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). Interacts (via its coiled-coil domain) with TRAF3 (via isoleucine zipper) (PubMed:31390091, PubMed:32366851). Interacts with MAP2K1 (PubMed:26195727). Interacts with PPP2CA; this interaction targets PPP2CA to the lysosomes (PubMed:30115741). Interacts with TLR4 (PubMed:30573680). Interacts with MAVS (PubMed:31390091). Interacts with TBK1 (PubMed:32366851). Accumulates on the mitochondria after virus infection.