Infoscience

Journal article

Induction of de novo α-synuclein fibrillization in a neuronal model for Parkinson's disease

Fares, Mohamed-Bilal; Maco, Bohumil; Oueslati, Abid; Rockenstein, Edward; Ninkina, Natalia; Buchman, Vladimir L; Masliah, Eliezer; Lashuel, Hilal A
  • Published in: Proceedings of the National Academy of Sciences of the United States of America (ISSN: 1091-6490), vol. 113, num. 7, p. E912-21
  • Washington: Natl Acad Sciences, 2016

Lewy bodies (LBs) are intraneuronal inclusions consisting primarily of fibrillized human α-synuclein (hα-Syn) protein, which represent the major pathological hallmark of Parkinson's disease (PD). Although doubling hα-Syn expression provokes LB pathology in humans, hα-Syn overexpression does not trigger the formation of fibrillar LB-like inclusions in mice. We hypothesized that interactions between exogenous hα-Syn and endogenous mouse synuclein homologs could be attenuating hα-Syn fibrillization in mice, and therefore, we systematically assessed hα-Syn aggregation propensity in neurons derived from α-Syn-KO, β-Syn-KO, γ-Syn-KO, and triple-KO mice lacking expression of all three synuclein homologs. Herein, we show that hα-Syn forms hyperphosphorylated (at S129) and ubiquitin-positive LB-like inclusions in primary neurons of α-Syn-KO, β-Syn-KO, and triple-KO mice, as well as in transgenic α-Syn-KO mouse brains in vivo. Importantly, correlative light and electron microscopy, immunogold labeling, and thioflavin-S binding established their fibrillar ultrastructure, and fluorescence recovery after photobleaching/photoconversion experiments showed that these inclusions grow in size and incorporate soluble proteins. We further investigated whether the presence of homologous α-Syn species would interfere with the seeding and spreading of α-Syn pathology. Our results are in line with increasing evidence demonstrating that the spreading of α-Syn pathology is most prominent when the injected preformed fibrils and host-expressed α-Syn monomers are from the same species. These findings provide insights that will help advance the development of neuronal and in vivo models for understanding mechanisms underlying hα-Syn intraneuronal fibrillization and its contribution to PD pathogenesis, and for screening pharmacologic and genetic modulators of α-Syn fibrillization in neurons.

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