Glutathiolation and Nitration of Sarcoplasmic Reticulum Ca 2+ ‐ATPase (SERCA) in hearts overexpressing SERCA1a‐pump

Abstract

SERCA pump activity is a major determinant of cardiac contractile function. It has been reported that protein glutathiolation activates whereas protein nitration by peroxynitrite inactivates SERCA. Overexpression of SERCA is associated with increased Ca2+ transport and contractile function; however, the status of gluathiolation or nitration of this protein is unknown. The goal of the present study was to estimate the levels of glutathiolated and nitrated 110-kDa SERCA protein and relates it to Ca2+ uptake and cardiac contractile function. Ca2+ uptake activity and Western blotting (with antibodies to SERCA2a, SERCA1a, glutathione, nitrotyrosine) were performed with cardiac homogenates from nontransgenic (NTG) and SERCA1a transgenic (TG) mice, and cardiac function was measured using Langendorff preparation. Baseline cardiac contractile function and Ca2+ uptake were markedly higher (~2-fold) in isolated TG hearts compared to NTG hearts. Compared to NTG hearts, a marked increase (~2-fold) in glutathiolation of SERCA protein was observed in TG hearts. On the other hand cardiac immunoprecipitates of SERCA2a and SERCA1a proteins demonstrated comparable nitration of 110-kDa protein despite a ~2-fold higher SERCA protein levels in TG hearts. These findings suggest that glutathiolation and nitration may play distinct roles in regulating SERCA pump activity, hence Ca2+ uptake and contractile function.