Oxidative posttranslational modifications mediate decreased SERCA activity and myocyte dysfunction in Galphaq-overexpressing mice.
BACKGROUND
Myocyte contractile dysfunction occurs in pathological remodeling in association with abnormalities in calcium regulation. Mice with cardiac myocyte-specific overexpression of Galphaq develop progressive left ventricular failure associated with myocyte contractile dysfunction and calcium dysregulation.


OBJECTIVE
We tested the hypothesis that myocyte contractile dysfunction in the Galphaq mouse heart is mediated by reactive oxygen species, and in particular, oxidative posttranslational modifications, which impair the function of sarcoplasmic reticulum Ca2+-ATPase (SERCA).


RESULTS
Freshly isolated ventricular myocytes from Galphaq mice had marked abnormalities of myocyte contractile function and calcium transients. In Galphaq myocardium, SERCA protein was not altered in quantity but displayed evidence of oxidative cysteine modifications reflected by decreased biotinylated iodoacetamide labeling and evidence of specific irreversible oxidative modifications consisting of sulfonylation at cysteine 674 and nitration at tyrosines 294/295. Maximal calcium-stimulated SERCA activity was decreased 47% in Galphaq myocardium. Cross-breeding Galphaq mice with transgenic mice that have cardiac myocyte-specific overexpression of catalase (a) decreased SERCA oxidative cysteine modifications, (b) decreased SERCA cysteine 674 sulfonylation and tyrosine 294/295 nitration, (c) restored SERCA activity, and (d) improved myocyte calcium transients and contractile function.


CONCLUSIONS
In Galphaq-induced cardiomyopathy, myocyte contractile dysfunction is mediated, at least in part, by 1 or more oxidative posttranslational modifications of SERCA. Protein oxidative posttranslational modifications contribute to the pathophysiology of myocardial dysfunction and thus may provide a target for therapeutic intervention.
Lancel
Steve
S
Cardiovascular Medicine Section, Department of Medicine, Boston University Medical Center, 88 E Newton St, Boston, MA 02118, USA.
Qin
Fuzhong
F
Lennon
Shannon L
SL
Zhang
Jingmei
J
Tong
Xiaoyong
X
Mazzini
Michael J
MJ
Kang
Y James
YJ
Siwik
Deborah A
DA
Cohen
Richard A
RA
Colucci
Wilson S
WS
D000818:Animals; D020013:Calcium Signaling; D002374:Catalase / Q000378:metabolism; D002478:Cells, Cultured; D003545:Cysteine / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000201:enzymology*; D010084:Oxidation-Reduction; D011499:Protein Processing, Post-Translational; D017382:Reactive Oxygen Species / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D015854:Up-Regulation; D018487:Ventricular Dysfunction, Left / Q000201:enzymology* / Q000235:genetics / Q000503:physiopathology / Q000517:prevention & control
D017382:Reactive Oxygen Species; C002744:3-nitrotyrosine; D014443:Tyrosine; D002374:Catalase; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D003545:Cysteine