Dataset Information

Bidirectional modulation of Alzheimer phenotype by alpha-synuclein in mice and primary neurons.

ABSTRACT: ?-Synuclein (?Syn) histopathology defines several neurodegenerative disorders, including Parkinson's disease, Lewy body dementia, and Alzheimer's disease (AD). However, the functional link between soluble ?Syn and disease etiology remains elusive, especially in AD. We, therefore, genetically targeted ?Syn in APP transgenic mice modeling AD and mouse primary neurons. Our results demonstrate bidirectional modulation of behavioral deficits and pathophysiology by ?Syn. Overexpression of human wild-type ?Syn in APP animals markedly reduced amyloid deposition but, counter-intuitively, exacerbated deficits in spatial memory. It also increased extracellular amyloid-? oligomers (A?Os), ?Syn oligomers, exacerbated tau conformational and phosphorylation variants associated with AD, and enhanced neuronal cell cycle re-entry (CCR), a frequent prelude to neuron death in AD. Conversely, ablation of the SNCA gene encoding for ?Syn in APP mice improved memory retention in spite of increased plaque burden. Reminiscent of the effect of MAPT ablation in APP mice, SNCA deletion prevented premature mortality. Moreover, the absence of ?Syn decreased extracellular A?Os, ameliorated CCR, and rescued postsynaptic marker deficits. In summary, this complementary, bidirectional genetic approach implicates ?Syn as an essential mediator of key phenotypes in AD and offers new functional insight into ?Syn pathophysiology.

SUBMITTER: Khan SS

PROVIDER: S-EPMC6329667 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Bidirectional modulation of Alzheimer phenotype by alpha-synuclein in mice and primary neurons.

Khan Shahzad S SS LaCroix Michael M Boyle Gabriel G Sherman Mathew A MA Brown Jennifer L JL Amar Fatou F Aldaco Jacqeline J Lee Michael K MK Bloom George S GS Lesné Sylvain E SE

Acta neuropathologica 20180711 4

α-Synuclein (αSyn) histopathology defines several neurodegenerative disorders, including Parkinson's disease, Lewy body dementia, and Alzheimer's disease (AD). However, the functional link between soluble αSyn and disease etiology remains elusive, especially in AD. We, therefore, genetically targeted αSyn in APP transgenic mice modeling AD and mouse primary neurons. Our results demonstrate bidirectional modulation of behavioral deficits and pathophysiology by αSyn. Overexpression of human wild-t ...[more]

PMID: 29995210

Similar Datasets

Project description:BACKGROUND: Alpha-synuclein is a presynaptic protein with a proposed role in neurotransmission and dopamine homeostasis. Abnormal accumulation of alpha-synuclein aggregates in dopaminergic neurons of the substantia nigra is diagnostic of sporadic Parkinson's disease, and mutations in the protein are linked to early onset forms of the disease. The folded conformation of the protein varies depending upon its environment and other factors that are poorly understood. When bound to phospholipid membranes, alpha-synuclein adopts a helical conformation that mediates specific interactions with other proteins. RESULTS: To investigate the role of the helical domain in transport and localization of alpha-synuclein, eGFP-tagged constructs were transfected into rat primary hippocampal neurons at 7 DIV. A series of constructs were analyzed in which each individual exon was deleted, for comparison to previous studies of lipid affinity and alpha-helix content. A53T and A30P substitutions, representing Parkinson's disease-associated variants, were analyzed as well. Single exon deletions within the lipid-binding N-terminal domain of alpha-synuclein (exons 2, 3, and 4) partially disrupted its presynaptic localization at 17-21 DIV, resulting in increased diffuse labeling of axons. Similar results were obtained for A30P, which exhibits decreased lipid binding, but not A53T. To examine whether differences in presynaptic enrichment were related to deficiencies in transport velocity, transport was visualized via live cell microscopy. Tagged alpha-synuclein migrated at a rate of 1.85 +/- 0.09 mum/s, consistent with previous reports, and single exon deletion mutants migrated at similar rates, as did A30P. Deletion of the entire N-terminal lipid-binding domain (Delta234GFP) did not significantly alter rates of particle movement, but decreased the number of moving particles. Only the A53TGFP mutant exhibited a significant decrease in transport velocity as compared to ASGFP. CONCLUSIONS: These results support the hypothesis that presynaptic localization involves a mechanism that requires helical conformation and lipid binding. Conversely, the rate of axonal transport is not determined by lipid affinity and is not sufficient to account for differences in presynaptic localization of alpha-synuclein-eGFP variants.

Project description:?-synuclein (?S) is a small protein that self-aggregates into ?-helical oligomer species and subsequently into larger insoluble amyloid fibrils that accumulate in intraneuronal inclusions during the development of Parkinson's disease. Toxicity of ?S oligomers and fibrils has been long debated and more recent data are suggesting that both species can induce neurodegeneration. However while most of these data are based on differences in structure between oligomer and aggregates, often preassembled in vitro, the in vivo situation might be more complex and subcellular locations where ?S species accumulate, rather than their conformation, might contribute to enhanced toxicity. In line with this observation, we have shown that ?S oligomers and aggregates are associated with the endoplasmic reticulum/microsomes (ER/M) membrane in vivo and how accumulation of soluble ?S oligomers at the ER/M level precedes neuronal degeneration in a mouse model of ?-synucleinopathies. In this paper we took a further step, investigating the biochemical and functional features of ?S species associated with the ER/M membrane. We found that by comparison with non-microsomal associated ?S (P10), the ER/M-associated ?S pool is a unique population of oligomers and aggregates with specific biochemical traits such as increased aggregation, N- and C-terminal truncations and phosphorylation at serine 129. Moreover, when administered to murine primary neurons, ER/M-associated ?S species isolated from diseased A53T human ?S transgenic mice induced neuronal changes in a time- and dose-dependent manner. In fact the addition of small amounts of ER/M-associated ?S species from diseased mice to primary cultures induced the formation of beads-like structures or strings of fibrous ?S aggregates along the neurites, occasionally covering the entire process or localizing at the soma level. By comparison treatment with P10 fractions from the same diseased mice resulted in the formation of scarce and small puncta only when administered at high amount. Moreover, increasing the amount of P100/M fractions obtained from diseased and, more surprisingly, from presymptomatic mice induced a significant level of neuronal death that was prevented when neurons were treated with ER/M fractions immunodepleted of ?S high molecular weight (HMW) species. These data provide the first evidence of the existence of two different populations of ?S HMW species in vivo, putting the spotlight on the association to ER/M membrane as a necessary step for the acquisition of ?S toxic features.

Project description:α-Synuclein is the major pathological component of synucleinopathies including Parkinson's disease and dementia with Lewy bodies. Recent studies have demonstrated that α-synuclein also plays important roles in the release of synaptic vesicles and synaptic membrane recycling in healthy neurons. However, the precise relationship between the pathogenicity and physiological functions of α-synuclein remains to be elucidated. To address this issue, we investigated the subcellular localization of α-synuclein in normal and pathological conditions using primary mouse hippocampal neuronal cultures. While some neurons expressed high levels of α-synuclein in presynaptic boutons and cell bodies, other neurons either did not or only very weakly expressed the protein. These α-synuclein-negative cells were identified as inhibitory neurons by immunostaining with specific antibodies against glutamic acid decarboxylase (GAD), parvalbumin, and somatostatin. In contrast, α-synuclein-positive synapses were colocalized with the excitatory synapse marker vesicular glutamate transporter-1. This expression profile of α-synuclein was conserved in the hippocampus in vivo. In addition, we found that while presynaptic α-synuclein colocalizes with synapsin, a marker of presynaptic vesicles, it is not essential for activity-dependent membrane recycling induced by high potassium treatment. Exogenous supply of preformed fibrils generated by recombinant α-synuclein was shown to promote the formation of Lewy body (LB) -like intracellular aggregates involving endogenous α-synuclein. GAD-positive neurons did not form LB-like aggregates following treatment with preformed fibrils, however, exogenous expression of human α-synuclein allowed intracellular aggregate formation in these cells. These results suggest the presence of a different mechanism for regulation of the expression of α-synuclein between excitatory and inhibitory neurons. Furthermore, α-synuclein expression levels may determine the efficiency of intracellular aggregate formation in different neuronal subtypes.

Dataset Information

Bidirectional modulation of Alzheimer phenotype by alpha-synuclein in mice and primary neurons.

Publications

Bidirectional modulation of Alzheimer phenotype by alpha-synuclein in mice and primary neurons.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets