Mitochondrial UCP5 is neuroprotective by preserving mitochondrial membrane potential, ATP levels, and reducing oxidative stress in MPP+ and dopamine toxicity.
We explored the protective mechanisms of human neuronal mitochondrial uncoupling protein-5 (UCP5) in MPP(+)- and dopamine-induced toxicity after its stable overexpression in SH-SY5Y cells. We raised specific polyclonal antibodies. Overexpressed UCP5 localized in mitochondria but not in cytosol. UCP5 overexpression increased proton leak, decreased mitochondrial membrane potential (MMP), reduced ATP production, and increased overall oxygen consumption (demonstrating uncoupling activity). UCP5 overexpression did not affect other neuronal UCP expression (UCP2 and UCP4). Overexpressing UCP5 is protective against MPP(+)- and dopamine-induced toxicity. MPP(+) and dopamine exposure for 6h reduced MMP and increased superoxide levels. ATP levels in UCP5-overexpressing cells were preserved under MPP(+) and dopamine toxicity, comparable to levels in untreated vector controls. At 24h, UCP5 overexpression preserved MMP, ATP levels, and cell survival; attenuated superoxide generation; and maintained oxidative phosphorylation as indicated by lower lactate levels. MPP(+) and dopamine exposure induced UCP5 mRNA transcription but did not decrease transcript degradation, as inhibition of transcription by actinomycin-D abolished induction by either toxin. Compared with our previous studies on UCP4, we observed functional differences between UCP4 and UCP5 in enhancing mitochondrial efficiency. These neuronal UCP homologues may work synergistically to maintain oxidative balance (through uncoupling activities) and ATP production (by modifying MMP).
Kwok
Ken Hon-Hung
KH
Division of Neurology, University Department of Medicine, University of Hong Kong, Hong Kong, China.
Ho
Philip Wing-Lok
PW
Chu
Andrew Chi-Yuen
AC
Ho
Jessica Wing-Man
JW
Liu
Hui-Fang
HF
Yiu
David Chi-Wai
DC
Chan
Koon-Ho
KH
Kung
Michelle Hiu-Wai
MH
Ramsden
David Boyer
DB
Ho
Shu-Leong
SL
D015655:1-Methyl-4-phenylpyridinium / Q000633:toxicity; D000255:Adenosine Triphosphate / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival; D019610:Cytoprotection; D004298:Dopamine / Q000494:pharmacology; D006019:Glycolysis / Q000187:drug effects; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D000071245:Mitochondrial Uncoupling Proteins; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D018384:Oxidative Stress / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism; D019076:Transgenes / Q000235:genetics
D026901:Membrane Transport Proteins; D000071245:Mitochondrial Uncoupling Proteins; D009419:Nerve Tissue Proteins; C116584:SLC25A14 protein, human; D013481:Superoxides; D000255:Adenosine Triphosphate; D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine