Department of Chemical Engineering, University of Florida, Gainesville, Florida, USA.
Biophys J. 2010 Jul 7;99(1):115-23. doi: 10.1016/j.bpj.2010.04.011.
Endothelial cell polarization and directional migration is required for angiogenesis. Polarization and motility requires not only local cytoskeletal remodeling but also the motion of intracellular organelles such as the nucleus. However, the physiological significance of nuclear positioning in the endothelial cell has remained largely unexplored. Here, we show that siRNA knockdown of nesprin-1, a protein present in the linker of nucleus to cytoskeleton complex, abolished the reorientation of endothelial cells in response to cyclic strain. Confocal imaging revealed that the nuclear height is substantially increased in nesprin-1 depleted cells, similar to myosin inhibited cells. Nesprin-1 depletion increased the number of focal adhesions and substrate traction while decreasing the speed of cell migration; however, there was no detectable change in nonmuscle myosin II activity in nesprin-1 deficient cells. Together, these results are consistent with a model in which the nucleus balances a portion of the actomyosin tension in the cell. In the absence of nesprin-1, actomyosin tension is balanced by the substrate, leading to abnormal adhesion, migration, and cyclic strain-induced reorientation.
内皮细胞的极化和定向迁移是血管生成所必需的。极化和迁移不仅需要局部细胞骨架重塑，还需要细胞内细胞器（如核）的运动。然而，核在内皮细胞中的定位的生理意义在很大程度上仍未得到探索。在这里，我们表明， linker of nucleus to cytoskeleton complex 中的 nesprin-1 蛋白的 siRNA 敲低，会消除内皮细胞对周期性应变的重新定向。共聚焦成像显示，在 nesprin-1 耗尽的细胞中，核的高度显著增加，类似于肌球蛋白抑制的细胞。nesprin-1 耗尽增加了黏附斑的数量和基质牵引力，同时降低了细胞迁移速度；然而，在 nesprin-1 缺陷细胞中，非肌球蛋白 II 活性没有检测到明显变化。总之，这些结果与核在细胞中平衡一部分肌动球蛋白张力的模型一致。在没有 nesprin-1 的情况下，肌动球蛋白张力由基质平衡，导致异常黏附、迁移和周期性应变诱导的重新定向。
