TMED2 Potentiates Cellular IFN Responses to DNA Viruses by Reinforcing MITA Dimerization and Facilitating Its Trafficking

Mediator of IRF3 activation (MITA), also known as stimulator of interferon genes (STING), plays a vital role in the innate immune responses to cytosolic dsDNA. The trafficking of MITA from the ER to perinuclear vesicles is necessary for its activation of the downstream molecules, which lead to the production of interferons and pro-inflammatory cytokines. However, the exact mechanism of MITA activation remains elusive. Here, we report that transmembrane emp24 protein transport domain containing 2 (TMED2) potentiates DNA virus-induced MITA signaling. The suppression or deletion of TMED2 markedly impairs the production of type I IFNs upon HSV-1 infection. TMED2-deficient cells harbor greater HSV-1 load than the control cells. Mechanistically, TMED2 associates with MITA only upon viral stimulation, and this process potentiates MITA activation by reinforcing its dimerization and facilitating its trafficking. These findings suggest an essential role of TMED2 in cellular IFN responses to DNA viruses.