Actin turnover-dependent fast dissociation of capping protein in the dendritic nucleation actin network: evidence of frequent filament severing
Actin turnover-dependent fast dissociation of capping protein in the dendritic nucleation actin network: evidence of frequent filament severing
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DOI：
10.1083/jcb.200604176
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发表时间：
2006-12-18
影响因子：
7.8
通讯作者：
Watanabe, Naoki
中科院分区：
文献类型：
--
作者：
Miyoshi, Takushi;Tsuji, Takahiro;Watanabe, Naoki
肌动蛋白形成树枝状成核网络，并在片状伪足中经历快速的聚合-解聚循环。为了阐明肌动蛋白分解的机制，我们表征了主要的分子动力学。利用单分子斑点显微镜观察了末端结合蛋白Arp 2/3复合物和帽蛋白（CP）。我们已经确定Arp 2/3和CP的解离速率分别为0.048和0.58 s（-1），在活XTC成纤维细胞的板状伪足。这种CP解离速率比体外快三个数量级。CP从肌动蛋白应力纤维中解离的速度比从片状伪足肌动蛋白网络中解离的速度慢，这表明CP解离与肌动蛋白相关。悲叹动力学我们发现一种肌动蛋白解聚抑制剂，jasplakinastine，可以迅速阻断细胞中CP的快速解离。因此，LIM激酶的共表达延长了板状伪足中CP斑点的寿命。这些结果表明，cofilin介导的肌动蛋白解体触发CP从肌动蛋白解离。哀叹。我们预测到了。在树突状成核肌动蛋白阵列中，末端切断和末端对末端退火可能相当频繁地发生。
Actin forms the dendritic nucleation network and undergoes rapid polymerization-depolymerization cycles in lamellipodia. To elucidate the mechanism of actin disassembly, we characterized molecular kinetics of the major. lament end-binding proteins Arp2/3 complex and capping protein (CP) using single-molecule speckle microscopy. We have determined the dissociation rates of Arp2/3 and CP as 0.048 and 0.58 s(-1), respectively, in lamellipodia of live XTC fibroblasts. This CP dissociation rate is three orders of magnitude faster than in vitro. CP dissociates slower from actin stress fibers than from the lamellipodial actin network, suggesting that CP dissociation correlates with actin. lament dynamics. We found that jasplakinolide, an actin depolymerization inhibitor, rapidly blocked the fast CP dissociation in cells. Consistently, the coexpression of LIM kinase prolonged CP speckle lifetime in lamellipodia. These results suggest that cofilin-mediated actin disassembly triggers CP dissociation from actin. laments. We predict that. lament severing and end-to-end annealing might take place fairly frequently in the dendritic nucleation actin arrays.