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Sadee W. Ligand-Free Signaling of G-Protein-Coupled Receptors: Physiology, Pharmacology, and Genetics. Molecules 2023; 28:6375. [PMID: 37687205 PMCID: PMC10489045 DOI: 10.3390/molecules28176375] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 08/28/2023] [Accepted: 08/30/2023] [Indexed: 09/10/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) are ubiquitous sensors and regulators of cellular functions. Each GPCR exists in complex aggregates with multiple resting and active conformations. Designed to detect weak stimuli, GPCRs can also activate spontaneously, resulting in basal ligand-free signaling. Agonists trigger a cascade of events leading to an activated agonist-receptor G-protein complex with high agonist affinity. However, the ensuing signaling process can further remodel the receptor complex to reduce agonist affinity, causing rapid ligand dissociation. The acutely activated ligand-free receptor can continue signaling, as proposed for rhodopsin and μ opioid receptors, resulting in robust receptor activation at low agonist occupancy with enhanced agonist potency. Continued receptor stimulation can further modify the receptor complex, regulating sustained ligand-free signaling-proposed to play a role in opioid dependence. Basal, acutely agonist-triggered, and sustained elevated ligand-free signaling could each have distinct functions, reflecting multi-state conformations of GPCRs. This review addresses basal and stimulus-activated ligand-free signaling, its regulation, genetic factors, and pharmacological implications, focusing on opioid and serotonin receptors, and the growth hormone secretagogue receptor (GHSR). The hypothesis is proposed that ligand-free signaling of 5-HT2A receptors mediate therapeutic effects of psychedelic drugs. Research avenues are suggested to close the gaps in our knowledge of ligand-free GPCR signaling.
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Affiliation(s)
- Wolfgang Sadee
- Cancer Biology and Genetics, College of Medicine, The Ohio State University, Columbus, OH 43210, USA;
- Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
- Aether Therapeutics Inc., Austin, TX 78756, USA
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2
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Oncolytic viruses as emerging therapy against cancers including Oncovirus-induced cancers. Eur J Pharmacol 2023; 939:175393. [PMID: 36435236 DOI: 10.1016/j.ejphar.2022.175393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 11/03/2022] [Accepted: 11/14/2022] [Indexed: 11/25/2022]
Abstract
There are several human viruses with known potential for causing cancers including, Hepatitis B virus, Hepatitis C virus, Epstein-Barr virus, Kaposi's sarcoma herpesvirus, Human T-cell lymphotropic virus, Human papillomavirus, and Merkel cell polyomavirus. Cancer is the second leading cause of death that affects humans worldwide, especially in developing countries. Surgery, chemotherapy, and radiotherapy can cure about 60% of humans with cancer but recurrent and metastatic diseases remain a major reason for death. In recent years, understanding the molecular characteristics of cancer cells has led to the improvement of therapeutic strategies using novel emerging therapies. Oncolytic viruses with the potential of lysing cancer cells defined the field of oncolytic virology, hence becoming a biotechnology tool rather than just a cause of disease. This study mainly focused on targeting cell proliferation and death pathways in human tumor-inducing viruses by developing innovative therapies for cancer patients based on the natural oncolytic properties of reovirus. To kill tumor cells efficiently and reduce the chance of recurrence both the direct ability of reovirus infection to lyse the tumor cells and the stimulation of a potent host immune response are applied. Hence, bioengineered stem cells can be used as smart carriers to improve the efficacy of oncolytic reovirus and safety profiles.
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3
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Sojka AC, Brennan KM, Maizels ET, Young CD. The Science Behind G Protein-Coupled Receptors (GPCRs) and Their Accurate Visual Representation in Scientific Research. THE JOURNAL OF BIOCOMMUNICATION 2017; 41:e6. [PMID: 36405408 PMCID: PMC9140105 DOI: 10.5210/jbc.v41i1.7309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
G Protein-Coupled Receptors (GPCRs) are transmembrane (TM) proteins that span the cell membrane seven times, and contain intracellular and extracellular domains, comprised of connecting loops, as well as terminal extension sequences. GPCRs bind ligands within their transmembrane and/or extracellular domains. Ligand binding elicits conformational changes that initiate downstream intracellular signaling events through arrestins and G proteins. GPCRs play central roles in many physiological processes, from sensory to neurological, cardiovascular, endocrine, and reproductive functions. This paper strives to provide an entry point to current GPCR science, and to identify visual approaches to communicate select aspects of GPCR structure and function with clarity and accuracy. The overall GPCR structure, primary sequence and the implications of sequence for membrane topology, ligand binding and helical rearrangements accompanying activation are considered and discussed in the context of visualization strategies, including two-dimensional topological diagrams, three-dimensional representations, and common errors that arise from these representations.
