Lipid-polymer hybrid-vesicles interrupt nucleation of amyloid fibrillation

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 (Aβ 1-40 ) 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 Aβ 1-40 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 Aβ 1-40 peptide as determined by thioflavin T (ThT) assays. We observed that the hybrid-vesicles interacted with early aggregating species of Aβ 1-40 peptide, irrespective of their composition or size. A substantial perturbation of both primary ( k + k n ) and secondary ( k + k 2 ) nucleation rates of Aβ 1-40 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 Aβ 1-40 . Furthermore, morphological differences of the aggregates were revealed by transmission electron microscopy (TEM) images supported the inhibitory kinetic signatures. Hybrid-vesicles composed of amphiphilic polymers in POPC-lipids inhibit Aβ 1-40 peptide fibrillation by interfering with primary and secondary nucleation, most pronounced by the cholesteryl-anchored polymers.