Alpha-synuclein aggregation involves a bafilomycin A₁-sensitive autophagy pathway

Abstract

Synucleinopathies like Parkinson disease and dementia with Lewy bodies (DLB) are characterized by α-synuclein aggregates within neurons (Lewy bodies) and their processes (Lewy neurites). Whereas α-synuclein has been genetically linked to the disease process, the pathological relevance of α-synuclein aggregates is still debated. Impaired degradation is considered to result in aggregation of α-synuclein. In addition to the ubiquitin-proteasome degradation, the autophagy-lysosomal pathway (ALP) is involved in intracellular degradation processes for α-synuclein. Here, we asked if modulation of ALP affects α-synuclein aggregation and toxicity. We have identified an induction of the ALP markers LAMP-2A and LC3-II in human brain tissue from DLB patients, in a transgenic mouse model of synucleinopathy, and in a cell culture model for α-synuclein aggregation. ALP inhibition using bafilomycin A 1 (BafA1) significantly potentiates toxicity of aggregated α-synuclein species in transgenic mice and in cell culture. Surprisingly, increased toxicity is paralleled by reduced aggregation in both in vivo and in vitro models. The dichotomy of effects on aggregating and nonaggregating species of α-synuclein was specifically sensitive to BafA1 and could not be reproduced by other ALP inhibitors. The present study expands on the accumulating evidence regarding the function of ALP for α-synuclein degradation by isolating an aggregation specific, BafA1-sensitive, ALP-related pathway. Our data also suggest that protein aggregation may represent a detoxifying event rather than being causal for cellular toxicity.

GBA deficiency promotes SNCA/α-synuclein accumulation through autophagic inhibition by inactivated PPP2A

“…34 Additionally, expression of regulatory components of the autophagy-lysosomal pathway is altered in the temporal cortex of LBD patients. 35 In this study, a downregulation of macroautophagy markers such as BECN1 and LC3 was observed in GBA-deficient neuroblastoma cells and cortical neurons and in the striatum (Figs. 2, 5 and 9).…”

Number and Brightness analysis of alpha-synuclein oligomerization and the associated mitochondrial morphology alterations in live cells

“…Dopamine was freshly prepared and transfected cells were treated for 3 hours with 100 µM dopamine. As reported by Klucken et al (2012) [28], cells were treated overnight after transfection with 200 nM bafilomycin A 1.…”

The neuropathology of multiple system atrophy and its therapeutic implications

“…Given the high levels and widespread distribution of α-syn aggregates in MSA, it is possible that both propagation and oligodendroglial α-syn expression might be occurring simultaneously. Supporting the possibility of propagation, several studies have shown that α-syn aggregates can transmit from neuron to neuron (Desplats et al, 2009; Lee et al, 2012b), neuron to astroglial and oligodendroglial cells (Lee et al, 2010; Reyes et al, 2014), and oligodendroglial to astroglial cells (Valera et al, 2014), leading to neuronal dysfunction, apoptosis and neuroin-flammation (Desplats et al, 2009; Klucken et al, 2012; Lee et al, 2010; Valera et al, 2014; Volpicelli-Daley et al, 2011). Moreover, recent studies have shown that injection of homogenates from MSA brains propagate α-syn pathology in a prion-like fashion in the murine brain (Prusiner et al, 2015; Watts et al, 2013).…”

“…autophagy, unfolded protein response, proteolysis) might play a role in the process of α-syn aggregation, release and subsequent accumulation of α-syn pathological species in donor and acceptor cells (Klucken et al, 2012; Lee et al, 2013) (Fig. 1).…”