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4
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Zhang J, He S, Wang Y, Brulois K, Lan K, Jung JU, Feng P. Herpesviral G protein-coupled receptors activate NFAT to induce tumor formation via inhibiting the SERCA calcium ATPase. PLoS Pathog 2015; 11:e1004768. [PMID: 25811856 PMCID: PMC4374719 DOI: 10.1371/journal.ppat.1004768] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 02/27/2015] [Indexed: 11/24/2022] Open
Abstract
G protein-coupled receptors (GPCRs) constitute the largest family of proteins that transmit signal to regulate an array of fundamental biological processes. Viruses deploy diverse tactics to hijack and harness intracellular signaling events induced by GPCR. Herpesviruses encode multiple GPCR homologues that are implicated in viral pathogenesis. Cellular GPCRs are primarily regulated by their cognate ligands, while herpesviral GPCRs constitutively activate downstream signaling cascades, including the nuclear factor of activated T cells (NFAT) pathway. However, the roles of NFAT activation and mechanism thereof in viral GPCR tumorigenesis remain unknown. Here we report that GPCRs of human Kaposi’s sarcoma-associated herpesvirus (kGPCR) and cytomegalovirus (US28) shortcut NFAT activation by inhibiting the sarcoplasmic reticulum calcium ATPase (SERCA), which is necessary for viral GPCR tumorigenesis. Biochemical approaches, entailing pharmacological inhibitors and protein purification, demonstrate that viral GPCRs target SERCA2 to increase cytosolic calcium concentration. As such, NFAT activation induced by vGPCRs was exceedingly sensitive to cyclosporine A that targets calcineurin, but resistant to inhibition upstream of ER calcium release. Gene expression profiling identified a signature of NFAT activation in endothelial cells expressing viral GPCRs. The expression of NFAT-dependent genes was up-regulated in tumors derived from tva-kGPCR mouse and human KS. Employing recombinant kGPCR-deficient KSHV, we showed that kGPCR was critical for NFAT-dependent gene expression in KSHV lytic replication. Finally, cyclosporine A treatment diminished NFAT-dependent gene expression and tumor formation induced by viral GPCRs. These findings reveal essential roles of NFAT activation in viral GPCR tumorigenesis and a mechanism of “constitutive” NFAT activation by viral GPCRs. G protein-coupled receptors (GPCRs) constitute the largest family of proteins that transmit signal across plasma membrane. Herpesviral GPCRs (vGPCRs) activate diverse signaling cascades and are implicated in viral pathogenesis (e.g., tumor development). In contrast to cellular GPCRs that are chiefly regulated via cognate ligand-association, vGPCRs are constitutively active independent of ligand-binding. vGPCRs provide useful tools to dissect signal transduction from plasma membrane receptors to nuclear transcription factors. To probe the activation of nuclear factor of T cells (NFAT), we demonstrate that vGPCRs target the ER calcium ATPase to increase cytosolic calcium concentration and activate NFAT. Inhibition of NFAT activation impairs tumor formation induced by vGPCRs, implying the antitumor therapeutic potential via disabling NFAT activation.
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Affiliation(s)
- Junjie Zhang
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Shanping He
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Yi Wang
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Kevin Brulois
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Ke Lan
- Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, P.R. China
| | - Jae U. Jung
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Pinghui Feng
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
- * E-mail:
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5
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Angelova M, Ferris M, Swan KF, McFerrin HE, Pridjian G, Morris CA, Sullivan DE. Kaposi's sarcoma-associated herpesvirus G-protein coupled receptor activates the canonical Wnt/β-catenin signaling pathway. Virol J 2014; 11:218. [PMID: 25514828 PMCID: PMC4304609 DOI: 10.1186/s12985-014-0218-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 11/27/2014] [Indexed: 12/12/2022] Open
Abstract
Background KSHV is a tumorigenic γ-herpesvirus that has been identified as the etiologic agent of Kaposi’s sarcoma (KS), a multifocal highly vascularized neoplasm that is the most common malignancy associated with acquired immunodeficiency syndrome (AIDS). The virus encodes a constitutively active chemokine receptor homologue, vGPCR that possesses potent angiogenic and tumorigenic properties, and is critical for KSHV pathobiology. To date, a number of signaling pathways have been identified as key in mediating vGPCR oncogenic potential. Findings In this study, we identify a novel pathway, the Wnt/β-catenin pathway, which is dysregulated by vGPCR expression in endothelial cells. Expression of vGPCR in endothelial cells enhances the nuclear accumulation of β-catenin, that correlates with an increase in β-catenin transcriptional activity. Activation of β-catenin signaling by vGPCR is dependent on the PI3K/Akt pathway, as treatment of vGPCR-expressing cells with a pharmacological inhibitor of PI3K, leads to a decreased activation of a β-catenin-driven reporter, a significant decrease in expression of β-catenin target genes, and reduced endothelial tube formation. Conclusions Given the critical role of Wnt/β-catenin signaling in angiogenesis and tumorigenesis, the findings from this study suggest a novel mechanism in KSHV-induced malignancies. Electronic supplementary material The online version of this article (doi:10.1186/s12985-014-0218-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Magdalena Angelova
- Department of Microbiology and Immunology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA, USA.
