title: Stimulation of the cardiac myocyte Na+-K+ pump due to reversal of its constitutive oxidative inhibition.
abstract: Protein kinase C can activate NADPH oxidase and induce glutathionylation of the β1-Na(+)-K(+) pump subunit, inhibiting activity of the catalytic α-subunit. To examine if signaling of nitric oxide-induced soluble guanylyl cyclase (sGC)/cGMP/protein kinase G can cause Na(+)-K(+) pump stimulation by counteracting PKC/NADPH oxidase-dependent inhibition, cardiac myocytes were exposed to ANG II to activate NADPH oxidase and inhibit Na(+)-K(+) pump current (Ip). Coexposure to 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) to stimulate sGC prevented the decrease of Ip. Prevention of the decrease was abolished by inhibition of protein phosphatases (PP) 2A but not by inhibition of PP1, and it was reproduced by an activator of PP2A. Consistent with a reciprocal relationship between β1-Na(+)-K(+) pump subunit glutathionylation and pump activity, YC-1 decreased ANG II-induced β1-subunit glutathionylation. The decrease induced by YC-1 was abolished by a PP2A inhibitor. YC-1 decreased phosphorylation of the cytosolic p47(phox) NADPH oxidase subunit and its coimmunoprecipitation with the membranous p22(phox) subunit, and it decreased O2 (·-)-sensitive dihydroethidium fluorescence of myocytes. Addition of recombinant PP2A to myocyte lysate decreased phosphorylation of p47(phox) indicating the subunit could be a substrate for PP2A. The effects of YC-1 to decrease coimmunoprecipitation of p22(phox) and p47(phox) NADPH oxidase subunits and decrease β1-Na(+)-K(+) pump subunit glutathionylation were reproduced by activation of nitric oxide-dependent receptor signaling. We conclude that sGC activation in cardiac myocytes causes a PP2A-dependent decrease in NADPH oxidase activity and a decrease in β1 pump subunit glutathionylation. This could account for pump stimulation with neurohormonal oxidative stress expected in vivo.
authors.affiliation: North Shore Heart Research Group, Kolling Medical Research Institute, University of Sydney, Sydney, Australia; Royal Brisbane and Women's Hospital, The University of Queensland, Queensland, Australia; and.
authors.forename: Karin K M
authors.initials: KK
authors.lastname: Chia
authors.affiliation: North Shore Heart Research Group, Kolling Medical Research Institute, University of Sydney, Sydney, Australia;
authors.forename: Chia-Chi
authors.initials: CC
authors.lastname: Liu
authors.affiliation: North Shore Heart Research Group, Kolling Medical Research Institute, University of Sydney, Sydney, Australia;
authors.forename: Elisha J
authors.initials: EJ
authors.lastname: Hamilton
authors.affiliation: North Shore Heart Research Group, Kolling Medical Research Institute, University of Sydney, Sydney, Australia;
authors.forename: Alvaro
authors.initials: A
authors.lastname: Garcia
authors.affiliation: North Shore Heart Research Group, Kolling Medical Research Institute, University of Sydney, Sydney, Australia;
authors.forename: Natasha A
authors.initials: NA
authors.lastname: Fry
authors.affiliation: North Shore Heart Research Group, Kolling Medical Research Institute, University of Sydney, Sydney, Australia;
authors.forename: William
authors.initials: W
authors.lastname: Hannam
authors.affiliation: North Shore Heart Research Group, Kolling Medical Research Institute, University of Sydney, Sydney, Australia; Department of Cardiology, Royal North Shore Hospital, St. Leonards, Australia.
authors.forename: Gemma A
authors.initials: GA
authors.lastname: Figtree
authors.affiliation: North Shore Heart Research Group, Kolling Medical Research Institute, University of Sydney, Sydney, Australia; Department of Cardiology, Royal North Shore Hospital, St. Leonards, Australia helge.rasmussen@sydney.edu.au.
authors.forename: Helge H
authors.initials: HH
authors.lastname: Rasmussen
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D054648:Protein Phosphatase 2 / Q000378:metabolism; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D054648:Protein Phosphatase 2; D000254:Sodium-Potassium-Exchanging ATPase
keywords: glutathionylation; nitric oxide; oxidative stress; sodium-potassium (Na+-K+)-ATPase; soluble guanylyl cyclase