title: Hexokinase 1 blocks apoptotic signals at the mitochondria.
abstract: To coordinate a meaningful response to infection or tissue damage, Tumor Necrosis Factor (TNF) triggers a spectrum of reactions in target cells that includes cell activation, differentiation, proliferation and death. Deregulated TNF signaling can lead to tissue damage and organ dysfunction during inflammation. Previously, we identified hexokinase 1 (HK1) as a potent pro-survival factor that counters TNF-induced apoptosis in type II cells. Here we used HK1 siRNA and clotrimazole to generate mitochondrial depletion phenotypes of HK1 to test if HK1 acts at the mitochondria to block TNF-induced apoptosis. We found that HK1 is predominantly mitochondrial in type II cells and that its depletion at the mitochondria decreased the inner mitochondrial membrane potential and accelerated TNF-induced apoptosis. In addition, we showed that the decrease of the mitochondrial membrane potential after HK1 depletion depended on the presence of Bak and Bax and was blocked by Bcl-2 overexpression. From these findings, we conclude that HK1 counters TNF-induced apoptosis through antagonization of pro-apoptotic Bcl-2 proteins at the outer mitochondrial membrane.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB T6G 2S2, Canada.
authors.forename: Anja
authors.initials: A
authors.lastname: Schindler
authors.forename: Edan
authors.initials: E
authors.lastname: Foley
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D006367:HeLa Cells; D006593:Hexokinase / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C472074:HK1 protein, human; D006593:Hexokinase
keywords: Apoptosis; Bcl-2 proteins; HK; Hexokinase; IMM; IMS; MPTP; Mitochondria; Mitochondrial membrane potential; NF-κB; TNF; VDAC; hexokinase; inner mitochondrial membrane; intermembrane space; mitochondrial permeability transition pore; nuclear factor-kappa B; siRNA; small interfering RNA; tumor necrosis factor alpha; voltage dependent anion channel