α-Synuclein enhances histone H3 lysine-9 dimethylation and H3K9me2-dependent transcriptional responses

Abstract

α-Synuclein (αS) is a protein linked to Parkinson’s disease (PD) and related neurodegenerative disorders. It is mostly localized within synapses, but αS has also been suggested to play a role in the nucleus. We used transgenic Drosophila and inducible SH-SY5Y neuroblastoma cells to investigate the effects of αS on chromatin with a particular focus on histone modifications. Overexpression of αS in male flies as well as in retinoic acid pre-treated neuroblastoma cells led to an elevation of histone H3K9 methylations, mostly mono- (H3K9me1) and di- (H3K9me2). The transient increase of H3K9 methylation in αS-induced SH-SY5Y cells was preceded by mRNA induction of the euchromatic histone lysine N-methyltransferase 2 (EHMT2). EHMT2 and H3K9me2 can function within the REST complex. Chromatin immunoprecipitation (ChIP) analyses of selected candidate, REST regulated genes showed significantly increased H3K9me2 promoter occupancy of genes encoding the L1CAM cell adhesion molecule and the synaptosomal-associated protein SNAP25, whose reduced expression levels were confirmed by RT-qPCR in αS induced cells. Treatment with EHMT inhibitor UNC0638 restored the mRNA levels of L1CAM and SNAP25. Thus, αS overexpression enhances H3K9 methylations via ΕΗΜΤ2 resulting in elevated H3K9me2 at the SNAP25 promoter, possibly affecting SNARE complex assembly and hence synaptic vesicle fusion events regulated by αS.

Alpha-Synuclein Physiology and Pathology: A Perspective on Cellular Structures and Organelles

“…Alpha-synuclein interacts with epigenetic "writers." It has been observed that in transgenic flies expressing hWT α-syn ubiquitously under control of the daG32-GAL4 promoter, an increase in histone-H3 lysine-9 (H3K9) methylation was present (Sugeno et al, 2016). Furthermore, by overexpressing hWT α-syn in rat B103 neuronal cells, Desplats et al (2011) found that α-syn can retain DNA methyltransferase 1 in the cytoplasm of neuronal cells compromising DNA methylation (Figure 3).…”

“…Transgenic mice expressing hWT α-syn under the Thy-1 promoter, rat B103 neuroblastoma cells and 293T human hepatocarcinoma cells (Desplats et al, 2011) α-syn retains DNA methyltransferase 1 in the cytoplasm Impaired histone deacetylation SH-SY5Y cells with hWT α-syn expression (Kontopoulos et al, 2006) α-syn restricts and maintains histone deacetylases in the cytoplasm Alteration in histone methylation pattern D. melanogaster expressing hWT α-syn ubiquitously under control of a daG32-GAL4 driver and dopaminergic differentiated SH-SY5Y cells with inducible hWT α-syn expression (Sugeno et al, 2016) α-syn selectively enhances H3K9 mono-and dimethylation by interacting with H3K9me1/2 methyltransferase…”

Membrane Trafficking Illuminates a Path to Parkinson’s Disease

“…The first αSYN was identified in 1988 from the electric organ of Torpedo californica as a protein that localized to the presynaptic nerve terminals and nuclei of neurons (Maroteaux et al 1988;Schell et al 2009;Sugeno et al 2016). Human αSYN is a relatively small protein, consisting of 140 amino acids, and has a predicted molecular mass of 14 kDa.…”

EHMT1/GLP; Biochemical Function and Association with Brain Disorders

“…α-Synuclein, a protein associated with Parkinson's disease and other neurodegenerative disorders, was found to increase the levels of H3K9me2, and overexpression of the protein would lead to an increasingly restrictive chromatin in Parkinson's disease [57]. H3K9me2 has also been associated with Huntington's disease (HD), where the marker is shown to be in the striatum of HD patients [58].…”