69 results on '"Steven L. Parker"'
Search Results
2. Homoiterons and expansion in ribosomal RNAs
- Author
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Michael S. Parker, Floyd R. Sallee, Edwards A. Park, and Steven L. Parker
- Subjects
RNA expansion segment ,RNA nucleotide bias ,RNA nucleotide repeat ,Biology (General) ,QH301-705.5 - Abstract
Ribosomal RNAs in both prokaryotes and eukaryotes feature numerous repeats of three or more nucleotides with the same nucleobase (homoiterons). In prokaryotes these repeats are much more frequent in thermophile compared to mesophile or psychrophile species, and have similar frequency in both large RNAs. These features point to use of prokaryotic homoiterons in stabilization of both ribosomal subunits. The two large RNAs of eukaryotic cytoplasmic ribosomes have expanded to a different degree across the evolutionary ladder. The big RNA of the larger subunit (60S LSU) evolved expansion segments of up to 2400 nucleotides, and the smaller subunit (40S SSU) RNA acquired expansion segments of not more than 700 nucleotides. In the examined eukaryotes abundance of rRNA homoiterons generally follows size and nucleotide bias of the expansion segments, and increases with GC content and especially with phylogenetic rank. Both the nucleotide bias and frequency of homoiterons are much larger in metazoan and angiosperm LSU compared to the respective SSU RNAs. This is especially pronounced in the tetrapod vertebrates and seems to culminate in the hominid mammals. The stability of secondary structure in polyribonucleotides would significantly connect to GC content, and should also relate to G and C homoiteron content. RNA modeling points to considerable presence of homoiteron‐rich double‐stranded segments especially in vertebrate LSU RNAs, and homoiterons with four or more nucleotides in the vertebrate and angiosperm LSU RNAs are largely confined to the expansion segments. These features could mainly relate to protein export function and attachment of LSU to endoplasmic reticulum and other subcellular networks.
- Published
- 2015
- Full Text
- View/download PDF
3. Dimers of G-Protein Coupled Receptors as Versatile Storage and Response Units
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Michael S. Parker, Renu Sah, Ambikaipakan Balasubramaniam, Edwards A. Park, Floyd R. Sallee, and Steven L. Parker
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heteropentamer ,G-protein heterotrimer ,heterodimer ,homodimer ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
The status and use of transmembrane, extracellular and intracellular domains in oligomerization of heptahelical G-protein coupled receptors (GPCRs) are reviewed and for transmembrane assemblies also supplemented by new experimental evidence. The transmembrane-linked GPCR oligomers typically have as the minimal unit an asymmetric ~180 kDa pentamer consisting of receptor homodimer or heterodimer and a G-protein αβγ subunit heterotrimer. With neuropeptide Y (NPY) receptors, this assembly is converted to ~90 kDa receptor monomer-Gα complex by receptor and Gα agonists, and dimers/heteropentamers are depleted by neutralization of Gαi subunits by pertussis toxin. Employing gradient centrifugation, quantification and other characterization of GPCR dimers at the level of physically isolated and identified heteropentamers is feasible with labeled agonists that do not dissociate upon solubilization. This is demonstrated with three neuropeptide Y (NPY) receptors and could apply to many receptors that use large peptidic agonists.
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- 2014
- Full Text
- View/download PDF
4. Fragmentation and Matching of Human MicroRNA Sequences in 3’utr
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Ambikaipakan Balasubramaniam, Michael S. Parker, Steven L. Parker, and Floyd R. Sallee
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Base Composition ,Phylogenetic tree ,Three prime untranslated region ,Point mutation ,Computational Biology ,RNA ,General Medicine ,Biology ,MicroRNAs ,Evolutionary biology ,Transcription (biology) ,microRNA ,Sense (molecular biology) ,Emergency Medicine ,Humans ,Orthopedics and Sports Medicine ,RNA, Messenger ,3' Untranslated Regions ,Gene - Abstract
Aims: Definition of sense and antisense microRNA matches in 3’utr. Background: Matches of mature microRNAs (m-miRs) in human 3’utr could be traced to mutations producing fragments of original m-miR sequences without physical separation. (The m-miR matches in 5’utr and cds should be by far fewer, but could follow similar patterns). Objective: To ascertain if the sense and antisense m-miR fragments in 3’utr occur at similar or different levels. Methods: Frequency of sense and antisense m-miR matches in 3'utr was examined in the range of 7-22 nucleotides. Results: The fragmentation occurs at gene level by mutation within one of the paired m-miRs, which upon transcription results in increased interactive capability for both former pre-micro (premir) RNA stem partners. The non-mutated stem partner can persist in 3’utr sequences, as is apparent from significant presence of miR-619-5p and miR-5096 and some conservation of 20 other simian- specific m-miR sequences. However, most of m-mir sequences in 3’utr are extensively fragmented, with low preservation of long matches. In flanks of individual m-miR embeds the mutated pre-mir positions are to a degree defined specifically. Conclusion: The m-mir matches of various sizes in 3’utr apparently reflect accumulation, on a phylogenetic time scale, of in-sequence point mutations. Across human 3’utr this fragmentation is significantly less for evolutionarily recent human m-miRs that originate in simians compared to human m-miRs first appearing in lower primates, and especially to human m-miRs introduced in nonprimates.
- Published
- 2021
5. Medical Evaluation of Human MicroRNAs Needs to Address Recent Sequences and GC Content
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Steven L. Parker, Edwards A. Park, Floyd R. Sallee, and Michael S. Parker
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Developmental Neuroscience ,business.industry ,microRNA ,Medicine ,Medical evaluation ,Cell Biology ,Bioinformatics ,business ,GC-content ,Developmental Biology - Published
- 2017
6. G and C Iterons and Strings in MicroRNAs Should be Important in Regulation of mRNAs†
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Floyd R. Sallee, Steven L. Parker, Edwards A. Park, and Michael S. Parker
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Genetics ,chemistry.chemical_classification ,RNA ,General Medicine ,Iteron ,Biology ,Bioinformatics ,chemistry.chemical_compound ,chemistry ,Polynucleotide ,microRNA ,Emergency Medicine ,Orthopedics and Sports Medicine ,Nucleotide ,DNA - Abstract
Background: Same-nucleotide repeats (iterons) are strongly expressed in many DNA regions and RNA classes. These repeats serve importantly in association of polynucleotides and proteins, but have not been characterized in miRNAs. Methods: Iterons and nucleotide strings were quantified in currently known human miRNAs, including some comparisons with miRNAs of other species. Results: Human 5p miRNAs have significantly more G iterons than other miRNA groups. The 3p miRNAs have an inverse excess of C iterons. The miRNAs lacking functional counter-stems (which we differentiate as 5n or 3n by position in pre-miRNAs) also have a large excess of G iterons. In 5p miRNAs G and C iterons have much higher density in the seed compared to the post-seed region. This difference is lower in 5n and 3n sequences, and much lower in 3p sequences. In all groups the contiguous GC strings constitute a larger part of sequences than the AU strings. A surplus of G or C iterons and of GC strings should enable a more stable association with the target mRNAs. Conclusion: From the available evidence, the G iteron- and GC-rich miRNAs should also interact more readily with miRNA-processing and similar proteins.
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- 2016
7. The Expansion Segments of 28S Ribosomal RNA Extensively Match Human Messenger RNAs
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Steven L. Parker, Ambikaipakan Balasubramaniam, Floyd R. Sallee, and Michael S. Parker
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0301 basic medicine ,RNA nucleotide repeat ,lcsh:QH426-470 ,Biology ,18S ribosomal RNA ,03 medical and health sciences ,Ribosomal protein ,28S ribosomal RNA ,Genetics ,RNA expansion segment ,Genetics (clinical) ,Original Research ,GC content ,Messenger RNA ,030102 biochemistry & molecular biology ,RNA ,RNA nucleotide bias ,Ribosomal RNA ,biology.organism_classification ,rRNA/mRNA matches ,lcsh:Genetics ,030104 developmental biology ,Molecular Medicine ,Eukaryote ,GC-content - Abstract
Eukaryote ribosomal RNAs (rRNAs) have expanded in the course of phylogeny by addition of nucleotides in specific insertion areas, the expansion segments. These number about 40 in the larger (25–28S) rRNA (up to 2,400 nucleotides), and about 12 in the smaller (18S) rRNA (
- Published
- 2018
8. Homoiterons and expansion in ribosomal RNAs
- Author
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Steven L. Parker, Edwards A. Park, Floyd R. Sallee, and Michael S. Parker
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RNA nucleotide repeat ,QH301-705.5 ,ES, an expansion segment ,Biology ,Ribosome ,General Biochemistry, Genetics and Molecular Biology ,nt, nucleotides ,03 medical and health sciences ,0302 clinical medicine ,Research article ,Eukaryotic Small Ribosomal Subunit ,aa, amino acid residues ,Small nucleolar RNA ,Biology (General) ,u, nucleotide unit ,RNA expansion segment ,030304 developmental biology ,Genetics ,0303 health sciences ,ncRNA, non-coding RNA ,Eukaryotic Large Ribosomal Subunit ,LSU, large cytoplasmic ribosome subunit (50S in prokaryotes and archaea, 60S in eukaryotes) ,PCN, homoionic motifs with ⩾3% and ⩾50% ionic residues, found especially in Polynucleotide-binding proteins, Carrier proteins and Nuclear localization signals ,SSU, small cytoplasmic ribosome subunit (30S in prokaryotes and archaea, 40S in eukaryotes) ,RNA ,XN or NX, [X = a number] a nucleotide unit with same nucleobases (homoiteron), such as 4U or U4 for UUUU ,RNA nucleotide bias ,Ribosomal RNA ,Non-coding RNA ,mRNP, messenger ribonucleoprotein ,030217 neurology & neurosurgery ,GC-content - Abstract
Highlights • Homoiterons like GGGGGGG stabilize ribosomal RNAs of thermophile prokaryotes. • In eukaryotes, homoiterons are much more abundant in RNA of the larger subunit (LSU). • The LSU repeats increase with phylogenetic rank to 28% entire RNA sequence in hominids. • In mammal LSU RNAs, these repeats constitute 45% of the massive expansion segments. • These repeats may help in anchoring of ribosomes and export of secretory proteins., Ribosomal RNAs in both prokaryotes and eukaryotes feature numerous repeats of three or more nucleotides with the same nucleobase (homoiterons). In prokaryotes these repeats are much more frequent in thermophile compared to mesophile or psychrophile species, and have similar frequency in both large RNAs. These features point to use of prokaryotic homoiterons in stabilization of both ribosomal subunits. The two large RNAs of eukaryotic cytoplasmic ribosomes have expanded to a different degree across the evolutionary ladder. The big RNA of the larger subunit (60S LSU) evolved expansion segments of up to 2400 nucleotides, and the smaller subunit (40S SSU) RNA acquired expansion segments of not more than 700 nucleotides. In the examined eukaryotes abundance of rRNA homoiterons generally follows size and nucleotide bias of the expansion segments, and increases with GC content and especially with phylogenetic rank. Both the nucleotide bias and frequency of homoiterons are much larger in metazoan and angiosperm LSU compared to the respective SSU RNAs. This is especially pronounced in the tetrapod vertebrates and seems to culminate in the hominid mammals. The stability of secondary structure in polyribonucleotides would significantly connect to GC content, and should also relate to G and C homoiteron content. RNA modeling points to considerable presence of homoiteron-rich double-stranded segments especially in vertebrate LSU RNAs, and homoiterons with four or more nucleotides in the vertebrate and angiosperm LSU RNAs are largely confined to the expansion segments. These features could mainly relate to protein export function and attachment of LSU to endoplasmic reticulum and other subcellular networks.
