scholarly journals The constitutive activity of the viral-encoded G protein-coupled receptor US28 supports a complex signalling network contributing to cancer development

2020 ◽  
Vol 48 (4) ◽  
pp. 1493-1504
Author(s):  
Carole A. Daly ◽  
Martine J. Smit ◽  
Bianca Plouffe
Keyword(s):  
G Protein ◽  
Cancer Progression ◽  
Structural Characteristics ◽  
Lytic Replication ◽  
Constitutive Activity ◽  
G Protein Coupled Receptor ◽  
Viral Receptor ◽  
Signalling Network ◽  
Cellular Pathways ◽  
G Protein Coupled

US28 is a viral G protein-coupled receptor (GPCR) encoded by the human cytomegalovirus (HCMV). This receptor, expressed both during lytic replication and viral latency, is required for latency. US28 is binding to a wide variety of chemokines but also exhibits a particularly high constitutive activity robustly modulating a wide network of cellular pathways altering the host cell environment to benefit HCMV infection. Several studies suggest that US28-mediated signalling may contribute to cancer progression. In this review, we discuss the unique structural characteristics that US28 acquired through evolution that confer a robust constitutive activity to this viral receptor. We also describe the wide downstream signalling network activated by this constitutive activation of US28 and discuss how these signalling pathways may promote and support important cellular aspects of cancer.

Involvement of the constitutive activity of the GHS-R1a (ghrelin G-protein coupled receptor) in the tumorigenesis of somatotroph adenomas

2013 ◽  
Author(s):  
Yves Louis Mear ◽  
Xavier Come Donato ◽  
Marie Pierre Blanchard ◽  
Celine Defilles ◽  
Christophe Lisbonis ◽  
...  
Keyword(s):  
G Protein ◽  
Constitutive Activity ◽  
G Protein Coupled Receptor ◽  
G Protein Coupled

scholarly journals Prostate-specific G-protein-coupled receptor collaborates with loss of PTEN to promote prostate cancer progression

Oncogene ◽  
2015 ◽  
Vol 35 (9) ◽  
pp. 1153-1162 ◽  
Author(s):  
M Rodriguez ◽  
S Siwko ◽  
L Zeng ◽  
J Li ◽  
Z Yi ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
G Protein ◽  
Cancer Progression ◽  
Prostate Cancer Progression ◽  
G Protein Coupled Receptor ◽  
G Protein Coupled

scholarly journals Molecular cloning of an orphan G-protein-coupled receptor that constitutively activates adenylate cyclase

1995 ◽  
Vol 309 (3) ◽  
pp. 837-843 ◽  
Author(s):  
D Eggerickx ◽  
J F Denef ◽  
O Labbe ◽  
Y Hayashi ◽  
S Refetoff ◽  
...  
Keyword(s):  
Adenylate Cyclase ◽  
G Protein ◽  
Rnase Protection Assay ◽  
Biological Significance ◽  
Orphan Receptor ◽  
Constitutive Activity ◽  
G Protein Coupled Receptor ◽  
Rnase Protection ◽  
G Protein Coupled ◽  
Stimulation Of

A human gene encoding an orphan G-protein-coupled receptor named ACCA (adenylate cyclase constitutive activator) was isolated from a genomic library using as a probe a DNA fragment obtained by low-stringency PCR. Human ACCA (hACCA) is a protein of 330 amino acids that exhibits all the structural hallmarks of the main family of G-protein-coupled receptors. Expression of hACCA resulted in a dramatic stimulation of adenylate cyclase, similar in amplitude to that obtained with other Gs-coupled receptors fully activated by their respective ligands. This stimulation was obtained in a large variety of stable cell lines derived from various organs, and originating from different mammalian species. hACCA was found to be the human homologue of a recently reported mouse orphan receptor (GPCR21). The mouse ACCA (mACCA) was therefore recloned by PCR, and expression of mACCA in Cos-7 cells demonstrated that the mouse receptor behaved similarly as a constitutive activator of adenylate cyclase. It is not known presently whether the stimulation of adenylate cyclase is the result of a true constitutive activity of the receptor or, alternatively, is the consequence of a permanent stimulation by a ubiquitous ligand. The tissue distribution of mACCA was determined by RNase protection assay. Abundant transcripts were found in the brain, whereas lower amounts were detected in testis, ovary and eye. Various hypotheses concerning the constitutive activity of ACCA and their potential biological significance are discussed.

scholarly journals The human cytomegalovirus G-protein coupled receptor US28 promotes latency by attenuating c-fos

