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Alpha-synuclein S129 phosphorylation mutants do not alter nigrostriatal toxicity in a rat model of Parkinson disease.

ABSTRACT: Lewy bodies are found in Parkinson disease and related disorders and are extensively phosphorylated at Ser-129 (S129), but whether S129 phosphorylation mediates alpha-synuclein aggregation and neurotoxicity has been controversial. We used recombinant adeno-associated virus to overexpress alpha-synuclein in the rat nigrostriatal system. Rats were injected with recombinant adeno-associated virus 2/8 expressing either human wild-type (wt) or mutant alpha-synuclein with S129 replaced by alanine (S129A) or aspartate (S129D). Contralateral substantia nigra injections containing empty vector served as controls. Both wt and S129 mutants resulted in significant dopaminergic cell loss in the recipients by 6 weeks, but there were only small decreases in nigrostriatal terminal density and tyrosine hydroxylase expression. There were no significant differences in dopaminergic cell loss, nigrostriatal terminal density, or tyrosine hydroxylase expression among the wt and S129 mutants. Furthermore, we did not observe any differences in alpha-synuclein aggregate formation or distribution among wt and either S129 mutant. These findings contrast with those from previous studies and suggest that injections of both S129 phosphorylation mutants result in dopaminergic neurotoxicity similar to wt injections. Further study is needed to clarify the effects of these S129 mutants and alpha-synuclein phosphorylation in mammalian systems.

SUBMITTER: McFarland NR

PROVIDER: S-EPMC2753269 | biostudies-literature | 2009 May

REPOSITORIES: biostudies-literature

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Alpha-synuclein S129 phosphorylation mutants do not alter nigrostriatal toxicity in a rat model of Parkinson disease.

McFarland Nikolaus R NR Fan Zhanyun Z Xu Kui K Schwarzschild Michael A MA Feany Mel B MB Hyman Bradley T BT McLean Pamela J PJ

Journal of neuropathology and experimental neurology 20090501 5

Lewy bodies are found in Parkinson disease and related disorders and are extensively phosphorylated at Ser-129 (S129), but whether S129 phosphorylation mediates alpha-synuclein aggregation and neurotoxicity has been controversial. We used recombinant adeno-associated virus to overexpress alpha-synuclein in the rat nigrostriatal system. Rats were injected with recombinant adeno-associated virus 2/8 expressing either human wild-type (wt) or mutant alpha-synuclein with S129 replaced by alanine (S12 ...[more]

PMID: 19525899

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Project description:The aggregation of α-synuclein (α-syn) is a major factor behind the onset of Parkinson's disease (PD). Sublocalization of this protein may be relevant for the formation of multimeric α-syn oligomeric configurations, insoluble aggregates that form Lewy bodies in PD brains. Processing of this protein aggregation is regulated by associations with distinct lipid classes. For instance, instability of lipid raft (LR) microdomains, membrane regions with a particular lipid composition, is an early event in the development of PD. However, the relevance of membrane microdomains in the regulation and trafficking of the distinct α-syn configurations associated with PD remains unexplored. In this study, using 6- and 14-month-old healthy and MPTP-treated animals as a model of PD, we have investigated the putative molecular alterations of raft membrane microstructures, and their impact on α-syn dynamics and conformation. A comparison of lipid analyses of LR microstructures and non-raft (NR) fractions showed alterations in gangliosides, cholesterol, polyunsaturated fatty acids (PUFA) and phospholipids in the midbrain and cortex of aged and MPTP-treated mice. In particular, the increase of PUFA and phosphatidylserine (PS) during aging correlated with α-syn multimeric formation in NR. In these aggregates, α-syn was phosphorylated in pSer129, the most abundant post-transductional modification of α-syn promoting toxic aggregation. Interestingly, similar variations in PUFA and PS content correlating with α-syn insoluble accumulation were also detected in membrane microstructures from the human cortex of incidental Parkinson Disease (iPD) and PD, as compared to healthy controls. Furthermore, structural changes in membrane lipid microenvironments may induce rearrangements in raft-interacting proteins involved in other neuropathologies. Therefore, we also investigated the dynamic of other protein markers involved in cognition and memory impairment such as metabotropic glutamate receptor 5 (mGluR5), ionotropic NMDA receptor (NMDAR2B), prion protein (PrPc) and amyloid precursor protein (APP), whose activity depends on membrane lipid organization. We observed a decline of these protein markers in LR fractions with the progression of aging and pathology. Overall, our findings demonstrate that lipid alterations in membranous compartments promoted by brain aging and PD-like injury may have an effect on α-syn aggregation and segregation in abnormal multimeric structures.

Project description:α-Synuclein (α-syn) is a 140-amino acid protein that plays a central role in the pathogenesis of Parkinson's disease (PD) and other synucleinopathies. However, the molecular determinants that are responsible for triggering and/or propagating α-syn aggregation and toxicity remain poorly understood. Several studies have suggested that there are direct interactions between different metals and α-syn, but the role of metal ions and α-syn in the pathogenesis of PD is not firmly established. Interestingly, the majority of disease-associated post-translational modifications (PTMs) (e.g., truncation, phosphorylation, and nitration) of α-syn occur at residues within the C-terminal region (Y125, S129, Y133, and Y136) and in very close proximity to the putative metal binding sites. Therefore, we hypothesized that phosphorylation within this domain could influence the α-syn-metal interactions. In this paper, we sought to map the interactions between the di- and trivalent cations, Cu(II), Pb(II), Fe(II), and Fe(III), and the C-terminal region of α-syn encompassing residues 107-140 and to determine how phosphorylation at S129 or Y125 alters the specificity and binding affinity of metals using electrospray ionization-mass spectrometry (ESI-MS) and fluorescence spectroscopy. We demonstrate that D115-M116 and P128-S129 act as additional Cu(II) binding sites and show for the first time that the residues P128-S129 and D119 are also involved in Pb(II) and Fe(II) coordination, although D119 is not essential for binding to Fe(II) and Pb(II). Furthermore, we demonstrate that phosphorylation at either Y125 or S129 increases the binding affinity of Cu(II), Pb(II), and Fe(II), but not Fe(III). Additionally, we also show that phosphorylations at these residues lead to a shift in the binding sites of metal ions from the N-terminus to the C-teminus. Together, our findings provide critical insight into and expand our understanding of the molecular and structural bases underlying the interactions between α-syn and metal ions, including the identification of novel metal binding sites, and highlight the potential importance of cross-talk between post-translational modifications and metal ion binding in modulating α-syn functional and aggregation properties that are regulated by its C-terminal domain.

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Alpha-synuclein S129 phosphorylation mutants do not alter nigrostriatal toxicity in a rat model of Parkinson disease.

Publications

Alpha-synuclein S129 phosphorylation mutants do not alter nigrostriatal toxicity in a rat model of Parkinson disease.

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