- Published
- 2015
9. Canonical microRNA Matching Differs Greatly Across Groups of G-protein Coupled Receptor mRNAs
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Ambikaipakan Balasubramaniam, Steven L. Parker, Floyd R. Sallee, and Michael S. Parker
- Subjects
Untranslated region ,Frizzled ,Olfactory receptor ,G protein ,Gene Expression Profiling ,General Medicine ,Biology ,Sensory receptor ,Molecular biology ,Cell biology ,Receptors, G-Protein-Coupled ,MicroRNAs ,medicine.anatomical_structure ,microRNA ,Emergency Medicine ,medicine ,Humans ,Orthopedics and Sports Medicine ,RNA, Messenger ,Receptor ,G protein-coupled receptor - Abstract
BACKGROUND Heptahelical G protein coupled receptors (GPCRs) support numerous sensory and metabolic functions and differ considerably in levels of expression. GPCR protein levels should link to regulation of GPCR mRNAs by microRNAs (miRs), which might significantly depend on numbers, size and GC content of the canonical antisense matches in mRNAs. These parameters of GPCR mRNAs have not been studied in detail. METHODS Canonical matching profiles of human GPCR mRNAs and miRs were examined using segments of 7-15 nucleotides in windows shifted by one position over the entire microRNA sequence. RESULTS Human GPCRs mRNAs within larger function-related groups have a quite homogenous matching with miRs. Both the GC content and the melting temperature (and hence also the binding energy) are appreciably higher in 5'utr compared to 3'utr matches of the same length. Increase in the GC content correlates significantly with length in the ubiquitous matches of 7-12 nucleotides. However, several GPCR groups strongly differ in overall match numbers and density. The untranslated regions of sensory receptor mRNAs, especially the olfactory and Taste-2 mRNAs, have the lowest match numbers and density and the fewest miR partners. The glucagon and frizzled families show the highest canonical matching. CONCLUSION Partnership of GPCR mRNAs and miRs could significantly relate to the type of function of the receptor proteins, with mRNAs of the sensory receptors having the lowest and those of metabotropic GPCRs the highest targeting. This could be of interest regarding GPCR regulation by exogenous miRs.
- Published
- 2017
10. Canonical Matches of Human MicroRNAs with mRNAs: A Broad Matrix of Position and Size
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Floyd R. Sallee, Steven L. Parker, Edwards A. Park, and Michael S. Parker
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Messenger RNA ,Base Composition ,Base Sequence ,Hydrogen Bonding ,General Medicine ,Computational biology ,Biology ,Matrix (biology) ,Bioinformatics ,MicroRNAs ,Drosophila melanogaster ,Mrna regulation ,Sequence Homology, Nucleic Acid ,microRNA ,Databases, Genetic ,Emergency Medicine ,Animals ,Humans ,Orthopedics and Sports Medicine ,RNA, Messenger ,5' Untranslated Regions ,3' Untranslated Regions ,GC-content - Abstract
Background: Canonical hydrogen-bonding multi-nucleotide matches of microRNAs (miRs) with mRNAs are considered as important in mRNA regulation. MiR "seed" positions 2-8 are frequently viewed as mRNA partners, but there is ample evidence for use of other (and even non-contiguous) miR parts. No detailed information is available about canonical matching, and the GC content of the matches is rarely considered, although it should have a major regulatory potential. Methods: Sequences of 2586 human miRs and of 5'utr, cds and 3'utr in 18810 human mRNAs were examined for number and GC content of contiguous Watson-Crick antisense matches of six or more nucleotides (nt) in successive windows shifted by 1 nt. Results: Frequency of the antisense matches is within all sectors similar for segments of up to 10 nt starting at positions 1-10 of miR sequences, with decrease of 3.5 to 4-fold for each 1-nt increment. Adenine and uracil rich elements (ARE-like) are very frequent in cds and 3'utr. All mRNAs have matches of up to 10 nt, and most also those of 11-15 nt. The match density is largest in 5'utr, and the match number in cds. The 5'utr and cds matches average much higher GC content than those of 3'utr. The GC content of matches is above that for the whole sector in 5'utr and cds, but lower in 3'utr. Conclusion: Human mRNA matches across miR sequences constitute a positionally similar matrix of canonical hydrogen-bonding reactivity. This presents ample opportunities for contiguous binding independent of miR position. The ubiquitous 10 to 15-nt matches could serve as binding foci. Interaction of miRs with the abundant GC-rich 5'utr and cds counterparts could be important in the regulation of mRNA-ribosome interaction as well as in mRNA disposal. The lower density and GC content of a majority of 3'utr matches could mainly support a dynamic regulation by miRs.
- Published
- 2016
11. On the segregation of protein ionic residues by charge type
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Michael S. Parker, Ambikaipakan Balasubramaniam, and Steven L. Parker
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Ions ,Chemistry ,Organic Chemistry ,Clinical Biochemistry ,Antimicrobial peptides ,Proteins ,Ionic bonding ,Sequence (biology) ,Charge type ,Proteomics ,Biochemistry ,Polynucleotide ,Proteins metabolism ,Protein biosynthesis ,Biophysics ,Humans - Abstract
Based on ubiquitous presence of large ionic motifs and clusters in proteins involved in gene transcription and protein synthesis, we analyzed the distribution of ionizable sidechains in a broad selection of proteins with regulatory, metabolic, structural and adhesive functions, in agonist, antagonist, toxin and antimicrobial peptides, and in self-excising inteins and intron-derived proteins and sequence constructs. All tested groups, regardless of taxa or sequence size, show considerable segregation of ionizable sidechains into same type charge (homoionic) tracts. These segments in most cases exceed half of the sequence length and comprise more than two-thirds of all ionizable sidechains. This distribution of ionic residues apparently reflects a fundamental advantage of sorted electrostatic contacts in association of sequence elements within and between polypeptides, as well as in interaction with polynucleotides. While large ionic densities are encountered in highly interactive proteins, the average ionic density in most sets does not change appreciably with size of the homoionic segments, which supports the segregation as a modular feature favoring association.
- Published
- 2012
12. Non-specific binding and general cross-reactivity of Y receptor agonists are correlated and should importantly depend on their acidic sectors
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O. Zerbe, Floyd R. Sallee, Ambikaipakan Balasubramaniam, Renu Sah, Michael S. Parker, and Steven L. Parker
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Physiology ,Peptide Hormones ,Amino Acid Motifs ,Sus scrofa ,Peptide ,Plasma protein binding ,Biochemistry ,Protein Structure, Secondary ,Mice ,Endocrinology ,Protein structure ,Cricetinae ,Urea ,Neuropeptide Y ,Receptor ,Cerebral Cortex ,chemistry.chemical_classification ,Perchlorates ,Chemistry ,Neuropeptide Y receptor ,Sodium Compounds ,Protein Binding ,Agonist ,medicine.drug_class ,Stereochemistry ,Detergents ,Molecular Sequence Data ,CHO Cells ,Pancreatic Polypeptide ,Transfection ,Article ,Gastrointestinal Hormones ,Cellular and Molecular Neuroscience ,Cricetulus ,medicine ,Animals ,Humans ,Peptide YY ,Amino Acid Sequence ,Binding site ,Binding Sites ,Cell Membrane ,Neuropeptides ,Peptide Fragments ,Rats ,Receptors, Neuropeptide Y ,HEK293 Cells ,Ultracentrifugation - Abstract
Non-specific binding of Y receptor agonists to intact CHO cells, and to CHO cell or rat brain particulates, is much greater for human neuropeptide Y (hNPY) compared to porcine peptide Y (pPYY), and especially relative to human pancreatic polypeptide (hPP). This binding of hNPY is reduced by alkali cations in preference to non-ionic chaotrope urea, while the much lower non-specific binding of pPYY is more sensitive to urea. The difference could mainly be due to the 10-16 stretch in 36-residue Y agonists (residues 8-14 in N-terminally clipped 34-peptides), located in the sector that contains all acidic residues of physiological Y agonists. Anionic pairs containing aspartate in the 10-16 zone could be principally responsible for non-specific attachments, but may also aid the receptor site binding. Two such pairs are found in hNPY, one in pPYY, and none in hPP. The hydroxyl amino acid residue at position 13 in mammalian PYY and PP molecules could lower conformational plasticity and the non-selective binding via intrachain hydrogen bonding. The acidity of this tract could also be important in agonist selectivity of the Y receptor subtypes. The differences point to an evolutionary reduction of promiscuous protein binding from NPY to PP, and should also be important for Y agonist selectivity within NPY receptor group, and correlate with partial agonism and out-of group cross-reactivity with other receptors.
- Published
- 2011
13. The fourth intracellular domain of G-protein coupling receptors: helicity, basicity and similarity to opsins
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Michael S. Parker and Steven L. Parker
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Opsin ,Opsins ,Sequence Homology, Amino Acid ,genetic structures ,biology ,G protein ,Bilayer ,Molecular Sequence Data ,Organic Chemistry ,Clinical Biochemistry ,Biochemistry ,Helicity ,Protein Structure, Secondary ,Protein Structure, Tertiary ,Receptors, G-Protein-Coupled ,Coupling (electronics) ,Rhodopsin ,Biophysics ,biology.protein ,Animals ,Humans ,Cattle ,Receptor ,G protein-coupled receptor - Abstract
The minimal size of the fourth intracellular domain of heptahelical G-protein coupling receptors (GPCRs) is close to 15 residues, and a juxtamembrane 15-residue segment is predicted as helical (Helix-8) in most of the receptors. Sequences of opsins, non-visual opsin-like (family A) GPCRs and Taste-2 receptors correspond with bovine rhodopsin at four positions in this tract. This is especially evident in monoamine receptors. In most GPCRs, the conserved juxtamembrane segment also has a large fraction of basic sidechains, and a considerable excess of cationic over anionic residues. The conservation is not dependent on the preferred G-protein alpha subunit or the overall length of the domain, indicating an additive speciation. In rod opsins and some A-GPCRs this segment has been shown to associate with the bilayer and to interact with G-proteins. The segment could also be involved in precoupling of receptors and transducers. These interactions could be helped by both the structural propensities and the high content of cationic sidechains.
- Published
- 2009
14. Oligomerization of the Heptahelical G Protein Coupling Receptors: A Case for Association Using Transmembrane Helices (Supplimentry Material)
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Trevor W. Sweatman, Ambikaipakan Balasubramaniam, Michael S. Parker, Edwards A. Park, Floyd R. Sallee, Renu Sah, and Steven L. Parker
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Pharmacology ,Coupling (electronics) ,Transmembrane domain ,G protein ,Heterotrimeric G protein ,Drug Discovery ,General Medicine ,Biology ,Signal transduction ,Receptor ,Intracellular ,G protein-coupled receptor ,Cell biology - Abstract
The heptahelical G protein coupling receptors oligomerize extensively via transmembrane domains, in association with heterotrimeric G proteins. This provides higher affinity for agonists, conformational stability necessary for signal transduction, and protection from intracellular proteinases. The oligomerization is relevant to organismic pathophysiology and could be targeted by natural or modified agonists. For Supplement material, please see the online version of the article.
- Published
- 2009
15. Importance of a N-terminal aspartate in the internalization of the neuropeptide Y Y2 receptor
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Floyd R. Sallee, Ying Y. Wong, Steven L. Parker, Renu Sah, Michael S. Parker, and Ambikaipakan Balasubramaniam
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Neuropeptide Y receptor Y1 ,Neuropeptide Y receptor Y2 ,Molecular Sequence Data ,Neuropeptide FF receptor ,CHO Cells ,Biology ,Article ,Estrogen-related receptor alpha ,Cricetulus ,GTP-Binding Proteins ,Cricetinae ,Enzyme-linked receptor ,Animals ,Humans ,5-HT5A receptor ,Amino Acid Sequence ,DNA Primers ,Pharmacology ,Aspartic Acid ,Binding Sites ,Neuropeptide Y receptor ,Molecular biology ,Receptors, Neuropeptide Y ,Kinetics ,Interleukin-21 receptor ,Mutation ,Protein Binding - Abstract
With human neuropeptide Y Y2 receptor expressed in the Chinese hamster ovary (CHO) cells, the Asp35Ala mutation, and especially the change of Pro34Asp35 to Ala34Ala35, decrease the compartmentalization and strongly accelerate internalization of the receptor. These changes are not associated with alterations in agonist affinity, G-protein interaction, dimerization, or level of expression of the mutated receptors relative to the wildtype receptor. The proline-flanked aspartate in the N-terminal extracellular segment of the neuropeptide Y Y2 receptor thus apparently has a large role in anchoring and compartmentalization of the receptor. However, the Pro34Ala mutation does not significantly affect the embedding and cycling of the receptor.
