β-arrestin functionally regulates the non-bleaching pigment parapinopsin in lamprey pineal.
β-arrestin functionally regulates the non-bleaching pigment parapinopsin in lamprey pineal.
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DOI：
10.1371/journal.pone.0016402
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发表时间：
2011-01-31
期刊：
影响因子：
3.7
通讯作者：
Terakita A
中科院分区：
文献类型：
--
作者：
Kawano-Yamashita E;Koyanagi M;Shichida Y;Oishi T;Tamotsu S;Terakita A
脊椎动物视觉细胞的光反应是通过光敏感蛋白如视蛋白基色素以及信号转导蛋白，包括视觉抑制蛋白来实现的。以往的研究表明，松果体色素类视蛋白具有重要的进化和生理特性。副视蛋白与脊椎动物的视色素在遗传学上相关。然而，与视色素视紫红质的光产物不同，视紫红质的光产物是不稳定的，从其发色团解离并漂白，副视紫红质光产物是稳定的，并且不释放其发色团。在这里，我们调查arrestin，调节视神经信号，在七鳃鳗松果体器官，视神经和视紫红质定位于不同的感光细胞。我们发现，β-抑制蛋白，它结合到刺激G蛋白偶联受体（GPCR）以外的视蛋白为基础的色素，被定位到含副视蛋白的细胞。这一结果与视紫红质细胞中视觉抑制蛋白的定位相反。β-arrestin结合到培养的细胞膜含有视神经肽光依赖性和易位到外段的松果体视神经肽含有细胞，表明β-arrestin结合到视神经肽逮捕视神经肽信号。有趣的是，在光照下，β-arrestin与副视蛋白共定位在表达副视蛋白的细胞体的颗粒中。由于β-抑制蛋白是网格蛋白介导的GPCR内化的介质，也是培养细胞中的副视蛋白内化的介质，因此这些结果表明，颗粒是通过β-抑制蛋白介导的来自外节的副视蛋白内化而光依赖性地产生的。因此，我们的研究结果表明，β-arrestin介导的内化是负责消除稳定的光产物和恢复细胞条件到原来的黑暗状态。结合先前的发现，漂白色素从非漂白色素进化而来，脊椎动物视觉抑制蛋白可能是从“β样”抑制蛋白进化而来的，失去了其网格蛋白结合结构域及其作为内化介质的功能。这种变化可能是脊椎动物视色素进化的结果，视色素产生不稳定的光产物，通过发色团解离而独立衰变。
The light response of vertebrate visual cells is achieved by light-sensing proteins such as opsin-based pigments as well as signal transduction proteins, including visual arrestin. Previous studies have indicated that the pineal pigment parapinopsin has evolutionally and physiologically important characteristics. Parapinopsin is phylogenetically related to vertebrate visual pigments. However, unlike the photoproduct of the visual pigment rhodopsin, which is unstable, dissociating from its chromophore and bleaching, the parapinopsin photoproduct is stable and does not release its chromophore. Here, we investigated arrestin, which regulates parapinopsin signaling, in the lamprey pineal organ, where parapinopsin and rhodopsin are localized to distinct photoreceptor cells. We found that beta-arrestin, which binds to stimulated G protein-coupled receptors (GPCRs) other than opsin-based pigments, was localized to parapinopsin-containing cells. This result stands in contrast to the localization of visual arrestin in rhodopsin-containing cells. Beta-arrestin bound to cultured cell membranes containing parapinopsin light-dependently and translocated to the outer segments of pineal parapinopsin-containing cells, suggesting that beta-arrestin binds to parapinopsin to arrest parapinopsin signaling. Interestingly, beta-arrestin colocalized with parapinopsin in the granules of the parapinopsin-expressing cell bodies under light illumination. Because beta-arrestin, which is a mediator of clathrin-mediated GPCR internalization, also served as a mediator of parapinopsin internalization in cultured cells, these results suggest that the granules were generated light-dependently by beta-arrestin-mediated internalization of parapinopsins from the outer segments. Therefore, our findings imply that beta-arrestin-mediated internalization is responsible for eliminating the stable photoproduct and restoring cell conditions to the original dark state. Taken together with a previous finding that the bleaching pigment evolved from a non-bleaching pigment, vertebrate visual arrestin may have evolved from a “beta-like” arrestin by losing its clathrin-binding domain and its function as an internalization mediator. Such changes would have followed the evolution of vertebrate visual pigments, which generate unstable photoproducts that independently decay by chromophore dissociation.
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