Abstract
Type I interferons (IFNs) are the first frontline of the host innate immune response against invading pathogens. Herein, we characterized an unknown protein encoded by phospholipase A2 inhibitor and LY6/PLAUR domain-containing (PINLYP) gene that interacted with TBK1 and induced type I IFN in a TBK1- and IRF3-dependent manner. Loss of PINLYP impaired the activation of IRF3 and production of IFN-β induced by DNA virus, RNA virus, and various Toll-like receptor ligands in multiple cell types. Because PINLYP deficiency in mice engendered an early embryonic lethality in mice, we generated a conditional mouse in which PINLYP was depleted in dendritic cells. Mice lacking PINLYP in dendritic cells were defective in type I IFN induction and more susceptible to lethal virus infection. Thus, PINLYP is a positive regulator of type I IFN innate immunity and important for effective host defense against viral infection.