title: Thioredoxin is involved in endothelial cell extracellular transglutaminase 2 activation mediated by celiac disease patient IgA.
abstract: OBJECTIVE
  To investigate the role of thioredoxin (TRX), a novel regulator of extracellular transglutaminase 2 (TG2), in celiac patients IgA (CD IgA) mediated TG2 enzymatic activation.
  
  
  METHODS
  TG2 enzymatic activity was evaluated in endothelial cells (HUVECs) under different experimental conditions by ELISA and Western blotting. Extracellular TG2 expression was studied by ELISA and immunofluorescence. TRX was analysed by Western blotting and ELISA. Serum immunoglobulins class A from healthy subjects (H IgA) were used as controls. Extracellular TG2 enzymatic activity was inhibited by R281. PX12, a TRX inhibitor, was also employed in the present study.
  
  
  RESULTS
  We have found that in HUVECs CD IgA is able to induce the activation of extracellular TG2 in a dose-dependent manner. Particularly, we noted that the extracellular modulation of TG2 activity mediated by CD IgA occurred only under reducing conditions, also needed to maintain antibody binding. Furthermore, CD IgA-treated HUVECs were characterized by a slightly augmented TG2 surface expression which was independent from extracellular TG2 activation. We also observed that HUVECs cultured in the presence of CD IgA evinced decreased TRX surface expression, coupled with increased secretion of the protein into the culture medium. Intriguingly, inhibition of TRX after CD IgA treatment was able to overcome most of the CD IgA-mediated effects including the TG2 extracellular transamidase activity.
  
  
  CONCLUSIONS
  Altogether our findings suggest that in endothelial cells CD IgA mediate the constitutive activation of extracellular TG2 by a mechanism involving the redox sensor protein TRX.
authors.affiliation: Tampere Center for Child Health Research, University of Tampere and Tampere University Hospital, Tampere, Finland.
authors.forename: Cristina
authors.initials: C
authors.lastname: Antonella Nadalutti
authors.forename: Ilma Rita
authors.initials: IR
authors.lastname: Korponay-Szabo
authors.forename: Katri
authors.initials: K
authors.lastname: Kaukinen
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Wang
authors.forename: Martin
authors.initials: M
authors.lastname: Griffin
authors.forename: Markku
authors.initials: M
authors.lastname: Mäki
authors.forename: Katri
authors.initials: K
authors.lastname: Lindfors
mesh_terms: D002446:Celiac Disease / Q000097:blood / Q000201:enzymology* / Q000276:immunology*; D042783:Endothelial Cells / Q000276:immunology*; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000276:immunology* / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood / Q000276:immunology*; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D013879:Thioredoxins / Q000276:immunology*; D011503:Transglutaminases / Q000276:immunology* / Q000378:metabolism
chemical_list: D007070:Immunoglobulin A; C491203:TXN protein, human; D013879:Thioredoxins; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins