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

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Abstract
The effects of cAMP‐dependent protein kinase (cAMP‐PK) and Ca2+/calmodulin‐dependent protein kinase II (CaMKII) phosphorylation on the calpain‐mediated degradation of microtubule‐associated protein 2 (MAP‐2) were studied. Both cAMP‐PK and CaMKII readily phosphorylated MAP‐2. However, cAMP‐PK phosphorylated MAP‐2 to a significantly greater extent than did CaMKII (4.5 mol 32P/mol MAP‐2 and 1.4 mol 32P/mol MAP‐2, respectively). Phosphorylation of MAP‐2 by cAMP‐PK, but not by CaMKII, significantly inhibited the calpain‐induced hydrolysis of MAP‐2. These results demonstrate that the phosphorylation of sites on the MAP‐2 molecule accessible to cAMP‐PK, but not to CaMKII, result in increased resistance to calpain proteolysis.