Ligand binding to human prostaglandin E receptor EP₄ at the lipid-bilayer interface

Area of Science:

• Structural Biology
• Pharmacology
• Immunology

Background:

• Prostaglandin E receptor EP4 (a G-protein-coupled receptor) is implicated in cancer and autoimmune diseases.
• Understanding EP4 structure is crucial for developing targeted therapies.

Purpose of the Study:

• To determine the crystal structure of human EP4 in complex with an antagonist and an antibody.
• To elucidate the binding mechanism of agonists and antagonists to EP4.
• To provide insights for novel drug design targeting EP4.

Main Methods:

• X-ray crystallography at 3.2 Å resolution.
• Functional and docking studies.
• Analysis of ligand-receptor interactions.

Main Results:

• The crystal structure of human EP4 with antagonist ONO-AE3-208 and an inhibitory antibody was determined.
• The antagonist binds at the lipid bilayer interface, near Arg316.
• The natural agonist Prostaglandin E2 (PGE2) binds similarly, with insights into ligand entry.
• An antibody allosterically modulates EP4 ligand binding.

Conclusions:

• The determined structure provides a detailed view of EP4 ligand binding.
• This structural information facilitates the design of therapeutics targeting both orthosteric and allosteric sites of EP4.
• The findings are significant for developing new drugs for EP4-related disorders.