A study of the molecular mechanism of binding kinetics and long residence times of human CCR5 receptor small molecule allosteric ligands

Br J Pharmacol. 2014 Jul;171(14):3364-75. doi: 10.1111/bph.12683.

Abstract

Background and purpose: The human CCR5 receptor is a co-receptor for HIV-1 infection and a target for anti-viral therapy. A greater understanding of the binding kinetics of small molecule allosteric ligand interactions with CCR5 will lead to a better understanding of the binding process and may help discover new molecules that avoid resistance.

Experimental approach: Using [(3) H] maraviroc as a radioligand, a number of different binding protocols were employed in conjunction with simulations to determine rate constants, kinetic mechanism and mutant kinetic fingerprints for wild-type and mutant human CCR5 with maraviroc, aplaviroc and vicriviroc.

Key results: Kinetic characterization of maraviroc binding to the wild-type CCR5 was consistent with a two-step kinetic mechanism that involved an initial receptor-ligand complex (RA), which transitioned to a more stable complex, R'A, with at least a 13-fold increase in affinity. The dissociation rate from R'A, k-2 , was 1.2 × 10(-3) min(-1) . The maraviroc time-dependent transition was influenced by F85L, W86A, Y108A, I198A and Y251A mutations of CCR5.

Conclusions and implications: The interaction between maraviroc and CCR5 proceeded according to a multi-step kinetic mechanism, whereby initial mass action binding and later reorganizations of the initial maraviroc-receptor complex lead to a complex with longer residence time. Site-directed mutagenesis identified a kinetic fingerprint of residues that affected the binding kinetics, leading to the conclusion that allosteric ligand binding to CCR5 involved the rearrangement of the binding site in a manner specific to each allosteric ligand.

Keywords: CCR5; HIV-1 infection; allosteric; binding kinetics; maraviroc; molecular mechanism of action; pharmacology.

MeSH terms

  • Allosteric Regulation / drug effects*
  • Binding Sites / drug effects
  • CCR5 Receptor Antagonists / chemistry
  • CCR5 Receptor Antagonists / pharmacology*
  • Cyclohexanes / chemistry
  • Cyclohexanes / pharmacology*
  • Dose-Response Relationship, Drug
  • Humans
  • Kinetics
  • Ligands
  • Maraviroc
  • Receptors, CCR5 / metabolism*
  • Structure-Activity Relationship
  • Time Factors
  • Triazoles / chemistry
  • Triazoles / pharmacology*

Substances

  • CCR5 Receptor Antagonists
  • CCR5 protein, human
  • Cyclohexanes
  • Ligands
  • Receptors, CCR5
  • Triazoles
  • Maraviroc