title: Hexokinase regulates Bax-mediated mitochondrial membrane injury following ischemic stress.
abstract: Hexokinase (HK), the rate-limiting enzyme in glycolysis, controls cell survival by promoting metabolism and/or inhibiting apoptosis. Since HK isoforms I and II have mitochondrial targeting sequences, we attempted to separate the protective effects of HK on cell metabolism from those on apoptosis. We exposed renal epithelial cells to metabolic stress causing ATP depletion in the absence of glucose and found that this activated glycogen synthase kinase 3β (GSK3β) and Bax caused mitochondrial membrane injury and apoptosis. ATP depletion led to a progressive HK II dissociation from mitochondria, released mitochondrial apoptosis inducing factor and cytochrome c into the cytosol, activated caspase-3, and reduced cell survival. Compared with control, adenoviral-mediated HK I or II overexpression improved cell survival following stress, but did not prevent GSK3β or Bax activation, improve ATP content, or reduce mitochondrial fragmentation. HK I or HK II overexpression increased mitochondria-associated isoform-specific HK content, and decreased mitochondrial membrane injury and apoptosis after stress. In vivo, HK II localized exclusively to the proximal tubule. Ischemia reduced total renal HK II content and dissociated HK II from proximal tubule mitochondria. In cells overexpressing HK II, Bax and HK II did not interact before or after stress. While the mechanism by which HK antagonizes Bax-mediated apoptosis is unresolved by these studies, one possible scenario is that the two proteins compete for a common binding site on the outer mitochondrial membrane.
authors: Renal Section, Department of Medicine, Boston Medical Center, Boston University School of Medicine, Massachusetts, USA.
authors: Jonathan M
authors: JM
authors: Gall
authors: Vincent
authors: V
authors: Wong
authors: David R
authors: DR
authors: Pimental
authors: Andrea
authors: A
authors: Havasi
authors: Zhiyong
authors: Z
authors: Wang
authors: John G
authors: JG
authors: Pastorino
authors: Ramon G B
authors: RG
authors: Bonegio
authors: John H
authors: JH
authors: Schwartz
authors: Steven C
authors: SC
authors: Borkan
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000201:enzymology* / Q000473:pathology; D005947:Glucose / Q000172:deficiency; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006593:Hexokinase / Q000235:genetics / Q000378:metabolism*; D007674:Kidney Diseases / Q000201:enzymology* / Q000473:pathology; D007687:Kidney Tubules, Proximal / Q000098:blood supply / Q000201:enzymology* / Q000473:pathology; D051379:Mice; D051336:Mitochondrial Membranes / Q000201:enzymology* / Q000473:pathology; D009893:Opossums; D021381:Protein Transport; D015427:Reperfusion Injury / Q000201:enzymology* / Q000473:pathology; D015398:Signal Transduction; D013312:Stress, Physiological; D013997:Time Factors; D014162:Transfection; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
chemical_list: C494827:Bax protein, mouse; D051028:bcl-2-Associated X Protein; D000255:Adenosine Triphosphate; D045304:Cytochromes c; C515658:HK1 protein, mouse; D006593:Hexokinase; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3; D053148:Caspase 3; D005947:Glucose