Mitochondrial import and accumulation of alpha-synuclein impair complex I in human dopaminergic neuronal cultures and Parkinson disease brain.
Alpha-synuclein, a protein implicated in the pathogenesis of Parkinson disease (PD), is thought to affect mitochondrial functions, although the mechanisms of its action remain unclear. In this study we show that the N-terminal 32 amino acids of human alpha-synuclein contain cryptic mitochondrial targeting signal, which is important for mitochondrial targeting of alpha-synuclein. Mitochondrial imported alpha-synuclein is predominantly associated with the inner membrane. Accumulation of wild-type alpha-synuclein in the mitochondria of human dopaminergic neurons caused reduced mitochondrial complex I activity and increased production of reactive oxygen species. However, these defects occurred at an early time point in dopaminergic neurons expressing familial alpha-synuclein with A53T mutation as compared with wild-type alpha-synuclein. Importantly, alpha-synuclein that lacks mitochondrial targeting signal failed to target to the mitochondria and showed no detectable effect on complex I function. The PD relevance of these results was investigated using mitochondria of substantia nigra, striatum, and cerebellum of postmortem late-onset PD and normal human brains. Results showed the constitutive presence of approximately 14-kDa alpha-synuclein in the mitochondria of all three brain regions of normal subjects. Mitochondria of PD-vulnerable substantia nigra and striatum but not cerebellum from PD subjects showed significant accumulation of alpha-synuclein and decreased complex I activity. Analysis of mitochondria from PD brain and alpha-synuclein expressing dopaminergic neuronal cultures using blue native gel electrophoresis and immunocapture technique showed the association of alpha-synuclein with complex I. These results provide evidence that mitochondrial accumulated alpha-synuclein may interact with complex I and interfere with its functions.
Devi
Latha
L
Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA.
Raghavendran
Vijayendran
V
Prabhu
Badanavalu M
BM
Avadhani
Narayan G
NG
Anandatheerthavarada
Hindupur K
HK
D000368:Aged; D000369:Aged, 80 and over; D019943:Amino Acid Substitution; D004298:Dopamine / Q000378:metabolism; D042967:Electron Transport Complex I / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000378:metabolism* / Q000648:ultrastructure; D020125:Mutation, Missense; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D009928:Organ Specificity / Q000235:genetics; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D021382:Protein Sorting Signals / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D051844:alpha-Synuclein / Q000235:genetics / Q000378:metabolism*
D021382:Protein Sorting Signals; D017382:Reactive Oxygen Species; D051844:alpha-Synuclein; D042967:Electron Transport Complex I; D004298:Dopamine