The actin-binding protein drebrin interacts with the respiratory syncytial virus matrix protein and promotes virus particle release.

Respiratory syncytial virus (RSV) is an enveloped virus that assembles and buds at the plasma membrane, producing filamentous infectious particles. Unlike many other enveloped viruses, a substantial fraction of RSV virions remains associated with the surface of infected cells, limiting our understanding of the membrane-scission mechanisms responsible for particle release. Here, we identified the actin-binding protein drebrin as a cellular interactor of the RSV matrix (M) protein, both in vitro and in infected cells. We demonstrated that RSV infection induces the relocalization of drebrin to actin-rich structures at the cell periphery associated with viral filaments. Using a Transwell-based assay to quantify infectious particles release without mechanically perturbing cells, we confirmed that RSV release is independent of the endosomal sorting complex required for transport (ESCRT) pathway and showed that drebrin depletion reduced RSV release, whereas drebrin overexpression enhanced it. Since drebrin depletion did not significantly affect overall infectious virus production, our results suggest that drebrin may act during the final step leading to membrane scission and RSV particle release. Finally, proteomics analysis identified Transmembrane 9 superfamily member 2 (TM9SF2) as a drebrin-associated protein specifically during infection. TM9SF2 depletion reduced RSV particle release and impaired the RSV-induced relocalization of drebrin to the plasma membrane. Together, these findings identify drebrin and TM9SF2 as host factors regulating RSV release and support a model in which TM9SF2 promotes the recruitment of drebrin to viral budding sites.