Charge of Phospholipids Determines the Rate of Lysozyme Aggregation but Not the Structure and Toxicity of Amyloid Aggregates

Abstract

Biophysical properties of plasma membranes are determined by a chemical structure of phospholipids, including saturation of fatty acids and charge of polar heads of these molecules. Phospholipids not only determine fluidity and plasticity of membranes but also play an important role in abrupt aggregation of misfolded proteins. In this study, we investigate the role of the charge of the most abundant phospholipids in the plasma membrane on the aggregation properties of the lysozyme. We found that the charge of phospholipids determines the aggregation rate of lysozyme and the morphology of the protein aggregates. However, the secondary structure and toxicity of these protein specimens are determined by the chemical nature rather than the charge of phospholipids. These findings show that the charge of phospholipids can be a key factor that determines the stability and aggregation mechanism of amyloidogenic proteins.

Elucidation of the Effect of Phospholipid Charge on the Rate of Insulin Aggregation and Structure and Toxicity of Amyloid Fibrils

“…Using nanoinfrared spectroscopy, also known as atomic force microscopy infrared (AFM-IR) spectroscopy, the researchers demonstrated that insulin strongly interacts with both phosphatidylcholine (PC) and cardiolipin (CL). In AFM-IR, a metallized scanning probe is placed on the sample of interest. − Next, the sample is illuminated by pulsed tunable IR laser, which induces thermal expansions in the sample. − These expansions are recorded by the probe and converted into IR spectra. ,,− Thus, AFM-IR can be used to determine the chemical structure of individual protein aggregates. − ,− Using AFM-IR, Rizevsky and co-workers also found that both PC and CL were found to be present in insulin oligomers that were grown in the presence of these phospholipids . Independently, Matveyenka and co-workers demonstrated that the degree of saturation of FAs of both PC and CL plays an important role in insulin aggregation .…”

“… 22 − 31 These expansions are recorded by the probe and converted into IR spectra. 18 , 19 , 32 − 35 Thus, AFM-IR can be used to determine the chemical structure of individual protein aggregates. 26 − 31 , 33 − 37 Using AFM-IR, Rizevsky and co-workers also found that both PC and CL were found to be present in insulin oligomers that were grown in the presence of these phospholipids.…”

Length and saturation of fatty acids in phosphatidylserine determine the rate of lysozyme aggregation simultaneously altering the structure and toxicity of amyloid oligomers and fibrils

“…Similar interactions are thought to stabilize such protein‐lipid aggregates (Alza et al, 2019; Galvagnion, 2017; Giasson et al, 2001; Kiechle et al, 2020; Ueda et al, 1993). Using nano‐Infrared spectroscopy, our group demonstrated that such aggregates possessed lipids in their structure (Zhaliazka et al, 2022; Zhaliazka & Kurouski, 2023).…”

Concentration of Phosphatidylserine Influence Rates of Insulin Aggregation and Toxicity of Amyloid Aggregates In Vitro

“…Our findings also suggest that a change in the relative concentrations of two zwitterions does not substantially alter the rate of insulin aggregation, which is consistent with the reported results for lysozyme by Zhaliazka and co-workers, according to which both PC and PE equivalently strongly inhibit protein aggregation. 44 Morphological and Structural Characterization of Insulin Aggregates Grown in the Presence of LUVs with Different Concentrations of PS. We utilized AFM to examine the morphology of insulin aggregates grown in the presence of LUVs with different concentrations of PS.…”

“…Specifically, the equimolar presence of fully saturated PS enabled the strongest enhancement of the rate of insulin aggregation compared to PS with unsaturated fatty acids. It was also found that insulin and lysozyme aggregates formed in the presence of PS exerted significantly different cell toxicities compared to the fibrils grown in the lipid-free environment. ,, Although the above-discussed findings can be valuable for the understanding of the role of PS in amyloidosis, they were obtained upon exposition of both insulin and lysozyme to the large unilamellar vesicles (LUVs) composed of PS alone. ,, The question to ask is whether an increase in the concentration of PS relative to zwitterionic lipids, such as PC and phosphatidylethanolamine (PE), primary constituents of the plasma membranes of most eucaryotic cells, would alter the rate of protein aggregation, as was evident for PS itself. To answer this question, we used a set of biophysical and molecular biology techniques that allowed for the determination of the rate of protein aggregation, the elucidation of morphology, secondary structure, and the toxicity of protein aggregates grown in the presence of lipid mixtures and in the lipid-free environment.…”