Sivaramakrishnan Sivaraj, Spudich James A
Department of Biochemistry, Stanford University, Stanford, CA 94305, USA.
J Cell Biol. 2009 Oct 5;187(1):53-60. doi: 10.1083/jcb.200906133. Epub 2009 Sep 28.
Unconventional myosins interact with the dense cortical actin network during processes such as membrane trafficking, cell migration, and mechanotransduction. Our understanding of unconventional myosin function is derived largely from assays that examine the interaction of a single myosin with a single actin filament. In this study, we have developed a model system to study the interaction between multiple tethered unconventional myosins and a model F-actin cortex, namely the lamellipodium of a migrating fish epidermal keratocyte. Using myosin VI, which moves toward the pointed end of actin filaments, we directly determine the polarity of the extracted keratocyte lamellipodium from the cell periphery to the cell nucleus. We use a combination of experimentation and simulation to demonstrate that multiple myosin VI molecules can coordinate to efficiently transport vesicle-size cargo over 10 microm of the dense interlaced actin network. Furthermore, several molecules of monomeric myosin VI, which are nonprocessive in single molecule assays, can coordinate to transport cargo with similar speeds as dimers.
非常规肌球蛋白在诸如膜运输、细胞迁移和机械转导等过程中与致密的皮质肌动蛋白网络相互作用。我们对非常规肌球蛋白功能的理解很大程度上源于检测单个肌球蛋白与单个肌动蛋白丝相互作用的实验。在本研究中，我们开发了一个模型系统，以研究多个拴系的非常规肌球蛋白与模型F-肌动蛋白皮质（即迁移的鱼类表皮角质形成细胞的片足）之间的相互作用。使用向肌动蛋白丝尖端移动的肌球蛋白VI，我们直接确定了从细胞周边到细胞核的提取角质形成细胞片足的极性。我们结合实验和模拟来证明，多个肌球蛋白VI分子可以协同作用，在10微米的致密交错肌动蛋白网络上有效地运输囊泡大小的货物。此外，在单分子实验中无连续性的几个单体肌球蛋白VI分子可以协同作用，以与二聚体相似的速度运输货物。
