Class II ADP-Ribosylation factors are required for efficient secretion of dengue viruses.
Résumé
Identification and characterization of virus-host interactions are very important steps towards a better comprehension of the molecular mechanisms responsible for disease progression and pathogenesis. To date, very few cellular factors involved in the life cycle of flaviviruses, which are important human pathogens, have been described. In this study, we demonstrate a crucial role for class II Arf proteins (Arf4 and Arf5) in dengue flavivirus life cycle. We show that simultaneous depletion of Arf4 and Arf5 block recombinant subviral particles (RSPs) secretion for all four dengue serotypes. Immunostaining analysis suggests that class II Arf proteins are required at an early, pre-Golgi step for dengue virus secretion. Using a horseradish peroxidase protein fused to a signal peptide, we show that class II Arfs act specifically on dengue virus secretion without altering the secretion of proteins through the constitutive secretory pathway. Co-immunoprecipitation data demonstrate that the dengue prM glycoprotein interacts with class II Arf proteins, but not through its C terminus VxPx motif. Finally, experiments performed with replication-competent dengue and yellow fever viruses demonstrate that the depletion of class II Arfs inhibits virus secretion, thus confirming their implication in viral life cycle, although data obtained with West Nile virus pointed out to the existence of differences in virus-host interactions among flaviviruses. Our findings shed new light on a molecular mechanism used by dengue viruses during the late stages of the life cycle and demonstrate a novel function for class II Arf proteins.