| | - MaryBeth Ferris
- Department of Microbiology and Immunology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA, USA.
| | - Kenneth F Swan
- Department of Obstetrics and Gynecology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA, USA.
| | - Harris E McFerrin
- Biology Department, Xavier University, 1 Drexel Drive, New Orleans, LA, USA.
| | - Gabriella Pridjian
- Department of Obstetrics and Gynecology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA, USA.
| | - Cindy A Morris
- Department of Microbiology and Immunology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA, USA.
| | - Deborah E Sullivan
- Department of Microbiology and Immunology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA, USA.
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6
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Niemann I, Reichel A, Stamminger T. Intracellular trafficking of the human cytomegalovirus-encoded 7-trans-membrane protein homologs pUS27 and pUL78 during viral infection: a comparative analysis. Viruses 2014; 6:661-82. [PMID: 24517969 PMCID: PMC3939477 DOI: 10.3390/v6020661] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 01/09/2014] [Accepted: 01/13/2014] [Indexed: 12/23/2022] Open
Abstract
Human cytomegalovirus (HCMV) encodes four G protein-coupled receptor (GPCR) homologs, termed pUS27, pUS28, pUL33, and pUL78. In contrast to the extensively characterized vGPCRs pUS28 and pUL33, knowledge concerning pUS27 and pUL78 is limited. Previous studies already demonstrated constitutive internalization of pUS27 and pUL78, as well as an association with the endosomal machinery, however, these results were mainly obtained using transiently transfected cells. To explore the subcellular localization of both receptors during viral infection, we constructed recombinant HCMVs expressing tagged vGPCRs. Colocalization analyses revealed a predominant association of pUS27 or pUL78 with the trans-Golgi network or the endoplasmic reticulum, respectively. Intriguingly, our data emphasize that protein sorting is highly regulated by viral functions as we detected dramatic changes in the colocalization of pUS27 and pUL78 with endosomal markers during progression of HCMV replication. Furthermore, we observed cell type-dependent differences in trafficking of both vGPCRs between fibroblasts and epithelial cells. Most importantly, infection experiments with a recombinant HCMV carrying tagged versions of pUS27 and pUL78 simultaneously, revealed that these two proteins do not colocalize during viral infection. This contrasts to results of transient expression experiments. In conclusion, our results highlight the importance to investigate vGPCR trafficking in a viral context.
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Affiliation(s)
- Ina Niemann
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Schlossgarten 4, Erlangen 91054, Germany.
| | - Anna Reichel
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Schlossgarten 4, Erlangen 91054, Germany.
| | - Thomas Stamminger
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Schlossgarten 4, Erlangen 91054, Germany.
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7
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Thompson MD, Cole DEC, Capra V, Siminovitch KA, Rovati GE, Burnham WM, Rana BK. Pharmacogenetics of the G protein-coupled receptors. Methods Mol Biol 2014; 1175:189-242. [PMID: 25150871 DOI: 10.1007/978-1-4939-0956-8_9] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Pharmacogenetics investigates the influence of genetic variants on physiological phenotypes related to drug response and disease, while pharmacogenomics takes a genome-wide approach to advancing this knowledge. Both play an important role in identifying responders and nonresponders to medication, avoiding adverse drug reactions, and optimizing drug dose for the individual. G protein-coupled receptors (GPCRs) are the primary target of therapeutic drugs and have been the focus of these studies. With the advance of genomic technologies, there has been a substantial increase in the inventory of naturally occurring rare and common GPCR variants. These variants include single-nucleotide polymorphisms and insertion or deletions that have potential to alter GPCR expression of function. In vivo and in vitro studies have determined functional roles for many GPCR variants, but genetic association studies that define the physiological impact of the majority of these common variants are still limited. Despite the breadth of pharmacogenetic data available, GPCR variants have not been included in drug labeling and are only occasionally considered in optimizing clinical use of GPCR-targeted agents. In this chapter, pharmacogenetic and genomic studies on GPCR variants are reviewed with respect to a subset of GPCR systems, including the adrenergic, calcium sensing, cysteinyl leukotriene, cannabinoid CB1 and CB2 receptors, and the de-orphanized receptors such as GPR55. The nature of the disruption to receptor function is discussed with respect to regulation of gene expression, expression on the cell surface (affected by receptor trafficking, dimerization, desensitization/downregulation), or perturbation of receptor function (altered ligand binding, G protein coupling, constitutive activity). The large body of experimental data generated on structure and function relationships and receptor-ligand interactions are being harnessed for the in silico functional prediction of naturally occurring GPCR variants. We provide information on online resources dedicated to GPCRs and present applications of publically available computational tools for pharmacogenetic studies of GPCRs. As the breadth of GPCR pharmacogenomic data becomes clearer, the opportunity for routine assessment of GPCR variants to predict disease risk, drug response, and potential adverse drug effects will become possible.
