Department of Biology, University of Utah, Salt Lake City, Utah, United States of America.
PLoS One. 2013 Aug 21;8(8):e69378. doi: 10.1371/journal.pone.0069378. eCollection 2013.
Contractile actomyosin stress fibers are critical for maintaining the force balance between the interior of the cell and its environment. Consequently, the actin cytoskeleton undergoes dynamic mechanical loading. This results in spontaneous, stochastic, highly localized strain events, characterized by thinning and elongation within a discrete region of stress fiber. Previous work showed the LIM-domain adaptor protein, zyxin, is essential for repair and stabilization of these sites. Using live imaging, we show paxillin, another LIM-domain adaptor protein, is also recruited to stress fiber strain sites. Paxillin recruitment to stress fiber strain sites precedes zyxin recruitment. Zyxin and paxillin are each recruited independently of the other. In cells lacking paxillin, actin recovery is abrogated, resulting in slowed actin recovery and increased incidence of catastrophic stress fiber breaks. For both paxillin and zyxin, the LIM domains are necessary and sufficient for recruitment. This work provides further evidence of the critical role of LIM-domain proteins in responding to mechanical stress in the actin cytoskeleton.
收缩性肌动球蛋白应力纤维对于维持细胞内部和环境之间的力平衡至关重要。因此，肌动蛋白细胞骨架会受到动态机械加载。这会导致自发、随机、高度局部的应变事件，其特征是在应力纤维的离散区域内变薄和伸长。先前的工作表明 LIM 结构域衔接蛋白 zyxin 对于这些位点的修复和稳定是必不可少的。通过实时成像，我们发现另一种 LIM 结构域衔接蛋白 paxillin 也被招募到应力纤维应变位点。paxillin 向应力纤维应变位点的募集先于 zyxin 的募集。zyxin 和 paxillin 的募集彼此独立。在缺乏 paxillin 的细胞中，肌动蛋白的恢复被阻断，导致肌动蛋白恢复减慢，灾难性的应力纤维断裂的发生率增加。对于 paxillin 和 zyxin 来说，LIM 结构域是招募所必需和充分的。这项工作进一步证明了 LIM 结构域蛋白在响应肌动蛋白细胞骨架中的机械应激方面的关键作用。
