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© The Rockefeller University Press, 0021-9525/2000//253 $5.00
The Journal of Cell Biology, Volume 148, Number 2, , 2000 253-258


Brief Report

Rhoa Function in Lamellae Formation and Migration Is Regulated by the {alpha}6β4 Integrin and Camp Metabolism



Kathleen L. O'Connora, Bao-Kim Nguyena, and Arthur M. Mercurioa

a Division of Cancer Biology and Angiogenesis, Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215
Beth Israel Deaconess Medical Center, Department of Pathology, Research North, 330 Brookline Avenue, Boston, MA 02215.(617) 975-5531(617) 667-7714

amercuri{at}caregroup.harvard.edu

Clone A colon carcinoma cells develop fan-shaped lamellae and exhibit random migration when plated on laminin, processes that depend on the ligation of the {alpha}6β4 integrin. Here, we report that expression of a dominant negative RhoA (N19RhoA) in clone A cells inhibited {alpha}6β4-dependent membrane ruffling, lamellae formation, and migration. In contrast, expression of a dominant negative Rac (N17Rac1) had no effect on these processes. Using the Rhotekin binding assay to assess RhoA activation, we observed that engagement of {alpha}6β4 by either antibody-mediated clustering or laminin attachment resulted in a two- to threefold increase in RhoA activation, compared with cells maintained in suspension or plated on collagen. Antibody-mediated clustering of β1 integrins, however, actually suppressed Rho A activation. The {alpha}6β4-mediated interaction of clone A cells with laminin promoted the translocation of RhoA from the cytosol to membrane ruffles at the edges of lamellae and promoted its colocalization with β1 integrins, as assessed by immunofluorescence microscopy. In addition, RhoA translocation was blocked by inhibiting phosphodiesterase activity and enhanced by inhibiting the activity of cAMP-dependent protein kinase. Together, these results establish a specific integrin-mediated pathway of RhoA activation that is regulated by cAMP and that functions in lamellae formation and migration.

Key Words: carcinoma • protein kinase A • G-protein • phosphodiesterase • cytoskeleton



© 2000 The Rockefeller University Press

Abbreviations used in this paper: β-gal, β-galactosidase; GFP, green fluorescent protein; IBMX, isobutylmethylxanthine; LPA, lysophosphatidic acid; PDE, phosphodiesterase; PKA, cAMP-dependent protein kinase; RBD, Rho-binding domain of Rhotekin.



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