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.

中文翻译：

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斑马鱼中松果体双稳态视蛋白对品视蛋白失活的视蛋白激酶的功能鉴定

在斑马鱼幼虫的松果体器官中，仅双稳态视蛋白对品视蛋白会在紫外线和可见光之间产生色差。我们以前的研究表明，激活G蛋白的副品视蛋白光产物的黑暗灭活对于调节光产物的量很重要。继而，光产物负责颜色对手性中的可见光敏感性。在这里，我们发现视蛋白激酶或G蛋白偶联受体激酶（GRK）参与了斑马鱼幼虫的松果体感光细胞中副品视蛋白活性光产物的失活。我们通过使用钙成像测量细胞的光响应，研究了各种敲低幼虫的对虾视蛋白细胞中光产物的失活。我们发现，GRK7a敲低减慢了对品索蛋白感光细胞反应的恢复，而GRK1b敲除或GRK7b敲除没有明显的作用，这表明圆锥型GRK GRK7a的主要作用是使斑马鱼幼虫中的对脂视蛋白光产品失活。 。我们还观察到对表达视蛋白SWS1（对紫外线敏感的视锥蛋白）而不是对视蛋白的突变体幼虫的对视蛋白的光感受器细胞的响应具有类似的抑制作用，这表明对视蛋白的光产物以类似于对视锥描述的方式被灭活视蛋白。我们通过比较敲除GRK7a和对照幼虫中对GRK7的免疫反应性，证实了对品视蛋白感光细胞中GRK7a的免疫组织化学分布。这些发现表明，在松果体感光细胞中，