Abstract
The melanopsin photopigment is an opsin class of G-protein coupled receptor (GPCR) playing a key role in the regulation of nonvisual photic responses. Upon activation, most mammalian GPCRs are phosphorylated in the C-terminal region by G-protein receptor kinases, which serve to recruit arrestin. Arrestin-binding often competes with G-protein for GPCR interaction and constitutes the mechanism of deactivation. We previously showed that ectopically expressed melanopsin produced a photocurrent in Xenopus oocytes supplemented with all-trans retinal in the presence of beta-arrestin. To understand the regulation of melanopsin function, here we investigated the role of arrestin. Photoactivated melanopsin was Ser/Thr phosphorylated at multiple sites in its C-terminal region. Deletion of this region did not affect photoactivation of melanopsin but attenuated the arrestin dependent deactivation. We propose that arrestin plays an important role in the deactivation of melanopsin by binding to the phosphorylated C-terminal region of melanopsin.