Differential Translocation of Rho Family GTPases by Lysophosphatidic Acid, Endothelin-1, and Platelet-derived Growth Factor*
- From the Howard Hughes Medical Institute and the Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0295
- ‡Investigator of the Howard Hughes Medical Institute. To whom all correspondence should be addressed. Tel.: 615-322-6494. Fax: 615-322-4381.
Abstract
The small GTPases of the Rho family play a key role in a number of signaling pathways activated by lysophosphatidic acid (LPA). However, little is known concerning the mechanism of regulation of these proteins. In this study we demonstrate that in Swiss 3T3 fibroblasts, LPA induces a sustained, time-dependent relocalization of RhoA to the Triton X-100-soluble low speed membrane fraction, which can be reversed by removal of LPA from the medium. Translocation was only observed with micromolar concentrations of LPA and was inhibited by pretreating the cells with pertussis toxin but not with tyrosine kinase inhibitors. LPA also induced translocation of CDC42Hs to the membranes but had no effect on the distribution of Rac1, RhoB, or Rho-GDI. Translocation of RhoA was also induced by endothelin-1. Conversely, platelet-derived growth factor did not cause the translocation of RhoA to any membrane fraction but stimulated relocalization of Rac1 to the high speed membrane fraction. Significantly, incubation of cell lysates with guanosine 5′-O-(thiotriphosphate) was sufficient to translocate RhoA, Rac1, and CDC42Hs from the cytosol to the membranes, whereas incubation with GDP had the opposite effect. These data suggest that the translocation of the Rho family proteins to the membrane fraction is controlled by their activation state and that agonists show selectivity in inducing the activation/translocation of these proteins.
Footnotes
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↵* 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.
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↵1 The abbreviations used are:
- Rho-GDI
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Rho GDP dissociation inhibitor
- DMEM
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Dulbecco's modified Eagle's medium
- GTPγS
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guanosine 5′-O-(thiotriphosphate)
- LPA
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lysophosphatidic acid
- PDGF
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platelet-derived growth factor
- ATPγS
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adenosine 5′-O-(thiotriphosphate)
- AMP-PNP
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adenylyl imidodiphosphate.
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- Received July 25, 1996.
- Revision received October 4, 1996.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
