Cross linking to tissue transglutaminase and collagen favours gliadin toxicity in coeliac disease

Background and aims: Intestinal inflammation in coeliac disease is driven by the gluten fraction of wheat proteins. Deamidation or cross linking of gluten peptides by tissue transglutaminase (dagger TG), the coeliac disease autoantigen, creates potent T cell stimulatory peptides. Therefore, our aim was to identify the reaction patterns of gluten peptides, intestinal extracellular matrix proteins, and dagger TG. Methods: dagger TG activity was analysed by incorporation of monodansyl cadaverine into gliadins. Fluorescence labelled dagger TG reactive short gliadin peptides were used to demonstrate their deamidation and explore their cross linking patterns with dagger TG itself or extracellular matrix proteins. Patient sera and controls were checked for autoantibodies to matrix proteins. Results: Gliadins alpha 1-alpha 11, gamma 1-gamma 6, omega 1-omega 3, and omega 5 were substrates for dagger TG. dagger TG catalysed the cross linking of gliadin peptides with interstitial collagen types I, III, and VI. Coeliac patients showed increased antibody titres against the collagens I, III, V, and VI. Conclusions: dagger TG formed high molecular weight complexes with all tested gliadins. As all tested gliadins were substrates for dagger TG, the dagger TG catalysed modifications were not restricted to single gliadin types and epitopes. Furthermore, haptenisation and long term immobilisation of gliadin peptides by dagger TG catalysed binding to abundant extracellular matrix proteins could be instrumental in the perpetuation of intestinal inflammation and some associated autoimmune diseases in coeliac disease.