Assembly of non-contractile dorsal stress fibers requires α-actinin-1 and Rac1 in migrating and spreading cells
Assembly of non-contractile dorsal stress fibers requires α-actinin-1 and Rac1 in migrating and spreading cells
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DOI：
10.1242/jcs.115063
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发表时间：
2013-01-01
影响因子：
4
通讯作者：
Vallenius, Tea
中科院分区：
文献类型：
--
作者：
Kovac, Bianca;Teo, Jessica L.;Vallenius, Tea
细胞迁移和扩散是由肌动蛋白聚合和肌动蛋白应力纤维驱动的。肌动蛋白应力纤维被认为含有 α-肌动蛋白交联剂和非肌肉肌球蛋白 II 马达。尽管在迁移和扩散细胞中已鉴定出几种肌动蛋白应力纤维亚型，但其组成的分子多样性程度和调节纤维亚型的信号通路在很大程度上仍然未知。在本研究中，我们确定背侧应力纤维组装需要 α-肌动蛋白-1。 α-肌动蛋白-1耗尽的细胞中背侧应力纤维的损失导致前缘粘着斑的成熟缺陷。这伴随着早期细胞扩散的延迟和细胞迁移的减慢，而肌球蛋白轻链磷酸化没有明显的改变。与未改变的肌球蛋白 II 活性一致，背侧应激纤维干缺乏肌球蛋白 II 并且对肌球蛋白 II ATP 酶抑制具有抵抗力。此外，Rac1 诱导背侧应力纤维组装，而收缩性腹侧应力纤维由 RhoA 诱导，这一发现支持了背侧应力纤维的非收缩性。通过消耗 α-肌动蛋白-1 或 Rac1 导致背侧应力纤维损失，导致 β-肌动蛋白在迁移和扩散细胞的前缘积聚。这些发现在分子上明确了来自其他肌动蛋白应力纤维亚型的背侧应力纤维。此外，我们提出非收缩性背侧应力纤维通过 Rac1 诱导的肌动蛋白聚合促进细胞迁移和早期细胞扩散。
Cell migration and spreading is driven by actin polymerization and actin stress fibers. Actin stress fibers are considered to contain alpha-actinin crosslinkers and nonmuscle myosin II motors. Although several actin stress fiber subtypes have been identified in migrating and spreading cells, the degree of molecular diversity of their composition and the signaling pathways regulating fiber subtypes remain largely uncharacterized. In the present study we identify that dorsal stress fiber assembly requires alpha-actinin-1. Loss of dorsal stress fibers in alpha-actinin-1-depleted cells results in defective maturation of leading edge focal adhesions. This is accompanied by a delay in early cell spreading and slower cell migration without noticeable alterations in myosin light chain phosphorylation. In agreement with the unaltered myosin II activity, dorsal stress fiber trunks lack myosin II and are resistant to myosin II ATPase inhibition. Furthermore, the non-contractility of dorsal stress fibers is supported by the finding that Rac1 induces dorsal stress fiber assembly whereas contractile ventral stress fibers are induced by RhoA. Loss of dorsal stress fibers either by depleting alpha-actinin-1 or Rac1 results in a beta-actin accumulation at the leading edge in migrating and spreading cells. These findings molecularly specify dorsal stress fibers from other actin stress fiber subtypes. Furthermore, we propose that non-contractile dorsal stress fibers promote cell migration and early cell spreading through Rac1-induced actin polymerization.