title: Translocator Protein (TSPO) Affects Mitochondrial Fatty Acid Oxidation in Steroidogenic Cells.
abstract: Translocator protein (TSPO), also known as the peripheral benzodiazepine receptor, is a highly conserved outer mitochondrial membrane protein present in specific subpopulations of cells within different tissues. In recent studies, the presumptive model depicting mammalian TSPO as a critical cholesterol transporter for steroidogenesis has been refuted by studies examining effects of Tspo gene deletion in vivo and in vitro, biochemical testing of TSPO cholesterol transport function, and specificity of TSPO-mediated pharmacological responses. Nevertheless, high TSPO expression in steroid-producing cells seemed to indicate an alternate function for this protein in steroidogenic mitochondria. To seek an explanation, we used CRISPR/Cas9-mediated TSPO knockout steroidogenic MA-10 Leydig cell (MA-10:TspoΔ/Δ) clones to examine changes to core mitochondrial functions resulting from TSPO deficiency. We observed that 1) MA-10:TspoΔ/Δ cells had a shift in substrate utilization for energy production from glucose to fatty acids with significantly higher mitochondrial fatty acid oxidation (FAO), and increased reactive oxygen species production; and 2) oxygen consumption rate, mitochondrial membrane potential, and proton leak were not different between MA-10:TspoΔ/Δ and MA-10:Tspo+/+ control cells. Consistent with this finding, TSPO-deficient adrenal glands from global TSPO knockout (Tspo(-/-)) mice also showed up-regulation of genes involved in FAO compared with the TSPO floxed (Tspo(fl/fl)) controls. These results demonstrate the first experimental evidence that TSPO can affect mitochondrial energy homeostasis through modulation of FAO, a function that appears to be consistent with high levels of TSPO expression observed in cell types active in lipid storage/metabolism.
authors.affiliation: Department of Animal Science (L.N.T., A.H.Z., M.H., V.S.), College of Agriculture and Life Sciences, Cornell University, Ithaca, New York 14853; and Department of Cell Biology and Biochemistry (D.M.S.), School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
authors.forename: Lan N
authors.initials: LN
authors.lastname: Tu
authors.affiliation: Department of Animal Science (L.N.T., A.H.Z., M.H., V.S.), College of Agriculture and Life Sciences, Cornell University, Ithaca, New York 14853; and Department of Cell Biology and Biochemistry (D.M.S.), School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
authors.forename: Amy H
authors.initials: AH
authors.lastname: Zhao
authors.affiliation: Department of Animal Science (L.N.T., A.H.Z., M.H., V.S.), College of Agriculture and Life Sciences, Cornell University, Ithaca, New York 14853; and Department of Cell Biology and Biochemistry (D.M.S.), School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Hussein
authors.affiliation: Department of Animal Science (L.N.T., A.H.Z., M.H., V.S.), College of Agriculture and Life Sciences, Cornell University, Ithaca, New York 14853; and Department of Cell Biology and Biochemistry (D.M.S.), School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Stocco
authors.affiliation: Department of Animal Science (L.N.T., A.H.Z., M.H., V.S.), College of Agriculture and Life Sciences, Cornell University, Ithaca, New York 14853; and Department of Cell Biology and Biochemistry (D.M.S.), School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
authors.forename: Vimal
authors.initials: V
authors.lastname: Selvaraj
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005227:Fatty Acids / Q000378:metabolism*; D005786:Gene Expression Regulation; D007473:Ion Channels / Q000378:metabolism; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007985:Leydig Cells / Q000378:metabolism*; D050356:Lipid Metabolism / Q000235:genetics; D008297:Male; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D010084:Oxidation-Reduction; D011374:Progesterone / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D018079:Receptors, GABA / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071246:Uncoupling Protein 2; D050995:Voltage-Dependent Anion Channel 1 / Q000378:metabolism
chemical_list: C463819:Bzrp protein, mouse; D005227:Fatty Acids; D007473:Ion Channels; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D018079:Receptors, GABA; D000071246:Uncoupling Protein 2; C494763:Vdac1 protein, mouse; D011374:Progesterone; D007521:Isocitrate Dehydrogenase; C000599591:isocitrate dehydrogenase 2, mouse; D050995:Voltage-Dependent Anion Channel 1