Marshall Thomas W, Aloor Heather L, Bear James E
Lineberger Comprehensive Cancer Center and Department of Cell and Developmental Biology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA.
J Cell Sci. 2009 Sep 1;122(Pt 17):3061-9. doi: 10.1242/jcs.051482. Epub 2009 Aug 4.
Coronins are conserved F-actin-binding proteins that are important for motility and actin dynamics. Unlike type I coronins, coronin 2A localizes to stress fibers and some focal adhesions, and is excluded from the leading edge. Depletion of coronin 2A in MTLn3 cells decreases cell motility and turnover of focal adhesions. Surprisingly, none of the pathways known to regulate focal-adhesion turnover are affected by depletion of coronin 2A. Depletion of coronin 2A does, however, increase phospho-cofilin, suggesting that misregulation of cofilin might affect adhesion dynamics. Slingshot-1L, a cofilin-activating phosphatase, localizes to focal adhesions and interacts with coronin 2A. Depletion of coronin 2A reduces cofilin activity at focal adhesions, as measured by barbed-end density and actin FRAP. In both fixed cells and live cells, cofilin localizes to the proximal end of some focal adhesions. Although expression of wild-type cofilin in coronin-2A-depleted cells has no major effect on focal-adhesion dynamics, expression of an active mutant of cofilin bypasses the defects in cell motility and focal-adhesion disassembly. These results implicate both coronin 2A and cofilin as factors that can regulate a subset of focal-adhesion-turnover events.
冠蛋白是保守的F-肌动蛋白结合蛋白,对细胞运动和肌动蛋白动力学很重要。与I型冠蛋白不同,冠蛋白2A定位于应力纤维和一些粘着斑,且被排除在前缘之外。MTLn3细胞中冠蛋白2A的缺失会降低细胞运动性和粘着斑的更新。令人惊讶的是,已知的调节粘着斑更新的途径均不受冠蛋白2A缺失的影响。然而,冠蛋白2A的缺失确实会增加磷酸化丝切蛋白,这表明丝切蛋白的调节异常可能会影响粘着动力学。丝切蛋白激活磷酸酶弹弓-1L定位于粘着斑并与冠蛋白2A相互作用。通过肌动蛋白丝末端密度和肌动蛋白荧光恢复率分析,冠蛋白2A的缺失会降低粘着斑处丝切蛋白的活性。在固定细胞和活细胞中,丝切蛋白均定位于一些粘着斑的近端。尽管在冠蛋白2A缺失的细胞中野生型丝切蛋白的表达对粘着斑动力学没有重大影响,但丝切蛋白活性突变体的表达可绕过细胞运动性和粘着斑解聚方面的缺陷。这些结果表明冠蛋白2A和丝切蛋白都是可以调节一部分粘着斑更新事件的因子。