- Published
- 2008
16. Neuropeptide Y (NPY) Y2 receptors of rabbit kidney cortex are largely dimeric
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Floyd R. Sallee, Michael S. Parker, A. M. Estes, Steven L. Parker, Y. Y. Wong, and Ambikaipakan Balasubramaniam
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Male ,Agonist ,medicine.medical_specialty ,Kidney Cortex ,Physiology ,medicine.drug_class ,G protein ,Protein subunit ,Clinical Biochemistry ,CHO Cells ,GTP-Binding Protein alpha Subunits, Gi-Go ,Biology ,Biochemistry ,Cellular and Molecular Neuroscience ,Cricetulus ,Endocrinology ,GTP-Binding Proteins ,Cricetinae ,Internal medicine ,medicine ,Animals ,Pancreatic polypeptide ,Receptor ,G protein-coupled receptor ,Chinese hamster ovary cell ,Neuropeptide Y receptor ,Receptors, Neuropeptide Y ,Solubility ,Rabbits ,Dimerization ,Protein Binding - Abstract
The neuropeptide Y (NPY) Y2 receptors and the pancreatic polypeptide Y4 receptors from rabbit kidney cortex are isolated largely as approximately 180 kDa complexes constituted of one receptor dimer and one G-protein heterotrimer, similar to NPY receptors expressed in the Chinese hamster ovary (CHO) cells. As expected, kidney and CHO cell Y2 dimers are converted into monomers by increasing concentrations of a selective agonist. Prevalence of dimeric Y2 receptors in the kidney could be related to low plasma levels of Y2 agonists, and possibly also to a relatively low concentration of Gi alpha subunits.
- Published
- 2008
17. Neuropeptide Y Y2 receptor in health and disease
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Steven L. Parker and Ambikaipakan Balasubramaniam
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Pharmacology ,Mechanism of action ,Angiogenesis ,medicine ,Disease ,medicine.symptom ,Compartmentalization (psychology) ,Biology ,Endocytosis ,Neuropeptide Y receptor ,Receptor ,Neuroscience ,Pathological - Abstract
We briefly survey the current knowledge and concepts regarding structure and function of the neuropeptide Y Y2 receptor and its agonists, especially as related to pharmacology of the receptor and its roles in pathological processes. Specific structural features are considered that could be responsible for the known compartmentalization and participation of the receptor in cell and tissue organization. This is further discussed in relation to changes of levels of the Y2 receptor in pathological conditions (especially in epilepsy and drug abuse), to endocytosis and recycling, and to participation in wound healing, retinopathy and angiogenesis. Properties of the receptor and of Y2 agonists are considered and reviewed in connection to the negative regulation of transmitter release, feeding, mood and social behavior. The possible involvement of the Y2 receptor in diabetes, carcinogenesis and bone formation is also reviewed.
- Published
- 2008
18. Pertussis toxin induces parallel loss of neuropeptide Y Y1 receptor dimers and Gi α subunit function in CHO cells
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Michael S. Parker, Ambikaipakan Balasubramaniam, Renu Sah, Floyd R. Sallee, and Steven L. Parker
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Agonist ,Swine ,medicine.drug_class ,media_common.quotation_subject ,CHO Cells ,GTP-Binding Protein alpha Subunits, Gi-Go ,Biology ,Pertussis toxin ,Cricetulus ,Cricetinae ,Heterotrimeric G protein ,medicine ,Animals ,Humans ,Internalization ,Receptor ,media_common ,G protein-coupled receptor ,Pharmacology ,Colforsin ,Neuropeptide Y receptor ,Rats ,Receptors, Neuropeptide Y ,Cell biology ,Pertussis Toxin ,Biochemistry ,Guanosine 5'-O-(3-Thiotriphosphate) ,G12/G13 alpha subunits ,GTP-Binding Protein alpha Subunits, Gq-G11 ,Adenylyl Cyclases - Abstract
Treatment with pertussis toxin in addition to a stable inhibition of G(i)alpha subunits of G-proteins also strongly reduced human neuropeptide Y Y(1) receptors expressed in Chinese hamster ovary (CHO) cells. This was reflected in abolition of the inhibition by Y(1) agonists of forskolin-stimulated adenylyl cyclase in intact cells, and of Y(1) agonist stimulation of GTPgammaS binding to particulates from disrupted cells. The loss of both receptor and G(i)alpha subunit function was attenuated by ammonium chloride, an inhibitor of acid proteinases, pointing to a chaperoning co-protection of active pertussis toxin-sensitive Galpha subunits and Y(1) receptors. The surface complement of the Y(1) receptor was changed a little in conditions of approximately 85% decrease of the Y(1) population, but the rate of the Y(1) receptor-linked internalization of agonist peptides was reduced about 70%. The preserved receptor fraction consisted of monomers significantly coupled to G(q)alpha subunits. The persistent pertussis toxin-insensitive internalization of agonists with the Y(1) receptor may reflect a rescue or alternative switching that could be important for cell functioning in neuropeptide Y-rich environments. The results are compatible with a loss, due to G(i)alpha subunit inactivation by the toxin, of a large Y(1) receptor reserve constituted of oligomers associating with heterotrimeric G-proteins.
- Published
- 2008
19. Interaction of NPY compounds with the rat glucocorticoid-induced receptor (GIR) reveals similarity to the NPY–Y2 receptor
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Katherine Eaton, Renu Sah, Floyd R. Sallee, Steven L. Parker, Sulaiman Sheriff, and Ambikaipakan Balasubramaniam
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Agonist ,medicine.medical_specialty ,Physiology ,medicine.drug_class ,Molecular Sequence Data ,Biology ,Biochemistry ,Article ,Receptors, G-Protein-Coupled ,Cellular and Molecular Neuroscience ,Endocrinology ,Glucocorticoid receptor ,Internal medicine ,Chlorocebus aethiops ,mental disorders ,Radioligand ,medicine ,Animals ,Neuropeptide Y ,Amino Acid Sequence ,Receptor ,DNA Primers ,COS cells ,Base Sequence ,Sequence Homology, Amino Acid ,Antagonist ,Neuropeptide Y receptor ,humanities ,Rats ,Receptors, Neuropeptide Y ,COS Cells ,Glucocorticoid ,medicine.drug - Abstract
The rat glucocorticoid-induced receptor (rGIR) is an orphan G protein-coupled receptor awaiting pharmacological characterization. Among known receptors, rGIR exhibits highest sequence similarity to the neuropeptide Y (NPY)-Y(2) receptor (38-40%). The pharmacological profile of rGIR was investigated using (125)I-PYY(3-36), a Y(2)-preferring radioligand and several NPY analogs. rGIR displayed a similar displacement profile as reported for the Y(2) receptor, in that the Y(2)-selective C terminus fragments of NPY and PYY (NPY(3-36) and PYY(3-36)) showed high affinity binding and activation of rGIR (low nanomolar range). The rank order potency for displacement was NPY(3-36)>PYY(3-36)=NPY>NPY(13-36)>Ac, Leu NPY(24-36)>[D-Trp(32)]-NPY>Leu(31), Pro(34)-NPY=hPP. NPY and Y(2)-selective agonists NPY(3-36) and PYY(3-36) led to significant activation of (35)S-GTPgammaS binding to rGIR transfected cells. BIIE0246, a specific Y(2) antagonist, displaced (125)I-PYY(3-36) binding to rGIR with high affinity (95nM). Activation of (35)S-GTPgammaS binding by Y(2)-selective agonist in rGIR transfected cells was also completely abolished by BIIE0246. Our data report, for the first time, an interaction of NPY ligands with rGIR expressed in vitro, and indicate similarities between GIR and the NPY-Y(2) receptor.
- Published
- 2007
20. G and C Iterons and Strings in MicroRNAs Should be Important in Regulation of mRNAs(†)
- Author
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Michael S, Parker, Edwards A, Park, Floyd R, Sallee, and Steven L, Parker
- Subjects
MicroRNAs ,Base Sequence ,Humans ,RNA Processing, Post-Transcriptional ,5' Untranslated Regions ,3' Untranslated Regions - Abstract
Same-nucleotide repeats (iterons) are strongly expressed in many DNA regions and RNA classes. These repeats serve importantly in association of polynucleotides and proteins, but have not been characterized in miRNAs.Iterons and nucleotide strings were quantified in currently known human miRNAs, including some comparisons with miRNAs of other species.Human 5p miRNAs have significantly more G iterons than other miRNA groups. The 3p miRNAs have an inverse excess of C iterons. The miRNAs lacking functional counter-stems (which we differentiate as 5n or 3n by position in pre-miRNAs) also have a large excess of G iterons. In 5p miRNAs G and C iterons have much higher density in the seed compared to the post-seed region. This difference is lower in 5n and 3n sequences, and much lower in 3p sequences. In all groups the contiguous GC strings constitute a larger part of sequences than the AU strings. A surplus of G or C iterons and of GC strings should enable a more stable association with the target mRNAs.From the available evidence, the G iteron- and GC-rich miRNAs should also interact more readily with miRNA-processing and similar proteins.
- Published
- 2015
21. Neuropeptide Y as a partial agonist of the Y1 receptor
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Floyd R. Sallee, Ambikaipakan Balasubramaniam, Renu Sah, Michael S. Parker, and Steven L. Parker
- Subjects
Male ,Agonist ,medicine.medical_specialty ,Neuropeptide Y receptor Y1 ,Neuropeptide Y receptor Y2 ,medicine.drug_class ,Neuropeptide ,Neuropeptide FF receptor ,CHO Cells ,Biology ,Binding, Competitive ,Rats, Sprague-Dawley ,Cricetulus ,Cricetinae ,Internal medicine ,medicine ,Animals ,Humans ,Neuropeptide Y ,Peptide YY ,Receptor ,Pharmacology ,Colforsin ,Neuropeptide Y receptor ,Rats ,Receptors, Neuropeptide Y ,Endocrinology ,Adenylyl Cyclases ,Signal Transduction ,Synaptosomes - Abstract
In absence of receptor cycling, human/rat neuropeptide Y was found to persistently occupy the guinea pig neuropeptide Y Y1 receptors expressed on the surface of Chinese hamster ovary (CHO) cells (IC 50 ∼ 8 nM); a lasting occupancy was also evident with active receptor cycling. A similar blockade was obtained with the human neuropeptide Y Y1 receptor (in CHO or SK-N-MC cells). Peptidic antagonists GR238118 (1229U91) and VD-11 blocked the Y1 receptor in the same molarity range. A neuropeptide Y-related Y1 agonist, (Leu 31 Pro 34 ) human neuropeptide Y, also strongly adhered to the Y1 site. Similar blockade-like occupancy by neuropeptide Y was found with particulates from Y1-expressing CHO cells, and with native neuropeptide Y Y1 receptors of rat synaptosomes. Peptide YY and a related Y1-selective agonist, (Leu 31 Pro 34 ) human peptide YY, showed a much less stable binding to the neuropeptide Y Y1 receptor with either the intact cells or particulates. The Y1 binding of neuropeptide Y was also less sensitive to chaotropic agents and guanine nucleotides than the binding of peptide YY, indicating a larger stability for association of neuropeptide Y with the receptor. Inhibition of forskolin-stimulated adenylyl cyclase showed a distinctly attenuating agonism for neuropeptide Y, with an activity similar to peptide YY below 1 nM, but considerably lower above 3 nM of the peptides. This activity was largely exerted via pertussis toxin-sensitive G-proteins of Y1-CHO cells. Our findings indicate that signaling by neuropeptide Y via its Y1 receptor could be self-restricting at higher levels of the peptide, in relation to a strong association of the agonist with the Y1 binding site.
