title: Voltage-dependent anion channels modulate mitochondrial metabolism in cancer cells: regulation by free tubulin and erastin.
abstract: Respiratory substrates and adenine nucleotides cross the mitochondrial outer membrane through the voltage-dependent anion channel (VDAC), comprising three isoforms--VDAC1, 2, and 3. We characterized the role of individual isoforms in mitochondrial metabolism by HepG2 human hepatoma cells using siRNA. With VDAC3 to the greatest extent, all VDAC isoforms contributed to the maintenance of mitochondrial membrane potential, but only VDAC3 knockdown decreased ATP, ADP, NAD(P)H, and mitochondrial redox state. Cells expressing predominantly VDAC3 were least sensitive to depolarization induced by increased free tubulin. In planar lipid bilayers, free tubulin inhibited VDAC1 and VDAC2 but not VDAC3. Erastin, a compound that interacts with VDAC, blocked and reversed mitochondrial depolarization after microtubule destabilizers in intact cells and antagonized tubulin-induced VDAC blockage in planar bilayers. In conclusion, free tubulin inhibits VDAC1/2 and limits mitochondrial metabolism in HepG2 cells, contributing to the Warburg phenomenon. Reversal of tubulin-VDAC interaction by erastin antagonizes Warburg metabolism and restores oxidative mitochondrial metabolism.
authors.affiliation: Center for Cell Death, Injury & Regeneration, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
authors.forename: Eduardo N
authors.initials: EN
authors.lastname: Maldonado
authors.forename: Kely L
authors.initials: KL
authors.lastname: Sheldon
authors.forename: David N
authors.initials: DN
authors.lastname: DeHart
authors.forename: Jyoti
authors.initials: J
authors.lastname: Patnaik
authors.forename: Yefim
authors.initials: Y
authors.lastname: Manevich
authors.forename: Danyelle M
authors.initials: DM
authors.lastname: Townsend
authors.forename: Sergey M
authors.initials: SM
authors.lastname: Bezrukov
authors.forename: Tatiana K
authors.initials: TK
authors.lastname: Rostovtseva
authors.forename: John J
authors.initials: JJ
authors.lastname: Lemasters
mesh_terms: D000244:Adenosine Diphosphate / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000235:genetics / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D056945:Hep G2 Cells; D006801:Humans; D008051:Lipid Bilayers / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009249:NADP / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D010879:Piperazines / Q000494:pharmacology*; D014404:Tubulin / Q000378:metabolism*; D050994:Voltage-Dependent Anion Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D008051:Lipid Bilayers; D024101:Mitochondrial Proteins; D009363:Neoplasm Proteins; D010879:Piperazines; D014404:Tubulin; D050994:Voltage-Dependent Anion Channels; C477224:erastin; D009249:NADP; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate