Interplay between Cytoskeletal Stresses and Cell Adaptation under Chronic Flow

Using stress sensitive FRET sensors we have measured cytoskeletal stresses in α-actinin and the associated reorganization of the actin cytoskeleton in cells subjected to chronic shear stress. We show that long-term shear stress reduces the average actinin stress and this effect is reversible with removal of flow. The flow-induced changes in cytoskeletal stresses are found to be dynamic, involving a transient decrease in stress (phase-I), a short-term increase (3–6 min) (Phase-II), followed by a longer-term decrease that reaches a minimum in ∼20 min (Phase-III), before saturating. These changes are accompanied by reorganization of the actin cytoskeleton from parallel F-actin bundles to peripheral bundles. Blocking mechanosensitive ion channels (MSCs) with Gd3+ and GsMTx4 (a specific inhibitor) eliminated the changes in cytoskeletal stress and the corresponding actin reorganization, indicating that Ca2+ permeable MSCs participate in the signaling cascades. This study shows that shear stress induced cell adaptation is mediated via MSCs.本研究采用应力敏感荧光共振能量转移（FRET）传感器，对暴露于慢性剪切应力的细胞内α-辅肌动蛋白（α-actinin）的细胞骨架应力及其伴随的肌动蛋白细胞骨架重排进行了定量检测。研究结果表明，长期剪切应力会降低细胞内α-辅肌动蛋白的平均应力，且该效应可通过移除流体剪切力实现逆转。研究发现，流体剪切力诱导的细胞骨架应力变化具有动态特性：首先出现应力短暂下降（I期），随后经历3~6分钟的短期升高（II期），继而发生长期下降并在约20分钟时达到最小值（III期），最终趋于饱和。上述应力变化同时伴随肌动蛋白细胞骨架的重排，即从平行F-肌动蛋白束转变为外周束。使用钆离子（Gd3+）与特异性抑制剂GsMTx4阻断机械敏感性离子通道（MSCs）后，细胞骨架应力的变化及对应的肌动蛋白重排均被完全消除，这表明钙离子通透性机械敏感性离子通道参与了该信号级联反应。本研究证实，剪切应力诱导的细胞适应过程是通过机械敏感性离子通道介导的。