Objective Salmonella enterica infections can lead to Reactive Arthritis (ReA), which can exhibit an association with human leucocyte antigen (HLA)-B*27:05, a molecule prone to misfolding and initiation of the unfolded protein response (UPR). This study examined how HLA-B*27:05 expression and the UPR affect the Salmonella life-cycle within epithelial cells.
Methods Isogenic epithelial cell lines expressing two copies of either HLA-B*27:05 and a control HLA-B*35:01 heavy chain (HC) were generated to determine the effect on the Salmonella infection life-cycle. A cell line expressing HLA-B*27:05.HC physically linked to the light chain beta-2-microglobulin and a specific peptide (referred to as a single chain trimer, SCT) was also generated to determine the effects of HLA-B27 folding status on S. enterica life-cycle. XBP-1 venus and AMP dependent Transcription Factor (ATF6)-FLAG reporters were used to monitor UPR activation in infected cells. Triacin C was used to inhibit de novo lipid synthesis during UPR, and confocal imaging of ER tracker stained membrane allowed quantification of glibenclamide-associated membrane.
Results S. enterica demonstrated enhanced replication with an altered cellular localisation in the presence of HLA-B*27:05.HC but not in the presence of HLA-B*27:05.SCT or HLA-B*35:01. HLA-B*27:05.HC altered the threshold for UPR induction. Salmonella activated the UPR and required XBP-1 for replication, which was associated with endoreticular membrane expansion and lipid metabolism.
Conclusions HLA-B27 misfolding and a UPR cellular environment are associated with enhanced Salmonella replication, while Salmonella itself can activate XBP-1 and ATF6. These data provide a potential mechanism linking the life-cycle of Salmonella with the physicochemical properties of HLA-B27 and cellular events that may contribute to ReA pathogenesis. Our observations suggest that the UPR pathway maybe targeted for future therapeutic intervention.
- ankylosing spondylitis
- reactive arthritis
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DN and SJP are joint senior authors.
Handling editor Josef S Smolen
Contributors All authors contributed to experimental design and to performing the experiments and generating data. All authors contributed to the construction of the manuscript. ANA: contributed to the planning, designing of experiments, interpretation of data and writing of the manuscript. IL: contributed and performed the biochemical analysis of the respective cell lines employed throughout the study, and contributed to the writing of the manuscript. JK-V: contributed to planning, designing and interpretation of the data collated by the microscopic screening, and contributed to the writing of the manuscript. TI: contributed to the design and the use of the UPR reporters. MT: contributed to the microscopic analysis. KM: contributed to the cellular and biochemical analysis of the cell lines employed throughout the study. SA: contributed to the design and generation of the constructs used in the study. NB: contributed to the cellular analysis of the cell lines employed throughout the study. PB: contributed to the cellular and biochemical analyses of the cell lines employed throughout the study and contributed to the writing of the manuscript. MB-E: contributed to the experimental design, data interpretation and writing of the manuscript. KG: contributed to the generation of the constructs and cell lines used throughout the study, data interpretation and writing of the manuscript. DN: contributed to the generation of the constructs and cell lines used throughout the study, data interpretation, experimental design and writing of the manuscript. SJP: contributed to the data interpretation, experimental design and writing of the manuscript, and contributed to the biochemical analysis of the cell lines employed throughout the study.
Funding ANA was funded by ARUK Fellowships Non-Clinical Career DevelopmentFellowship (ref no: 18440). IL was funded by an ARUK PhD studentship (ref no: 17868). ANA and SJP were also in part funded by ARUK (grant 21261).
Competing interests None declared.
Patient consent Not required.
Ethics approval All experiments and procedures were performed as approved by the local ethics.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All data are available on request to firstname.lastname@example.org.
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