The β4GalT1 affects the fibroblast-like synoviocytes invasion in rheumatoid arthritis by modifying N-linked glycosylation of CXCR3

OBJECTIVE

The level of β-1,4-galactosyltransferase 1 (β4GalT1) is up-regulated in collagen-induced arthritis (CIA) mice. It is reported that CXC chemokine receptor 3 (CXCR3) can enhance the invasiveness of fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA). This study aims to investigate the specific mechanism of β4GalT1 and relationship between β4GalT1 and CXCR3 in RA.

METHODS

The model of CIA mice was established to explore the role of β4GalT1. The N-glycosylation of CXCR3 was detected by mass spectrometry and western-blot. The interaction between β4GalT1 and CXCR3 was tested by immunoprecipitation. The truncted MMP-1 was detected by ELISA. Flow cytometry analysis was applied to measure ligand-receptor interaction between CXCR3 and CXCL10.

RESULTS

β4GalT1 can promote the inflammatory process of arthritis. CXCR3 was N-glycosylated and its glycosylation regulated by β4GalT1. β4GalT1 can enhance the invasiveness of FLS by modifying CXCR3. N-glycosylation of CXCR3 influences the ligand-receptor interaction between CXCR3 and CXCL10.

CONCLUSIONS

β4GalT1 can regulate N-glycans of CXCR3 in RA. N-glycans of CXCR3 affects CXCL10/CXCR3 ligand-binding which enhancing FLS invasion.

Decreased severity of experimental autoimmune arthritis in peptidylarginine deiminase type 4 knockout mice

Background

Peptidylarginine deiminase type 4 (PADI4) has been identified as a susceptibility gene for rheumatoid arthritis (RA) by genome-wide association studies. PADI4 is highly expressed in the bone marrow, macrophages, neutrophils, and monocytes. Peptidyl citrulline is an interesting molecule in RA because it is a target antigen for anti-citrullinated peptide antibodies, and only PADs (translated proteins from PADI genes) can provide peptidyl citrulline via the modification of protein substrates. The aim of this study was to evaluate the importance of the PADI4 gene in the progression of RA.

Methods

We generated Padi4 knockout (Padi4^−/−) DBA1J mice. The Padi4^−/− DBA1J and wild-type mice were immunized with bovine type II collagen (CII) to develop collagen-induced arthritis (CIA). The expression of various inflammatory cytokines and Padi genes in immune cells was detected by the real-time TaqMan assay. Cytokine concentrations in sera were measured by enzyme-linked immunosorbent assays. Localization of the PAD4 and PAD2 proteins was indicated by immunohistochemistry.

Results

We demonstrated that the clinical disease score was significantly decreased in the Padi4^−/− mice and Padi4 expression was induced by CII immunization. In the Padi4^−/− mice, serum anti-type II collagen (CII) immunoglobulin M (IgM), IgG, and inflammatory cytokine levels were significantly decreased compared with those in the wild-type mice. Padi2 expression was induced in the immune cells of the Padi4^−/− mice as a compensation for the defect in Padi4.

Conclusions

Padi4 affected disease severity in the CIA mice and was involved in the enhancement of the collagen-initiated inflammatory responses.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-1055-2) contains supplementary material, which is available to authorized users.