Selective Interaction between Toxic Amyloid Oligomers and the Cell Membrane Revealed by Innovative AFM Applications

Abstract

The mechanism of cytotoxicity in amyloid diseases is still controversial. Several evidences indicate that the interaction between oligomers and plasma membrane plays a pivotal role in amyloid toxicity. It was proposed that oligomer-mediated cytotoxicity does not depend only on aggregates properties, but also on the chemical composition of the cell membrane.The short HypF-N peptide is able to aggregate in vitro, forming amyloid fibrils. HypF-N oligomers formed in different conditions show different levels of cytotoxicity. It has been demonstrated that the level of cytotoxicity is dependent on the concentration of negatively charged ganglioside GM1. In order to understand the interaction between lipids and oligomers, we previously studied by using SLBs as simplified models of plasma membrane.We proposed a completely new approach based on the use of single cell force spectroscopy (SCFS) on multifunctional substrates. Oligomers and fibrils formed in the two different conditions, with TFE (toxic) or with TFA (non-toxic), were patterned on glass substrate by using long polymer linker as flexible spacer. Single CHO cell is attached to a soft AFM cantilever and brought in contact with the different molecular species. The adhesion between cell and molecular substrate is quantified calculating the total work that must be spent in order to detach the cell from the molecular substrate. We found that toxic oligomers A bind the cell more efficiently with respect to oligomers B. Experiments were repeated by treating the cells with neuroaminidase to cleave the sialic acid residues from GM1. In this case, oligomers A and B show a similar behavior, indicating that the increased binding capability of oligomers A on untreated cells is mediated by GM1.