Department of Anatomy, University of California, San Francisco, CA 94143, USA.
J Cell Sci. 2012 Sep 1;125(Pt 17):4147-57. doi: 10.1242/jcs.108670. Epub 2012 May 23.
Scribble was originally identified as a Drosophila protein that regulates epithelial polarity and formation of the basolateral surface. The mammalian orthologue, Scrib, is evolutionarily conserved, but does not appear to be necessary for apical-basolateral epithelial polarity. Instead, it is implicated in the regulation of cell survival, protein trafficking, adhesion and migration. A key issue is to understand the molecular pathway by which Scrib participates in these processes. We have investigated Scrib using a three-dimensional epithelial cell culture system. We show a novel association between the leucine-rich repeat domain of Scrib and the co-chaperone Sgt1 and demonstrate that these proteins are necessary for epithelial morphogenesis and tubulogenesis following hepatocyte growth factor (HGF) stimulation. The molecular chaperone HSP90 is also required for Sgt1 association with Scrib, and both Sgt1 and HSP90 are needed to ensure proper Scrib protein levels. Furthermore, reduced Scrib stability, following inhibition of Sgt1-HSP90, lowers the cellular abundance of the Scrib-βPix-PAK complex. Inhibition of any member of this complex, Scrib, βPix or PAK, is sufficient to block HGF-mediated epithelial morphogenesis. The identification of Scrib as an Sgt1-HSP90 client protein required for three-dimensional cell migration suggests that chaperone-mediated regulation of polarity protein stability and homeostasis is an unappreciated mechanism underlying dynamic rearrangements during morphogenesis.
Scribble 最初被鉴定为一种调节上皮细胞极性和基底外侧表面形成的果蝇蛋白。其哺乳动物直系同源物 Scrib 在进化上是保守的，但似乎对顶-底上皮极性不是必需的。相反，它参与细胞存活、蛋白质运输、黏附和迁移的调节。一个关键问题是要了解 Scrib 参与这些过程的分子途径。我们使用三维上皮细胞培养系统研究了 Scrib。我们发现 Scrib 的亮氨酸重复结构域与共伴侣 Sgt1 之间存在新的关联，并证明这些蛋白对于肝细胞生长因子 (HGF) 刺激后的上皮形态发生和小管形成是必需的。分子伴侣 HSP90 也需要 Sgt1 与 Scrib 的结合，并且 Sgt1 和 HSP90 都需要确保适当的 Scrib 蛋白水平。此外，抑制 Sgt1-HSP90 后 Scrib 的稳定性降低，降低了 Scrib-βPix-PAK 复合物在细胞中的丰度。抑制该复合物的任何成员，Scrib、βPix 或 PAK，足以阻止 HGF 介导的上皮形态发生。将 Scrib 鉴定为 Sgt1-HSP90 客户蛋白，是三维细胞迁移所必需的，这表明伴侣介导的极性蛋白稳定性和动态平衡的调节是形态发生过程中动态重排的一个未被认识的机制。
