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.
Kaul
Siddharth
S
Parkinson's Disorder Research Laboratory, Department of Biomedical Sciences, 2062, Veterinary Medicine Building, Iowa Sate University, Ames, IA 50011, USA.
Anantharam
Vellareddy
V
Kanthasamy
Arthi
A
Kanthasamy
Anumantha G
AG
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