Kinase-independent transcriptional co-activation of peroxisome proliferator-activated receptor alpha by AMP-activated protein kinase.
AMPK (AMP-activated protein kinase) responds to intracellular ATP depletion, while PPARalpha (peroxisome proliferator-activated receptor alpha) induces the expression of genes coding for enzymes and proteins involved in increasing cellular ATP yields. PPARalpha-mediated transcription is shown here to be co-activated by the alpha subunit of AMPK, as well as by kinase-deficient (Thr172Ala) and kinase-less (Asp157Ala, Asp139Ala) mutants of AMPKalpha. The Ser452Ala mutant of mPPARalpha mutated in its putative consensus AMPKalpha phosphorylation site is similarly co-activated by AMPKalpha. AMPKalpha or its kinase-less mutants bind to PPARalpha; binding is increased by MgATP, to a lesser extent by MgADP, but not at all by AMP or ZMP [AICAR (5-aminoimidazole-4-carboxamide ribonucleoside) monophosphate]. ATP-activated binding of AMPKalpha to PPARalpha is mediated primarily by the C-terminal regulatory domain of AMPKalpha. PPARalpha co-activation by AMPKalpha may, however, require its secondary interaction with the N-terminal catalytic domain of AMPKalpha, independently of its kinase activity. While AMPK catalytic activity is activated by AICAR, PPARalpha co-activation and PPARalpha-controlled transcription are robustly inhibited by AICAR, with concomitant translocation of nuclear AMPKalpha or its kinase-less mutants to the cytosol. In conclusion, AMPKalpha, independently of its kinase activity, co-activates PPARalpha both in primary rat hepatocytes and in PPARalpha-transfected cells. The kinase and transcriptional co-activation modes of AMPKalpha are both regulated by the cellular ATP/AMP ratio. Co-activation of PPARalpha by AMPKalpha may transcriptionally complement AMPK in maintaining cellular ATP status.
Department of Human Nutrition and Metabolism, Hebrew University Faculty of Medicine, P.O. Box 12272, Jerusalem 91120, Israel.
Myriam
M
Bronner
Rachel
R
Hertz
Jacob
J
Bar-Tana
D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D019556:COS Cells / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D006367:HeLa Cells / Q000737:chemistry / Q000378:metabolism; D022781:Hepatocytes / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000196:embryology; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D047493:PPAR alpha / Q000235:genetics* / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D012265:Ribonucleotides / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology*; D014162:Transfection
D009097:Multienzyme Complexes; D047493:PPAR alpha; D021122:Protein Subunits; D012265:Ribonucleotides; D000620:Aminoimidazole Carboxamide; D010770:Phosphotransferases; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide