Apoptosis inducing factor mediates caspase-independent 1-methyl-4-phenylpyridinium toxicity in dopaminergic cells.
Parkinson's disease is a debilitating neurodegenerative disease characterized by loss of midbrain dopaminergic neurons. These neurons are particularly sensitive to the neurotoxin 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which causes parkinsonian syndromes in humans, monkeys and rodents. Although apoptotic cell death has been implicated in MPTP/MPP+ toxicity, several recent studies have challenged the role of caspase-dependent apoptosis in dopaminergic neurons. Using the midbrain-derived MN9D dopaminergic cell line, we found that MPP+ treatment resulted in an active form of cell death that could not be prevented by caspase inhibitors or over-expression of a dominant negative inhibitor of apoptotic protease activating factor 1/caspase-9. Apoptosis inducing factor (AIF) is a mitochondrial protein that may mediate caspase-independent forms of regulated cell death following its translocation to the nucleus. We found that MPP+ treatment elicited nuclear translocation of AIF accompanied by large-scale DNA fragmentation. To establish the role of AIF in MPP+ toxicity, we constructed a DNA vector encoding a short hairpin sequence targeted against AIF. Reduction of AIF expression by RNA interference inhibited large-scale DNA fragmentation and conferred significant protection against MPP+ toxicity. Studies of primary mouse midbrain cultures further supported a role for AIF in caspase-independent cell death in MPP+-treated dopaminergic neurons.
Chu
Charleen T
CT
Department of Pathology, Division of Neuropathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA. ctc4@pitt.edu
Zhu
Jian-hui
JH
Cao
Guodong
G
Signore
Armando
A
Wang
Suping
S
Chen
Jun
J
D015655:1-Methyl-4-phenylpyridinium / Q000633:toxicity*; D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051033:Apoptosis Inducing Factor; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002460:Cell Line; D053938:DNA Fragmentation / Q000187:drug effects / Q000502:physiology; D004298:Dopamine / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D005420:Flavoproteins / Q000187:drug effects* / Q000378:metabolism; D020267:MPTP Poisoning / Q000378:metabolism / Q000503:physiopathology; D008565:Membrane Proteins / Q000187:drug effects* / Q000378:metabolism; D008636:Mesencephalon / Q000378:metabolism* / Q000503:physiopathology; D051379:Mice; D009410:Nerve Degeneration / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D034622:RNA Interference
D051033:Apoptosis Inducing Factor; D005420:Flavoproteins; D008565:Membrane Proteins; C494830:AIFM1 protein, mouse; D020169:Caspases; D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine