Autoantibodies from patients with celiac disease inhibit transglutaminase 2 binding to heparin/heparan sulfate and interfere with intestinal epithelial cell adhesion

Abstract

Autoantibodies from patients with celiac disease (CD) can influence transglutaminase 2 (TG2) activity and its cellular functions, but the exact mechanisms have remained unknown. Our objective was to study whether autoantibodies could modulate TG2 binding to heparin/heparan sulfate (HS) and intestinal epithelial cell attachment to fibronectin-TG2 matrix. Anti-TG2 antibodies were purified by TG2 affinity chromatography from sera of patients with active CD. Serum and antibody effects on TG2 binding to heparin/HS, on transamidase activity of TG2, as well as on Caco-2 cell attachment to fibronectin-TG2 matrix were assessed using microplate assays. Both sera and purified anti-TG2 antibodies from CD patients with high anti-TG2 IgA levels reduced TG2 binding to heparin/HS as compared with those with low anti-TG2 IgA or controls. There was a negative correlation between anti-TG2 IgA levels and TG2 binding to heparin/HS. Treatment of fibronectin-TG2 coated wells with CD patients' sera or purified anti-TG2 antibodies reduced attachment of Caco-2 cells onto the plate as compared with the control samples. The effect of CD patients' antibodies on Caco-2 cell attachment to fibronectin-TG2 matrix occurred independently of the inhibition of cell adhesion by Arg-Gly-Asp sequence containing peptides. Anti-TG2 autoantibodies had no effect on transamidase activity of TG2 in vitro. We suggest that modulation of adhesion function of TG2 by autoantibodies from patients with CD could be related to the inhibition of TG2 binding to HS residues of cell surface proteoglycans and could have possible implications for CD pathogenesis.

Physiological, pathological, and structural implications of non-enzymatic protein–protein interactions of the multifunctional human transglutaminase 2

“…Some of the biological effects include (a) inhibition of cell adhesion and migration, most probably by modulating the heparin sulfate proteoglycan binding site [176] and by enhancing the expression of matrix metallo-proteases, (b) inhibition of epithelial cell differentiation by interfering with TG2 mediated TGF-b1 activation [177], (c) inhibition of several steps in angiogenesis [178], and (d) increasing the permeability of blood-brain barrier.…”

Transglutaminases: Expression in Kidney and Relation to Kidney Fibrosis

“…HS chains have also high affinity binding for TG2 Lortat-Jacob et al 2012) which is associated with the HS chains of syndecan-4 in a variety of cell types Lortat-Jacob et al 2012;Nadella et al 2015;Wang et al 2011Teesalu et al 2012). HS proteoglycans have a physiopathological role in the kidney and have also been suggested to modulate TG2 trafficking in the kidney ).…”

“…Studies with the application of the HS blocking agent Surfen (Schuksz et al 2008) clearly showed reduced extracellular TG2 ), suggesting that if specific interference with TG2-syndecan 4 interactions could be achieved, then it would also serve as a therapeutic intervention site. Several HS binding sites within TG2 have been proposed (Lortat-Jacob et al 2012;Teesalu et al 2012). Our group have identified two distant basic amino acid clusters, RRWK (262-265) and KQKRK (598-602) which would come together to form a conformationally dependent high affinity binding site (Lortat-Jacob et al 2012).…”

Transglutaminase 2 and Transglutaminase 2 Autoantibodies in Celiac Disease: a Review

“…In addition, TG2 antibodies derived from celiac patients have been demonstrated to induce proliferation of intestinal epithelial cells [160]. Further, celiac patient sera or purified anti-TG2 antibodies are able to reduce the attachment of epithelial cells to the TG2-fibronectin matrix [161]. Moreover, treatment of intestinal epithelial cells with sera from celiac patients has been reported to increase the transepithelial permeability of these cells [162].…”