57 results on '"Liebscher I"'
Search Results
2. The repertoire and structure of adhesion GPCR transcript variants assembled from publicly available deep-sequenced human samples.
- Author
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Kuhn CK, Stenzel U, Berndt S, Liebscher I, Schöneberg T, and Horn S
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- Humans, Transcriptome genetics, RNA, Messenger genetics, RNA, Messenger metabolism, RNA, Messenger chemistry, Exons genetics, Protein Domains, Receptors, G-Protein-Coupled genetics, Receptors, G-Protein-Coupled metabolism, Receptors, G-Protein-Coupled chemistry, Alternative Splicing, High-Throughput Nucleotide Sequencing
- Abstract
Alternative splicing and multiple transcription start and termination sites can produce a diverse repertoire of mRNA transcript variants from a given gene. While the full picture of the human transcriptome is still incomplete, publicly available RNA datasets have enabled the assembly of transcripts. Using publicly available deep sequencing data from 927 human samples across 48 tissues, we quantified known and new transcript variants, provide an interactive, browser-based application Splice-O-Mat and demonstrate its relevance using adhesion G protein-coupled receptors (aGPCRs) as an example. On average, 24 different transcript variants were detected for each of the 33 human aGPCR genes, and several dominant transcript variants were not yet annotated. Variable transcription starts and complex exon-intron structures encode a flexible protein domain architecture of the N- and C termini and the seven-transmembrane helix domain (7TMD). Notably, we discovered the first GPCR (ADGRG7/GPR128) with eight transmembrane helices. Both the N- and C terminus of this aGPCR were intracellularly oriented, anchoring the N terminus in the plasma membrane. Moreover, the assessment of tissue-specific transcript variants, also for other gene classes, in our application may change the evaluation of disease-causing mutations, as their position in different transcript variants may explain tissue-specific phenotypes., (© The Author(s) 2024. Published by Oxford University Press on behalf of Nucleic Acids Research.)
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- 2024
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3. The dark sides of the GPCR tree - research progress on understudied GPCRs.
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Scharf MM, Humphrys LJ, Berndt S, Di Pizio A, Lehmann J, Liebscher I, Nicoli A, Niv MY, Peri L, Schihada H, and Schulte G
- Abstract
A large portion of the human GPCRome is still in the dark and understudied, consisting even of entire subfamilies of GPCRs such as odorant receptors, class A and C orphans, adhesion GPCRs, Frizzleds and taste receptors. However, it is undeniable that these GPCRs bring an untapped therapeutic potential that should be explored further. Open questions on these GPCRs span diverse topics such as deorphanisation, the development of tool compounds and tools for studying these GPCRs, as well as understanding basic signalling mechanisms. This review gives an overview of the current state of knowledge for each of the diverse subfamilies of understudied receptors regarding their physiological relevance, molecular mechanisms, endogenous ligands and pharmacological tools. Furthermore, it identifies some of the largest knowledge gaps that should be addressed in the foreseeable future and lists some general strategies that might be helpful in this process., (© 2024 The Authors. British Journal of Pharmacology published by John Wiley & Sons Ltd on behalf of British Pharmacological Society.)
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- 2024
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4. The adhesion GPCR GPR116/ADGRF5 has a dual function in pancreatic islets regulating somatostatin release and islet development.
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Röthe J, Kraft R, Ricken A, Kaczmarek I, Matz-Soja M, Winter K, Dietzsch AN, Buchold J, Ludwig MG, Liebscher I, Schöneberg T, and Thor D
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- Humans, Animals, Mice, Somatostatin metabolism, Insulin metabolism, Lung metabolism, Receptors, G-Protein-Coupled genetics, Receptors, G-Protein-Coupled metabolism, Mice, Knockout, Glucose metabolism, Islets of Langerhans metabolism
- Abstract
Glucose homeostasis is maintained by hormones secreted from different cell types of the pancreatic islets and controlled by manifold input including signals mediated through G protein-coupled receptors (GPCRs). RNA-seq analyses revealed expression of numerous GPCRs in mouse and human pancreatic islets, among them Gpr116/Adgrf5. GPR116 is an adhesion GPCR mainly found in lung and required for surfactant secretion. Here, we demonstrate that GPR116 is involved in the somatostatin release from pancreatic delta cells using a whole-body as well as a cell-specific knock-out mouse model. Interestingly, the whole-body GPR116 deficiency causes further changes such as decreased beta-cell mass, lower number of small islets, and reduced pancreatic insulin content. Glucose homeostasis in global GPR116-deficient mice is maintained by counter-acting mechanisms modulating insulin degradation. Our data highlight an important function of GPR116 in controlling glucose homeostasis., (© 2024. The Author(s).)
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- 2024
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5. G Protein-Coupled Receptors in Cell Signaling Transduction.
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Beer-Hammer S and Liebscher I
- Abstract
G protein-coupled receptors (GPCRs) and their downstream signaling pathways are critical targets for current pharmacotherapy [...].
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- 2023
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6. Intramolecular activity regulation of adhesion GPCRs in light of recent structural and evolutionary information.
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Kleinau G, Ali AH, Wiechert F, Szczepek M, Schmidt A, Spahn CMT, Liebscher I, Schöneberg T, and Scheerer P
- Subjects
- Binding Sites, Protein Domains, Biological Evolution, Signal Transduction
- Abstract
The class B2 of GPCRs known as adhesion G protein-coupled receptors (aGPCRs) has come under increasing academic and nonacademic research focus over the past decade due to their physiological importance as mechano-sensors in cell-cell and cell-matrix contexts. A major advance in understanding signal transduction of aGPCRs was achieved by the identification of the so-called Stachel sequence, which acts as an intramolecular agonist at the interface between the N terminus (Nt) and the seven-transmembrane helix domain (7TMD). Distinct extracellular signals received by the Nt are integrated at the Stachel into structural changes of the 7TMD towards an active state conformation. Until recently, little information was available on how the activation process of aGPCRs is realized at the molecular level. In the past three years several structures of the 7TMD plus the Stachel in complex with G proteins have been determined, which provide new insights into the architecture and molecular function of this receptor class. Herein, we review this structural information to extract common and distinct aGPCR features with particular focus on the Stachel binding site within the 7TMD. Our analysis extends the current view of aGPCR activation and exposes similarities and differences not only between diverse aGPCR members, but also compared to other GPCR classes., Competing Interests: Declaration of Competing Interest None., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)
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- 2023
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7. PTK7 is a positive allosteric modulator of GPR133 signaling in glioblastoma.
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Frenster JD, Erdjument-Bromage H, Stephan G, Ravn-Boess N, Wang S, Liu W, Bready D, Wilcox J, Kieslich B, Jankovic M, Wilde C, Horn S, Sträter N, Liebscher I, Schöneberg T, Fenyo D, Neubert TA, and Placantonakis DG
- Subjects
- Humans, Signal Transduction, Receptors, G-Protein-Coupled metabolism, Cell Membrane metabolism, Allosteric Regulation, Ligands, Allosteric Site, Cell Adhesion Molecules metabolism, Receptor Protein-Tyrosine Kinases metabolism, Glioblastoma
- Abstract
The adhesion G-protein-coupled receptor GPR133 (ADGRD1) supports growth of the brain malignancy glioblastoma. How the extracellular interactome of GPR133 in glioblastoma modulates signaling remains unknown. Here, we use affinity proteomics to identify the transmembrane protein PTK7 as an extracellular binding partner of GPR133 in glioblastoma. PTK7 binds the autoproteolytically generated N-terminal fragment of GPR133 and its expression in trans increases GPR133 signaling. This effect requires the intramolecular cleavage of GPR133 and PTK7's anchoring in the plasma membrane. PTK7's allosteric action on GPR133 signaling is additive with but topographically distinct from orthosteric activation by soluble peptide mimicking the endogenous tethered Stachel agonist. GPR133 and PTK7 are expressed in adjacent cells in glioblastoma, where their knockdown phenocopies each other. We propose that this ligand-receptor interaction is relevant to the pathogenesis of glioblastoma and possibly other physiological processes in healthy tissues., Competing Interests: Declaration of interests D.G.P. and NYU Grossman School of Medicine own a patent in the European Union and Hong Kong titled “Method for treating high grade glioma” on the use of GPR133 as a treatment target in glioma. D.G.P. has received consultant fees from Tocagen, Synaptive Medical, Monteris, Advantis, and Robeaute in the past., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2023
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8. Collagen VI Is a Gi-Biased Ligand of the Adhesion GPCR GPR126/ADGRG6.
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Wilde C, Chaudhry PM, Luo R, Simon KU, Piao X, and Liebscher I
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- Ligands, Schwann Cells metabolism, Collagen metabolism, Receptors, G-Protein-Coupled metabolism, Signal Transduction
- Abstract
GPR126/ADGRG6, a member of the adhesion G-protein-coupled receptor family, balances cell differentiation and proliferation through fine-tuning of intracellular cAMP levels, which is achieved through coupling to Gs and Gi proteins. While GPR126-mediated cAMP increase has been proven to be essential for differentiation of Schwann cells, adipocytes and osteoblasts, Gi-signaling of the receptor was found to propagate breast cancer cell proliferation. Extracellular ligands or mechanical forces can modulate GPR126 activity but require an intact encrypted agonist sequence, coined the Stachel . Even though coupling to Gi can be seen for constitutively active truncated receptor versions of GPR126 as well as with a peptide agonist derived from the Stachel sequence, all known N-terminal modulators have so far only been shown to modulate Gs coupling. Here, we identified collagen VI as the first extracellular matrix ligand of GPR126 that induces Gi signaling at the receptor, which shows that N-terminal binding partners can mediate selective G protein signaling cascades that are masked by fully active truncated receptor variants.
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- 2023
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9. Adhesion G protein-coupled receptors-Structure and functions.
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Thor D and Liebscher I
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- Animals, Humans, Cell Adhesion, Structure-Activity Relationship, Cell Membrane metabolism, Proteolysis, Receptors, G-Protein-Coupled chemistry
- Abstract
Adhesion G protein-coupled receptors (aGPCRs) are an ancient class of receptors that represent some of the largest transmembrane-integrated proteins in humans. First recognized as surface markers on immune cells, it took more than a decade to appreciate their 7-transmembrane structure, which is reminiscent of GPCRs. Roughly 30 years went by before the first functional proof of an interaction with a G protein was published. Besides classic features of GPCRs (extracellular N terminus, 7-transmembrane region, intracellular C terminus), aGPCRs display a distinct N-terminal structure, which harbors the highly conserved GPCR autoproteolysis-inducing (GAIN) domain with the GPCR proteolysis site (GPS) in addition to several functional domains. Several human diseases have been associated with variants of aGPCRs and subsequent animal models have been established to investigate these phenotypes. Much progress has been made in recent years to decipher the structure and functions of these receptors. This chapter gives an overview of our current understanding with respect to the molecular structural patterns governing aGPCR activation and the contribution of these giant molecules to the development of pathologies., (Copyright © 2023 Elsevier Inc. All rights reserved.)
- Published
- 2023
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10. A guide to adhesion GPCR research.
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Liebscher I, Cevheroğlu O, Hsiao CC, Maia AF, Schihada H, Scholz N, Soave M, Spiess K, Trajković K, Kosloff M, and Prömel S
- Subjects
- Cell Adhesion, Receptors, G-Protein-Coupled genetics, Receptors, G-Protein-Coupled metabolism, Signal Transduction
- Abstract
Adhesion G protein-coupled receptors (aGPCRs) are a class of structurally and functionally highly intriguing cell surface receptors with essential functions in health and disease. Thus, they display a vastly unexploited pharmacological potential. Our current understanding of the physiological functions and signaling mechanisms of aGPCRs form the basis for elucidating further molecular aspects. Combining these with novel tools and methodologies from different fields tailored for studying these unusual receptors yields a powerful potential for pushing aGPCR research from singular approaches toward building up an in-depth knowledge that will facilitate its translation to applied science. In this review, we summarize the state-of-the-art knowledge on aGPCRs in respect to structure-function relations, physiology, and clinical aspects, as well as the latest advances in the field. We highlight the upcoming most pressing topics in aGPCR research and identify strategies to tackle them. Furthermore, we discuss approaches how to promote, stimulate, and translate research on aGPCRs 'from bench to bedside' in the future., (© 2021 The Authors. The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)
- Published
- 2022
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11. Stachel-mediated activation of adhesion G protein-coupled receptors: insights from cryo-EM studies.
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Liebscher I, Schöneberg T, and Thor D
- Subjects
- Cryoelectron Microscopy, Protein Binding, Receptors, G-Protein-Coupled genetics
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- 2022
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12. The N Terminus of Adhesion G Protein-Coupled Receptor GPR126/ADGRG6 as Allosteric Force Integrator.
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Mitgau J, Franke J, Schinner C, Stephan G, Berndt S, Placantonakis DG, Kalwa H, Spindler V, Wilde C, and Liebscher I
- Abstract
The adhesion G protein-coupled receptor (aGPCR) GPR126/ADGRG6 plays an important role in several physiological functions, such as myelination or peripheral nerve repair. This renders the receptor an attractive pharmacological target. GPR126 is a mechano-sensor that translates the binding of extracellular matrix (ECM) molecules to its N terminus into a metabotropic intracellular signal. To date, the structural requirements and the character of the forces needed for this ECM-mediated receptor activation are largely unknown. In this study, we provide this information by combining classic second-messenger detection with single-cell atomic force microscopy. We established a monoclonal antibody targeting the N terminus to stimulate GPR126 and compared it to the activation through its known ECM ligands, collagen IV and laminin 211. As each ligand uses a distinct mode of action, the N terminus can be regarded as an allosteric module that can fine-tune receptor activation in a context-specific manner., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Mitgau, Franke, Schinner, Stephan, Berndt, Placantonakis, Kalwa, Spindler, Wilde and Liebscher.)
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- 2022
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13. Activation of the adhesion G protein-coupled receptor GPR133 by antibodies targeting its N-terminus.
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Stephan G, Frenster JD, Liebscher I, and Placantonakis DG
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- HEK293 Cells, Humans, Signal Transduction drug effects, Antibodies metabolism, Antibodies pharmacology, Glioblastoma metabolism, Receptors, G-Protein-Coupled genetics, Receptors, G-Protein-Coupled metabolism
- Abstract
We recently demonstrated that GPR133 (ADGRD1), an adhesion G protein-coupled receptor involved in raising cytosolic cAMP levels, is necessary for growth of glioblastoma (GBM) and is de novo expressed in GBM relative to normal brain tissue. Our previous work suggested that dissociation of autoproteolytically generated N-terminal and C-terminal fragments of GPR133 at the plasma membrane correlates with receptor activation and signaling. To promote the goal of developing biologics that modulate GPR133 function, we investigated the effects of antibodies against the N-terminus of GPR133 on receptor signaling. Here, we show that treatment of HEK293T cells overexpressing GPR133 with these antibodies increased cAMP levels in a concentration-dependent manner. Analysis of culture medium following antibody treatment further indicated the presence of complexes of these antibodies with the autoproteolytically cleaved N-terminal fragments of GPR133. In addition, cells expressing a cleavage-deficient mutant of GPR133 (H543R) did not respond to antibody stimulation, suggesting that the effect is cleavage dependent. Finally, we demonstrate the antibody-mediated stimulation of WT GPR133, but not the cleavage-deficient H543R mutant, was reproducible in patient-derived GBM cells. These findings provide a paradigm for modulation of GPR133 function with biologics and support the hypothesis that the intramolecular cleavage in the N-terminus modulates receptor activation and signaling., Competing Interests: Conflict of interest D. G. P. and NYU Grossman School of Medicine own an EU and Hong Kong patent titled “Method for treating high-grade gliomas” on the use of GPR133 as a treatment target in glioma. D. G. P. has received consultant fees from Tocagen, Synaptive Medical, Monteris and Robeaute. The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)
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- 2022
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14. Translating the force-mechano-sensing GPCRs.
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Wilde C, Mitgau J, Suchý T, Schöneberg T, and Liebscher I
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- Mechanical Phenomena, Membrane Proteins metabolism, Stress, Mechanical, Ion Channels, Receptors, G-Protein-Coupled metabolism
- Abstract
Incorporating mechanical cues into cellular responses allows us to experience our direct environment. Specialized cells can perceive and discriminate between different physical properties such as level of vibration, temperature, or pressure. Mechanical forces are abundant signals that also shape general cellular responses such as cytoskeletal rearrangement, differentiation, or migration and contribute to tissue development and function. The molecular structures that perceive and transduce mechanical forces are specialized cytoskeletal proteins, cell junction molecules, and membrane proteins such as ion channels and metabotropic receptors. G protein-coupled receptors (GPCRs) have attracted attention as metabotropic force receptors as they are among the most important drug targets. This review summarizes the function of mechano-sensitive GPCRs, specifically, the angiotensin II type 1 receptor and adrenergic, apelin, histamine, parathyroid hormone 1, and orphan receptors, focusing particularly on the advanced knowledge gained from adhesion-type GPCRs. We distinguish between shear stress and cell swelling/stretch as the two major types of mechano-activation of these receptors and contemplate the potential contribution of the force-from-lipid and force-from-tether models that have previously been suggested for ion channels.
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- 2022
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15. Hepatic Hedgehog Signaling Participates in the Crosstalk between Liver and Adipose Tissue in Mice by Regulating FGF21.
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Ott F, Körner C, Werner K, Gericke M, Liebscher I, Lobsien D, Radrezza S, Shevchenko A, Hofmann U, Kratzsch J, Gebhardt R, Berg T, and Matz-Soja M
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- Adipose Tissue metabolism, Animals, Female, Fibroblast Growth Factors metabolism, Liver metabolism, Mice, Hedgehog Proteins metabolism, Insulin Resistance physiology
- Abstract
The Hedgehog signaling pathway regulates many processes during embryogenesis and the homeostasis of adult organs. Recent data suggest that central metabolic processes and signaling cascades in the liver are controlled by the Hedgehog pathway and that changes in hepatic Hedgehog activity also affect peripheral tissues, such as the reproductive organs in females. Here, we show that hepatocyte-specific deletion of the Hedgehog pathway is associated with the dramatic expansion of adipose tissue in mice, the overall phenotype of which does not correspond to the classical outcome of insulin resistance-associated diabetes type 2 obesity. Rather, we show that alterations in the Hedgehog signaling pathway in the liver lead to a metabolic phenotype that is resembling metabolically healthy obesity. Mechanistically, we identified an indirect influence on the hepatic secretion of the fibroblast growth factor 21, which is regulated by a series of signaling cascades that are directly transcriptionally linked to the activity of the Hedgehog transcription factor GLI1. The results of this study impressively show that the metabolic balance of the entire organism is maintained via the activity of morphogenic signaling pathways, such as the Hedgehog cascade. Obviously, several pathways are orchestrated to facilitate liver metabolic status to peripheral organs, such as adipose tissue.
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- 2022
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16. Affinity Proteomics Identifies Interaction Partners and Defines Novel Insights into the Function of the Adhesion GPCR VLGR1/ADGRV1.
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Knapp B, Roedig J, Roedig H, Krzysko J, Horn N, Güler BE, Kusuluri DK, Yildirim A, Boldt K, Ueffing M, Liebscher I, and Wolfrum U
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- Humans, Retina metabolism, Signal Transduction, Proteomics, Receptors, G-Protein-Coupled metabolism
- Abstract
The very large G-protein-coupled receptor 1 (VLGR1/ADGRV1) is the largest member of the adhesion G-protein-coupled receptor (ADGR) family. Mutations in VLGR1/ADGRV1 cause human Usher syndrome (USH), a form of hereditary deaf-blindness, and have been additionally linked to epilepsy. In the absence of tangible knowledge of the molecular function and signaling of VLGR1, the pathomechanisms underlying the development of these diseases are still unknown. Our study aimed to identify novel, previously unknown protein networks associated with VLGR1 in order to describe new functional cellular modules of this receptor. Using affinity proteomics, we have identified numerous new potential binding partners and ligands of VLGR1. Tandem affinity purification hits were functionally grouped based on their Gene Ontology terms and associated with functional cellular modules indicative of functions of VLGR1 in transcriptional regulation, splicing, cell cycle regulation, ciliogenesis, cell adhesion, neuronal development, and retinal maintenance. In addition, we validated the identified protein interactions and pathways in vitro and in situ. Our data provided new insights into possible functions of VLGR1, related to the development of USH and epilepsy, and also suggest a possible role in the development of other neuronal diseases such as Alzheimer's disease.
