Uptake of Rabies Virus into Epithelial Cells by Clathrin-Mediated Endocytosis Depends upon Actin

Abstract

Rabies virus (RABV) causes a fatal zoonotic encephalitis. Disease symptoms require replication and spread of the virus within neuronal cells; however, in infected animals as well as in cell culture the virus replicates in a broad range of cell types. Here we use a single-cycle RABV and a recombinant vesicular stomatitis virus (rVSV) in which the glycoprotein (G) was replaced with that of RABV (rVSV RABV G) to examine RABV uptake into the African green monkey kidney cell line BS-C-1. Combining biochemical studies and real-time spinning-disk confocal fluorescence microscopy, we show that the predominant entry pathway of RABV particles into BS-C-1 cells is clathrin dependent. Viral particles enter cells in pits with elongated structures and incomplete clathrin coats which depend upon actin to complete the internalization process. By measuring the time of internalization and the abundance of the clathrin adaptor protein AP2, we further show that the pits that internalize RABV particles are similar to those that internalize VSV particles. Pharmacological perturbations of dynamin or of actin polymerization inhibit productive infection, linking our observations on particle uptake with viral infectivity. This work extends to RABV particles the finding that clathrin-mediated endocytosis of rhabdoviruses proceeds through incompletely coated pits which depend upon actin.