The Chain Length Dependence of Helix Formation of the Second Transmembrane Domain of a G Protein-coupled Receptor ofSaccharomycescerevisiae

Filamentous growth of Candida albicans occurs in response to a variety of environmental signals. The C. albicans gene orf19.1944 and its allele orf19.9499 are identical and are predicted to encode an 823-residue, 7-transmembrane-domain protein that has all the expected features of a G-protein-coupled receptor. The protein is 20.9% identical to the Saccharomyces cerevisiae Gpr1p receptor that signals both glucose availability and nitrogen limitation. Deletion of both copies of the gene in C. albicans abolished filamentation by colonies embedded in rich media (YPS, YPGal, and YPGlu), whereas mutants carrying a single copy of the gene were indistinguishable from the parental strain under these conditions. On medium containing low concentrations of ammonia (SLAD and SLAM media), surface colonies of both the homozygous deletion mutants and the mutants carrying a single copy of the gene were defective in filamentation. Serum-induced germ tube formation was unaffected by deletion of this gene, as was filamentation of the mutants growing on the surface of solid Spider medium at 37 °C or embedded in solid Spider medium at 25 °C. The protein encoded by orf19.1944 and orf19.9499 has a role in filamentation by both surface and embedded colonies, presumably as a sensor of environmental cues.Key words: Candida albicans, G-protein-coupled receptor, orf19.1944, embedded agar, filamentation.

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Evidence for Osteocalcin Binding and Activation of GPRC6A in β-Cells

Endocrinology ◽

10.1210/en.2015-2010 ◽

2016 ◽

Vol 157 (5) ◽

pp. 1866-1880 ◽

Cited By ~ 56

Author(s):

Min Pi ◽

Karan Kapoor ◽

Ruisong Ye ◽

Satoru Kenneth Nishimoto ◽

Jeremy C. Smith ◽

...

Keyword(s):

Cell Proliferation ◽

G Protein ◽

Computational Models ◽

Transmembrane Domain ◽

Structural Basis ◽

G Protein Coupled Receptor ◽

Β Cells ◽

Β Cell ◽

Cell Functions ◽

G Protein Coupled

Abstract The possibility that G protein-coupled receptor family C member A (GPRC6A) is the osteocalcin (Ocn)-sensing G protein-coupled receptor that directly regulates pancreatic β-cell functions is controversial. In the current study, we found that Ocn and an Ocn-derived C-terminal hexapeptide directly activate GPRC6A-dependent ERK signaling in vitro. Computational models probe the structural basis of Ocn binding to GPRC6A and predict that the C-terminal hexapeptide docks to the extracellular side of the transmembrane domain of GPRC6A. Consistent with the modeling, mutations in the computationally identified binding pocket of GPRC6A reduced Ocn and C-terminal hexapeptide activation of this receptor. In addition, selective deletion of Gprc6a in β-cells (Gprc6aβ-cell-cko) by crossing Gprc6aflox/flox mice with Ins2-Cre mice resulted in reduced pancreatic weight, islet number, insulin protein content, and insulin message expression. Both islet size and β-cell proliferation were reduced in Gprc6aβ-cell-cko compared with control mice. Gprc6aβ-cell-cko exhibited abnormal glucose tolerance, but normal insulin sensitivity. Islets isolated from Gprc6aβ-cell-cko mice showed reduced insulin simulation index in response to Ocn. These data establish the structural basis for Ocn direct activation of GPRC6A and confirm a role for GPRC6A in regulating β-cell proliferation and insulin secretion.

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A Drosophila orphan G protein-coupled receptor BOSS functions as a glucose-responding receptor: Loss of boss causes abnormal energy metabolism

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.0807833105 ◽

2008 ◽

Vol 105 (40) ◽

pp. 15328-15333 ◽

Cited By ~ 47

Author(s):

Ayako Kohyama-Koganeya ◽

Yeon-Jeong Kim ◽

Masayuki Miura ◽

Yoshio Hirabayashi

Keyword(s):

Lipid Metabolism ◽

G Protein ◽

Insulin Signaling ◽

Metabolic Regulation ◽

Transmembrane Domain ◽

Fat Body ◽

Nutrient Sensing ◽

G Protein Coupled Receptor ◽

Extracellular Glucose ◽

G Protein Coupled

Glucose, one of the most important nutrients for animals, acts as a regulatory signal that controls the secretion of hormones, such as insulin, by endocrine tissues. However, how organisms respond to extracellular glucose and how glucose controls nutrient homeostasis remain unknown. Here, we show that a putative Drosophila melanogaster G protein-coupled receptor, previously identified as Bride of sevenless (BOSS), responds to extracellular glucose and regulates sugar and lipid metabolism. We found that BOSS was expressed in the fat body, a nutrient-sensing tissue equivalent to mammalian liver and adipose tissues, and in photoreceptor cells. Boss null mutants had small bodies, exhibited abnormal sugar and lipid metabolism (elevated circulating sugar and lipid levels, impaired lipid mobilization to oenocytes), and were sensitive to nutrient deprivation stress. These phenotypes are reminiscent of flies defective in insulin signaling. Consistent with these findings are the observations that boss mutants had reduced PI3K activity and phospho-AKT levels, which indicates that BOSS is required for proper insulin signaling. Because human G protein-coupled receptor 5B and the seven-transmembrane domain of BOSS share the same sequence, our results also have important implications for glucose metabolism in humans. Thus, our study provides insight not only into the basic mechanisms of metabolic regulation but also into the pathobiological basis for diabetes and obesity.

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