title: Authentically phosphorylated α-synuclein at Ser129 accelerates neurodegeneration in a rat model of familial Parkinson's disease.
abstract: Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra (SN) and the appearance of fibrillar aggregates of insoluble α-synuclein (α-syn) called Lewy bodies (LBs). Approximately 90% of α-syn deposited in LBs is phosphorylated at serine 129 (Ser129). In contrast, only 4% of total α-syn is phosphorylated in normal brain, suggesting that accumulation of Ser129-phosphorylated α-syn is involved in the pathogenesis of PD. However, the role of Ser129 phosphorylation in α-syn neurotoxicity remains unclear. In this study, we coexpressed familial PD-linked A53T α-syn and G-protein-coupled receptor kinase 6 (GRK6) in the rat SN pars compacta using recombinant adeno-associated virus 2. Coexpression of these proteins yielded abundant Ser129-phosphorylated α-syn and significantly exacerbated degeneration of dopaminergic neurons when compared with coexpression of A53T α-syn and GFP. Immunohistochemical analysis revealed that Ser129-phosphorylated α-syn was preferentially distributed to swollen neurites. However, biochemical analysis showed that the increased expression of Ser129-phosphorylated α-syn did not promote accumulation of detergent-insoluble α-syn. Coexpression of catalytically inactive K215R mutant GRK6 failed to accelerate A53T α-syn-induced degeneration. Furthermore, introducing a phosphorylation-incompetent mutation, S129A, into A53T α-syn did not alter the pace of degeneration, even when GRK6 was coexpressed. Our study demonstrates that authentically Ser129-phosphorylated α-syn accelerates A53T α-syn neurotoxicity without the formation of detergent-insoluble α-syn, and suggests that the degenerative process could be constrained by inhibiting the kinase that phosphorylates α-syn at Ser129.
authors.affiliation: Department of Neurology, Hematology, Metabolism, Endocrinology and Diabetology, Yamagata University Faculty of Medicine, Yamagata 990-9585, Japan.
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Sato
authors.forename: Shigeki
authors.initials: S
authors.lastname: Arawaka
authors.forename: Susumu
authors.initials: S
authors.lastname: Hara
authors.forename: Shingo
authors.initials: S
authors.lastname: Fukushima
authors.forename: Kaori
authors.initials: K
authors.lastname: Koga
authors.forename: Shingo
authors.initials: S
authors.lastname: Koyama
authors.forename: Takeo
authors.initials: T
authors.lastname: Kato
mesh_terms: D000818:Animals; D002452:Cell Count; D002461:Cell Line, Transformed; D004195:Disease Models, Animal; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism; D051959:ELAV Proteins / Q000378:metabolism; D054768:G-Protein-Coupled Receptor Kinases / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics; D005822:Genetic Vectors / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009154:Mutation / Q000235:genetics; D019636:Neurodegenerative Diseases / Q000209:etiology* / Q000473:pathology; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D010300:Parkinson Disease / Q000150:complications* / Q000235:genetics; D010766:Phosphorylation / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D012694:Serine / Q000378:metabolism*; D013378:Substantia Nigra / Q000378:metabolism / Q000473:pathology; D014161:Transduction, Genetic / Q000379:methods; D014162:Transfection; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D051844:alpha-Synuclein / Q000235:genetics / Q000378:metabolism*
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D051959:ELAV Proteins; D051844:alpha-Synuclein; D049452:Green Fluorescent Proteins; D012694:Serine; D014446:Tyrosine 3-Monooxygenase; D054768:G-Protein-Coupled Receptor Kinases; C089176:G-protein-coupled receptor kinase 6
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