Jules Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America.
PLoS One. 2011;6(6):e20707. doi: 10.1371/journal.pone.0020707. Epub 2011 Jun 27.
Retinoschisin is encoded by the gene responsible for X-linked retinoschisis (XLRS), an early onset macular degeneration that results in a splitting of the inner layers of the retina and severe loss in vision. Retinoschisin is predominantly expressed and secreted from photoreceptor cells as a homo-oligomer protein; it then associates with the surface of retinal cells and maintains the retina cellular architecture. Many missense mutations in the XLRS1 gene are known to cause intracellular retention of retinoschisin, indicating that the secretion process of the protein is a critical step for its normal function in the retina. However, the molecular mechanisms underlying retinoschisin's secretion remain to be fully elucidated. In this study, we investigated the role of the F-actin cytoskeleton in the secretion of retinoschisin by treating Weri-Rb1 cells, which are known to secrete retinoschisin, with cytochalasin D, jasplakinolide, Y-27632, and dibutyryl cGMP. Our results show that cytochalasin D and jasplakinolide inhibit retinoschisin secretion, whereas Y-27632 and dibutyryl cGMP enhance secretion causing F-actin alterations. We also demonstrate that high concentrations of taxol, which hyperpolymerizes microtubules, inhibit retinoschisin secretion. Our data suggest that retinoschisin secretion is regulated by the F-actin cytoskeleton, that cGMP or inhibition of ROCK alters F-actin structure enhancing the secretion, and that the microtubule cytoskeleton is also involved in this process.
视锥视蛋白是 X 连锁性视网膜劈裂症（XLRS）相关基因编码的蛋白，XLRS 是一种早期发病的黄斑变性疾病，会导致视网膜内层分裂和严重的视力丧失。视锥视蛋白主要在感光细胞中表达和分泌为同源寡聚体蛋白；然后它与视网膜细胞的表面结合并维持视网膜细胞的结构。已知 XLRS1 基因中的许多错义突变会导致视锥视蛋白在细胞内滞留，表明该蛋白的分泌过程是其在视网膜中正常功能的关键步骤。然而，视锥视蛋白分泌的分子机制仍有待充分阐明。在这项研究中，我们通过用细胞松弛素 D、jasplakinolide、Y-27632 和二丁酰环鸟苷处理已知分泌视锥视蛋白的 Weri-Rb1 细胞，研究了 F-肌动蛋白细胞骨架在视锥视蛋白分泌中的作用。我们的结果表明，细胞松弛素 D 和 jasplakinolide 抑制视锥视蛋白分泌，而 Y-27632 和二丁酰环鸟苷增强分泌导致 F-肌动蛋白结构改变。我们还证明，高浓度的紫杉醇（可使微管高度聚合）抑制视锥视蛋白分泌。我们的数据表明，视锥视蛋白的分泌受 F-肌动蛋白细胞骨架调节，cGMP 或 ROCK 抑制改变 F-肌动蛋白结构，增强分泌，微管细胞骨架也参与该过程。
