The sarcoplasmic reticulum Ca2+-ATPase (SERCA2) gene promoter activity is decreased in response to severe left ventricular pressure-overload hypertrophy in rat hearts

The sarcoplasmic reticulum Ca2+-ATPase (SERCA2) pump plays a key role in th e contraction-relaxation cycle of the myocardium by controlling the intrace llular Ca2+ concentration. SERCA2 protein and mRNA expression levels, as we ll as, SR Ca2+ uptake function are depressed in hypertrophied and failing m yocardium. At this time, the molecular mechanisms regulating SERCA2 gene tr anscription during hypertrophy and heart failure are not completely underst ood, especially in viva. Direct gene transfer into adult cardiac tissue has recently been shown to be a useful technique to study in vivo gene regulat ion. In this study, SERCA2 promoter-luciferase (Luc) reporter constructs of various lengths were injected into the beating left ventricular apex of ad ult rats (groups = compensated hypertrophy, heart failure, and controls) an d the expression level was analysed. Our SERCA2 promoter analyses revealed three positive regulatory regions bet ween -1810 bp and -1110 bp, - 658 bp and -284 bp, and - 267 bp and - 72 bp and a negative regulatory region between -1110 bp and - 658 bp, important f or in vivo expression in rat hearts. SERCA2 promoter activity was also asse ssed in rat hearts with compensated pressure-overload hypertrophy (induced by the DOCA-salt treatment) and heart failure (induced by severe ascending aortic constriction). In the DOCA-salt-induced hypertrophy model, SERCA2 pr omoter activity was similar to that of sham controls. In contrast. severe c onstriction of the ascending aorta decreased the expression of the -1810 Lu c and -1110 Luc constructs by 92.8% and 64.3%, respectively. This study sug gests that only severe pressure-overload hypertrophy produces a significant decrease in SERCA2 promoter activity, and the promoter region extending to -1810 bp is sufficient for the down regulation of SERCA2 gene expression. (C) 1999 Academic Press.