A Kinetic Map of the Influence of Biomimetic Lipid Model Membranes on A beta 42 Aggregation

The aggregation of the amyloid fl (Afl) peptide is one of the molecular hallmarks of Alzheimer's disease (AD). Although Afl deposits have mostly been observed extracellularly, various studies have also reported the presence of intracellular Afl assemblies. Because these intracellular Afl aggregates might play a role in the onset and progression of AD, it is important to investigate their possible origins at different locations of the cell along the secretory pathway of the amyloid precursor protein, from which Afl is derived by proteolytic cleavage. Senile plaques found in AD are largely composed of the 42-residue form of Afl (Afl42). Intracellularly, Afl42 is produced in the endoplasmatic reticulum (ER) and Golgi apparatus. Since lipid bilayers have been shown to promote the aggregation of Afl, in this study, we measure the effects of the lipid membrane composition on the in vitro aggregation kinetics of Afl42. By using large unilamellar vesicles to model cellular membranes at different locations, including the inner and outer leaflets of the plasma membrane, late endosomes, the ER, and the Golgi apparatus, we show that Afl42 aggregation is inhibited by the ER and Golgi model membranes. These results provide a preliminary map of the possible effects of the membrane composition in different cellular locations on Afl aggregation and suggest the presence of an evolutionary optimization of the lipid composition to prevent the intracellular aggregation of Afl.