Biologically active conformer of the effector region of human C5a and modulatory effects of N-terminal receptor binding determinants on activity

J Med Chem. 1997 Mar 14;40(6):877-84. doi: 10.1021/jm960727r.

Abstract

A conformationally biased decapeptide agonist of human C5a (C5a55-74Y65,F67,P69,P71,D-Ala73 or YSFKPMPLaR) was used as a functional probe of the C5a receptor (C5aR) in order to understand the conformational features in the C-terminal effector region of C5a that are important for C5aR binding and signal transduction. YSFKPMPLaR was a potent, full agonist of C5a, but at higher concentrations had a superefficacious effect compared to the natural factor. The maximal efficacy of this analogue was 216 +/- 56% that of C5a in stimulating the release of beta-glucuronidase from human neutrophils. C5aR activation and binding curves both occurred in the same concentration range with YSFKPMPLaR, characteristics not observed with natural C5a or more conformationally flexible C-terminal agonists. YSFKPMPLaR was then used as a C-terminal effector template onto which was synthesized various C5aR binding determinants from the N-terminal core domain of the natural factor. In general, the presence of N-terminal binding determinants had little effect on either potency or binding affinity when the C-terminal effector region was presented to the C5aR in this biologically active conformation. However, one peptide, C5a12-20-Ahx-YSFKPMPLaR, expressed a 100-fold increase in affinity for the neutrophil C5aR and a 6-fold increase in potency relative to YSFKPMPLaR. These analyses showed that the peptides used in this study have up to 25% of the potency of C5a in human fetal artery and up to 5% of the activity of C5a in the PMN enzyme release assay.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / metabolism*
  • Arteries / drug effects
  • Arteries / embryology
  • Binding, Competitive
  • Complement C5a / agonists*
  • Complement C5a / chemistry
  • Complement C5a / metabolism
  • Complement C5a / pharmacology*
  • Fetus
  • Glucuronidase / metabolism
  • Humans
  • In Vitro Techniques
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / embryology
  • Neutrophils / drug effects
  • Neutrophils / metabolism
  • Peptide Fragments / chemistry
  • Peptide Fragments / metabolism
  • Peptide Fragments / pharmacology*
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Receptor, Anaphylatoxin C5a
  • Receptors, Complement / metabolism*
  • Vasoconstriction / drug effects

Substances

  • Antigens, CD
  • Peptide Fragments
  • Receptor, Anaphylatoxin C5a
  • Receptors, Complement
  • complement C5a, (65-74), Tyr(65)-Phe(67)-Pro(69,71)-Ala(73)-
  • Complement C5a
  • Glucuronidase