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Affiliation(s)
- Miles D Thompson
- Department of Pharmacology and Toxicology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, ON, Canada, M5S 1A8,
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8
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Tschammer N. Virally Encoded G Protein-Coupled Receptors. ANNUAL REPORTS IN MEDICINAL CHEMISTRY VOLUME 47 2012. [DOI: 10.1016/b978-0-12-396492-2.00025-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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9
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Induction of therapeutic antibodies by vaccination against external loops of tumor-associated viral latent membrane protein. J Virol 2009; 83:11734-45. [PMID: 19726497 DOI: 10.1128/jvi.00578-09] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Some human herpesviruses (HHV) are etiological contributors to a wide range of malignant diseases. These HHV express latent membrane proteins (LMPs), which are type III membrane proteins consistently exposed at the cell surface in these malignancies. These LMPs have relatively large cytoplasmic domains but only short extracellular loops connecting transmembrane segments that are accessible at the surface of infected cells, but they do not elicit antibodies in the course of natural infection and tumorigenesis. We report here that conformational peptides mimicking two adjacent loops of the Epstein-Barr virus (EBV) LMP1 (2LS peptides) induce high-affinity antibodies with remarkable antitumor activities in mice. In active immunization experiments, LMP1-targeting 2LS vaccine conferred tumor protection in BALB/c mice. Moreover, this tumor protection is dependent upon a humoral anti-2LS immune response as demonstrated in DO11.10 (TCR-OVA) mice challenged with LMP1-expressing tumor and in SCID mice xenografted with human EBV-positive lymphoma cells. These data provide a proof of concept for 2LS immunization against short external loops of viral LMPs. This approach might possibly be extended to other infectious agents expressing type III membrane proteins.
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10
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Couty JP, Lupu-Meiri M, Oron Y, Gershengorn MC. Kaposi's sarcoma-associated herpesvirus-G protein-coupled receptor-expressing endothelial cells exhibit reduced migration and stimulated chemotaxis by chemokine inverse agonists. J Pharmacol Exp Ther 2009; 329:1142-7. [PMID: 19258523 DOI: 10.1124/jpet.108.147686] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A constitutively active G protein-coupled receptor (GPCR) encoded by Kaposi's sarcoma-associated herpesvirus (human herpesvirus-8) (KSHV) is expressed in endothelial (spindle) cells of Kaposi's sarcoma lesions. In this study, we report novel effects of basal signaling by this receptor and of inverse agonist chemokines on migration of KSHV-GPCR-expressing mouse lung endothelial cells. We show that basal signaling by KSHV-GPCR inhibits migration of endothelial cells in two systems, movement through porous filters and in vitro wound closure. Naturally occurring chemokines, interferon gamma-inducible protein-10 and stromal-derived factor-1, which act as inverse agonists at KSHV-GPCR, abrogate the inhibition of migration and stimulate directed migration (or chemotaxis) of these cells. Thus, the expression of KSHV-GPCR may allow infected endothelial cells in situ to remain in a localized environment or to directionally migrate along a gradient of specific chemokines that are inverse agonists at KSHV-GPCR.
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Affiliation(s)
- Jean-Pierre Couty
- Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
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11
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Constitutive serum response factor activation by the viral chemokine receptor homologue pUS28 is differentially regulated by Galpha(q/11) and Galpha(16). Cell Signal 2008; 20:1528-37. [PMID: 18534820 DOI: 10.1016/j.cellsig.2008.04.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2008] [Accepted: 04/11/2008] [Indexed: 01/30/2023]
Abstract
Expression of the human cytomegalovirus (HCMV)-encoded chemokine receptor homologue pUS28 in mammalian cells results in ligand-dependent and -independent changes in the activity of multiple cellular signal transduction pathways. The ligand-dependent signalling activity of pUS28 has been shown to be predominantly mediated by heterotrimeric G proteins of the G(i/o) and G(12/13) subfamilies. Ligand-independent constitutive activity of pUS28 causing stimulation of inositol phosphate formation has been correlated with the coupling of pUS28 to G proteins of the G(q) family. It is well known that activation of G(q) proteins by cell surface receptors is coupled to activation of the Rho GTPase RhoA. Activated RhoA regulates numerous cellular functions, including the activity of the transcription factor serum response factor (SRF). The marked activation of G(q) proteins by pUS28 in transfected and HCMV-infected cells prompted us to investigate its effect on SRF activity. The results presented herein demonstrate that expression of pUS28 in COS-7 cells caused a vigorous induction of SRF activity. This effect was observed in the absence of chemokines known to interact with pUS28, and was specifically mediated by endogenous G(q) and/or G(11) as well as RhoA and/or a closely related Rho GTPase. The stimulatory effect of pUS28 and Galpha(q/11) was independent of phospholipase C-beta (PLCbeta) activation and was markedly sensitive to inhibition by wild-type, but not by constitutively active Galpha(16), thus identifying Galpha(16) as a modulator of Galpha(q/11) function likely to act by competing with Galpha(q/11) for and thus uncoupling Galpha(q/11) from activation by pUS28.
