title: FOXO3 determines the accumulation of α-synuclein and controls the fate of dopaminergic neurons in the substantia nigra.
abstract: Parkinson's disease (PD) is characterized by the selective degeneration of neuronal populations presumably due to pathogenic interactions between aging and predisposing factors such as increased levels of α-synuclein. Here, we genetically modulate the activity of the transcription factor Forkhead box protein O3 (FOXO3) in adult nigral dopaminergic neurons using viral vectors and explore how this determinant of longevity impacts on neuronal fate in normal and diseased conditions. We find that dopaminergic neurons are particularly vulnerable to changes in FOXO3 activity in the substantia nigra. While constitutive activation has proapoptotic effects leading to neuronal loss, inhibition of FOXO-mediated transcription by a dominant-negative competitor causes oxidative damage and is detrimental at high vector dose. To address the role of FOXO3 in PD, we modulate its activity in dopaminergic neurons overexpressing human α-synuclein. In this pathogenic condition, we find that FOXO inhibition has protective effects, suggesting that this transcription factor ultimately contributes to neuronal cell death. Nevertheless, mild FOXO3 activity also protects nigral neurons against the accumulation of human α-synuclein, albeit to a lesser extent. FOXO3 reduces the amount of α-synuclein present in the soluble protein fraction and promotes the coalescence of dense proteinase K-resistant aggregates, with an accumulation of autophagic vacuoles containing lipofuscin. Consistent with these in vivo observations, we find that FOXO3 controls autophagic flux in neuronal cells. Altogether, these results point to FOXO3 as an important determinant of neuronal survival in the substantia nigra, which may oppose α-synuclein accumulation and proteotoxicity.
authors.affiliation: Brain Mind Institute, Neurodegenerative Studies Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Emilda
authors.initials: E
authors.lastname: Pino
authors.forename: Ryoji
authors.initials: R
authors.lastname: Amamoto
authors.forename: Lu
authors.initials: L
authors.lastname: Zheng
authors.forename: Matthias
authors.initials: M
authors.lastname: Cacquevel
authors.forename: Juan-Carlos
authors.initials: JC
authors.lastname: Sarria
authors.forename: Graham W
authors.initials: GW
authors.lastname: Knott
authors.forename: Bernard L
authors.initials: BL
authors.lastname: Schneider
mesh_terms: D000818:Animals; D016923:Cell Death; D004249:DNA Damage; D000229:Dependovirus / Q000235:genetics*; D004195:Disease Models, Animal; D059290:Dopaminergic Neurons / Q000378:metabolism* / Q000473:pathology; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D006801:Humans; D010084:Oxidation-Reduction; D051381:Rats; D013378:Substantia Nigra / Q000378:metabolism* / Q000473:pathology; D051844:alpha-Synuclein / Q000378:metabolism*
chemical_list: C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D051844:alpha-Synuclein