tailieunhanh - Báo cáo khoa học: Identification of ERRa as a specific partner of PGC-1a for the activation of PDK4 gene expression in muscle

Pyruvate dehydrogenase kinase 4 (PDK4) is a key regulatory enzyme involved in switching the energy source from glucose to fatty acids in response to physiological conditions. Transcription of the PDK4gene is activated by fasting or by the administration of a PPARaligand in a tis-sue-specific manner. | ềFEBS Journal Identification of ERRa as a specific partner of PGC-1a for the activation of PDK4 gene expression in muscle Makoto Araki and Kiyoto Motojima Department of Biochemistry Meiji PharmaceuticalUniversity Tokyo Japan Keywords ERRa PGC-1a PPAR pyruvate dehydrogenase kinase skeletalmuscle Correspondence K. Motojima Department of Biochemistry Meiji PharmaceuticalUniversity 2-522-1 Noshio Kiyose Tokyo 204-8588 Japan Tel Fax 81 424 95 8474 E-mail motojima@ Received 13 December 2005 revised 8 February 2006 accepted 16 February 2006 doi Pyruvate dehydrogenase kinase 4 PDK4 is a key regulatory enzyme involved in switching the energy source from glucose to fatty acids in response to physiological conditions. Transcription of the PDK4 gene is activated by fasting or by the administration of a PPARa ligand in a tissue-specific manner. Here we show that the two mechanisms are independent and that ERRa is directly involved in PPARa-independent transcriptional activation of the PDK4 gene with PGC-1a as a specific partner. This conclusion is based on the following evidence. First detailed mutation analyses of the cloned PDK4 gene promoter sequence identified a possible ERRa-binding motif as the PGC-1a responsive element. Second overexpression of ERRa by cotransfection enhanced and the knockout of it by shRNAs diminished PGC-1a-dependent activation. Third specific binding of ERRa to the identified PGC-1a responsive sequence was confirmed by the electrophoresis mobility shift assay. Finally cell-type-specific responsiveness to PGC-1a was observed and this could be explained by differences in the expression levels of ERRa however ectopic expression of ERRa in poorly responsive cells did not restore PGC-1a responsiveness indicating that ERRa is necessary but not sufficient for the response. Metabolic switching of oxidative fuel use from glucose and three-carbon compounds to fatty acids is a key adaptive mechanism to maintain .