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M. Hatori, Q. Zhu, S. V. Yelamanchili, V. Piamonte, N. Tanaka, S. Panda; The Role of Arrestin-Melanopsin Interaction in Melanopsin Function. Invest. Ophthalmol. Vis. Sci. 2008;49(13):186.
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We previously showed that ectopically expressed melanopsin produced a photocurrent in Xenopus oocytes supplemented with all-trans retinal only in the presence of beta-arrestin. To understand the role of arrestin in melanopsin function, we investigated the interaction mechanism of these two proteins.
Expression of two beta-arrestins - Arrb1 and Arrb2 in ipRGCs was analyzed by single cell qPCR. HEK-293 cells were transiently transfected with full-length or C-terminal truncated melanopsin and arrestin, and its interaction with arrestin was investigated by co-immunoprecipitation assay. HEK-293 cells transiently expressing melanopsin were metabolically labeled with 32P and stimulated by light. Melanopsin protein was immunoprecipitated, and the phosphorylation state was analyzed by autoradiography. Phospho amino acid analysis was performed by using phosphorylated melanopsin. Light-dependent changes in membrane current were analyzed by using Xenopus oocytes expressing melanopsin.
We found that both Arrb1 and Arrb2 were co-expressed with melanopsin in ipRGCs. These arrestins functionally interacted with melanopsin C-terminal region in heterologous expression systems. Photoactivated melanopsin was typically Serine phosphorylated at multiple sites in its C-terminal region, and deletion of this region did not affect photoactivation of melanopsin but attenuated the deactivation.
We propose that arrestin plays an important role in the deactivation of melanopsin by binding to the phosphorylated C-terminal region of melanopsin.
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