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K. A. Martemyanov, J. H. Song, H. Song, M. Sokolov; Localization and Interactions of R7 RGS Proteins With Their Membrane Anchors R7BP and R9AP in Neurons of Vertebrate Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2947.
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© ARVO (1962-2015); The Authors (2016-present)
Signaling via heterotrimeric G proteins is essential for retina function. The timing of G protein signaling is crucially regulated by Regulators of G protein Signaling (RGS) proteins which act to stimulate the rate of the G protein inactivation. RGS proteins of the R7 subfamily (R7 RGS) are believed to play important roles in the regulation of signaling in retina neurons. Recent findings indicate that R7 RGS proteins form complexes with two newly identified membrane anchors: RGS9 Anchor Protein (R9AP) and R7 Binding Protein (R7BP). In this study we evaluated the distribution of R7 RGS proteins in the retina and studied their association with R7BP and R9AP.
The association between individual R7 RGS proteins and their anchors was investigated by immunoprecipitation. Expression and compartmentalization of the signaling complexes across retina neurons was determined by two complementary approaches: serial sectioning with Western blotting and immunofluorescence staining.
We found that four R7 RGS proteins: RGS6, RGS7, RGS9 and RGS11 differentially associate with their two membrane anchors, R7BP and R9AP. While R9AP was found to be the predominant anchor in the photoreceptors, where it associates with RGS9 and RGS11, R7BP was mostly found in the inner retina, where it forms complexes with RGS6 and RGS7 and RGS11. Specifically, R7BP complexes with R7 RGS proteins appeared to be enriched in the synaptic projections of retina neurons within both the outer and inner plexiform layers. Studies of R9AP knockout mice revealed that R9AP is necessary for the expression of only RGS9 but not for RGS6, 7 or 11, suggesting that those proteins are regulated by R7BP, which they associate with even in the absence of R9AP.
Co-localization and interactions of R7 RGS proteins with R7BP in synaptic structures of the retina suggest a role for these complexes in the regulation of synaptic transmission between retina neurons.
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