Adapter protein that plays essential roles in both innate and adaptive immunity. Plays a crucial role in the regulation of thymocyte development (PubMed:26195727). Mechanistically, mediates TCR-stimulated activation through recruiting MAP2K1/MEK1 to the Golgi and, thereby, facilitating the interaction of MAP2K1/MEK1 with its activator BRAF (PubMed:26195727). Also plays an essential role in regulatory T-cell stability and function by recruiting the serine-threonine phosphatase catalytic subunit (PPP2CA) to the lysosome, thereby facilitating the interaction of PP2Ac with the mTORC1 component RPTOR and restricting glycolytic metabolism (PubMed:30115741). Positively regulates TLR4 signaling activity in macrophage-mediated inflammation by acting as a molecular clamp to facilitate LPS-induced translocation of TLR4 to lipid rafts (PubMed:30573680). In response to viral infection, facilitates the recruitment of TRAF3 to MAVS within mitochondria leading to IRF3 activation and interferon production (PubMed:31390091). However, participates in the maintenance of immune homeostasis and the prevention of overzealous innate immunity by promoting 'Lys-48'- dependent ubiquitination of TBK1 (PubMed:32366851). {ECO:0000269|PubMed:26195727, ECO:0000269|PubMed:30115741, ECO:0000269|PubMed:30573680, ECO:0000269|PubMed:31390091, ECO:0000269|PubMed:32366851}. This is the function of ENSG00000009790 (TRAF3IP3, TRAF3 interacting protein 3).