EFFECT ON MICROTUBULE DYNAMICS OF XMAP230, A MICROTUBULE-ASSOCIATED PROTEIN PRESENT IN XENOPUS-LAEVIS EGGS AND DIVIDING CELLS

被引:81
作者
ANDERSEN, SSL
BUENDIA, B
DOMINGUEZ, JE
SAWYER, A
KARSENTI, E
机构
[1] Europ. Molecular Biology Laboratory, Cell Biology Program
[2] Dept. de Biol. Supra-Molec. et Cell., Institut J. Monod, UAR 9922
[3] EMBL, D-69012, Heidelberg
关键词
D O I
10.1083/jcb.127.5.1289
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
The reorganization from a radical interphase microtubule (MT) network into a bipolar spindle at the onset of mitosis involves a dramatic change in MT dynamics. Microtubule-associated proteins (MAPs) and other factors are thought to regulate MT dynamics both in interphase and in mitosis. In this study we report the purification and functional in vitro characterization of a 230-KD MAP from Xenopus egg extract (XMAP230). This protein is present in eggs, oocytes, testis and a Xenopus tissue culture cell line. It is apparently absent from non-dividing cells in which an immunologically related 200-kD protein is found. XMAP230 is composed of two isoforms with slightly different molecular masses and pIs. It is localized to interphase MTs, dissociates from MTs at the onset of prophase and specifically binds to spindle MTs during metaphase and anaphase. The dissociation constant of XMAP230 is 500 nM, the stoichiometry of binding to MTs is between 1:8 and 1:4, and the in vivo concentration is similar to 200 nM. Both isoforms are phosphorylated and have reduced affinity for microtubules in mitotic extracts. Analysis of the effect of XMAP230 on MT dynamics by video microscopy shows that it increases the growth rate, decreases the shrinking rate of MTs and strongly suppresses catastrophes. These results suggest that in vivo, XMAP230 participates in the control of the MT elongation rate, stabilizes MTs and locally modulates MT dynamics during mitosis.
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页码:1289 / 1299
页数:11
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