title: Uncoupling protein-4 (UCP4) increases ATP supply by interacting with mitochondrial Complex II in neuroblastoma cells.
abstract: Mitochondrial uncoupling protein-4 (UCP4) protects against Complex I deficiency as induced by 1-methyl-4-phenylpyridinium (MPP(+)), but how UCP4 affects mitochondrial function is unclear. Here we investigated how UCP4 affects mitochondrial bioenergetics in SH-SY5Y cells. Cells stably overexpressing UCP4 exhibited higher oxygen consumption (10.1%, p<0.01), with 20% greater proton leak than vector controls (p<0.01). Increased ATP supply was observed in UCP4-overexpressing cells compared to controls (p<0.05). Although state 4 and state 3 respiration rates of UCP4-overexpressing and control cells were similar, Complex II activity in UCP4-overexpressing cells was 30% higher (p<0.05), associated with protein binding between UCP4 and Complex II, but not that of either Complex I or IV. Mitochondrial ADP consumption by succinate-induced respiration was 26% higher in UCP4-overexpressing cells, with 20% higher ADP:O ratio (p<0.05). ADP/ATP exchange rate was not altered by UCP4 overexpression, as shown by unchanged mitochondrial ADP uptake activity. UCP4 overexpression retained normal mitochondrial morphology in situ, with similar mitochondrial membrane potential compared to controls. Our findings elucidate how UCP4 overexpression increases ATP synthesis by specifically interacting with Complex II. This highlights a unique role of UCP4 as a potential regulatory target to modulate mitochondrial Complex II and ATP output in preserving existing neurons against energy crisis.
authors.affiliation: Division of Neurology, University Department of Medicine, University of Hong Kong, Hong Kong, Hong Kong. hwl2002@hku.hk
authors.forename: Philip Wing-Lok
authors.initials: PW
authors.lastname: Ho
authors.forename: Jessica Wing-Man
authors.initials: JW
authors.lastname: Ho
authors.forename: Ho-Man
authors.initials: HM
authors.lastname: Tse
authors.forename: Danny Hon-Fai
authors.initials: DH
authors.lastname: So
authors.forename: David Chi-Wai
authors.initials: DC
authors.lastname: Yiu
authors.forename: Hui-Fang
authors.initials: HF
authors.lastname: Liu
authors.forename: Koon-Ho
authors.initials: KH
authors.lastname: Chan
authors.forename: Michelle Hiu-Wai
authors.initials: MH
authors.lastname: Kung
authors.forename: David Boyer
authors.initials: DB
authors.lastname: Ramsden
authors.forename: Shu-Leong
authors.initials: SL
authors.lastname: Ho
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D042963:Electron Transport Complex II / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D000226:Mitochondrial ADP, ATP Translocases / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D000071245:Mitochondrial Uncoupling Proteins; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010101:Oxygen Consumption; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D000071245:Mitochondrial Uncoupling Proteins; C117577:SLC25A27 protein, human; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D045304:Cytochromes c; D000226:Mitochondrial ADP, ATP Translocases; D042963:Electron Transport Complex II