Retrograde Flow and Myosin II Activity within the Leading Cell Edge Deliver F-Actin to the Lamella to Seed the Formation of Graded Polarity Actomyosin II Filament Bundles in Migrating Fibroblasts
Retrograde Flow and Myosin II Activity within the Leading Cell Edge Deliver F-Actin to the Lamella to Seed the Formation of Graded Polarity Actomyosin II Filament Bundles in Migrating Fibroblasts
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DOI：
10.1091/mbc.e08-01-0034
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发表时间：
2008-11-01
影响因子：
3.3
通讯作者：
Cramer, Louise P.
中科院分区：
文献类型：
--
作者：
Anderson, Tom W.;Vaughan, Andrew N.;Cramer, Louise P.
在迁移的成纤维细胞中，肌动球蛋白II束是极性渐变（GP）束，这是一种与应力纤维不同的组织结构。GP束对驱动细胞迁移很重要，但其形成机制尚不清楚。电子显微镜和光漂白标记的命运显示，肌动蛋白丝在丝状伪足中发生逆行流动，并且片状伪足在结构和动力学上与片层内静止的GP束相连接。单个丝状伪足最初伸出，但随后与片状伪足的尖端分离，并在片层内引发新的GP束的形成。在同时表达绿色荧光蛋白 - 肌球蛋白II和红色荧光蛋白 - 肌动蛋白的单个活细胞中，肌球蛋白II斑点在丝状伪足引发新的GP束形成之前平均28秒定位到单个丝状伪足的基部。在新的GP束中，相关的肌球蛋白II相对于基质是静止的。在活细胞中抑制肌球蛋白II的运动活性会阻止片层中新的GP束的出现，但在相同的时间尺度内不会抑制细胞的突出。我们得出结论，前沿细胞边缘内的逆行F - 肌动蛋白流和肌球蛋白II活性将F - 肌动蛋白输送到片层，以引发新的GP束的形成。
In migrating fibroblasts actomyosin II bundles are graded polarity (GP) bundles, a distinct organization to stress fibers. GP bundles are important for powering cell migration, yet have an unknown mechanism of formation. Electron microscopy and the fate of photobleached marks show actin filaments undergoing retrograde flow in filopodia, and the lamellipodium are structurally and dynamically linked with stationary GP bundles within the lamella. An individual filopodium initially protrudes, but then becomes separated from the tip of the lamellipodium and seeds the formation of a new GP bundle within the lamella. In individual live cells expressing both GFP-myosin II and RFP-actin, myosin II puncta localize to the base of an individual filopodium an average 28 s before the filopodium seeds the formation of a new GP bundle. Associated myosin II is stationary with respect to the substratum in new GP bundles. Inhibition of myosin II motor activity in live cells blocks appearance of new GP bundles in the lamella, without inhibition of cell protrusion in the same timescale. We conclude retrograde F-actin flow and myosin II activity within the leading cell edge delivers F-actin to the lamella to seed the formation of new GP bundles.