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- 2022
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17. Structural basis for the tethered peptide activation of adhesion GPCRs.
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Ping YQ, Xiao P, Yang F, Zhao RJ, Guo SC, Yan X, Wu X, Zhang C, Lu Y, Zhao F, Zhou F, Xi YT, Yin W, Liu FZ, He DF, Zhang DL, Zhu ZL, Jiang Y, Du L, Feng SQ, Schöneberg T, Liebscher I, Xu HE, and Sun JP
- Subjects
- Binding Sites, Cryoelectron Microscopy, Protein Domains, Protein Structure, Secondary, Structure-Activity Relationship, Peptides, Receptors, G-Protein-Coupled metabolism
- Abstract
Adhesion G-protein-coupled receptors (aGPCRs) are important for organogenesis, neurodevelopment, reproduction and other processes
1-6 . Many aGPCRs are activated by a conserved internal (tethered) agonist sequence known as the Stachel sequence7-12 . Here, we report the cryogenic electron microscopy (cryo-EM) structures of two aGPCRs in complex with Gs : GPR133 and GPR114. The structures indicate that the Stachel sequences of both receptors assume an α-helical-bulge-β-sheet structure and insert into a binding site formed by the transmembrane domain (TMD). A hydrophobic interaction motif (HIM) within the Stachel sequence mediates most of the intramolecular interactions with the TMD. Combined with the cryo-EM structures, biochemical characterization of the HIM motif provides insight into the cross-reactivity and selectivity of the Stachel sequences. Two interconnected mechanisms, the sensing of Stachel sequences by the conserved 'toggle switch' W6.53 and the constitution of a hydrogen-bond network formed by Q7.49 /Y7.49 and the P6.47 /V6.47 φφG6.50 motif (φ indicates a hydrophobic residue), are important in Stachel sequence-mediated receptor activation and Gs coupling. Notably, this network stabilizes kink formation in TM helices 6 and 7 (TM6 and TM7, respectively). A common Gs -binding interface is observed between the two aGPCRs, and GPR114 has an extended TM7 that forms unique interactions with Gs . Our structures reveal the detailed mechanisms of aGPCR activation by Stachel sequences and their Gs coupling., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)- Published
- 2022
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18. Evaluating the feasibility of Cas9 overexpression in 3T3-L1 cells for generation of genetic knock-out adipocyte cell lines.
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Suchý T, Kaczmarek I, Maricic T, Zieschang C, Schöneberg T, Thor D, and Liebscher I
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- 3T3-L1 Cells, Adipogenesis genetics, Animals, Cell Differentiation, Cell Line, Feasibility Studies, Humans, Mice, Adipocytes, CRISPR-Cas Systems genetics
- Abstract
Cell lines recapitulating physiological processes can represent alternatives to animal or human studies. The 3T3-L1 cell line is used to mimic adipocyte function and differentiation. Since transfection of 3T3-L1 cells is difficult, we used a modified 3T3-L1 cell line overexpressing Cas9 for a straightforward generation of gene knock-outs. As an example, we intended to generate 3T3-L1 cell lines deficient for adhesion G protein-coupled receptors Gpr64/Adgr2 and Gpr126/Adgr6 using the CRISPR/Cas approach. Surprisingly, all the generated knock-out as well as scramble control cell lines were unresponsive to isoprenaline in respect to adiponectin secretion and lipolysis in contrast to the wild type 3T3-L1 cells. We, therefore, analysed the properties of these stable Cas9-overexpressing 3T3-L1 cells. We demonstrate that this commercially available cell line exhibits dysfunction in cAMP signalling pathways as well as reduced insulin sensitivity independent of gRNA transfection. We tried transient transfection of plasmids harbouring Cas9 as well as direct introduction of the Cas9 protein as alternate approaches to the stable expression of this enzyme. We find that transfection of the Cas9 protein is not only feasible but also does not impair adipogenesis and, therefore, represents a preferable alternative to achieve genetic knock-out.
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- 2021
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19. The relevance of adhesion G protein-coupled receptors in metabolic functions.
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Kaczmarek I, Suchý T, Prömel S, Schöneberg T, Liebscher I, and Thor D
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- Adipose Tissue, Central Nervous System, Signal Transduction, Islets of Langerhans, Receptors, G-Protein-Coupled
- Abstract
G protein-coupled receptors (GPCRs) modulate a variety of physiological functions and have been proven to be outstanding drug targets. However, approximately one-third of all non-olfactory GPCRs are still orphans in respect to their signal transduction and physiological functions. Receptors of the class of Adhesion GPCRs (aGPCRs) are among these orphan receptors. They are characterized by unique features in their structure and tissue-specific expression, which yields them interesting candidates for deorphanization and testing as potential therapeutic targets. Capable of G-protein coupling and non-G protein-mediated function, aGPCRs may extend our repertoire of influencing physiological function. Besides their described significance in the immune and central nervous systems, growing evidence indicates a high importance of these receptors in metabolic tissue. RNAseq analyses revealed high expression of several aGPCRs in pancreatic islets, adipose tissue, liver, and intestine but also in neurons governing food intake. In this review, we focus on aGPCRs and their function in regulating metabolic pathways. Based on current knowledge, this receptor class represents high potential for future pharmacological approaches addressing obesity and other metabolic diseases., (© 2021 Isabell Kaczmarek et al., published by De Gruyter, Berlin/Boston.)
- Published
- 2021
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20. New Structural Perspectives in G Protein-Coupled Receptor-Mediated Src Family Kinase Activation.
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Berndt S and Liebscher I
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- Amino Acid Sequence, Animals, Arrestins chemistry, Arrestins metabolism, Enzyme Activation, Humans, Molecular Docking Simulation, Molecular Dynamics Simulation, Multiprotein Complexes chemistry, Multiprotein Complexes metabolism, Protein Binding, Protein Conformation, Structure-Activity Relationship, Receptors, G-Protein-Coupled chemistry, Receptors, G-Protein-Coupled metabolism, src-Family Kinases chemistry, src-Family Kinases metabolism
- Abstract
Src family kinases (SFKs) are key regulators of cell proliferation, differentiation, and survival. The expression of these non-receptor tyrosine kinases is strongly correlated with cancer development and tumor progression. Thus, this family of proteins serves as an attractive drug target. The activation of SFKs can occur via multiple signaling pathways, yet many of them are poorly understood. Here, we summarize the current knowledge on G protein-coupled receptor (GPCR)-mediated regulation of SFKs, which is of considerable interest because GPCRs are among the most widely used pharmaceutical targets. This type of activation can occur through a direct interaction between the two proteins or be allosterically regulated by arrestins and G proteins. We postulate that a rearrangement of binding motifs within the active conformation of arrestin-3 mediates Src regulation by comparison of available crystal structures. Therefore, we hypothesize a potentially different activation mechanism compared to arrestin-2. Furthermore, we discuss the probable direct regulation of SFK by GPCRs and investigate the intracellular domains of exemplary GPCRs with conserved polyproline binding motifs that might serve as scaffolding domains to allow such a direct interaction. Large intracellular domains in GPCRs are often understudied and, in general, not much is known of their contribution to different signaling pathways. The suggested direct interaction between a GPCR and a SFK could allow for a potential immediate allosteric regulation of SFKs by GPCRs and thereby unravel a novel mechanism of SFK signaling. This overview will help to identify new GPCR-SFK interactions, which could serve to explain biological functions or be used to modulate downstream effectors.
- Published
- 2021
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21. Elevated expression of the adhesion GPCR ADGRL4/ELTD1 promotes endothelial sprouting angiogenesis without activating canonical GPCR signalling.
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Favara DM, Liebscher I, Jazayeri A, Nambiar M, Sheldon H, Banham AH, and Harris AL
- Subjects
- Codon, Endothelium, Vascular cytology, HEK293 Cells, Human Umbilical Vein Endothelial Cells, Humans, Up-Regulation, Endothelium, Vascular metabolism, Neovascularization, Pathologic, Receptors, G-Protein-Coupled metabolism, Signal Transduction
- Abstract
ADGRL4/ELTD1 is an orphan adhesion GPCR (aGPCR) expressed in endothelial cells that regulates tumour angiogenesis. The majority of aGPCRs are orphan receptors. The Stachel Hypothesis proposes a mechanism for aGPCR activation, in which aGPCRs contain a tethered agonist (termed Stachel) C-terminal to the GPCR-proteolytic site (GPS) cleavage point which, when exposed, initiates canonical GPCR signalling. This has been shown in a growing number of aGPCRs. We tested this hypothesis on ADGRL4/ELTD1 by designing full length (FL) and C-terminal fragment (CTF) ADGRL4/ELTD1 constructs, and a range of potential Stachel peptides. Constructs were transfected into HEK293T cells and HTRF FRET, luciferase-reporter and Alphascreen GPCR signalling assays were performed. A stable ADGRL4/ELTD1 overexpressing HUVEC line was additionally generated and angiogenesis assays, signalling assays and transcriptional profiling were performed. ADGRL4/ELTD1 has the lowest GC content in the aGPCR family and codon optimisation significantly increased its expression. FL and CTF ADGRL4/ELTD1 constructs, as well as Stachel peptides, did not activate canonical GPCR signalling. Furthermore, stable overexpression of ADGRL4/ELTD1 in HUVECs induced sprouting angiogenesis, lowered in vitro anastomoses, and decreased proliferation, without activating canonical GPCR signalling or MAPK/ERK, PI3K/AKT, JNK, JAK/HIF-1α, beta catenin or STAT3 pathways. Overexpression upregulated ANTXR1, SLC39A6, HBB, CHRNA, ELMOD1, JAG1 and downregulated DLL4, KIT, CCL15, CYP26B1. ADGRL4/ELTD1 specifically regulates the endothelial tip-cell phenotype through yet undefined signalling pathways.
