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Z. Wang, Y. Qian, T. G. Wensel, D. K. Mojumder; Effects of Genetic Disruption of RGS7, RGS11, and GPR158 on the Murine Electroretinogram. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2911.
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© ARVO (1962-2015); The Authors (2016-present)
To explore the roles of the R7 RGS proteins, RGS7 and RGS11, and the RGS7-binding GPCR, GPR158, in retinal signaling. RGS7 and RGS11 and their obligatory binding partner Gbeta5 have been proposed to play a role in regulating the kinetics of light responses of retinal ON bipolar cells (ONBPC), based on their localization in the dendritic tips of the ONBPC, where metabotropic glutamate receptor mGluR6 responds to glutamate released from rod and cone photoreceptor synaptic terminals by activation of the RGS7/RGS11 substrate, Galphao. GPR158 is an orphan member of the metabotropic glutamate receptor family of GPCR that binds RGS7 in the brain.
We have explored the relative roles of these proteins by immunofluorescence staining of murine retina, and by recording electroretinograms from mice with targeted disruption of the RGS7 and RGS11 genes, or with an shRNA transgene that knocks down GPR158 levels.
Genetic disruption of either RGS7 or RGS11 produced delays in the leading edge of the b-wave response, which arises from depolarization of ON bipolar cells, but no changes in the photoreceptor-derived a-wave. Mice homozygous for a mutation in RGS7 had delayed b-waves for scotopic intensities under fully dark-adapted condition, but no delay in photopic responses. RGS11 mutants produced delays in both the leading edge of the b-wave and the trailing edge of the b-wave for mixed rod+cone fully dark-adapted ERG’s and especially for cone driven ERG’s. Scotopic threshold responses and oscillatory potentials were attenuated for both mutants. The b-wave delays were enhanced in mice doubly homozygous for RGS7 and RGS11 gene disruptions beyond those seen for mice with defects in either one of the genes separately. GPR158 immunofluorescence was observed in many retinal cell types, but was especially bright in the photoreceptor inner segments. GPR158 knockdown via an shRNA transgene resulted in significantly reduced a-wave amplitude.
RGS7 and RGS11 both act in parallel to regulate the kinetics of ON bipolar cell responses, with differential impacts on the rod and cone pathways. GPR158 acts to regulate the amplitude of the a-wave, likely through effects on photoreceptor dark current.
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