Salmonella subverts autophagy balancing bacterial fate and cellular inflammation

Abstract

SummarySalmonella Typhimurium (S. Typhimurium) is an enteric bacterium capable of invading a wide range of host cell types and adopting different intracellular lifestyles for survival. Host endocytic trafficking and autophagy have been implied to regulate the S. Typhimurium subcellular localization and survival. To reveal alternative host regulators on S. Typhimurium lifestyle, we combined a novel fluorescent reporter, Salmonella Intracellular Analyzer (SINA) with haploid forward genetic screening. This identified transcription factor c-MYC as a negative regulator of S. Typhimurium cytosolic lifestyle via stabilizing the Salmonella-containing vacuole (SCV). We further confirmed that c-MYC downstream regulated LC3 acts to maintain SCV stability and limits S. Typhimurium cytosolic lifestyle. We demonstrated that LC3 is recruited to the SCV prior to the endomembrane damage marker Galectin 3, and it regulates SCV stability independent of the autophagosome adaptor NDP52. The LC3 processing enzymes ATG3 and ATG4 reciprocally act on SCV stability, where the loss of LC3-PE conjugation in the absence of ATG3 limits SCV damages. We further identified the dosage-dependent function of the S. Typhimurium effector SopF in mediating SCV stability by actively avoiding LC3 recruitment to the proximity of the SCV to reduce its catastrophic rupture and host cell death. Altogether, we offer insights on the significance of cellular transcription profile in the determination of S. Typhimurium pathophysiology as well as the underlying host-evasion strategy of S. Typhimurium.