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 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 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 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.

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.

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