90 results on '"George A. Gutman"'
Search Results
2. Calcium- and sodium-activated potassium channels (KCa, KNa) in GtoPdb v.2023.1
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Heike Wulff, Aguan D. Wei, Leonard K. Kaczmarek, George A. Gutman, Stephan Grissmer, K. George Chandy, and Richard Aldrich
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General Medicine ,General Chemistry - Abstract
Calcium- and sodium- activated potassium channels are members of the 6TM family of K channels which comprises the voltage-gated KV subfamilies, including the KCNQ subfamily, the EAG subfamily (which includes hERG channels), the Ca2+-activated Slo subfamily (actually with 6 or 7TM) and the Ca2+- and Na+-activated SK subfamily (nomenclature as agreed by the NC-IUPHAR Subcommittee on Calcium- and sodium-activated potassium channels [126]). As for the 2TM family, the pore-forming a subunits form tetramers and heteromeric channels may be formed within subfamilies (e.g. KV1.1 with KV1.2; KCNQ2 with KCNQ3).
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- 2023
3. Voltage-gated potassium channels (Kv) in GtoPdb v.2023.1
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Xiaoliang Wang, James S. Trimmer, Walter Stühmer, Michael C. Sanguinetti, Bernardo Rudy, Gail A. Robertson, Luis A. Pardo, Jeanne Nerbonne, David Mckinnon, Michel Lazdunski, Lily Y. Jan, George A. Gutman, Stephan Grissmer, M. Hunter Giese, K. George Chandy, and Bernard Attali
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General Medicine ,General Chemistry - Abstract
The 6TM family of K channels comprises the voltage-gated KV subfamilies, the EAG subfamily (which includes hERG channels), the Ca2+-activated Slo subfamily (actually with 7TM, termed BK) and the Ca2+-activated SK subfamily. These channels possess a pore-forming α subunit that comprise tetramers of identical subunits (homomeric) or of different subunits (heteromeric). Heteromeric channels can only be formed within subfamilies (e.g. Kv1.1 with Kv1.2; Kv7.2 with Kv7.3). The pharmacology largely reflects the subunit composition of the functional channel.Kv7 channelsKv7.1-Kv7.5 (KCNQ1-5) K+ channels are voltage-gated K+ channels with major roles in neurons, muscle cells and epithelia where they underlie physiologically important K+ currents, such as the neuronal M-current and the cardiac IKs. Genetic deficiencies in all five KCNQ genes result in human excitability disorders, including epilepsy, autism spectrum disorders, cardiac arrhythmias and deafness. Thanks to the recent knowledge of the structure and function of human KCNQ-encoded proteins, these channels are increasingly used as drug targets for treating diseases [326, 2, 767].
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- 2023
4. IUPHAR-DB: the IUPHAR database of G protein-coupled receptors and ion channels.
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Anthony J. Harmar, Rebecca A. Hills, Edward M. Rosser, Martin Jones, Oscar Peter Buneman, Donald R. Dunbar, Stuart D. Greenhill, Valerie A. Hale, Joanna L. Sharman, Tom I. Bonner, William A. Catterall, Anthony P. Davenport, Philippe Delagrange, Colin T. Dollery, Steven M. Foord, George A. Gutman, Vincent Laudet, Richard R. Neubig, Eliot H. Ohlstein, Richard W. Olsen, John A. Peters, Jean-Philippe Pin, Robert R. Ruffolo, David B. Searls, Mathew W. Wright, and Michael Spedding
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- 2009
- Full Text
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5. Calcium- and sodium-activated potassium channels (KCa, KNa) in GtoPdb v.2021.3
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Stephan Grissmer, Aguan D. Wei, Leonard K. Kaczmarek, Richard W. Aldrich, George A. Gutman, K. George Chandy, and Heike Wulff
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Subfamily ,biology ,Chemistry ,Stereochemistry ,Sodium ,hERG ,biology.protein ,chemistry.chemical_element ,Calcium ,Potassium channel ,K channels - Abstract
Calcium- and sodium- activated potassium channels are members of the 6TM family of K channels which comprises the voltage-gated KV subfamilies, including the KCNQ subfamily, the EAG subfamily (which includes hERG channels), the Ca2+-activated Slo subfamily (actually with 6 or 7TM) and the Ca2+- and Na+-activated SK subfamily (nomenclature as agreed by the NC-IUPHAR Subcommittee on Calcium- and sodium-activated potassium channels [125]). As for the 2TM family, the pore-forming a subunits form tetramers and heteromeric channels may be formed within subfamilies (e.g. KV1.1 with KV1.2; KCNQ2 with KCNQ3).
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- 2021
6. Voltage-gated potassium channels (Kv) in GtoPdb v.2021.3
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Bernardo Rudy, Bernard Attali, Lily Yeh Jan, Xiaoliang Wang, M. Hunter Giese, James S. Trimmer, David McKinnon, George A. Gutman, Jeanne M. Nerbonne, Michel Lazdunski, Stephan Grissmer, Walter Stühmer, K. George Chandy, Gail A. Robertson, Luis A. Pardo, and Michael C. Sanguinetti
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Α subunit ,Subfamily ,biology ,Chemistry ,Stereochemistry ,Protein subunit ,hERG ,biology.protein ,Homomeric ,Voltage-gated potassium channel ,K channels - Abstract
The 6TM family of K channels comprises the voltage-gated KV subfamilies, the EAG subfamily (which includes hERG channels), the Ca2+-activated Slo subfamily (actually with 7TM, termed BK) and the Ca2+-activated SK subfamily. These channels possess a pore-forming α subunit that comprise tetramers of identical subunits (homomeric) or of different subunits (heteromeric). Heteromeric channels can only be formed within subfamilies (e.g. Kv1.1 with Kv1.2; Kv7.2 with Kv7.3). The pharmacology largely reflects the subunit composition of the functional channel.
- Published
- 2021
7. Calcium- and sodium-activated potassium channels (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database
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Heike Wulff, Leonard K. Kaczmarek, George A. Gutman, Aguan D. Wei, Richard W. Aldrich, K. George Chandy, and Stephan Grissmer
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Subfamily ,biology ,Chemistry ,Stereochemistry ,Sodium ,hERG ,biology.protein ,chemistry.chemical_element ,Calcium ,Potassium channel ,K channels - Abstract
Calcium- and sodium- activated potassium channels are members of the 6TM family of K channels which comprises the voltage-gated KV subfamilies, including the KCNQ subfamily, the EAG subfamily (which includes herg channels), the Ca2+-activated Slo subfamily (actually with 6 or 7TM) and the Ca2+- and Na+-activated SK subfamily (nomenclature as agreed by the NC-IUPHAR Subcommittee on Calcium- and sodium-activated potassium channels [124]). As for the 2TM family, the pore-forming a subunits form tetramers and heteromeric channels may be formed within subfamilies (e.g. KV1.1 with KV1.2; KCNQ2 with KCNQ3).
- Published
- 2019
8. Kv1.3 channel‐blocking immunomodulatory peptides from parasitic worms: implications for autoimmune diseases
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Vikas Dhawan, George K. Chandy, Satendra Chauhan, James D. Swarbrick, Shihchieh Jeff Chang, Mariel Gindin, Hai M. Nguyen, Luz M. Londono, Biswaranjan Mohanty, Rosendo Estrada, Sanjeev K. Upadhyay, Heike Wulff, Sandeep Chhabra, Mark R. Tanner, George A. Gutman, Jesus G. Valenzuela, Christine Beeton, Raymond S. Norton, Michael W. Pennington, Redwan Huq, Shawn P. Iadonato, and Peter J. Hotez
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Models, Molecular ,Male ,Magnetic Resonance Spectroscopy ,Protein Conformation ,Physiology ,T-Lymphocytes ,Medical Physiology ,Sequence Homology ,C-C chemokine receptor type 7 ,medicine.disease_cause ,Biochemistry ,Brugia malayi ,Research Communications ,Mice ,Models ,Receptors ,2.1 Biological and endogenous factors ,Hypersensitivity, Delayed ,Aetiology ,Peptide sequence ,Cells, Cultured ,Phylogeny ,Cultured ,Kv1.3 Potassium Channel ,Inbred Lew ,biology ,Effector ,Delayed ,probiotic worm therapy ,Electrophysiology ,Amino Acid ,Infectious Diseases ,Cytokines ,Female ,hookworm ,Ancylostoma caninum ,Biotechnology ,Receptors, CCR7 ,Biochemistry & Molecular Biology ,Cells ,Molecular Sequence Data ,T lymphocytes ,Autoimmune Disease ,Autoimmune Diseases ,Structure-Activity Relationship ,Cnidarian Venoms ,Rare Diseases ,Immune system ,Clinical Research ,Helminths ,parasitic diseases ,Hypersensitivity ,Potassium Channel Blockers ,Genetics ,medicine ,Animals ,Humans ,Amino Acid Sequence ,Molecular Biology ,Cell Proliferation ,Ancylostoma ceylanicum ,Sequence Homology, Amino Acid ,Toxin ,Molecular ,ShK ,Fibroblasts ,biology.organism_classification ,Peptide Fragments ,Rats ,Rats, Inbred Lew ,Immunology ,ion channel modulator ,Biochemistry and Cell Biology ,Immunologic Memory ,CCR7 - Abstract
© FASEB. The voltage-gated potassium (Kv) 1.3 channel is widely regarded as a therapeutic target for immunomodulation in autoimmune diseases. ShK-186, a selective inhibitor of Kv1.3 channels, ameliorates autoimmune diseases in rodent models, and human phase 1 trials of this agent in healthy volunteers have been completed. In this study, we identified and characterized a large family of Stichodactyla helianthus toxin (ShK)-related peptides in parasitic worms. Based on phylogenetic analysis, 2 worm peptides were selected for study: AcK1, a 51-residue peptide expressed in the anterior secretory glands of the dog-infecting hookworm Ancylostoma caninum and the human-infecting hookworm Ancylostoma ceylanicum, and BmK1, the C-terminal domain of a metalloprotease from the filarial worm Brugia malayi. These peptides in solution adopt helical structures closely resembling that of ShK. At doses in the nanomolar-micromolar range, they block native Kv1.3 in human T cells and cloned Kv1.3 stably expressed in L929 mouse fibroblasts. They preferentially suppress the proliferation of rat CCR7-effector memory T cells without affecting naive and central memory subsets and inhibit the delayed-type hypersensitivity (DTH) response caused by skin-homing effector memory T cells in rats. Further, they suppress IFNγ production by human T lymphocytes. ShK-related peptides in parasitic worms may contribute to the potential beneficial effects of probiotic parasitic worm therapy in human autoimmune diseases. - Chhabra, S., Chang, S. C., Nguyen, H. M., Huq, R., Tanner, M. R., Londono, L. M., Estrada, R., Dhawan, V., Chauhan, S., Upadhyay, S. K., Gindin, M., Hotez, P. J., Valenzuela, J. G., Mohanty, B., Swarbrick, J. D., Wulff, H., Iadonato, S. P., Gutman, G. A., Beeton, C., Pennington, M. W., Norton, R. S., Chandy, K. G. Kv1.3 channelblocking immunomodulatory peptides from parasitic worms: implications for autoimmune diseases.
