Global mapping of Salmonella enterica-host protein-protein interactions during infection

Intracellular bacterial pathogens inject effector proteins to hijack host cellular processes and promote their survival and proliferation. To systematically map effector-host protein-protein interactions (PPIs) during infection, we generated a library of 32 Salmonella enterica serovar Typhimurium (STm) strains expressing chromosomally encoded affinity-tagged effectors and quantified PPIs in macrophages and epithelial cells. We identified 446 effector-host PPIs, 25 of which were previously described, and validated 13 by reciprocal co-immunoprecipitation. While effectors converged on the same host cellular processes, most had multiple targets, which often differed between cell types. We demonstrate that SseJ, SseL, and SifA modulate cholesterol accumulation at the Salmonella-containing vacuole (SCV) partially via the cholesterol transporter Niemann-Pick C1 protein. PipB recruits the organelle contact site protein PDZD8 to the SCV, and SteC promotes actin bundling by phosphorylating formin-like proteins. This study provides a method for probing host-pathogen PPIs during infection and a resource for interrogating STm effector mechanisms. [Display omitted] •A host-pathogen protein-protein interaction map during infection•Salmonella effectors are multifunctional, with most targeting more than one host process•Effectors can converge on same host process and act in a cell-type-specific manner•SteC promotes actin bundling by phosphorylating formin-like proteins Pathogens hijack host cells by injecting effector proteins. In this work, Walch & Selkrig et al. used quantitative proteomics to systematically map the host targets of Salmonella effectors during infection. This effort yielded hundreds of protein-protein interactions, highlighted general effector properties, and uncovered missing links in Salmonella effector biology.