title: Susceptibility to HLA-DM protein is determined by a dynamic conformation of major histocompatibility complex class II molecule bound with peptide.
abstract: HLA-DM mediates the exchange of peptides loaded onto MHCII molecules during antigen presentation by a mechanism that remains unclear and controversial. Here, we investigated the sequence and structural determinants of HLA-DM interaction. Peptides interacting nonoptimally in the P1 pocket exhibited low MHCII binding affinity and kinetic instability and were highly susceptible to HLA-DM-mediated peptide exchange. These changes were accompanied by conformational alterations detected by surface plasmon resonance, SDS resistance assay, antibody binding assay, gel filtration, dynamic light scattering, small angle x-ray scattering, and NMR spectroscopy. Surprisingly, all of those changes could be reversed by substitution of the P9 pocket anchor residue. Moreover, MHCII mutations outside the P1 pocket and the HLA-DM interaction site increased HLA-DM susceptibility. These results indicate that a dynamic MHCII conformational determinant rather than P1 pocket occupancy is the key factor determining susceptibility to HLA-DM-mediated peptide exchange and provide a molecular mechanism for HLA-DM to efficiently target unstable MHCII-peptide complexes for editing and exchange those for more stable ones.
authors.affiliation: From the Program in Immunology and Microbiology and.
authors.forename: Liusong
authors.initials: L
authors.lastname: Yin
authors.affiliation: From the Program in Immunology and Microbiology and.
authors.forename: Peter
authors.initials: P
authors.lastname: Trenh
authors.affiliation: Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts 01605.
authors.forename: Abigail
authors.initials: A
authors.lastname: Guce
authors.affiliation: the Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany, and.
authors.forename: Marek
authors.initials: M
authors.lastname: Wieczorek
authors.affiliation: the Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany, and.
authors.forename: Sascha
authors.initials: S
authors.lastname: Lange
authors.affiliation: the Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany, and.
authors.forename: Jana
authors.initials: J
authors.lastname: Sticht
authors.affiliation: the Department of Pediatrics, Program in Immunology, Stanford University Medical Center, Stanford, California 94305.
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
authors.affiliation: Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts 01605.
authors.forename: Marissa
authors.initials: M
authors.lastname: Bylsma
authors.affiliation: the Department of Pediatrics, Program in Immunology, Stanford University Medical Center, Stanford, California 94305.
authors.forename: Elizabeth D
authors.initials: ED
authors.lastname: Mellins
authors.affiliation: the Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany, and.
authors.forename: Christian
authors.initials: C
authors.lastname: Freund
authors.affiliation: From the Program in Immunology and Microbiology and Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, lawrence.stern@umassmed.edu.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Stern
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000737:chemistry / Q000276:immunology*; D006681:HLA-D Antigens / Q000737:chemistry / Q000276:immunology*; D006801:Humans; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry / Q000276:immunology*
chemical_list: D000939:Epitopes; D006681:HLA-D Antigens; C084245:HLA-DM antigens; D010455:Peptides
keywords: Antigen Presentation; Conformational Change; DM Susceptibility; Enzyme Kinetics; Enzyme Mechanism; Major Histocompatibility Complex (MHC); Protein-Protein Interaction