Abstract
An intriguing enigma in virology is the utilization of transferrin receptor 1 (TfR1) by various viruses as an entry portal into host cells, a mechanism that remains relatively underexplored. In this study, we report a strategy to investigate the multifaceted aspects of viral entry, using Influenza A viruses (IAVs) as a model system. By decorating the sialylated viral envelope with photo-crosslinking moieties, we identify and elucidate the pivotal role of TfR1 in this process. Our results demonstrate that TfR1 initially functions as a receptor, interacting with the viral neuraminidase (NA) through its extracellular apical domain, thereby initiating viral endocytosis. Subsequently, TfR1 acts as a matrix degradator, engaging its intracellular stop-transfer sequence with the viral matrix protein 1 (M1), which in turn triggers proteasome- and aggresome-mediated nucleocapsid uncoating. The identification of the molecular interactions between TfR1 and NA, as well as the reciprocal degradation of TfR1 and M1 not only illuminates a cellular pathway that enriches our understanding of viral entry mechanisms but also presents exciting avenues for the development of innovative antiviral strategies beyond IAVs.