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- 2014
9. Alternative polyadenylation signals in the 3′ non-coding region of a voltage-gated potassium channel gene are major determinants of mRNA isoform expression
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Bert L. Semler, George A. Gutman, Gwendolyn M. Jang, Brian S. Tanaka, and Alan L. Goldin
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Gene isoform ,Polyadenylation ,Xenopus ,Molecular Sequence Data ,Cleavage and polyadenylation specificity factor ,Biology ,Article ,Mice ,Genetics ,Animals ,Humans ,Protein Isoforms ,Coding region ,RNA, Messenger ,3' Untranslated Regions ,Cells, Cultured ,Regulation of gene expression ,Messenger RNA ,Base Sequence ,Three prime untranslated region ,Alternative splicing ,General Medicine ,Molecular biology ,Rats ,Kv1.4 Potassium Channel ,HeLa Cells - Abstract
We investigated the role of the 3' non-coding region of a mouse voltage-gated potassium channel mRNA (mKv1.4 mRNA) in post-transcriptional regulation of gene expression. In contrast to an earlier report from studies carried out in Xenopus oocytes, we found that 3' non-coding region sequences of mKv1.4 mRNAs did not significantly affect expression of a heterologous reporter RNA in vitro or in mammalian cells/cell lines. Instead, our data revealed a possible role for alternative polyadenylation mediated by distinct determinants approximately 0.2 kb and approximately 1.2 kb downstream of the Kv1.4 coding region. The use of the downstream polyadenylation signal correlated with the synthesis of a larger Kv1.4 mRNA isoform that was more abundantly expressed than the smaller mRNA species, whose expression was regulated by the upstream polyadenylation signal. Our results suggest that the relative strengths of the polyadenylation signals are major determinants of overall Kv1.4 mRNA abundance in cells.
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- 2008
10. Kv1.3 channels are a therapeutic target for T cell-mediated autoimmune diseases
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Heike Wulff, Christine Beeton, Jamshid Tehranzadeh, Nathan Standifer, Stephen M Griffey, Werner W. Roeck, Christine J. LeeHealey, Philippe Azam, Brian S. Andrews, Alexandra Grino, Debra Counts, K. George Chandy, George A. Gutman, Kimber L. Stanhope, Ananthakrishnan Sankaranarayanan, Ping H. Wang, Katherine M. Mullen, Daniel Homerick, Pavel I. Zimin, Peter J. Havel, Michael W. Pennington, Aaron Kolski-Andreaco, Eric Wei, Peter A. Calabresi, Gerald T. Nepom, and Hans Guenther Knaus
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rheumatoid arthritis ,type-1 diabetes mellitus ,Patch-Clamp Techniques ,T-Lymphocytes ,Pancreatitis-Associated Proteins ,Arthritis, Rheumatoid ,Interleukin 21 ,Rheumatoid ,Receptors ,2.1 Biological and endogenous factors ,Medicine ,Cytotoxic T cell ,IL-2 receptor ,Aetiology ,Kv1.3 Potassium Channel ,Multidisciplinary ,Biological Sciences ,Natural killer T cell ,Electrophysiology ,medicine.anatomical_structure ,Chemokine ,5.1 Pharmaceuticals ,Interleukin 12 ,Receptors, Chemokine ,Female ,Development of treatments and therapeutic interventions ,Type 1 ,Receptors, CCR7 ,T cell ,Autoimmune Disease ,Antigen ,effector memory T cell ,MD Multidisciplinary ,Diabetes Mellitus ,Potassium Channel Blockers ,Animals ,Humans ,Animal ,business.industry ,Arthritis ,Inflammatory and immune system ,Rats ,Disease Models, Animal ,Diabetes Mellitus, Type 1 ,CTLA-4 ,Disease Models ,Immunology ,business ,CCR7 - Abstract
Autoreactive memory T lymphocytes are implicated in the pathogenesis of autoimmune diseases. Here we demonstrate that disease-associated autoreactive T cells from patients with type-1 diabetes mellitus or rheumatoid arthritis (RA) are mainly CD4+CCR7−CD45RA−effector memory T cells (TEMcells) with elevated Kv1.3 potassium channel expression. In contrast, T cells with other antigen specificities from these patients, or autoreactive T cells from healthy individuals and disease controls, express low levels of Kv1.3 and are predominantly naïve or central-memory (TCM) cells. In TEMcells, Kv1.3 traffics to the immunological synapse during antigen presentation where it colocalizes with Kvβ2, SAP97, ZIP, p56lck, and CD4. Although Kv1.3 inhibitors [ShK(L5)-amide (SL5) and PAP1] do not prevent immunological synapse formation, they suppress Ca2+-signaling, cytokine production, and proliferation of autoantigen-specific TEMcells at pharmacologically relevant concentrations while sparing other classes of T cells. Kv1.3 inhibitors ameliorate pristane-induced arthritis in rats and reduce the incidence of experimental autoimmune diabetes in diabetes-prone (DP-BB/W) rats. Repeated dosing with Kv1.3 inhibitors in rats has not revealed systemic toxicity. Further development of Kv1.3 blockers for autoimmune disease therapy is warranted.
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- 2006
11. Kv1.3 Potassium Channel: Physiology, Pharmacology and Therapeutic Indications
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Michael W. Pennington, George A. Gutman, Heike Wulff, Christine Beeton, K. George Chandy, and Peter A. Calabresi
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Chemistry ,Physiology ,Pharmacology ,Potassium channel - Published
- 2006
12. International Union of Pharmacology. LII. Nomenclature and Molecular Relationships of Calcium-Activated Potassium Channels
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George A. Gutman, Heike Wulff, Richard W. Aldrich, K. George Chandy, Aguan Wei, and Stephan Grissmer
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Pharmacology ,Inward-rectifier potassium ion channel ,Chemistry ,Voltage-gated potassium channel ,Potassium channel ,Potassium Channels, Calcium-Activated ,Structure-Activity Relationship ,KCNN4 ,Terminology as Topic ,Animals ,Humans ,Molecular Medicine ,Shaker ,Gene ,Nomenclature ,Ion channel - Abstract
Potassium-selective channels are the largest and most diverse group of ion channels, represented by some 70 known loci in the mammalian genome. The first cloned potassium channel gene was the Drosophila voltage-gated shaker channel, and this was rapidly followed by the identification of other
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- 2005
13. Structurally Distinct Elements Mediate Internal Ribosome Entry within the 5′-Noncoding Region of a Voltage-gated Potassium Channel mRNA
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Lily T. Hoang, George A. Gutman, Gwendolyn M. Jang, Louis Leong, Ping H. Wang, and Bert L. Semler
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5' Flanking Region ,RNase P ,5' flanking region ,Biology ,Biochemistry ,Ribosome ,Cell Line ,Mice ,Ribonucleases ,Protein biosynthesis ,Animals ,Humans ,RNA, Messenger ,Promoter Regions, Genetic ,Molecular Biology ,Messenger RNA ,RNA ,Cell Biology ,Voltage-gated potassium channel ,Molecular biology ,Cell biology ,Gene Expression Regulation ,Polypyrimidine tract ,Potassium Channels, Voltage-Gated ,Protein Biosynthesis ,Mutation ,Kv1.4 Potassium Channel ,Nucleic Acid Conformation ,Ribosomes - Abstract
The approximately 1.2-kb 5'-noncoding region (5'-NCR) of mRNA species encoding mouse Kv1.4, a member of the Shaker-related subfamily of voltage-gated potassium channels, was shown to mediate internal ribosome entry in cells derived from brain, heart, and skeletal muscle, tissues known to express Kv1.4 mRNA species. We also show that the upstream approximately 1.0 kb and the downstream approximately 0.2 kb of the Kv1.4 5'-NCR independently mediated internal ribosome entry; however, separately, these sequences were less efficient in mediating internal ribosome entry than when together in the complete (and contiguous) 5'-NCR. Using enzymatic structure probing, the 3'-most approximately 0.2 kb was predicted to form three distinct stem-loop structures (stem-loops X, Y, and Z) and two defined single-stranded regions (loops Psi and Omega) in the presence and absence of the upstream approximately 1.0 kb. Although the systematic deletion of sequences within the 3'-most approximately 0.2 kb resulted in distinct changes in expression, enzymatic structure probing indicated that local RNA folding was not completely altered. Structure probing analysis strongly suggested an interaction between stem-loop X and a downstream polypyrimidine tract; however, opposing changes in activity were observed when sequences within these two regions were independently deleted. Moreover, deletions correlating with positive as well as negative changes in expression altered RNase cleavage within stem-loop X, indicating that this structure may be an integral element. Therefore, these findings indicate that Kv1.4 expression is mediated through a complex interplay between many distinct RNA regions.
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- 2004
14. International Union of Pharmacology. XXXIX. Compendium of Voltage-Gated Ion Channels: Sodium Channels
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Michel Lazdunski, John P. Adelman, Gary V. Desir, Jonathan Robbins, Stephan Grissmer, Heike Wulff, Gail A. Robertson, Manuel Covarriubias, Douglas A. Bayliss, David McKinnon, Bernardo Rudy, Henry A. Lester, Andreas Karschin, Aguan Wei, David E. Clapham, Kiyoshi Furuichi, Maria L. Garcia, Randy S. Wymore, Barry Ganetzky, K. George Chandy, Michael C. Sanguinetti, Lily Yeh Jan, Jayashree Aiyar, Yoshihisa Kurachi, Walter Stuehmer, Florian Lesage, Colin G. Nichols, Ita O'Kelly, Sabina Kuperschmidt, Michael M. Tamkun, George A. Gutman, Susumu Seino, Carol A. Vandenberg, and Donghee Kim
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Pharmacology ,Voltage-gated ion channel ,Chemistry ,Terminology as Topic ,Molecular Medicine ,Ion Channel Gating ,Molecular Biology ,Sodium Channels ,Compendium - Abstract
This summary article presents an overview of the molecular relationships among the voltage-gated sodium channels and a standard nomenclature for them, which is derived from the IUPHAR Compendium of Voltage-Gated Ion Channels. The complete Compendium, including data tables for each member of the sodium channel family can be found athttp://www.iuphar-db.org/iuphar-ic/.