- Published
- 2021
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22. Functional impact of intramolecular cleavage and dissociation of adhesion G protein-coupled receptor GPR133 (ADGRD1) on canonical signaling.
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Frenster JD, Stephan G, Ravn-Boess N, Bready D, Wilcox J, Kieslich B, Wilde C, Sträter N, Wiggin GR, Liebscher I, Schöneberg T, and Placantonakis DG
- Subjects
- Cyclic AMP metabolism, Glioblastoma metabolism, Humans, Proteolysis, Receptors, G-Protein-Coupled chemistry, Tumor Cells, Cultured, Receptors, G-Protein-Coupled metabolism, Signal Transduction
- Abstract
GPR133 (ADGRD1), an adhesion G protein-coupled receptor (GPCR) whose canonical signaling activates G
αS -mediated generation of cytosolic cAMP, has been shown to be necessary for the growth of glioblastoma (GBM), a brain malignancy. The extracellular N terminus of GPR133 is thought to be autoproteolytically cleaved into N-terminal and C- terminal fragments (NTF and CTF, respectively). However, the role of this cleavage in receptor activation remains unclear. Here, we used subcellular fractionation and immunoprecipitation approaches to show that the WT GPR133 receptor is cleaved shortly after protein synthesis and generates significantly more canonical signaling than an uncleavable point mutant GPR133 (H543R) in patient-derived GBM cultures and HEK293T cells. After cleavage, the resulting NTF and CTF remain noncovalently bound to each other until the receptor is trafficked to the plasma membrane, where we demonstrated NTF-CTF dissociation occurs. Using a fusion of the CTF of GPR133 and the N terminus of thrombin-activated human protease-activated receptor 1 as a controllable proxy system to test the effect of intramolecular cleavage and dissociation, we also showed that thrombin-induced cleavage and shedding of the human protease-activated receptor 1 NTF increased intracellular cAMP levels. These results support a model wherein dissociation of the NTF from the CTF at the plasma membrane promotes GPR133 activation and downstream signaling. These findings add depth to our understanding of the molecular life cycle and mechanism of action of GPR133 and provide critical insights that will inform therapeutic targeting of GPR133 in GBM., Competing Interests: Conflict of interest D. G. P. and NYU Grossman School of Medicine own a patent in the European Union titled “Method for treating high grade glioma” on the use of GPR133 as a treatment target in glioma. D. G. P. has received consultant fees from Tocagen, Synaptive Medical, Monteris, and Robeaute. G. R. W. is an employee and shareholder of Sosei Heptares., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)- Published
- 2021
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23. Mutations in G Protein-Coupled Receptors: Mechanisms, Pathophysiology and Potential Therapeutic Approaches.
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Schöneberg T and Liebscher I
- Subjects
- Humans, Mutation, Phenotype, Receptors, G-Protein-Coupled genetics, Signal Transduction
- Abstract
There are approximately 800 annotated G protein-coupled receptor (GPCR) genes, making these membrane receptors members of the most abundant gene family in the human genome. Besides being involved in manifold physiologic functions and serving as important pharmacotherapeutic targets, mutations in 55 GPCR genes cause about 66 inherited monogenic diseases in humans. Alterations of nine GPCR genes are causatively involved in inherited digenic diseases. In addition to classic gain- and loss-of-function variants, other aspects, such as biased signaling, trans -signaling, ectopic expression, allele variants of GPCRs, pseudogenes, gene fusion, and gene dosage, contribute to the repertoire of GPCR dysfunctions. However, the spectrum of alterations and GPCR involvement is probably much larger because an additional 91 GPCR genes contain homozygous or hemizygous loss-of-function mutations in human individuals with currently unidentified phenotypes. This review highlights the complexity of genomic alteration of GPCR genes as well as their functional consequences and discusses derived therapeutic approaches. SIGNIFICANCE STATEMENT: With the advent of new transgenic and sequencing technologies, the number of monogenic diseases related to G protein-coupled receptor (GPCR) mutants has significantly increased, and our understanding of the functional impact of certain kinds of mutations has substantially improved. Besides the classical gain- and loss-of-function alterations, additional aspects, such as biased signaling, trans -signaling, ectopic expression, allele variants of GPCRs, uniparental disomy, pseudogenes, gene fusion, and gene dosage, need to be elaborated in light of GPCR dysfunctions and possible therapeutic strategies., Competing Interests: Financial disclosure statement: no author has an actual or perceived conflict of interest with the contents of this article., (Copyright © 2020 by The Author(s).)
- Published
- 2021
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24. The repertoire of Adhesion G protein-coupled receptors in adipocytes and their functional relevance.
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Suchý T, Zieschang C, Popkova Y, Kaczmarek I, Weiner J, Liebing AD, Çakir MV, Landgraf K, Gericke M, Pospisilik JA, Körner A, Heiker JT, Dannenberger D, Schiller J, Schöneberg T, Liebscher I, and Thor D
- Subjects
- 3T3-L1 Cells, Animals, Humans, Lipid Metabolism, Lipolysis, Male, Mice, Mice, Inbred C57BL, RNA-Seq, Adipocytes physiology, Adipogenesis, Receptors, G-Protein-Coupled physiology
- Abstract
Background: G protein-coupled receptors (GPCR) are well-characterized regulators of a plethora of physiological functions among them the modulation of adipogenesis and adipocyte function. The class of Adhesion GPCR (aGPCR) and their role in adipose tissue, however, is poorly studied. With respect to the demand for novel targets in obesity treatment, we present a comprehensive study on the expression and function of this enigmatic GPCR class during adipogenesis and in mature adipocytes., Methods: The expression of all aGPCR representatives was determined by reanalyzing RNA-Seq data and by performing qPCR in different mouse and human adipose tissues under low- and high-fat conditions. The impact of aGPCR expression on adipocyte differentiation and lipid accumulation was studied by siRNA-mediated knockdown of all expressed members of this receptor class. The biological characteristics and function of mature adipocytes lacking selected aGPCR were analyzed by mass spectrometry and biochemical methods (lipolysis, glucose uptake, adiponectin secretion)., Results: More than ten aGPCR are significantly expressed in visceral and subcutaneous adipose tissues and several aGPCR are differentially regulated under high-caloric conditions in human and mouse. Receptor knockdown of six receptors resulted in an impaired adipogenesis indicating their expression is essential for proper adipogenesis. The altered lipid composition was studied in more detail for two representatives, ADGRG2/GPR64 and ADGRG6/GPR126. While GPR126 is mainly involved in adipocyte differentiation, GPR64 has an additional role in mature adipocytes by regulating metabolic processes., Conclusions: Adhesion GPCR are significantly involved in qualitative and quantitative adipocyte lipid accumulation and can control lipolysis. Factors driving adipocyte formation and function are governed by signaling pathways induced by aGPCR yielding these receptors potential targets for treating obesity.
- Published
- 2020
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25. Expression profiling of the adhesion G protein-coupled receptor GPR133 (ADGRD1) in glioma subtypes.
- Author
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Frenster JD, Kader M, Kamen S, Sun J, Chiriboga L, Serrano J, Bready D, Golub D, Ravn-Boess N, Stephan G, Chi AS, Kurz SC, Jain R, Park CY, Fenyo D, Liebscher I, Schöneberg T, Wiggin G, Newman R, Barnes M, Dickson JK, MacNeil DJ, Huang X, Shohdy N, Snuderl M, Zagzag D, and Placantonakis DG
- Abstract
Background: Glioma is a family of primary brain malignancies with limited treatment options and in need of novel therapies. We previously demonstrated that the adhesion G protein-coupled receptor GPR133 (ADGRD1) is necessary for tumor growth in adult glioblastoma, the most advanced malignancy within the glioma family. However, the expression pattern of GPR133 in other types of adult glioma is unknown., Methods: We used immunohistochemistry in tumor specimens and non-neoplastic cadaveric brain tissue to profile GPR133 expression in adult gliomas., Results: We show that GPR133 expression increases as a function of WHO grade and peaks in glioblastoma, where all tumors ubiquitously express it. Importantly, GPR133 is expressed within the tumor bulk, as well as in the brain-infiltrating tumor margin. Furthermore, GPR133 is expressed in both isocitrate dehydrogenase (IDH) wild-type and mutant gliomas, albeit at higher levels in IDH wild-type tumors., Conclusion: The fact that GPR133 is absent from non-neoplastic brain tissue but de novo expressed in glioma suggests that it may be exploited therapeutically., (© The Author(s) 2020. Published by Oxford University Press, the Society for Neuro-Oncology and the European Association of Neuro-Oncology.)
- Published
- 2020
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26. The role of ADGRE5/CD97 in human retinal pigment epithelial cell growth and survival.
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Eichler W, Lohrenz A, Simon KU, Krohn S, Lange J, Bürger S, and Liebscher I
- Subjects
- CD55 Antigens metabolism, Cell Adhesion, Cells, Cultured, Humans, Ligands, Signal Transduction, Antigens, CD metabolism, Cell Proliferation, Cell Survival, Receptors, G-Protein-Coupled metabolism, Retinal Pigment Epithelium cytology, Retinal Pigment Epithelium metabolism
- Abstract
Cell surface molecules of retinal pigment epithelial (RPE) cells participate in the pathogenesis of retinal diseases. In an attempt to identify cell surface proteins that play a role in RPE cell-cell interactions, we have considered studying the expression, regulation, and signaling of ADGRE5/CD97, an adhesion G protein-coupled receptor family member, based on its known adhesive function in other cell types such as leukocytes. We showed that RPE cells express three isoforms of CD97 and identified inflammation-related cytokines as important mediators regulating CD97 expression. Whereas TNF-α and IFN-γ upregulated CD97, TGF-β decreased CD97 expression. Due to interaction with CD55, ARPE-19 cells firmly adhered to monocytes and T lymphocytes when overexpressing CD97, suggesting a role for CD97 in controlling leukocyte infiltration across the RPE-based blood-retinal barrier. CD97-mediated signaling acted synergistically with PDGF-BB and IFN-γ to regulate cell growth and survival, ensuring a cellular balance under inflammatory conditions. These findings suggest that CD97 on RPE cells serves to control leukocyte activation and trafficking in uveoretinal inflammation while at the same time regulating second messenger-mediated gene expression, cell growth, and survival., (© 2019 The Authors. Annals of the New York Academy of Sciences published by Wiley Periodicals, Inc. on behalf of New York Academy of Sciences.)
