The Microtubule-destabilizing Activity of Metablastin (p19) Is Controlled by Phosphorylation*
- Susan Band Horwitz‡,
- Heng-Jia Shen‡,
- Lifeng He‡,
- Peter Dittmar§,
- Rüdiger Neef§,
- Jinghua Chen§ and
- Ulrich K. Schubartद
- From the Department of ‡ Molecular Pharmacology and
- § Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
- ¶ To whom correspondence should be addressed: Dept. of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461. Tel.: 718-430-3249; Fax: 718-430-8557; E-mail: schubart{at}aecom.yu.edu
Abstract
Metablastin (also called p19, stathmin, prosolin, p18, Lap18, and oncoprotein 18) is a highly conserved, cytosolic 149-amino acid polypeptide that is expressed in immature vertebrate cells and undergoes extracellular factor- and cell cycle-regulated serine phosphorylation. The protein was shown recently to destabilize microtubules in vitro (Belmont, L., and Mitchison, T. J. (1996) Cell 84, 623–631). Here we demonstrate that microinjection of recombinant metablastin induces a loss of microtubules in COS-7 cells. This effect is enhanced by serine-to-alanine mutations at several phosphorylation sites and virtually abolished by aspartate substitution at a single site, Ser-63. We also show that stoichiometric amounts of metablastin prevent assembly and promote disassembly of microtubules in vitro. Interestingly, the phosphorylation site mutations of metablastin that have dramatic differential effects in intact cells do not alter the ability of metablastin to block tubulin assembly in vitro. The data suggest that phosphorylation of metablastin controls its microtubule-destabilizing activity in vivo but that this regulation may require additional cellular factors. This control mechanism is poised to play a critical role in the dynamic reorganization of the cellular microtubule network that occurs during morphogenesis and mitosis.
Footnotes
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↵* This work was supported by United States Public Health Service Grants CA39821 (to S. B. H.), NS26333 (to U. K. S.), and 5P30CA13330. 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:
- GST
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glutathioneS-transferase
- MES
-
2-(N-morpholino)ethanesulfonic acid
- PBS
-
phosphate-buffered saline.
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- Received December 20, 1996.
- Revision received February 10, 1997.
- © 1997 by The American Society for Biochemistry and Molecular Biology, Inc.
