Effect of Disease-Associated P123H and V70M Mutations on β-Synuclein Fibrillation

Abstract

Synucleinopathies are a class of neurodegenerative diseases, including Parkinson's disease (PD), Dementia with Lewy bodies (DLB), and Multiple System Atrophy (MSA). The common pathological hallmark of synucleinopathies is the filamentous α-synuclein (α-Syn) aggregates along with membrane components in cytoplasmic inclusions in the brain. β-Synuclein (β-Syn), an isoform of α-Syn, inhibits α-Syn aggregation and prevents its neurotoxicity, suggesting the neuroprotective nature of β-Syn. However, this notion changed with the discovery of diseaseassociated β-Syn mutations, V70M and P123H, in patients with DLB. It is still unclear how these missense mutations alter the structural and amyloidogenic properties of β-Syn, leading to neurodegeneration. Here, we characterized the biophysical properties and investigated the effect of mutations on β-Syn fibrillation under different conditions. V70M and P123H show high membrane binding affinity compared to wild-type β-Syn, suggesting their potential role in membrane interactions. β-Syn and its mutants do not aggregate under normal physiological conditions; however, the proteins undergo self-polymerization in a slightly acidic microenvironment and/or in the presence of an inducer, forming long unbranched amyloid fibrils similar to α-Syn. Strikingly, V70M and P123H mutants exhibit accelerated fibrillation compared to native β-Syn under these conditions. NMR study further revealed that these point mutations induce local perturbations at the site of mutation in β-Syn. Overall, our data provide insight into the biophysical properties of disease-associated β-Syn mutations and demonstrate that these mutants make the native protein more susceptible to aggregation in an altered microenvironment.

Synaptic vesicle binding of α-synuclein is modulated by β- and γ-synucleins

“…Previous in silico and in vitro studies have reported on certain aspects of membrane binding of the synucleins ( Bertoncini et al, 2007 ; Brown et al, 2016 ; Ducas and Rhoades, 2012 ; Middleton and Rhoades, 2010 ; Rao et al, 2009 ; Sharma et al, 2020 ; Sung and Eliezer, 2006 ). Yet, the three synucleins were never compared side by side in a systematic manner, and the in vivo relevance of the findings in the above studies remains unknown.…”

Structural and Functional Insights into α-Synuclein Fibril Polymorphism

“…The deleterious effects of these mutations have been shown by cell-and animalbased studies [179,180]. Our group recently showed that under normal physiological conditions, fibrilization and aggregation of β-Syn and its disease-associated mutations did not occur, but an altered microenvironment, such as a decrease in pH and/or presence of heparin, caused them to polymerize [181]. γ-Syn, which shares~55% sequence homology with α-Syn, was initially identified in breast cancer malignancies encoded by a breastcancer-specific gene, BCSG1 [182].…”

Coassembled Chitosan–Hyaluronic Acid Nanoparticles as a Theranostic Agent Targeting Alzheimer’s β-Amyloid

“…As illustrated in Figure b, CHG NPs showed visible fluorescence response after the interaction with α-syn fibrils; by contrast, insignificant fluorescence changes were detected in the presence of either Lys or hIAPP fibrils (Figure b). From a comparison of the properties of the above amyloid proteins, it is known that α-syn fibrils and Aβ aggregates are both negatively charged , while both Lys and hIAPP fibrils carry positive charges at physiological conditions (pH 7.4) . This implies that electrostatic interactions play a pivotal role in the recognition and fluorescence response behavior of CHG NPs, which were positively charged (Table S1).…”