Silencing of PINK1 expression affects mitochondrial DNA and oxidative phosphorylation in dopaminergic cells

• Published in: PloS one Vol. 4; no. 3; p. e4756
• Main Authors: Gegg, Matthew E, Cooper, J Mark, Schapira, Anthony H V, Taanman, Jan-Willem
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 09-03-2009; Public Library of Science (PLoS)
• Subjects: Adenosine Triphosphate - metabolism; Apoptosis; Blotting, Western; Cell Biology/Cellular Death and Stress Responses; Cell death; Cell Survival; Cytosol; Deoxyribonucleic acid; DNA; DNA, Mitochondrial - metabolism; Dopamine - metabolism; Dopamine receptors; Drosophila; Electron transport; Electron transport chain; Evolution; Gene expression; Gene Silencing; Genes; Genetic aspects; Glutathione - metabolism; Humans; Kinases; Membrane potential; Membrane Potential, Mitochondrial; Mitochondria; Mitochondria - metabolism; Mitochondrial DNA; Mitochondrial Membranes - metabolism; Movement disorders; Mutation; Neuroblastoma - metabolism; Neuroblastoma - pathology; Neurodegenerative diseases; Neurological Disorders; Neuroprotection; Neuroscience/Neurobiology of Disease and Regeneration; Neuroscience/Neuronal Signaling Mechanisms; Oxidative Phosphorylation; Oxidative stress; Paraquat; Parkinson's disease; Pathogenesis; Phosphorylation; Protein Kinases - chemistry; Protein Kinases - genetics; Protein Kinases - metabolism; Protein-serine/threonine kinase; PTEN-induced putative kinase; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering - pharmacology; Rodents; Signal transduction; Signaling; siRNA; Substantia nigra; Synthesis; Threonine; Tumor Cells, Cultured
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0004756

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.
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.
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.