Miki H, Yamaguchi H, Suetsugu S, Takenawa T
Department of Biochemistry, Institute of Medical Science, University of Tokyo, and CREST, Japan Science and Technology Corporation.
Nature. 2000 Dec 7;408(6813):732-5. doi: 10.1038/35047107.
Neural Wiskott-Aldrich syndrome protein (N-WASP) functions in several intracellular events including filopodium formation, vesicle transport and movement of Shigella frexneri and vaccinia virus, by stimulating rapid actin polymerization through the Arp2/3 complex. N-WASP is regulated by the direct binding of Cdc42 (refs 7, 8), which exposes the domain in N-WASP that activates the Arp2/3 complex. A WASP-related protein, WAVE/Scar, functions in Rac-induced membrane ruffling; however, Rac does not bind directly to WAVE, raising the question of how WAVE is regulated by Rac. Here we demonstrate that IRSp53, a substrate for insulin receptor with unknown function, is the 'missing link' between Rac and WAVE. Activated Rac binds to the amino terminus of IRSp53, and carboxy-terminal Src-homology-3 domain of IRSp53 binds to WAVE to form a trimolecular complex. From studies of ectopic expression, we found that IRSp53 is essential for Rac to induce membrane ruffling, probably because it recruits WAVE, which stimulates actin polymerization mediated by the Arp2/3 complex.
神经维斯科特-奥尔德里奇综合征蛋白（N-WASP）在多种细胞内活动中发挥作用，包括丝状伪足形成、囊泡运输以及弗氏志贺菌和痘苗病毒的移动，它通过Arp2/3复合体刺激肌动蛋白快速聚合来实现这些功能。N-WASP受Cdc42的直接结合调控（参考文献7、8），这会暴露N-WASP中激活Arp2/3复合体的结构域。一种与WASP相关的蛋白WAVE/Scar，在Rac诱导的膜皱襞形成中发挥作用；然而，Rac并不直接与WAVE结合，这就引发了WAVE如何受Rac调控的问题。在此我们证明，胰岛素受体的一种功能未知的底物IRSp53是Rac和WAVE之间的“缺失环节”。激活的Rac与IRSp53的氨基末端结合，而IRSp53的羧基末端Src同源3结构域与WAVE结合形成一个三分子复合体。通过异位表达研究，我们发现IRSp53对于Rac诱导膜皱襞形成至关重要，这可能是因为它招募了WAVE，而WAVE会刺激由Arp2/3复合体介导的肌动蛋白聚合。
