Wild-type alpha-synuclein interacts with pro-apoptotic proteins PKCdelta and BAD to protect dopaminergic neuronal cells against MPP+-induced apoptotic cell death.
Alpha-synuclein is a pre-synaptic protein of unknown function that has been implicated in the pathogenesis of Parkinson's disease (PD). Recently, we demonstrated that 1-methyl-4-phenylpyridinium (MPP+) induces caspase-3-dependent proteolytic activation of PKCdelta, which subsequently contributes to neuronal apoptotic cell death in mesencephalic dopaminergic neuronal cells. In the present study, we examined whether PKCdelta interacts with alpha-synuclein to modulate MPP+-induced dopaminergic degeneration. Over-expression of wild-type human alpha-synuclein in mesencephalic dopaminergic neuronal cells (N27 cells) attenuated MPP+-induced (300 microM) cytotoxicity, release of mitochondrial cytochrome c, and subsequent caspase-3 activation, without affecting reactive oxygen species (ROS) generation. Wild-type alpha-synuclein over-expression also dramatically reduced MPP+-induced caspase-3-mediated proteolytic cleavage of PKCdelta, whereas over-expression of the mutant human alpha-synucleinA53T did not alter the PKCdelta cleavage under similar conditions. Immunoprecipitation-kinase assay revealed reduced PKCdelta kinase activity in wild-type alpha-synuclein over-expressing cells in response to MPP+ treatment. Wild-type alpha-synuclein over-expression also rescued mesencephalic dopaminergic neuronal cells from MPP+-induced apoptotic cell death, while alpha-synucleinA53T exacerbated the MPP+-induced DNA fragmentation. Furthermore, co-immunoprecipitation studies revealed that alpha-synuclein interacts with the pro-apoptotic proteins PKCdelta and BAD, but not with the anti-apoptotic protein Bcl-2 following MPP+ treatment. We also observed that the interaction between PKCdelta and alpha-synuclein does not involve direct phosphorylation. Together, our results demonstrate that wild-type alpha-synuclein interacts with the pro-apoptotic molecules BAD and PKCdelta to protect dopaminergic neuronal cells against neurotoxic insults.
Parkinson's Disorder Research Laboratory, Department of Biomedical Sciences, 2062, Veterinary Medicine Building, Iowa Sate University, Ames, IA 50011, USA.
Siddharth
S
Kaul
Vellareddy
V
Anantharam
Arthi
A
Kanthasamy
Anumantha G
AG
Kanthasamy
D015655:1-Methyl-4-phenylpyridinium / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D004298:Dopamine / Q000378:metabolism; D004789:Enzyme Activation; D006540:Herbicides / Q000494:pharmacology; D006801:Humans; D009474:Neurons / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
D006540:Herbicides; D017382:Reactive Oxygen Species; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine