Abstract 18718: The Sarcoplasmic Reticulum Calcium ATPase (SERCA) Cysteine 674 Thiol is Required for Cardiac Myocyte Hypertrophy
Introduction: Cardiac hypertrophy is mediated in part by oxidative stress and calcium-sensitive pathways. The interaction between oxidative stress and calcium signaling is not understood. The activity of SERCA, which maintains calcium stores, is regulated via oxidative post-translational modification of the cysteine 674 (C674) thiol, with stimulation caused by reversible glutathiolation and inhibition of that mechanism by irreversible sulfonylation.
Hypothesis: We used a knock-in mouse in which SERCA C674 is mutated to serine in one allele (SKI mouse), eliminating the thiol and resulting in decreased redox-sensitivity of the enzyme in order to test the hypothesis that redox regulation of SERCA C674 mediates myocardial hypertrophy in vivo and in vitro.
Methods & Results: WT and SKI mice (8-10 weeks old) were subjected to ascending aortic constriction (AAC) for 3 weeks. In WT, AAC increased left ventricular (LV) total wall thickness measured by echocardiography from 1.52 ± 0.02 mm to 1.88 ± 0.06 mm (p<0.001). In SKI, the increase in LV wall thickness with AAC was decreased (1.70 ± 0.04 mm; p<0.05 vs. WT/AAC). Likewise, the heart/body weight ratio after AAC was decreased in SKI (6.6 ± 0.5 mg/g vs. 8.0 ± 0.5 mg/g in WT; p=0.07). Maximal Ca2+-stimulated SERCA activity was unchanged in SKI/AAC (38.7 ± 7.1 nmol Ca/mg/min) vs. WT/AAC (36.0 ± 6.0 nmol Ca/mg/min; p=NS). The mitogen-activated protein kinases p44/42 MAPK (Erk1/2) mediate hypertrophic signaling in cardiac myocytes. Therefore, we measured activation of Erk1/2 (phosphoantibody to Thr202/Tyr204) in isolated adult ventricular myocytes from WT and SKI mice. Alpha-adrenergic receptor (α-AR) stimulation with norepinephrine (NE; 1 μM; 15 min) plus propranolol (2 μM; 30 min pretreatment) increased Erk1/2 phosphorylation by 55 ± 20% (p<0.03) in WT myocytes, whereas in SKI myocytes α-AR stimulation failed to activate Erk (0 ±11%; p<0.03 vs. WT)
Conclusions: SERCA at C674 plays a critical role in mediating myocyte hypertrophy in response to two distinct stimuli - hemodynamic overload in vivo and α-AR stimulation in vitro. Preservation of maximal Ca2+-stimulated SERCA activity in SKI/AAC hearts suggests that reversible redox regulation of SERCA C674 is required for hypertrophic signaling in cardiac myocytes.
Author Disclosures: R.J. Morgan: None. F. Qin: None. D.R. Pimentel: None. D.A. Siwik: None. R.A. Cohen: None. W.S. Colucci: None.
- © 2014 by American Heart Association, Inc.