Multiple signaling pathways regulate contractile activity-mediated PGC-1α
gene expression and activity in skeletal muscle cells
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PGC-1α is an important transcriptional coactivator that plays a key role in mediating mitochondrial biogenesis. Within seconds of the onset of contractile activity, a number of rapid cellular events occur that form part of the initial signaling processes involved in PGC-1α gene regulation, such as elevations in cytoplasmic calcium, AMPK and p38 activation, and elevated ROS production. We observed that basal levels of PGC-1α promoter activity were more sensitive to resting Ca(2+) levels, compared to ROS, p38 or, AMPK signaling. Moreover, enhanced PGC-1α transcription and post-translational activity on DNA were a result of the activation of multiple signal transduction pathways during contractile activity of myotubes. AMPK, ROS, and Ca(2+) appear to be necessary for the regulation of contractile activity-induced PGC-1α gene expression, governed partly through p38 MAPK and CaMKII activity. Whether these signaling pathways are arranged as a linear sequence of events, or as largely independent pathways during contractile activity, remains to be determined.