Opn5L1 is a retinal receptor that behaves as a reverse and self-regenerating photoreceptor

• DOI: 10.1038/s41467-018-03603-3
• Publication Date: 2018-04-04T02:49:28Z
• Authors: Keita Sato; Takahiro Yamashita; Hideyo Ohuchi; Atsuko Takeuchi; Hitoshi Gotoh; Katsuhiko Ono; Misao Mizuno; Yasuhisa Mizutani; Sayuri Tomonari; Kazumi Sakai; Yasushi Imamoto; Akimori Wada; Yoshinori Shichida
• Keywords: Male; 0301 basic medicine; Rhodopsin; Light; Science; Xenopus; 535; Biochemistry; Article; 03 medical and health sciences; G protein-coupled receptors; Animals; Humans; Regeneration; Photoreceptor Cells; Vitamin A; Chromatography, High Pressure Liquid; In Situ Hybridization; Opsins; Q; Recombinant Proteins; HEK293 Cells; Factor Xa; Retinaldehyde; Chickens; Photoreceptor Cells, Vertebrate; Protein Binding; Signal Transduction

AbstractMost opsins are G protein-coupled receptors that utilize retinal both as a ligand and as a chromophore. Opsins’ main established mechanism is light-triggered activation through retinal 11-cis-to-all-trans photoisomerization. Here we report a vertebrate non-visual opsin that functions as a Gi-coupled retinal receptor that is deactivated by light and can thermally self-regenerate. This opsin, Opn5L1, binds exclusively to all-trans-retinal. More interestingly, the light-induced deactivation through retinal trans-to-cis isomerization is followed by formation of a covalent adduct between retinal and a nearby cysteine, which breaks the retinal-conjugated double bond system, probably at the C11 position, resulting in thermal re-isomerization to all-trans-retinal. Thus, Opn5L1 acts as a reverse photoreceptor. We conclude that, like vertebrate rhodopsin, Opn5L1 is a unidirectional optical switch optimized from an ancestral bidirectional optical switch, such as invertebrate rhodopsin, to increase the S/N ratio of the signal transduction, although the direction of optimization is opposite to that of vertebrate rhodopsin.