Quantitative analysis of the molecular interactions driving Influenza A virus assembly in model and cellular membranes

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Cellular membranes are complex biological entities which perform a wide range of functions. The lateral organization of lipids and receptors in the plasma membrane (PM), for example, is involved in several biologicalprocesses such as cell-cell communication or viral infections. Themechanism by which the Influenza virus (IV) infects a cell and, eventually,spreads to other cells is paradigmatic in this context. It is known, in fact, that assembly and budding of progeny influenza virions is an intricate process that occurs through specialized lipid-protein domains of the PM named rafts.Unfortunately, the detailed molecular mechanisms behind this processremain unclear. In order to dissect the complex interactions between viralcomponents and the lipids and membrane proteins of the host cell, we will use novel physical models of the PM, i.e. asymmetric model membranes. This represents an important step forward in the field of membrane biophysics since, until recently, investigation of lipid-protein interaction has been carried almost exclusively on symmetric simple models of cellular membranes. These model bilayers did not take into account the important compositional asymmetry between inner and outer leaflets of PM.Our general goal is to clarify the molecular interactions governing thebudding and exit of IV from infected cells, by reconstituting the key viralcomponents in the above-mentioned reliable and controlled membranemodels and characterizing them with a sophisticated combination of Atomic Force Microscopy and advanced fluorescence microscopy techniques.Firstly, we will focus on the role of the viral matrix protein M1 in orchestrating the spatial assembly of IV components into a new virion budding from the host PM. Furthermore, we will investigate the relationship between the raft domains in the PM and IV infectious cycle. The interaction between IV components and PM raft domains is, in fact, not well understood. On one hand, we will quantitatively characterize the interplay between IV proteins and advanced (i.e. asymmetric) models of raft domains. On the other hand, the use of novel asymmetric models for the PM will provide us the chance to understand in general how the structure of PM domains is affected by leaflet compositional asymmetry and by the coupling between leaflets. This topic is of particular importance in the field of membrane biophysics, since orderedPM domains are involved in several physiological processes, such as cell signaling. The knowledge deriving from the experiments described in this proposal will be of great value for understanding the molecular mechanisms of IV exit from host cells and, ultimately, developing innovative methods to prevent the spreading of the viral infection.