Chemokine receptor activity is differentially regulated by membrane cholesterol

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Cholesterol is a vital membrane component influencing G protein-coupled receptor (GPCR) function.
• The precise molecular mechanisms by which cholesterol modulates GPCRs, particularly chemokine receptors, are not fully understood.

Purpose of the Study:

• To elucidate the role of cholesterol in regulating the activation and signaling of chemokine receptors.
• To define the molecular basis for cholesterol's allosteric modulation of GPCRs.

Main Methods:

• Chemical extraction of membrane sterols.
• Functional cell signaling assays.
• Single-molecule fluorescence resonance energy transfer (smFRET) to analyze receptor conformational changes.

Main Results:

• Cholesterol reduction selectively altered signaling of specific chemokine receptors (CXCR1, CXCR2, CXCR4, ACKR3), demonstrating receptor-specific dependence.
• Cholesterol's regulatory mechanism involved a conserved GPCR residue (Trp4.50).
• Cholesterol shifted agonist-bound CXCR4 towards active conformations, explaining functional effects.

Conclusions:

• Cholesterol acts as an allosteric regulator of chemokine receptor activity.
• Oxysterols differ from cholesterol in modulating GPCR activation, suggesting distinct roles in inflammatory signaling.