Abstract
Background Host engulfment protein ELMO1 generates intestinal inflammation following internalization of enteric bacteria. In Shigella, bacterial effector IpgB1 interacts with ELMO1 and promotes bacterial invasion. IpgB1 belongs to the WxxxE effector family, a motif found in several effector of enteric pathogens. Here, we have studied the role of WxxxE effectors, with emphasis on Salmonella SifA and whether it interacts with ELMO1 to regulate inflammation.
Methodology In-silico-analysis of WxxxE effectors was performed using BLAST search and Clustal W program. The interaction of ELMO1 with SifA was assessed by GST pulldown assay and co-immunoprecipitation. ELMO1 knock-out mice, and ELMO1-depleted murine macrophage J774 cell lines were challenged with WT and SifA mutant Salmonella. Bacterial effectors containing the WxxxE motif were transfected in WT and ELMO1-depleted J774 cells to assess the inflammatory cytokines.
Results ELMO1 generates differential pro-inflammatory cytokines between pathogenic and non-pathogenic bacteria. WxxxE motif is present in pathogens and in the TIR domain of host proteins. The C-terminal part of ELMO1 interacts with SifA where WxxxE motif is important for interaction. ELMO1-SifA interaction affects the bacterial colonization, dissemination, and inflammatory cytokines in vivo. Moreover, ELMO1-SifA interaction increases TNF-α and IL-6 production from the macrophage cell line and is associated with enhanced Rac1 activity. ELMO1 also interacts with WxxxE effectors IpgB1, IpgB2, and Map, and induces inflammation after challenge with microbe or microbial ligand.
Conclusion ELMO1 generates a differential response through interaction with the WxxxE motif which is absent in commensals. ELMO1-WxxxE interaction plays a role in bacterial pathogenesis and induction of inflammatory response.
Highlights
ELMO1 generates a differential immune response between enteric pathogens and commensals.
Enteric bacterial effectors containing WxxxE signature motif interact with ELMO1.
The WxxxE effector of Salmonella SifA interacts with the C-terminal part of ELMO1.
ELMO1-SifA interaction increases the inflammatory response in vivo and in vitro.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
$ Another Affiliation: Department of Medical Microbiology and Immunology, Faculty of Medicine, Assiut University, Egypt
Conflict of interest - Each author revealed that they do not have any competing financial and non-financial interests or connections, direct or indirect, or other situations that might raise the question of bias in the work reported or the conclusions, implications, or opinions stated here– including pertinent commercial or other sources of funding.