Solubility and aggregation of proteins are crucial factors for their functional and further biological roles. Aggregation of proteins in vivo, such as the amyloid beta (Aβ1-40) peptide into fibrils, is significantly modulated by membrane lipids, abundantly present in cells. We developed a model membrane system, composed of lipid hybrid-vesicles bearing embedded hydrophilic polymers to in vitro study the aggregation of the Aβ1-40 peptide. Focus is to understand and inhibit the primordial, nucleation stages of their fibrillation by added hybrid-vesicles, composed of a natural lipid and amphiphilic polymers. These designed hybrid-vesicles are based on 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC), displaying embedded hydrophilic (EO) m P n A_EG polymers (m = 2 or 3; P n = 10 to 52 with M n = 2800-9950 gmol-1) in amounts ranging from 5-20 mol%, anchored to the POPC vesicles via hydrophobic hexadecyl-, glyceryl- and cholesteryl-moieties, affixed to the polymers as end-groups. All investigated hybrid-vesicles significantly delay fibrillation of the Aβ1-40 peptide as determined by thioflavin T (ThT) assays. We observed that the hybrid-vesicles interacted with early aggregating species of Aβ1-40 peptide, irrespective of their composition or size. A substantial perturbation of both primary (k + k n ) and secondary (k + k 2) nucleation rates of Aβ1-40 by the POPC-polymer vesicles compared to POPC vesicles was observed, particularly for the cholesteryl-anchored polymers, interfering with the fragmentation and elongation steps of Aβ1-40. Furthermore, morphological differences of the aggregates were revealed by transmission electron microscopy (TEM) images supported the inhibitory kinetic signatures.
This journal is © The Royal Society of Chemistry.