Exploring the Structural Diversity in Inhibitors of ?-Synuclein Amyloidogenic Folding, Aggregation, and Neurotoxicity.

ABSTRACT: Aggregation of ?-Synuclein (?S) protein to amyloid fibrils is a neuropathological hallmark of Parkinson's disease (PD). Growing evidence suggests that extracellular ?S aggregation plays a pivotal role in neurodegeneration found in PD in addition to the intracellular ?S aggregates in Lewy bodies (LB). Here, we identified and compared a diverse set of molecules capable of mitigating protein aggregation and exogenous toxicity of ?SA53T, a more aggregation-prone ?S mutant found in familial PD. For the first time, we investigated the ?S anti-amyloid activity of semi-synthetic flavonoid 2', 3', 4' trihydroxyflavone or 2-D08, which was compared with natural flavones myricetin and transilitin, as well as such structurally diverse polyphenols as honokiol and punicalagin. Additionally, two novel synthetic compounds with a dibenzyl imidazolidine scaffold, Compound 1 and Compound 2, were also investigated as they exhibited favorable binding with ?SA53T. All seven compounds inhibited ?SA53T aggregation as demonstrated by Thioflavin T fluorescence assays, with modified fibril morphology observed by transmission electron microscopy. Ion mobility-mass spectrometry (IM-MS) was used to monitor the structural conversion of native ?SA53T into amyloidogenic conformations and all seven compounds preserved the native unfolded conformations of ?SA53T following 48 h incubation. The presence of each test compound in a 1:2 molar ratio was also shown to inhibit the neurotoxicity of preincubated ?SA53T using phaeochromocytoma (PC12) cell viability assays. Among the seven tested compounds 2-D08, honokiol, and the synthetic Compound 2 demonstrated the highest inhibition of aggregation, coupled with neuroprotection from preincubated ?SA53T in vitro. Molecular docking predicted that all compounds bound near the lysine-rich region of the N-terminus of ?SA53T, where the flavonoids and honokiol predominantly interacted with Lys 23. Overall, these findings highlight that (i) restricted vicinal trihydroxylation in the flavone B-ring is more effective in stabilizing the native ?S conformations, thus blocking amyloidogenic aggregation, than dihydroxylation aggregation in both A and B-ring, and (ii) honokiol, punicalagin, and the synthetic imidazolidine Compound 2 also inhibit ?S amyloidogenic aggregation by stabilizing its native conformations. This diverse set of molecules acting on a singular pathological target with predicted binding to ?SA53T in the folding-prone N-terminal region may contribute toward novel drug-design for PD.

SUBMITTER: Das S 

PROVIDER: S-EPMC5983024 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature