Porcine reproductive and respiratory syndrome virus envelope (E) protein interacts with tubulin

Porcine reproductive and respiratory syndrome virus (PRRSV) encodes the small envelope (E) protein which is a minor structural component of the virion that is important for virus infectivity. To better understand the biological functions of the E protein, we studied interactions between E and PRRSV cellular proteins. Using immunoprecipitation-coupled mass spectrometry approach, we previously identified tubulin-α as an interacting partner of E. In this study, we confirmed this interaction using co-immunoprecipitation and co-localization assays. In addition, we demonstrated that the 25-residue C-terminal endodomain of E was essential for its interaction with tubulin-α. Over-expression of the E protein in cultured cells led to microtubule depolymerisation. Similarly, we observed that microtubule depolymerisation occurs in MARC-145 cells at the late stage of PRRSV replication. Also, depolymerisation of microtubules by colcemid significantly inhibited PRRSV replication in MARC-145 cells at early time points but the effect was not as dramatic at the late stage of infection. These data suggest that PRRSV infection of MARC-145 cells requires the microtubules network to facilitate early phase of infection whereas microtubules depolymerisation occurs at the late stage of PRRSV replication. Interaction between E and tubulin-α may contribute to microtubules depolymerisation.