title: Calcineurin activity augments cAMP/PKA-dependent activation of V-ATPase in blowfly salivary glands.
abstract: We have examined the role of the Ca(2+)-dependent protein phosphatase 2B (calcineurin) in the regulation of the vacuolar H(+)-ATPase (V-ATPase) in blowfly salivary glands. In response to the neurohormone serotonin [5-hydroxytryptamine (5-HT)] and under the mediation of the cAMP/PKA signaling pathway, the secretory cells assemble and activate V-ATPase molecules at the apical membrane. We demonstrate that the inhibition of calcineurin activity by cyclosporin A, by FK-506, or by prevention of the elevation of Ca(2+) diminishes the 5-HT-induced assembly and activation of V-ATPase. The effect of calcineurin on V-ATPase is mediated by the cAMP/PKA signaling pathway, with calcineurin acting upstream of PKA, because 1) cyclosporin A does not influence the 8-(4-chlorophenylthio)adenosine-3',5'-cyclic monophosphate (8-CPT-cAMP)-induced activation of V-ATPase, and 2) the 5-HT-induced rise in cAMP is highly reduced in the presence of cyclosporin A. Moreover, a Ca(2+) rise evoked by the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) inhibitor cyclopiazonic acid leads to an increase in intracellular cAMP concentration and a calcineurin-mediated PKA-dependent activation of V-ATPase. We propose that calcineurin activity mediates cross talk between the inositol 1,4,5-trisphosphate/Ca(2+) and the cAMP/PKA signaling pathways, thereby augmenting the 5-HT-induced rise in cAMP and thus the cAMP/PKA-mediated activation of V-ATPase.
authors.affiliation: Institut für Biochemie und Biologie, Universität Potsdam, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Voss
authors.forename: Lennart
authors.initials: L
authors.lastname: Fechner
authors.forename: Bernd
authors.initials: B
authors.lastname: Walz
authors.forename: Otto
authors.initials: O
authors.lastname: Baumann
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004175:Diptera / Q000201:enzymology*; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D012469:Salivary Glands / Q000201:enzymology; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*
chemical_list: D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D019703:Calcineurin; D025262:Vacuolar Proton-Translocating ATPases