Two UV-Sensitive Photoreceptor Proteins, Opn5m and Opn5m2 in Ray-Finned Fish with Distinct Molecular Properties and Broad Distribution in the Retina and Brain.
Two UV-Sensitive Photoreceptor Proteins, Opn5m and Opn5m2 in Ray-Finned Fish with Distinct Molecular Properties and Broad Distribution in the Retina and Brain.
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DOI：
10.1371/journal.pone.0155339
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Shichida Y
中科院分区：
文献类型：
--
作者：
Sato K;Yamashita T;Haruki Y;Ohuchi H;Kinoshita M;Shichida Y
Opn5是视蛋白家族中的一组，负责动物的视觉和非视觉光接受。它由几个亚群组成，包括Opn5m，这是在大多数脊椎动物（包括哺乳动物）中发现的唯一包含成员的亚群。此外，最近的基因组信息显示，一些鳐鱼携带Opn5m的旁系基因，而另一些鱼类则没有这种基因。在这里，我们报告了现在称为Opn5m2的视蛋白的分子特性及其在视网膜和大脑中的分布。与Opn5m一样，Opn5m2与11-顺式视网膜结合时表现出紫外光敏感性，并与G蛋白的Gi亚型偶联形成稳定的活性状态。然而，Opn5m2不结合全反式视网膜，只与11-顺式视网膜结合，而许多双稳定视蛋白，包括鱼类的Opn5m，可以直接结合全反式视网膜和11-顺式视网膜。由于medaka鱼在基因组中丢失了Opn5m2基因，我们比较了Opn5m在medaka鱼、斑马鱼和斑点gar中的组织分布模式，以及Opn5m2在斑马鱼和斑点gar中的分布模式。Opn5m的表达水平沿视网膜背腹轴呈梯度分布，且在视网膜腹侧优先表达。Opn5m2在视网膜背侧呈优先表达的梯度。Opn5m在内核层内侧表达相对丰富，而Opn5m2在内核层外缘表达。此外，我们可以在这些鱼类的几个大脑区域（包括下丘脑）检测到Opn5m的表达。Opn5m2在斑马鱼的大脑中无法检测到表达，但在斑点雀的有限大脑区域中可以清楚地观察到表达。这些结果表明，鳐鱼通常可以利用紫外线信息在视网膜和大脑的广泛细胞中进行非图像形成的光接收。
Opn5 is a group within the opsin family of proteins that is responsible for visual and non-visual photoreception in animals. It consists of several subgroups, including Opn5m, the only subgroup containing members found in most vertebrates, including mammals. In addition, recent genomic information has revealed that some ray-finned fishes carry paralogous genes of Opn5m while other fishes have no such genes. Here, we report the molecular properties of the opsin now called Opn5m2 and its distributions in both the retina and brain. Like Opn5m, Opn5m2 exhibits UV light-sensitivity when binding to 11-cis-retinal and forms a stable active state that couples with Gi subtype of G protein. However, Opn5m2 does not bind all-trans-retinal and exhibits exclusive binding to 11-cis-retinal, whereas many bistable opsins, including fish Opn5m, can bind directly to all-trans-retinal as well as 11-cis-retinal. Because medaka fish has lost the Opn5m2 gene from its genome, we compared the tissue distribution patterns of Opn5m in medaka fish, zebrafish, and spotted gar, in addition to the distribution patterns of Opn5m2 in zebrafish and spotted gar. Opn5m expression levels showed a gradient along the dorsal–ventral axis of the retina, and preferential expression was observed in the ventral retina in the three fishes. The levels of Opn5m2 showed a similar gradient with preferential expression observed in the dorsal retina. Opn5m expression was relatively abundant in the inner region of the inner nuclear layer, while Opn5m2 was expressed in the outer edge of the inner nuclear layer. Additionally, we could detect Opn5m expression in several brain regions, including the hypothalamus, of these fish species. Opn5m2 expression could not be detected in zebrafish brain, but was clearly observed in limited brain regions of spotted gar. These results suggest that ray-finned fishes can generally utilize UV light information for non-image-forming photoreception in a wide range of cells in the retina and brain.