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Direct assessment of CXCR4 mutant conformations reveals complex link between receptor structure and G(alpha)(i)

Yamina A Berchiche1, Ken Y Chow, Bernard Lagane

  • 1Department of Biochemistry, Université de Montréal, Montréal, Québec H3T 1J4, Canada.

The Journal of Biological Chemistry
|January 2, 2007
PubMed

Insights

G protein-coupled receptor (GPCR) activation involves complex conformational changes. This study reveals that multiple active GPCR conformations can trigger downstream signaling, challenging existing models.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • G protein-coupled receptors (GPCRs) mediate cellular responses through conformational changes upon ligand binding.
  • Current models of GPCR activation do not fully explain the link between receptor conformation and effector activity.
  • Understanding GPCR structure-function relationships is crucial for drug development.

Purpose of the Study:

  • To investigate the relationship between receptor conformation and G alpha i activation in the chemokine receptor CXCR4.
  • To elucidate the role of specific residues (DRY motif and N(3.35)119) in CXCR4 conformational dynamics and signaling.
  • To provide biophysical evidence for distinct active receptor conformations.

Main Methods:

  • Utilized bioluminescence resonance energy transfer (BRET) to directly measure receptor conformation.
  • Generated and analyzed mutants of the chemokine receptor CXCR4, focusing on the DRY motif and N(3.35)119.
  • Assessed G alpha i activation for wild-type and mutant CXCR4 receptors.

Main Results:

  • Mutations in CXCR4 affected G alpha i activation, with some mutants showing wild-type activity, loss of activity, or constitutive activity.
  • Bioluminescence resonance energy transfer analysis indicated no direct correlation between ligand-induced conformational changes and G alpha i activation.
  • Multiple distinct conformations were observed for both active and inactive CXCR4 receptors, including wild-type and specific mutants.

Conclusions:

  • Different conformations of active CXCR4 receptors can effectively trigger G alpha i signaling.
  • The findings support advanced models of GPCR structure-activity relationships that incorporate receptor conformational flexibility.
  • This work provides critical biophysical insights into the dynamic nature of GPCR activation and signaling.

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