Micromechanics and ultrastructure of actin filament networks crosslinked by human fascin:: A comparison with α-actinin
Micromechanics and ultrastructure of actin filament networks crosslinked by human fascin:: A comparison with α-actinin
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DOI：
10.1006/jmbi.2001.4716
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发表时间：
2001-07-06
影响因子：
5.6
通讯作者：
Wirtz, D
中科院分区：
文献类型：
--
作者：
Tseng, Y;Fedorov, E;Wirtz, D
成束蛋白是一种肌动蛋白交联蛋白，其将肌动蛋白丝组织成紧密堆积的束，据信其介导细胞突起的形成并为应力纤维提供机械支撑。利用定量流变学方法，我们研究了在人肌成束蛋白存在下，丝状肌动蛋白（F-actin）网络组装的力学行为的演变。F-肌动蛋白/肌成束蛋白网络的机械性能直接与由α-辅肌动蛋白，一种原型肌动蛋白丝交联/捆绑蛋白形成的那些进行比较。在肌成束蛋白（肌成束蛋白与肌动蛋白的摩尔比>1：50）存在下，F-肌动蛋白网络的GdR表现出非单调的行为，其特征在于弹性的爆发，随后随着时间的推移缓慢下降。此外，凝胶化速率显示出对肌成束蛋白浓度的非单调依赖性。与此相反，α-辅肌动蛋白增加的F-肌动蛋白网络的弹性和凝胶化的速度单调。时间分辨多角度光散射和共聚焦和电子显微镜表明，这种独特的行为是由于竞争之间的fascin介导的交联和侧支化的肌动蛋白丝和束，一方面，延迟肌动蛋白组装和增强网络微观异质性，另一方面。不同频率的振荡剪切下的F-肌动蛋白/肌成束蛋白溶液的行为，其模拟细胞对以不同速率施加的力的响应，支持肌成束蛋白介导的F-肌动蛋白侧支化的关键作用。肌动蛋白侧支化促进了相互连接网络的形成，从而完全抑制了肌动蛋白丝和束的运动。因此，我们的结果表明，尽管共享看似相似的F-肌动蛋白交联/捆绑活性，α-辅肌动蛋白和肌成束蛋白显示完全不同的机械行为。当在活细胞中最近的微观流变测量的背景下，这些结果提供了理解多种交联蛋白之间的协同作用，特别是肌成束蛋白和α-辅肌动蛋白在体内的互补机械作用的基础。(C)北京：科学出版社.
Fascin is an actin crosslinking protein that organizes actin filaments into tightly packed bundles believed to mediate the formation of cellular protrusions and to provide mechanical support to stress fibers. Using quantitative rheological methods, we studied the evolution of the mechanical behavior of filamentous actin (F-actin) networks assembled in the presence of human fascin. The mechanical properties of F-actin/fascin networks were directly compared with those formed by a-actinin, a prototypical actin filament crosslinking/bundling protein. Gelation of F-actin networks in the presence of fascin (fascin to actin molar ratio >1:50) exhibits a non-monotonic behavior characterized by a burst of elasticity followed by a slow decline over time. Moreover, the rate of gelation shows a non-monotonic dependence on fascin concentration. In contrast, alpha -actinin increased the F-actin network elasticity and the rate of gelation monotonically. Time-resolved multiple-angle light scattering and confocal and electron microscopies suggest that this unique behavior is due to competition between fascin-mediated crosslinking and side-branching of actin filaments and bundles, on the one hand, and delayed actin assembly and enhanced network micro-heterogeneity, on the other hand. The behavior of F-actin/fascin solutions under oscillatory shear of different frequencies, which mimics the cell's response to forces applied at different rates, supports a key role for fascin-mediated F-actin side-branching. F-actin side-branching promotes the formation of interconnected networks, which completely inhibits the motion of actin filaments and bundles. Our results therefore show that despite sharing seemingly similar F-actin crosslinking/bundling activity, alpha -actinin and fascin display completely different mechanical behavior. When viewed in the context of recent microrheological measurements in living cells, these results provide the basis for understanding the synergy between multiple crosslinking proteins, and in particular the complementary mechanical roles of fascin and alpha -actinin in vivo. (C) 2001 Academic Press.