Cofilin drives rapid turnover and fluidization of entangled F-actin
Cofilin drives rapid turnover and fluidization of entangled F-actin
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DOI：
10.1073/pnas.1818808116
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发表时间：
2019-06-25
影响因子：
11.1
通讯作者：
Gardel, Margaret L.
中科院分区：
文献类型：
--
作者：
McCall, Patrick M.;MacKintosh, Frederick C.;Gardel, Margaret L.
大多数动物细胞的形状是由肌动蛋白皮质控制的，肌动蛋白皮质是一种位于质膜下方的动态肌动蛋白丝（F-肌动蛋白）的薄网络。皮质被主动应力和聚合物周转保持远离平衡：分子马达驱动细胞形态发生所需的变形，而肌动蛋白丝分解动力学放松应力并促进皮质重塑。虽然肌动蛋白皮质力学的许多方面都很好的特点，非平衡肌动蛋白营业额如何有助于应力松弛的机械理解仍然缺乏。为了解决这个问题，我们开发了一个重组的缠绕F-肌动蛋白的体外系统，其中的稳态长度和周转率的F-肌动蛋白的肌动蛋白调节蛋白cofilin，profilin，和cofilin，切断，回收，并组装细丝，分别控制。Cofilin介导的切断加速了F-肌动蛋白的周转和空间重组，而对细丝长度没有显着变化。我们证明，cofilin介导的切断是一个单一的时间尺度模式的应力松弛，调谐低频粘度超过两个数量级。这些研究结果作为理解更多生理F-肌动蛋白网络与营业额的机制的基础，并通知更新的微观模型的单丝营业额。他们还证明，以与核苷酸依赖性cofilin结合偶联的F-肌动蛋白上的ATP水解形式的聚合物活性足以产生一种活性物质形式，其中不对称的细丝拆卸保持细丝数量，尽管持续切断。
The shape of most animal cells is controlled by the actin cortex, a thin network of dynamic actin filaments (F-actin) situated just beneath the plasma membrane. The cortex is held far from equilibrium by both active stresses and polymer turnover: Molecular motors drive deformations required for cell morphogenesis, while actin-filament disassembly dynamics relax stress and facilitate cortical remodeling. While many aspects of actin-cortex mechanics are well characterized, a mechanistic understanding of how non-equilibrium actin turnover contributes to stress relaxation is still lacking. To address this, we developed a reconstituted in vitro system of entangled F-actin, wherein the steady-state length and turnover rate of F-actin are controlled by the actin regulatory proteins cofilin, profilin, and formin, which sever, recycle, and assemble filaments, respectively. Cofilin-mediated severing accelerates the turnover and spatial reorganization of F-actin, without significant changes to filament length. We demonstrate that cofilin-mediated severing is a single-timescale mode of stress relaxation that tunes the low-frequency viscosity over two orders of magnitude. These findings serve as the foundation for understanding the mechanics of more physiological F-actin networks with turnover and inform an updated microscopic model of single-filament turnover. They also demonstrate that polymer activity, in the form of ATP hydrolysis on F-actin coupled to nucleotide-dependent cofilin binding, is sufficient to generate a form of active matter wherein asymmetric filament disassembly preserves filament number despite sustained severing.