Modulation of ligand selectivity by mutation of the first extracellular loop of the human C5a receptor

Cain, S. A., Woodruff, T. M., Taylor, S. M., Fairlie, D. P., Sanderson, S. D. and Monk, P. N. (2001) Modulation of ligand selectivity by mutation of the first extracellular loop of the human C5a receptor. Biochemical Pharmacology, 61 12: 1571-1579. doi:10.1016/S0006-2952(01)00608-6


Author Cain, S. A.
Woodruff, T. M.
Taylor, S. M.
Fairlie, D. P.
Sanderson, S. D.
Monk, P. N.
Title Modulation of ligand selectivity by mutation of the first extracellular loop of the human C5a receptor
Journal name Biochemical Pharmacology   Check publisher's open access policy
ISSN 0006-2952
Publication date 2001-01-01
Sub-type Article (original research)
DOI 10.1016/S0006-2952(01)00608-6
Volume 61
Issue 12
Start page 1571
End page 1579
Total pages 9
Editor Alan C. Sartorelli
Jacques E. Gielen
Place of publication United States
Publisher Elsevier Science
Language eng
Subject C1
250204 Bioinorganic Chemistry
730102 Immune system and allergy
320502 Basic Pharmacology
780105 Biological sciences
Abstract The cyclic C5a receptor antagonist, phenylalanine [L-ornithine-proline-D-cyclohexylalanine-tryptophan-arginine] (F-[OPchaWR]), has similar to 1000-fold less affinity for the C5a receptor (C5aR) on murine polymorphonuclear leukocytes than on human. Analysis of C5aR from different species shows that a possible cause of this difference is the variation in the sequence of the first extracellular loop of the receptor. The mouse receptor contains Y at a position analogous to P-103 in the human receptor, and D at G(105). To test this hypothesis, we expressed human C5aR mutants ((PY)-Y-103, G(105)D and the double mutant, (PY)-Y-103/G(105)D) in RBL-2H3 cells and investigated the effects of these mutations on binding affinity and receptor activation. All three mutant receptors had a higher affinity for human C5a than the wild-type receptor, but showed no significant difference in the ability of F-[OPchaWR] to inhibit human C5a binding. However, all of the mutant receptors had substantially lower affinities for the weak agonist, C5a des Arg(74) (C5adR(74)), and two altered receptors (G(105)D and (PY)-Y-103/G(105)D) had much lower affinities for the C-terminal C5a agonist peptide analogue, L-tyrosine-serine-phenylalanine-lysine-proline-methionine-proline-leucine-D-alanine-arginine (YSFKPMPLaR). Although it is unlikely that differences at these residues are responsible for variations in the potency of F-[OPchaWR] across species, residues in the first extracellular loop are clearly involved in the recognition of both C5a and C5a agonists. The complex effects of mutating these residues on the affinity and response to C5a, C5adR(74), and the peptide analogues provide evidence of different binding modes for these ligands on the C5aR. (C) 2001 Elsevier Science Inc. All rights reserved.
Keyword Pharmacology & Pharmacy
Complement
C5a
Receptor
Antagonist
Mast Cells
Anaphylatoxin Receptor
Pharmacological Characterization
Molecular-cloning
Des Arg
Identification
Activation
Expression
Residues
Binding
Site
Q-Index Code C1

 
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Created: Wed, 15 Aug 2007, 02:46:31 EST