title: A modified FCCS procedure applied to Ly49A-MHC class I cis-interaction studies in cell membranes.
abstract: The activity of natural killer (NK) cells is regulated by a fine-tuned balance between activating and inhibitory receptors. Dual-color fluorescence cross-correlation spectroscopy (FCCS) was used to directly demonstrate a so-called cis-interaction between a member of the inhibitory NK cell receptor family Ly49 (Ly49A), and its ligand, the major histocompatibility complex (MHC) class I, within the plasma membrane of the same cell. By a refined FCCS model, calibrated by positive and negative control experiments on cells from the same lymphoid cell line, concentrations and diffusion coefficients of free and interacting proteins could be determined on a collection of cells. Using the intrinsic intercellular variation of their expression levels for titration, it was found that the fraction of Ly49A receptors bound in cis increase with increasing amounts of MHC class I ligand. This increase shows a tendency to be more abrupt than for a diffusion limited - three dimensional bimolecular reaction, which most likely reflects the two-dimensional confinement of the reaction. For the Ly49A- MHC class I interaction it indicates that within a critical concentration range the local concentration level of MHC class I can provide a distinct regulation mechanism of the NK cell activity.
authors: Experimental Biomolecular Physics, Department of Applied Physics, Royal Institute of Technology, AlbaNova University Center, Stockholm, Sweden.
authors: Johan
authors: J
authors: Strömqvist
authors: Sofia
authors: S
authors: Johansson
authors: Lei
authors: L
authors: Xu
authors: Yu
authors: Y
authors: Ohsugi
authors: Katja
authors: K
authors: Andersson
authors: Hideki
authors: H
authors: Muto
authors: Masataka
authors: M
authors: Kinjo
authors: Petter
authors: P
authors: Höglund
authors: Jerker
authors: J
authors: Widengren
mesh_terms: D000483:Alleles; D000818:Animals; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D002470:Cell Survival; D004058:Diffusion; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006680:HLA Antigens / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D055650:NK Cell Lectin-Like Receptor Subfamily A / Q000378:metabolism*; D011485:Protein Binding; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D006680:HLA Antigens; D055650:NK Cell Lectin-Like Receptor Subfamily A; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins