Dissection of the Influenza A Virus Endocytic Routes Reveals Macropinocytosis as an Alternative Entry Pathway

de Vries, Erik; Tscherne, Donna M.; Wienholts, Marleen J.; Cobos-Jiménez, Viviana; Scholte, Florine; García-Sastre, Adolfo; Rottier, Peter J. M.; de Haan, Cornelis A. M.

Here we have established entry assay conditions that allow dissecting cell entry of IAV into a dynamin-dependent (DYNA-DEP) and a dynamin-independent (DYNA-IND) component. Dynamin is a large GTPase forming multimeric assemblies around the neck of newly formed endocytic vesicles. GTP hydrolysis is required for pinching off of the vesicles [20] . Whereas CME is completely dependent on dynamin, several other endocytic routes do not require dynamin [21] . We performed an extensive characterization of the dynamin-independent IAV entry route using pharmacological inhibitors as well as by expressing dominant-negative mutants and applying siRNA induced gene silencing as tools. Taken together the results identify a pathway that closely resembles macropinocytosis as a novel entry pathway for IAV.