Focal adhesions are controlled by microtubules through local contractility regulation

Microtubules regulate cell polarity and migration via local activation of focal adhesion turnover, but the mechanism of this process is insufficiently understood. Molecular complexes containing KANK family proteins connect microtubules with talin, the major component of focal adhesions. Here, local optogenetic activation of KANK1-mediated microtubule/talin linkage promoted microtubule targeting to an individual focal adhesion and subsequent withdrawal, resulting in focal adhesion centripetal sliding and rapid disassembly. This sliding is preceded by a local increase of traction force due to accumulation of myosin-II and actin in the proximity of the focal adhesion. Knockdown of the Rho activator GEF-H1 prevented development of traction force and abolished sliding and disassembly of focal adhesions upon KANK1 activation. Other players participating in microtubule-driven, KANK-dependent focal adhesion disassembly include kinases ROCK, PAK and FAK, as well as microtubules/focal adhesion-associated proteins kinesin-1, APC, and αTAT. Based on these data, we develop a mathematical model for a microtubule-driven focal adhesion disruption involving local GEF-H1/RhoA/ROCK dependent activation of contractility, which is consistent with experimental data.

微管（Microtubules）可通过局部激活黏着斑（focal adhesion）周转调控细胞极性与细胞迁移，但该过程的具体分子机制尚未得到充分阐释。包含KANK家族蛋白（KANK family proteins）的分子复合物可将微管与黏着斑的核心组分踝蛋白（talin）相连。本研究中，对KANK1介导的微管/踝蛋白连接实施局部光遗传激活，可促进微管靶向单个黏着斑并随后发生回缩，最终引发黏着斑向心滑动与快速解离。该滑动发生前，黏着斑附近因肌球蛋白II（myosin-II）与肌动蛋白（actin）聚集，会出现局部牵引力升高现象。敲低（Knockdown）Rho激活因子GEF-H1可阻断牵引力的产生，并消除KANK1激活后黏着斑的滑动与解离过程。参与微管驱动、依赖KANK的黏着斑解离过程的其他调控因子包括激酶ROCK、PAK与黏着斑激酶（FAK，focal adhesion kinase），以及微管/黏着斑相关蛋白驱动蛋白-1（kinesin-1）、腺瘤性结肠息肉病蛋白（APC）与α微管蛋白乙酰转移酶（αTAT）。基于上述实验结果，我们构建了一个依赖局部GEF-H1/RhoA/ROCK激活细胞收缩性的微管驱动黏着斑解离数学模型，该模型与实验数据高度吻合。