title: A serine protease triggers the initial step of transmembrane signalling in cytotoxic T cells.
abstract: We report here by using stopped-flow fluorometry with three different fluorescent probes that a serine protease triggers the initial step of transmembrane signalling in cytotoxic T cells. When cytotoxic T cells (mouse LC7, H-2b anti H-2d) bound to the specific target cells (mouse mastocytoma P815, H-2d), cytotoxic T cells first increased their membrane fluidity, and calcium then was released from intracellular stores. After that, there was a calcium influx from the external medium into the T cells. All of these steps, however, were blocked by serine protease inhibitors (soybean trypsin inhibitor, N alpha-p-tosyl-L-lysine chloromethyl ketone and tosylphenylalanyl chloromethyl ketone). Bovine pancreatic trypsin and chymotrypsin in the external medium mimicked the signalling events which were triggered by the serine protease on the T cell surfaces. From the reaction time (within 1 s) and its specificity, this serine protease in cytotoxic T cells was considered to be different from a protease which works at the killing stage.
mesh_terms: D000818:Animals; D002450:Cell Communication; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D010450:Endopeptidases / Q000378:metabolism*; D051379:Mice; D010954:Plasmacytoma / Q000276:immunology; D012697:Serine Endopeptidases; D013050:Spectrometry, Fluorescence; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000502:physiology
chemical_list: D010450:Endopeptidases; D012697:Serine Endopeptidases