Lawrence Berkeley National Laboratory, University of California, Berkeley, California, USA.
Biophys J. 2010 Nov 3;99(9):2775-83. doi: 10.1016/j.bpj.2010.08.071.
The ability of a cell to distribute contractile stresses across the extracellular matrix in a spatially heterogeneous fashion underlies many cellular behaviors, including motility and tissue assembly. Here we investigate the biophysical basis of this phenomenon by using femtosecond laser nanosurgery to measure the viscoelastic recoil and cell-shape contributions of contractile stress fibers (SFs) located in specific compartments of living cells. Upon photodisruption and recoil, myosin light chain kinase-dependent SFs located along the cell periphery display much lower effective elasticities and higher plateau retraction distances than Rho-associated kinase-dependent SFs located in the cell center, with severing of peripheral fibers uniquely triggering a dramatic contraction of the entire cell within minutes of fiber irradiation. Image correlation spectroscopy reveals that when one population of SFs is pharmacologically dissipated, actin density flows toward the other population. Furthermore, dissipation of peripheral fibers reduces the elasticity and increases the plateau retraction distance of central fibers, and severing central fibers under these conditions triggers cellular contraction. Together, these findings show that SFs regulated by different myosin activators exhibit different mechanical properties and cell shape contributions. They also suggest that some fibers can absorb components and assume mechanical roles of other fibers to stabilize cell shape.
细胞在细胞外基质中以空间异质的方式分配收缩力的能力是许多细胞行为的基础，包括运动和组织组装。在这里，我们通过使用飞秒激光纳米手术来测量位于活细胞特定隔室中的收缩力纤维 (SF) 的粘弹性反冲和细胞形状贡献，从而研究了这一现象的生物物理基础。在光解和反冲之后，沿着细胞边缘定位的肌球蛋白轻链激酶依赖性 SF 表现出比位于细胞中心的 Rho 相关激酶依赖性 SF 低得多的有效弹性和高得多的平台回缩距离，并且只有切断外围纤维会在纤维照射后几分钟内独特地引发整个细胞的剧烈收缩。图像相关光谱学揭示了当一种 SF 群体被药理学耗散时，肌动蛋白密度流向另一种 SF 群体。此外，外围纤维的耗散降低了中心纤维的弹性并增加了平台回缩距离，并且在这些条件下切断中心纤维会引发细胞收缩。总之，这些发现表明，由不同肌球蛋白激活剂调节的 SF 表现出不同的机械性能和细胞形状贡献。它们还表明，一些纤维可以吸收成分并承担其他纤维的机械作用，以稳定细胞形状。
