f-chemotactic-peptide-fluorescein and oxophenylarsine

High resolution kinetic data of the binding of fluorescent peptide to the N-formyl peptide receptor of neutrophils at 37 degrees C has allowed for the development of a ligand binding model that predicts statistically larger binding rate constants than those previously reported for intact neutrophils. The new model accounts for ligand association and dissociation, receptor up-regulation, ligand-receptor complex internalization, a change in receptor affinity, and the quenching of internalized fluorescent ligand. We determined that receptor up-regulation is both agonist- and temperature-induced and is inhibited by both phenylarsine oxide and pertussis toxin treatment. Model fits of ligand association to pertussis toxin-treated cells show that while receptor up-regulation was inhibited, rate constants for ligand binding, receptor affinity conversion, and internalization of ligand-receptor complexes were unaffected. Results suggest Gi-protein-mediated receptor up-regulation and Gi-protein-independent receptor affinity conversion. Simulation of ligand infusion using our model gives insight into the quantitative and dynamic relationship between the low affinity ligand-receptor complex and the actin polymerization response.

Topics: Amino Acid Sequence; Arsenicals; Fluoresceins; Humans; In Vitro Techniques; Kinetics; Ligands; Models, Biological; Molecular Sequence Data; Neutrophils; Oligopeptides; Pertussis Toxin; Receptors, Formyl Peptide; Receptors, Immunologic; Receptors, Peptide; Temperature; Up-Regulation; Virulence Factors, Bordetella