Functional identification of an opsin kinase underlying inactivation of the pineal bistable opsin parapinopsin in zebrafish

Zoological Letters

Baoguo Shen¹  Takashi Nagata¹  Haruka Nishioka¹  Emi Kawano-Yamashita²  Mitsumasa Koyanagi³  Akihisa Terakita³  Seiji Wada³ 

[1] Department of Biology and Geosciences, Graduate School of Science, Osaka City University, 558-8585, Osaka, Japan;Department of Biology and Geosciences, Graduate School of Science, Osaka City University, 558-8585, Osaka, Japan;Department of Chemistry, Biology, and Environmental Science, Faculty of Science, Nara Women’s University, Kitauoyanishi-machi, 630-8506, Nara, Japan;Department of Biology and Geosciences, Graduate School of Science, Osaka City University, 558-8585, Osaka, Japan;The OCU Advanced Research Institute for Natural Science and Technology, Osaka City University, 558-8585, Osaka, Japan;

关键词: Nonvisual photoreception;    Pineal organs;    Bistable opsin;    G-protein-coupled receptor kinase;    Opsin inactivation;   

DOI  :  10.1186/s40851-021-00171-1

来源: Springer

【 摘 要 】

In the pineal organ of zebrafish larvae, the bistable opsin parapinopsin alone generates color opponency between UV and visible light. Our previous study suggested that dark inactivation of the parapinopsin photoproduct, which activates G-proteins, is important for the regulation of the amount of the photoproduct. In turn, the photoproduct is responsible for visible light sensitivity in color opponency. Here, we found that an opsin kinase or a G-protein-coupled receptor kinase (GRK) is involved in inactivation of the active photoproduct of parapinopsin in the pineal photoreceptor cells of zebrafish larvae. We investigated inactivation of the photoproduct in the parapinopsin cells of various knockdown larvae by measuring the light responses of the cells using calcium imaging. We found that GRK7a knockdown slowed recovery of the response of parapinopsin photoreceptor cells, whereas GRK1b knockdown or GRK7b knockdown did not have a remarkable effect, suggesting that GRK7a, a cone-type GRK, is mainly responsible for inactivation of the parapinopsin photoproduct in zebrafish larvae. We also observed a similar knockdown effect on the response of the parapinopsin photoreceptor cells of mutant larvae expressing the opsin SWS1, a UV-sensitive cone opsin, instead of parapinopsin, suggesting that the parapinopsin photoproduct was inactivated in a way similar to that described for cone opsins. We confirmed the immunohistochemical distribution of GRK7a in parapinopsin photoreceptor cells by comparing the immunoreactivity to GRK7 in GRK7a-knockdown and control larvae. These findings suggest that in pineal photoreceptor cells, the cone opsin kinase GRK7a contributes greatly to the inactivation of parapinopsin, which underlies pineal color opponency.

【 授权许可】

CC BY