Cdc42 and Rac1 Regulate the Interaction of IQGAP1 with β-Catenin

doi:10.1074/jbc.274.37.26044

Cdc42 and Rac1 Regulate the Interaction of IQGAP1 with β-Catenin*

From the^‡Division of Signal Transduction, Nara Institute of Science and Technology, Ikoma 630-0101,^§Department of Biochemistry, Hiroshima University School of Medicine, Hiroshima 734-8551, ^¶Inheritance and Variation Group, PRESTO, Japan Science and Technology, Kyoto 619-0237,^‖Department of Virology II, National Institute of Infectious Diseases, Tokyo 162-8640, ^‡Institute for Virus Research, Kyoto University, Kyoto 606-8397, and ^§§Group of Developmental Neurobiology, Division of Biological Science, Nagoya University Graduate School of Science, Nagoya 464-8602, Japan

Abstract

IQGAP1, a target of Cdc42 and Rac1 small GTPases, directly interacts with β-catenin and negatively regulates E-cadherin-mediated cell-cell adhesion by dissociating α-catenin from the cadherin-catenin complex in vivo (Kuroda, S., Fukata, M., Nakagawa, M., Fujii, K., Nakamura, T., Ookubo, T., Izawa, I., Nagase, T., Nomura, N., Tani, H., Shoji, I., Matsuura, Y., Yonehara, S., and Kaibuchi, K. (1998) Science 281, 832–835). Here we investigated how Cdc42 and Rac1 regulate the IQGAP1 function. IQGAP1 interacted with the amino-terminal region (amino acids 1–183) of β-catenin, which contains the α-catenin-binding domain. IQGAP1 dissociated α-catenin from the β-catenin-α-catenin complex in a dose-dependent manner in vitro. Guanosine 5′-(3-O-thio)triphosphate (GTPγS)·glutathioneS-transferase (GST)-Cdc42 and GTPγS·GST-Rac1 inhibited the binding of IQGAP1 to β-catenin in a dose-dependent manner in vitro, whereas neither GDP·GST-Cdc42, GDP·GST-Rac1, nor GTPγS·GST-RhoA did. The coexpression of dominant active Cdc42 with IQGAP1 suppressed the dissociation of α-catenin from the cadherin-catenin complex induced by the overexpression of IQGAP1 in L cells expressing E-cadherin (EL cells). Consistent with this, the overexpression of either dominant negative Cdc42 or Rac1 resulted in the reduction of E-cadherin-mediated cell adhesive activity in EL cells. These results indicate that Cdc42 and Rac1 negatively regulate the IQGAP1 function by inhibiting the interaction of IQGAP1 with β-catenin, leading to stabilization of the cadherin-catenin complex.

Footnotes

↵* This study was supported by grants-in-aid for Scientific Research from the Ministry of Education, Science, and Culture, Japan (1998), by the Japan Society of the Promotion of Science Research for the Future, by the Human Frontier Science Program, and by the grant from Kirin Brewery Co. Ltd.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.
↵** Present address: Dept. of Pathology, Harvard Medical School, Boston, MA 02115.
↵¶¶ To whom correspondence should be addressed: Division of Signal Transduction, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma 630-0101, Japan. Tel.: 81-743-72-5440; Fax: 81-743-72-5449; E-mail: kaibuchi@bs.aist-nara.ac.jp.
Abbreviations:

WASP

Wiskott-Aldrich syndrome protein

N-WASP

Neural Wiskott-Aldrich syndrome protein

MRCK

Myotonic dystrophy kinase-related Cdc42-binding kinase

GTPγS

guanosine 5′-(3-O-thio)triphosphate

GST

glutathione S-transferase

MBP

maltose-binding protein

aa

amino acid

PAGE

polyacrylamide gel electrophoresis

HA

hemagglutinin

DSP

dithiobis(succinimidyl propionate)

CHAPS

(3-[(3-cholamidopropyl)dimethylammonio]propanesulfonic acid)

IL

interleukin

MDCK

Madin-Darby canine kidney

GDI

GDP dissociation inhibitor
- Received March 2, 1999.
- Revision received May 25, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.