Dephosphorylation of autophosphorylated Ca2+/calmodulin-dependent protein kinase II by protein phosphatase 2C.

It has been demonstrated that okadaic acid-insensitive protein phosphatases are involved in dephosphorylation of autophosphorylated Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) in rat cerebellar granule cells (Fukunaga, K., Rich, D. P., and Soderling, T. R. (1989) J. Biol. Chem. 264, 21830-21836). In the present study, recombinant rat protein phosphatase 2C (PrP-2C) expressed in Escherichia coli could dephosphorylate both Thr286/287 and Thr305/306 phosphorylation sites of CaM kinase II, which are responsible for the generation of Ca(2+)-independent activity and the inhibition of the total activity, respectively. The dephosphorylation of Thr286/287 and Thr305/306 was accomplished within 15 min at 0 degrees C and totally dependent on Mg2+. Phosphopeptide mapping of the CNBr-cleaved 32P-labeled CaM kinase II revealed that PrP-2C was relatively specific for dephosphorylation of Thr286/287 and Thr305/306 in the autophosphorylated CaM kinase II. These results suggest that PrP-2C has a role in the regulation of the Ca(2+)-independent activity of CaM kinase II in the neural cells.