Lymphocyte function-associated antigen 1 (LFA-1, CD11a/CD18, αLβ2-integrin) and its ligands are essential for adhesion between T-cells and antigen-presenting cells, formation of the immunological synapse, and other immune cell interactions. LFA-1 function is regulated through conformational changes that include the modulation of ligand binding affinity and molecular extension. However, the relationship between molecular conformation and function is unclear. Here fluorescence resonance energy transfer (FRET) with new LFA-1-specific fluorescent probes showed that triggering of the pathway used for T-cell activation induced rapid unquenching of the FRET signal consistent with extension of the molecule. Analysis of the FRET quenching at rest revealed an unexpected result that can be interpreted as a previously unknown LFA-1 conformation.
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This work was supported by National Institutes of Health Grants HL081062 and U54 MH074425-03S2 (to L.A.S.), Leukemia and Lymphoma Society Grant 7388-06 (to L.A.S.), and the Oxnard Foundation (to A.C.). Images were generated in the University of New Mexico and Cancer Center Fluorescence Microscopy Shared Resource, funded as detailed on hsc.unm.edu/crtc/microscopy/acknowledgement.shtml.
Chigaev, Alexandre; Smagley, Yelena; Haynes, Mark K.; Ursu, Oleg; Bologa, Cristian G.; Halip, Liliana; Oprea, Tudor; Waller, Anna; Carter, Mark B.; Zhang, Yinan; Wang, Wei; Buranda, Tione; and Sklar, Larry A., "FRET Detection of Lymphocyte Function-Associated Antigen-1 Conformational Extension" (2015). Pharmaceutical Sciences Faculty Publications. 42.