2018 ◽  
Author(s):  
Benjamin A. Krishna ◽  
Monica S. Humby ◽  
William E. Miller ◽  
Christine M. O’Connor
Keyword(s):  
Host Cell ◽  
G Protein ◽  
Human Cytomegalovirus ◽  
Latent Infection ◽  
Lytic Replication ◽  
Wild Type ◽  
G Protein Coupled Receptor ◽  
In Trans ◽  
G Protein Coupled

AbstractHuman cytomegalovirus (HCMV) is a ubiquitous pathogen that undergoes latency in cells of the hematopoietic compartment, though the mechanisms underlying establishment and maintenance of latency remain elusive. We previously reported that the HCMV-encoded G-protein coupled receptor (GPCR) homolog,US28is required for successful latent infection. We now show that US28 protein (pUS28) providedin transcomplements the US28Δ lytic phenotype in myeloid cells, suggesting that sustained US28 expression is necessary for long-term latency. Furthermore, expression of pUS28 at the time of infection represses transcription from the major immediate early promoter (MIEP) within 24 hours. However, this repression is only maintained in the presence of continual pUS28 expression providedin trans. Our data also reveal that pUS28-mediated signaling attenuates both expression and phosphorylation of cellular fos (c-fos), an AP-1 transcription factor subunit, to repress MIEP-driven transcription. AP-1 binds to the MIEP and promotes lytic replication, and in line with this, we find that US28Δ infection results in an increase in AP-1 binding to the MIEP, compared to wild type latent infection. Pharmacological inhibition of c-fos represses the MIEP during US28Δ infection to similar levels we observe during wild type latent infection. Together, our data reveal that US28 is required for both establishment and long-term maintenance of HCMV latency, which is modulated, at least in part, by repressing functional AP-1 binding to the MIEP.Significance StatementHuman cytomegalovirus (HCMV) is a wise-spread pathogen that remains with an individual for life in a quiescent/latent state, posing little threat to an otherwise healthy person. However, when an individual’s immune system is severely compromised, HCMV can reactivate to its active/lytic state, resulting in viral spread and disease that is often fatal. The biological mechanisms underlying HCMV latency and reactivation remain poorly understood. Herein we show that the viral-encoded G-protein coupled receptor (GPCR)US28aids in the establishment and the maintenance of viral latency. Furthermore, we find that US28 modulates host cell proteins to suppress viral processes associated with active/lytic replication, thereby promoting latent infection. This work provides mechanism by which HCMV modulates the host cell environment to its advantage.

scholarly journals In vitro profiling of orphan G protein coupled receptor (GPCR) constitutive activity

2021 ◽  
Author(s):  
Lyndsay R. Watkins ◽  
Cesare Orlandi
Keyword(s):  
G Protein ◽  
Luciferase Reporter ◽  
List Type ◽  
Constitutive Activity ◽  
Protein Signaling ◽  
G Protein Coupled Receptor ◽  
Orphan Receptors ◽  
Gpcr Family ◽  
Orphan Gpcrs ◽  
G Protein Coupled

AbstractBackground and PurposeMembers of the G protein coupled receptor (GPCR) family are targeted by a significant fraction of the available FDA-approved drugs. However, the physiological role and pharmacological properties of many GPCRs remain unknown, representing untapped potential in drug design. Of particular interest are ~100 less-studied GPCRs known as orphans because their endogenous ligands are unknown. Intriguingly, disease-causing mutations identified in patients, together with animal studies, have demonstrated that many orphan receptors play crucial physiological roles, and thus, represent attractive drug targets.Experimental ApproachThe majority of deorphanized GPCRs demonstrate coupling to Gi/o, however a limited number of techniques allow the detection of intrinsically small constitutive activity associated with Gi/o protein activation which represents a significant barrier in our ability to study orphan GPCR signaling. Using luciferase reporter assays, we effectively detected constitutive Gs, Gq, and G12/13 protein signaling by unliganded receptors, and introducing various G protein chimeras, we provide a novel, highly-sensitive tool capable of identifying Gi/o coupling in unliganded orphan GPCRs.Key ResultsUsing this approach, we measured the constitutive activity of the entire class C GPCR family that includes 8 orphan receptors, and a subset of 20 prototypical class A GPCR members, including 11 orphans. Excitingly, this approach illuminated the G protein coupling profile of 8 orphan GPCRs (GPR22, GPR137b, GPR88, GPR156, GPR158, GPR179, GPRC5D, and GPRC6A) previously linked to pathophysiological processes.Conclusion and ImplicationsWe provide a new platform that could be utilized in ongoing studies in orphan receptor signaling and deorphanization efforts.What is already knownA large group of understudied orphan GPCRs controls a variety of physiological process.What this study addsA new strategy to identify G protein signaling associated with orphan GPCRs.Identification of Gi/o coupling for 8 orphan GPCRs.What is the clinical significanceMany orphan GPCRs are associated with pathological conditions and represent promising druggable targets.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus G-Protein-Coupled Receptor Prevents AU-Rich-Element-Mediated mRNA Decay

