Uncoupling of Membrane Ruffling and Pinocytosis during Ras Signal Transduction*
- Guangpu Li‡,
- Crislyn D’Souza-Schorey§,
- M. Alejandro Barbieri,
- Jonathan A. Cooper¶ and
- Philip D. Stahl‖
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110 and the¶Fred Hutchinson Cancer Research Center, Seattle, Washington 98104
Abstract
Activation of Ras stimulates cell surface membrane ruffling and pinocytosis. Although seen as coupled events, our study demonstrates that membrane ruffling and pinocytosis are regulated by distinct Ras signal transduction pathways. Ras controls membrane ruffling via the small GTPase Rac. In BHK-21 cells, expression of the constitutively active Rac1(G12V) mutant, via a Sindbis virus vector, resulted in a dramatic stimulation of membrane ruffling without affecting the uptake of horseradish peroxidase. Expression of Ha-Ras(G12V), an activated Ras mutant, stimulated both membrane ruffling and horseradish peroxidase uptake. The Ha-Ras(G12V)-stimulated pinocytosis but not membrane ruffling was abolished by either wortmannin or co-expression with a dominant negative mutant of Rab5, Rab5(S34N). Expression of the activated Rab5(Q79L) mutant mimics the stimulatory effect of Ha-Ras(G12V) on pinocytosis but not membrane ruffling. Our data indicate that Ha-Ras(G12V) separately activates Rab5-dependent pinocytosis and Rac1-dependent membrane ruffling.
Footnotes
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↵* This work was supported in part by grants from the National Institutes of Health (to P. D. S. and J. A. C.).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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↵‡ Supported by a fellowship from the Parker B. Francis Foundation. To whom correspondence should be addressed: Dept. of Biochemistry and Molecular Biology, The University of Oklahoma Health Sciences Center, 940 S. L. Young Blvd., P. O. Box 26901, Oklahoma City, OK 73190. Tel.: 405-271-2227; Fax: 405-271-3092; E-mail: guangpu-li{at}vokhsc.edu.
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↵§ Lucille P. Markey Special Emphasis Pathway Fellow.
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↵‖ Present address: Dept. of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid, St. Louis, MO 63110. Tel.: 314-362-6950; Fax: 314-362-7463.
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↵1 The abbreviations used are: PI 3-kinase, phosphatidylinositol 3-kinase; α-MEM, α-minimum essential medium; HRP, horseradish peroxidase; PBS, phosphate-buffered saline.
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- Received February 6, 1997.
