Proximity labelling reveals VPS13C as a regulator of Salmonella-containing vacuole fission.

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a facultative intracellular bacterial pathogen that grows within a specialized membrane-bound compartment known as the Salmonella-containing vacuole (SCV). The molecular composition and regulatory mechanisms governing SCV dynamics remain incompletely understood. In this study, we employed proximity-dependent biotin identification (BioID) to analyze the SCV proteome during infection. For this, we targeted the UltraID biotin ligase to the SCV by fusing it to a type 3 secreted effector. We demonstrate that the bacteria express and translocate the effector-UltraID fusion protein directly into host cells for labeling of the cytosolic face of the SCV surface. Proteomic analysis of biotinylated proteins revealed previously undescribed proteins associated with the SCV, including regulators of vesicular trafficking, cellular metabolism and lipid transport. Among these, VPS13C, a lipid transporter and membrane contact site protein, was identified as a critical regulator of SCV morphology and fission. Functional studies revealed that VPS13C also promotes ER-SCV contact formation, controls SCV positioning in host cells, and facilitates cell-to-cell spread by the bacteria. Together, our findings highlight the utility of BioID as a tool to study host-pathogen interactions in the context of infection and characterize VPS13C as a novel modulator of the intracellular life cycle of S. Typhimurium.