Clustering of class I HLA oligomers with CD8 and TCR: three-dimensional models based on fluorescence resonance energy transfer and crystallographic data.
Fluorescence resonance energy transfer (FRET) data, in accordance with lateral mobility measurements, suggested the existence of class I HLA dimers and oligomers at the surface of live human cells, including the B lymphoblast cell line (JY) used in the present study. Intra- and intermolecular class I HLA epitope distances were measured on JY B cells by FRET using fluorophore-conjugated Ag-binding fragments of mAbs W6/32 and L368 directed against structurally well-characterized heavy and light chain epitopes, respectively. Out-of-plane location of these epitopes relative to the membrane-bound BODIPY-PC (2-(4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-1-hexadecanoyl-sn-glycero-3-phosphocholine) was also determined by FRET. Computer-simulated docking of crystallographic structures of class I HLA and epitope-specific Ag-binding fragments, with experimentally determined interepitope and epitope to cell surface distances as constraints, revealed several sterically allowed and FRET-compatible class I HLA dimeric and tetrameric arrangements. Extension of the tetrameric class I HLA model with interacting TCR and CD8 resulted in a model of a supramolecular cluster that may exist physiologically and serve as a functionally significant unit for a network of CD8-HLA-I complexes providing enhanced signaling efficiency even at low MHC-peptide concentrations at the interface of effector and APCs.
Gáspár
R
R
Department of Biophysics, Biophysics Research Group of the Hungarian Academy of Sciences, University of Debrecen, Medical and Health Science Center, Debrecen, Hungary. gaspar@jaguar.dote.hu
Bagossi
P
P
Bene
L
L
Matkó
J
J
Szöllosi
J
J
Tozsér
J
J
Fésüs
L
L
Waldmann
T A
TA
Damjanovich
S
S
D000938:Antigen-Presenting Cells / Q000737:chemistry / Q000276:immunology; D001402:B-Lymphocytes / Q000737:chemistry / Q000276:immunology; D016827:CD8 Antigens / Q000737:chemistry*; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000737:chemistry / Q000276:immunology; D003198:Computer Simulation; D018360:Crystallography, X-Ray / Q000379:methods; D004735:Energy Transfer / Q000276:immunology*; D018985:Epitopes, B-Lymphocyte / Q000737:chemistry; D006680:HLA Antigens / Q000737:chemistry*; D015789:HLA-A2 Antigen / Q000737:chemistry; D015395:Histocompatibility Antigens Class I / Q000737:chemistry*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry; D008958:Models, Molecular; D010449:Peptide Mapping; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods; D001613:beta 2-Microglobulin / Q000737:chemistry
D016827:CD8 Antigens; D018985:Epitopes, B-Lymphocyte; D006680:HLA Antigens; D015789:HLA-A2 Antigen; D015395:Histocompatibility Antigens Class I; D007140:Immunoglobulin Fab Fragments; D011948:Receptors, Antigen, T-Cell; D001613:beta 2-Microglobulin