title: Activation of AMP-activated protein kinase stimulates proopiomelanocortin gene transcription in AtT20 corticotroph cells.
abstract: Starvation is known to activate the hypothalamo-pituitary-adrenal (HPA) axis, a representative antistress system in the living organism. In this study, we investigated in vitro whether activation of the AMP-activated protein kinase (AMPK), which is known to occur in intracellular energy depletion, influences the expression of POMC gene that encodes adrenocorticotropin. We first confirmed that each subunit of AMPK was expressed in the AtT20 corticotroph cell line. We then found that AICAR, a cell-permeable AMP analog and an activator of AMPK, potently stimulated the 5'-promoter activity of POMC gene in a dose-dependent manner. The effects were promoter specific because AICAR enhanced the AP1-mediated POMC promoter activities but did not influence other transcription factor-induced transcription. The effect of AICAR on POMC gene transcription was completely eliminated by specific AMPK inhibitor compound C or by dominant negative AMPK, whereas overexpression of constitutively active AMPK mimicked the effect of AICAR. Finally, experiments using specific kinase inhibitors suggested that the PI 3-kinase-mediated signaling pathway is at least partly involved in the effect. Our results suggest that intracellular energy depletion with the resultant activation of AMPK directly stimulates the HPA axis at the pituitary level by increasing the expression of POMC gene.
authors.affiliation: Department of Endocrinology, Metabolism, and Nephrology, Kochi Medical School, Kochi University, Kohasu, Japan. iwasaki@kochi-u.ac.jp
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Iwasaki
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Nishiyama
authors.forename: Takafumi
authors.initials: T
authors.lastname: Taguchi
authors.forename: Machiko
authors.initials: M
authors.lastname: Kambayashi
authors.forename: Masato
authors.initials: M
authors.lastname: Asai
authors.forename: Masanori
authors.initials: M
authors.lastname: Yoshida
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nigawara
authors.forename: Kozo
authors.initials: K
authors.lastname: Hashimoto
mesh_terms: D055372:AMP-Activated Protein Kinases; D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000620:Aminoimidazole Carboxamide / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D052680:Corticotrophs / Q000378:metabolism*; D003346:Corticotropin-Releasing Hormone / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects; D005786:Gene Expression Regulation; D009097:Multienzyme Complexes / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011333:Pro-Opiomelanocortin / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012265:Ribonucleotides / Q000008:administration & dosage / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D018808:Transcription Factor AP-1 / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*
chemical_list: D009097:Multienzyme Complexes; D012333:RNA, Messenger; D012265:Ribonucleotides; D018808:Transcription Factor AP-1; D000620:Aminoimidazole Carboxamide; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide