A genome-wide screen in macrophages identifies PTEN as required for myeloid restriction of Listeria monocytogenes infection

Abstract

Listeria monocytogenes(Lm) is an intracellular foodborne pathogen which causes the severe disease listeriosis in immunocompromised individuals. Macrophages play a dual role duringLminfection by both promoting dissemination ofLmfrom the gastrointestinal tract and limiting bacterial growth upon immune activation. Despite the relevance of macrophages toLminfection, the mechanisms underlying phagocytosis ofLmby macrophages are not well understood. To identify host factors important forLminfection of macrophages, we performed an unbiased CRISPR/Cas9 screen which revealed pathways that are specific to phagocytosis ofLmand those that are required for internalization of bacteria generally. Specifically, we discovered the tumor suppressor PTEN promotes macrophage phagocytosis ofLmandL.ivanovii, but not other Gram-positive bacteria. Additionally, we found that PTEN enhances phagocytosis ofLmvia its lipid phosphatase activity by promoting adherence to macrophages. Using conditional knockout mice lackingPtenin myeloid cells, we show that PTEN-dependent phagocytosis is important for host protection during oralLminfection. Overall, this study provides a comprehensive identification of macrophage factors involved in regulatingLmuptake and characterizes the function of one factor, PTEN, duringLminfectionin vitroandin vivo. Importantly, these results demonstrate a role for opsonin-independent phagocytosis inLmpathogenesis and suggest that macrophages play a primarily protective role during foodborne listeriosis.