Selectivity of Lewy body protein interactions along the aggregation pathway of α-synuclein

Abstract

The aggregation of alpha-synuclein (α-SYN) follows a cascade of oligomeric, prefibrillar and fibrillar forms, culminating in the formation of Lewy Bodies (LB), the pathological hallmarks of Parkinson’s Disease. Although LB contain over 70 proteins, the potential for interactions along the aggregation pathway of α-SYN is unknown. Here we propose a map of interactions of 65 proteins against different species of α-SYN. We measured binding to monomeric α-SYN using AlphaScreen, a sensitive nano-bead luminescence assay for detection of protein interactions. To access oligomeric species, we used the pathological mutants of α-SYN (A30P, G51D and A53T) which form oligomers with distinct properties. Finally, we generated amyloid fibrils from recombinant α-SYN. Binding to oligomers and fibrils was measured by two-color coincidence detection (TCCD) on a single molecule spectroscopy setup. Overall, we demonstrate that LB components are recruited to specific steps in the aggregation of α-SYN, uncovering future targets to modulate aggregation in synucleinopathies.

Ultrastructural and biochemical classification of pathogenic tau, α-synuclein and TDP-43

“…It will be important to clarify whether the disease-specific fold is established at the point of initial fibrillar species formation or at some other point during the maturation process, both in order to elucidate the mechanism of the strain formation and to characterize the pathological transition from pre-tangles/pre-inclusions to fibrillar inclusions. Recently, comprehensive proteomic analysis has identified a number of proteins that interact with tau, α-syn and TDP-43 [ 99 , 123 , 181 , 292 ]. A similar approach would be useful to identify cell type-specific proteins that interact with pathogenic proteins and are involved in strain formation.…”

Protein interaction networks in neurodegenerative diseases: From physiological function to aggregation

“…As well, α-syn binds tau, and both proteins have a synergetic effect toward their polymerization into fibrils ( 144 , 145 ). In a recent study, in which PPIs of a subset of LB-localizing proteins were assessed using a combination of nanobead luminescence and two-color coincidence detection assays, tau was shown to bind more strongly to preformed α-syn fibrils rather than to monomeric and oligomeric α-syn ( 146 ). In addition to its association with the microtubular network, α-syn has also been found to associate with dopamine transporter 1 (DAT1) , and may thereby regulate dopamine neurotransmission by modulating DAT1 levels at the cell surface by tethering the transporter to microtubules ( 147 , 148 , 149 ).…”

“…This is the case with DnaJB1, Hsp70, and the Apg2 nucleotide exchange factor that convert cytotoxic fibrils to nontoxic monomeric α-syn in an ATP-dependent manner ( 160 ). Another molecular cochaperone, DnaJB6, has been shown to suppress the aggregation of seeded α-syn in cells and in animal models of PD ( 146 , 161 , 162 , 163 ). Different chaperone proteins can bind to different populations of misfolded α-syn.…”

“…Different chaperone proteins can bind to different populations of misfolded α-syn. Notably, while the small HSP αB-crystallin preferably binds to seeding oligomers, DnaJB6 interacts instead with assembled fibrils ( 146 ). Distinctly, recent work using in-cell nuclear magnetic resonance indicates that a majority of monomeric α-syn could be bound to chaperone proteins inside the cell ( 164 ).…”

Mitochondrial Function and Parkinson’s Disease: From the Perspective of the Electron Transport Chain

“…Cyt c has also been identified as one of the components of brainstem Lewy bodies ( Wakabayashi et al, 2007 ) and might play as a trigger in α-Syn aggregation ( Hashimoto et al, 1999 ). α-Syn fibrils rather than mutant oligomers or monomers specifically interact with cyt c according to an in vitro study ( Leitão et al, 2021 ). Whether similar aggregations could be replicated in vivo and whether post-translational modifications of cyt c as mentioned earlier have any effects on these moonlight functions are still unknown.…”