- Published
- 2003
15. A Novel Fluorescent Toxin to Detect and Investigate Kv1.3 Channel Up-regulation in Chronically Activated T Lymphocytes
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Steve Botsko, George Crossley, Michael W. Pennington, K. George Chandy, George A. Gutman, Christine Beeton, Satendra Singh, Heike Wulff, and Michael D. Cahalan
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Models, Molecular ,Magnetic Resonance Spectroscopy ,Potassium Channels ,Time Factors ,T-Lymphocytes ,Biochemistry ,Mice ,Cytotoxic T cell ,Tissue Distribution ,Lymphocytes ,IL-2 receptor ,Amino Acids ,Protein Kinase C ,Kv1.3 Potassium Channel ,biology ,medicine.diagnostic_test ,Flow Cytometry ,Fluoresceins ,Up-Regulation ,Electrophysiology ,medicine.anatomical_structure ,Potassium Channels, Voltage-Gated ,biological phenomena, cell phenomena, and immunity ,T cell ,Guinea Pigs ,Biotin ,complex mixtures ,Cell Line ,Flow cytometry ,Cnidarian Venoms ,Antigen ,medicine ,Animals ,Humans ,natural sciences ,Antigens ,Molecular Biology ,Fluorescent Dyes ,Cell Nucleus ,CD40 ,Dose-Response Relationship, Drug ,Voltage-gated ion channel ,urogenital system ,Cell Biology ,Molecular biology ,Rats ,Kinetics ,nervous system ,Rats, Inbred Lew ,Cell culture ,biology.protein ,Calcium ,Peptides - Abstract
T lymphocytes with unusually high expression of the voltage-gated Kv1.3 channel (Kv1.3(high) cells) have been implicated in the pathogenesis of experimental autoimmune encephalomyelitis, an animal model for multiple sclerosis. We have developed a fluoresceinated analog of ShK (ShK-F6CA), the most potent known inhibitor of Kv1.3, for detection of Kv1.3(high) cells by flow cytometry. ShK-F6CA blocked Kv1.3 at picomolar concentrations with a Hill coefficient of 1 and exhibited >80-fold specificity for Kv1.3 over Kv1.1 and other K(V) channels. In flow cytometry experiments, ShK-F6CA specifically stained Kv1.3-expressing cells with a detection limit of approximately 600 channels per cell. Rat and human T cells that had been repeatedly stimulated 7-10 times with antigen were readily distinguished on the basis of their high levels of Kv1.3 channels (>600 channels/cell) and ShK-F6CA staining from resting T cells or cells that had undergone 1-3 rounds of activation. Functional Kv1.3 expression levels increased substantially in a myelin-specific rat T cell line following myelin antigen stimulation, peaking at 15-20 h and then declining to baseline over the next 7 days, in parallel with the acquisition and loss of encephalitogenicity. Both calcium- and protein kinase C-dependent pathways were required for the antigen-induced Kv1.3 up-regulation. ShK-F6CA might be useful for rapid and quantitative detection of Kv1.3(high) expressing cells in normal and diseased tissues, and to visualize the distribution of functional channels in intact cells.
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- 2003
16. Delineation of the Clotrimazole/TRAM-34 Binding Site on the Intermediate Conductance Calcium-activated Potassium Channel, IKCa1
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Heike Wulff, George A. Gutman, K. George Chandy, and Michael D. Cahalan
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Models, Molecular ,Cytoplasm ,Potassium Channels ,Charybdotoxin ,Protein Conformation ,Stereochemistry ,Molecular Sequence Data ,Biochemistry ,Hydrophobic effect ,chemistry.chemical_compound ,Humans ,Moiety ,Amino Acid Sequence ,Clotrimazole ,Binding site ,Molecular Biology ,Binding Sites ,Tetraethylammonium ,Sequence Homology, Amino Acid ,Conductance ,Cell Biology ,Intermediate-Conductance Calcium-Activated Potassium Channels ,Potassium channel ,Calcium-activated potassium channel ,chemistry ,Pyrazoles ,Calcium ,Calcium Channels - Abstract
Selective and potent triarylmethane blockers of the intermediate conductance calcium-activated potassium channel, IKCa1, have therapeutic use in sickle cell disease and secretory diarrhea and as immunosuppressants. Clotrimazole, a membrane-permeant triarylmethane, blocked IKCa1 with equal affinity when applied externally or internally, whereas a membrane-impermeant derivative TRAM-30 blocked the channel only when applied to the cytoplasmic side, indicating an internal drug-binding site. Introduction of the S5-P-S6 region of the triarylmethane-insensitive small conductance calcium-activated potassium channel SKCa3 into IKCa1 rendered the channel resistant to triarylmethanes. Replacement of Thr(250) or Val(275) in IKCa1 with the corresponding SKCa3 residues selectively abolished triarylmethane sensitivity without affecting the affinity of the channel for tetraethylammonium, charybdotoxin, and nifedipine. Introduction of these two residues into SKCa3 rendered the channel sensitive to triarylmethanes. In a molecular model of IKCa1, Thr(250) and Val(275) line a water-filled cavity just below the selectivity filter. Structure-activity studies suggest that the side chain methyl groups of Thr(250) and Val(275) may lock the triarylmethanes in place via hydrophobic interactions with the pi-electron clouds of the phenyl rings. The heterocyclic moiety may project into the selectivity filter and obstruct the ion-conducting pathway from the inside.
- Published
- 2001
17. Up-regulation of the IKCa1 Potassium Channel during T-cell Activation
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Amber L. Neben, Mark J. Miller, K. George Chandy, Sanjiv Ghanshani, Heike Rohm, Michael D. Cahalan, Heike Wulff, and George A. Gutman
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T cell ,Margatoxin ,Cell ,Cell Biology ,Biology ,Biochemistry ,Potassium channel ,Cell biology ,AP-1 transcription factor ,medicine.anatomical_structure ,Downregulation and upregulation ,medicine ,Receptor ,Molecular Biology ,Protein kinase C - Abstract
We used whole cell recording to evaluate functional expression of the intermediate conductance Ca2+-activated K+ channel,IKCa1, in response to various mitogenic stimuli. One to two days following engagement of T-cell receptors to trigger both PKC- and Ca2+-dependent events, IKCa1expression increased from an average of 8 to 300–800 channels/cell. Selective stimulation of the PKC pathway resulted in equivalent up-regulation, whereas a calcium ionophore was relatively ineffective. Enhancement in IKCa1 mRNA levels paralleled the increased channel number. The genomic organization ofIKCa1, SKCa2, and SKCa3 were defined, and IKCa and SKCa genes were found to have a remarkably similar intron-exon structure. Mitogens enhancedIKCa1 promoter activity proportional to the increase inIKCa1 mRNA, suggesting that transcriptional mechanisms underlie channel up-regulation. Mutation of motifs for AP1 and Ikaros-2 in the promoter abolished this induction. Selective Kv1.3inhibitors ShK-Dap22, margatoxin, and correolide suppressed mitogenesis of resting T-cells but not preactivated T-cells with up-regulated IKCa1 channel expression. Selectively blockingIKCa1 channels with clotrimazole or TRAM-34 suppressed mitogenesis of preactivated lymphocytes, whereas resting T-cells were less sensitive. Thus, Kv1.3 channels are essential for activation of quiescent cells, but signaling through the PKC pathway enhances expression of IKCa1 channels that are required for continued proliferation.
- Published
- 2000
18. Lack of linkage or association between schizophrenia and the polymorphic trinucleotide repeat within the KCNN3 gene on chromosome 1q21
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Corinne Gehrig, Stylianos E. Antonarakis, J. Jay Gargus, Virginia K. Lasseter, Haig H. Kazazian, K G Chandy, Emmanuelle Fantino, David E. Housman, A. E. Pulver, George A. Gutman, Jean-Louis Blouin, Gerald Nestadt, K. Kalman, and Uppala Radhakrishna
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Genetics ,Candidate gene ,Genetic linkage ,Genetic marker ,mental disorders ,Genotype ,Locus (genetics) ,Allele ,Biology ,Trinucleotide repeat expansion ,Gene ,Genetics (clinical) - Abstract
To determine the importance of a candidate gene KCNN3 (formerly named hSKCa3) in the susceptibility to schizophrenia, we have studied the genotypes of a (CAG)n polymorphism within this gene in the DNAs of the members of 54 multiplex families with this disease. Parametric and nonparametric linkage analysis did not provide evidence for linkage between KCNN3 (that we mapped to chromosome 1q21) and schizophrenia. Furthermore, we observed no difference in the distribution of the (CAG)n alleles between affected and normal individuals. These results do not support the hypothesis that larger KCNN3 alleles are preferentially associated with schizophrenia [Chandy et al. 1998 Mol Psychiatr 3:32-37] in individuals from multiply affected families.
- Published
- 1999
19. UK-78,282, a novel piperidine compound that potently blocks the Kv1.3 voltage-gated potassium channel and inhibits human T cell activation
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John Charles Kath, Kimberly A. Verdries, Kevin Koch, Stephan Grissmer, Angela Nguyen, Paul C. Canniff, Ann C. Cunningham, Robert J. Mather, Matthew J. Bruns, Douglas C. Hanson, E. Edward Mena, K. George Chandy, Michael D. Cahalan, Carol B. Donovan, Heiko Rauer, Burgess Laurence E, George A. Gutman, and James P. Rizzi
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Pharmacology ,Membrane potential ,Tetraethylammonium ,Charybdotoxin ,Stereochemistry ,Potassium channel blocker ,Voltage-gated potassium channel ,Potassium channel ,SK channel ,chemistry.chemical_compound ,chemistry ,medicine ,Channel blocker ,medicine.drug - Abstract
UK-78,282, a novel piperidine blocker of the T lymphocyte voltage-gated K+ channel, Kv1.3, was discovered by screening a large compound file using a high-throughput 86Rb efflux assay. This compound blocks Kv1.3 with a IC50 of ∼200 nM and 1 : 1 stoichiometry. A closely related compound, CP-190,325, containing a benzyl moiety in place of the benzhydryl in UK-78,282, is significantly less potent. Three lines of evidence indicate that UK-78,282 inhibits Kv1.3 in a use-dependent manner by preferentially blocking and binding to the C-type inactivated state of the channel. Increasing the fraction of inactivated channels by holding the membrane potential at −50 mV enhances the channel's sensitivity to UK-78,282. Decreasing the number of inactivated channels by exposure to ∼160 mM external K+ decreases the sensitivity to UK-78,282. Mutations that alter the rate of C-type inactivation also change the channel's sensitivity to UK-78,282 and there is a direct correlation between τh and IC50 values. Competition experiments suggest that UK-78,282 binds to residues at the inner surface of the channel overlapping the site of action of verapamil. Internal tetraethylammonium and external charybdotoxin do not compete UK-78,282's action on the channel. UK-78,282 displays marked selectivity for Kv1.3 over several other closely related K+ channels, the only exception being the rapidly inactivating voltage-gated K+ channel, Kv1.4. UK-78,282 effectively suppresses human T-lymphocyte activation. British Journal of Pharmacology (1999) 126, 1707–1716; doi:10.1038/sj.bjp.0702480
- Published
- 1999
20. ShK-Dap22, a Potent Kv1.3-specific Immunosuppressive Polypeptide
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Heiko Rauer, K. Kalman, Kathy Paschetto, Angela Nguyen, Edward P. Christian, Michael D. Cahalan, George A. Gutman, William R. Kem, Raymond S. Norton, Michael W. Pennington, V.M. Mahnir, K. George Chandy, Mark D. Lanigan, and Stephan Grissmer
- Subjects
Male ,Models, Molecular ,Magnetic Resonance Spectroscopy ,Potassium Channels ,T-Lymphocytes ,Molecular Sequence Data ,Mutant ,Peptide ,Pharmacology ,medicine.disease_cause ,Biochemistry ,Protein Structure, Secondary ,Cell Line ,Mice ,medicine ,Animals ,Humans ,Amino Acid Sequence ,Molecular Biology ,chemistry.chemical_classification ,Kv1.3 Potassium Channel ,Toxin ,Cell Biology ,Recombinant Proteins ,In vitro ,Potassium channel ,Amino acid ,chemistry ,Potassium Channels, Voltage-Gated ,Docking (molecular) ,Peptides ,Immunosuppressive Agents ,Potassium Channel Binding - Abstract
The voltage-gated potassium channel in T lymphocytes, Kv1.3, is an important molecular target for immunosuppressive agents. A structurally defined polypeptide, ShK, from the sea anemone Stichodactyla helianthus inhibited Kv1.3 potently and also blocked Kv1.1, Kv1.4, and Kv1.6 at subnanomolar concentrations. Using mutant cycle analysis in conjunction with complementary mutagenesis of ShK and Kv1.3, and utilizing the structure of ShK, we determined a likely docking configuration for this peptide in the channel. Based upon this topological information, we replaced the critical Lys22 in ShK with the positively charged, non-natural amino acid diaminopropionic acid (ShK-Dap22) and generated a highly selective and potent blocker of the T-lymphocyte channel. ShK-Dap22, at subnanomolar concentrations, suppressed anti-CD3 induced human T-lymphocyte [3H]thymidine incorporation in vitro. Toxicity with this mutant peptide was low in a rodent model, with a median paralytic dose of approximately 200 mg/kg body weight following intravenous administration. The overall structure of ShK-Dap22 in solution, as determined from NMR data, is similar to that of native ShK toxin, but there are some differences in the residues involved in potassium channel binding. Based on these results, we propose that ShK-Dap22 or a structural analogue may have use as an immunosuppressant for the prevention of graft rejection and for the treatment of autoimmune diseases.
