Crucial roles of TNFAIP8 protein in regulating apoptosis and Listeria infection.

TNF-α-induced protein 8 (TNFAIP8 or TIPE) is a newly described regulator of cancer and infection. However, its precise roles and mechanisms of actions are not well understood. We report in this article that TNFAIP8 regulates Listeria monocytogenes infection by controlling pathogen invasion and host cell apoptosis in a RAC1 GTPase-dependent manner. TNFAIP8-knockout mice were resistant to lethal L. monocytogenes infection and had reduced bacterial load in the liver and spleen. TNFAIP8 knockdown in murine liver HEPA1-6 cells increased apoptosis, reduced bacterial invasion into cells, and resulted in dysregulated RAC1 activation. TNFAIP8 could translocate to plasma membrane and preferentially associate with activated RAC1-GTP. The combined effect of reduced bacterial invasion and increased sensitivity to TNF-α-induced clearance likely protected the TNFAIP8-knockout mice from lethal listeriosis. Thus, by controlling bacterial invasion and the death of infected cells through RAC1, TNFAIP8 regulates the pathogenesis of L. monocytogenes infection.