title: Resolving multiple protein-peptide binding events: implication for HLA-DQ2 mediated antigen presentation in celiac disease.
abstract: Techniques that can effectively separate protein-peptide complexes from free peptides have shown great value in major histocompatibility complex (MHC)-peptide binding studies. However, most of the available techniques are limited to measuring the binding of a single peptide to an MHC molecule. As antigen presentation in vivo involves both endogenous ligands and exogenous antigens, the deconvolution of multiple binding events necessitates the implementation of a more powerful technique. Here we show that capillary electrophoresis coupled to fluorescence detection (CE-FL) can resolve multiple MHC-peptide binding events owing to its superior resolution and the ability to simultaneously monitor multiple emission channels. We utilized CE-FL to investigate competition and displacement of endogenous peptides by an immunogenic gluten peptide for binding to HLA-DQ2. Remarkably, this immunogenic peptide could displace CLIP peptides from the DQ2 binding site at neutral but not acidic pH. This unusual ability of the gluten peptide supports a direct loading mechanism of antigen presentation in extracellular environment, a property that could explain the antigenicity of dietary gluten in celiac disease.
authors.affiliation: Department of Chemistry, The Chinese University of Hong Kong, Shatin, Hong Kong, P. R. China.
authors.forename: Jianhao
authors.initials: J
authors.lastname: Wang
authors.forename: Xi
authors.initials: X
authors.lastname: Jin
authors.forename: Jiahui
authors.initials: J
authors.lastname: Liu
authors.forename: Chaitan
authors.initials: C
authors.lastname: Khosla
authors.forename: Jiang
authors.initials: J
authors.lastname: Xia
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation; D002446:Celiac Disease / Q000276:immunology*; D002460:Cell Line; D019075:Electrophoresis, Capillary / Q000295:instrumentation; D004867:Equipment Design; D005453:Fluorescence; D005983:Glutens / Q000737:chemistry / Q000276:immunology*; D006683:HLA-DQ Antigens / Q000276:immunology*; D006801:Humans; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology*
chemical_list: D006683:HLA-DQ Antigens; C053186:HLA-DQ2 antigen; D010455:Peptides; D005983:Glutens