- Published
- 1998
21. Transmission Disequilibrium Analysis of a Triplet Repeat within thehKCa3Gene Using Family Trios with Schizophrenia
- Author
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A. T. Bruinvels, Emmanuelle Fantino, K G Chandy, J. Jay Gargus, K. Kalman, George A. Gutman, E. Dawson, Xun Hu, RM Murray, Xiehe Liu, David A. Collier, Tao Li, Pak C. Sham, and B. Freeman
- Subjects
Adult ,Male ,Risk ,China ,Psychosis ,Potassium Channels ,Adolescent ,Genotype ,Small-Conductance Calcium-Activated Potassium Channels ,Molecular Sequence Data ,Disequilibrium ,Biophysics ,Locus (genetics) ,Biology ,Biochemistry ,Linkage Disequilibrium ,Potassium Channels, Calcium-Activated ,Trinucleotide Repeats ,mental disorders ,medicine ,Humans ,Allele ,Molecular Biology ,Gene ,Alleles ,Aged ,Genetics ,Haplotype ,Chromosome Mapping ,Cell Biology ,Middle Aged ,Polyglutamine tract ,medicine.disease ,Haplotypes ,Chromosomes, Human, Pair 1 ,Multiple comparisons problem ,Schizophrenia ,Female ,medicine.symptom - Abstract
hKCa3 is a neuronal small conductance calcium-activated potassium channel which contains a polyglutamine tract, encoded by a polymorphic CAG repeat in the gene. Since an association between longer alleles of the CAG repeat and schizophrenia has been reported, we performed haplotype-based haplotype relative risk (HHRR) and transmission disequilibrium (TDT) in 97 family trios with schizophrenia from SW China. We found no evidence for an excess of longer CAG repeats in the patients, and the ETDT test was not significant for either allele-wise (P = 0.31) or genotype-wise analysis (P = 0.18). However, there was a deficit of transmission of the (CAG) 20 repeat allele to affected offspring when this allele was considered individually by TDT (P = 0.012; not corrected for multiple testing). These data do not support a role for larger alleles at the hKCa3 locus in psychosis in Chinese subjects.
- Published
- 1998
22. Further support for an association between a polymorphic CAG repeat in the hKCa3 gene and schizophrenia
- Author
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Timothy Bowen, Kieran C. Murphy, Julie Williams, M. Y. Gray, George A. Gutman, Peter McGuffin, Carol Guy, Lesley Jones, Emmanuelle Fantino, J. Jay Gargus, Geraldine McCarthy, Gillian Spurlock, Rebecca Sanders, Michael John Owen, K. Kalman, Alastair G. Cardno, Michael Conlon O'Donovan, Nigel Williams, Nicholas John Craddock, and K G Chandy
- Subjects
Male ,Proband ,Psychosis ,Candidate gene ,Potassium Channels ,Genotype ,Biology ,Genetic determinism ,Cellular and Molecular Neuroscience ,Trinucleotide Repeats ,medicine ,Humans ,Allele ,Molecular Biology ,Gene ,Alleles ,Genetics ,Polymorphism, Genetic ,Case-control study ,Middle Aged ,medicine.disease ,Psychiatry and Mental health ,Case-Control Studies ,Schizophrenia ,Female ,Trinucleotide repeat expansion - Abstract
A recent study has suggested that a polymorphism in the hKCa3 potassium channel may be associated with raised susceptibility to schizophrenia. Despite its modest statistical significance, the study is intriguing for two reasons. First, hKCa3 contains a polymorphic CAG repeat in its coding sequence, with large repeats more common in schizophrenics compared with controls. This is interesting in view of several repeat expansion detection (RED) studies that have reported an excess of large CAG repeats in psychotic probands. Second, the hKCa3 gene is a functional candidate gene because studies of antipsychotic and psychotogenic compounds suggest that glutamatergic systems modulated by SKCa channels may be important in schizophrenia pathogenesis. In the light of the above, we have tested the hypothesis of an association between schizophrenia and the hKCa3 CAG repeat polymorphism using a case control study design. Under the same model of analysis as the earlier study, schizophrenic probands had a higher frequency of alleles with greater than 19 repeats than controls (chi 2 = 2.820, P = 0.047, 1-tail). Our data therefore provide modest support for the hypothesis that polymorphism in the hKCa3 gene may contribute to susceptibility to schizophrenia.
- Published
- 1998
23. Genomic Organization, Chromosomal Localization, Tissue Distribution, and Biophysical Characterization of a Novel MammalianShaker-related Voltage-gated Potassium Channel, Kv1.7
- Author
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Harvey W. Mohrenweiser, Carolyn M. Hustad, Grischa Chandy, K. George Chandy, George A. Gutman, B. F. Brandriff, K. Kalman, Michael D. Cahalan, Iain D. Dukes, Julie Tseng-Crank, Nancy A. Jenkins, Neal G. Copeland, and Angela Nguyen
- Subjects
Potassium Channels ,Charybdotoxin ,Molecular Sequence Data ,Neurotoxins ,Kaliotoxin ,Mice, Inbred Strains ,Biology ,complex mixtures ,Biochemistry ,Chromosomes ,Islets of Langerhans ,Mice ,chemistry.chemical_compound ,Animals ,Humans ,Coding region ,natural sciences ,Amino Acid Sequence ,Northern blot ,Cloning, Molecular ,Molecular Biology ,Gene ,In Situ Hybridization ,Phylogeny ,Chromosome 7 (human) ,Base Sequence ,Gene map ,urogenital system ,Chromosome Mapping ,Sequence Analysis, DNA ,Cell Biology ,Voltage-gated potassium channel ,Molecular biology ,Electrophysiology ,nervous system ,chemistry ,Shaker Superfamily of Potassium Channels ,biological phenomena, cell phenomena, and immunity ,Ion Channel Gating - Abstract
We report the isolation of a novel mouse voltage-gated Shaker-related K+ channel gene, Kv1.7 (Kcna7/KCNA7). Unlike other known Kv1 family genes that have intronless coding regions, the protein-coding region of Kv1.7 is interrupted by a 1.9-kilobase pair intron. The Kv1.7 gene and the related Kv3.3 (Kcnc3/KCNC3) gene map to mouse chromosome 7 and human chromosome 19q13.3, a region that has been suggested to contain a diabetic susceptibility locus. The mouse Kv1.7 channel is voltage-dependent and rapidly inactivating, exhibits cumulative inactivation, and has a single channel conductance of 21 pS. It is potently blocked by noxiustoxin and stichodactylatoxin, and is insensitive to tetraethylammonium, kaliotoxin, and charybdotoxin. Northern blot analysis reveals approximately 3-kilobase pair Kv1.7 transcripts in mouse heart and skeletal muscle. In situ hybridization demonstrates the presence of Kv1.7 in mouse pancreatic islet cells. Kv1.7 was also isolated from mouse brain and hamster insulinoma cells by polymerase chain reaction.
- Published
- 1998
24. Isolation of a novel potassium channel gene hSKCa3 containing a polymorphic CAG repeat: a candidate for schizophrenia and bipolar disorder?
- Author
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K. Kalman, Emmanuelle Fantino, TH Ho, Deborah J. Morris-Rosendahl, Rohan Ganguli, George A. Gutman, Oliver H. Wittekindt, Marc-Antoine Crocq, KG Chandy, LL Tong, Nimgaonkar, and J. Jay Gargus
- Subjects
Psychosis ,Bipolar Disorder ,Potassium Channels ,Small-Conductance Calcium-Activated Potassium Channels ,Molecular Sequence Data ,Locus (genetics) ,Genetic determinism ,Cellular and Molecular Neuroscience ,Trinucleotide Repeats ,mental disorders ,medicine ,Humans ,Amino Acid Sequence ,Bipolar disorder ,Allele ,Repeated sequence ,Molecular Biology ,Gene ,Allele frequency ,Alleles ,Neurons ,Genetics ,Polymorphism, Genetic ,Sequence Homology, Amino Acid ,Neuropeptides ,Brain ,medicine.disease ,Psychiatry and Mental health ,Schizophrenia ,Psychology ,Sequence Alignment - Abstract
Many human hereditary neurodegenerative diseases are caused by expanded CAG repeats, and anonymous CAG expansions have also been described in schizophrenia and bipolar disorder. We have isolated and sequenced a novel human cDNA encoding a neuronal, small conductance calcium-activated potassium channel (hSKCa3) that contains two arrays of CAG trinucleotide repeats. The second CAG repeat in hSKCa3 is highly polymorphic in control individuals, with alleles ranging in size from 12 to 28 repeats. The overall allele frequency distribution is significantly different in patients with schizophrenia compared to ethnically matched controls (Wilcoxon Rank Sum test, P = 0.024), with CAG repeats longer than the modal value being over-represented in patients (Fisher Exact test, P = 0.0035). A similar, non-significant, trend is seen for patients with bipolar disorder. These results provide evidence for a possible association between longer alleles in the hSKCa3 gene and both of these neuropsychiatric diseases, and emphasize the need for more extensive studies of this new gene. Small conductance calcium-activated K+ channels play a critical role in determining the firing pattern of neurons. These polyglutamine repeats may modulate hSKCa3 channel function and neuronal excitability, and thereby increase disease risk when combined with other genetic and environmental effects.
