title: Structural Basis for Antigen Recognition by Transglutaminase 2-specific Autoantibodies in Celiac Disease.
abstract: Antibodies to the autoantigen transglutaminase 2 (TG2) are a hallmark of celiac disease. We have studied the interaction between TG2 and an anti-TG2 antibody (679-14-E06) derived from a single gut IgA plasma cell of a celiac disease patient. The antibody recognizes one of four identified epitopes targeted by antibodies of plasma cells of the disease lesion. The binding interface was identified by small angle x-ray scattering, ab initio and rigid body modeling using the known crystal structure of TG2 and the crystal structure of the antibody Fab fragment, which was solved at 2.4 Å resolution. The result was confirmed by testing binding of the antibody to TG2 mutants by ELISA and surface plasmon resonance. TG2 residues Arg-116 and His-134 were identified to be critical for binding of 679-14-E06 as well as other epitope 1 antibodies. In contrast, antibodies directed toward the two other main epitopes (epitopes 2 and 3) were not affected by these mutations. Molecular dynamics simulations suggest interactions of 679-14-E06 with the N-terminal domain of TG2 via the CDR2 and CDR3 loops of the heavy chain and the CDR2 loop of the light chain. In addition there were contacts of the framework 3 region of the heavy chain with the catalytic domain of TG2. The results provide an explanation for the biased usage of certain heavy and light chain gene segments by epitope 1-specific antibodies in celiac disease.
authors.affiliation: From the Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital, N-0372 Oslo, Norway and.
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.affiliation: From the Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital, N-0372 Oslo, Norway and.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Hnida
authors.affiliation: European Molecular Biology Laboratory, Hamburg Outstation, D-22607 Hamburg, Germany.
authors.forename: Melissa Ann
authors.initials: MA
authors.lastname: Graewert
authors.affiliation: From the Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital, N-0372 Oslo, Norway and.
authors.forename: Jan Terje
authors.initials: JT
authors.lastname: Andersen
authors.affiliation: From the Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital, N-0372 Oslo, Norway and.
authors.forename: Rasmus
authors.initials: R
authors.lastname: Iversen
authors.affiliation: European Molecular Biology Laboratory, Hamburg Outstation, D-22607 Hamburg, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Tuukkanen
authors.affiliation: European Molecular Biology Laboratory, Hamburg Outstation, D-22607 Hamburg, Germany.
authors.forename: Dmitri
authors.initials: D
authors.lastname: Svergun
authors.affiliation: From the Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital, N-0372 Oslo, Norway and l.m.sollid@medisin.uio.no.
authors.forename: Ludvig M
authors.initials: LM
authors.lastname: Sollid
mesh_terms: D001323:Autoantibodies / Q000737:chemistry / Q000276:immunology*; D002446:Celiac Disease / Q000201:enzymology* / Q000235:genetics / Q000276:immunology*; D000939:Epitopes / Q000737:chemistry / Q000276:immunology; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry / Q000276:immunology*; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D053838:Scattering, Small Angle; D020349:Surface Plasmon Resonance; D011503:Transglutaminases / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D014961:X-Ray Diffraction
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D007140:Immunoglobulin Fab Fragments; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins
keywords: antibody; celiac disease; epitope mapping; mutagenesis; small-angle x-ray scattering (SAXS); surface plasmon resonance (SPR); transglutaminase