2012 ◽  
Vol 86 (16) ◽  
pp. 8859-8871 ◽  
Author(s):  
Jennifer A. Corcoran ◽  
Denys A. Khaperskyy ◽  
Benjamin P. Johnston ◽  
Christine A. King ◽  
David P. Cyr ◽  
...  
Keyword(s):  
Gene Expression ◽  
G Protein ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Mrna Degradation ◽  
Lytic Replication ◽  
G Protein Coupled Receptor ◽  
Infected Cells ◽  
Host Shutoff ◽  
G Protein Coupled

During lytic Kaposi's sarcoma-associated herpesvirus (KSHV) infection, host gene expression is severely restricted by a process of global mRNA degradation known as host shutoff, which rededicates translational machinery to the expression of viral proteins. A subset of host mRNAs is spared from shutoff, and a number of these containcis-acting AU-rich elements (AREs) in their 3′ untranslated regions. AREs are found in labile mRNAs encoding cytokines, growth factors, and proto-oncogenes. Activation of the p38/MK2 signal transduction pathway reverses constitutive decay of ARE-mRNAs, resulting in increased protein production. The viral G-protein-coupled receptor (vGPCR) is thought to play an important role in promoting the secretion of angiogenic molecules from KSHV-infected cells during lytic replication, but to date it has not been clear how vGPCR circumvents host shutoff. Here, we demonstrate that vGPCR activates the p38/MK2 pathway and stabilizes ARE-mRNAs, augmenting the levels of their protein products. Using MK2-deficient cells, we demonstrate that MK2 is essential for maximal vGPCR-mediated ARE-mRNA stabilization. ARE-mRNAs are normally delivered to cytoplasmic ribonucleoprotein granules known as processing bodies (PBs) for translational silencing and decay. We demonstrate that PB formation is prevented during KSHV lytic replication or in response to vGPCR-mediated activation of RhoA subfamily GTPases. Together, these data show for the first time that vGPCR impacts gene expression at the posttranscriptional level, coordinating an attack on the host mRNA degradation machinery. By suppressing ARE-mRNA turnover, vGPCR may facilitate escape of certain target mRNAs from host shutoff and allow secretion of angiogenic factors from lytically infected cells.

scholarly journals Mutational analysis of the R33-encoded G protein-coupled receptor of rat cytomegalovirus: identification of amino acid residues critical for cellular localization and ligand-independent signalling

2004 ◽  
Vol 85 (4) ◽  
pp. 897-909 ◽  
Author(s):  
Yvonne K. Gruijthuijsen ◽  
Erik V. H. Beuken ◽  
Martine J. Smit ◽  
Rob Leurs ◽  
Cathrien A. Bruggeman ◽  
...  
Keyword(s):  
G Protein ◽  
Cellular Localization ◽  
Mutational Analysis ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Constitutive Activity ◽  
G Protein Coupled Receptor ◽  
Human Cmv ◽  
G Protein Coupled

The rat cytomegalovirus (RCMV) R33 gene encodes a G protein-coupled receptor (GPCR), pR33, which possesses agonist-independent, constitutive signalling activity. To characterize this activity further, we generated a series of point and deletion mutants of pR33. Both expression of and signalling by the mutants was evaluated. Several point mutants were generated that contained modifications in the NRY motif. This motif, at aa 130–132 of pR33, is the counterpart of the common DRY motif of GPCRs, which is known to be involved in G protein coupling. We found that mutation of the asparagine residue within the NRY motif of pR33 (N130) to aspartic acid resulted in a mutant (N130D) with similar signalling characteristics to the wild-type (WT) protein, indicating that N130 is not the determinant of constitutive activity of pR33. Interestingly, a mutant carrying an alanine at aa 130 (N130A) was severely impaired in Gq/11-mediated, constitutive activation of phospholipase C, whereas it displayed similar levels of activity to pR33 in Gi/0-mediated signalling. Another protein that contained a modified NRY motif, R131A, did not show constitutive activity, whereas mutants Y132F and Y132A displayed similar activities to the WT receptor. This indicated that residue R131 is critical for pR33 function in vitro, whereas Y132 is not. Finally, we identified two consecutive arginines within the C-terminal tails of both pR33 and its homologue from human CMV, pUL33, which are important for correct cell-surface expression of these receptors.

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