Cdc2 kinase-induced destabilization of MAP2-coated microtubules in Xenopus egg extracts

• Published in: Journal of cell science Vol. 101; no. 1; pp. 69 - 78
• Main Authors: FARUKI, S, DOREE, M, KARSENTI, E
• Format: Journal Article
• Language: English
• Published: Cambridge Company of Biologists 1992
• Subjects: Animals; Biological and medical sciences; CDC2 Protein Kinase - pharmacology; Cell structures and functions; Cell-Free System; Cytoskeleton, cytoplasm. Intracellular movements; Fundamental and applied biological sciences. Psychology; Interphase; Microtubule-Associated Proteins - antagonists & inhibitors; Microtubules - drug effects; Mitosis; Molecular and cellular biology; Nocodazole - pharmacology; Ovum; Phosphorylation; Xenopus; Phosphorylation; Bovine; Enzyme; Mitosis; Stabilization; Xenopus laevis; Amphibia; Salientia; Vertebrata; Mammalia; Molecular assembly; Protein kinase; Cytoskeleton; Microtubule associated protein; Artiodactyla; Microtubule; Ungulata; Brain (vertebrata)
• ISSN: 0021-9533; 1477-9137
• DOI: 10.1242/jcs.101.1.69

During the interphase to metaphase transition, microtubules are destabilized by a cdc2 kinase-dependent phosphorylation event. This destabilization is due to a dramatic increase in the rate at which each growing microtubule starts to shrink (catastrophe rate). In principle, this could be brought about by lowering the affinity of stabilizing MAPs for the microtubule wall, by activating a factor that would actively increase the catastrophe rate or by an alteration of both parameters. Here we examine the stabilizing effect of bovine brain MAP2 on microtubules assembled in interphase Xenopus egg extracts. We show that this MAP strongly stabilizes microtubules assembled in the extracts against nocodazole-induced depolymerization. However, it does not protect them from the cdc2 kinase-induced shortening and destabilization. Moreover, the steady-state length of centrosome-nucleated microtubules in cdc2-treated extracts containing MAP2 is similar to that found in extracts lacking exogenous MAP2. We also show that although exogenous MAP2 is phosphorylated by cdc2 kinase in the extract, this is not the cause of microtubule destabilization. These results indicate that increased microtubule dynamics during mitosis is due to the activation of a factor that can function independently of the presence of active, stabilizing factors.