Rho Family GTPases Bind to Phosphoinositide Kinases

doi:10.1074/jbc.270.30.17656

Rho Family GTPases Bind to Phosphoinositide Kinases (*)

From the (1) Departments of Cell Biology and
(2) Medicine, Harvard Medical School and the
(3) Division of Signal Transduction, Beth Israel Hospital, Boston, Massachusetts 02115

^§ To whom correspondence should be addressed: Warren Alpert Bldg., Rm. 151, 200 Longwood Ave., Boston, MA 02115. Tel.: 617-278-3048; Fax: 617-278-3131.

Abstract

Rho family GTPases appear to play an important role in the regulation of the actin cytoskeleton, but the mechanism of regulation is unknown. Since phosphoinositide 3-kinase and phosphatidylinositol 4,5-bisphosphate have also been implicated in actin reorganization, we investigated the possibility that Rho family members interact with phosphoinositide kinases. We found that both GTP- and GDP-bound Rac1 associate with phosphatidylinositol-4-phosphate 5-kinase in vitro and in vivo. Phosphoinositide 3-kinase also bound to Rac1 and Cdc42Hs, and these interactions were GTP-dependent. Stimulation of Swiss 3T3 cells with platelet-derived growth factor induced the association of PI 3-kinase with Rac in immunoprecipitates. PI 3-kinase activity was also detected in Cdc42 immunoprecipitates from COS7 cells. These results suggest that phosphoinositide kinases are involved in Rho family signal transduction pathways and raise the possibility that the effects of Rho family members on the actin cytoskeleton are mediated in part by phosphoinositide kinases.

Footnotes

↵* This work was supported by a Parke-Davis American Heart Association Clinician Scientist Award, an award from the Hood Foundation (to C. L. C.), and National Institutes of Health Grant GM36624 (to L. C. C.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

PDGF

platelet-derived growth factor

PI

phosphoinositide

PtdIns

phosphatidylinositol

GTPS

guanosine 5′-3-O-(thio)triphosphate

GST

glutathione S-transferase

DTT

dithiothreitol

GDPβS

guanyl-5′-yl thiophosphate

PBS

phosphate-buffered saline

HPLC

high pressure liquid chromatography.
↵²L. Ma, M. Kirschner, K. F. Tolias, L. C. Cantley, and C. L. Carpenter, unpublished data; A. Hall, personal communication.
- Received April 7, 1995.
- Revision received June 6, 1995.