Proteomic Profiling of the TRAF3 Interactome Network Reveals a New Role for the ER-to-Golgi Transport Compartments in Innate Immunity

van Zuylen, Wendy J.; Doyon, Priscilla; Clément, Jean-François; Khan, Kashif Aziz; D'Ambrosio, Lisa M.; Dô, Florence; St-Amant-Verret, Myriam; Wissanji, Tasheen; Emery, Gregory; Gingras, Anne-Claude; Meloche, Sylvain; Servant, Marc J.

This prompted us to ask whether enforced retention of TRAF3 at the ER-to-Golgi compartment could negatively influence the type I IFN response. In order to verify this, a TRAF3 mutant containing a COPI and COPII sorting signal peptide [50] , namely ''AKKFF'' [51] , at its C-terminal end was generated and used in confocal microscopy and reporter gene assays. Confocal microscopy experiments revealed that addition of dilysine and dihydrophobic residues to the C-terminal end of TRAF3 resulted in the formation of large TRAF3 aggregates which failed to colocalize with the Golgi marker GM130 upon infection with SeV ( Figure 7A ). Consequently, the ability of the TRAF3-AKKFF mutant to mediate TRAF3-dependent synergistic activation of the IFNb promoter was drastically reduced ( Figure 7B ), which is likely due to less binding to MAVS ( Figure S5 ).