MSS4, a Phosphatidylinositol-4-phosphate 5-Kinase Required for Organization of the Actin Cytoskeleton in Saccharomyces cerevisiae*
- From the ‡Department of Biochemistry, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland and the ¶Imperial Cancer Research Fund Laboratories, P.O. Box 123, Lincoln’s Fields, London WC2A 3PX, United Kingdom
Abstract
The Saccharomyces cerevisiae protein MSS4 is essential and homologous to mammalian phosphatidylinositol-4-phosphate (PI(4)P) 5-kinases. Here, we demonstrate that MSS4 is a lipid kinase. MSS4 has dual substrate specificity in vitro, converting PI(4)P to PI(4,5)P2 and to a lesser extent PI(3)P to PI(3,4)P2; no activity was detected with PI or PI(5)P as a substrate. Cells overexpressing MSS4 contain an elevated level specifically of PI(4,5)P2, whereas mss4mutant cells have only approximately 10% of the normal amount of this phosphorylated phosphoinositide. Furthermore, cells lacking MSS4 are unable to form actin cables and to properly localize their actin cytoskeleton during polarized cell growth. Overexpression ofRHO2, encoding a Rho-type GTPase involved in regulation of the actin cytoskeleton, restores growth and polarized distribution of actin in an mss4 mutant. These results suggest that MSS4 is the major PI(4)P 5-kinase in yeast and provide a link between phosphoinositide metabolism and organization of the actin cytoskeletonin vivo.
Footnotes
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↵* This work was supported by grants from the Imperial Cancer Research Fund (to P. J. P. and F. T. C.) and from the Swiss National Science Foundation and the Canton of Basel (to M. N. H.).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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↵§ Recipient of a long-term European Molecular Biology Organization fellowship.
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↵‖ To whom correspondence should be addressed. Tel.: 41-61-267-2162; Fax: 41-61-267-2149; E-mail:hall{at}ubaclu.unibas.ch.
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↵1 The abbreviations used are: PI, phosphatidylinositol; PI(4,5)P2, phosphatidylinositol 4,5-biphosphate; PI(3,5)P2, phosphatidylinositol 3,5-biphosphate; IP3, inositol 1,4,5-triphosphate; kb, kilobase(s); GST, glutathione S-transferase; HPLC, high performance liquid chromatography; GroPIns(3,5)P2, deacylated PI(3,5)P2.
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- Received November 3, 1997.
- Revision received February 11, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
