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

Abstract

Tumor Necrosis Factor receptor-associated factor-3 (TRAF3) is a central mediator important for inducing type I interferon (IFN) production in response to intracellular double-stranded RNA (dsRNA). Here, we report the identification of Sec16A and p115, two proteins of the ER-to-Golgi vesicular transport system, as novel components of the TRAF3 interactome network. Notably, in non-infected cells, TRAF3 was found associated with markers of the ER-Exit-Sites (ERES), ER-to-Golgi intermediate compartment (ERGIC) and the cis-Golgi apparatus. Upon dsRNA and dsDNA sensing however, the Golgi apparatus fragmented into cytoplasmic punctated structures containing TRAF3 allowing its colocalization and interaction with Mitochondrial AntiViral Signaling (MAVS), the essential mitochondria-bound RIG-I-like Helicase (RLH) adaptor. In contrast, retention of TRAF3 at the ER-to-Golgi vesicular transport system blunted the ability of TRAF3 to interact with MAVS upon viral infection and consequently decreased type I IFN response. Moreover, depletion of Sec16A and p115 led to a drastic disorganization of the Golgi paralleled by the relocalization of TRAF3, which under these conditions was unable to associate with MAVS. Consequently, upon dsRNA and dsDNA sensing, ablation of Sec16A and p115 was found to inhibit IRF3 activation and anti-viral gene expression. Reciprocally, mild overexpression of Sec16A or p115 in Hec1B cells increased the activation of IFNβ, ISG56 and NF-κB -dependent promoters following viral infection and ectopic expression of MAVS and Tank-binding kinase-1 (TBK1). In line with these results, TRAF3 was found enriched in immunocomplexes composed of p115, Sec16A and TBK1 upon infection. Hence, we propose a model where dsDNA and dsRNA sensing induces the formation of membrane-bound compartments originating from the Golgi, which mediate the dynamic association of TRAF3 with MAVS leading to an optimal induction of innate immune responses.

Mint3 potentiates TLR3/4- and RIG-I–induced IFN-β expression and antiviral immune responses

“…In uninfected cells, TRAF3 resides in the ER-to-Golgi intermediate compartment and the cis-Golgi apparatus (15). Following viral infection, the Golgi apparatus fragmented into cytoplasmic punctated structures containing TRAF3, allowing its colocalization and interaction with other adaptors, such as MAVS (15).…”

“…In uninfected cells, TRAF3 resides in the ER-to-Golgi intermediate compartment and the cis-Golgi apparatus (15). Following viral infection, the Golgi apparatus fragmented into cytoplasmic punctated structures containing TRAF3, allowing its colocalization and interaction with other adaptors, such as MAVS (15). Thus, retention of TRAF3 at the ER-to-Golgi vesicular transport system blunted the ability of TRAF3 to interact with MAVS upon viral infection and consequently decreased type I IFN secretion (15).…”

“…Following viral infection, the Golgi apparatus fragmented into cytoplasmic punctated structures containing TRAF3, allowing its colocalization and interaction with other adaptors, such as MAVS (15). Thus, retention of TRAF3 at the ER-to-Golgi vesicular transport system blunted the ability of TRAF3 to interact with MAVS upon viral infection and consequently decreased type I IFN secretion (15). Mint3 associates with several membrane proteins in Golgi and regulate their traffic from the trans-Golgi network (10)(11)(12).…”

“…In wild-type mouse embryonic fibroblasts (MEFs), TRAF3 was distributed in a speckle pattern (Fig. 4F), which was vital for the downstream signal transduction (15). However, TRAF3 distribution was dramatically changed from a speckle pattern to a diffuse pattern in Mint3-deficient MEFs (Fig.…”

Ubiquitin in the activation and attenuation of innate antiviral immunity

“…This facilitates interactions between TBK1, inhibitor of NF-κB kinase subunit ε (IKKε) and TRAFs, particularly TRAF3. Upon RLR activation, these proteins are colocalized at the cytosolic surface of the mitochondrial outer membrane (Parvatiyar et al, 2010;van Zuylen et al, 2012), coordinated by the mitochondrial antiviral-signaling protein (MAVS; also termed VISA/Cardif/IPS-1).…”