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12
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Case R, Sharp E, Benned-Jensen T, Rosenkilde MM, Davis-Poynter N, Farrell HE. Functional analysis of the murine cytomegalovirus chemokine receptor homologue M33: ablation of constitutive signaling is associated with an attenuated phenotype in vivo. J Virol 2008; 82:1884-98. [PMID: 18057236 PMCID: PMC2258698 DOI: 10.1128/jvi.02550-06] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Accepted: 11/20/2007] [Indexed: 01/28/2023] Open
Abstract
The murine cytomegalovirus (MCMV) M33 gene is conserved among all betaherpesviruses and encodes a homologue of seven-transmembrane receptors (7TMR) with the capacity for constitutive signaling. Previous studies have demonstrated that M33 is important for MCMV dissemination to or replication within the salivary glands. In this study, we probed N- and C-terminal regions of M33 as well as known 7TMR signature motifs in transmembrane (TM) II and TM III to determine the impact on cell surface expression, constitutive signaling, and in vivo phenotype. The region between amino acids R(340) and A(353) of the C terminus was found to be important for CREB- and NFAT-mediated signaling, although not essential for phosphatidylinositol turnover. Tagging or truncation of the N terminus of M33 resulted in loss of cell surface expression. Within TM II, an F79D mutation abolished constitutive signaling, demonstrating a role, as in other cellular and viral 7TMR, of TM II in receptor activation. In TM III, the arginine (but not the asparagine) residue of the NRY motif (the counterpart of the common DRY motif in cellular 7TMR) was found to be essential for constitutive signaling. Selected mutations incorporated into recombinant MCMV showed that disruption of constitutive signaling for a viral 7TMR homologue resulted in a reduced capacity to disseminate to or replicate in the salivary glands. In addition, HCMV UL33 was found to partially compensate for the lack of M33 in vivo, suggesting conserved biological roles of the UL33 gene family.
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Affiliation(s)
- Ruth Case
- Clinical Medical Virology Centre, University of Queensland, Sir Albert Sakzewski Virus Research Centre, Royal Children's Hospital, Herston 4029, Queensland, Australia
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13
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Boudry C, Markine-Goriaynoff N, Delforge C, Springael JY, de Leval L, Drion P, Russell G, Haig DM, Vanderplasschen AF, Dewals B. The A5 gene of alcelaphine herpesvirus 1 encodes a constitutively active G-protein-coupled receptor that is non-essential for the induction of malignant catarrhal fever in rabbits. J Gen Virol 2008; 88:3224-3233. [PMID: 18024890 DOI: 10.1099/vir.0.83153-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many gammaherpesviruses encode G-protein-coupled receptors (GPCRs). Several in vivo studies have revealed that gammaherpesvirus GPCRs are important for viral replication and for virus-induced pathogenesis. The gammaherpesvirus alcelaphine herpesvirus 1 (AlHV-1) is carried asymptomatically by wildebeest, but causes malignant catarrhal fever (MCF) following cross-species transmission to a variety of susceptible species. The A5 ORF of the AlHV-1 genome encodes a putative GPCR. In the present study, we investigated whether A5 encodes a functional GPCR and addressed its role in viral replication and in the pathogenesis of MCF. In silico analysis supported the hypothesis that A5 could encode a functional GPCR as its expression product contained several hallmark features of GPCRs. Expression of A5 as tagged proteins in various cell lines revealed that A5 localizes in cell membranes, including the plasma membrane. Using [35S]GTPgammaS and reporter gene assays, we found that A5 is able to constitutively couple to alpha i-type G-proteins in transfected cells, and that this interaction is able to inhibit forskolin-triggered cAMP response element-binding protein (CREB) activation. Finally, using an AlHV-1 BAC clone, we produced a strain deleted for A5 and a revertant strain. Interestingly, the strain deleted for A5 replicated comparably to the wild-type parental strain and induced MCF in rabbits that was indistinguishable from that of the parental strain. The present study is the first to investigate the role of an individual gene of AlHV-1 in MCF pathogenesis.
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Affiliation(s)
- C Boudry
- Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of Liège, B-4000 Liège, Belgium
| | - N Markine-Goriaynoff
- Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of Liège, B-4000 Liège, Belgium
| | - C Delforge
- Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of Liège, B-4000 Liège, Belgium
| | - J-Y Springael
- Institute of Interdisciplinary Research in Human and Molecular Biology (IRIBHM), Free University of Brussels, Erasme, 808 Route de Lennik, B-1070 Brussels, Belgium
| | - L de Leval
- Department of Pathology (B23), Faculty of Medicine, University of Liège, B-4000 Liège, Belgium
| | - P Drion
- Animal facility (B23), University of Liège, B-4000 Liège, Belgium
| | - G Russell
- Moredun Research Institute, Pentlands Science Park, Penicuik, Midlothian EH26 0PZ, UK
| | - D M Haig
- Moredun Research Institute, Pentlands Science Park, Penicuik, Midlothian EH26 0PZ, UK
| | - A F Vanderplasschen
- Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of Liège, B-4000 Liège, Belgium
| | - B Dewals
- Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of Liège, B-4000 Liège, Belgium
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14
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Tadagaki K, Yamanishi K, Mori Y. Reciprocal roles of cellular chemokine receptors and human herpesvirus 7-encoded chemokine receptors, U12 and U51. J Gen Virol 2007; 88:1423-1428. [PMID: 17412969 DOI: 10.1099/vir.0.82665-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human herpesvirus 7 (HHV-7) is a member of the subfamilyBetaherpesvirinaethat exhibits a restricted cell tropism, preferentially infecting CD4+T cellsin vitro. HHV-7 encodes two functional chemokine receptors, U12 and U51. The human chemokines that act as ligands for these receptors have been identified as CCL22 (the natural ligand for CCR4) and CCL19 (the natural ligand for CCR7). It was found that murine L1.2 cells co-expressing CCR4 or CCR7 and U12 responded to both CCL22 and CCL19 in calcium-mobilization assays, but migrated in response only to the appropriate ligand for the expressed cellular receptor. Similar results were obtained with L1.2 cells co-expressing CCR4 or CCR7 with U51. These results suggest that the HHV-7 U12 and U51 receptors can function in concert with CCR4 and CCR7 in host-cell signalling pathways.
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Affiliation(s)
- Kenjiro Tadagaki
- Laboratory of Virology and Vaccinology, Division of Biomedical Research, National Institute of Biomedical Innovation, 7-6-8 Saito-Asagi, Ibaraki, Osaka 567-0085, Japan
| | - Koichi Yamanishi
- Laboratory of Virology and Vaccinology, Division of Biomedical Research, National Institute of Biomedical Innovation, 7-6-8 Saito-Asagi, Ibaraki, Osaka 567-0085, Japan
| | - Yasuko Mori
- Laboratory of Virology and Vaccinology, Division of Biomedical Research, National Institute of Biomedical Innovation, 7-6-8 Saito-Asagi, Ibaraki, Osaka 567-0085, Japan
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15
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Huang Y, Huang X, Zhang J, Gui J, Zhang Q. Subcellular Localization and Characterization of G Protein-Coupled Receptor Homolog from Lymphocystis Disease Virus Isolated in China. Viral Immunol 2007; 20:150-9. [PMID: 17425429 DOI: 10.1089/vim.2006.0082] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
G protein-coupled receptors (GPCRs) constitute a large superfamily involved in various types of signal transduction pathways, and play an important role in coordinating the activation and migration of leukocytes to sites of infection and inflammation. Viral GPCRs, on the other hand, can help the virus to escape from host immune surveillance and contribute to viral pathogenesis. Lymphocystis disease virus isolated in China (LCDV-C) contains a putative homolog of cellular GPCRs, LCDV-C GPCR. In this paper, LCDV-C GPCR was cloned, and the subcellular localization and characterization of GPCR protein were investigated in fish cells. LCDV-C GPCR encoded a 325 amino acid peptide, containing a typical seven-transmembrane domain characteristic of the chemokine receptors and a conserved DRY motif that is usually essential for receptor activation. Transient transfection of GPCR-EGFP in fathead minnow (FHM) cells and epithelioma papulosum cyprini (EPC) cells indicated that LCDV-C GPCR was expressed abundantly in both the cytoplasm and nucleoplasm. Transient overexpression of GPCR in these two cells cannot induce obvious apoptosis. FHM cells stably expressing GPCR showed enhanced cell proliferation and significant anchorage-independent growth. The effects of GPCR protein on external apoptotic stimuli were examined. Few apoptotic bodies were observed in cells expressing GPCR treated with actinomycin D (ActD). Quantitative analysis of apoptotic cells indicated that a considerable decrease in the apoptotic fraction of cells expressing GPCR, compared with the control cells, was detected after exposure to ActD and cycloheximide. These data suggest that LCDV-C GPCR may inhibit apoptosis as part of its potential mechanism in mediating cellular transformation.
