Identification and characterization of CaMKP-N, nuclear calmodulin-dependent protein kinase phosphatase

Calmodulin-dependent protein kinase phosphatase (CaMKP) dephosphorylates an d concomitantly deactivates multifunctional Ca2+/calmodulin-dependent prote in kinases (CaMKs), such as CaMKI, CaMKII, and CaMKIV. In the present study , a nuclear CaMKP-related protein, CaMKP-N, was identified. This protein co nsisted of 757 amino acid residues with a calculated molecular weight of 84 ,176. Recombinant CaMKP-N dephosphorylated CaMKIV. The activity of CaMKP-N requires Mn2+ ions and is stimulated by polycations. Transiently expressed CaMKP-N in COS-7 cells was localized in the nucleus. This finding together with previous reports regarding localization of CaMKs indicates that CaMKP- N dephosphorylates CaMKIV and nuclear CaMKII, whereas CaMKP dephosphorylate s CaMKI and cytosolic CaMKII.