title: 6-Hydroxydopamine but not 1-methyl-4-phenylpyridinium abolishes alpha-synuclein anti-apoptotic phenotype by inhibiting its proteasomal degradation and by promoting its aggregation.
abstract: We established previously that alpha-synuclein displayed a protective anti-apoptotic phenotype in neurons, mainly by down-regulating p53-dependent caspase-3 activation (Alves da Costa, C., Ancolio, K., and Checler, F. (2000) J. Biol. Chem. 275, 24065-24069; Alves da Costa, C., Paitel, E., Vincent, B., and Checler, F. (2002) J. Biol. Chem. 277, 50980-50984). This function was abolished by Parkinson disease-linked pathogenic mutations and by the dopaminergic toxin, 6-hydroxydopamine (6OH-DOPA) (Alves da Costa, C., Paitel, E., Vincent, B., and Checler, F. (2002) J. Biol. Chem. 277, 50980-50984). However, the mechanisms by which 6OH-DOPA interfered with alpha-synuclein function remained unclear. Here we showed that 6OH-DOPA prevents alpha-synuclein-mediated anti-apoptotic function by altering its degradation. Thus, 6OH-DOPA treatment of TSM1 neurons and SH-SY5Y neuroblastoma cells enhances endogenous alpha-synuclein-like immunoreactivity and inhibits the catabolism of endogenous and recombinant alpha-synucleins by purified 20 S proteasome. Furthermore, we demonstrated that 6OH-DOPA directly inhibits endogenous proteasomal activity in TSM1 and SH-SY5Y cells and also blocks purified proteasome activity in vitro. This inhibitory effect can be prevented by the anti-oxidant phenyl-N-butylnitrone. We also established that 6OH-DOPA triggers the aggregation of recombinant alpha-synuclein in vitro. Therefore, we conclude that 6OH-DOPA abolishes alpha-synuclein anti-apoptotic phenotype by inhibiting its proteasomal degradation, thereby increasing its intracellular concentration and potential propensity to aggregation, the latter phenomenon being directly exacerbated by 6OH-DOPA itself. Interestingly, 1-methyl-4-phenylpyridinium (MPP(+)), another toxin inducer of Parkinson disease-like pathology, does not affect alpha-synuclein protective function and fails to trigger aggregation of recombinant alpha-synuclein. Furthermore, MPP(+) does not alter cellular proteasomal activity, and only high concentrations of the toxin affect purified 20 S proteasome by a mechanism that remains insensitive to phenyl-N-butylnitrone. The drastically distinct effects of 6OH-DOPA and MPP(+) on alpha-synuclein function are discussed with respect to Parkinson disease pathology and animal models mimicking this pathology.
authors.affiliation: IPMC du CNRS, UMR6097, Equipe Labellisée FRM, 660 Route des Lucioles, 06560 Valbonne, France. acosta@ipmc.cnrs.fr
authors.forename: Cristine
authors.initials: C
authors.lastname: Alves da Costa
authors.forename: Julie
authors.initials: J
authors.lastname: Dunys
authors.forename: Frédéric
authors.initials: F
authors.lastname: Brau
authors.forename: Sherwin
authors.initials: S
authors.lastname: Wilk
authors.forename: Roberto
authors.initials: R
authors.lastname: Cappai
authors.forename: Frédéric
authors.initials: F
authors.lastname: Checler
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D004195:Disease Models, Animal; D006540:Herbicides / Q000378:metabolism*; D006801:Humans; D009447:Neuroblastoma / Q000473:pathology; D009474:Neurons / Q000502:physiology; D016627:Oxidopamine / Q000494:pharmacology*; D010300:Parkinson Disease / Q000503:physiopathology; D010641:Phenotype; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D051844:alpha-Synuclein / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D006540:Herbicides; D051844:alpha-Synuclein; D016627:Oxidopamine; D046988:Proteasome Endopeptidase Complex; D015655:1-Methyl-4-phenylpyridinium