Rodal A A, Tetreault J W, Lappalainen P, Drubin D G, Amberg D C
Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA.
J Cell Biol. 1999 Jun 14;145(6):1251-64. doi: 10.1083/jcb.145.6.1251.
Actin interacting protein 1 (Aip1) is a conserved component of the actin cytoskeleton first identified in a two-hybrid screen against yeast actin. Here, we report that Aip1p also interacts with the ubiquitous actin depolymerizing factor cofilin. A two-hybrid-based approach using cofilin and actin mutants identified residues necessary for the interaction of actin, cofilin, and Aip1p in an apparent ternary complex. Deletion of the AIP1 gene is lethal in combination with cofilin mutants or act1-159, an actin mutation that slows the rate of actin filament disassembly in vivo. Aip1p localizes to cortical actin patches in yeast cells, and this localization is disrupted by specific actin and cofilin mutations. Further, Aip1p is required to restrict cofilin localization to cortical patches. Finally, biochemical analyses show that Aip1p causes net depolymerization of actin filaments only in the presence of cofilin and that cofilin enhances binding of Aip1p to actin filaments. We conclude that Aip1p is a cofilin-associated protein that enhances the filament disassembly activity of cofilin and restricts cofilin localization to cortical actin patches.
肌动蛋白相互作用蛋白1（Aip1）是肌动蛋白细胞骨架的一个保守组分，最初是在针对酵母肌动蛋白的双杂交筛选中被鉴定出来的。在此，我们报道Aip1p还与普遍存在的肌动蛋白解聚因子cofilin相互作用。一种基于双杂交的方法，利用cofilin和肌动蛋白突变体，在一个明显的三元复合物中鉴定出了肌动蛋白、cofilin和Aip1p相互作用所必需的残基。AIP1基因的缺失与cofilin突变体或act1-159（一种在体内减缓肌动蛋白丝解聚速率的肌动蛋白突变）相结合是致死的。Aip1p定位于酵母细胞中的皮质肌动蛋白斑块，并且这种定位会被特定的肌动蛋白和cofilin突变所破坏。此外，需要Aip1p将cofilin的定位限制在皮质斑块。最后，生化分析表明，Aip1p仅在存在cofilin的情况下才会导致肌动蛋白丝的净解聚，并且cofilin会增强Aip1p与肌动蛋白丝的结合。我们得出结论，Aip1p是一种与cofilin相关的蛋白，它增强了cofilin的丝解聚活性，并将cofilin的定位限制在皮质肌动蛋白斑块。
