A retinal-specific regulator of G-protein signaling interacts with Galpha(o) and accelerates an expressed metabotropic glutamate receptor 6 cascade.
G(o) is the most abundant G-protein in the brain, but its regulators are essentially unknown. In retina, Galpha(o1) is obligatory in mediating the metabotropic glutamate receptor 6 (mGluR6)-initiated ON response. To identify the interactors of G(o), we conducted a yeast two-hybrid screen with constituitively active Galpha(o) as a bait. The screen frequently identified a regulator of G-protein signaling (RGS), Ret-RGS1, the interaction of which we confirmed by coimmunoprecipitation with Galpha(o) in transfected cells and in retina. Ret-RGS1 localized to the dendritic tips of ON bipolar neurons, along with mGluR6 and Galpha(o1). When Ret-RGS1 was coexpressed in Xenopus oocytes with mGluR6, Galpha(o1), and a GIRK (G-protein-gated inwardly rectifying K+) channel, it accelerated the deactivation of the channel response to glutamate in a concentration-dependent manner. Because light onset suppresses glutamate release from photoreceptors onto the ON bipolar dendrites, Ret-RGS1 should accelerate the rising phase of the light response of the ON bipolar cell. This would tend to match its kinetics to that of the OFF bipolar that arises directly from ligand-gated channels.
Dhingra
Anuradha
A
Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6058, USA. annu@retina.anatomy.upenn.edu
Faurobert
Eva
E
Dascal
Nathan
N
Sterling
Peter
P
Vardi
Noga
N
D000818:Animals; D002417:Cattle; D002460:Cell Line; D044385:GTP-Binding Protein alpha Subunits / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D066298:In Vitro Techniques; D009865:Oocytes / Q000502:physiology; D020710:RGS Proteins / Q000096:biosynthesis / Q000502:physiology*; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D012160:Retina / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D020798:Two-Hybrid System Techniques; D014982:Xenopus laevis
D044385:GTP-Binding Protein alpha Subunits; D020710:RGS Proteins; D018094:Receptors, Metabotropic Glutamate; C113897:metabotropic glutamate receptor 6