title: Interaction between Calcineurin and Ca/Calmodulin Kinase-II in Modulating Cellular Functions.
abstract: Roles of calcineurin (CaN), a Ca(2+)/calmodulin- (CaM-) dependent protein phosphatase, and Ca(2+)/CaM-dependent protein kinase-II (CaMKII) in modulating K(+) channel activity and the intracellular Ca(2+) concentration ([Ca(2+)](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 [Ca(2+)](i), suggesting that CyA closes K(+) channels and opens Ca(2+)-release channels of the cytosolic Ca(2+)-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.
authors.affiliation: Department of Physiology, Iwate Medical University School of Medicine, 2-1-1 Nishitokuda, Yahaba, Iwate 028-3694, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Kubokawa
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Nakamura
authors.forename: You
authors.initials: Y
authors.lastname: Komagiri