E-cadherin-mediated Cell-Cell Attachment Activates Cdc42

doi:10.1074/jbc.M003430200

E-cadherin-mediated Cell-Cell Attachment Activates Cdc42*

From the Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115

Abstract

E-cadherin is a transmembrane protein that mediates Ca²⁺-dependent cell-cell adhesion. Cdc42, a member of the Rho family of small GTPases, participates in cytoskeletal rearrangement and cell cycle progression. Recent evidence reveals that members of the Rho family modulate E-cadherin function. To further examine the role of Cdc42 in E-cadherin-mediated cell-cell adhesion, we developed an assay for active Cdc42 using the GTPase-binding domain of the Wiskott-Aldrich syndrome protein. Initiation of E-cadherin-mediated cell-cell attachment significantly increased in a time-dependent manner the amount of active Cdc42 in MCF-7 epithelial cell lysates. By contrast, Cdc42 activity was not increased under identical conditions in MCF-7 cells incubated with anti-E-cadherin antibodies nor in MDA-MB-231 (E-cadherin negative) epithelial cells. By fusing the Wiskott-Aldrich syndrome protein/GTPase-binding domain to a green fluorescent protein, activation of endogenous Cdc42 by E-cadherin was demonstrated in live cells. These data indicate that E-cadherin activates Cdc42, demonstrating bi-directional interactions between the Rho- and E-cadherin signaling pathways.

Footnotes

↵* This work was supported in part by National Institutes of Health Grant CA75205.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: Brigham and Women's Hospital, Thorn 530, 75 Francis St., Boston, MA 02115. Tel.: 617-732-6627; Fax: 617-278-6921; E-mail: dsacks@rics.bwh.harvard.edu.
Published, JBC Papers in Press, August 18, 2000, DOI 10.1074/jbc.M003430200
Abbreviations:

GEF

guanine nucleotide exchange factor

PAGE

polyacrylamide gel electrophoresis

PVDF

polyvinylidene difluoride

GBD

GTPase-binding domain

GAP

GTPase-activating protein

GST

gluthathione S-transferase

MBP

maltose-binding protein

GTPγS

guanosine 5′-O-(3-thiotriphosphate)

PBS

phosphate-buffered saline

GFP

green fluorescent protein

DMEM

Dulbecco's modified Eagle's medium

MDCK

Madin-Darby canine kidney

PI3-kinase

phosphatidylinositol 3′-kinase

WASP

Wiskott-Aldrich syndrome protein
- Received April 21, 2000.
- Revision received August 11, 2000.
The American Society for Biochemistry and Molecular Biology, Inc.