- Published
- 2005
22. Gestational nicotine exposure reduces nicotinic cholinergic receptor (nAChR) expression in dopaminergic brain regions of adolescent rats
- Author
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Shannon G. Matta, Steven L. Parker, Burt M. Sharp, and Hao Chen
- Subjects
medicine.medical_specialty ,business.industry ,General Neuroscience ,Dopaminergic ,Substantia nigra ,Nucleus accumbens ,Ventral tegmental area ,Nicotine ,medicine.anatomical_structure ,Endocrinology ,Nicotinic agonist ,nervous system ,Dopamine ,In utero ,Internal medicine ,Medicine ,business ,medicine.drug - Abstract
Children of women who smoked during pregnancy are at increased risk of dependence when smoking is initiated during adolescence. We previously reported that gestational nicotine exposure attenuated dopamine release induced by nicotine delivered during adolescence. In this study, we determined the effects of gestational nicotine exposure on nicotinic cholinergic receptor (nAChR) expression. Timed pregnant rats received nicotine (2 mg/kg/day) or vehicle via mini-osmotic pumps during gestation. Treatments continued in pups via maternal nursing during postnatal days (PN) 2-14 (equivalent to the human in utero third trimester). On PN35, 1 2 5 I-epibatidine binding to nAChR was measured. The B m a x values (fmol/mg) in prefrontal cortex (PFC), nucleus accumbens (NAcc), substantia nigra (SN) and ventral tegmental area (VTA) were reduced by 26.6% (P < 0.05), 32.6% (P < 0.01), 23.0% (P < 0.01) and 27.6% (P < 0.05), respectively. In addition, gender differences were found in vehicle-treated groups; in SN and VTA, females were 79.3% (P < 0.005) and 82.9% (P = 0.08) of males, respectively. The expression of nAChR subunit mRNAs was measured using real-time RT-PCR on laser-capture microdissected tissues. In adolescent VTA, gestational nicotine exposure reduced (P < 0.05) nAChR subunit mRNAs encoding a3 (53.0%), α4 (23.9%), a5 (46.7%) and β4 (61.4%). In NAcc core, the treatment increased α3 mRNA (75.8%). In addition, the number of neurons in VTA was reduced by 15.0% (P< 0.001). These studies indicate that gestational exposure to nicotine induces long-lasting changes in nAChR expression that may underlie the vulnerability of adolescents to dependence on nicotine.
- Published
- 2005
23. Internalization of neuropeptide Y Y1 and Y5 and of pancreatic polypeptide Y4 receptors is inhibited by lithium in preference to sodium and potassium ions
- Author
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Steven L. Parker, Justin K. Kane, and Michael S. Parker
- Subjects
Receptor recycling ,Agonist ,Physiology ,medicine.drug_class ,media_common.quotation_subject ,Guinea Pigs ,Clinical Biochemistry ,CHO Cells ,Lithium ,Ligands ,Pancreatic Polypeptide ,Binding, Competitive ,Biochemistry ,Cellular and Molecular Neuroscience ,Endocrinology ,Cricetinae ,medicine ,Animals ,Humans ,Pancreatic polypeptide ,Neuropeptide Y ,Receptor ,Internalization ,media_common ,Ligand ,Chemistry ,Chinese hamster ovary cell ,Sodium ,Neuropeptide Y receptor ,Receptors, Neuropeptide Y ,Potassium ,Biophysics - Abstract
The receptor-linked internalization of [125I] human neuropeptide Y (NPY) in Chinese hamster ovary (CHO) cells expressing the guinea-pig Y1 receptors or in human endometrial carcinoma-1B (Hec-1B) cells expressing the human Y5 receptor, as well as the receptor-linked internalization of human pancreatic polypeptide (hPP) receptor expressed in CHO cells, is selectively inhibited by low molarities of the Li+ cation. The Na+ and K+ cations decreased the receptor-linked internalization of agonist peptides only at high molar inputs, and largely in proportion to the reduction of cell surface binding of Y ligand peptides, dependent on ion concentration and the type of Y receptor examined. With particulates isolated from disrupted cells, there was no preferential inhibition by Li+ relative to Na+ in the binding of type-specific ligand peptides to Y receptors of any type. The observed difference could be connected to the known ability of Li+ to modify active conformations of signal transducers, which may also directly or indirectly affect the internalization motors. The decrease in the rate of Y receptor internalization by Li+ also points to a possible alteration of Y receptor signaling in vivo by lithium at acute therapeutically employed dose levels.
- Published
- 2004
24. Up-Regulation of Brain Nicotinic Acetylcholine Receptors in the Rat during Long-Term Self-Administration of Nicotine: Disproportionate Increase of the α6 Subunit
- Author
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Jon Lindstrom, J. Michael McIntosh, Jianhong Luo, Kathleen McAllen, Burt M. Sharp, Steven L. Parker, and Yitong Fu
- Subjects
Male ,Nicotine ,medicine.medical_specialty ,Pyridines ,Self Administration ,Receptors, Nicotinic ,Sodium Chloride ,Nucleus accumbens ,Antibodies ,Time ,Mice ,Prosencephalon ,Internal medicine ,medicine ,Tegmentum ,Animals ,Nicotinic Agonists ,Immunosorbent Techniques ,Acetylcholine receptor ,Pharmacology ,Binding Sites ,urogenital system ,Chemistry ,Putamen ,Brain ,Anatomy ,Bridged Bicyclo Compounds, Heterocyclic ,Rats ,Up-Regulation ,Protein Subunits ,Nicotinic agonist ,Endocrinology ,nervous system ,Mice, Inbred DBA ,Rats, Inbred Lew ,Cerebellar cortex ,Epibatidine ,Molecular Medicine ,Conotoxins ,medicine.drug - Abstract
In male rats continually self-administering nicotine (approximately 1.5 mg free base/kg/day), we found a significant increase of nicotinic acetylcholine receptors (nAChRs) labeled by epibatidine (Epb) in 11 brain areas. A large increase of high-affinity Epb binding sites was apparent in the ventral tegmentum/substantia nigra, nucleus tractus solitarii, nucleus accumbens, thalamus/subthalamus, parietal cortex, hypothalamus, and amygdala. A smaller but significant up-regulation of high-affinity Epb sites was seen in the piriform cortex, hippocampus, caudate/putamen, and cerebellar cortex. The up-regulation of nAChRs, shown by immunoadsorption and Western blotting, involved alpha4, alpha6, and beta2 subunits. As a consequence of long-term self-administration of nicotine, the alpha6 immunoreactive (IR) binding of either labeled Epb or 125I-alpha-conotoxin MII increased to a much greater extent than did alpha4 or beta2 IR binding of Epb. In addition, the beta2 IR binding of Epb was consistently enhanced to a greater extent than was alpha4. These findings may reflect a larger surface membrane retention of alpha6-containing and, to some degree, beta2-containing nAChRs compared with alpha4-containing nAChRs during long-term self-administration of nicotine.
- Published
- 2004
25. Internalization of pancreatic polypeptide Y4 receptors: correlation of receptor intake and affinity
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Steven L. Parker, Michael S. Parker, and Ingrid Lundell
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Endosome ,media_common.quotation_subject ,education ,CHO Cells ,Clathrin ,Species Specificity ,Cricetinae ,medicine ,Animals ,Humans ,Pancreatic polypeptide ,Receptor ,Internalization ,Pancreas ,media_common ,Pharmacology ,biology ,Chinese hamster ovary cell ,Neuropeptide Y receptor ,Rats ,Receptors, Neuropeptide Y ,medicine.anatomical_structure ,Biochemistry ,biology.protein ,Peptides ,Protein Binding - Abstract
Unlike neuropeptide Y receptors, the pancreatic polypeptide Y4 receptors display considerable differences in sequence and ligand-binding affinity across mammalian species. This could produce different receptor turnover rates in the same cellular membrane environment. Comparing rat, human and guinea-pig Y4 receptors expressed in Chinese hamster ovary (CHO) cells (K(d) with human pancreatic polypeptide 14, 45 and 116 pM, respectively), we indeed found human pancreatic polypeptide internalization in the rank order of receptor affinities. A large fraction of the internalized human pancreatic polypeptide, similar across the Y4 species, was associated with secondary endosomes (density approximately 1.05 in Percoll gradients) and lysosomes (density approximately 1.11). For all Y4 receptors examined, this intake was potently and selectively inhibited by cholesterol-complexing polyene antibiotic filipin III and also by clathrin lattice formation inhibitor, phenylarsine oxide. Internalization differences found across Y4 receptor species to a degree compare with those observed for the cloned guinea-pig neuropeptide Y Y1 and human neuropeptide Y Y5 receptors and, generally, support ligand-binding affinities as important determinants of internalization for neuropeptide receptors.
- Published
- 2002
26. A pool of Y2 neuropeptide Y receptors activated by modifiers of membrane sulfhydryl or cholesterol balance
- Author
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Justin K. Kane, Steven L. Parker, Magnus M. Berglund, and Michael S. Parker
- Subjects
education.field_of_study ,Chinese hamster ovary cell ,Population ,Biology ,Neuropeptide Y receptor ,Biochemistry ,Cell membrane ,chemistry.chemical_compound ,medicine.anatomical_structure ,Membrane protein ,chemistry ,medicine ,Phenylarsine oxide ,Lipid bilayer ,education ,Receptor - Abstract
The cloned guinea-pig Y2 neuropeptide Y (NPY) receptors expressed in Chinese hamster ovary (CHO) cells, as well as the Y2 receptors natively expressed in rat forebrain, are distributed in two populations. A smaller population that is readily accessed by agonist peptides on the surface of intact cells constitutes less than 30% of Y2 receptors detected in particulates after cell homogenization. A much larger fraction of cell surface Y2 sites can be activated by sulfhydryl modifiers. A fast and large activation of these masked or cryptic sites could be obtained with membrane-permeating, vicinal cysteine-bridging arsenical phenylarsine oxide. A lower activation is effected by N-ethylmaleimide, an alkylator that slowly penetrates lipid bilayers. The restricted-access alkylator, 2-[(trimethylammonium)ethyl]methanethiosulfonate, was not effective in unmasking these sites. Some of the hidden cell surface Y2 sites could be activated by polyene filipin III through complexing of membrane cholesterol. The results are consistent with the presence of a large Y2 reserve in a compartment that can be accessed by alteration of sulfhydryl balance or fluidity of the cell membrane, and by treatments that affect the anchoring and aggregation of membrane proteins.
- Published
- 2002
27. Pancreatic polypeptide receptors: affinity, sodium sensitivity and stability of agonist binding 1 1Abbreviations: NPY, neuropeptide Y; hNPY, human NPY; PYY, peptide YY; pPYY, porcine PYY; LP-PYY, (Leu31,Pro34) human peptide YY; hPP, rPP, human and rat pancreatic polypeptide, respectively; hPYY [3–36], human peptide YY [3–36]; EIPA, 5-(N-ethyl, N-isopropyl)amiloride; DMA, 5-(N, N-dimethyl)amiloride; HEXA, 5-(N, N-hexamethylene)amiloride; MIA, 5-N(methyl, N-isobutyl)amiloride; CHO, Chinese hamster ovary; PEG, polyethylene glycol
- Author
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Michael S. Parker, Steven L. Parker, and Ingrid Lundell
- Subjects
Agonist ,Physiology ,Chemistry ,medicine.drug_class ,Chinese hamster ovary cell ,Pancreatic polypeptide receptors ,Biochemistry ,Dissociation (chemistry) ,Cellular and Molecular Neuroscience ,Endocrinology ,Biophysics ,medicine ,Pancreatic polypeptide ,Selectivity ,Receptor ,Antagonism - Abstract
Cloned rat, human and guinea-pig Y4 pancreatic polypeptide (PP) receptors expressed in Chinese hamster ovary (CHO) cells, as well as the rabbit Y4-like PP receptor, show a selective sensitivity to Na+ over K+ ion in PP attachment, but little sensitivity to Na+ in dissociation of bound PP peptides. Agonist binding to Y4 receptors of intact CHO cells also shows much greater sensitivity to Na+ over K+, and a tenacious attachment of the bound agonist. Binding sensitivity to K+ is greatly enhanced upon receptor solubilization. Pancreatic polypeptide sites also show large sensitivity to modulators of Na+ transport such as N5-substituted amilorides and to RFamides, as different from Y1 or Y2 receptors. Thus, PP binding is modulated by cation-induced changes in site environment (with selectivity for Na+) and ultimately results in a blocking attachment. This would support receptor operation in the presence of ion gradients, as well as prolonged agonist-delimited signaling activity (which can include partial antagonism). Also, this could point to an evolutionary adaptation enabling small numbers of PP receptors to perform extensive metabolic tasks in response to low agonist signals.
