Receptor up-regulation, internalization, and interconverting receptor states. Critical components of a quantitative description of N-formyl peptide-receptor dynamics in the neutrophil.
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.
Hoffman
J F
JF
Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
Linderman
J J
JJ
Omann
G M
GM
D000595:Amino Acid Sequence; D001152:Arsenicals / Q000494:pharmacology; D005452:Fluoresceins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008024:Ligands; D008954:Models, Biological; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D037342:Pertussis Toxin; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic / Q000187:drug effects / Q000378:metabolism*; D018000:Receptors, Peptide / Q000187:drug effects / Q000378:metabolism*; D013696:Temperature; D015854:Up-Regulation; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D001152:Arsenicals; D005452:Fluoresceins; D008024:Ligands; D009842:Oligopeptides; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic; D018000:Receptors, Peptide; D010566:Virulence Factors, Bordetella; C029341:oxophenylarsine; C061989:F-chemotactic peptide-fluorescein; D037342:Pertussis Toxin