title: Regulation of N-formyl-methionyl-leucyl-phenylalanine receptor recycling by surface membrane neutral endopeptidase-mediated degradation of ligand.
abstract: Neutrophil responses to alpha-N-formyl-L-Met-L-Leu-L-Phe (fMLF) are modulated by inhibitors of surface membrane neutral endopeptidase (NEP), such as phosphoramidon (PPAD). Because receptor recycling is presumably required for a sustained cellular response, the effect of PPAD on receptor reexpression was examined. After down-regulation of surface fMLF receptors by fMLF, PPAD blocked the normal reexpression of surface receptors in a manner that was related to the time of prior exposure to fMLF. Internalized fML[3H]F was hydrolyzed by NEP at a rate comparable to the rate of receptor reexpression at the cell surface, suggesting that ligand hydrolysis is rate limiting. To test this hypothesis, cells were incubated with fluorescein-labeled formyl-Met-Leu-Phe-Nle-Tyr-Lys at 15 degrees C. After binding was complete, but before internalization of receptor-ligand complexes, high-affinity antifluorescein antibody F(ab')2 fragments were added and the cells incubated at 37 degrees C for 60 min in the presence of PPAD. Under these conditions, the inhibitory effects of PPAD were largely reversed and nonimmune F(ab')2 fragments were without effect.
authors.affiliation: Department of Biochemistry, University of Texas Health Center at Tyler 75710, USA.
authors.forename: R G
authors.initials: RG
authors.lastname: Painter
authors.forename: M L
authors.initials: ML
authors.lastname: Aiken
mesh_terms: D000595:Amino Acid Sequence; D000906:Antibodies / Q000378:metabolism / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology / Q000648:ultrastructure; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000201:enzymology; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D006020:Glycopeptides / Q000494:pharmacology; D006801:Humans; D019272:Leukocyte Elastase; D008024:Ligands; D008969:Molecular Sequence Data; D009113:Muramidase / Q000378:metabolism; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000378:metabolism / Q000494:pharmacology; D015260:Neprilysin / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D010196:Pancreatic Elastase / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D017463:Receptors, Complement 3b / Q000187:drug effects / Q000502:physiology; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology*; D018000:Receptors, Peptide / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D000906:Antibodies; D006020:Glycopeptides; D008024:Ligands; D011480:Protease Inhibitors; D017463:Receptors, Complement 3b; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic; D018000:Receptors, Peptide; D009240:N-Formylmethionine Leucyl-Phenylalanine; D009113:Muramidase; D010196:Pancreatic Elastase; D019272:Leukocyte Elastase; D015260:Neprilysin; C008890:phosphoramidon