Structural basis for signal recognition and transduction by platelet-activating-factor receptor

Area of Science:

• Structural biology
• Molecular pharmacology
• Biochemistry

Background:

• The platelet-activating-factor receptor (PAFR) mediates diverse physiological effects through interaction with platelet-activating factor (PAF).
• PAFR is a significant therapeutic target for asthma, inflammation, and cardiovascular diseases due to its role in cell signaling.

Purpose of the Study:

• To elucidate the structural mechanisms underlying PAFR activation and ligand recognition.
• To provide atomic-level insights into PAFR's interaction with antagonists and inverse agonists.

Main Methods:

• X-ray crystallography was employed to determine the structures of human PAFR bound to SR 27417 (antagonist) and ABT-491 (inverse agonist).
• Molecular docking simulations were performed with platelet-activating factor (PAF).
• Single-molecule Förster resonance energy transfer (smFRET) and cell-based functional assays were utilized to assess receptor dynamics and activation.

Main Results:

• Crystal structures of human PAFR were obtained at 2.8-Å and 2.9-Å resolution with antagonist SR 27417 and inverse agonist ABT-491, respectively.
• The PAFR-SR 27417 complex exhibited an unusual conformation with outward shifts in intracellular helices II and IV and an inward shift of helix VIII.
• Ligand-dependent conformational changes in the helical bundle were observed, correlating with PAFR activation.

Conclusions:

• The determined PAFR structures offer critical insights into ligand-binding and signal-recognition mechanisms.
• Ligand-induced conformational changes in the helical bundle are essential for PAFR activation, impacting G-protein-coupled receptor signaling.
• These findings significantly enhance the understanding of PAFR function and provide a basis for rational drug design targeting PAFR.