Clustering of Class I HLA Oligomers with CD8 and TCR: Three-Dimensional Models Based on Fluorescence Resonance Energy Transfer and Crystallographic Data

摘要: Fluorescence resonance energy transfer (FRET) data, in accordance with lateral mobility measurements, suggested the existence of class I HLA dimers and oligomers at surface live human cells, including B lymphoblast cell line (JY) used present study. Intra- intermolecular epitope distances were measured on JY cells by FRET using fluorophore-conjugated Ag-binding fragments mAbs W6/32 L368 directed against structurally well-characterized heavy light chain epitopes, respectively. Out-of-plane location these epitopes relative to 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 FRET. Computer-simulated docking crystallographic structures epitope-specific fragments, experimentally interepitope as constraints, revealed several sterically allowed FRET-compatible dimeric tetrameric arrangements. Extension model interacting TCR CD8 resulted a supramolecular cluster that may exist physiologically serve functionally significant unit for network CD8-HLA-I complexes providing enhanced signaling efficiency even low MHC-peptide concentrations interface effector APCs.