- Published
- 1998
25. Structural and Biochemical Features of the Kv1.3 Potassium Channel: An Aid to Guided Drug Design
- Author
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Jayashree Aiyar, George A. Gutman, Michael Strong, and George K. Chandy
- Subjects
Drug ,Protein structure ,Biochemistry ,Physiology ,Chemistry ,media_common.quotation_subject ,Protein crystallization ,Potassium channel ,media_common - Abstract
The Kv1.3 potassium channel in T lymphocytes plays a major role in mitogen-induced activation and is widely recognized as a potential therapeutic target for immunosuppressive agents. Availability of s
- Published
- 1997
26. Characterization of the Transcription Unit of Mouse Kv1.4, a Voltage-gated Potassium Channel Gene
- Author
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K. Kalman, Jayashree Aiyar, Deborah Negulescu, George A. Gutman, Randy S. Wymore, K. George Chandy, and Keith D. Kinoshita
- Subjects
Potassium Channels ,Transcription, Genetic ,Polyadenylation ,Restriction Mapping ,Biology ,Biochemistry ,Membrane Potentials ,Mice ,Xenopus laevis ,Exon ,Start codon ,Transcription (biology) ,Animals ,Coding region ,Tissue Distribution ,RNA, Messenger ,Promoter Regions, Genetic ,Molecular Biology ,Gene ,Messenger RNA ,Base Sequence ,3T3 Cells ,Cell Biology ,Molecular biology ,Stop codon ,Enhancer Elements, Genetic ,Gene Expression Regulation ,Genes ,Protein Biosynthesis ,Oocytes - Abstract
The mouse voltage-gated K+ channel gene, Kv1.4, is expressed in brain and heart as approximately 4.5- and approximately 3.5-kilobase (kb) transcripts. Both mRNAs begin at a common site 1338 bp upstream of the initiation codon, contain 3477 and 4411 nucleotides, respectively, and are encoded by two exons; exon 1 contains 0.5 kb of the 5'-noncoding region (NCR), while exon 2 encodes the remaining 0.8 kb of the 5'-NCR, the entire coding region (2 kb), and all of the 3'-NCR. The 3.5-kb transcript terminates at a polyadenylation signal 177 bp 3' of the stop codon, while the 4.5-kb mRNA utilizes a signal 94 bp farther downstream. Although the proteins generated from either transcript are identical, the two mRNAs are functionally different, the 3.5-kb transcript producing approximately 4-5-fold larger currents when expressed in Xenopus oocytes compared to the 4. 5-kb mRNA. The decreased expression of the longer transcript is due to the presence of five ATTTA repeats in the 3'-NCR which inhibit translation; such motifs have also been reported to destabilize the messages of many other genes and might therefore shorten the life of the 4.5-kb transcript during its natural expression. The Kv1.4 basal promoter is GC-rich, contains three SP1 repeats (CCGCCC, -65 to -35), lacks canonical TATAAA and GGCAATCT motifs, and has no apparent tissue specificity. One region enhances activity of this promoter. Thus, transcriptional and post-transcriptional regulation of mKv1.4, coupled with selective usage of the two alternate Kv1.4 mRNAs, may modulate the levels of functional Kv1.4 channels.
- Published
- 1996
27. Topology of the pore-region of a K+ channel revealed by the NMR-derived structures of scorpion toxins
- Author
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James E. Hall, George A. Gutman, Chao-lin Lee, Jayashree Aiyar, James G. Boyd, James P. Rizzi, Douglas C. Hanson, Jane M. Withka, Wen Lin, David H. Singleton, K. George Chandy, Mariella Simon, Brent A. Dethlefs, and Glenn C. Andrews
- Subjects
Models, Molecular ,Magnetic Resonance Spectroscopy ,Potassium Channels ,Charybdotoxin ,Neuroscience(all) ,Molecular Sequence Data ,Neurotoxins ,Kaliotoxin ,Scorpion Venoms ,Topology ,Maurotoxin ,chemistry.chemical_compound ,Electrochemistry ,Homology modeling ,Amino Acid Sequence ,Ion channel ,Topology (chemistry) ,Binding Sites ,Chemistry ,General Neuroscience ,Margatoxin ,Electric Conductivity ,Protein Structure, Tertiary ,Solutions ,Mutagenesis ,Vestibule ,Thermodynamics ,Ion Channel Gating - Abstract
The architecture of the pore-region of a voltage-gated K+ channel, Kv1.3, was probed using four high affinity scorpion toxins as molecular calipers. We established the structural relatedness of these toxins by solving the structures of kaliotoxin and margatoxin and comparing them with the published structure of charybdotoxin; a homology model of noxiustoxin was then developed. Complementary mutagenesis of Kv1.3 and these toxins, combined with electrostatic compliance and thermodynamic mutant cycle analyses, allowed us to identify multiple toxin-channel interactions. Our analyses reveal the existence of a shallow vestibule at the external entrance to the pore. This vestibule is approximately 28-32 A wide at its outer margin, approximately 28-34 A wide at its base, and approximately 4-8 A deep. The pore is 9-14 A wide at its external entrance and tapers to a width of 4-5 A at a depth of approximately 5-7 A from the vestibule. This structural information should directly aid in developing topological models of the pores of related ion channels and facilitate therapeutic drug design.
- Published
- 1995
- Full Text
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28. Transduction of a human RNA sequence by poliovirus
- Author
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Bert L. Semler, George A. Gutman, S Todd, and W A Charini
- Subjects
viruses ,Molecular Sequence Data ,Immunology ,Biology ,Transfection ,Cleavage (embryo) ,medicine.disease_cause ,Microbiology ,Ribosome ,Viral Proteins ,Transduction (genetics) ,Methionine ,Transduction, Genetic ,Virology ,RNA, Ribosomal, 28S ,Protein biosynthesis ,medicine ,Humans ,Amino Acid Sequence ,Peptide sequence ,Base Sequence ,Models, Genetic ,Poliovirus ,RNA ,Templates, Genetic ,Molecular biology ,Phenotype ,Protein Biosynthesis ,Insect Science ,Mutagenesis, Site-Directed ,RNA, Viral ,Ribosomes ,Research Article ,HeLa Cells - Abstract
Cells infected with poliovirus express a virally encoded polyprotein which undergoes self-mediated cleavage into structural and nonstructural viral proteins. Most of these cleavages are catalyzed by the 3C proteolytic domain of the polyprotein. Polyprotein synthesized in vitro from an RNA template containing a three-nucleotide insertion in 3C underwent proteolytic processing at all but one of the 3C-dependent cleavage sites. When transfected into HeLa cells, this RNA template displayed a lethal phenotype. We report here the isolation of two pseudorevertant progeny strains with restored protein-processing phenotypes, one of which appears to have arisen by transduction of a stretch of nucleotides from human 28S rRNA.
- Published
- 1994
29. Genomic Organization, Nucleotide Sequence, Biophysical Properties, and Localization of the Voltage-Gated K+ Channel Gene KCNA4/Kv1.4 to Mouse Chromosome 2/Human 11p14 and Mapping of KCNC1/Kv3.1 to Mouse 7/Human 11p14.3-p15.2 and KCNA1/Kv1.1 to Human 12p13
- Author
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Nancy A. Jenkins, George A. Gutman, Julie R. Korenberg, Christopher Coyne, K. George Chandy, Carolyn M. Hustad, Randy S. Wymore, Xiao Ning Chen, Neal G. Copeland, Jayashree Aiyar, and Keith D. Kinoshita
- Subjects
Genetics ,Chromosome 7 (human) ,Chromosomes, Human, Pair 12 ,Potassium Channels ,Base Sequence ,Chromosomes, Human, Pair 11 ,Molecular Sequence Data ,Nucleic acid sequence ,Intron ,Chromosome Mapping ,Locus (genetics) ,DNA ,Biology ,Molecular biology ,Mice ,Exon ,Animals ,Humans ,Coding region ,Ion Channel Gating ,Gene ,In Situ Hybridization, Fluorescence ,Genomic organization - Abstract
A genomic clone encoding the Shaker-related potassium channel gene, Kcna4/mKv1.4, was isolated from mice. Its coding region is contained in a single exon, encodes a protein of 654 amino acids, and shares approximately 91% nucleotide sequence identity with human KCNA4/hKv1.4. We show that 0.8 kb of the 5' noncoding region (NCR), the entire protein coding region (approximately 2.0 kb), and all of the known 3' NCR (approximately 1.1 kb) are contained within a single exon; the remaining 0.5 kb of the 5' NCR is separated from this exon by a 3.4-kb intron. The sequenced genomic region thus accounts for essentially all of the longest known transcript (4.5 kb), although the precise ends of this transcript have not been defined. The 3' NCR contains several ATTTA and ATTTG motifs that are thought to destabilize mRNAs, and these are also present in rat, bovine, and human Kcna4/Kv1.4 cDNAs. It also contains three conserved polyadenylation signals, alternate utilization of which could generate mRNAs of differing stabilities. The 5' NCR of Kcna4/mKv1.4 may also serve to regulate channel expression. This region is approximately 85% identical to KCNA4/hKv1.4 and contains eight consensus translation start sites [(G, A)NNATG] that, based on the 5'-3' scanning model, would lead to a lowering of translational efficiency. The shortest Kcna4/Kv1.4 transcript (2.4 kb) can contain at most 400 bp of NCR and should lack the 3' ATTTAs and most of the 5' ATGs; this transcript might therefore exhibit increased stability and translational efficiency. The Kcna4/mKv1.4 channel exhibited biophysical and pharmacological properties indistinguishable from its rat and human homologues. Kcna4/mKv1.4 lies on mouse chromosome 2, near the Fshb locus, and in humans on the proximal half of chromosome 11p14 near human FSHB. Another K+ channel gene, Kcnc1/mKv3.1, lies approximately 1.8 cM from the Myod-1 gene on mouse chromosome 7, and in situ hybridization localizes KCNC1/hKv3.1 to the homologous region on human chromosome 11p14.3-p15.2. A third gene, KCNA1/hKv1.1, was mapped to human 12p13.
- Published
- 1994
30. Nomenclature of mammalian voltage-dependent potassium channel genes
- Author
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George A. Gutman and K. George Chandy
- Subjects
KCNN4 ,Chemistry ,General Neuroscience ,Gene ,Nomenclature ,Potassium channel ,Voltage ,Cell biology - Published
- 1993
31. Physiological role, molecular structure and evolutionary relationships of voltage-gated potassium channels in T lymphocytes
- Author
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George A. Gutman, K. George Chandy, and Stephan Grissmer
- Subjects
Membrane potential ,Genetics ,General Neuroscience ,T cell ,Chromosome ,Voltage-gated potassium channel ,Biology ,Cell biology ,medicine.anatomical_structure ,Autoimmune Process ,medicine ,Molecule ,Gene ,Calcium signaling - Abstract
T lymphocytes display three distinct types of voltage-gated K + channels, types n, n′ and l, that are expressed in an activation- and development-dependent fashion. These channels regulate the membrane potential of T cells and thereby control the calcium signaling response necessary for lymphocyte activation. Abnormal over-expression of type l K + channels is a marker for a subset of CD4/CD8-negative T cells associated with autoimmune disorders, and may reflect the ability of these cells to trigger the autoimmune process. The types n and l K + channels are encoded by genes belonging to two distinct subfamilies, showing only 51% sequence identity at the nucleotide level; the Shaker-related Kv1.3 gene on human chromosome 1 encodes the type n K + channel, whereas the type l K + channel is the product of the Shaw-subfamily gene Kv3.1 on human chromosome 11. Drugs which block the Kv1.3 channel inhibit T cell activation, and might therefore serve as immunosuppressants for the prevention of graft rejection and treatment of T cell-mediated autoimmune diseases. Agents which block type l K + channels, on the other hand, could be used to treat autoimmune disorders in a highly specific manner by targeting a disease-relevant subset of T lymphocytes.
