Effect of Pseudorepeat Rearrangement on α-Synuclein Misfolding, Vesicle Binding, and Micelle Binding

Abstract

The pathological and physiological hallmarks of the protein α-synuclein are its misfolding into cytotoxic aggregates and its binding to synaptic vesicles, respectively. Both events are mediated by seven 11-residue amphiphilic pseudorepeats and, most generally, involve a transition from intrinsically unstructured to structured conformations. Based upon α-synuclein interactions with aggregation-inhibiting small molecules, a α-synuclein variant termed SaS, wherein the first six pseudorepeats had been rearranged, was introduced. Here, the effects of this rearrangement upon misfolding, vesicle binding and micelle binding are examined in reference to α- and β-synuclein to study the sequence characteristics underlying these processes. Fibrillization correlates with the distinct clustering of residues with high β-sheet propensities, while vesicle affinities depend on the mode of pseudorepeat interchange and loss. In the presence of micelles, the pseudorepeat region of SaS adopts an essentially continuous helix, whereas α- and β-synuclein encounter a distinct helix break, indicating that a more homogeneous distribution of surfactant affinities in SaS prevented the formation of a helix break in the micelle-bound state. By demonstrating the importance of the distribution of β-sheet propensities and by revealing inhomogeneous aS surfactant affinities, the present study provides novel insight into two central themes of synuclein biology.

Biophysics of α-synuclein membrane interactions

“…Using a variety of techniques including fluorescence correlation spectroscopy (FCS) and CD spectroscopy, it has been shown that PE enhances α-syn membrane interaction [90] and that α-syn favors PA and PI over PS and PG [90–94]. In addition to vesicles containing anionic lipids, α-syn also can bind to lipid droplets [96] and SDS micelles [26, 97–99]. …”

Neuroprotective and Nootropic Drug Noopept Rescues α-Synuclein Amyloid Cytotoxicity

“…50 The weighted average of the 1 H and 15 N chemical shift difference (Δδ ave = (0.5[Δδ( 1 H) 2 + (0.2Δδ ( 15 N)) 2 ])1/2) and the ratio of peak intensities between the different experiments were derived and presented by using the software Grace (plasma-gate.weizmann.ac.il/Grace), together with the previously reported 1 H and 15 N chemical shift assignment for α-Syn. 51,52 ThT binding assay…”

Binding interactions of agents that alter α-synuclein aggregation

“…The greater density of β-branched residues in the adjacent sixth and seventh repeats is particularly important for fibril formation 24,25 . In studies of constructs with reordered repeats, it was observed that when the sixth and seventh repeats are separated by the insertion of other repeats mature fibril formation did not occur and β-structure formation was inhibited.…”