engleski

Deciphering the role of alpha- synuclein in the nucleus: insights into the molecular basis of synucleiopathies

Alpha-synuclein (asyn), a common player in sporadic and familiar forms of Parkinson’s disease (PD), was fist named for its localization both in the nucleus and presynaptic terminals. The nuclear localization has been controversial, despite several episodic reports. Growing evidence suggests that oxidative stress and some familial asyn mutations enhance its nuclear localization and promote neurotoxicity, possibly due to altered interactions with histones and modulation of gene expression. In both mouse models and human PD patients, transcriptional alterations have been reported. Here, we investigated the effects of asyn in the nucleus in terms of its cell biology and gene expression. We started by comparing the gene expression patters of two clinically distinct co-horts of PD patients, characterized by either slow or fast disease progression. We identified 147 genes with differential expression patterns between the two groups (p<0.01). Validation by qPCR was performed for 5 selected genes in a subset of patients. We found different gene expression in genes whose function is linked to transcription regulation, ubiquitin-proteasome system, membrane trafficking and cytoskeleton dynamics. In parallel, to confirm the presence of asyn in the nucleus we performed in vitro studies, in cell culture models, and in mice. We verified that asyn is present in nuclear fractions from H4 cells overexpressing wild-type (wt) asyn and from the midbrain of transgenic A30P mice. Using immunohistochemistry we also demonstrated that asyn is present in the nucleus of cells from several brain regions during embryonic stages of development in mice and also, although to a lesser extent, in adult mice. To further explore the interaction between asyn and DNA and identify novel promoter binding sites, we performed NMRexperiments, genome-wide chromatin immunoprecipitation (ChIP)-sequencing and dualluciferase assays. Our preliminary NMR results corroborate the hypothesis that asyn interacts with DNA and acts as a transcriptional modulator. ChIP-sequencing data shows that wt asyn can bind to several promoter regions involved in CNS functioning and development, such as NEDD4, CDH4 and SLC4A5. We confirmed that wt a-Syn overexpression resulted in a 27% increase of SLC4A5 promoter activityin dual-luciferase reporter assays, . In conclusion, our results provide novel insight into the effects of asyn in the nucleus, where it promotes transcriptional dysregulation by direct binding to DNA. Ultimately, our studies may open novel avenuesfor therapeutic intervention and for the development of novel biomarkers for PD.

alpha-synuclein; synucleiopathies; Parkinson’s disease

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