Lamellipodium tip actin barbed ends serve as a force sensor
Lamellipodium tip actin barbed ends serve as a force sensor
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DOI：
10.1111/gtc.12720
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发表时间：
2019-11-01
期刊：
影响因子：
2.1
通讯作者：
Watanabe, Naoki
中科院分区：
文献类型：
--
作者：
Koseki, Kazuma;Taniguchi, Daisuke;Watanabe, Naoki
细胞通过感知环境的刚性和牵引力改变迁移方向，但其潜在机制尚不清楚。在这里，我们展示了尖端肌动蛋白倒钩末端作为一个主动的“力传感器”在前缘。我们建立了一种通过弹性培养底物观察细胞内单分子荧光肌动蛋白的方法。我们发现，在细胞边缘拉伸后，肌动蛋白的组装在板基顶端增加。肌动蛋白组装率随拉伸速度的增加而增加。此外，在随后的保持步骤中，尖端肌动蛋白聚合保持升高，这伴随着尖端倒刺端负载的减少。在没有WAVE复合物或Ena/VASP蛋白的情况下，拉伸诱导的尖端肌动蛋白聚合仍然被观察到。观察到的力与尖端肌动蛋白聚合之间的关系与布朗棘轮机制预测的力-速度关系一致。拉伸引起相对于拉伸底物的膜外突出，并在30秒内增加了细胞总肌动蛋白的5%的局部尖端聚合。我们的数据显示，板基顶端肌动蛋白组装的增加与负载的减少直接耦合，这可能作为定向细胞突出的力传感器。
Cells change direction of migration by sensing rigidity of environment and traction force, yet its underlying mechanism is unclear. Here, we show that tip actin barbed ends serve as an active "force sensor" at the leading edge. We established a method to visualize intracellular single-molecule fluorescent actin through an elastic culture substrate. We found that immediately after cell edge stretch, actin assembly increased specifically at the lamellipodium tip. The rate of actin assembly increased with increasing stretch speed. Furthermore, tip actin polymerization remained elevated at the subsequent hold step, which was accompanied by a decrease in the load on the tip barbed ends. Stretch-induced tip actin polymerization was still observed without either the WAVE complex or Ena/VASP proteins. The observed relationships between forces and tip actin polymerization are consistent with a force-velocity relationship as predicted by the Brownian ratchet mechanism. Stretch caused extra membrane protrusion with respect to the stretched substrate and increased local tip polymerization by >5% of total cellular actin in 30 s. Our data reveal that augmentation of lamellipodium tip actin assembly is directly coupled to the load decrease, which may serve as a force sensor for directed cell protrusion.