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Affiliation(s)
- Youhua Huang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Graduate University of Chinese Academy of Science, Wuhan, People's Republic of China
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16
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Vischer HF, Hulshof JW, de Esch IJP, Smit MJ, Leurs R. Virus-encoded G-protein-coupled receptors: constitutively active (dys)regulators of cell function and their potential as drug target. ERNST SCHERING FOUNDATION SYMPOSIUM PROCEEDINGS 2007:187-209. [PMID: 17703583 DOI: 10.1007/2789_2006_009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
G-protein-coupled receptors encoded by herpesviruses such as EBV, HCMV and KSHV are very interesting illustrations of the (patho)physiological importance of constitutive GPCR activity. These viral proteins are expressed on the cell surface of infected cells and often constitutively activate a variety of G-proteins. For some virus-encoded GPCRs, the constitutive activity has been shown to occur in vivo, i.e., in infected cells. In this paper, we will review the occurrence of virus-encoded GPCRs and describe their known signaling properties. Moreover, we will also review the efforts, directed towards the discovery of small molecule antagonist, that so far have been mainly focused on the HCMV-encoded GPCR US28. This virus-encoded receptor might be involved in cardiovascular diseases and cancer and seems an interesting target for drug intervention.
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Affiliation(s)
- H F Vischer
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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17
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Rosenkilde MM, Benned-Jensen T, Andersen H, Holst PJ, Kledal TN, Lüttichau HR, Larsen JK, Christensen JP, Schwartz TW. Molecular Pharmacological Phenotyping of EBI2. J Biol Chem 2006; 281:13199-13208. [PMID: 16540462 DOI: 10.1074/jbc.m602245200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Epstein-Barr virus (EBV)-induced receptor 2 (EBI2) is an orphan seven-transmembrane (7TM) receptor originally identified as the most up-regulated gene (>200-fold) in EBV-infected cells. Here we show that EBI2 signals with constitutive activity through Galpha(i) as determined by a receptor-mediated inhibition of forskolin-induced cAMP production and an induction of the serum response element-driven transcriptional activity in a pertussis toxin-sensitive manner. Galpha(s) and Galpha(q) were not activated constitutively as determined by the lack of cAMP production, the lack of inositol phosphate turnover, and the lack of activities of the transcription factors: cAMP response element-binding protein and nuclear factor-kappaB. Immunohistochemistry and confocal microscopy of FLAG- and green fluorescent protein-tagged EBI2 revealed cell-surface expression. A putative N-terminal truncated version of EBI2, delta4-EBI2, showed similar expression and signaling through Galpha(i) as full-length EBI2. By using a 32P-labeled EBI2 probe we found a very high expression in lymphoid tissue (spleen and lymph node) and peripheral blood mononuclear cells and a high expression in lung tissue. Real-time PCR of EBV-infected cells showed high expression of EBI2 during latent and lytic infection, in contrast to the EBV-encoded 7TM receptor BILF1, which was induced during lytic infection. EBI2 clustered with the orphan GPR18 by alignment analysis as well as by close proximity in the chromosomal region 13q32.3. Based on the constitutive signaling and cellular expression pattern of EBI2, it is suggested that it may function in conjunction with BILF1 in the reprogramming of the cell during EBV infection.
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Affiliation(s)
- Mette M Rosenkilde
- Laboratory for Molecular Pharmacology, Department of Pharmacology, University of Copenhagen, 2200 Copenhagen N, Copenhagen, Denmark.
| | - Tau Benned-Jensen
- Laboratory for Molecular Pharmacology, Department of Pharmacology, University of Copenhagen, 2200 Copenhagen N, Copenhagen, Denmark
| | - Helene Andersen
- Clinical Research Unit, Copenhagen University Hospital, 2650 Hvidovre, Denmark
| | - Peter J Holst
- Institute for Medical Microbiology and Immunology, The Panum Institute, Building 18.6, Blegdamsvej 3, 2200 Copenhagen N, Copenhagen, Denmark
| | - Thomas N Kledal
- Clinical Research Unit, Copenhagen University Hospital, 2650 Hvidovre, Denmark
| | - Hans R Lüttichau
- Laboratory for Molecular Pharmacology, Department of Pharmacology, University of Copenhagen, 2200 Copenhagen N, Copenhagen, Denmark; Department for Infectious Diseases, Copenhagen University Hospital, 2200 Copenhagen, Denmark
| | - Jørgen K Larsen
- Finsen Laboratory, The Finsen Center, Copenhagen University Hospital, 2200 Copenhagen, Denmark
| | - Jan P Christensen
- Institute for Medical Microbiology and Immunology, The Panum Institute, Building 18.6, Blegdamsvej 3, 2200 Copenhagen N, Copenhagen, Denmark
| | - Thue W Schwartz
- Laboratory for Molecular Pharmacology, Department of Pharmacology, University of Copenhagen, 2200 Copenhagen N, Copenhagen, Denmark
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18
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Abstract
Multicellular organisms possess very sophisticated defense mechanisms that are designed to effectively counter the continual microbial insult of the environment within the vertebrate host. However, successful microbial pathogens have in turn evolved complex and efficient methods to overcome innate and adaptive immune mechanisms, which can result in disease or chronic infections. Although the various virulence strategies used by viral and bacterial pathogens are numerous, there are several general mechanisms that are used to subvert and exploit immune systems that are shared between these diverse microbial pathogens. The success of each pathogen is directly dependant on its ability to mount an effective anti-immune response within the infected host, which can ultimately result in acute disease, chronic infection, or pathogen clearance. In this review, we highlight and compare some of the many molecular mechanisms that bacterial and viral pathogens use to evade host immune defenses.
