Salmonella Typhimurium persistently infects host via its effector SseJ-induced PHB2-mediated mitophagy.

Abstract

Despite decades of research on effective methods to resist Salmonella enterica serovar Typhimurium (S. Typhimurium) pathogenicity, the mechanisms of S. Typhimurium-host interactions have not been fully determined. S. Typhimurium is characterized as an important zoonosis in public health worldwide because of its endemicity, high morbidity, and difficulty in applying control and prevention measures. Herein, we introduce a novel bacterial factor, secretion system effector J (SseJ), and its interactive host protein, PHB2 (prohibitin 2). We explored whether SseJ affected S. Typhimurium replication and survival in the host. S. Typhimurium infection caused severe mitochondrial damage and mitophagy, which facilitated S. Typhimurium proliferation in cells. S. Typhimurium SseJ activated the PINK1 (PTEN induced kinase 1)-PRKN (parkin RBR E3 ubiquitin protein ligase)-autophagosome-dependent mitophagy pathway, aided by the mitophagy receptor PHB2, for bacterial survival and persistent infection. Moreover, suppression of mitophagy alleviated the pathogenicity of S. Typhimurium. In conclusion, S. Typhimurium infection could be antagonized by targeting the SseJ-PHB2-mediated host mitochondrial autophagy pathway.Abbreviation: ACTB: actin beta; BafA1: bafilomycin A₁; CCCP: carbonyl cyanide m-chlorophenyl hydrazone; co-IP: co-immunoprecipitation; CFU: colony-forming units; COX4/COXIV: cytochrome c oxidase subunit 4; CQ: chloroquine; hpi: h post-bacterial infection; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; Mdivi-1:mitophagy inhibitor mitochondrial division inhibitor 1; MFN2: mitofusin 2; MG132: z-leu-leu-leucinal; MOI: multiplicity of infection; mtDNA: mitochondrial DNA; PBS: phosphate-buffered saline; PGAM5: PGAM family member 5, mitochondrial serine/threonine protein phosphatase; PHB2: prohibitin 2; PINK1: PTEN induced kinase 1; qPCR: quantitative real-time reverse transcription PCR; Roc-A: Rocaglamide A; PRKN/Parkin: parkin RBR E3 ubiquitin protein ligase; SCVs: Salmonella-containing vacuoles; siRNA: small interfering RNA; SPI-2: Salmonella pathogenicity island 2; SseJ: secretion system effector J; S. Typhimurium: Salmonella enterica serovar Typhimurium; S.T-ΔSseJ: SseJ gene-deleted Salmonella Typhimurium strains; S.T-CΔSseJ: SseJ-complemented Salmonella Typhimurium strains; WT: wild-type.