title: Celiac anti-type 2 transglutaminase antibodies induce phosphoproteome modification in intestinal epithelial Caco-2 cells.
abstract: BACKGROUND
  Celiac disease is an inflammatory condition of the small intestine that affects genetically predisposed individuals after dietary wheat gliadin ingestion. Type 2-transglutaminase (TG2) activity seems to be responsible for a strong autoimmune response in celiac disease, TG2 being the main autoantigen. Several studies support the concept that celiac anti-TG2 antibodies may contribute to disease pathogenesis. Our recent findings on the ability of anti-TG2 antibodies to induce a rapid intracellular mobilization of calcium ions, as well as extracellular signal-regulated kinase phosphorylation, suggest that they potentially act as signaling molecules. In line with this concept, we have investigated whether anti-TG2 antibodies can induce phosphoproteome modification in an intestinal epithelial cell line.
  
  
  RESULTS
  We studied phosphoproteome modification in Caco-2 cells treated with recombinant celiac anti-TG2 antibodies. We performed a two-dimensional electrophoresis followed by specific staining of phosphoproteins and mass spectrometry analysis of differentially phosphorylated proteins. Of 14 identified proteins (excluding two uncharacterized proteins), three were hypophosphorylated and nine were hyperphosphorylated. Bioinformatics analyses confirmed the presence of phosphorylation sites in all the identified proteins and highlighted their involvement in several fundamental biological processes, such as cell cycle progression, cell stress response, cytoskeletal organization and apoptosis.
  
  
  CONCLUSIONS
  Identification of differentially phosphorylated proteins downstream of TG2-antibody stimulation suggests that in Caco-2 cells these antibodies perturb cell homeostasis by behaving as signaling molecules. We hypothesize that anti-TG2 autoantibodies may destabilize the integrity of the intestinal mucosa in celiac individuals, thus contributing to celiac disease establishment and progression. Since several proteins here identified in this study were already known as TG2 substrates, we can also suppose that transamidating activity and differential phosphorylation of the same targets may represent a novel regulatory mechanism whose relevance in celiac disease pathogenesis is still unexplored.
authors.affiliation: Department of Chemistry and Biology, University of Salerno, Salerno, Italy.
authors.forename: Gaetana
authors.initials: G
authors.lastname: Paolella
authors.affiliation: Department of Chemistry and Biology, University of Salerno, Salerno, Italy ; European Laboratory for the Investigation of Food-Induced Diseases (ELFID), University "Federico II", Naples, Italy.
authors.forename: Ivana
authors.initials: I
authors.lastname: Caputo
authors.affiliation: Department of Chemistry and Biology, University of Salerno, Salerno, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Marabotti
authors.affiliation: Department of Chemistry and Biology, University of Salerno, Salerno, Italy.
authors.forename: Marilena
authors.initials: M
authors.lastname: Lepretti
authors.affiliation: Proteomics and Mass Spectrometry Laboratory, ISPAAM, National Research Council, Naples, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Salzano
authors.affiliation: Proteomics and Mass Spectrometry Laboratory, ISPAAM, National Research Council, Naples, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Scaloni
authors.affiliation: Department of Molecular Medicine and Medical Biotechnologies, University "Federico II", Naples, Italy ; CEINGE Biotecnologie Avanzate, Naples, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Vitale
authors.affiliation: Department of Molecular Medicine and Medical Biotechnologies, University "Federico II", Naples, Italy ; CEINGE Biotecnologie Avanzate, Naples, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Zambrano
authors.affiliation: Department of Health Sciences and IRCAD, University of Eastern Piedmont, Novara, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Sblattero
authors.affiliation: Department of Chemistry and Biology, University of Salerno, Salerno, Italy ; European Laboratory for the Investigation of Food-Induced Diseases (ELFID), University "Federico II", Naples, Italy.
authors.forename: Carla
authors.initials: C
authors.lastname: Esposito
mesh_terms: D000906:Antibodies / Q000276:immunology / Q000494:pharmacology*; D015153:Blotting, Western; D018938:Caco-2 Cells; D002446:Celiac Disease / Q000201:enzymology*; D019295:Computational Biology; D015180:Electrophoresis, Gel, Two-Dimensional; D019204:GTP-Binding Proteins / Q000276:immunology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007413:Intestinal Mucosa / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D040901:Proteomics; D011503:Transglutaminases / Q000276:immunology*
chemical_list: D000906:Antibodies; D010750:Phosphoproteins; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins