title: Adenosine activates AMPK to phosphorylate Bcl-XL responsible for mitochondrial damage and DIABLO release in HuH-7 cells.
abstract: OBJECTIVE
  Accumulating evidence has pointed to AMP-activated protein kinase (AMPK) as an inducer of apoptosis in a variety of cancer cells. The present study aimed at understanding AMPK signals for adenosine-induced HuH-7 cell apoptosis.
  
  
  METHODS
  Cell viability, AMPK activity, mitochondrial membrane potentials, phosphorylation of Bcl-X(L), in situ DIABLO mobilizations, and caspase-3 activity were monitored in HuH-7 cells. Plasmid DNAs for DIABLO-GFP, mutant Bcl-X(L), dominant negative mutant AMPKα2 and the siRNAs to silence the AMPKα1 or AMPKα2 targeted gene were constructed and transfected.
  
  
  RESULTS
  Adenosine or the AMPK activator AICAR induced apoptosis in HuH-7 cells, and no synergistic effect was obtained with co-treatment. Adenosine activated AMPK, to phosphorylate Bcl-X(L). Adenosine or AICAR disrupted mitochondrial membrane potentials, and the effect was inhibited by knocking-down AMPKα1 and/or AMPKα2, expressing dominant negative mutant AMPKα2 or mutant Bcl-X(L) lacking Ser/Thr phosphorylation sites. AICAR stimulated DIABLO release from the mitochondria, and the release was suppressed by expressing the mutant Bcl-X(L). AICAR activated caspase-3, which was also inhibited by expressing the mutant Bcl-X(L).
  
  
  CONCLUSIONS
  Adenosine activates AMPK, to disrupt mitochondrial membrane potentials through Bcl-X(L) phosphorylation, allowing DIABLO release from the mitochondria, as a factor for caspase-3 activation to induce HuH-7 cell apoptosis.
authors.affiliation: Division of Bioinformation, Department of Physiology, Hyogo College of Medicine, Nishinomiya, Japan.
authors.forename: Donqin
authors.initials: D
authors.lastname: Yang
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yaguchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Nishizaki
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000241:Adenosine / Q000494:pharmacology*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D045744:Cell Line, Tumor; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D010766:Phosphorylation; D034622:RNA Interference; D034741:RNA, Small Interfering; D012265:Ribonucleotides / Q000494:pharmacology; D051020:bcl-X Protein / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D034741:RNA, Small Interfering; D012265:Ribonucleotides; D051020:bcl-X Protein; D000620:Aminoimidazole Carboxamide; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide; D000241:Adenosine