Direct binding of RalA to PKCη and its crucial role in morphological change during keratinocyte differentiation.
Direct binding of RalA to PKCη and its crucial role in morphological change during keratinocyte differentiation.
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DOI：
10.1091/mbc.e10-09-0754
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发表时间：
2011-04-15
影响因子：
3.3
通讯作者：
Saito N
中科院分区：
文献类型：
--
作者：
Shirai Y;Morioka S;Sakuma M;Yoshino K;Otsuji C;Sakai N;Kashiwagi K;Chida K;Shirakawa R;Horiuchi H;Nishigori C;Ueyama T;Saito N
小G蛋白Rala被鉴定为PKCη的结合伙伴。这种结合导致Rala的激活和与角质形成细胞分化相关的肌动蛋白解聚。这些结果为细胞骨架调节导致细胞形状剧烈变化的分子机制提供了新的见解。在分化过程中，角质形成细胞除了产生形成表皮所必需的蛋白质外，还经历了从小而圆到大而平的戏剧性形状变化。已有研究表明，蛋白激酶Cη对角质形成细胞的分化起着至关重要的作用。然而，它在这一过程中的作用尚未完全阐明。在这里，我们表明，尽管催化活性对于标记蛋白的基因表达是重要的，但对于过表达PKCη诱导的人角质形成细胞的扩大和扁平的形态来说，催化活性是不必要的。此外，我们还鉴定了小G蛋白Rala是PKCη的结合伙伴，它与C1域结合，而C1域是细胞形态变化不可或缺的区域。结合导致Rala激活和肌动蛋白解聚与角质形成细胞分化相关。小干扰RNA技术证明，Rala不仅参与了蛋白激酶Cη过表达诱导的角质形成细胞分化，而且还参与了钙和胆固醇硫酸盐诱导的角质形成细胞的正常分化。这些结果为揭示细胞骨架调控导致细胞形态剧烈变化的分子机制提供了新的视角。
A small G protein, RalA, was identified as a binding partner of PKCη. The binding led to activation of RalA and actin depolymerization associated with keratinocyte differentiation. These results provide new insight into the molecular mechanism of cytoskeletal regulation that leads to drastic change of cell shape. During differentiation, keratinocytes undergo a dramatic shape change from small and round to large and flat, in addition to production of proteins necessary for the formation of epidermis. It has been shown that protein kinase C (PKC) η is crucial for keratinocyte differentiation. However, its role in this process has yet to be fully elucidated. Here, we show that catalytic activity is not necessary for enlarged and flattened morphology of human keratinocytes induced by overexpression of PKCη, although it is important for gene expression of the marker proteins. In addition, we identify the small G protein RalA as a binding partner of PKCη, which binds to the C1 domain, an indispensable region for the morphological change. The binding led activation of RalA and actin depolymerization associated with keratinocyte differentiation. siRNA techniques proved that RalA is involved in not only the keratinocyte differentiation induced by PKCη overexpression but also normal keratinocyte differentiation induced by calcium and cholesterol sulfate. These results provide a new insight into the molecular mechanism of cytoskeletal regulation leading to drastic change of cell shape.