Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
Mol Biol Cell. 2012 Jun;23(11):2131-42. doi: 10.1091/mbc.E11-11-0937. Epub 2012 Apr 4.
Shroom (Shrm) proteins are essential regulators of cell shape and tissue morpho-logy during animal development that function by interacting directly with the coiled-coil region of Rho kinase (Rock). The Shrm-Rock interaction is sufficient to direct Rock subcellular localization and the subsequent assembly of contractile actomyosin networks in defined subcellular locales. However, it is unclear how the Shrm-Rock interaction is regulated at the molecular level. To begin investigating this issue, we present the structure of Shrm domain 2 (SD2), which mediates the interaction with Rock and is required for Shrm function. SD2 is a unique three-segmented dimer with internal symmetry, and we identify conserved residues on the surface and within the dimerization interface that are required for the Rock-Shrm interaction and Shrm activity in vivo. We further show that these residues are critical in both vertebrate and invertebrate Shroom proteins, indicating that the Shrm-Rock signaling module has been functionally and molecularly conserved. The structure and biochemical analysis of Shrm SD2 indicate that it is distinct from other Rock activators such as RhoA and establishes a new paradigm for the Rock-mediated assembly of contractile actomyosin networks.
蘑菇蛋白（Shrm）是动物发育过程中细胞形状和组织形态的重要调节因子，通过与Rho 激酶（Rock）的卷曲螺旋区直接相互作用发挥功能。Shrm-Rock 相互作用足以指导 Rock 亚细胞定位，以及随后在特定亚细胞位置组装收缩性肌动球蛋白网络。然而，目前尚不清楚蘑菇蛋白-Rock 相互作用如何在分子水平上进行调节。为了开始研究这个问题，我们展示了蘑菇蛋白结构域 2（SD2）的结构，它介导与 Rock 的相互作用，是蘑菇蛋白功能所必需的。SD2 是一个具有内部对称性的独特三片段二聚体，我们确定了表面和二聚化界面上的保守残基，这些残基对于 Rock-Shrm 相互作用和蘑菇蛋白体内活性是必需的。我们进一步表明，这些残基在脊椎动物和无脊椎动物的蘑菇蛋白中都是关键的，表明蘑菇蛋白-Rock 信号模块在功能和分子水平上都得到了保守。蘑菇蛋白 SD2 的结构和生化分析表明，它与其他 Rock 激活剂（如 RhoA）不同，并为 Rock 介导的收缩性肌动球蛋白网络组装建立了一个新的范例。