- Published
- 1993
32. The Shaw-related potassium channel gene, Kv3.1, on human chromosome 11, encodes the type l K+ channel in T cells
- Author
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John J. Wasmuth, George A. Gutman, Michael D. Cahalan, Brent A. Dethlefs, John Douglas Mcpherson, Sanjiv Ghanshani, K G Chandy, and Stephan Grissmer
- Subjects
Genetics ,Gene map ,T cell ,Cell Biology ,T lymphocyte ,Biology ,Biochemistry ,Molecular biology ,Potassium channel ,medicine.anatomical_structure ,medicine ,Cytotoxic T cell ,Chromosome 21 ,Molecular Biology ,CD8 ,Chromosome 12 - Abstract
T lymphocytes exhibit three distinct types of voltage-gated K+ channels, n, n', and l, that are distributed in the T cell lineage according to subset, as well as the cells' activation and developmental status. Type l K+ channels are found sparingly in cytotoxic T cells from normal mice and abundantly in a specific T cell subset (CD4- CD8- Thy1+) from mice with autoimmune disease. Here, we show that the mouse Kv3.1 gene, when expressed in Xenopus oocytes, encodes a channel with properties remarkably similar to those of the l-type channel. Kv3.1 transcripts were found in T cells isolated from the lymph nodes of MRL-lpr mice with systemic lupus erythematosus and in a human lymphoma cell line that also expresses the l channel phenotype. By these criteria, we conclude that Kv3.1 encodes the voltage-gated type l K+ channel in lymphocytes. The Kv3.1 gene maps to human chromosome 11; the related Kv1.1 and Kv3.2 genes are localized on human chromosome 12, while the IsK gene maps to human chromosome 21.
- Published
- 1992
33. IUPHAR-DB: the IUPHAR database of G protein-coupled receptors and ion channels
- Author
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Vincent Laudet, Peter Buneman, Stuart D. Greenhill, Mathew W. Wright, John A. Peters, Eliot H. Ohlstein, Joanna L. Sharman, Tom I. Bonner, Rebecca Hills, George A. Gutman, Donald R. Dunbar, Robert R. Ruffolo, Jean-Philippe Pin, Philippe Delagrange, David B. Searls, Steven M. Foord, Valerie A. Hale, Colin Dollery, Anthony P. Davenport, Michael Spedding, Richard R. Neubig, Richard W. Olsen, William A. Catterall, Martin Jones, Edward M. Rosser, Anthony J. Harmar, University of Edinburgh, School of Informatics, National Institute of Mental Health, Department of Pharmacology, University of Washington [Seattle], Clinical Pharmacology Unit, University of Cambridge [UK] (CAM)-Addenbrooke's Hospital, SERVIER, Management Division, Babson College, Research and Development, GlaxoSmithKline, University of California (UC), Institut de Génomique Fonctionnelle de Lyon (IGFL), École normale supérieure de Lyon (ENS de Lyon)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), University of Dundee, Institut de Génomique Fonctionnelle (IGF), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Wyeth, GlaxoSmithKline [Siena, Italy] (GSK), Wellcome Trust, University of California, Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-École normale supérieure - Lyon (ENS Lyon), and Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
BASE IUPHAR ,update ,[SDV]Life Sciences [q-bio] ,HUGO Gene Nomenclature Committee ,genome database ,subunits ,Ligands ,computer.software_genre ,Genome ,Ion Channels ,Receptors, G-Protein-Coupled ,information ,Mice ,0302 clinical medicine ,Drug Discovery ,Databases, Protein ,bioinformatique ,RÉCEPTEUR PROTÉINE ,Genetics ,0303 health sciences ,Database ,Drug discovery ,Life Sciences ,Articles ,3. Good health ,protéine ,Ligand-gated ion channel ,nomenclature ,UniProt ,international union ,Biology ,03 medical and health sciences ,Animals ,Humans ,[INFO]Computer Science [cs] ,gene ,Gene ,030304 developmental biology ,G protein-coupled receptor ,Sequence database ,génome ,gène ,protéine g ,Rats ,knowledgebase ,Protein Subunits ,BASE DE DONNÉES ,sequence database ,pharmacology ,computer ,030217 neurology & neurosurgery - Abstract
International audience; The IUPHAR database (IUPHAR-DB) integrates peer-reviewed pharmacological, chemical, genetic, functional and anatomical information on the 354 non-sensory G protein-coupled receptors (GPCRs), 71 ligand-gated ion channel subunits and 141 voltage-gated-like ion channel subunits encoded by the human, rat and mouse genomes. These genes represent the targets of approximately one-third of currently approved drugs and are a major focus of drug discovery and development programs in the pharmaceutical industry. IUPHAR-DB provides a comprehensive description of the genes and their functions, with information on protein structure and interactions, ligands, expression patterns, signaling mechanisms, functional assays and biologically important receptor variants (e.g. single nucleotide polymorphisms and splice variants). In addition, the phenotypes resulting from altered gene expression (e.g. in genetically altered animals or in human genetic disorders) are described. The content of the database is peer reviewed by members of the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR); the data are provided through manual curation of the primary literature by a network of over 60 subcommittees of NC-IUPHAR. Links to other bioinformatics resources, such as NCBI, Uniprot, HGNC and the rat and mouse genome databases are provided. IUPHAR-DB is freely available at http://www.iuphar-db.org.
- Published
- 2009
34. The sense of place in the immune system
- Author
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Michael D. Cahalan and George A. Gutman
- Subjects
Innate immune system ,Immunology ,Antigen presentation ,Lymphokine ,Thymus Gland ,Biology ,biochemical phenomena, metabolism, and nutrition ,Acquired immune system ,Hematopoietic Stem Cells ,Article ,Cell biology ,B-1 cell ,Immune system ,Cell Movement ,Immune System ,Lymph node stromal cell ,Immunology and Allergy ,bacteria ,Animals ,Humans ,Cell Lineage ,Lymph Nodes ,Lymphocytes ,Adult stem cell - Abstract
This series of reviews examines the effect of differing tissue environments on the activity and functional capacity of cells in the immune system. From their origins as hematopoietic stem cells, throughout their development and as mature cells, cells of the immune system find themselves in distinct and highly specialized niches, and contact with antigen or inflammatory signals changes their phenotype, activity and trafficking. Two-photon microscopy has provided the first direct observations of living cells and their activation choreography in the tissue environment and will no doubt continue to provide greater understanding of cellular dynamics and immune function.
- Published
- 2006
35. Targets and Therapeutic Properties of Venom Peptides
- Author
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Christine Beeton, K. George Chandy, and George A. Gutman
- Subjects
media_common.quotation_subject ,Large array ,Zoology ,Venom ,Anatomy ,Art ,media_common - Abstract
Venoms contain numerous peptides with a large array of biological activities. In this chapter we examine the potential therapeutic application of venom-derived peptides. Toads, snakes, and other venomous animals are well-known ingredients of witch potions, as extolled by Shakespeare in Macbeth, Act IV, Scene 1. The three witches Hellip; Round about the caldron go; In the poison'd entrails throw— Toad, that under cold stone, Days and nights has thirty-one Swelter'd venom sleeping got, Boil thou first i’ the charmed pot! Double, double, toil and trouble; Fire, burn; and caldron, bubble. Fillet of a fenny snake, In the caldron boil and bake; Eye of newt, and toe of frog, Wool of bat, and tongue of dog, Adder's fork, and blind-worm's sting, Lizard's leg, and howlet's wing— For a charm of powerful trouble, Like a hell-broth boil and bubble.
- Published
- 2006
36. International Union of Pharmacology. LIII. Nomenclature and molecular relationships of voltage-gated potassium channels
- Author
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George A. Gutman, K. George Chandy, Stephan Grissmer, Michel Lazdunski, David Mckinnon, Luis A. Pardo, Gail A. Robertson, Bernardo Rudy, Michael C. Sanguinetti, Walter Stühmer, and Xiaoliang Wang
- Subjects
Pharmacology ,Structure-Activity Relationship ,Potassium Channels, Voltage-Gated ,Terminology as Topic ,Molecular Medicine ,Animals ,Humans - Published
- 2005
37. Overview of molecular relationships in the voltage-gated ion channel superfamily
- Author
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Vladimir Yarov-Yarovoy, William A. Catterall, Frank H. Yu, and George A. Gutman
- Subjects
Pharmacology ,Voltage-gated ion channel ,Protein Conformation ,SUPERFAMILY ,Biology ,Biological Evolution ,Calcium in biology ,Ion Channels ,Cell biology ,Electrophysiology ,Multicellular organism ,Molecular Medicine ,Animals ,Humans ,Secretion ,Ion Channel Gating ,Hormone - Abstract
Complex multicellular organisms require rapid and accurate transmission of information among cells and tissues and tight coordination of distant functions. In vertebrates, electrical signals and the resulting intracellular calcium transients control contraction of muscle, secretion of hormones
- Published
- 2005
38. Enhanced neuronal excitability in the absence of neurodegeneration induces cerebellar ataxia
- Author
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Hans-Günther Knaus, Frank M. LaFerla, Vikram G. Shakkottai, George A. Gutman, Michael E. Barish, Claudia A. Sailer, K. George Chandy, Salvatore Oddo, and Chin Hua Chou
- Subjects
congenital, hereditary, and neonatal diseases and abnormalities ,Cerebellum ,medicine.medical_specialty ,Potassium Channels ,Ataxia ,Cerebellar Ataxia ,Recombinant Fusion Proteins ,Mice, Transgenic ,In Vitro Techniques ,Motor Activity ,Biology ,Audiology ,Deep cerebellar nuclei ,Neuroprotection ,Article ,SK channel ,Mice ,Purkinje Cells ,medicine ,Animals ,Humans ,Transgenes ,Promoter Regions, Genetic ,Neurons ,Cerebellar ataxia ,Neurodegeneration ,General Medicine ,medicine.disease ,Riluzole ,Electrophysiology ,medicine.anatomical_structure ,Apamin ,nervous system ,Cerebellar Nuclei ,Commentary ,medicine.symptom ,Neuroscience ,medicine.drug - Abstract
Cerebellar ataxia, a devastating neurological disease, may be initiated by hyperexcitability of deep cerebellar nuclei (DCN) secondary to loss of inhibitory input from Purkinje neurons that frequently degenerate in this disease. This mechanism predicts that intrinsic DCN hyperexcitability would cause ataxia in the absence of upstream Purkinje degeneration. We report the generation of a transgenic (Tg) model that supports this mechanism of disease initiation. Small-conductance calcium-activated potassium (SK) channels, regulators of firing frequency, were silenced in the CNS of Tg mice with the dominant-inhibitory construct SK3-1B-GFP. Transgene expression was restricted to the DCN within the cerebellum and was detectable beginning on postnatal day 10, concomitant with the onset of cerebellar ataxia. Neurodegeneration was not evident up to the sixth month of age. Recordings from Tg DCN neurons revealed loss of the apamin-sensitive after-hyperpolarization current (IAHP) and increased spontaneous firing through SK channel suppression, indicative of DCN hyperexcitability. Spike duration and other electrogenic conductance were unaffected. Thus, a purely electrical alteration is sufficient to cause cerebellar ataxia, and SK openers such as the neuroprotective agent riluzole may reduce neuronal hyperexcitability and have therapeutic value. This dominant-inhibitory strategy may help define the in vivo role of SK channels in other neuronal pathways.
