Key result
A redox-insensitive SERCA C674S mutation attenuated H2O2-stimulated rises in mitochondrial calcium, myocyte apoptosis, and pressure overload-induced myocardial failure in mice.
Why the study?
Because sarcoplasmic reticulum calcium mediates mitochondrial dysfunction from reactive oxygen species, researchers investigated whether SERCA oxidation at cysteine 674 modulates reactive oxygen species effects on mitochondrial calcium and apoptosis in cardiac myocytes.
Does a redox-insensitive SERCA C674S mutation prevent oxidant-stimulated mitochondrial calcium overload and pressure overload-induced myocardial failure in mice?
Does a redox-insensitive SERCA C674S mutation prevent oxidant-stimulated mitochondrial calcium overload and pressure overload-induced myocardial failure in mice?
Redox activation of SERCA C674 mediates pathologic reactive oxygen species-stimulated rise in mitochondrial calcium, leading to myocyte apoptosis and myocardial failure.
Mouse data implicate SERCA oxidation in pressure-overload failure; leaves open redox targeting in human cardiomyopathy.
Background: SERCA [sarco(endo)plasmic reticulum calcium ATPase] is regulated by oxidative posttranslational modifications at cysteine 674 (C674). Because sarcoplasmic reticulum (SR) calcium has been shown to play a critical role in mediating mitochondrial dysfunction in response to reactive oxygen species, we hypothesized that SERCA oxidation at C674 would modulate the effects of reactive oxygen species on mitochondrial calcium and mitochondria-dependent apoptosis in cardiac myocytes. Methods: Adult rat ventricular myocytes expressing wild-type SERCA2b or a redox-insensitive mutant in which C674 is replaced by serine (C674S) were exposed to H 2 O 2 (100 µmol/Lμ). Free mitochondrial calcium concentration was measured in adult rat ventricular myocytes with a genetically targeted fluorescent probe, and SR calcium content was assessed by measuring caffeine-stimulated release. Mice with heterozygous knock-in of the SERCA C674S mutation were subjected to chronic ascending aortic constriction. Results: In adult rat ventricular myocytes expressing wild-type SERCA, H 2 O 2 caused a 25% increase in mitochondrial calcium concentration that was associated with a 50% decrease in SR calcium content, both of which were prevented by the ryanodine receptor inhibitor tetracaine. In cells expressing the C674S mutant, basal SR calcium content was decreased by 31% and the H 2 O 2 -stimulated rise in mitochondrial calcium concentration was attenuated by 40%. In wild-type cells, H 2 O 2 caused cytochrome c release and apoptosis, both of which were prevented in C674S-expressing cells. In myocytes from SERCA knock-in mice, basal SERCA activity and SR calcium content were decreased. To test the effect of C674 oxidation on apoptosis in vivo, SERCA knock-in mice were subjected to chronic ascending aortic constriction. In wild-type mice, ascending aortic constriction caused myocyte apoptosis, LV dilation, and systolic failure, all of which were inhibited in SERCA knock-in mice. Conclusions: Redox activation of SERCA C674 regulates basal SR calcium content, thereby mediating the pathologic reactive oxygen species–stimulated rise in mitochondrial calcium required for myocyte apoptosis and myocardial failure.
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Goodman et al. (2020) studied Pressure overload-induced myocardial failure. SERCA C674S mutation vs. Wild-type SERCA was evaluated on Mitochondrial calcium concentration, SR calcium content, apoptosis, and myocardial failure. A redox-insensitive SERCA C674S mutation attenuated H2O2-stimulated rises in mitochondrial calcium, myocyte apoptosis, and pressure overload-induced myocardial failure in mice.
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