CALPAIN-MEDIATED PROTEOLYSIS OF MICROTUBULE-ASSOCIATED PROTEIN-2 (MAP-2) IS INHIBITED BY PHOSPHORYLATION BY CAMP-DEPENDENT PROTEIN-KINASE, BUT NOT BY CA2+ CALMODULIN-DEPENDENT PROTEIN KINASE-II/

The effects of cAMP-dependent protein kinase (cAMP-PK) and Ca2+/calmod ulin-dependent protein kinase II (CaMKII) phosphorylation on the calpa in-mediated degradation of microtubule-associated protein 2 (MAP-2) we re studied. Both cAMP-PK and CaMKII readily phosphorylated MAP-2. Howe ver, cAMP-PK phosphorylated MAP-2 to a significantly greater extent th an did CaMKII (4.5 mol P-32/mol MAP-2 and 1.4 mol P-32/mol MAP-2, resp ectively). Phosphorylation of MAP-2 by cAMP-PK, but not by CaMKII, sig nificantly inhibited the calpain-induced hydrolysis of MAP-2. These re sults demonstrate that the phosphorylation of sites on the MAP-2 molec ule accessible to cAMP-PK, but not to CaMKII, result in increased resi stance to calpain proteolysis.