Biophysical Society Thematic Meeting | Ascona, Switzerland

Liposomes, Exosomes, and Virosomes: From Modeling Complex Membrane Processes to Medical Diagnostics and Drug Delivery

Monday Speaker Abstracts

Artificial Cell Membrane Mimics to Study the Role of the Influenza Virus Matrix Protein M1 in Virus Budding David Saletti 1,2 , Birger Eklund 1 , Jens Radzimanowski 3 , Winfried Weissenhorn 3 , Patricia Bassereau 2 , Marta Bally 1,2 . 1 Chalmers University of Technology, Gothenburg, Sweden, 2 Institut Curie, Paris, France, 3 Université Joseph Fourier, Grenoble, France. The influenza virus egresses from its host by deforming the plasma membrane into a bud before pinching off by membrane fission. The viral matrix protein M1, a protein that forms a layer underneath the vial membrane connecting it to the viral genetic material, is believed to play an important role in the virion formation process. Nevertheless, the mechanisms underlying virus assembly and budding are still poorly understood. In this project, we take advantage of minimal cell-membrane models to study the interactions between the matrix protein and lipid membranes. Specifically, we aim at providing fundamental understating on the role of M1 in virus assembly and egress as well as in virus uncoating during entry. Giant unilamellar vesicles (GUV) are used to study the protein’s ability to deform membranes into a bud. Binding studies performed with fluorescently-labelled proteins reveal that M1 alone is capable of deforming membranes: the interaction leads to membrane inward tubulation, creating vesicle–enclosed lipid structures greatly enriched in matrix protein. GUV experiments are further complemented with investigations using supported lipid bilayers (SLBs) in combination with surface-sensitive techniques. Quartz crystal microbalance experiments make it possible to characterize the protein’s binding affinity and specificity to negatively charged membranes. Our data reveal that protein binding is pH, salt and membrane- charge dependent. Further imaging of the SLB using fluorescence microscopy, surface-enhanced ellipsometry contrast and atomic force microscopy indicates that the protein can locally recruit negatively charged lipids, shedding light on the protein’s propensity to self-aggregation at the bilayer surface. Taken together, our study illustrate the unique potential of cell membrane mimics in providing fundamental biophysical insights into the properties of protein-membrane interactions and into the mechanisms leading to membrane deformation.

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