- Published
- 2002
28. Dimers of G-Protein Coupled Receptors as Versatile Storage and Response Units
- Author
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Ambikaipakan Balasubramaniam, Floyd R. Sallee, Michael S. Parker, Renu Sah, Edwards A. Park, and Steven L. Parker
- Subjects
Pentamer ,Protein subunit ,homodimer ,Amino Acid Motifs ,Class C GPCR ,CHO Cells ,Binding, Competitive ,Catalysis ,Rhodopsin-like receptors ,Article ,Receptors, G-Protein-Coupled ,Inorganic Chemistry ,lcsh:Chemistry ,Cricetulus ,Cricetinae ,heterodimer ,Arrestin ,Animals ,Humans ,Neuropeptide Y ,Peptide YY ,G-protein heterotrimer ,Amino Acid Sequence ,Physical and Theoretical Chemistry ,Receptor ,Molecular Biology ,lcsh:QH301-705.5 ,heteropentamer ,Spectroscopy ,G protein-coupled receptor ,Binding Sites ,Chemistry ,Organic Chemistry ,General Medicine ,Neuropeptide Y receptor ,Peptide Fragments ,Computer Science Applications ,Receptors, Neuropeptide Y ,Kinetics ,Protein Subunits ,Biochemistry ,lcsh:Biology (General) ,lcsh:QD1-999 ,Rabbits ,Protein Multimerization ,Protein Binding - Abstract
The status and use of transmembrane, extracellular and intracellular domains in oligomerization of heptahelical G-protein coupled receptors (GPCRs) are reviewed and for transmembrane assemblies also supplemented by new experimental evidence. The transmembrane-linked GPCR oligomers typically have as the minimal unit an asymmetric ~180 kDa pentamer consisting of receptor homodimer or heterodimer and a G-protein αβγ subunit heterotrimer. With neuropeptide Y (NPY) receptors, this assembly is converted to ~90 kDa receptor monomer-Gα complex by receptor and Gα agonists, and dimers/heteropentamers are depleted by neutralization of Gαi subunits by pertussis toxin. Employing gradient centrifugation, quantification and other characterization of GPCR dimers at the level of physically isolated and identified heteropentamers is feasible with labeled agonists that do not dissociate upon solubilization. This is demonstrated with three neuropeptide Y (NPY) receptors and could apply to many receptors that use large peptidic agonists.
- Published
- 2014
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29. On the expansion of ribosomal proteins and RNAs in eukaryotes
- Author
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Edwards A. Park, Renu Sah, Floyd R. Sallee, Michael S. Parker, Ambikaipakan Balasubramaniam, and Steven L. Parker
- Subjects
Ribosomal Proteins ,Archaeal Proteins ,Clinical Biochemistry ,Biochemistry ,Ribosome ,Evolution, Molecular ,Bacterial Proteins ,Ribosomal protein ,Animals ,Conserved Sequence ,Genetics ,Mammals ,biology ,Base Sequence ,Eukaryotic Large Ribosomal Subunit ,Organic Chemistry ,Eukaryota ,Prokaryote ,Ribosomal RNA ,biology.organism_classification ,RNA, Bacterial ,Eukaryotic Cells ,Prokaryotic Cells ,RNA, Ribosomal ,Eukaryote ,Hydrophobic and Hydrophilic Interactions ,Bacteria ,Archaea - Abstract
While the ribosome constitution is similar in all biota, there is a considerable increase in size of both ribosomal proteins (RPs) and RNAs in eukaryotes as compared to archaea and bacteria. This is pronounced in the large (60S) ribosomal subunit (LSU). In addition to enlargement (apparently maximized already in lower eukarya), the RP changes include increases in fraction, segregation and clustering of basic residues, and decrease in hydrophobicity. The acidic fraction is lower in eukaryote as compared to prokaryote RPs. In all eukaryote groups tested, the LSU RPs have significantly higher content of basic residues and homobasic segments than the SSU RPs. The vertebrate LSU RPs have much higher sequestration of basic residues than those of bacteria, archaea and even of the lower eukarya. The basic clusters are highly aligned in the vertebrate, but less in the lower eukarya, and only within families in archaea and bacteria. Increase in the basicity of RPs, besides helping transport to the nucleus, should promote stability of the assembled ribosome as well as the association with translocons and other intracellular matrix proteins. The size and GC nucleotide bias of the expansion segments of large LSU rRNAs also culminate in the vertebrate, and should support ribosome association with the endoplasmic reticulum and other intracellular networks. However, the expansion and nucleotide bias of eukaryote LSU rRNAs do not clearly correlate with changes in ionic parameters of LSU ribosomal proteins.
- Published
- 2014
30. Cloned neuropeptide Y (NPY) Y1and pancreatic polypeptide Y4receptors expressed in Chinese hamster ovary cells show considerable agonist-driven internalization, in contrast to the NPY Y2receptor
- Author
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Ingrid Lundell, Michael S. Parker, Magnus M. Berglund, Steven L. Parker, Justin K. Kane, and Ming D. Li
- Subjects
Agonist ,medicine.medical_specialty ,medicine.drug_class ,Chinese hamster ovary cell ,media_common.quotation_subject ,education ,Neuropeptide ,Biology ,Neuropeptide Y receptor ,Biochemistry ,Cell biology ,Endocrinology ,Opioid receptor ,Internal medicine ,medicine ,Enzyme-linked receptor ,Receptor ,Internalization ,media_common - Abstract
Guinea-pig neuropeptide Y1 and rat pancreatic polypeptide Y4 receptors expressed in Chinese hamster ovary cells were internalized rapidly upon attachment of selective peptide agonists. The Y1 and Y2, but not the Y4, receptor also internalized the nonselective neuropeptide Y receptor agonist, human/rat neuropeptide Y. The internalization of guinea-pig neuropeptide Y2 receptor expressed in Chinese hamster ovary cells was small at 37 degrees C, and essentially absent at or below 15 degrees C, possibly in connection to the large molecular size of the receptor-ligand complexes (up to 400 kDa for the internalized fraction). The rate of intake was strongly temperature dependent, with essentially no internalization at 6 degrees C for any receptor. Internalized receptors were largely associated with light, endosome-like particulates. Sucrose dose-dependently decreased the internalization rate for all receptors, while affecting ligand attachment to cell membrane sites much less. Internalization of the Y1 and the Y4 receptors could be blocked, and that of the Y2 receptor significantly inhibited, by phenylarsine oxide, which also unmasked spare cell-surface receptors especially abundant for the Y2 subtype. The restoration of Y1 and Y4 receptors after agonist peptide pretreatment was decreased significantly by cycloheximide and monensin. Thus, in Chinese hamster ovary cells the Y1 and Y4 receptors have much larger subcellular dynamics than the Y2 receptor. This differential could also hold in organismic systems, and is comparable with the known differences in internalization of angiotensin, bradykinin, somatostatin and opioid receptor subtypes.
- Published
- 2001
31. Hypothalamic orexin-A binding sites are downregulated by chronic nicotine treatment in the rat
- Author
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Ming D. Li, J.K. Kane, and Steven L. Parker
- Subjects
Nicotine ,medicine.medical_specialty ,Hypothalamus ,Down-Regulation ,Neuropeptide ,Biology ,Binding, Competitive ,Rats, Sprague-Dawley ,Orexin-A ,Internal medicine ,Orexigenic ,mental disorders ,medicine ,Animals ,Orexins ,Binding Sites ,General Neuroscience ,Neuropeptides ,digestive, oral, and skin physiology ,Intracellular Signaling Peptides and Proteins ,Neuropeptide Y receptor ,Rats ,Orexin ,Pituitary adenylate cyclase-activating peptide ,Endocrinology ,nervous system ,Carrier Proteins ,psychological phenomena and processes ,hormones, hormone substitutes, and hormone antagonists ,medicine.drug - Abstract
Chronic nicotine treatment (4 mg/kg per day; 14 days) significantly reduced the affinity and density of orexin-A binding sites in the anterior hypothalamus of rat brain. There was a significantly lower sensitivity of orexin-A binding to orexin peptides, to the related secretin and pituitary adenylate cyclase activating peptide, and to unrelated neuropeptide Y (NPY). This change correlated with selective downregulation of a fraction of hypothalamic NPY Y(1) receptors. In previous studies, we have demonstrated an increase in the levels of orexin-A peptide and NPY in discrete hypothalamic areas upon nicotine treatment. This finding contradicts an expected increase in the production of these orexigenic peptides in a model where an inverse relationship is observed between food consumption and nicotine treatment. This study provides a possible explanation to this inconsistency in that a decrease in affinity of orexin-A binding could reduce neural orexin signaling, which may contribute to decreased food intake observed in smokers and animals chronically treated with nicotine.
- Published
- 2001
32. Sensitivity of Orexin-A Binding to Phospholipase C Inhibitors, Neuropeptide Y, and Secretin
- Author
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Steven L. Parker, Hirokazu Tanaka, J. K. Kane, Masashi Yanagisawa, and Ming D. Li
- Subjects
Male ,Receptors, Neuropeptide ,medicine.medical_specialty ,Biophysics ,Secretin receptor family ,CHO Cells ,Secretin family ,Biology ,Binding, Competitive ,Biochemistry ,Phospholipases A ,Receptors, G-Protein-Coupled ,Secretin ,Rats, Sprague-Dawley ,Inhibitory Concentration 50 ,Phosphoinositide Phospholipase C ,Prosencephalon ,Orexin Receptors ,Cricetinae ,Internal medicine ,mental disorders ,medicine ,Animals ,Humans ,Magnesium ,Neuropeptide Y ,Enzyme Inhibitors ,Opioid peptide ,Molecular Biology ,Orexins ,Phospholipase A ,Phospholipase C ,Phosphatidylinositol Diacylglycerol-Lyase ,Neuropeptides ,digestive, oral, and skin physiology ,Intracellular Signaling Peptides and Proteins ,Cell Biology ,Neuropeptide Y receptor ,Heterotrimeric GTP-Binding Proteins ,Rats ,Endocrinology ,Guanosine 5'-O-(3-Thiotriphosphate) ,Type C Phospholipases ,Peptide YY ,Calcium ,Carrier Proteins ,hormones, hormone substitutes, and hormone antagonists ,Signal Transduction - Abstract
The binding of [(125)I] orexin-A (Ox-A) to particulates from Chinese hamster ovary (CHO) cells expressing the cloned orexin-A receptor, or from rat forebrain areas, was sensitive to blockers of phosphatidylinositol-specific phospholipase C (PtdIns-PLC) U-73122 and ET-18-OCH(3), little affected by phospholipase A(2) inhibitor quinacrine, and not sensitive to D609, a xanthate inhibitor of phosphatidylcholine-selective PLC. Interaction of the receptor with a PtdIns-PLC was further indicated by a large sensitivity of the binding to Ca(2+). Up to 50% of the binding was sensitive to the G-protein nucleotide site agonist GTP-gamma-S. Ligand attachment to the orexin-A receptor thus depends on an association with both PtdIns-PLC and G-protein alpha-subunits. In all paradigms examined, the binding of [(125)I]orexin-A was competed by human/rat neuropeptide Y (hNPY) and porcine secretin with a potency similar to orexin-A (IC(50) range 30-100 nM). The rank order of potency for NPY-related peptides was hNPY > porcine peptide YY (pPYY) > (Leu(31), Pro(34)) human PYY > human PYY(3-36) > hNPY free acid > human pancreatic polypeptide. Among secretin-related peptides, the rank order of potency was porcine secretin > or = orexin-A > human pituitary adenylate cyclase-activating peptide > orexin-B > porcine vasoactive intestinal peptide. Among opioid peptides, rat beta-endorphin and camel delta-endorphin were much less active than NPY and secretin, and two enkephalins were inactive at 1 microM. In view of high abundance of NPY in forebrain, the above cross-reactivity could indicate a significant contribution of NPY to signaling via orexin-A receptors.