- Published
- 2004
39. International Union of Pharmacology. XLI. Compendium of voltage-gated ion channels: potassium channels
- Author
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Gary V. Desir, I. T. A. O'kelly, David McKinnon, Kiyoshi Furuichi, Maria L. Garcia, Bernardo Rudy, Jonathan Robbins, Lily Yeh Jan, John P. Adelman, Jayashree Aiyar, David E. Clapham, Florian Lesage, Michel Lazdunski, Stephan Grissmer, Manuel Covarriubias, Randy S. Wymore, Heike Wulff, Gail A. Robertson, George A. Gutman, Michael C. Sanguinetti, Aguan Wei, Carol A. Vandenberg, Susumu Seino, Douglas A. Bayliss, Sabina Kuperschmidt, Michael M. Tamkun, Colin G. Nichols, Henry A. Lester, Walter Stuehmer, Barry Ganetzky, K. George Chandy, Yoshihisa Kurachi, Donghee Kim, and Andreas Karschin
- Subjects
Pharmacology ,Voltage-gated ion channel ,Chemistry ,Inward-rectifier potassium ion channel ,Potassium Channels, Voltage-Gated ,Terminology as Topic ,Molecular Medicine ,Compendium ,Potassium channel ,Phylogeny - Abstract
This summary article presents an overview of the molecular relationships among the voltage-gated potassium channels and a standard nomenclature for them, which is derived from the IUPHAR Compendium of Voltage-Gated Ion Channels.1 The complete Compendium, including data tables for each member of the potassium channel family can be found at http://www.iuphar-db.org/iuphar-ic/.
- Published
- 2003
40. SK3-1C, a dominant-negative suppressor of SKCa and IKCa channels
- Author
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Michael D. Cahalan, K. George Chandy, Vikram G. Shakkottai, J. Jay Gargus, George A. Gutman, Aaron Kolski-Andreaco, and Hiroaki Tomita
- Subjects
Patch-Clamp Techniques ,Potassium Channels ,Small-Conductance Calcium-Activated Potassium Channels ,Biochemistry ,PC12 Cells ,Potassium Channels, Calcium-Activated ,Protein Isoforms ,Tissue Distribution ,Genes, Dominant ,Transmembrane channels ,Microscopy, Confocal ,biology ,Reverse Transcriptase Polymerase Chain Reaction ,Muscles ,Exons ,Intermediate-Conductance Calcium-Activated Potassium Channels ,Potassium channel ,Cell biology ,Signal transduction ,Signal Transduction ,DNA, Complementary ,Calmodulin ,Green Fluorescent Proteins ,Molecular Sequence Data ,Transfection ,Cell Line ,SK channel ,SK3 ,Animals ,Humans ,Patch clamp ,Amino Acid Sequence ,Gene Silencing ,RNA, Messenger ,Molecular Biology ,Base Sequence ,Models, Genetic ,Sequence Homology, Amino Acid ,T-type calcium channel ,Cell Biology ,Hematopoietic Stem Cells ,Molecular biology ,Introns ,Protein Structure, Tertiary ,Rats ,Alternative Splicing ,Luminescent Proteins ,biology.protein ,Gene Deletion - Abstract
Small conductance Ca2+-activated K+ channels, products of the SK1-SK3 genes, regulate membrane excitability both within and outside the nervous system. We report the characterization of a SK3 variant (SK3-1C) that differs from SK3 by utilizing an alternative first exon (exon 1C) in place of exon 1A used by SK3, but is otherwise identical to SK3. Quantitative RT-PCR detected abundant expression of SK3-1C transcripts in human lymphoid tissues, skeletal muscle, trachea, and salivary gland but not the nervous system. SK3-1C did not produce functional channels when expressed alone in mammalian cells, but suppressed SK1, SK2, SK3, and IKCa1 channels, but not BKCa or KV channels. Confocal microscopy revealed that SK3-1C sequestered SK3 protein intracellularly. Dominant-inhibitory activity of SK3-1C was not due to a nonspecific calmodulin sponge effect since overexpression of calmodulin did not reverse SK3-1C-mediated intracellular trapping of SK3 protein, and calmodulin-Ca2+-dependent inactivation of CaV channels was not affected by SK3-1C overexpression. Deletion analysis identified a dominant-inhibitory segment in the SK3-1C C terminus that resembles tetramerization-coiled-coiled domains reported to enhance tetramer stability and selectivity of multimerization of many K+ channels. SK3-1C may therefore suppress calmodulin-gated SKCa/IKCa channels by trapping these channel proteins intracellularly via subunit interactions mediated by the dominant-inhibitory segment and thereby reduce functional channel expression on the cell surface. Such family-wide dominant-negative suppression by SK3-1C provides a powerful mechanism to titrate membrane excitability and is a useful approach to define the functional in vivo role of these channels in diverse tissues by their targeted silencing.
- Published
- 2003
41. Novel truncated isoform of SK3 potassium channel is a potent dominant-negative regulator of SK currents: implications in schizophrenia
- Author
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Hiroaki Tomita, Vikram G. Shakkottai, G. Sun, William E. Bunney, George A. Gutman, Michael D. Cahalan, J. Jay Gargus, and K G Chandy
- Subjects
medicine.medical_specialty ,Potassium Channels ,Small-Conductance Calcium-Activated Potassium Channels ,Green Fluorescent Proteins ,Molecular Sequence Data ,Biology ,PC12 Cells ,Membrane Potentials ,SK channel ,Cellular and Molecular Neuroscience ,chemistry.chemical_compound ,Jurkat Cells ,Potassium Channels, Calcium-Activated ,SK3 ,Isomerism ,Internal medicine ,Monoaminergic ,medicine ,Animals ,Humans ,Neurotransmitter ,Molecular Biology ,Genes, Dominant ,Membrane potential ,Brain Chemistry ,Neurons ,Base Sequence ,Potassium channel ,Cell biology ,Protein Structure, Tertiary ,Rats ,Psychiatry and Mental health ,Transmembrane domain ,Luminescent Proteins ,Endocrinology ,chemistry ,Schizophrenia ,Calcium ,Indicators and Reagents ,Intracellular - Abstract
The small-conductance calcium-activated K(+) channel SK3 (SKCa3/KCNN3) regulates electrical excitability and neurotransmitter release in monoaminergic neurons, and has been implicated in schizophrenia, ataxia and anorexia nervosa. We have identified a novel SK3 transcript, SK3-1B that utilizes an alternative first exon (exon 1B), but is otherwise identical to SK3. SK3-1B, mRNA is widely distributed in human tissues and is present at 20-60% of SK3 in the brain. The SK3-1B protein lacks the N-terminus and first transmembrane segment, and begins eight residues upstream of the second transmembrane segment. When expressed alone, SK3-1B did not produce functional channels, but selectively suppressed endogenous SK3 currents in the pheochromocytoma cell line, PC12, in a dominant-negative fashion. This dominant inhibitory effect extended to other members of the SK subfamily, but not to voltage-gated K(+) channels, and appears to be due to intracellular trapping of endogenous SK channels. The effect of SK3-1B expression is very similar to that produced by expression of the rare SK3 truncation allele, SK3-Delta, found in a patient with schizophrenia. Regulation of SK3 and SK3-1B levels may provide a potent mechanism to titrate neuronal firing rates and neurotransmitter release in monoaminergic neurons, and alterations in the relative abundance of these proteins could contribute to abnormal neuronal excitability, and to the pathogenesis of schizophrenia.
- Published
- 2003
42. Potassium channels in T lymphocytes: toxins to therapeutic immunosuppressants
- Author
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George A. Gutman, K. George Chandy, Heike Wulff, Michael D. Cahalan, Raymond S. Norton, and Michael W. Pennington
- Subjects
Potassium Channels ,Stereochemistry ,Toxin ,Potassium ,T-Lymphocytes ,chemistry.chemical_element ,Potassium channel blocker ,Biological activity ,T lymphocyte ,Biology ,Pharmacology ,Toxicology ,medicine.disease_cause ,Animal origin ,Potassium channel ,Pharmaceutical technology ,chemistry ,medicine ,Potassium Channel Blockers ,Animals ,Humans ,Immunosuppressive Agents ,medicine.drug ,Toxins, Biological - Published
- 2001
43. A unified nomenclature for short-chain peptides isolated from scorpion venoms: alpha-KTx molecular subfamilies
- Author
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Maria L. Garcia, George A. Gutman, K. George Chandy, Marie-France Martin-Eauclaire, Jan Tytgat, Jurg van der Walt, and Lourival D. Possani
- Subjects
Pharmacology ,chemistry.chemical_classification ,Scorpion toxin ,Potassium Channels ,biology ,Mesobuthus martensii ,Molecular Sequence Data ,Scorpion Venoms ,Venom ,Peptide ,Toxicology ,biology.organism_classification ,Maurotoxin ,chemistry ,Biochemistry ,Terminology as Topic ,Potassium Channel Blockers ,Amino Acid Sequence ,Peptides ,Peptide sequence ,Mesobuthus eupeus - Abstract
Peptidyl toxins are used extensively to determine the pharmacology of ion channels. Four families of peptides have been purified from scorpion venom. In this article, the classification of K + -channel-blocking peptides belonging to family 2 peptides and comprising 30–40 amino acids linked by three or four disulfide bridges, will be discussed. Evidence is provided for the existence of 12 molecular subfamilies, named α-KTx1–12, containing 49 different peptides. Because of the pharmacological divergence of these peptides, the principle of classification was based on a primary sequence alignment, combined with maximum parsimony and Neighbour-Joining analysis.
- Published
- 1999
44. hKCa3/KCNN3 potassium channel gene: association of longer CAG repeats with schizophrenia in Israeli Ashkenazi Jews, expression in human tissues and localization to chromosome 1q21
- Author
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R. Kimhi, T Litmanovitch, Edward G. Jones, J. Jay Gargus, Marnina Swartz, George A. Gutman, Emmanuelle Fantino, Ruth Navon, K G Chandy, Ronit Weizman, V Dror, Eyal Shamir, L Avivi, Sanjiv Ghanshani, K. Kalman, and Yoram Barak
- Subjects
medicine.medical_specialty ,Cerebellum ,Potassium Channels ,Transcription, Genetic ,Small-Conductance Calcium-Activated Potassium Channels ,Thalamus ,Molecular Sequence Data ,Substantia nigra ,Biology ,Polymerase Chain Reaction ,Cellular and Molecular Neuroscience ,Potassium Channels, Calcium-Activated ,Trinucleotide Repeats ,Internal medicine ,Basal ganglia ,medicine ,Humans ,Lymphocytes ,Israel ,Molecular Biology ,Allele frequency ,DNA Primers ,Genetics ,Base Sequence ,Brain ,Chromosome Mapping ,Exons ,Ashkenazi jews ,Introns ,Ventral tegmental area ,Europe ,Psychiatry and Mental health ,medicine.anatomical_structure ,Endocrinology ,nervous system ,Spinal Cord ,Cerebral cortex ,Chromosomes, Human, Pair 1 ,Organ Specificity ,Jews ,Schizophrenia - Abstract
We demonstrate a significant association between longer CAG repeats in the hKCa3/KCNN3 calcium-activated potassium channel gene and schizophrenia in Israeli Ashkenazi Jews. We genotyped alleles from 84 Israeli Jewish patients with schizophrenia and from 102 matched controls. The overall allele frequency distribution is significantly different in patients vs controls (P = 0.00017, Wilcoxon Rank Sum test), with patients showing greater lengths of the CAG repeat. Northern blots reveal substantial levels of approximately 9 kb and approximately 13 kb hKCa3/KCNN3transcripts in brain, striated muscle, spleen and lymph nodes. Within the brain, hKCa3/KCNN3transcripts are most abundantly expressed in the substantia nigra, lesser amounts are detected in the basal ganglia, amygdala, hippocampus and subthalamic nuclei, while little is seen in the cerebral cortex, cerebellum and thalamus. In situ hybridization reveals abundant hKCa3/KCNN3 message localized within the substantia nigra and ventral tegmental area, and along the distributions of dopaminergic neurons from these regions into the nigrostriatal and mesolimbic pathways. FISH analysis shows that hKCa3/KCNN3 is located on chromosome 1q21.
