Kato M, Miki H, Imai K, Nonoyama S, Suzuki T, Sasakawa C, Takenawa T
Department of Biochemistry, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Chiba 263-8522, Japan.
J Biol Chem. 1999 Sep 17;274(38):27225-30. doi: 10.1074/jbc.274.38.27225.
WASP (Wiskott-Aldrich syndrome protein) was identified as the gene product whose mutation causes the human hereditary disease Wiskott-Aldrich syndrome. WASP contains many functional domains and has been shown to induce the formation of clusters of actin filaments in a manner dependent on Cdc42. However, there has been no report investigating what domain(s) is(are) important for the function. Here we present for the first time the results of detailed analyses on the domain-function relationship of WASP. First, the C-terminal verprolin-cofilin-acidic domain was shown to be essential for the regulation of actin cytoskeleton. In addition, we found that the clustering of WASP itself is distinct from actin clustering. The partial protein containing the region from the N-terminal pleckstrin homology domain to the basic residue-rich region also clustered especially around the nucleus as wild type WASP without inducing actin clustering. Finally, we obtained the quite unexpected result that a WASP mutant deficient in binding to Cdc42 still induced actin cluster formation, indicating that direct interaction between Cdc42 and WASP is not required for the regulation of actin cytoskeleton. This result may explain why no Wiskott-Aldrich syndrome patients have been identified with a missense mutation in the Cdc42-binding site.
WASP（威斯科特-奥尔德里奇综合征蛋白）被鉴定为其突变导致人类遗传性疾病威斯科特-奥尔德里奇综合征的基因产物。WASP包含许多功能域，并且已被证明以依赖于Cdc42的方式诱导肌动蛋白丝簇的形成。然而，尚无报告研究哪个结构域对该功能很重要。在此，我们首次展示了对WASP结构域-功能关系的详细分析结果。首先，C端的维普洛林-丝切蛋白-酸性结构域被证明对肌动蛋白细胞骨架的调节至关重要。此外，我们发现WASP自身的聚集与肌动蛋白聚集不同。包含从N端普列克底物蛋白同源结构域到富含碱性残基区域的部分蛋白也会聚集，特别是在细胞核周围，就像野生型WASP一样，但不会诱导肌动蛋白聚集。最后，我们得到了一个相当意外的结果，即一个缺乏与Cdc42结合能力的WASP突变体仍然能诱导肌动蛋白簇的形成，这表明Cdc42与WASP之间的直接相互作用对于肌动蛋白细胞骨架的调节不是必需的。这一结果可能解释了为什么尚未鉴定出在Cdc42结合位点发生错义突变的威斯科特-奥尔德里奇综合征患者。
