Interaction between calcineurin and Ca2+/calmodulin Kinase-II in modulating cellular functions

Abstract

Roles of calcineurin (CaN), a Ca2+/calmodulin- (CaM-) dependent protein phosphatase, and Ca2+/CaM-dependent protein kinase-II (CaMKII) in modulating K+ channel activity and the intracellular Ca2+ concentration ([Ca2+]i) have been investigated in renal tubule epithelial cells. The channel current through the cell membrane was recorded with the patch-clamp technique, and [Ca 2+]i was monitored using fura-2 imaging. We found that a CaN-inhibitor, cyclosporin A (CyA), lowered the K+ channel activity and elevated [Ca2+]i, suggesting that CyA closes K + channels and opens Ca2+-release channels of the cytosolic Ca2+-store. Moreover, both of these responses were blocked by KN-62, an inhibitor of CaMKII. It is suggested that the CyA-mediated response results from the activation of CaMKII. Indeed, Western blot analysis revealed that CyA increased phospho-CaMKII, an active form of CaMKII. These findings suggest that CaN-dependent dephosphorylation inhibits CaMKII-mediated phosphorylation, and the inhibition of CaN increases phospho-CaMKII, which results in the stimulation of CaMKII-dependent cellular actions. © 2011 Manabu Kubokawa et al.