Bhlhe40 Represses PGC-1α Activity on Metabolic Gene Promoters in Myogenic Cells

Abstract

PGC-1α is a transcriptional coactivator promoting oxidative metabolism in many tissues. Its expression in skeletal muscle (SKM) is induced by hypoxia and reactive oxidative species (ROS) generated during exercise, suggesting that PGC-1α might mediate the cross talk between oxidative metabolism and cellular responses to hypoxia and ROS. Here we found that PGC-1α directly interacted with Bhlhe40, a basic helix-loop-helix (bHLH) transcriptional repressor induced by hypoxia, and protects SKM from ROS damage, and they cooccupied PGC-1α-targeted gene promoters/enhancers, which in turn repressed PGC-1α transactivational activity. Bhlhe40 repressed PGC-1α activity through recruiting histone deacetylases (HDACs) and preventing the relief of PGC-1α intramolecular repression caused by its own intrinsic suppressor domain. Knockdown of Bhlhe40 mRNA increased levels of ROS, fatty acid oxidation, mitochondrial DNA, and expression of PGC-1α target genes. Similar effects were also observed when the Bhlhe40-mediated repression was rescued by a dominantly active form of the PGC-1α-interacting domain (PID) from Bhlhe40. We further found that Bhlhe40-mediated repression can be largely relieved by exercise, in which its recruitment to PGC-1α-targeted cis elements was significantly reduced. These observations suggest that Bhlhe40 is a novel regulator of PGC-1α activity repressing oxidative metabolism gene expression and mitochondrion biogenesis in sedentary SKM.

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00387-15.

ACKNOWLEDGMENTS

We thank Anastasia Kralli (Division of Biochemistry, University of Basel, Basel, Switzerland) for providing the pCDNA3-PGC-1α plasmid, Ssu Ching Chen (Department of Life Sciences, National Central University) for help with the ROS assay, and Rick Sturm (Institute for Bioscience, University of Queensland) for providing the Tet-off inducible expression system. We are also grateful to Bertrand Chin-Ming Tan (Chang Gung University) and Shuang En-Chuang (National Health Research Institutes) for their help during the revision period.

This study was supported by funding from the National Science Council of Taiwan, Republic of China, to Shen Liang Chen (NSC-102-2311-B-008-003 and NSC-99-2314-B-008-001-MY3).

We have no conflict of interest to declare.