Orphan G protein-coupled receptors MrgA1 and MrgC11 are distinctively activated by RF-amide-related peptides through the Galpha q/11 pathway.
MrgA1 and MrgC11 belong to a recently identified family of orphan G-protein coupled receptors, called mrgs (mas-related genes). They are only expressed in a specific subset of sensory neurons that are known to detect painful stimuli. However, the precise physiological function of Mrg receptors and their underlying mechanisms of signal transduction are not known. We therefore have screened a series of neuropeptides against human embryonic kidney (HEK) 293 cells that stably express either MrgA1 or MrgC11 to identify ligands and/or agonists. MrgA1- or MrgC11-specific agonists stimulated dose-dependent increases in intracellular free Ca(2+) in a pertussis toxin-insensitive manner, but failed to alter basal or forskolin-stimulated levels of intracellular cAMP. Furthermore, studies using embryonic fibroblasts derived from various Galpha protein knockout mice demonstrated that both the MrgA1 and MrgC11 receptors are coupled to the Galpha(q/11) signaling pathway. Screening of neuropeptides identified surrogate agonists, most of these peptides included a common C-terminal -RF(Y)G or -RF(Y) amide motif. Structure-function studies suggest that endogenous ligands of Mrg receptors are likely to be RF(Y)G and/or RF(Y) amide-related peptides and that postprocessing of these peptides may serve to determine Mrg receptor-ligand specificity. The differences in ligand specificity also suggest functional diversity amongst the Mrg receptors.
Han
Sang-Kyou
SK
Division of Biology 147-75, California Institute of Technology, Pasadena 91125, USA.
Dong
Xinzhong
X
Hwang
Jong-Ik
JI
Zylka
Mark J
MJ
Anderson
David J
DJ
Simon
Melvin I
MI
D000595:Amino Acid Sequence; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins / Q000502:physiology*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014162:Transfection
D000242:Cyclic AMP; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D019204:GTP-Binding Proteins; D020962:Heterotrimeric GTP-Binding Proteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D011994:Recombinant Proteins; C470191:MrgA1 protein, mouse; C470192:Mrgprx1 protein, mouse