- Published
- 2000
33. FMRFamides exert a unique modulation of rodent pancreatic polypeptide sensitive neuropeptide Y (NPY) receptors
- Author
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Michael S. Parker and Steven L. Parker
- Subjects
Pharmacology ,Agonist ,medicine.medical_specialty ,Physiology ,medicine.drug_class ,Chemistry ,Allosteric regulation ,Neuropeptide ,General Medicine ,Neuropeptide Y receptor ,Endocrinology ,Physiology (medical) ,Peptide YY ,Internal medicine ,medicine ,Pancreatic polypeptide ,FMRFamide ,Receptor - Abstract
FMRFamide and related peptides (RFamides) were found to inhibit the association binding of iodinated human pancreatic polypeptide ([125I]hPP) to Y5-like neuropeptide Y (NPY) receptor in rodent tissues. An allosteric regulation of the activity of the rodent kidney PP-sensitive neuropeptide Y (NPY) receptor by RFamides was indicated by potency decrease with particle concentration in the inhibition of the association binding of125I-labeled human pancreatic polypeptide (hPP) by RFamides at rabbit kidney membranes. The competition by C-terminal hexapeptide of hPP (LTRPRY.NH2) did not show such affinity change. The steady-state binding of hPP showed little sensitivity to any of the RFamides tested. The Y1-selective binding of [125I][Leu31,Pro34]hPYY (at 2 nM hPP) was much less sensitive to RFamides than the binding of [125I]hPP, albeit with some differences across tissue or cell types. The binding of Y2-selective agonist125I-labeled human peptide YY (3-36) was quite insensitive to RFamides. The presence of a unique component in the inhibition of hPP binding by RFamides was further indicated by a degree of antagonism with phospholipase C inhibitor U-73122, and by an only limited cooperation with a N5-amiloride compound, and with alkylator chloroethylclonidine. Change of the chirality of individual residues in the FMRFamide molecule produced a significant reduction of inhibitory potency only with D-Phe in the C-terminal position. Substitution of the (C-3) L-Met by L-Leu greatly increased the inhibitory potency of RFamides relative to otherwise identical congeners. RFamides could act both as ligands of membrane neighbors of the PP receptor, and as competitors of Y5-like NPY receptor epitopes that accommodate the C-terminal aspects of agonist peptides.Key words: Y1receptor, Y2receptor, Y5receptor, RFamide, allosteric interaction, hydrophobic pocket, amino acid chirality.
- Published
- 2000
34. Regulation of Feeding-Associated Peptides and Receptors by Nicotine
- Author
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Ming D. Li, Justin K. Kane, and Steven L. Parker
- Subjects
Leptin ,Male ,Receptors, Neuropeptide ,Dopamine ,Receptors, Nicotinic ,Ion Channels ,Receptors, G-Protein-Coupled ,Nicotine ,Eating ,Orexin Receptors ,Uncoupling Protein 3 ,Neuropeptide Y ,Uncoupling Protein 2 ,Prospective Studies ,Receptor ,Uncoupling Protein 1 ,Smoking ,digestive, oral, and skin physiology ,Intracellular Signaling Peptides and Proteins ,Neuropeptide Y receptor ,Orexin receptor ,Neuroprotective Agents ,Neurology ,Cholecystokinin ,medicine.drug ,Serotonin ,medicine.medical_specialty ,Neuroscience (miscellaneous) ,Neuropeptide ,Nerve Tissue Proteins ,Biology ,Peptide hormone ,Mitochondrial Proteins ,Cellular and Molecular Neuroscience ,Internal medicine ,Appetite Depressants ,Weight Loss ,mental disorders ,Diseases in Twins ,medicine ,Animals ,Humans ,Orexins ,Neuropeptides ,Membrane Proteins ,Membrane Transport Proteins ,Proteins ,Rats ,Receptors, Neuropeptide Y ,Orexin ,Cross-Sectional Studies ,Endocrinology ,Smoking Cessation ,Carrier Proteins ,Energy Metabolism ,Secretory Rate - Abstract
Although numerous epidemiological studies have provided convincing evidence for the inverse association between tobacco smoking and body weight, the molecular mechanisms underlying this relationship are not well-understood. Nicotine, as a potent secretagogue, could be expected to influence the levels and expression of many classes of neurotransmitters, as well as of cell-membrane constituents linked to neurotransmission, including signal transducers and related effectors. A potentially major group of candidate molecules that could be involved in feeding-related actions of nicotine are the numerous neuropeptides and peptide hormones shown in the past two decades to regulate food intake and energy expenditure. These could include neuropeptide Y (NPY), orexins, leptins, and uncoupling proteins (UCPs). Some of these peptides were already shown to respond to nicotine treatment in terms of regulation of levels and of activity at the level of cell-membrane receptors. The primary objective of this review is to summarize our current understanding of the regulatory effects of nicotine on the food intake and energy expenditure as related to the expression levels of leptin, NPY, orexin, uncoupling proteins, and of NPY and orexin receptors.
- Published
- 2000
35. Characterization of Y1, Y2 and Y5 subtypes of the neuropeptide Y (NPY) receptor in rabbit kidney
- Author
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William R. Crowley, Steven L. Parker, and Michael S. Parker
- Subjects
Phospholipase C ,Physiology ,Guanine ,Clinical Biochemistry ,Guanosine ,Biology ,Phospholipase ,Neuropeptide Y receptor ,Biochemistry ,Cellular and Molecular Neuroscience ,chemistry.chemical_compound ,Endocrinology ,chemistry ,Peptide YY ,Mastoparan ,Receptor - Abstract
The binding of two peptide YY/neuropeptide Y analogues selective for major subtypes of neuropeptide Y (NPY) receptors was compared in particulates from rabbit kidney cortex employing modulators of activity of G-proteins, phospholipase enzymes, and ion channels. The binding of (Leu31,Pro34)human peptide YY resembled the patterns observed previously for the brain tissue Y1 receptor, exhibiting a high sensitivity to monovalent cations, disulfide disruptors, guanosine polyphosphates and phospholipase C inhibitors. However, this binding was bimodal in response to human pancreatic polypeptide and to peptides selective for the Y2 subtype of the NPY receptor, displaying a large component pharmacologically similar to the brain Y5 receptor. This kidney Y5-like binding largely shared the sensitivity to monovalent cations, guanine nucleotides and phospholipase C inhibitors found for either the kidney or the brain Y1 receptor, and also was activated by Ca2+ ion. Both Y1- and Y5-like binding in the kidney displayed a uniformly low reactivity to a nonpeptidic Y1 antagonist, BIBP-3226, and to a receptor peptide mimetic, mastoparan analogue MAS-7. The kidney Y2 binding shared the low sensitivity to ionic environment observed for the brain Y2 subtype, and was only partially sensitive to guanine nucleotides or to MAS-7. The Y2 liganding had a sensitivity to phospholipase C inhibitors similar to the Y1/Y5 binding. This reactivity was retained in the fraction of the Y2 receptor persisting detergent solubilization in a high-affinity form, which, however, was activated rather than inhibited by G-protein agonists.
- Published
- 1998
36. Neuropeptide Y Y2 receptors in hypothalamic neuroendocrine areas are up-regulated by estradiol and decreased by progesterone cotreatment in the ovariectomized rat
- Author
-
B. L. Carroll, Steven L. Parker, William R. Crowley, A Fournier, S P Kalra, and S St-Pierre
- Subjects
endocrine system ,medicine.medical_specialty ,Ovariectomy ,Hypothalamus ,Down-Regulation ,Hypothalamus, Middle ,Gonadotropin-releasing hormone ,Biology ,Basal (phylogenetics) ,Endocrinology ,Cell surface receptor ,Piriform cortex ,Internal medicine ,medicine ,Animals ,Humans ,Point Mutation ,Drug Interactions ,Peptide YY ,Receptor ,Progesterone ,Analysis of Variance ,Estradiol ,Luteinizing Hormone ,Neuropeptide Y receptor ,Preoptic Area ,Recombinant Proteins ,humanities ,Prolactin ,Rats ,Receptors, Neuropeptide Y ,Up-Regulation ,Hypothalamus, Anterior ,nervous system ,Organ Specificity ,Ovariectomized rat ,Female ,Peptides ,hormones, hormone substitutes, and hormone antagonists - Abstract
Central neuropeptide Y (NPY) systems are known to stimulate, via the Y1 subtype of NPY receptor, the release of LHRH that leads to surges of LH. Levels of NPY receptors in relation to the above modulation have not been assessed. This study, therefore, examined profiles of NPY receptors in ovariectomized (Ovx) rats and in Ovx rat treated with estradiol (E2) with or without cotreatment with progesterone (P4). [125I]Human PYY containing proline in position 34 [(Pro 34 )hPYY] was used as the Y1 receptor ligand, and [125 I]human peptide YY-(3-36) [hPYY-(3-36)] was used as the Y2 site ligand. Treatment with E2 over 3 days increased Y2 binding in the preoptic hypothalamus and the medial basal hypothalamus, whereas no changes were found in the lateral anterior hypothalamus or the piriform cortex. Administration of P4 (1.5 mg/animal) on the third day of E2 treatment reduced Y2 binding in both the preoptic hypothalamus and the medial basal hypothalamus to or below the density found in Ovx controls. The Y1 receptor levels and the affinity of either Y1 or Y2 binding did not change appreciably with any of the treatments. No significant changes in the binding of wheat germ agglutinin were found at the time of the largest reduction in Y2 receptor numbers by P4, indicating the absence of a major membrane receptor reduction in response to the progestin. The down-regulation of Y2 sites by P4 preceded and accompanied the surge of serum LH induced by the progestin in E2-treated animals. A short term P4 treatment thus appears to reduce the Y2 tone in hypothalamic areas involved in LHRH secretion. This reduction might reinforce Y1 drives known to stimulate the output of LHRH, and thus contribute to LH release.
- Published
- 1996
37. Central Stimulation of Oxytocin Release in the Lactating Rat by N-Methyl-D-Aspartate: Requirement for Coactivation through Non-NMDA Glutamate Receptors or the Glycine Coagonist Site
- Author
-
Steven L. Parker and William R. Crowley
- Subjects
medicine.medical_specialty ,N-Methylaspartate ,Endocrinology, Diabetes and Metabolism ,Radioimmunoassay ,Neuropeptide ,Kainate receptor ,Stimulation ,AMPA receptor ,Oxytocin ,Cellular and Molecular Neuroscience ,Receptors, Glycine ,Endocrinology ,Internal medicine ,medicine ,Animals ,Lactation ,Receptor ,alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid ,Endocrine and Autonomic Systems ,Chemistry ,Glutamate receptor ,Rats ,Receptors, Glutamate ,nervous system ,Glycine ,NMDA receptor ,Female - Abstract
Excitatory amino acid (EAA) neurotransmitters participate in the regulation of secretion of several neuropeptides, including oxytocin (OT), via actions at different receptors. In earlier studies, release of OT could be achieved reliably by injection into the supraoptic nucleus (SON) of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate receptor agonists, but not by treatment with N-methyl-D-aspartate (NMDA) alone. This prompted further examination of the possible role of NMDA receptors in OT release following central coapplication of NMDA and AMPA-site agonists, or of NMDA and agonists active at the glycine coagonist site. The agonists were injected into the right SON, the right paraventricular nucleus (PVN), or into the third ventricle (3V) of nonsuckled lactating rats. Cotreatment with NMDA and AMPA (using doses that alone did not include OT release) elicited a strong OT release in all animals by either the SON or the PVN route, and this was attenuated by pretreatment/cotreatment with specific antagonists of either the NMDA or the AMPA receptor. The SON area or 3V coinjection of NMDA and the NMDA/glycine site agonists glycine or D-serine also induced OT discharges in all animals, while cotreatment in the PVN did not result in uniform OT discharges. This release was potently reduced by cotreatment with the specific NMDA/glycine site antagonist 5, 7-dichlorokynurenate (DCK). L-Serine somewhat increased the frequency of discharge-type response to NMDA, while intra-SON coinjection of L-leucine did not stimulate OT release. D-Serine alone stimulated the release of OT much less than in combination with NMDA, and with no obvious dose dependence. The suckling-induced release of OT was attenuated, but not abolished, by DCK, while PRL release was briefly stimulated by this agent. A physiological role for the NMDA receptor in OT release is clearly supported by these studies. NMDA receptor activation in the lactating rat may result from either an allosteric stimulation by glycine site agonists, or a synergistic interaction with the AMPA/kainate group of excitatory amino acid receptors.
