Suetsugu S, Miki H, Takenawa T
Department of Biochemistry, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
EMBO J. 1998 Nov 16;17(22):6516-26. doi: 10.1093/emboj/17.22.6516.
Profilin was first identified as an actin monomer binding protein; however, recent reports indicate its involvement in actin polymerization. To date, there is no direct evidence of a functional role in vivo for profilin in actin cytoskeletal reorganization. Here, we prepared a profilin mutant (H119E) defective in actin binding, but retaining the ability to bind to other proteins. This mutant profilin I suppresses actin polymerization in microspike formation induced by N-WASP, the essential factor in microspike formation. Profilin associates both in vivo and in vitro with N-WASP at proline-rich sites different from those to which Ash/Grb2 binds. This association between profilin and N-WASP is required for N-WASP-induced efficient microspike elongation. Moreover, we succeeded in reconstituting microspike formation in permeabilized cells using profilin I combined with N-WASP and its regulator, Cdc42. These findings provide the first evidence that profilin is a key molecule linking a signaling network to rapid actin polymerization in microspike formation.
最初，丝切蛋白被鉴定为一种肌动蛋白单体结合蛋白；然而，最近的报道表明它参与肌动蛋白聚合。迄今为止，尚无直接证据表明丝切蛋白在体内对肌动蛋白细胞骨架重组具有功能性作用。在此，我们制备了一种肌动蛋白结合缺陷但保留与其他蛋白结合能力的丝切蛋白突变体（H119E）。这种突变型丝切蛋白I抑制由N-WASP诱导的微刺形成过程中的肌动蛋白聚合，N-WASP是微刺形成的关键因子。丝切蛋白在体内和体外均与N-WASP在富含脯氨酸的位点结合，这些位点不同于Ash/Grb2结合的位点。丝切蛋白与N-WASP之间的这种结合是N-WASP诱导的高效微刺伸长所必需的。此外，我们成功地使用丝切蛋白I与N-WASP及其调节剂Cdc42在通透细胞中重建了微刺形成。这些发现提供了首个证据，即丝切蛋白是在微刺形成中将信号网络与快速肌动蛋白聚合联系起来的关键分子。
