Phosphorylation of microtubule-associated proteins MAP2 and MAP4 by the protein kinase p110(mark) - Phosphorylation sites and regulation of microtubule dynamics

The phosphorylation of microtubule-associated proteins (MAPs) is thought to be a key factor in the regulation of microtubule stability. We have shown recently that a novel protein kinase, termed p110 microtubule-affinity regulating kinase (''MARK''), phosphorylates microtubule-associated protein tau at the KXGS motifs in the region of internal repeats and causes the detach ment of tau from microtubules (Drewes, G., Trinczek, B., Illenberger, S., Biernat, J., Schmitt-Ulms, G., Meyer, H. E., Mandelkow, E.-M., and Mandelkow, E. (1995) J. Biol. Chem, 270, 7679-7688). Here we show that p110(mark) phosphorylates analogous KXGS sites in the microtubule binding domains of the neuronal MAP2 and the ubiquitous MAP4. Phosphorylation in vitro leads to the dissociation of MAP2 and MAP4 from microtubules and to a pronounced increase in dynamic instability, Thus the phosphorylation of the repeated motifs in the micro tubule binding domains of MAPs by p110(mark) might provide a mechanism for the regulation of microtubule dynamics in cells.