- Published
- 1995
38. Surface masking shapes the traffic of the neuropeptide Y Y2 receptor
- Author
-
Renu Sah, Michael S. Parker, and Steven L. Parker
- Subjects
Physiology ,media_common.quotation_subject ,Population ,Guinea Pigs ,Molecular Sequence Data ,Digitonin ,CHO Cells ,Biology ,Biochemistry ,Article ,Arsenicals ,Cellular and Molecular Neuroscience ,chemistry.chemical_compound ,Surface-Active Agents ,Endocrinology ,Cricetinae ,Cell Adhesion ,Animals ,Humans ,Phenylarsine oxide ,Peptide YY ,Protein Interaction Domains and Motifs ,Amino Acid Sequence ,Filipin ,Receptor ,education ,Cell adhesion ,Internalization ,Edetic Acid ,media_common ,G protein-coupled receptor ,Chelating Agents ,education.field_of_study ,Binding Sites ,Neuropeptide Y receptor ,Receptors, Neuropeptide Y ,Protein Transport ,HEK293 Cells ,chemistry ,Pertussis Toxin ,Guanosine 5'-O-(3-Thiotriphosphate) ,Biophysics ,Protein Binding - Abstract
The neuropeptide Y (NPY) Y2 receptor shows a large masked surface population in adherent CHO cells or in forebrain cell aggregates, but not in dispersed cells or in particulates from these sources. This is related to adhesion via acidic motifs in the extracellular N-terminal domain. Masking of the Y2 receptor is lifted by non-permeabilizing mechanical dispersion of cells, which also increases internalization of Y2 agonists. Mechanical dispersion and detachment by EDTA expose the same number of surface sites. As we have already shown, phenylarsine oxide (PAO), a cysteine-bridging agent, and to a lesser extent also the cysteine alkylator N-ethylmaleimide, unmask the surface Y2 sites without cell detachment or permeabilization. We now demonstrate that unmasking by permeabilizing but non-detaching treatment with cholesterol-binding detergents digitonin and edelfosine compares with and overlaps that of PAO. The caveolar/raft cholesterol-targeting macrolide filipin III however produces only partial unmasking. Depletion of the surface sites by N-terminally clipped Y2 agonists indicates larger accessibility for a short highly helical peptide. These findings indicate presence of a dynamic masked pool including majority of the cell surface Y2 receptors in adherent CHO cells. This compartmentalization is obviously involved in the low internalization of Y2 receptors in these cells.
- Published
- 2012
39. Maintenance of Y receptor dimers in epithelial cells depends on interaction with G-protein heterotrimers
- Author
-
Trevor W. Sweatman, Anne-Marie Estes, Ambikaipakan Balasubramaniam, Michael S. Parker, Edwards A. Park, Floyd R. Sallee, Kathleen McAllen, Renu Sah, Steven L. Parker, and Mary W. Walker
- Subjects
Swine ,Clinical Biochemistry ,B-cell receptor ,CHO Cells ,Biology ,Biochemistry ,Cricetulus ,Cricetinae ,Enzyme-linked receptor ,Animals ,Humans ,5-HT5A receptor ,Receptor ,Protease-activated receptor 2 ,Insulin-like growth factor 1 receptor ,Liver receptor homolog-1 ,Organic Chemistry ,Epithelial Cells ,Interleukin-13 receptor ,Molecular biology ,Heterotrimeric GTP-Binding Proteins ,Rats ,Receptors, Neuropeptide Y ,Pertussis Toxin ,Biophysics ,Cattle ,Dimerization ,Protein Binding - Abstract
Treatment of CHO cells expressing human Y receptors (Y(1), Y(2) or Y4 subtype) with pertussis toxin results in a large decrease in functional receptors, with a preferential loss of heteropentameric assemblies of receptor dimers and G-protein trimers. This occurs in parallel to inactivation of the nucleotide site of Gi α subunits, with a half period of about 4 h. The loss could be mainly due to proteolysis at the level of recycling/perinuclear endosomes, and of receptor completion in the ER, since it is reduced by co-treatment with ammonium chloride, an inhibitor of particulate proteinases. Antagonists do not strongly decrease the heteropentameric fraction. These findings indicate that the upkeep of Y receptor dimers in epithelial cell lines depends on the association of receptor oligomers with functional Gi α subunits. This interaction could use the juxtamembrane helix 8 in the fourth intracellular domain, and could also be supported by the C-terminal helix of the third intracellular loop, as outlined in the companion review (Parker et al., Amino Acids, doi: 10.1007/s00726-010-0616-1 , 2010).
- Published
- 2010
40. Two intracellular helices of G-protein coupling receptors could generally support oligomerization and coupling with transducers
- Author
-
Floyd R. Sallee, Steven L. Parker, Edwards A. Park, and Michael S. Parker
- Subjects
G protein-coupled receptor kinase ,Organic Chemistry ,Clinical Biochemistry ,Biology ,Biochemistry ,Rhodopsin-like receptors ,Protein Structure, Secondary ,Protein Structure, Tertiary ,Receptors, G-Protein-Coupled ,Protein structure ,GTP-Binding Proteins ,Helix ,Biophysics ,Animals ,Humans ,Signal transduction ,Protein Multimerization ,Receptor ,Intracellular ,G protein-coupled receptor ,Signal Transduction - Abstract
For many G-protein coupling receptors (GPCRs), the upkeep of receptor dimers could depend on association with functional Gi α subunits. This is known for Y1, Y2 and Y4 neuropeptide Y receptors [presented in the companion paper (Estes et al., Amino Acids, doi: 10.1007/s00726-010-0642-z , 2010)]. Interactions with transducers use mainly intracellular domains of the receptors. Intracellular loops 1 and 2 in GPCRs are short and lack extensive helicity that could support transducer anchoring. Interaction with G-proteins is known to use the juxtamembrane Helix 8 in the fourth intracellular domain, for which we document a helix-stabilizing n/(n + 4) pattern of large hydrophobic sidechains. Another intracellular helix located in the C-terminal portion of the third intracellular loop does not display a strong stabilizing pattern, and is found in many studies to serve dynamically in association and activation of transducers and effectors. We show that these tracts share features across metazoan phyla not only in opsins and opsin-like receptors (including the Y receptors), but also in Taste-2 and Frizzled receptors. Similarities of these helices across GPCR groups could have both phylogenetic and functional roots.
- Published
- 2010
41. Two intracellular helices of G‐protein coupling receptors as transducer‐attaching entities
- Author
-
Michael S. Parker and Steven L. Parker
- Subjects
Coupling (electronics) ,Transducer ,Chemistry ,G protein ,Genetics ,Biophysics ,Receptor ,Molecular Biology ,Biochemistry ,Intracellular ,Biotechnology - Published
- 2010
42. Neurotransmitter and Neurohormonal Regulation of Oxytocin Secretion in Lactationa
- Author
-
William R. Crowley, W. E. Arm Strong, Steven L. Parker, Clark E. Grosvenor, and L. H. Spinolo
- Subjects
medicine.medical_specialty ,Dopamine ,Biology ,Oxytocin ,General Biochemistry, Genetics and Molecular Biology ,Receptors, Dopamine ,Norepinephrine ,chemistry.chemical_compound ,History and Philosophy of Science ,Internal medicine ,medicine ,Animals ,Lactation ,Norepinephrine metabolism ,Neurotransmitter ,Receptor ,Dopamine metabolism ,General Neuroscience ,Oxytocin secretion ,Oxytocin receptor ,Prolactin ,Rats ,Endocrinology ,chemistry ,Female ,Supraoptic Nucleus ,Paraventricular Hypothalamic Nucleus - Published
- 1992
43. Activation of Central D-1 Dopamine Receptors Stimulates Oxytocin Release in the Lactating Rat: Evidence for Involvement of the Hypothalamic Paraventricular and Supraoptic Nuclei
- Author
-
William R. Crowley and Steven L. Parker
- Subjects
medicine.medical_specialty ,Microinjections ,Endocrinology, Diabetes and Metabolism ,Radioimmunoassay ,Neuropeptide ,Biology ,Oxytocin ,Supraoptic nucleus ,Cellular and Molecular Neuroscience ,Endocrinology ,Dopamine ,Internal medicine ,medicine ,Animals ,Lactation ,Injections, Intraventricular ,Endocrine and Autonomic Systems ,Receptors, Dopamine D1 ,Rats, Inbred Strains ,Oxytocin receptor ,Rats ,Dopamine receptor ,Hypothalamus ,Catecholamine ,Female ,2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine ,Supraoptic Nucleus ,Paraventricular Hypothalamic Nucleus ,medicine.drug - Abstract
The stimulatory effect of dopamine (DA) on the release of oxytocin (OT) in lactating rats is exerted at the D-1 DA receptor subtype. Because the neural loci mediating this effect have not been identified, the objective of the present studies was to test whether OT release in the lactating rat would be elevated after central administration of a D-1 DA receptor agonist into the third ventricle (3V) or directly into either the rostral paraventricular/anterior commissural nucleus area (PVN/ACN), the central paraventricular nucleus area, or the supraoptic nucleus (SON), all of which contain OT neurosecretory cells. Lactating rats were implanted with a stainless steel cannula directed into one of the above areas or into the arcuate-ventromedial region of the medial basal hypothalamus (MBH), or sites dorsal to the PVN/ACN or SON, which served as anatomical controls. After 6-7 days of recovery, each animal received an intra-atrial cannula for sequential blood sampling, and was used in experiments 24 h later. Animals were separated from their litters, and following a period of basal blood sampling, received central microinjections of either vehicle, the D-1 DA receptor agonist SKF-38393, or the D-2 DA receptor agonist quinpirole, and blood samples were removed periodically for 60 min. An injection of angiotensin II (Ang II, 100 ng) was made into each site as a positive control for OT release.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1992
44. Neuropeptide Y (NPY) forms stable complexes with the Y1 receptor and G‐protein alpha subunits, reducing the transduction and internalization of the receptor
- Author
-
Michael S. Parker, Ambikaipakan Balasubramaniam, Floyd R. Sallee, Renu Sah, and Steven L. Parker
- Subjects
Neuropeptide Y receptor Y1 ,Neuropeptide Y receptor Y2 ,G protein ,Chemistry ,media_common.quotation_subject ,Interleukin 5 receptor alpha subunit ,Neuropeptide FF receptor ,Neuropeptide Y receptor ,Biochemistry ,Genetics ,Enzyme-linked receptor ,Internalization ,Molecular Biology ,Biotechnology ,media_common - Published
- 2009
45. Neuropeptide Y Modulates the Binding of a Gonadotropin-Releasing Hormone (GnRH) Analog to Anterior Pituitary GnRH Receptor Sites*
- Author
-
William R. Crowley, Steven L. Parker, and Satya P. Kalra
- Subjects
Pituitary gland ,medicine.medical_specialty ,Magnesium Chloride ,Gonadotropin-releasing hormone ,Biology ,Gastrointestinal Hormones ,Gonadotropin-Releasing Hormone ,Endocrinology ,Anterior pituitary ,Pituitary Gland, Anterior ,Internal medicine ,mental disorders ,medicine ,Animals ,Neuropeptide Y ,Peptide YY ,Galanin ,Rats, Inbred Strains ,Neuropeptide Y receptor ,humanities ,Rats ,medicine.anatomical_structure ,Hypothalamus ,Female ,Peptides ,Receptors, LHRH ,Gonadotropin-releasing hormone receptor - Abstract
Neuropeptide Y (NPY) increases LH secretion in part by enhancing the release of LH in response to GnRH. The present studies examined whether NPY influences the binding of GnRH to its receptors and also assessed whether specific binding sites for NPY exist in rat anterior pituitary membranes. In concentrations from 66-200 nM, NPY dose-dependently enhanced the binding of a 125I-labeled GnRH agonist, [D-Ala6, des-Gly10]GnRH ethylamide (GnRHa; 30 pM) to anterior pituitary membranes of chronically ovariectomized rats; higher concentrations of NPY were ineffective. At 200 nM, NPY significantly increased the high affinity binding of the GnRHa to these membranes, without change in the apparent maximum binding capacity. Further, 200 nM NPY significantly increased the binding of [125I]GnRHa when this tracer was used in concentrations of less than 100 pM, but NPY did not increase the binding of higher concentrations of [125I]GnRHa. Peptide YY, a gastrointestinal peptide structurally and functionally related to NPY, and the hypothalamic/pituitary peptide galanin (both at 200 nM) also increased the binding of [125I]GnRHa (30 pM) to anterior pituitary membranes, but to approximately one third of the extent produced by NPY. Salmon calcitonin, which, similar to NPY, is a strongly hydrophobic neuroendocrine peptide, did not alter GnRHa binding. Mg++ ion dose-dependently reduced the affinity of GnRHa binding, without changing the maximum binding capacity, and also attenuated the increase in GnRHa binding produced by NPY. To further characterize the nature of NPY interaction with anterior pituitary membranes, [125I] peptide YY was used to label NPY binding sites in anterior pituitary and hypothalamic membranes from ovariectomized rats. Specific, and predominantly high affinity, NPY binding sites were demonstrated in hypothalamic membranes, whereas NPY binding to anterior pituitary membranes could be resolved into high and low affinity components. These results show that at low nanomolar concentrations, NPY can enhance the association of GnRHa to receptors in anterior pituitary membranes. This demonstration of increased GnRHa binding in the presence of NPY may explain in part the action of this neuropeptide to potentiate GnRH-induced LH release from anterior pituitary cells.
