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.
Bronner
Myriam
M
Department of Human Nutrition and Metabolism, Hebrew University Faculty of Medicine, P.O. Box 12272, Jerusalem 91120, Israel.
Hertz
Rachel
R
Bar-Tana
Jacob
J
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