Differential Regulation of Adhesion Complex Turnover by ROCK1 and ROCK2

BackgroundROCK1 and ROCK2 are serine/threonine kinases that function downstream of the small GTP-binding protein RhoA. Rho signalling via ROCK regulates a number of cellular functions including organisation of the actin cytoskeleton, cell adhesion and cell migration. Methodology/Principal FindingsIn this study we use RNAi to specifically knockdown ROCK1 and ROCK2 and analyse their role in assembly of adhesion complexes in human epidermal keratinocytes. We observe that loss of ROCK1 inhibits signalling via focal adhesion kinase resulting in a failure of immature adhesion complexes to form mature stable focal adhesions. In contrast, loss of ROCK2 expression results in a significant reduction in adhesion complex turnover leading to formation of large, stable focal adhesions. Interestingly, loss of either ROCK1 or ROCK2 expression significantly impairs cell migration indicating both ROCK isoforms are required for normal keratinocyte migration. ConclusionsROCK1 and ROCK2 have distinct and separate roles in adhesion complex assembly and turnover in human epidermal keratinocytes.

研究背景
ROCK1与ROCK2均为丝氨酸/苏氨酸激酶（serine/threonine kinases），作为小GTP结合蛋白RhoA的下游效应分子发挥功能。Rho信号通路通过ROCK调控诸多细胞生命活动，包括肌动蛋白细胞骨架（actin cytoskeleton）的组装、细胞黏附以及细胞迁移。

方法学与主要研究结果
本研究利用RNA干扰（RNA interference，RNAi）技术特异性敲低ROCK1与ROCK2的表达，分析二者在人表皮角质细胞（human epidermal keratinocytes）黏附复合物组装过程中的作用。研究发现，ROCK1的缺失会抑制黏着斑激酶（focal adhesion kinase）介导的信号通路，导致未成熟黏附复合物无法形成成熟稳定的黏着斑。与之相反，ROCK2表达缺失会显著降低黏附复合物的周转速率，进而形成大型稳定的黏着斑。值得注意的是，无论是敲低ROCK1还是ROCK2的表达，均会显著损害细胞迁移能力，提示两种ROCK亚型对于角质细胞的正常迁移均不可或缺。

研究结论
ROCK1与ROCK2在人表皮角质细胞的黏附复合物组装与周转过程中，发挥着截然不同且相互独立的生物学功能。