Kinetic analysis of the early signaling steps of the human chemokine receptor CXCR4


  • C. Perpina-Viciano
  • A. Isbilir
  • A. Zarca
  • B. Caspar
  • L.E. Kilpatrick
  • S.J. Hill
  • M.J. Smit
  • M.J. Lohse
  • C. Hoffmann


  • Molecular Pharmacology


  • Mol Pharmacol 98 (2): 72-87


  • G protein-coupled receptors (GPCRs) are biological switches that transduce extracellular stimuli into intracellular responses in the cell. Temporally resolving GPCR transduction pathways is key to understanding how cell signaling occurs. Here, we investigate the kinetics and dynamics of the activation and early signaling steps of the chemokine receptor CXCR4 in response to its natural ligands CXCL12 and macrophage migration inhibitory factor (MIF), using Förster resonance energy transfer-based approaches. We show that CXCR4 presents a multifaceted response to CXCL12, with receptor activation (≈0.6s) followed by a rearrangement in the receptor/G protein complex (≈1s), a slower dimer rearrangement (≈1.7s) and prolonged G protein activation (≈4s). In comparison, MIF distinctly modulates every step of the transduction pathway, indicating distinct activation mechanisms and reflecting the different pharmacological properties of these two ligands. Our study also indicates that CXCR4 exhibits some degree of ligand-independent activity, a relevant feature for drug development. SIGNIFICANCE STATEMENT: The CXCL12/CXCR4 axis represents a well-established therapeutic target for cancer treatment. We demonstrate that CXCR4 exhibits a multifaceted response that involves dynamic receptor dimer rearrangements, which is kinetically embedded between receptor-G protein complex rearrangements and G protein activation. The alternative endogenous ligand MIF behaves opposite to CXCL12 in each assay studied and does not lead to G protein activation. This detailed understanding of the receptor activation may aid in the development of more specific drugs against this target.