alpha-synuclein and 1-2-dioleoylphosphatidylserine

The neuronal protein α-synuclein, linked to Parkinson's disease, binds to negatively charged vesicles adopting a partial α-helix structure, but helix arrangement at the vesicle surface is not fully understood. Using linear dichroism spectroscopy (LD), we study the interaction of monomeric α-synuclein with large unilamellar vesicles of 1,2-dioleoyl-

Topics: alpha-Synuclein; Amino Acid Sequence; Phosphatidylglycerols; Phosphatidylserines; Protein Binding; Protein Conformation, alpha-Helical; Unilamellar Liposomes

Complexin-1 (Cpx) and α-synuclein (α-Syn) are involved in neurotransmitter release through an interaction with synaptic vesicles (SVs). Recent studies demonstrated that Cpx and α-Syn preferentially associate with highly curved membranes, like SVs, to correctly position them for fusion. Here, based on recent experimental results, to further propose a possible explanation for this mechanism, we performed in silico simulations probing interactions between Cpx or α-Syn and membranes of varying curvature. We found that the preferential association is attributed to smaller, curved membranes containing more packing defects that expose hydrophobic acyl tails, which may favorably interact with hydrophobic residues of Cpx and α-Syn. The number of membrane defects is proportional to the curvature and the size can be regulated by cholesterol.

Topics: Adaptor Proteins, Vesicular Transport; alpha-Synuclein; Cholesterol; Hydrogen Bonding; Lipid Bilayers; Molecular Dynamics Simulation; Nerve Tissue Proteins; Phosphatidylcholines; Phosphatidylethanolamines; Phosphatidylserines; Protein Binding; Synaptic Vesicles

Parkinson's disease (PD), closely associated with the misfolding and aggregation of the neuronal protein α-synuclein (A-Syn), is a neurodegenerative disorder with no cure to date. Here, we show that the commercially available, inexpensive, aminoglycoside antibiotic kanamycin effectively inhibits both lipid-induced and solution-phase aggregation of A-Syn in vitro, pointing towards the prospective repurposing of kanamycin as a potential anti-PD drug.

Topics: alpha-Synuclein; Anti-Bacterial Agents; Cell Line, Tumor; Humans; Kanamycin; Phosphatidylcholines; Phosphatidylethanolamines; Phosphatidylserines; Protein Binding; Protein Conformation; Protein Multimerization; Unilamellar Liposomes

Amyloid fibrillation causes serious neurodegenerative diseases and amyloidosis; however, the detailed mechanisms by which the structural states of precursor proteins in a lipid membrane-associated environment contribute to amyloidogenesis still remains to be elucidated. We examined the relationship between structural states of intrinsically-disordered wild-type and mutant α-synuclein (αSN) and amyloidogenesis on two-types of model membranes. Highly-unstructured wild-type αSN (αSN

Topics: alpha-Synuclein; Amyloid; Dose-Response Relationship, Drug; Dynamic Light Scattering; Humans; Membrane Lipids; Models, Chemical; Nuclear Magnetic Resonance, Biomolecular; Phosphatidylcholines; Phosphatidylethanolamines; Phosphatidylserines; Protein Binding; Protein Conformation; Sequence Deletion; Unilamellar Liposomes

Elucidation of the fundamental interactions of proteins with biological membranes under native conditions is crucial for understanding the molecular basis of their biological function and malfunction. Notably, the large surface to volume ratio of living cells provides a molecular landscape for significant interactions of cellular components with membranes, thereby potentially modulating their function. However, such interactions can be challenging to probe using conventional biophysical methods due to the heterogeneity of the species and processes involved. Here, we use direct measurements of micron scale molecular diffusivity to detect and quantify the interactions of α-synuclein, associated with the etiology of Parkinson's disease, with negatively charged lipid vesicles. We further demonstrate that this microfluidic approach enables the characterization of size distributions of different binary mixtures of vesicles, which are not readily accessible using conventional light scattering techniques. Finally, the size distributions of the two α-synuclein conformations, free α-synuclein and membrane-bound α-synuclein, were resolved under varying lipid:protein ratios, thus, allowing the determination of the dissociation constant and the binding stoichiometry associated with this protein-lipid system. The microfluidic diffusional sizing platform allows these measurements to be performed on a time scale of minutes using microlitre volumes, thus, establishing the basis for an approach for the study of molecular interactions of heterogeneous systems under native conditions.

Topics: alpha-Synuclein; Diffusion; Microfluidic Analytical Techniques; Particle Size; Phosphatidylethanolamines; Phosphatidylserines; Protein Binding; Unilamellar Liposomes

α-Synuclein (α-Syn) is an abundant cytosolic protein involved in the release of neurotransmitters in presynaptic terminal and its aberrant aggregation is found to be associated with Parkinson's disease. Recent study suggests that the oligomers formed at the initial oligomerization stage may be the root cause of cytotoxicity. While characterizing this stage is challenging due to the inherent difficulties in studying heterogeneous and transient systems by conventional biochemical technology. Here we use solid-state nanopores to study the time-dependent kinetics of α-Syn oligomerization through a label-free and single molecule approach. A tween 20 coating method is developed to inhibit non-specific adsorption between α-Syn and nanopore surface to ensure successful and continuous detection of α-Syn translocation. We identify four types of oligomers formed in oligomerization stage and find an underlying consumption mechanism that the formation of large oligomers consumes small oligomers. Furthermore, the effect of lipid membrane on oligomerization of α-Syn is also investigated and the results show that 1,2-dioleoyl-sn-glycero-3-[phospho-L-serine] (DOPS) small unilamellar vesicles (SUVs) dramatically enhances the aggregation rate of α-Syn while do not alter the aggregation pathway.

Topics: alpha-Synuclein; Amino Acid Sequence; Humans; Nanopores; Phosphatidylserines; Polysorbates; Protein Aggregates; Protein Multimerization; Protein Transport; Surface Properties; Unilamellar Liposomes

Previous studies indicate that binding of alpha-synuclein to membranes is critical for its physiological function and the development of Parkinson's disease (PD). Here, we have investigated the association of fluorescence-labeled alpha-synuclein variants with different types of giant unilamellar vesicles using confocal microscopy. We found that alpha-synuclein binds with high affinity to anionic phospholipids, when they are embedded in a liquid-disordered as opposed to a liquid-ordered environment. This indicates that not only electrostatic forces but also lipid packing and hydrophobic interactions are critical for the association of alpha-synuclein with membranes in vitro. When compared to wild-type alpha-synuclein, the disease-causing alpha-synuclein variant A30P bound less efficiently to anionic phospholipids, while the variant E46K showed enhanced binding. This suggests that the natural association of alpha-synuclein with membranes is altered in the inherited forms of Parkinson's disease.

Topics: alpha-Synuclein; Amino Acid Sequence; Anions; Binding Sites; Cell Membrane; Fatty Acids; Fluorescent Dyes; Hydrophobic and Hydrophilic Interactions; Lipids; Microscopy, Fluorescence; Molecular Sequence Data; Molecular Weight; Mutation; Parkinson Disease; Phosphatidic Acids; Phosphatidylcholines; Phosphatidylglycerols; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylserines; Phospholipids; Protein Binding; Protein Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; Rhodamines; Static Electricity; Surface Properties; Unilamellar Liposomes