title: A derivative of wheat germ agglutinin specifically inhibits formyl-peptide-induced polymorphonuclear leukocyte chemotaxis by blocking re-expression (or recycling) of receptors.
abstract: We examined the mechanism of action of a derivative of wheat germ agglutinin (WGA-D) which specifically and irreversibly inhibits N-formyl-methionyl-leucyl-phenylalanine (FMLP)-induced polymorphonuclear leukocyte (PMN) chemotaxis. At a concentration that completely inhibited PMN chemotaxis, WGA-D had no effect on either the uptake or release of [3H]-FMLP by PMN. Similarly, WGA-D did not affect either the short-term binding to, or internalization by, PMN of a fluoresceinated FMLP analog. WGA-D did interfere, however, with the re-expression (or recycling) of FMLP receptors by PMN that had been preincubated with 1 microM FMLP for 10 min at 4 degrees C. This effect was specific for WGA-D, because it was not observed when concanavalin A was used. Scatchard plot analysis of FMLP binding to PMN after receptor re-expression demonstrated that WGA-D-treated PMN had a significant diminution in the number of high affinity receptors. WGA-D-mediated inhibition of FMLP receptor re-expression was associated with inhibition of FMLP-induced PMN chemotaxis, but had no effect on either FMLP-induced PMN superoxide anion generation or degranulation. Studies using [125I]-WGA-D demonstrated that PMN did not internalize WGA-D spontaneously. PMN did internalize [125I]-WGA-D, however, when stimulated with FMLP. Internalization of WGA-D by FMLP-stimulated PMN was rapid, dependent on the concentration of FMLP, and specific. Internalization of [125I]-WGA-D by PMN did not occur when highly purified human C5a, instead of FMLP, was used as a stimulus. Subcellular fractionation studies demonstrated that [125I]-WGA-D and [3H]-FMLP were co-internalized by PMN, and segregated to a compartment co-migrating with Golgi markers. Western blot analysis, using PMN plasma membranes, demonstrated that WGA-D bound to a single membrane glycoprotein that migrated with an apparent m.w. of 62,000. The data indicate that WGA-D, perhaps by binding to the FMLP receptor, inhibits FMLP-induced PMN chemotaxis by blocking the re-expression (or recycling) of a population of receptors required for continuous migration.
mesh_terms: D000328:Adult; D001667:Binding, Competitive; D002634:Chemotaxis, Leukocyte / Q000187:drug effects*; D004705:Endocytosis; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D037102:Lectins / Q000494:pharmacology*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000378:metabolism / Q000494:pharmacology*; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic / Q000032:analysis / Q000187:drug effects / Q000378:metabolism*; D014909:Wheat Germ Agglutinins
chemical_list: D007166:Immunosuppressive Agents; D037102:Lectins; D009842:Oligopeptides; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic; D014909:Wheat Germ Agglutinins; D009240:N-Formylmethionine Leucyl-Phenylalanine; C021642:F-chemotactic peptide