The process of Lewy body formation, rather than simply α-synuclein fibrillization, is one of the major drivers of neurodegeneration

Abstract

Parkinson’s disease (PD) is characterized by the accumulation of misfolded and aggregated α-synuclein (α-syn) into intraneuronal inclusions named Lewy bodies (LBs). Although it is widely believed that α-syn plays a central role in the pathogenesis of PD, the processes that govern α-syn fibrillization and LB formation remain poorly understood. In this work, we sought to dissect the spatiotemporal events involved in the biogenesis of the LBs at the genetic, molecular, biochemical, structural, and cellular levels. Toward this goal, we further developed a seeding-based model of α-syn fibrillization to generate a neuronal model that reproduces the key events leading to LB formation, including seeding, fibrillization, and the formation of inclusions that recapitulate many of the biochemical, structural, and organizational features of bona fide LBs. Using an integrative omics, biochemical and imaging approach, we dissected the molecular events associated with the different stages of LB formation and their contribution to neuronal dysfunction and degeneration. In addition, we demonstrate that LB formation involves a complex interplay between α-syn fibrillization, posttranslational modifications, and interactions between α-syn aggregates and membranous organelles, including mitochondria, the autophagosome, and endolysosome. Finally, we show that the process of LB formation, rather than simply fibril formation, is one of the major drivers of neurodegeneration through disruption of cellular functions and inducing mitochondria damage and deficits, and synaptic dysfunctions. We believe that this model represents a powerful platform to further investigate the mechanisms of LB formation and clearance and to screen and evaluate therapeutics targeting α-syn aggregation and LB formation.

Pronounced α-synuclein pathology in a seeding-based mouse model is not sufficient to induce mitochondrial respiration deficits in the striatum and amygdala

“…Conversely, by immunostaining pS129 α-synuclein was readily detected. This could mean that pS129-positive α-synuclein pathology precedes the formation of insoluble aggregates, which is line with our recently presented study on the successive maturation of pS129 α-synuclein-positive aggregates into Lewy body like structures (Mahul-Mellier et al, 2020).…”

“…In primary hippocampal neurons we furthermore detected strong colocalization of pS129 with mitochondrial markers (Fig. 2C and (Mahul-Mellier et al, 2020)), which also was the case for neurons in the amygdala 60 dpi (Fig. 2D), which contained proteinase K resistant α-synuclein aggregations (Fig.…”

“…Primary hippocampal neurons were prepared from P0-2 pups of C57BL/6JRccHsd mice (Harlan) and imaged as described before (Mahul-Mellier et al, 2020). Briefly, hippocampi were dissescted in Hank’s Balanced Salt Solution (HBSS) and digested by papain (20U/mL, Sigma-Aldrich) for 30 min at 37 ◻C.…”

“…Mitochondrial dysfunction, in particular electron transport chain deficiencies, has also been implicated in PD pathogenesis (Langston et al, 1983; Schapira et al, 1989) and is thought to play important roles in both neurodegeneration and α-synuclein pathology (Hsu et al, 2000). Aggregated forms of α-synuclein has been shown to interfere with the regulation of mitochondrial import (Di Maio et al, 2016), mitochondrial membrane potential, reactive oxygen species (ROS)-generation and morphology (Tapias et al, 2017; Grassi et al, 2018) and oxidative phosphorylation (Ludtmann et al, 2016; Ludtmann et al, 2018) (Devi et al, 2008; Mahul-Mellier et al, 2020). However, whether α-synuclein pathology in the brain is sufficient to precipitate mitochondrial dysfunction is not known.…”

Tuning Hsp104 specificity to selectively detoxify α-synuclein

“…We suggest Hsp104 K358D:Y257T may partially remodel α-syn inclusions into less toxic structures. Hsp104 K358D:Y257T could extract essential proteins trapped in α-syn foci or mitigate toxic interactions between α-syn and intracellular vesicles or organelles Mahul-Mellier et al, 2020;Shahmoradian et al, 2019;Soper et al, 2008).…”