Akt inhibits apoptosis downstream of BID cleavage via a glucose-dependent mechanism involving mitochondrial hexokinases.
The serine/threonine kinase Akt/protein kinase B inhibits apoptosis induced by a variety of stimuli, including overexpression or activation of proapoptotic Bcl-2 family members. The precise mechanisms by which Akt prevents apoptosis are not completely understood, but Akt may function to maintain mitochondrial integrity, thereby preventing cytochrome c release following an apoptotic insult. This effect may be mediated, in part, via promotion of physical and functional interactions between mitochondria and hexokinases. Here we show that growth factor deprivation induced proteolytic cleavage of the proapoptotic Bcl-2 family member BID to yield its active truncated form, tBID. Activated Akt inhibited mitochondrial cytochrome c release and apoptosis following BID cleavage. Akt also antagonized tBID-mediated BAX activation and mitochondrial BAK oligomerization, two downstream events thought to be critical for tBID-induced apoptosis. Glucose deprivation, which impaired the ability of Akt to maintain mitochondrion-hexokinase association, prevented Akt from inhibiting BID-mediated apoptosis. Interestingly, tBID independently elicited dissociation of hexokinases from mitochondria, an effect that was antagonized by activated Akt. Ectopic expression of the amino-terminal half of hexokinase II, which is catalytically active and contains the mitochondrion-binding domain, consistently antagonized tBID-induced apoptosis. These results suggest that Akt inhibits BID-mediated apoptosis downstream of BID cleavage via promotion of mitochondrial hexokinase association and antagonism of tBID-mediated BAX and BAK activation at the mitochondria.
Majewski
Nathan
N
Department of Biochemistry and Molecular Genetics (M/C 669), College of Medicine, University of Illinois at Chicago, 900 S. Ashland Avenue, Chicago, IL 60607, USA.
Nogueira
Veronique
V
Robey
R Brooks
RB
Hay
Nissim
N
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003470:Culture Media; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism*; D006593:Hexokinase / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology; D008954:Models, Biological; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein
D051023:BH3 Interacting Domain Death Agonist Protein; C494774:Bak1 protein, rat; C494828:Bax protein, rat; C494816:Bid protein, rat; D002352:Carrier Proteins; D003470:Culture Media; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D006593:Hexokinase; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose