Interaction of toxic and non-toxic HypF-N oligomers with lipid bilayers investigated at high resolution with atomic force microscopy

// Reinier Oropesa-Nunez 1,2 , Silvia Seghezza 1 , Silvia Dante 1 , Alberto Diaspro 1,3 , Roberta Cascella 4 , Cristina Cecchi 4 , Massimo Stefani 4 , Fabrizio Chiti 4 and Claudio Canale 1 1 Department of Nanophysics, Istituto Italiano di Tecnologia, Genova, Italy 2 DIBRIS Department, University of Genova, Genova, Italy 3 Department of Physics, University of Genova, Genova, Italy 4 Section of Biochemistry, Department of Biomedical Experimental and Clinical Sciences, University of Florence, Firenze, Italy Correspondence to: Claudio Canale, email: // Keywords : protein misfolding, protein aggregation, ganglioside GM1, amyloid oligomers, AFM Received : May 17, 2016 Accepted : June 26, 2016 Published : July 06, 2016 Abstract Protein misfolded oligomers are considered the most toxic species amongst those formed in the process of amyloid formation and the molecular basis of their toxicity, although not completely understood, is thought to originate from the interaction with the cellular membrane. Here, we sought to highlight the molecular determinants of oligomer-membrane interaction by atomic force microscopy. We monitored the interaction between multiphase supported lipid bilayers and two types of HypF-N oligomers displaying different structural features and cytotoxicities. By our approach we imaged with unprecedented resolution the ordered and disordered lipid phases of the bilayer and different oligomer structures interacting with either phase. We identified the oligomers and lipids responsible for toxicity and, more generally, we established the importance of the membrane lipid component in mediating oligomer toxicity. Our findings support the importance of GM1 ganglioside in mediating the oligomer-bilayer interaction and support a mechanism of oligomer cytotoxicity involving bilayer destabilization by globular oligomers within GM1-rich ordered raft regions rather than by annular oligomers in the surrounding disordered membrane domains.