PHOSPHORYLATION REGULATES THE MICROTUBULE-DESTABILIZING ACTIVITY OF STATHMIN AND ITS INTERACTION WITH TUBULIN

Stathmin is a regulator of microtubule dynamics which undergoes extens ive phosphorylation during the cell cycle as well as in response to va rious extracellular factors. Four serine residues are targets for prot ein kinases: Ser-25 and Ser-38 for proline-directed kinases such as mi togen-activated protein kinase and cyclin-dependent protein kinase, an d Ser-16 and Ser-63 for cAMP-dependent protein kinase. We studied the effect of phosphorylation on the microtubule-destabilizing activity of stathmin and on its interaction with tubulin in vitro, We show that t riple phosphorylation on Ser-16, Ser-25, and Ser-38 efficiently inhibi ts its activity and prevents its binding to tubulin. (C) 1997 Federati on of European Biochemical Societies.