Endoplasmic reticulum stress and mitochondrial cell death pathways mediate A53T mutant alpha-synuclein-induced toxicity.
Parkinson's disease (PD) is a neurodegenerative movement disorder characterized by selective loss of dopaminergic neurons and the presence of Lewy bodies. Alpha-synuclein is a major component of Lewy bodies in sporadic PD, and mutations in alpha-synuclein cause autosomal-dominant hereditary PD. Here, we generated A53T mutant alpha-synuclein-inducible PC12 cell lines using the Tet-off regulatory system. Inducing expression of A53T alpha-synuclein in differentiated PC12 cells decreased proteasome activity, increased the intracellular ROS level and caused up to approximately 40% cell death, which was accompanied by mitochondrial cytochrome C release and elevation of caspase-9 and -3 activities. Cell death was partially blocked by cyclosporine A [an inhibitor of the mitochondrial permeability transition (MPT) process], z-VAD (a pan-caspase inhibitor) and inhibitors of caspase-9 and -3 but not by a caspase-8 inhibitor. Furthermore, induction of A53T alpha-synuclein increased endoplasmic reticulum (ER) stress and elevated caspase-12 activity. RNA interference to knock down caspase-12 levels or salubrinal (an ER stress inhibitor) partially protected against cell death and further reduced A53T toxicity after treatment with z-VAD. Our results indicate that both ER stress and mitochondrial dysfunction contribute to A53T alpha-synuclein-induced cell death. This study sheds light into the pathogenesis of alpha-synuclein cellular toxicity in PD and provides a cell model for screening PD therapeutic agents.
Smith
Wanli W
WW
Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Jiang
Haibing
H
Pei
Zhong
Z
Tanaka
Yuji
Y
Morita
Hokuto
H
Sawa
Akira
A
Dawson
Valina L
VL
Dawson
Ted M
TM
Ross
Christopher A
CA
D000818:Animals; D061945:Caspase Inhibitors; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000502:physiology*; D004789:Enzyme Activation; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D016716:PC12 Cells; D010300:Parkinson Disease / Q000378:metabolism / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D051844:alpha-Synuclein / Q000235:genetics* / Q000378:metabolism
D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D017382:Reactive Oxygen Species; D051844:alpha-Synuclein; D045304:Cytochromes c; D020169:Caspases; D046988:Proteasome Endopeptidase Complex