Relevance of coronavirus viroporins and PDZ-binding-motifs in virus replication and virulence

Trabajo presentado en el 37th Annual Meeting American Society for Virology Symposia, celebrado en Maryland (Estados Unidos), del 14 al 18 de julio de 2018Viroporins are viral proteins with ion channel (IC) activity that play an important role in several processes including virus replication and pathogenesis. While many coronaviruses (CoVs) encode two viroporins, SARS-CoV encodes three: proteins 3a, E and 8a. Additionally, 3a and E proteins have a PDZ-binding motif (PBM), which may bind over 400 cellular proteins containing a PDZ domain, making them relevant for the control of cell function. In the present work, a comparative study of the functional motifs included within the SARS-CoV viroporins was performed focusing on the roles of the IC and PBM of E and 3a proteins. Our results showed that both the full-length E and 3a proteins were required for optimum SARS-CoV replication and virulence whereas viroporin 8a had a minor impact on these activities. However, IC and PBM activities of E, but not 3a protein, were necessary for virulence in mice. Interdependence between E and 3a was identified. A virus missing both proteins was not viable, whereas the presence of either protein with a functional PBM restored virus viability, indicating functional redundancy between the PBMs of these proteins. Given the relevance of SARS-CoV PBMs, the presence of these motifs was studied in other CoVs. MERSCoV, another highly pathogenic human CoV, includes a PBM in both E and 5 proteins. The interaction between the 256 known human PDZ domains and the PBMs of SARS-CoV and MERS-CoV was studied using a specific yeast-two-hybrid platform. More than 20 cellular proteins mostly involved in virus-cell and cell-cell interaction were identified. Some of these proteins are involved in immune response or in the infectivity of other viruses. Collectively, these results demonstrate redundant roles for the IC and PBMs for optimal virus replication and pathogenesis suggesting that they are potential targets for antiviral therap