Section of Pathology, Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland.
Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
Cell Rep. 2018 Jul 3;24(1):11-19. doi: 10.1016/j.celrep.2018.06.011.
Stress fibers are contractile actomyosin bundles that guide cell adhesion, migration, and morphogenesis. Their assembly and alignment are under precise mechanosensitive control. Thus, stress fiber networks undergo rapid modification in response to changes in biophysical properties of the cell's surroundings. Stress fiber maturation requires mechanosensitive activation of 5'AMP-activated protein kinase (AMPK), which phosphorylates vasodilator-stimulated phosphoprotein (VASP) to inhibit actin polymerization at focal adhesions. Here, we identify Ca-calmodulin-dependent kinase kinase 2 (CaMKK2) as a critical upstream factor controlling mechanosensitive AMPK activation. CaMKK2 and Ca influxes were enriched around focal adhesions at the ends of contractile stress fibers. Inhibition of either CaMKK2 or mechanosensitive Ca channels led to defects in phosphorylation of AMPK and VASP, resulting in a loss of contractile bundles and a decrease in cell-exerted forces. These data provide evidence that Ca, CaMKK2, AMPK, and VASP form a mechanosensitive signaling cascade at focal adhesions that is critical for stress fiber assembly.
应力纤维是收缩性肌动球蛋白束，指导细胞黏附、迁移和形态发生。它们的组装和排列受到精确的机械敏感控制。因此，应力纤维网络会根据细胞周围生物物理特性的变化而迅速改变。应力纤维成熟需要 5'AMP 激活蛋白激酶（AMPK）的机械敏感激活，该激酶将血管扩张刺激磷蛋白（VASP）磷酸化，从而抑制黏附处的肌动蛋白聚合。在这里，我们确定钙调蛋白依赖性激酶激酶 2（CaMKK2）是控制机械敏感 AMPK 激活的关键上游因子。CaMKK2 和 Ca 流入在收缩性应力纤维末端的黏附处富集。抑制 CaMKK2 或机械敏感 Ca 通道会导致 AMPK 和 VASP 磷酸化缺陷，导致收缩束丢失和细胞施加的力减少。这些数据提供了证据，表明 Ca、CaMKK2、AMPK 和 VASP 在黏附处形成了一个机械敏感的信号级联，对于应力纤维组装至关重要。