- Published
- 1999
45. A Family of Three Mouse Potassium Channel Genes with Intronless Coding Regions
- Author
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Calvin B. Williams, Bruce L. Tempel, K G Chandy, George A. Gutman, R.H. Spencer, BA Aguilar, and Sanjiv Ghanshani
- Subjects
Genetics ,Mice, Inbred BALB C ,Potassium Channels ,Multidisciplinary ,Sequence analysis ,Molecular Sequence Data ,Restriction Mapping ,Alternative splicing ,Nucleic Acid Hybridization ,DNA ,Exons ,Biology ,Genome ,Introns ,Potassium channel ,Mice ,Exon ,Complementary DNA ,Animals ,Coding region ,Drosophila ,Amino Acid Sequence ,DNA Probes ,Gene - Abstract
To understand the molecular mechanisms responsible for generating physiologically diverse potassium channels in mammalian cells, mouse genomic clones have been isolated with a potassium channel complementary DNA, MBK1, that is homologous to the Drosophila potassium channel gene, Shaker. A family of three closely related potassium channel genes (MK1, MK2, and MK3) that are encoded at distinct genomic loci has been isolated. Sequence analysis reveals that the coding region of each of these three genes exists as a single uninterrupted exon in the mouse genome. This organization precludes the generation of multiple forms of the protein by alternative RNA splicing, a mechanism known to characterize the Drosophila potassium channel genes Shaker and Shab. Thus, mammals may use a different strategy for generating diverse K+ channels by encoding related genes at multiple distinct genomic loci, each of which produces only a single protein.
- Published
- 1990
46. Human calcium-activated potassium channel gene KCNN4 maps to chromosome 19q13.2 in the region deleted in diamond-blackfan anemia
- Author
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Matthew A. Coleman, P. Gustavsson, Sanjiv Ghanshani, Niklas Dahl, Harvey W. Mohrenweiser, J. Jay Gargus, George A. Gutman, K G Chandy, and A. C.-L. Wu
- Subjects
Genetics ,Mutation ,Potassium Channels ,Chromosome ,Chromosome Mapping ,Biology ,medicine.disease_cause ,medicine.disease ,Intermediate-Conductance Calcium-Activated Potassium Channels ,Molecular biology ,Potassium channel ,Calcium-activated potassium channel ,KCNN4 ,Potassium Channels, Calcium-Activated ,Fanconi Anemia ,Gene mapping ,hemic and lymphatic diseases ,medicine ,Humans ,Diamond–Blackfan anemia ,Gene ,Chromosomes, Human, Pair 19 ,Sequence Deletion - Abstract
Human calcium-activated potassium channel gene, hKCa4 on human chromosome 19q13.2 in region deleted in Diamond-Blackfan anemia.
- Published
- 1998
47. Translation initiation of a cardiac voltage-gated potassium channel by internal ribosome entry
- Author
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K G Chandy, L. E.-C. Leong, D. Negulescu, George A. Gutman, and Bert L. Semler
- Subjects
Chloramphenicol O-Acetyltransferase ,Potassium Channels ,Reticulocytes ,Five prime untranslated region ,Molecular Sequence Data ,Biology ,Transfection ,Biochemistry ,Mice ,Eukaryotic translation ,Cistron ,Genes, Reporter ,Initiation factor ,Animals ,Humans ,RNA, Messenger ,Luciferases ,Molecular Biology ,Cells, Cultured ,Base Sequence ,EIF4E ,Translation (biology) ,Heart ,Cell Biology ,Molecular biology ,Ribosomal binding site ,Internal ribosome entry site ,Potassium Channels, Voltage-Gated ,Protein Biosynthesis ,Kv1.4 Potassium Channel ,Nucleic Acid Conformation ,Rabbits ,Ion Channel Gating ,Ribosomes - Abstract
The mammalian Kv1.4 voltage-gated potassium channel mRNA contains an unusually long (1.2 kilobases) 5'-untranslated region (UTR) and includes 18 AUG codons upstream of the authentic site of translation initiation. Computer-predicted secondary structures of this region reveal complex stem-loop structures that would serve as barriers to 5' --> 3' ribosomal scanning. These features suggested that translation initiation in Kv1.4 might occur by the mechanism of internal ribosome entry, a mode of initiation employed by a variety of RNA viruses but only a limited number of vertebrate genes. To test this possibility we introduced the 5'-UTR of mouse Kv1.4 mRNA into the intercistronic region of a bicistronic vector containing two tandem reporter genes, chloramphenicol acetyltransferase and luciferase. The control construct translated only the upstream chloramphenicol cistron in transiently transfected mammalian cells. In contrast, the construct containing the mKv1.4 UTR efficiently translated the luciferase cistron as well, demonstrating the presence of an internal ribosome entry segment. Progressive 5' --> 3' deletions localized the activity to a 3'-proximal 200-nucleotide fragment. Suppression of cap-dependent translation by extracts from poliovirus-infected HeLa cells in an in vitro translation assay eliminated translation of the upstream cistron while allowing translation of the downstream cistron. Our results indicate that the 5'-untranslated region of mKv1.4 contains a functional internal ribosome entry segment that may contribute to unusual and physiologically important modes of translation regulation for this and other potassium channel genes.
- Published
- 1998
48. Purification, visualization, and biophysical characterization of Kv1.3 tetramers
- Author
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Jayashree Aiyar, K G Chandy, Yuri Sokolov, B Takenaka, H Park, R.H. Spencer, Huilin Li, Anthony J. Milici, George A. Gutman, Angela Nguyen, James E. Hall, and Bing K. Jap
- Subjects
Glycosylation ,Potassium Channels ,Protein Conformation ,Neurotoxins ,Scorpion Venoms ,Peptide ,Cholic Acid ,Biology ,Biochemistry ,Chromatography, Affinity ,chemistry.chemical_compound ,Protein structure ,Cnidarian Venoms ,Tetramer ,Chlorocebus aethiops ,Animals ,Lipid bilayer ,Molecular Biology ,Peptide sequence ,chemistry.chemical_classification ,Kv1.3 Potassium Channel ,Voltage-gated ion channel ,Margatoxin ,Cholic Acids ,Cell Biology ,chemistry ,Solubility ,Potassium Channels, Voltage-Gated ,Potassium - Abstract
The voltage-gated K+ channel of T-lymphocytes, Kv1.3, was heterologously expressed in African Green Monkey kidney cells (CV-1) using a vaccinia virus/T7 hybrid expression system; each infected cell exhibited 10(4) to 5 x 10(5) functional channels on the cell surface. The protein, solubilized with detergent (3-[cholamidopropyl)dimethylammonio]-1-propanesulfonic acid or cholate), was purified to near-homogeneity by a single nickel-chelate chromatography step. The Kv1.3 protein expressed in vaccinia virus-infected cells and its purified counterpart are both modified by a approximately 2-kDa core-sugar moiety, most likely at a conserved N-glycosylation site in the external S1-S2 loop; absence of the sugar does not alter the biophysical properties of the channel nor does it affect expression levels. Purified Kv1.3 has an estimated size of approximately 64 kDa in denaturing SDS-polyacrylamide electrophoresis gels, consistent with its predicted size based on the amino acid sequence. By sucrose gradient sedimentation, purified Kv1.3 is seen primarily as a single peak with an approximate mass of 270 kDa, compatible with its being a homotetrameric complex of the approximately 64-kDa subunits. When reconstituted in the presence of lipid and visualized by negative-staining electron microscopy, the purified Kv1.3 protein forms small crystalline domains consisting of tetramers with dimensions of approximately 65 x 65 A. The center of each tetramer contains a stained depression which may represent the ion conduction pathway. Functional reconstitution of the Kv1.3 protein into lipid bilayers produces voltage-dependent K+-selective currents that can be blocked by two high affinity peptide antagonists of Kv1.3, margatoxin and stichodactylatoxin.
- Published
- 1997
49. The signature sequence of voltage-gated potassium channels projects into the external vestibule
- Author
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James P. Rizzi, George A. Gutman, K. George Chandy, and Jayashree Aiyar
- Subjects
Models, Molecular ,Potassium Channels ,Molecular model ,Xenopus ,Mutant ,Kaliotoxin ,Scorpion Venoms ,Biochemistry ,Ion ,Structure-Activity Relationship ,Tetramer ,Animals ,Molecular Biology ,Aspartic Acid ,Scorpion toxin ,Binding Sites ,Kv1.3 Potassium Channel ,Chemistry ,Lysine ,Cell Biology ,Voltage-gated potassium channel ,Crystallography ,Kinetics ,Potassium Channels, Voltage-Gated ,Vestibule ,Mutagenesis, Site-Directed ,Thermodynamics ,Tyrosine - Abstract
A highly conserved motif, GYGD, contributes to the formation of the ion selectivity filter in voltage-gated K+ channels and is thought to interact with the scorpion toxin residue, Lys27. By probing the pore of the Kv1.3 channel with synthetic kaliotoxin-Lys27 mutants, each containing a non-natural lysine analog of a different length, and using mutant cycle analysis, we determined the spatial locations of Tyr400 and Asp402 in the GYGD motif, relative to His404 located at the base of the outer vestibule. Our data indicate that the terminal amines of the shorter Lys27 analogs lie close to His404 and to Asp402, while Lys27 itself interacts with Tyr400. Based on these data, we developed a molecular model of this region of the channel. The junction between the outer vestibule and the pore is defined by a ring ( approximately 8-9-A diameter) formed from alternating Asp402 and His404 residues. Tyr400 lies 4-6 A deeper into the pore, and its interaction with kaliotoxin-Lys27 is in competition with K+ ions. Studies with dimeric Kv1.3 constructs suggest that two Tyr400 residues in the tetramer are sufficient to bind K+ ions. Thus, at least part of the K+ channel signature sequence extends into a shallow trough at the center of a wide external vestibule.
- Published
- 1996
50. International Union of Pharmacology: Approaches to the Nomenclature of Voltage-Gated Ion Channels
- Author
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Anthony J. Harmar, William A. Catterall, K. G. Chandy, Franz Hofmann, George A. Gutman, Darrell R. Abernethy, David E. Clapham, and Michael Spedding
- Subjects
Pharmacology ,Voltage-gated ion channel ,business.industry ,Molecular Medicine ,Medicine ,business ,Ion channel - Abstract
This issue of Pharmacological Reviews includes a new venture in the collaboration between the International Union of Pharmacology (IUPHAR) and the American Society for Pharmacology and Experimental Therapeutics (ASPET), in that a new classification of voltage-gated ion channels is outlined in this
- Published
- 2003
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