Systematic identification of host cell regulators of Legionella pneumophila pathogenesis using a genome-wide CRISPR screen

During infection, Legionella pneumophila translocates over 300 effector proteins into the host cytosol, allowing the pathogen to establish an endoplasmic reticulum (ER)-like Legionella-containing vacuole (LCV) that supports bacterial replication. Here, we perform a genome-wide CRISPR-Cas9 screen and secondary targeted screens in U937 human monocyte/macrophage-like cells to systematically identify host factors that regulate killing by L. pneumophila. The screens reveal known host factors hijacked by L. pneumophila and novel genes spanning diverse trafficking and signaling pathways. We highlight a number of examples of newly discovered biology, including two uncharacterized genes, C1ORF43 and KIAA1109, which regulate phagocytosis. Furthermore, we show that RAB10 and its chaperone RABIF are required for L. pneumophila replication and ER recruitment to the LCV. Finally, we show that Rab10 protein is recruited to the LCV and ubiquitinated by the effectors SidC/SdcA. Collectively, our results provide a wealth of new insights into L. pneumophila pathogenesis and mammalian cell function.