Protein-kinase-C-catalyzed phosphorylation of the microtubule-binding domain of microtubule-associated protein 2 inhibits its ability to induce tubulin polymerization.
It has previously been demonstrated that microtubule-associated protein 2 (MAP2) is a good substrate for the purified protein kinase C [Tsuyama, S., Bramblett, G. T., Huang, K.-P. & Flavin, M. (1986) J. Biol. Chem. 261, 4110-4116; Akiyama, T., Nishida, E., Ishida, J., Saji, N., Ogawara, H., Hoshi, M., Miyata, Y. & Sakai, H. (1986) J. Biol. Chem. 261, 15648-15651]. We have shown here that phosphorylation of MAP2, catalyzed by protein kinase C, reduces the ability to induce tubulin polymerization. MAP2 is divided into two domains by digestion with alpha-chymotrypsin; the microtubule-binding and the non-binding (projection) domains. The limited chymotryptic digestion following phosphorylation of MAP2 by protein kinase C has shown that both the domains of MAP2 were phosphorylated by protein kinase C, 50-60% of the incorporated phosphates being detected in the microtubule-binding domain. Polypeptide fragments, containing the microtubule-binding domain of MAP2, were purified by DEAE-cellulose column chromatography after chymotryptic digestion of MAP2. The purified microtubule-binding fragments were competent to polymerize tubulin, and served as good substrates for protein kinase C. The phosphorylation of the microtubule-binding fragments by protein kinase C reduced their ability to induce tubulin polymerization. These results suggest that the ability of MAP2 to induce tubulin polymerization is inhibited by phosphorylation of the microtubule-binding domain catalyzed by protein kinase C.
Hoshi
M
M
Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
Akiyama
T
T
Shinohara
Y
Y
Miyata
Y
Y
Ogawara
H
H
Nishida
E
E
Sakai
H
H
D000199:Actins / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000201:enzymology; D002384:Catalysis; D046911:Macromolecular Substances; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011817:Rabbits; D014404:Tubulin / Q000378:metabolism*
D000199:Actins; D046911:Macromolecular Substances; D008869:Microtubule-Associated Proteins; D010446:Peptide Fragments; D010710:Phosphates; D014404:Tubulin; D011493:Protein Kinase C