The autoimmune susceptibility gene, PTPN2, restricts expansion of a novel mouse adherent-invasive E. coli

Abstract

Inflammatory bowel disease (IBD) pathogenesis involves significant contributions from genetic and environmental factors. Loss-of-function single-nucleotide polymorphisms (SNPs) in the protein tyrosine phosphatase non-receptor type 2 (PTPN2) gene increase IBD risk and are associated with altered microbiome population dynamics in IBD. Expansion of intestinal pathobionts, such as adherent-invasive E. coli (AIEC), is strongly implicated in IBD pathogenesis as AIEC increases proinflammatory cytokine production and alters tight junction protein regulationsuggesting a potential mechanism of pathogen-induced barrier dysfunction and inflammation. We aimed to determine if PTPN2 deficiency alters intestinal microbiome composition to promote expansion of specific bacteria with pathogenic properties. In mice constitutively lacking Ptpn2, we identified increased abundance of a novel mouse AIEC (mAIEC) that showed similar adherence and invasion of intestinal epithelial cells, but greater survival in macrophages, to the IBD-associated AIEC, LF82. Furthermore, mAIEC caused disease when administered to mice lacking segmented-filamentous bacteria (SFB), and in germ-free mice but only when reconstituted with a microbiome, thus supporting its classification as a pathobiont, not a pathogen. Moreover, mAIEC infection increased the severity of, and prevented recovery from, induced colitis. Although mAIEC genome sequence analysis showed >90% similarity to LF82, mAIEC contained putative virulence genes with >50% difference in gene/protein identities from LF82 indicating potentially distinct genetic features of mAIEC. We show for the first time that an IBD susceptibility gene, PTPN2, modulates the gut microbiome to protect against a novel pathobiont. This study generates new insights into geneenvironment-microbiome interactions in IBD and identifies a new model to study AIEC-host interactions.

T cell protein tyrosine phosphatase protects intestinal barrier function by restricting epithelial tight junction remodeling

“…TCPTP limits claudin-2 by restricting STAT1-mediated transcription of claudin-2 and hepatocyte growth factor activator inhibitor-1, static host-commensal microbe interactions with the epithelium. The observed regional variations in cytokine production were associated with altered relative abundance of cytokine-producing T cell subsets in Tcptp-deficient mice (51). Increased IFN-γ + T cell abundance and serum IFN-γ was consistent with previous studies of these mice, and CD4-specific deletion of TCPTP (24,32,52).…”

Autoimmune susceptibility gene PTPN2 is required for clearance of adherent-invasive Escherichia coli by integrating bacterial uptake and lysosomal defence

“… 50 Therefore, this model might not be optimally suited to study AIEC-host interactions. In contrast, our recently identified m AIEC 27 was effective in invading mouse macrophages since it binds to and enters host cells by using CEACAM1, which is highly expressed in mouse enterocytes and intestinal macrophages. 51 Thus, this novel m AIEC strain might represent a more appropriate strain for studying the effect of AIEC colonisation in mouse models of IBD.…”

“… 29 These cells were exposed to non-invasive E. coli K12, the human LF82 AIEC, or a novel m AIEC recently discovered in our lab. 27 EV-transfected (PTPN2-deficient) macrophages were highly susceptible to LF82 and m AIEC uptake, an effect mirrored in macrophages expressing the PTPN2 loss-of-function variant ( online supplemental figure 1A, B ). Bacterial replication was increased in PTPN2 -deficient and PTPN2 -variant macrophages when compared with macrophages expressing the WT variant ( online supplemental figure 1C ).…”

“…For experiments, K12 (ATCC), LF82 8 and mouse AIEC ( m AIEC) 27 were cultured in Luria-Bertani (LB) medium overnight from frozen stocks, subcultured into fresh LB, harvested in the log-phase, washed in PBS, and macrophages infected at an MOI of 20. After 2 hours, macrophages were washed twice with Gentamycin (100 µg/mL)-containing culture medium and incubated in gentamycin (20 ug/mL)-containing culture medium.…”

“…We previously found that full-body Ptpn2 knockout mice exhibit a significant expansion of a novel mouse AIEC ( m AIEC). 25 The aim of this study was to identify whether loss of PTPN2 activity compromises macrophage-mediated host defences against AIEC and to assess the mechanisms by which loss of PTPN2, or the presence of SNP rs1893217 SNP, compromises the ability of macrophages to clear AIEC infections.…”