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TRANSCRIPTION IN SKELETAL MUSCLE CELLS
1 Biology, York University, Toronto, Canada
2 Dept. of Kinesiology, York University, Toronto, Canada
3 Dept. of Kinesiology, York University, 4700 Keele St., Toronto, M3J 1P3, Canada; Biology, York University, Toronto, Canada
* To whom correspondence should be addressed. E-mail: dhood{at}yorku.ca.
Reactive oxygen species (ROS) play an important role in cellular function via the activation of signaling cascades. ROS have been shown to affect mitochondrial biogenesis, morphology and function. Their beneficial effects are likely mediated via the upregulation of transcriptional regulators such as PGC-1
. However, the ROS signals that regulate PGC-1 transcription in skeletal muscle are not understood. Here we examined the effect of H2O2 on the regulation of PGC-1 expression, and its relationship to AMPK activation. We demonstrate that 24 hours of exogenous H2O2 treatment increased PGC-1 promoter activity and mRNA expression. Both effects were blocked with the addition of NAC, a ROS scavenger. These effects were mediated, in part, via USF-1/Ebox DNA binding, and involved 1) interactions with downstream sequences, and 2) the activation of AMPK. Elevated ROS led to the activation of AMPK, likely via a decline in ATP levels. The activation of AMPK using AICAR increased PGC-1 promoter activity and mRNA levels, but reduced ROS production. Thus, the net effect of AMPK activation on PGC-1 expression was a result of increased transcriptional activation, counterbalanced by reduced ROS production. The effects of H2O2 on PGC-1 expression differed depending on the level of ROS within the cell. Low levels of ROS result in reduced PGC-1 mRNA in the absence an effect on PGC-1 promoter activation. In contrast, elevated levels of H2O2 induce PGC-1 transcription indirectly, via AMPK activation. These data identify unique interactions between ROS and AMPK activation on the expression of PGC-1 in muscle cells.
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