Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America.
PLoS One. 2011;6(8):e22755. doi: 10.1371/journal.pone.0022755. Epub 2011 Aug 11.
Actin structures are often stable, remaining unchanged in organization for the lifetime of a differentiated cell. Little is known about stable actin structure formation, organization, or maintenance. During Drosophila spermatid individualization, long-lived actin cones mediate cellular remodeling. Myosin VI is necessary for building the dense meshwork at the cones' fronts. We test several ideas for myosin VI's mechanism of action using domain deletions or site-specific mutations of myosin VI. The head (motor) and globular tail (cargo-binding) domains were both needed for localization at the cone front and dense meshwork formation. Several conserved partner-binding sites in the globular tail previously identified in vertebrate myosin VI were critical for function in cones. Localization and promotion of proper actin organization were separable properties of myosin VI. A vertebrate myosin VI was able to localize and function, indicating that functional properties are conserved. Our data eliminate several models for myosin VI's mechanism of action and suggest its role is controlling organization and action of actin assembly regulators through interactions at conserved sites. The Drosophila orthologues of interaction partners previously identified for vertebrate myosin VI are likely not required, indicating novel partners mediate this effect. These data demonstrate that generating an organized and functional actin structure in this cell requires multiple activities coordinated by myosin VI.
肌动蛋白结构通常很稳定，在分化细胞的整个生命周期中保持不变。对于稳定的肌动蛋白结构的形成、组织或维持，人们知之甚少。在果蝇精原细胞个体化过程中，长寿命的肌动蛋白锥体介导细胞重塑。肌球蛋白 VI 对于在锥体前缘形成密集的网格至关重要。我们使用肌球蛋白 VI 的结构域缺失或特异性突变来测试几种关于肌球蛋白 VI 作用机制的想法。头部（马达）和球状尾部（货物结合）结构域对于在锥体前缘和密集网格的形成中的定位都是必需的。以前在脊椎动物肌球蛋白 VI 中鉴定的球状尾部中的几个保守的伙伴结合位点对于锥体中的功能至关重要。肌球蛋白 VI 的定位和促进适当的肌动蛋白组织的能力是可分离的。一种脊椎动物肌球蛋白 VI 能够定位和发挥作用，表明其功能特性是保守的。我们的数据排除了几种肌球蛋白 VI 作用机制的模型，并表明其作用是通过保守位点的相互作用来控制肌动蛋白组装调节剂的组织和功能。以前为脊椎动物肌球蛋白 VI 鉴定的相互作用伙伴的果蝇同源物可能不是必需的，这表明新的伙伴介导了这种效应。这些数据表明，在这个细胞中产生有组织和功能的肌动蛋白结构需要由肌球蛋白 VI 协调的多种活性。