- Published
- 2019
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27. The expanding functional roles and signaling mechanisms of adhesion G protein-coupled receptors.
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Morgan RK, Anderson GR, Araç D, Aust G, Balenga N, Boucard A, Bridges JP, Engel FB, Formstone CJ, Glitsch MD, Gray RS, Hall RA, Hsiao CC, Kim HY, Knierim AB, Kusuluri DK, Leon K, Liebscher I, Piao X, Prömel S, Scholz N, Srivastava S, Thor D, Tolias KF, Ushkaryov YA, Vallon M, Van Meir EG, Vanhollebeke B, Wolfrum U, Wright KM, Monk KR, and Mogha A
- Subjects
- Animals, Humans, Receptors, G-Protein-Coupled chemistry, Receptors, G-Protein-Coupled metabolism, Signal Transduction
- Abstract
The adhesion class of G protein-coupled receptors (GPCRs) is the second largest family of GPCRs (33 members in humans). Adhesion GPCRs (aGPCRs) are defined by a large extracellular N-terminal region that is linked to a C-terminal seven transmembrane (7TM) domain via a GPCR-autoproteolysis inducing (GAIN) domain containing a GPCR proteolytic site (GPS). Most aGPCRs undergo autoproteolysis at the GPS motif, but the cleaved fragments stay closely associated, with the N-terminal fragment (NTF) bound to the 7TM of the C-terminal fragment (CTF). The NTFs of most aGPCRs contain domains known to be involved in cell-cell adhesion, while the CTFs are involved in classical G protein signaling, as well as other intracellular signaling. In this workshop report, we review the most recent findings on the biology, signaling mechanisms, and physiological functions of aGPCRs., (© 2019 New York Academy of Sciences.)
- Published
- 2019
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28. In vivo identification of small molecules mediating Gpr126/Adgrg6 signaling during Schwann cell development.
- Author
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Bradley EC, Cunningham RL, Wilde C, Morgan RK, Klug EA, Letcher SM, Schöneberg T, Monk KR, Liebscher I, and Petersen SC
- Subjects
- Alleles, Animals, Dose-Response Relationship, Drug, Receptors, G-Protein-Coupled genetics, Schwann Cells metabolism, Zebrafish, Zebrafish Proteins genetics, Receptors, G-Protein-Coupled metabolism, Schwann Cells cytology, Signal Transduction drug effects, Small Molecule Libraries pharmacology, Zebrafish Proteins metabolism
- Abstract
Gpr126/Adgrg6, an adhesion family G protein-coupled receptor (aGPCR), is required for the development of myelinating Schwann cells in the peripheral nervous system. Myelin supports and insulates vertebrate axons to permit rapid signal propagation throughout the nervous system. In mammals and zebrafish, mutations in Gpr126 arrest Schwann cells at early developmental stages. We exploited the optical and pharmacological tractability of larval zebrafish to uncover drugs that mediate myelination by activating Gpr126 or functioning in parallel. Using a fluorescent marker of mature myelinating glia (Tg[mbp:EGFP-CAAX]), we screened hypomorphic gpr126 mutant larvae for restoration of myelin basic protein (mbp) expression along peripheral nerves following small molecule treatment. Our screens identified five compounds sufficient to promote mbp expression in gpr126 hypomorphs. Using an allelic series of gpr126 mutants, we parsed the ability of small molecules to restore mbp, suggesting differences in drug efficacy dependent on Schwann cell developmental state. Finally, we identify apomorphine hydrochloride as a direct small molecule activator of Gpr126 using combined in vivo/in vitro assays and show that aporphine class compounds promote Schwann cell development in vivo. Our results demonstrate the utility of in vivo screening for aGPCR modulators and identify small molecules that interact with the gpr126-mediated myelination program., (© 2019 New York Academy of Sciences.)
- Published
- 2019
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29. Genetic basis of functional variability in adhesion G protein-coupled receptors.
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Knierim AB, Röthe J, Çakir MV, Lede V, Wilde C, Liebscher I, Thor D, and Schöneberg T
- Subjects
- Animals, COS Cells, Chlorocebus aethiops, Mice, Organ Specificity, Protein Domains, RNA, Messenger chemistry, RNA, Messenger genetics, RNA, Messenger metabolism, Receptors, G-Protein-Coupled chemistry, Receptors, G-Protein-Coupled metabolism, RNA Splicing, Receptors, G-Protein-Coupled genetics
- Abstract
The enormous sizes of adhesion G protein-coupled receptors (aGPCRs) go along with complex genomic exon-intron architectures giving rise to multiple mRNA variants. There is a need for a comprehensive catalog of aGPCR variants for proper evaluation of the complex functions of aGPCRs found in structural, in vitro and animal model studies. We used an established bioinformatics pipeline to extract, quantify and visualize mRNA variants of aGPCRs from deeply sequenced transcriptomes. Data analysis showed that aGPCRs have multiple transcription start sites even within introns and that tissue-specific splicing is frequent. On average, 19 significantly expressed transcript variants are derived from a given aGPCR gene. The domain architecture of the N terminus encoded by transcript variants often differs and N termini without or with an incomplete seven-helix transmembrane anchor as well as separate seven-helix transmembrane domains are frequently derived from aGPCR genes. Experimental analyses of selected aGPCR transcript variants revealed marked functional differences. Our analysis has an impact on a rational design of aGPCR constructs for structural analyses and gene-deficient mouse lines and provides new support for independent functions of both, the large N terminus and the transmembrane domain of aGPCRs.
- Published
- 2019
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30. The Adhesion G Protein-Coupled Receptor GPR97/ ADGRG3 Is Expressed in Human Granulocytes and Triggers Antimicrobial Effector Functions.
- Author
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Hsiao CC, Chu TY, Wu CJ, van den Biggelaar M, Pabst C, Hébert J, Kuijpers TW, Scicluna BP, I KY, Chen TC, Liebscher I, Hamann J, and Lin HH
- Subjects
- Antibodies, Monoclonal metabolism, Cells, Cultured, Cyclic AMP metabolism, Eosinophils metabolism, Humans, Inflammation metabolism, Mitogen-Activated Protein Kinases metabolism, NF-kappa B metabolism, Neutrophils metabolism, Phosphorylation physiology, Reactive Oxygen Species metabolism, Signal Transduction physiology, Anti-Infective Agents metabolism, Granulocytes metabolism, Receptors, G-Protein-Coupled metabolism
- Abstract
The adhesion family of G protein-coupled receptors (aGPCRs) comprises 33 members in human, several of which are distinctly expressed and functionally involved in polymorphonuclear cells (PMNs). As former work indicated the possible presence of the aGPCR GPR97 in granulocytes, we studied its cellular distribution, molecular structure, signal transduction, and biological function in PMNs. RNA sequencing and mass-spectrometry revealed abundant RNA and protein expression of ADGRG3/GPR97 in granulocyte precursors and terminally differentiated neutrophilic, eosinophilic, and basophilic granulocytes. Using a newly generated GPR97-specific monoclonal antibody, we confirmed that endogenous GPR97 is a proteolytically processed, dichotomous, N-glycosylated receptor. GPR97 was detected in tissue-infiltrating PMNs and upregulated during systemic inflammation. Antibody ligation of GPR97 increased neutrophil reactive oxygen species production and proteolytic enzyme activity, which is accompanied by an increase in mitogen-activated protein kinases and IκBα phosphorylation. In-depth analysis of the GPR97 signaling cascade revealed a possible switch from basal Gαs/cAMP-mediated signal transduction to a Gαi-induced reduction in cAMP levels upon mutation-induced activation of the receptor, in combination with an increase in downstream effectors of Gβγ, such as SRE and NF-κB. Finally, ligation of GPR97 increased the bacteria uptake and killing activity of neutrophils. We conclude that the specific presence of GPR97 regulates antimicrobial activity in human granulocytes.
- Published
- 2018
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31. Mechano-Dependent Phosphorylation of the PDZ-Binding Motif of CD97/ADGRE5 Modulates Cellular Detachment.
- Author
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Hilbig D, Sittig D, Hoffmann F, Rothemund S, Warmt E, Quaas M, Stürmer J, Seiler L, Liebscher I, Hoang NA, Käs JA, Banks L, and Aust G
- Subjects
- Humans, Phosphorylation, Protein Binding, Antigens, CD metabolism, PDZ Domains physiology, Receptors, G-Protein-Coupled metabolism
- Abstract
Cells respond to mechanical stimuli with altered signaling networks. Here, we show that mechanical forces rapidly induce phosphorylation of CD97/ADGRE5 (pCD97) at its intracellular C-terminal PDZ-binding motif (PBM). Biochemically, this phosphorylation disrupts CD97 binding to PDZ domains of the scaffold protein DLG1. In shear-stressed cells, pCD97 appears not only in junctions, retracting fibers, and the attachment area but also in lost membrane patches, demonstrating (intra)cellular detachment at the CD97 PBM. This motif is critical for the CD97-dependent mechanoresponse. Cells expressing CD97 without the PBM are more deformable, and under shear stress, these cells lose cell contacts faster and show changes in the actin cytoskeleton when compared with cells expressing full-length CD97. Our data indicate CD97 linkage to the cytoskeleton. Consistently, CD97 knockout phenocopies CD97 without the PBM, and membranous CD97 is organized in an F-actin-dependent manner. In summary, CD97 shapes the cellular mechanoresponse through signaling modulation via its PBM., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2018
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32. Activation of Adhesion G Protein-coupled Receptors: AGONIST SPECIFICITY OF STACHEL SEQUENCE-DERIVED PEPTIDES.
