Induced overexpression of phospholemman S68E mutant improves cardiac contractility and mortality after ischemia-reperfusion.
Phospholemman (PLM), when phosphorylated at Ser(68), inhibits cardiac Na+ / Ca2+ exchanger 1 (NCX1) and relieves its inhibition on Na+ -K+ -ATPase. We have engineered mice in which expression of the phosphomimetic PLM S68E mutant was induced when dietary doxycycline was removed at 5 wk. At 8-10 wk, compared with noninduced or wild-type hearts, S68E expression in induced hearts was ∼35-75% that of endogenous PLM, but protein levels of sarco(endo)plasmic reticulum Ca2+ -ATPase, α1- and α2-subunits of Na+ -K+ -ATPase, α1c-subunit of L-type Ca2+ channel, and phosphorylated ryanodine receptor were unchanged. The NCX1 protein level was increased by ∼47% but the NCX1 current was depressed by ∼34% in induced hearts. Isoproterenol had no effect on NCX1 currents but stimulated Na+ -K+ -ATPase currents equally in induced and noninduced myocytes. At baseline, systolic intracellular Ca2+ concentrations ([Ca2+]i), sarcoplasmic reticulum Ca2+ contents, and [Ca(2+)]i transient and contraction amplitudes were similar between induced and noninduced myocytes. Isoproterenol stimulation resulted in much higher systolic [Ca2+]i, sarcoplasmic reticulum Ca2+ content, and [Ca2+]i transient and contraction amplitudes in induced myocytes. Echocardiography and in vivo close-chest catheterization demonstrated similar baseline myocardial function, but isoproterenol induced a significantly higher +dP/dt in induced compared with noninduced hearts. In contrast to the 50% mortality observed in mice constitutively overexpressing the S68E mutant, induced mice had similar survival as wild-type and noninduced mice. After ischemia-reperfusion, despite similar areas at risk and left ventricular infarct sizes, induced mice had significantly higher +dP/dt and -dP/dt and lower perioperative mortality compared with noninduced mice. We propose that phosphorylated PLM may be a novel therapeutic target in ischemic heart disease.
Center of Translational Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania;
JuFang
J
Wang
Jianliang
J
Song
Erhe
E
Gao
Xue-Qian
XQ
Zhang
Tongda
T
Gu
Daohai
D
Yu
Walter J
WJ
Koch
Arthur M
AM
Feldman
Joseph Y
JY
Cheung
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling; D002316:Cardiotonic Agents / Q000494:pharmacology; D004195:Disease Models, Animal; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D009200:Myocardial Contraction / Q000187:drug effects; D009203:Myocardial Infarction / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D020127:Recovery of Function; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013318:Stroke Volume; D015854:Up-Regulation; D018487:Ventricular Dysfunction, Left / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D016277:Ventricular Function, Left / Q000187:drug effects; D017725:Ventricular Pressure
D000318:Adrenergic beta-Agonists; C514350:CACNA1C protein, mouse; D020746:Calcium Channels, L-Type; D002316:Cardiotonic Agents; D008565:Membrane Proteins; C499849:NCX1 protein, mouse; D010750:Phosphoproteins; D019837:Ryanodine Receptor Calcium Release Channel; D019831:Sodium-Calcium Exchanger; C069141:phospholemman; C401838:Atp1a2 protein, mouse; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C506947:Atp2a2 protein, mouse; C497344:Atp1a1 protein, mouse; D000254:Sodium-Potassium-Exchanging ATPase
FXYD proteins; in vivo hemodynamics; intracellular Ca2+ regulation; ischemic cardiomyopathy