The Salmonella T3SS1 effector IpaJ is regulated by ItrA and inhibits the MAPK signaling pathway

Abstract

Invasion plasmid antigen J (IpaJ) is a protein with cysteine protease activity that is present in Salmonella and Shigella species. Salmonella enterica serovar Pullorum uses IpaJ to inhibit the NF-κB pathway and the subsequent inflammatory response, resulting in bacterial survival in host macrophages. In the present study, we performed a DNA pull-down assay and EMSA and identified ItrA, a new DeoR family transcriptional regulator that could control the expression of IpaJ by directly binding to the promoter of ipaJ. The deletion of itrA inhibited the transcription of ipaJ in Salmonella. Tn-Seq revealed that two regulators of Salmonella pathogenicity island 1 (SPI-1), namely HilA and HilD, regulated the secretion of IpaJ. The deletion of hilA, hilD or SPI-1 inhibited the secretion of IpaJ in both cultured medium and Salmonella-infected cells. In contrast, the strain with the deletion of ssrB (an SPI-2 regulator-encoding gene) displayed normal IpaJ secretion, indicating that IpaJ is an effector of the SPI-1-encoded type III secretion system (T3SS1). To further demonstrate the role of IpaJ in host cells, we performed quantitative phosphoproteomics and compared the fold changes in signaling molecules in HeLa cells infected with wild-type S. Pullorum C79-13 with those in HeLa cells infected with the ipaJ-deleted strain C79-13ΔpSPI12. Both phosphoproteomics and Western blot analyses revealed that p-MEK and p-ERK molecules were increased in C79-13ΔpSPI12- and C79-13ΔpSPI12-pipaJ(C45A)-infected cells; and Co-IP assays demonstrated that IpaJ interacts with Ras to reduce its ubiquitination, indicating that IpaJ can inhibit the activation of the MAPK signaling pathway.

Immunity of turbot Induced by inactivated vaccine of Aeromonas salmonicida from the perspective of DNA methylation

“…It was found from the WGBS results that many DMGs were significantly enriched in multiple immune-related pathways, such as MAPK signaling pathway, Wnt signaling pathway. Among them, MAPK signaling pathway plays a key role in apoptosis and the interaction between bacteria and host in cancer and immune system ( 29 , 30 ). At the same time, a large number of immune-related DEGs were screened and analyzed from the transcriptome sequencing results.…”

Mitogen-Activated Protein Kinases (MAPKs) and Enteric Bacterial Pathogens: A Complex Interplay

“…Nevertheless, studies suggested that injected IpaJ inhibits the host NF-κB and the MAPK signaling pathways. IpaJ can prevent the ubiquitination and degradation of IκBα in the NF-κB signaling pathway and inhibit the phosphorylation of MEK and Erk in the MAPK signaling pathway through deubiquitylation and the inhibition of Ras, thereby downregulating proinflammatory responses, cellular growth and differentiation, cell survival, and apoptosis [128]. However, the detailed mechanism by which IpaJ targets the Ras/MAPK pathway remains unknown.…”