Andrew Leidal, University of Calgary

Ghadir Alhindal1, Jackie Tsasa1, Chamalika Manawadu1, FuiBoon Kai1, Craig McCormick2 and Andrew M. Leidal1. 1Department of Physiology and Pharmacology and Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, 3280 Hospital Drive NW Calgary, Alberta, Canada T2N 4Z6 2Department of Microbiology and Immunology, Dalhousie University, 5850 College Street, Halifax NS, Canada B3H 4R2.

Building & Escaping

Enveloped viruses exploit host extracellular vesicle (EVs) biogenesis and secretion machinery to facilitate virion assembly and budding. Although many enveloped viruses hijack the endosomal complexes required for transport (ESCRT) machinery for egress, influenza A virus (IAV) buds from the plasma membrane via ESCRT-independent mechanisms that require the matrix 2 (M2) protein. Nevertheless, precisely how M2 mediates IAV assembly and budding within infected cells remains unclear. Here, we report that IAV hijacks non-canonical functions of ATG8/LC3 in EV biogenesis to facilitate viral budding. IAV M2 was found to recruit ATG8/LC3 to the plasma membrane and endo-lysosomal membranes via a conserved LC3-interaction region (LIR) within its cytoplasmic tail. Mutant influenza A viruses carrying single amino acid substitutions in M2 that disrupt interaction with ATG8/LC3 showed severe impairment in viral budding including the release of virion associated proteins and genomic RNA but had no overt defects in viral genomic RNA replication or protein production within host cells. IAV egress was also impaired in cells depleted of autophagy pathway components necessary for ATG8/LC3 conjugation to lipid membranes and the exocytic GTPase RAB27A. Future work will focus on identifying host and viral proteins that are recruited to sites of IAV budding by M2-ATG8/LC3 complexes and delineating the functional contributions of these components to IAV assembly and egress from infected cells. Overall, these studies will inform on the mechanisms of IAV egress and illuminate novel host targets that can be leveraged to combat infection or facilitate the production virus-like particles with therapeutic potential.