Dynamic conformational switching in the chemokine ligand is essential for G-protein-coupled receptor activation

Prem Raj B. Joseph, Kirti V. Sawant, Angela Isley, Mesias Pedroza, Roberto P. Garofalo, Ricardo M. Richardson, Krishna Rajarathnam

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

Chemokines mediate diverse functions from organogenesis to mobilizing leucocytes, and are unusual agonists for class-A GPCRs (G-protein-coupled receptors) because of their large size and multi-domain structure. The current model for receptor activation, which involves interactions between chemokine N-loop and receptor N-terminal residues (Site-I) and between chemokine N-terminal and receptor extracellular loop/transmembrane residues (Site-II), fails to describe differences in ligand/receptor selectivity and the activation of multiple signalling pathways. In the present study, we show in neutrophil-activating chemokine CXCL8 that the highly conserved GP (glycine-proline) motif located distal to both N-terminal and N-loop residues couples Site-I and Site-II interactions. GP mutants showed large differences from nativelike to complete loss of function that could not be correlated with the specific mutation, receptor affinity or subtype, or a specific signalling pathway. NMR studies indicated that the GP motif does not influence Site-I interactions, but molecular dynamics simulations suggested that this motif dictates substates of the CXCL8 conformational ensemble. We conclude that the GP motif enables diverse receptor functions by controlling cross-talk between Site-I and Site-II, and further propose that the repertoire of chemokine functions is best described by a conformational ensemble model in which a network of long-range coupled indirect interactions mediate receptor activity.

Original languageEnglish (US)
Pages (from-to)241-251
Number of pages11
JournalBiochemical Journal
Volume456
Issue number2
DOIs
StatePublished - Dec 1 2013

Keywords

  • Chemokine
  • Conformational ensemble
  • G-proteincoupled receptor
  • Long-range coupling
  • Signalling

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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