Silencing of PINK1 expression affects mitochondrial DNA and oxidative phosphorylation in dopaminergic cells.
BACKGROUND
Mitochondrial dysfunction has been implicated in the pathogenesis of Parkinson's disease (PD). Impairment of the mitochondrial electron transport chain (ETC) and an increased frequency in deletions of mitochondrial DNA (mtDNA), which encodes some of the subunits of the ETC, have been reported in the substantia nigra of PD brains. The identification of mutations in the PINK1 gene, which cause an autosomal recessive form of PD, has supported mitochondrial involvement in PD. The PINK1 protein is a serine/threonine kinase localized in mitochondria and the cytosol. Its precise function is unknown, but it is involved in neuroprotection against a variety of stress signalling pathways.


RESULTS
In this report we have investigated the effect of silencing PINK1 expression in human dopaminergic SH-SY5Y cells by siRNA on mtDNA synthesis and ETC function. Loss of PINK1 expression resulted in a decrease in mtDNA levels and mtDNA synthesis. We also report a concomitant loss of mitochondrial membrane potential and decreased mitochondrial ATP synthesis, with the activity of complex IV of the ETC most affected. This mitochondrial dysfunction resulted in increased markers of oxidative stress under basal conditions and increased cell death following treatment with the free radical generator paraquat.


CONCLUSIONS
This report highlights a novel function of PINK1 in mitochondrial biogenesis and a role in maintaining mitochondrial ETC activity. Dysfunction of both has been implicated in sporadic forms of PD suggesting that these may be key pathways in the development of the disease.
Gegg
Matthew E
ME
Department of Clinical Neurosciences, Institute of Neurology, University College London, Queen Square, London, United Kingdom.
Cooper
J Mark
JM
Schapira
Anthony H V
AH
Taanman
Jan-Willem
JW
D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis; D015153:Blotting, Western; D002470:Cell Survival; D004272:DNA, Mitochondrial / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D020868:Gene Silencing; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism / Q000473:pathology*; D010085:Oxidative Phosphorylation; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D000099202:PTEN-Induced Putative Kinase
D000255:Adenosine Triphosphate; D004272:DNA, Mitochondrial; D004298:Dopamine; D005978:Glutathione; D011494:Protein Kinases; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000099202:PTEN-Induced Putative Kinase