- Author
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Demberg LM, Winkler J, Wilde C, Simon KU, Schön J, Rothemund S, Schöneberg T, Prömel S, and Liebscher I
- Subjects
- Amino Acid Sequence, Animals, COS Cells, Chickens, Chlorocebus aethiops, HEK293 Cells, Humans, Mice, Mutation, Phylogeny, Protein Domains, Receptors, G-Protein-Coupled chemistry, Receptors, G-Protein-Coupled genetics, Signal Transduction drug effects, Peptides chemistry, Peptides pharmacology, Receptors, G-Protein-Coupled agonists, Receptors, G-Protein-Coupled metabolism
- Abstract
Members of the adhesion G protein-coupled receptor (aGPCR) family carry an agonistic sequence within their large ectodomains. Peptides derived from this region, called the Stachel sequence, can activate the respective receptor. As the conserved core region of the Stachel sequence is highly similar between aGPCRs, the agonist specificity of Stachel sequence-derived peptides was tested between family members using cell culture-based second messenger assays. Stachel peptides derived from aGPCRs of subfamily VI (GPR110/ADGRF1, GPR116/ADGRF5) and subfamily VIII (GPR64/ADGRG2, GPR126/ADGRG6) are able to activate more than one member of the respective subfamily supporting their evolutionary relationship and defining them as pharmacological receptor subtypes. Extended functional analyses of the Stachel sequences and derived peptides revealed agonist promiscuity, not only within, but also between aGPCR subfamilies. For example, the Stachel -derived peptide of GPR110 (subfamily VI) can activate GPR64 and GPR126 (both subfamily VIII). Our results indicate that key residues in the Stachel sequence are very similar between aGPCRs allowing for agonist promiscuity of several Stachel -derived peptides. Therefore, aGPCRs appear to be pharmacologically more closely related than previously thought. Our findings have direct implications for many aGPCR studies, as potential functional overlap has to be considered for in vitro and in vivo studies. However, it also offers the possibility of a broader use of more potent peptides when the original Stachel sequence is less effective., (© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)
- Published
- 2017
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33. Functional relevance of naturally occurring mutations in adhesion G protein-coupled receptor ADGRD1 (GPR133).
- Author
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Fischer L, Wilde C, Schöneberg T, and Liebscher I
- Subjects
- Amino Acid Substitution, Animals, Asymptomatic Diseases, Body Height genetics, COS Cells, Chlorocebus aethiops, Databases, Genetic, Exons, Gene Expression, Genome-Wide Association Study, HEK293 Cells, Heart Rate genetics, Humans, Genome, Human, Mutation, Polymorphism, Single Nucleotide, Receptors, G-Protein-Coupled genetics
- Abstract
Background: A large number of human inherited and acquired diseases and phenotypes are caused by mutations in G protein-coupled receptors (GPCR). Genome-wide association studies (GWAS) have shown that variations in the ADGRD1 (GPR133) locus are linked with differences in metabolism, human height and heart frequency. ADGRD1 is a Gs protein-coupled receptor belonging to the class of adhesion GPCRs., Results: Analysis of more than 1000 sequenced human genomes revealed approximately 9000 single nucleotide polymorphisms (SNPs) in the human ADGRD1 as listed in public data bases. Approximately 2.4 % of these SNPs are located in exons resulting in 129 non-synonymous SNPs (nsSNPs) at 119 positions of ADGRD1. However, the functional relevance of those variants is unknown. In-depth characterization of these amino acid changes revealed several nsSNPs (A448D, Q600stop, C632fs [frame shift], A761E, N795K) causing full or partial loss of receptor function, while one nsSNP (F383S) significantly increased basal activity of ADGRD1., Conclusion: Our results show that a broad spectrum of functionally relevant ADGRD1 variants is present in the human population which may cause clinically relevant phenotypes, while being compatible with life when heterozygous.
- Published
- 2016
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34. The constitutive activity of the adhesion GPCR GPR114/ADGRG5 is mediated by its tethered agonist.
- Author
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Wilde C, Fischer L, Lede V, Kirchberger J, Rothemund S, Schöneberg T, and Liebscher I
- Subjects
- Amino Acid Sequence, Animals, COS Cells, Chlorocebus aethiops, Mice, Multigene Family, Mutation, Protein Isoforms, Receptors, G-Protein-Coupled genetics, Tissue Distribution, Gene Expression Regulation physiology, Receptors, G-Protein-Coupled metabolism
- Abstract
Adhesion GPCRs (aGPCRs) form the second largest, yet most enigmatic class of the GPCR superfamily. Although the physiologic importance of aGPCRs was demonstrated in several studies, the majority of these receptors is still orphan with respect to their agonists and signal transduction. Recent studies reported that aGPCRs are activated through a tethered peptide agonist, coined the Stachel sequence. The Stachel sequence is the most C-terminal part of the highly conserved GPCR autoproteolysis-inducing domain. Here, we used cell culture-based assays to investigate 2 natural splice variants within the Stachel sequence of the orphan Gs coupling aGPCR GPR114/ADGRG5. There is 1 variant constitutively active in cAMP assays (∼25-fold over empty vector) and sensitive to mechano-activation. The other variant has low basal activity in cAMP assays (6-fold over empty vector) and is insensitive to mechano-activation. In-depth mutagenesis studies of these functional differences revealed that the N-terminal half of the Stachel sequence confers the agonistic activity, whereas the C-terminal part orientates the agonistic core sequence to the transmembrane domain. Sequence comparison and functional testing suggest that the proposed mechanism of Stachel-mediated activation is relevant not only to GPR114 but to aGPCRs in general., (© FASEB.)
- Published
- 2016
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35. Tethered Agonism: A Common Activation Mechanism of Adhesion GPCRs.
- Author
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Liebscher I and Schöneberg T
- Subjects
- Animals, Binding Sites, Cell Membrane metabolism, Humans, Models, Molecular, Peptides chemical synthesis, Protein Binding, Protein Interaction Domains and Motifs, Receptors, G-Protein-Coupled chemistry, Receptors, G-Protein-Coupled metabolism, Signal Transduction, Structure-Activity Relationship, Cell Adhesion drug effects, Cell Membrane drug effects, Peptides pharmacology, Receptors, G-Protein-Coupled agonists
- Abstract
Adhesion GPCRs harbor a tethered agonist sequence (reproduced from [24]) As the past years have seen a magnificent increase in knowledge on adhesion GPCR (aGPCR) signal transduction, the time had come to fill the gap on how these receptors can be activated. Based on experimental observations that deletion of the ectodomain can induce signaling, the idea arose that aGPCRs, just like other atypical GPCRs, may harbor a tethered agonist sequence. In this chapter, we describe the recent findings and characteristics of this agonist, called the Stachel sequence, and discuss potential mechanisms that cause liberation of this encrypted sequence. Further, we provide perspectives for application of Stachel-derived synthetic peptides in future studies of aGPCR function.
- Published
- 2016
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36. How to wake a giant.
- Author
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Liebscher I, Monk KR, and Schöneberg T
- Subjects
- Amino Acid Motifs, Animals, Extracellular Matrix metabolism, Humans, Neoplasms metabolism, Protein Binding, Protein Structure, Tertiary, Signal Transduction, Zebrafish, Receptors, G-Protein-Coupled metabolism
- Published
- 2015
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37. Adhesion G Protein-Coupled Receptors: From In Vitro Pharmacology to In Vivo Mechanisms.
- Author
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Monk KR, Hamann J, Langenhan T, Nijmeijer S, Schöneberg T, and Liebscher I
- Subjects
- Animals, Humans, Protein Binding, Receptors, G-Protein-Coupled agonists, Receptors, G-Protein-Coupled chemistry, Receptors, Peptide agonists, Receptors, Peptide chemistry, Signal Transduction, Cell Adhesion, Receptors, G-Protein-Coupled metabolism, Receptors, Peptide metabolism
- Abstract
The adhesion family of G protein-coupled receptors (aGPCRs) comprises 33 members in humans. aGPCRs are characterized by their enormous size and complex modular structures. While the physiologic importance of many aGPCRs has been clearly demonstrated in recent years, the underlying molecular functions have only recently begun to be elucidated. In this minireview, we present an overview of our current knowledge on aGPCR activation and signal transduction with a focus on the latest findings regarding the interplay between ligand binding, mechanical force, and the tethered agonistic Stachel sequence, as well as implications on translational approaches that may derive from understanding aGPCR pharmacology., (Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.)
- Published
- 2015
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38. Identification of the tethered peptide agonist of the adhesion G protein-coupled receptor GPR64/ADGRG2.
- Author
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Demberg LM, Rothemund S, Schöneberg T, and Liebscher I
- Subjects
- Amino Acid Sequence, Animals, COS Cells, Chlorocebus aethiops, Epididymis metabolism, Fertility physiology, Male, Mice, Molecular Sequence Data, Oligopeptides genetics, Oligopeptides metabolism, Peptides genetics, Receptors, G-Protein-Coupled genetics, Receptors, G-Protein-Coupled metabolism, Recombinant Fusion Proteins genetics, Recombinant Fusion Proteins metabolism, Sequence Homology, Amino Acid, Signal Transduction, Peptides metabolism, Receptors, G-Protein-Coupled agonists
- Abstract
The epididymis-specific adhesion G protein-coupled receptor (aGPCR) GPR64/ADGRG2 has been shown to be a key-player in the male reproductive system. As its disruption leads to infertility, GPR64 has drawn attention as potential target for male fertility control or improvement. Like the majority of aGPCRs GPR64 is an orphan receptor regarding its endogenous agonist and signal transduction. In this study we examined the G protein-coupling abilities of GPR64 and showed that it is activated through a tethered agonist sequence, which we have previously identified as the Stachel sequence. Synthetic peptides derived from the Stachel region can activate the receptor, opening for the first time the possibility to externally manipulate the receptor activity., (Copyright © 2015 Elsevier Inc. All rights reserved.)
- Published
- 2015
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39. Tethered agonists: a new mechanism underlying adhesion G protein-coupled receptor activation.
- Author
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Schöneberg T, Liebscher I, Luo R, Monk KR, and Piao X
- Subjects
- Animals, Cell Adhesion Molecules ultrastructure, Computer Simulation, Humans, Membrane Proteins ultrastructure, Models, Biological, Models, Chemical, Receptors, G-Protein-Coupled ultrastructure, Structure-Activity Relationship, Cell Adhesion Molecules chemistry, Cell Adhesion Molecules physiology, Membrane Proteins chemistry, Membrane Proteins physiology, Receptors, G-Protein-Coupled chemistry, Receptors, G-Protein-Coupled physiology
- Abstract
The family of adhesion G protein-coupled receptors (aGPCRs) comprises 33 members in the human genome, which are subdivided into nine subclasses. Many aGPCRs undergo an autoproteolytic process via their GPCR Autoproteolysis-INducing (GAIN) domain during protein maturation to generate an N- and a C-terminal fragments, NTF and CTF, respectively. The NTF and CTF are non-covalently reassociated on the plasma membrane to form a single receptor unit. How aGPCRs are activated upon ligand binding remains one of the leading questions in the field of aGPCR research. Recent work from our labs and others shows that ligand binding can remove the NTF from the plasma membrane-bound CTF, exposing a tethered agonist which potently activates downstream signaling.
- Published
- 2015
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40. The adhesion GPCR GPR126 has distinct, domain-dependent functions in Schwann cell development mediated by interaction with laminin-211.
- Author
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Petersen SC, Luo R, Liebscher I, Giera S, Jeong SJ, Mogha A, Ghidinelli M, Feltri ML, Schöneberg T, Piao X, and Monk KR
- Subjects
- Animals, Animals, Genetically Modified, Animals, Newborn, COS Cells, Cells, Cultured, Chlorocebus aethiops, Embryo, Mammalian, Embryo, Nonmammalian, Ganglia, Spinal cytology, Humans, In Vitro Techniques, Laminin genetics, Larva, Mice, Mice, Inbred C57BL, Models, Molecular, Morpholinos pharmacology, Myelin Sheath ultrastructure, Neuroglia metabolism, Neuroglia ultrastructure, Protein Binding drug effects, Protein Binding genetics, Receptors, G-Protein-Coupled chemistry, Receptors, G-Protein-Coupled genetics, Schwann Cells ultrastructure, Zebrafish, Zebrafish Proteins genetics, Zebrafish Proteins metabolism, Laminin metabolism, Myelin Sheath metabolism, Receptors, G-Protein-Coupled metabolism, Schwann Cells metabolism
- Abstract
Myelin ensheathes axons to allow rapid propagation of action potentials and proper nervous system function. In the peripheral nervous system, Schwann cells (SCs) radially sort axons into a 1:1 relationship before wrapping an axonal segment to form myelin. SC myelination requires the adhesion G protein-coupled receptor GPR126, which undergoes autoproteolytic cleavage into an N-terminal fragment (NTF) and a seven-transmembrane-containing C-terminal fragment (CTF). Here we show that GPR126 has domain-specific functions in SC development whereby the NTF is necessary and sufficient for axon sorting, whereas the CTF promotes wrapping through cAMP elevation. These biphasic roles of GPR126 are governed by interactions with Laminin-211, which we define as a novel ligand for GPR126 that modulates receptor signaling via a tethered agonist. Our work suggests a model in which Laminin-211 mediates GPR126-induced cAMP levels to control early and late stages of SC development., (Copyright © 2015 Elsevier Inc. All rights reserved.)
- Published
- 2015
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41. A Tethered Agonist within the Ectodomain Activates the Adhesion G Protein-Coupled Receptors GPR126 and GPR133.
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Liebscher I, Schön J, Petersen SC, Fischer L, Auerbach N, Demberg LM, Mogha A, Cöster M, Simon KU, Rothemund S, Monk KR, and Schöneberg T
- Published
- 2015
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42. International Union of Basic and Clinical Pharmacology. XCIV. Adhesion G protein-coupled receptors.
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Hamann J, Aust G, Araç D, Engel FB, Formstone C, Fredriksson R, Hall RA, Harty BL, Kirchhoff C, Knapp B, Krishnan A, Liebscher I, Lin HH, Martinelli DC, Monk KR, Peeters MC, Piao X, Prömel S, Schöneberg T, Schwartz TW, Singer K, Stacey M, Ushkaryov YA, Vallon M, Wolfrum U, Wright MW, Xu L, Langenhan T, and Schiöth HB
- Subjects
- Animals, Cell Adhesion, Cell Adhesion Molecules chemistry, Cell Membrane enzymology, Cell Membrane metabolism, Cell Movement, Humans, International Agencies, Ligands, Pharmacology trends, Pharmacology, Clinical trends, Protein Isoforms agonists, Protein Isoforms chemistry, Protein Isoforms classification, Protein Isoforms metabolism, Receptors, G-Protein-Coupled agonists, Receptors, G-Protein-Coupled chemistry, Receptors, G-Protein-Coupled classification, Signal Transduction, Societies, Scientific, Terminology as Topic, Cell Adhesion Molecules metabolism, Cyclic AMP physiology, Models, Molecular, Receptors, G-Protein-Coupled metabolism, Second Messenger Systems
- Abstract
The Adhesion family forms a large branch of the pharmacologically important superfamily of G protein-coupled receptors (GPCRs). As Adhesion GPCRs increasingly receive attention from a wide spectrum of biomedical fields, the Adhesion GPCR Consortium, together with the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification, proposes a unified nomenclature for Adhesion GPCRs. The new names have ADGR as common dominator followed by a letter and a number to denote each subfamily and subtype, respectively. The new names, with old and alternative names within parentheses, are: ADGRA1 (GPR123), ADGRA2 (GPR124), ADGRA3 (GPR125), ADGRB1 (BAI1), ADGRB2 (BAI2), ADGRB3 (BAI3), ADGRC1 (CELSR1), ADGRC2 (CELSR2), ADGRC3 (CELSR3), ADGRD1 (GPR133), ADGRD2 (GPR144), ADGRE1 (EMR1, F4/80), ADGRE2 (EMR2), ADGRE3 (EMR3), ADGRE4 (EMR4), ADGRE5 (CD97), ADGRF1 (GPR110), ADGRF2 (GPR111), ADGRF3 (GPR113), ADGRF4 (GPR115), ADGRF5 (GPR116, Ig-Hepta), ADGRG1 (GPR56), ADGRG2 (GPR64, HE6), ADGRG3 (GPR97), ADGRG4 (GPR112), ADGRG5 (GPR114), ADGRG6 (GPR126), ADGRG7 (GPR128), ADGRL1 (latrophilin-1, CIRL-1, CL1), ADGRL2 (latrophilin-2, CIRL-2, CL2), ADGRL3 (latrophilin-3, CIRL-3, CL3), ADGRL4 (ELTD1, ETL), and ADGRV1 (VLGR1, GPR98). This review covers all major biologic aspects of Adhesion GPCRs, including evolutionary origins, interaction partners, signaling, expression, physiologic functions, and therapeutic potential., (Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.)
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- 2015
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- View/download PDF
43. A tethered agonist within the ectodomain activates the adhesion G protein-coupled receptors GPR126 and GPR133.
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Liebscher I, Schön J, Petersen SC, Fischer L, Auerbach N, Demberg LM, Mogha A, Cöster M, Simon KU, Rothemund S, Monk KR, and Schöneberg T
- Subjects
- Amino Acid Sequence, Animals, Binding Sites, COS Cells, Chlorocebus aethiops, Humans, Molecular Sequence Data, Oligopeptides chemistry, Protein Binding, Receptors, G-Protein-Coupled chemistry, Receptors, G-Protein-Coupled metabolism, Zebrafish, Oligopeptides pharmacology, Receptors, G-Protein-Coupled agonists
- Abstract
Adhesion G protein-coupled receptors (aGPCRs) comprise the second largest yet least studied class of the GPCR superfamily. aGPCRs are involved in many developmental processes and immune and synaptic functions, but the mode of their signal transduction is unclear. Here, we show that a short peptide sequence (termed the Stachel sequence) within the ectodomain of two aGPCRs (GPR126 and GPR133) functions as a tethered agonist. Upon structural changes within the receptor ectodomain, this intramolecular agonist is exposed to the seven-transmembrane helix domain, which triggers G protein activation. Our studies show high specificity of a given Stachel sequence for its receptor. Finally, the function of Gpr126 is abrogated in zebrafish with a mutated Stachel sequence, and signaling is restored in hypomorphic gpr126 zebrafish mutants upon exogenous Stachel peptide application. These findings illuminate a mode of aGPCR activation and may prompt the development of specific ligands for this currently untargeted GPCR family., (Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2014
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44. New functions and signaling mechanisms for the class of adhesion G protein-coupled receptors.
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Liebscher I, Ackley B, Araç D, Ariestanti DM, Aust G, Bae BI, Bista BR, Bridges JP, Duman JG, Engel FB, Giera S, Goffinet AM, Hall RA, Hamann J, Hartmann N, Lin HH, Liu M, Luo R, Mogha A, Monk KR, Peeters MC, Prömel S, Ressl S, Schiöth HB, Sigoillot SM, Song H, Talbot WS, Tall GG, White JP, Wolfrum U, Xu L, and Piao X
- Subjects
- Animals, Developmental Disabilities genetics, Humans, Mutation, Neoplasms genetics, Signal Transduction, Synapses physiology, Cell Adhesion, Receptors, G-Protein-Coupled physiology
- Abstract
The class of adhesion G protein-coupled receptors (aGPCRs), with 33 human homologs, is the second largest family of GPCRs. In addition to a seven-transmembrane α-helix-a structural feature of all GPCRs-the class of aGPCRs is characterized by the presence of a large N-terminal extracellular region. In addition, all aGPCRs but one (GPR123) contain a GPCR autoproteolysis-inducing (GAIN) domain that mediates autoproteolytic cleavage at the GPCR autoproteolysis site motif to generate N- and a C-terminal fragments (NTF and CTF, respectively) during protein maturation. Subsequently, the NTF and CTF are associated noncovalently as a heterodimer at the plasma membrane. While the biological function of the GAIN domain-mediated autocleavage is not fully understood, mounting evidence suggests that the NTF and CTF possess distinct biological activities in addition to their function as a receptor unit. We discuss recent advances in understanding the biological functions, signaling mechanisms, and disease associations of the aGPCRs., (© 2014 New York Academy of Sciences.)
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- 2014
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45. Combined newborn screening for familial hemophagocytic lymphohistiocytosis and severe T- and B-cell immunodeficiencies.
