title: Cross-regulation of VPAC2 receptor internalization by m2 receptors via c-Src-mediated phosphorylation of GRK2.
abstract: The aim of the study was to examine the mechanisms by which ACh, acting via m2 receptors, regulates GRK2-mediated VPAC(2) receptor desensitization in gastric smooth muscle cells. VIP induced VPAC(2) receptor phosphorylation and internalization in freshly dispersed smooth muscle cells. Co-stimulation with acetylcholine (ACh), in the presence of m3 receptor antagonist, 4-DAMP, augmented VPAC(2) receptor phosphorylation and internalization. The m2 receptor antagonist methoctramine or the c-Src inhibitor PP2 blocked the effect of ACh, suggesting that the augmentation was mediated by c-Src, derived from m2 receptor activation. ACh induced activation of c-Src and phosphorylation of GRK2 and the effects of ACh were blocked by methoctramine, PP2, or by uncoupling of m2 receptors from G(i3) with pertussis toxin. In conclusion, we identified a novel mechanism of cross-regulation of GRK2-mediated phosphorylation and internalization of G(s)-coupled VPAC(2) receptors by G(i)-coupled m2 receptors via tyrosine phosphorylation of GRK2 and stimulation of GRK2 activity.
authors.affiliation: Department of Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298, United States.
authors.forename: Sunila
authors.initials: S
authors.lastname: Mahavadi
authors.forename: Jiean
authors.initials: J
authors.lastname: Huang
authors.forename: Wimolpak
authors.initials: W
authors.lastname: Sriwai
authors.forename: Krothapalli R S S
authors.initials: KR
authors.lastname: Rao
authors.forename: Karnam S
authors.initials: KS
authors.lastname: Murthy
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D004305:Dose-Response Relationship, Drug; D004705:Endocytosis / Q000502:physiology; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D011817:Rabbits; D043585:Receptor, Muscarinic M2 / Q000378:metabolism / Q000502:physiology*; D051239:Receptors, Vasoactive Intestinal Peptide, Type II / Q000378:metabolism*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology; D051552:beta-Adrenergic Receptor Kinases / Q000378:metabolism*
chemical_list: D043585:Receptor, Muscarinic M2; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D014660:Vasoactive Intestinal Peptide; D016392:Proto-Oncogene Proteins pp60(c-src); D054746:Cyclic AMP-Dependent Protein Kinase Type II; D051552:beta-Adrenergic Receptor Kinases; D000109:Acetylcholine