Amyloid-forming proteins alter the local mechanical properties of lipid membranes.

A diverse number of diseases, including Alzheimer's disease, Huntington's disease, and type 2 diabetes, are characterized by the formation of fibrillar protein aggregates termed amyloids. The precise mechanism by which aggregates are toxic remains unclear; however, these proteins have been shown to interact strongly with lipid membranes. We investigated morphological and mechanical changes in model lipid bilayers exposed to amyloid-forming proteins by reconstructing the tapping forces associated with atomic force microscopy (AFM) imaging in solution. Tip/sample tapping forces contain information regarding mechanical properties of surfaces. Interpretation of the mechanical changes in the bilayers was aided by numerical simulations of the entire AFM experiment. Amyloid-forming proteins disrupted distinct regions of the bilayer morphology, and these regions were associated with decreased Young's modulus and adhesive properties. These changes in bilayer mechanical properties upon exposure to amyloid-forming proteins may represent a common mechanism leading to membrane dysfunction in amyloid diseases.