ATF‐1 is a hypoxia responsive transcriptional activator of UCP3

Abstract

Uncoupling protein 3 (UCP3) confers resilience against oxidative stress in skeletal muscle. We find a marked upregulation of UCP3 expression in response to hypoxia in mice and in skeletal myotubes. Furthermore, in primary myocytes deficient in UCP3, basal and hypoxia-induced ROS levels are elevated. To investigate the regulation mechanism, a transcription factor transfection array of 704 full-length cDNAs in conjunction with a murine UCP3 promoter-luciferase construct was carried out and ATF-1 was identified as a transcriptional activator of UCP3. Site-directed mutagenesis and ChIP assays identify a 10 bp region necessary for ATF-1 induction of UCP3 promoter activity. Hypoxia promotes the phosphorylation of ATF-1 and its depletion by shRNA prevents hypoxia mediated upregulation of UCP3. Pharmacologic inhibition of p38MAP kinase prevents both hypoxia-mediated ATF-1 phosphorylation and UCP3 upregulation. Interestingly, neither PKA signaling nor HIF-1a activation by cobalt chloride modulates skeletal muscle UCP3 protein levels. In conclusion these data identify that ATF-1, via p38MAPK upregulates UCP3 expression in response to hypoxia and identifies a novel regulatory program orchestrating skeletal muscle anti-oxidant defense. Funded by Intramural Research of NHLBI/NIH.