AMPK activation represses the human gene promoter of the cardiac isoform of acetyl-CoA carboxylase: Role of nuclear respiratory factor-1.
The cardiac-enriched isoform of acetyl-CoA carboxylase (ACCbeta) produces malonyl-CoA, a potent inhibitor of carnitine palmitoyltransferase-1. AMPK inhibits ACCbeta activity, lowering malonyl-CoA levels and promoting mitochondrial fatty acid beta-oxidation. Previously, AMPK increased promoter binding of nuclear respiratory factor-1 (NRF-1), a pivotal transcriptional modulator controlling gene expression of mitochondrial proteins. We therefore hypothesized that NRF-1 inhibits myocardial ACCbeta promoter activity via AMPK activation. A human ACCbeta promoter-luciferase construct was transiently transfected into neonatal cardiomyocytes+/-a NRF-1 expression construct. NRF-1 overexpression decreased ACCbeta gene promoter activity by 71+/-4.6% (p<0.001 vs. control). Transfections with 5'-end serial promoter deletions revealed that NRF-1-mediated repression of ACCbeta was abolished with a pPIIbeta-18/+65-Luc deletion construct. AMPK activation dose-dependently reduced ACCbeta promoter activity, while NRF-1 addition did not further decrease it. We also investigated NRF-1 inhibition in the presence of upstream stimulatory factor 1 (USF1), a known transactivator of the human ACCbeta gene promoter. Here NRF-1 blunted USF1-dependent induction of ACCbeta promoter activity by 58+/-7.5% (p<0.001 vs. control), reversed with a dominant negative NRF-1 construct. NRF-1 also suppressed endogenous USF1 transcriptional activity by 55+/-6.2% (p<0.001 vs. control). This study demonstrates that NRF-1 is a novel transcriptional inhibitor of the human ACCbeta gene promoter in the mammalian heart. Our data extends AMPK regulation of ACCbeta to the transcriptional level.
Adam
Tasneem
T
Hatter Cardiovascular Research Institute, Faculty of Health Sciences, University of Cape Town, Observatory 7925, South Africa.
Opie
Lionel H
LH
Essop
M Faadiel
MF
D000091162:AMP-Activated Protein Kinase Kinases; D000103:Acetyl-CoA Carboxylase / Q000235:genetics*; D000818:Animals; D002478:Cells, Cultured; D004794:Enzyme Repression; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000235:genetics; D009206:Myocardium / Q000201:enzymology*; D051266:Nuclear Respiratory Factor 1 / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics; D011494:Protein Kinases / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D012097:Repressor Proteins / Q000378:metabolism*; D051720:Upstream Stimulatory Factors / Q000378:metabolism
D051266:Nuclear Respiratory Factor 1; D020033:Protein Isoforms; D012097:Repressor Proteins; C497181:USF1 protein, human; D051720:Upstream Stimulatory Factors; D008156:Luciferases; D011494:Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases; C520105:ACACB protein, human; D000103:Acetyl-CoA Carboxylase