Wiskott-Aldrich Syndrome Protein Induces Actin Clustering without Direct Binding to Cdc42

doi:10.1074/jbc.274.38.27225

Wiskott-Aldrich Syndrome Protein Induces Actin Clustering without Direct Binding to Cdc42*

From the Departments of ^‡Biochemistry and ^‖Bacteriology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, the ^¶Department of Pediatrics, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, and the ^§Department of Biology, Faculty of Science, Chiba University, Yayoicho, Inage-ku, Chiba, Chiba 263-8522, Japan

Abstract

WASP (Wiskott-Aldrichsyndrome 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.

Footnotes

↵* This work was supported in part by a Grant-in-Aid for Cancer Research from the Ministry of Education, Science, and Culture of Japan and a Grant-in-Aid for Research for the Future Program from the Japan Society for the Promotion of Science.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵** To whom correspondence should be addressed. Tel.: 81-3-5449-5510; Fax: 81-3-5449-5417; E-mail: takenawa@ims.u-tokyo.ac.jp.
Abbreviations:

PH

pleckstrin homology

CRIB

Cdc42 and Rac interactive binding

GBD

GTPase binding domain

GST

glutathione S-transferase

PR

proline-rich

VCA

verprolin-cofilin-acidic

WT

wild type

GTPγS

guanosine 5′-3-O-(thio)triphosphate

WI

WASP insert

BR

basic-rich region

VPH

verprolin homology
- Received March 15, 1999.
- Revision received June 24, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.