Role for Actin in the Polarized Release of Rotavirus

Rotaviruses are characterized by polarized release from the apical side of infected enterocytes, and the rotavirus VP4 spike protein specifically binds to the actin network at the apical pole of differentiated entero-cytic cells. To determine the functional consequences of this VP4-actin interaction, fluorescence recovery after photobleaching experiments were carried out to measure the diffusional mobility of VP4 associated with the microfilaments. Results show that VP4 binds to barbed ends of microfilaments by using actin treadmilling. Actin treadmilling inhibition results in the loss of rotavirus apical preferential release, suggesting a major role for actin in polarized rotavirus release. Rotaviruses belong to the Reoviridae family and are a major cause of infantile viral diarrhea worldwide. The nonenveloped particles contain a segmented double-stranded RNA genome, and rotaviruses are characterized by their enteric tropism. In differentiated enterocytic cells, virions reach the apical pole through an atypical trafficking pathway where they are released without cell lysis (6). Our previous data also show that the spike protein VP4 specifically interacts with and strongly re