Kiuchi Tai, Ohashi Kazumasa, Kurita Souichi, Mizuno Kensaku
Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, Japan.
J Cell Biol. 2007 May 7;177(3):465-76. doi: 10.1083/jcb.200610005. Epub 2007 Apr 30.
Cofilin stimulates actin filament disassembly and accelerates actin filament turnover. Cofilin is also involved in stimulus-induced actin filament assembly during lamellipodium formation. However, it is not clear whether this occurs by replenishing the actin monomer pool, through filament disassembly, or by creating free barbed ends, through its severing activity. Using photoactivatable Dronpa-actin, we show that cofilin is involved in producing more than half of all cytoplasmic actin monomers and that the rate of actin monomer incorporation into the tip of the lamellipodium is dependent on the size of this actin monomer pool. Finally, in cofilin-depleted cells, stimulus-induced actin monomer incorporation at the cell periphery is attenuated, but the incorporation of microinjected actin monomers is not. We propose that cofilin contributes to stimulus-induced actin filament assembly and lamellipodium extension by supplying an abundant pool of cytoplasmic actin monomers.
丝切蛋白刺激肌动蛋白丝的解聚并加速肌动蛋白丝的周转。丝切蛋白还参与片足形成过程中刺激诱导的肌动蛋白丝组装。然而，目前尚不清楚这是通过补充肌动蛋白单体库、通过丝解聚，还是通过其切断活性产生游离的带刺末端来实现的。使用光激活的Dronpa-肌动蛋白，我们发现丝切蛋白参与产生了超过一半的细胞质肌动蛋白单体，并且肌动蛋白单体掺入片足尖端的速率取决于这个肌动蛋白单体库的大小。最后，在丝切蛋白缺失的细胞中，刺激诱导的肌动蛋白单体在细胞周边的掺入减弱，但显微注射的肌动蛋白单体的掺入不受影响。我们提出，丝切蛋白通过提供丰富的细胞质肌动蛋白单体库，促进刺激诱导的肌动蛋白丝组装和片足延伸。
