Simões Sérgio de Matos, Mainieri Avantika, Zallen Jennifer A
Howard Hughes Medical Institute and 2 Developmental Biology Program, Sloan Kettering Institute, New York, NY 10065.
J Cell Biol. 2014 Feb 17;204(4):575-89. doi: 10.1083/jcb.201307070.
Actomyosin contraction generates mechanical forces that influence cell and tissue structure. During convergent extension in Drosophila melanogaster, the spatially regulated activity of the myosin activator Rho-kinase promotes actomyosin contraction at specific planar cell boundaries to produce polarized cell rearrangement. The mechanisms that direct localized Rho-kinase activity are not well understood. We show that Rho GTPase recruits Rho-kinase to adherens junctions and is required for Rho-kinase planar polarity. Shroom, an asymmetrically localized actin- and Rho-kinase-binding protein, amplifies Rho-kinase and myosin II planar polarity and junctional localization downstream of Rho signaling. In Shroom mutants, Rho-kinase and myosin II achieve reduced levels of planar polarity, resulting in decreased junctional tension, a disruption of multicellular rosette formation, and defective convergent extension. These results indicate that Rho GTPase activity is required to establish a planar polarized actomyosin network, and the Shroom actin-binding protein enhances myosin contractility locally to generate robust mechanical forces during axis elongation.
肌动球蛋白收缩产生影响细胞和组织结构的机械力。在黑腹果蝇的趋同延伸过程中，肌球蛋白激活剂Rho激酶的空间调控活性促进了特定平面细胞边界处的肌动球蛋白收缩，从而产生极化细胞重排。指导局部Rho激酶活性的机制尚不清楚。我们发现，Rho GTP酶将Rho激酶招募到黏附连接，并且是Rho激酶平面极性所必需的。Shroom是一种不对称定位的肌动蛋白和Rho激酶结合蛋白，它在Rho信号下游放大Rho激酶和肌球蛋白II的平面极性以及连接定位。在Shroom突变体中，Rho激酶和肌球蛋白II的平面极性水平降低，导致连接张力下降、多细胞玫瑰花结形成破坏以及趋同延伸缺陷。这些结果表明，Rho GTP酶活性是建立平面极化肌动球蛋白网络所必需的，并且Shroom肌动蛋白结合蛋白在轴伸长过程中局部增强肌球蛋白收缩力以产生强大的机械力。