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Affiliation(s)
- B Brett Finlay
- Michael Smith Laboratories, University of British Columbia, Vancouver, B.C. V6T 1Z4 Canada.
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19
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Galligan CL, Murooka TT, Rahbar R, Baig E, Majchrzak-Kita B, Fish EN. Interferons and viruses: signaling for supremacy. Immunol Res 2006; 35:27-40. [PMID: 17003507 PMCID: PMC7091094 DOI: 10.1385/ir:35:1:27] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 12/28/2022]
Abstract
Interferon (IFN)-alpha and IFN-beta are critical mediators of host defense against microbial challenges, directly interfering with viral infection and influencing both the innate and adaptive immune responses. IFNs exert their effects in target cells through the activation of a cell-surface receptor, leading to a cascade of signaling events that determine transcriptional and translation regulation. Understanding the circuitry associated with IFN-mediated signal transduction that leads to a specific biological outcome has been a major focus of our laboratory. Through the efforts of graduate students, postdoctoral fellows, a skilled research technologist, and important collaborations with investigators elsewhere, we have provided some insights into the complexity of the IFN system-and the elegance and simplicity of how protein-protein interactions define biological function.
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Affiliation(s)
- C. L. Galligan
- Department of Immunology, University of Toronto, Toronto, Canada
- Toronto General Research Institute, University Health Network, 67 College Street Rm. 424, M5G 2M1 Toronto, Ontario Canada
| | - T. T. Murooka
- Department of Immunology, University of Toronto, Toronto, Canada
- Toronto General Research Institute, University Health Network, 67 College Street Rm. 424, M5G 2M1 Toronto, Ontario Canada
| | - R. Rahbar
- Department of Immunology, University of Toronto, Toronto, Canada
- Toronto General Research Institute, University Health Network, 67 College Street Rm. 424, M5G 2M1 Toronto, Ontario Canada
| | - E. Baig
- Department of Immunology, University of Toronto, Toronto, Canada
- Toronto General Research Institute, University Health Network, 67 College Street Rm. 424, M5G 2M1 Toronto, Ontario Canada
| | - B. Majchrzak-Kita
- Department of Immunology, University of Toronto, Toronto, Canada
- Toronto General Research Institute, University Health Network, 67 College Street Rm. 424, M5G 2M1 Toronto, Ontario Canada
| | - E. N. Fish
- Department of Immunology, University of Toronto, Toronto, Canada
- Toronto General Research Institute, University Health Network, 67 College Street Rm. 424, M5G 2M1 Toronto, Ontario Canada
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20
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Vischer HF, Leurs R, Smit MJ. HCMV-encoded G-protein-coupled receptors as constitutively active modulators of cellular signaling networks. Trends Pharmacol Sci 2005; 27:56-63. [PMID: 16352349 DOI: 10.1016/j.tips.2005.11.006] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2005] [Revised: 10/05/2005] [Accepted: 11/21/2005] [Indexed: 11/19/2022]
Abstract
Several herpesviruses encode G-protein-coupled receptor (vGPCR) proteins that are homologous to human chemokine receptors. In contrast to chemokine receptors, many vGPCRs signal in a ligand-independent (constitutive) manner. Such constitutive signaling is of major significance because various pathologies are associated with activating GPCR mutations. Constitutive activity of the human herpesvirus 8-encoded GPCR (ORF74), for example, is essential for its oncogenic potential to cause angioproliferative Kaposi's sarcoma-like lesions. The human cytomegalovirus (HCMV) encodes four GPCRs, of which US28 and UL33 display constitutive activity in transfected, but also HCMV-infected, cells. In addition, US28 is activated by a broad spectrum of chemokines. Furthermore, both US28 and UL33 show promiscuous G-protein coupling, whereas chemokine receptors activate primarily G(i/o) proteins. Thus, these vGPCRs are versatile signaling devices, reprogramming cellular signaling networks to modulate cellular function after infection. By these means, these HCMV-encoded receptors might contribute to HCMV-related pathologies.
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Affiliation(s)
- Henry F Vischer
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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