PGC-1α accelerates cytosolic Ca2+ clearance without disturbing Ca2+ homeostasis in cardiac myocytes

Energy metabolism and Ca2+ handling serve critical roles in cardiac physiology and pathophysiology. Peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 alpha) is a multi-functional coactivator that is involved in the regulation of cardiac mitochondrial functional capacity and cellular energy metabolism. However, the regulation of PGC-1 alpha in cardiac Ca2+ signaling has not been fully elucidated. To address this issue, we combined confocal line-scan imaging with off-line imaging processing to characterize calcium signaling in cultured adult rat ventricular myocytes expressing PGC-1 alpha via adenoviral transduction. Our data shows that overexpressing PGC-1 alpha improved myocyte contractility without increasing the amplitude of Ca2+ transients, suggesting that myofilament sensitivity to Ca2+ increased. Interestingly, the decay kinetics of global Ca2+ transients and Ca2+ waves accelerated in PGC-1 alpha-expressing cells, but the decay rate of caffeine-elicited Ca2+ transients showed no significant change. This suggests that sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA2a), but not Na+/Ca2+ exchange (NCX) contribute to PGC-1 alpha-induced cytosolic Ca2+ clearance. Furthermore, PGC-1 alpha induced the expression of SERCA2a in cultured cardiac myocytes. Importantly, overexpressing PGC-1 alpha did not disturb cardiac Ca2+ homeostasis, because SR Ca2+ load and the propensity for Ca2+ waves remained unchanged. These data suggest that PGC-1 alpha can ameliorate cardiac Ca2+ cycling and improve cardiac work output in response to physiological stress. Unraveling the PGC-1 alpha-calcium handing pathway sheds new light on the role of PGC-1 alpha in the therapy of cardiac diseases. (c) 2010 Elsevier Inc. All rights reserved.