The mode of α-synuclein binding to membranes depends on lipid composition and lipid to protein ratio

Abstract

a b s t r a c tInteractions of the presynaptic protein a-synuclein with membranes are involved in its physiological action as well as in the pathological misfolding and aggregation related to Parkinsons's disease.We studied the conformation and orientation of a-synuclein bound to model vesicular membranes using multiparametric response polarity-sensitive fluorescent probes together with CD and EPR measurements. At low lipid to a-synuclein ratio the protein binds membranes through its N-terminal domain. When lipids are in excess, the a-helical content and the role of the C-terminus in binding increase. Highly rigid membranes also induce a greater a-helical content and a lower polarity of the protein microenvironment.

α-Synuclein Senses Lipid Packing Defects and Induces Lateral Expansion of Lipids Leading to Membrane Remodeling

“…3A) suggests a lipid bilayer rearrangement that could cause a small underestimation of the protein/lipid mass ratio. However, irrespective of this effect, the molar ratio value is within the range of the stoichiometry described for a maximal ␣-helix folding to DOPC/DOPG (1:1) vesicles (46). It is worth noting that at low ␣-Syn concentrations, SUVs were observed to induce the highest binding during incubation that rapidly saturated to a mass ratio value of 0.076 Ϯ 0.003, equivalent to DOPC/DOPS (70:30) SUVs (Fig.…”

Effects of impaired membrane interactions on α-synuclein aggregation and neurotoxicity

“…The fractional population of molecules bound to the membrane in either mode (‘total bound population’) was determined from the mean attenuation of residues 3–9. Our rationale for this approach was that the N-terminal segment of aSyn has a higher membrane affinity compared to more C-terminal regions (Bartels et al, 2010; Drescher et al, 2008; Shvadchak et al, 2011b) and is lipid-bound in the case of both exposed and hidden conformers (Bodner et al, 2010). To calculate the fractional population of protein in the hidden state we determined the mean attenuation of residues 66–80, based on the fact that this segment of the central hydrophobic region contains residues that play a key role in aSyn self-assembly (Giasson et al, 2001), and consistent with a previous report (Bodner et al, 2010).…”

“…The aSyn region spanning residues 31–85 has been reported to have lower membrane affinity than the N-terminal segment spanning the first ~30 residues (Bartels et al, 2010; Drescher et al, 2008; Shvadchak et al, 2011b). Interactions involving residues 31–85 with the membrane only become significant after the crowding of neighboring aSyn molecules on the bilayer surface is relieved by the addition of excess lipid.…”

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

“…As shown in the B map in Figure 3D, αsyn oligomers localize in certain cell regions. Considering the ability of αsyn to bind to membranes characterized by different lipid compositions [57], a “scaffolding effect” may be envisioned, partially due to the localization of αsyn oligomers at the numerous membranous structures present in the cell cytoplasm and at the plasma membrane. This interpretation is supported by a model for αsyn aggregation where the early αsyn oligomers are formed not only in the cell cytoplasm but also at the membranes [32, 58], which can lead to calcium leakage [59] and to synaptic vesicles homeostasis disruption in neurons [60].…”