A MICROTUBULE-ASSOCIATED PROTEIN (MAP2) KINASE RESTORES MICROTUBULE MOTILITY IN EMBRYONIC BRAIN

Motility driven by the microtubule motors, kinesin and cytoplasmic dyn ein, is inhibited by MAP2 (Lopez, L. A., and Sheetz, M. P. (1993) Cell Motil. Cytoskeleton 24, 1-16). The MAP2 inhibition is reversed by a k inase that is co-purified with chicken embryonic MAP2, completely rele asing MAP2 from the microtubules. We have identified this activity wit h a kinase, embryonic MAP2 kinase (M(r) = 100,000), which phosphorylat es MAP2 at serine amino acid residues. This kinase is c-AMP independen t and inhibited by potassium fluoride and glycerol 2-phosphate. Only t he phosphorylation produced by embryonic MAP2 kinase can change the af finity of MAP2 by microtubules. Bovine MAPS kinase, Cdc2 kinase, mitog enic activated protein kinase, and the NIMA kinase are able to phospho rylate MAP2 but do not change the affinity for microtubules. In vivo, embryonic MAP2 kinase could play a major role in the regulation of mot ility and positioning of membranous organelles within the cells even a t substoichiometric levels.