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Borte S, Meeths M, Liebscher I, Krist K, Nordenskjöld M, Hammarström L, von Döbeln U, Henter JI, and Bryceson YT
- Subjects
- B-Lymphocytes immunology, Dried Blood Spot Testing, Early Diagnosis, Humans, Immunologic Deficiency Syndromes genetics, Immunologic Deficiency Syndromes immunology, Immunologic Deficiency Syndromes pathology, Infant, Newborn, Lymphohistiocytosis, Hemophagocytic genetics, Lymphohistiocytosis, Hemophagocytic immunology, Lymphohistiocytosis, Hemophagocytic pathology, Neonatal Screening methods, Sequence Inversion, T-Lymphocytes immunology, B-Lymphocytes pathology, Immunologic Deficiency Syndromes diagnosis, Lymphohistiocytosis, Hemophagocytic diagnosis, Membrane Proteins genetics, T-Lymphocytes pathology
- Published
- 2014
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46. Gpr126 functions in Schwann cells to control differentiation and myelination via G-protein activation.
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Mogha A, Benesh AE, Patra C, Engel FB, Schöneberg T, Liebscher I, and Monk KR
- Subjects
- Animals, COS Cells, Chlorocebus aethiops, Female, GTP-Binding Proteins physiology, Humans, Male, Mice, Mice, 129 Strain, Mice, Inbred C57BL, Mice, Knockout, Myelin Sheath ultrastructure, Schwann Cells ultrastructure, Signal Transduction physiology, Cell Differentiation physiology, Myelin Sheath metabolism, Receptors, G-Protein-Coupled physiology, Schwann Cells metabolism
- Abstract
The myelin sheath surrounding axons ensures that nerve impulses travel quickly and efficiently, allowing for the proper function of the vertebrate nervous system. We previously showed that the adhesion G-protein-coupled receptor (aGPCR) Gpr126 is essential for peripheral nervous system myelination, although the molecular mechanisms by which Gpr126 functions were incompletely understood. aGPCRs are a significantly understudied protein class, and it was unknown whether Gpr126 couples to G-proteins. Here, we analyze Dhh(Cre);Gpr126(fl/fl) conditional mutants, and show that Gpr126 functions in Schwann cells (SCs) for radial sorting of axons and myelination. Furthermore, we demonstrate that elevation of cAMP levels or protein kinase A activation suppresses myelin defects in Gpr126 mouse mutants and that cAMP levels are reduced in conditional Gpr126 mutant peripheral nerve. Finally, we show that GPR126 directly increases cAMP by coupling to heterotrimeric G-proteins. Together, these data support a model in which Gpr126 functions in SCs for proper development and myelination and provide evidence that these functions are mediated via G-protein-signaling pathways.
- Published
- 2013
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- View/download PDF
47. Progress in demystification of adhesion G protein-coupled receptors.
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Liebscher I, Schöneberg T, and Prömel S
- Subjects
- Animals, Cell Adhesion, Humans, Receptors, G-Protein-Coupled analysis, Signal Transduction, Receptors, G-Protein-Coupled metabolism
- Abstract
Adhesion G protein-coupled receptors (aGPCR) form the second largest class of GPCR. They are phylogenetically old and have been highly conserved during evolution. Mutations in representatives of this class are associated with severe diseases such as Usher Syndrome, a combined congenital deaf-blindness, or bifrontal parietal polymicrogyria. The main characteristics of aGPCR are their enormous size and the complexity of their N termini. They contain a highly conserved GPCR proteolytic site (GPS) and several functional domains that have been implicated in cell-cell and cell-matrix interactions. Adhesion GPCR have been proposed to serve a dual function as adhesion molecules and as classical receptors. However, until recently there was no proof that aGPCR indeed couple to G proteins or even function as classical receptors. In this review, we have summarized and discussed recent evidence that aGPCR present many functional features of classical GPCR, including multiple G protein-coupling abilities, G protein-independent signaling and oligomerization, but also specific signaling properties only found in aGPCR.
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- 2013
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48. Dissecting signaling and functions of adhesion G protein-coupled receptors.
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Araç D, Aust G, Calebiro D, Engel FB, Formstone C, Goffinet A, Hamann J, Kittel RJ, Liebscher I, Lin HH, Monk KR, Petrenko A, Piao X, Prömel S, Schiöth HB, Schwartz TW, Stacey M, Ushkaryov YA, Wobus M, Wolfrum U, Xu L, and Langenhan T
- Subjects
- Cell Adhesion, Humans, Ligands, Models, Biological, Proteolysis, Receptors, G-Protein-Coupled genetics, Receptors, G-Protein-Coupled metabolism, Signal Transduction
- Abstract
G protein-coupled receptors (GPCRs) comprise an expanded superfamily of receptors in the human genome. Adhesion class G protein-coupled receptors (adhesion-GPCRs) form the second largest class of GPCRs. Despite the abundance, size, molecular structure, and functions in facilitating cell and matrix contacts in a variety of organ systems, adhesion-GPCRs are by far the most poorly understood GPCR class. Adhesion-GPCRs possess a unique molecular structure, with extended N-termini containing various adhesion domains. In addition, many adhesion-GPCRs are autoproteolytically cleaved into an N-terminal fragment (NTF, NT, α-subunit) and C-terminal fragment (CTF, CT, β-subunit) at a conserved GPCR autoproteolysis-inducing (GAIN) domain that contains a GPCR proteolysis site (GPS). These two features distinguish adhesion-GPCRs from other GPCR classes. Though active research on adhesion-GPCRs in diverse areas, such as immunity, neuroscience, and development and tumor biology has been intensified in the recent years, the general biological and pharmacological properties of adhesion-GPCRs are not well known, and they have not yet been used for biomedical purposes. The "6th International Adhesion-GPCR Workshop," held at the Institute of Physiology of the University of Würzburg on September 6-8, 2012, assembled a majority of the investigators currently actively pursuing research on adhesion-GPCRs, including scientists from laboratories in Europe, the United States, and Asia. The meeting featured the nascent mechanistic understanding of the molecular events driving the signal transduction of adhesion-GPCRs, novel models to evaluate their functions, and evidence for their involvement in human disease., (© 2012 New York Academy of Sciences.)
- Published
- 2012
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49. The ligand specificity of the G-protein-coupled receptor GPR34.
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Ritscher L, Engemaier E, Stäubert C, Liebscher I, Schmidt P, Hermsdorf T, Römpler H, Schulz A, and Schöneberg T
- Subjects
- Cells, Cultured, Humans, Ligands, Likelihood Functions, Receptors, Lysophospholipid metabolism
- Abstract
Lyso-PS (lyso-phosphatidylserine) has been shown to activate the G(i/o)-protein-coupled receptor GPR34. Since in vitro and in vivo studies provided controversial results in assigning lyso-PS as the endogenous agonist for GPR34, we investigated the evolutionary conservation of agonist specificity in more detail. Except for some fish GPR34 subtypes, lyso-PS has no or very weak agonistic activity at most vertebrate GPR34 orthologues investigated. Using chimaeras we identified single positions in the second extracellular loop and the transmembrane helix 5 of carp subtype 2a that, if transferred to the human orthologue, enabled lyso-PS to activate the human GPR34. Significant improvement of agonist efficacy by changing only a few positions strongly argues against the hypothesis that nature optimized GPR34 as the receptor for lyso-PS. Phylogenetic analysis revealed several positions in some fish GPR34 orthologues which are under positive selection. These structural changes may indicate functional specification of these orthologues which can explain the species- and subtype-specific pharmacology of lyso-PS. Furthermore, we identified aminoethyl-carbamoyl ATP as an antagonist of carp GPR34, indicating ligand promiscuity with non-lipid compounds. The results of the present study suggest that lyso-PS has only a random agonistic activity at some GPR34 orthologues and the search for the endogenous agonist should consider additional chemical entities.
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- 2012
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50. Altered immune response in mice deficient for the G protein-coupled receptor GPR34.
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Liebscher I, Müller U, Teupser D, Engemaier E, Engel KM, Ritscher L, Thor D, Sangkuhl K, Ricken A, Wurm A, Piehler D, Schmutzler S, Fuhrmann H, Albert FW, Reichenbach A, Thiery J, Schöneberg T, and Schulz A
- Subjects
- Animals, Cattle, Cryptococcosis metabolism, Cytokines biosynthesis, Cytokines genetics, Cytokines immunology, Granulocytes metabolism, Hypersensitivity, Delayed genetics, Hypersensitivity, Delayed metabolism, Immunization, Macrophages immunology, Mice, Mice, Knockout, Pneumonia metabolism, Receptors, Lysophospholipid genetics, Receptors, Lysophospholipid metabolism, Serum Albumin, Bovine immunology, Serum Albumin, Bovine pharmacology, X Chromosome genetics, X Chromosome immunology, X Chromosome metabolism, Cryptococcosis immunology, Cryptococcus neoformans immunology, Granulocytes immunology, Hypersensitivity, Delayed immunology, Macrophages metabolism, Pneumonia immunology, Receptors, Lysophospholipid immunology
- Abstract
The X-chromosomal GPR34 gene encodes an orphan G(i) protein-coupled receptor that is highly conserved among vertebrates. To evaluate the physiological relevance of GPR34, we generated a GPR34-deficient mouse line. GPR34-deficient mice were vital, reproduced normally, and showed no gross abnormalities in anatomical, histological, laboratory chemistry, or behavioral investigations under standard housing. Because GPR34 is highly expressed in mononuclear cells of the immune system, mice were specifically tested for altered functions of these cell types. Following immunization with methylated BSA, the number of granulocytes and macrophages in spleens was significantly lower in GPR34-deficient mice as in wild-type mice. GPR34-deficient mice showed significantly increased paw swelling in the delayed type hypersensitivity test and higher pathogen burden in extrapulmonary tissues after pulmonary infection with Cryptococcus neoformans compared with wild-type mice. The findings in delayed type hypersensitivity and infection tests were accompanied by significantly different basal and stimulated TNF-α, GM-CSF, and IFN-γ levels in GPR34-deficient animals. Our data point toward a functional role of GPR34 in the cellular response to immunological challenges.
- Published
- 2011
- Full Text
- View/download PDF
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