- Published
- 1991
46. Prolactin Stimulates the Release of Oxytocin in Lactating Rats: Evidence for a Physiological Role via an Action at the Neural Lobe
- Author
-
Clark E. Grosvenor, Celia D. Sladek, William E. Armstrong, Steven L. Parker, and William R. Crowley
- Subjects
endocrine system ,medicine.medical_specialty ,Vasopressin ,Endocrinology, Diabetes and Metabolism ,Biology ,Oxytocin ,Inhibitory postsynaptic potential ,Prolactin cell ,Cellular and Molecular Neuroscience ,Endocrinology ,Dopamine ,Internal medicine ,Lactation ,medicine ,Animals ,Bromocriptine ,Endocrine and Autonomic Systems ,Immunization, Passive ,Domperidone ,Electric Stimulation ,Prolactin ,Rats ,medicine.anatomical_structure ,Growth Hormone ,Pituitary Gland ,Catecholamine ,Female ,hormones, hormone substitutes, and hormone antagonists ,medicine.drug - Abstract
The present studies were designed to investigate whether prolactin (PRL) influences the secretion of oxytocin (OT) in lactating rats, and to test whether the previously reported inhibitory and stimulatory effects of dopamine-2 (D-2) agonists and antagonists, respectively, on OT release might be secondary to their respective inhibitory and stimulatory effects on the release of PRL. Intravenous administration of either rat (r) or ovine (o) PRL to lactating, nonsuckled rats increased basal plasma concentrations of OT. rGH was ineffective, but administration of oGH did produce some stimulation of OT release. Both oPRL and rPRL significantly enhanced the electrical stimulation-induced release of OT from isolated stalk-neurointermediate lobes, in vitro, without affecting the basal release of the peptide. oGH was ineffective on basal or stimulated in vitro OT release, and neither hormone altered basal or stimulation-induced release of vasopressin from these tissues. Both rPRL and oPRL reversed the inhibitory effect of the D-2 dopamine agonist bromocriptine. Immunoneutralization of circulating PRL with a highly specific antiserum abolished the increases in OT in response to either suckling or to administration of the D-2 dopamine antagonist domperidone.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1991
47. Dimers of the neuropeptide Y (NPY) Y2 receptor show asymmetry in agonist affinity and association with G proteins
- Author
-
Michael S. Parker, Trevor W. Sweatman, Steven L. Parker, Edwards A. Park, Ambikaipakan Balasubramaniam, Renu Sah, and Floyd R. Sallee
- Subjects
Agonist ,G protein ,medicine.drug_class ,Stereochemistry ,Phosphodiesterase Inhibitors ,Dimer ,Trimer ,Protomer ,CHO Cells ,Biochemistry ,chemistry.chemical_compound ,Mice ,Cricetulus ,GTP-Binding Proteins ,Cricetinae ,medicine ,Animals ,Humans ,Estrenes ,Receptor ,Molecular Biology ,G protein-coupled receptor ,Cell Biology ,Neuropeptide Y receptor ,Pyrrolidinones ,Receptors, Neuropeptide Y ,chemistry ,Guanosine 5'-O-(3-Thiotriphosphate) ,Rabbits ,Protein Multimerization - Abstract
In conditions precluding activation of G proteins, the binding of agonists to dimers of the neuropeptide Y (NPY) Y2 receptor shows two components of similar size, but differing in affinity. The dimers of all NPY receptors are solubilized as approximately 180-kDa complexes containing one G protein alpha beta gamma trimer. These heteropentamers are stable to excess agonists, chelators, and alkylators. However, dispersion in the weak surfactant cholate releases approximately 300-kDa complexes. These findings indicate that both protomers in the Y2 dimer are associated with G protein heterotrimers, but the extent of interaction depends on affinity for the agonist peptide. The G protein in contact with the first-liganded, higher-affinity protomer should have a stronger interaction with the receptor and a larger probability of activation.
- Published
- 2008
48. Oligomerization of Neuropeptide Y (NPY) Y2 Receptors in CHO Cells Depends on Functional Pertussis Toxin-Sensitive G-Proteins
- Author
-
Ambikaipakan Balasubramaniam, Michael S. Parker, Steven L. Parker, and Floyd R. Sallee
- Subjects
Physiology ,G protein ,Protein subunit ,Clinical Biochemistry ,CHO Cells ,Biology ,GTP-Binding Protein alpha Subunits, Gi-Go ,medicine.disease_cause ,Pertussis toxin ,Arginine ,Biochemistry ,Article ,Cellular and Molecular Neuroscience ,Endocrinology ,Cricetulus ,Cricetinae ,medicine ,Animals ,Humans ,Receptor ,G protein-coupled receptor ,Toxin ,Chinese hamster ovary cell ,Benzazepines ,Neuropeptide Y receptor ,Molecular biology ,Receptors, Neuropeptide Y ,Protein Subunits ,Pertussis Toxin ,Solubility ,Dimerization - Abstract
Human neuropeptide Y Y2 receptors expressed in CHO cells are largely oligomeric, and upon solubilization are recovered by density gradient centrifugation as approximately 180 kDa complexes of receptor dimers and G-protein heterotrimers. A large fraction of the receptors is inactivated in the presence of pertussis toxin, in parallel with inactivation of Gi alpha subunits (with half-periods of about 4 h for both). This is accompanied by a very long-lasting loss of receptor dimers and of masked surface Y2 sites (an apparent receptor reserve pre-coupled mainly to Gi alpha subunit-containing G-proteins). However, surface Y2 receptors accessible to large peptide agonists are much less sensitive to the toxin. All surface Y2 receptors are rapidly blocked by Y2 antagonist BIIE0246, with a significant loss of the dimers, but with little change of basal Gi activity. However, both dimers and Y2 receptor compartmentalization are restored within 24 h after removal of the antagonist. In CHO cells, the maintenance and organization of Y2 receptors appear to critically depend on functional pertussis toxin-sensitive G-proteins.
- Published
- 2007
49. An ion-responsive motif in the second transmembrane segment of rhodopsin-like receptors
- Author
-
Y. Y. Wong, Michael S. Parker, and Steven L. Parker
- Subjects
Opsin ,Rhodopsin ,Stereochemistry ,Clinical Biochemistry ,Amino Acid Motifs ,Receptors, Cell Surface ,Biology ,Biochemistry ,Rhodopsin-like receptors ,Evolution, Molecular ,Protein structure ,Animals ,Humans ,Receptor ,Organic Chemistry ,Sodium ,Cations, Monovalent ,Transmembrane protein ,Protein Structure, Tertiary ,Transmembrane domain ,Amino Acid Substitution ,biology.protein ,Signal transduction ,Signal Transduction - Abstract
A L(M)xxxD(N, E) motif (x=a non-ionic amino acid residue, most frequently A, S, L or F; small capitals indicating a minor representation) is found in the second transmembrane (tm2) segment of most G-protein coupling metazoan receptors of the rhodopsin family (Rh-GPCRs). Changes in signal transduction, agonist binding and receptor cycling are known for numerous receptors bearing evolved or experimentally introduced mutations in this tm2 motif, especially of its aspartate residue. The [Na(+)] sensitivity of the receptor-agonist interaction relates to this aspartate in a number of Rh-GPCRs. Native non-conservative mutations in the tm2 motif only rarely coincide with significant changes in two other ubiquitous features of the rhodopsin family, the seventh transmembrane N(D)PxxY(F) motif and the D(E)RY(W,F) or analogous sequence at the border of the third transmembrane helix and the second intracellular loop. Native tm2 mutations with Rh-GPCRs frequently result in constitutive signaling, and with visual opsins also in shifts to short-wavelength sensitivity. Substitution of a strongly basic residue for the tm2 aspartate in Taste-2 receptors could be connected to a lack of sodium sensing by these receptors. These properties could be consistent with ionic interactions, and even of ion transfer, that involve the tm2 motif. A decrease in cation sensing by this motif is usually connected to an enhanced constitutive interaction of the mutated receptors with cognate G- proteins, and also relates to both the constitutive and the overall activity of the short-wavelength opsins.
- Published
- 2007
50. Parallel inactivation of Y2 receptor and G-proteins in CHO cells by pertussis toxin
- Author
-
Ambikaipakan Balasubramaniam, Floyd R. Sallee, Michael S. Parker, Steven L. Parker, and Renu Sah
- Subjects
medicine.medical_specialty ,Physiology ,G protein ,Clinical Biochemistry ,Gi alpha subunit ,Blotting, Western ,Gene Expression ,CHO Cells ,Pertussis toxin ,Biochemistry ,Ammonium Chloride ,Adenylyl cyclase ,Cellular and Molecular Neuroscience ,chemistry.chemical_compound ,Endocrinology ,Cricetulus ,GTP-Binding Proteins ,Internal medicine ,Cricetinae ,medicine ,Animals ,Humans ,Receptor ,G protein-coupled receptor ,biology ,Neuropeptide Y receptor ,Receptors, Neuropeptide Y ,chemistry ,Gq alpha subunit ,Pertussis Toxin ,Guanosine 5'-O-(3-Thiotriphosphate) ,biology.protein ,Adenylyl Cyclases ,Protein Binding - Abstract
The Y(2) receptor for neuropeptide Y (NPY) interacts with pertussis toxin (PTX)-sensitive G-proteins, but little is known about interdependence of their levels and functions. We found that PTX reduces Y(2) receptors expressed in CHO cells in parallel to inactivation of Gi G-proteins, to loss of inhibition by Y(2) agonists of forskolin-stimulated adenylyl cyclase, and to decrease in the binding of GTP-gamma-S. These losses were attenuated by the endosome alkalinizer ammonium chloride. Affinity of the Y(2) receptor was not changed by PTX treatment. Prolonged treatment induced a large decrease of Y(2) receptor immunoreactivity (more than 70% in 48 h). The Gi(3) alpha-subunit immunoreactivity decreased slowly (about 46% in 48 h). There was a significant increase in Gq alpha immunoreactivity and in fraction of Y(2) binding sensitive to a Gq-selective antagonist. Possibly linked to that, the surface Y(2) sites and the internalization of the Y(2) receptor were less than 40% reduced. However, the abundant masked Y(2) sites were eliminated by the toxin, and could be mainly coupled to PTX-sensitive G-proteins.
- Published
- 2006
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