A biased allosteric modulator functions as a molecular glue to induce β₂AR dimerization.

Area of Science:

• Pharmacology
• Structural Biology
• Biochemistry

Background:

• G-protein coupled receptors (GPCRs), particularly Family A GPCRs, are often viewed as monomers.
• Emerging evidence indicates GPCRs can form dimers with unique signaling characteristics.
• The mechanisms and therapeutic implications of GPCR dimerization are not fully understood.

Purpose of the Study:

• To investigate the role of a novel small molecule, AP-7-168, in modulating β2-adrenergic receptor (β2AR) function.
• To elucidate the structural basis and cellular consequences of AP-7-168-induced β2AR dimerization.
• To explore ligand-induced dimerization as a therapeutic strategy for GPCRs.

Main Methods:

• Cryo-electron microscopy (Cryo-EM) to determine the structure of β2AR dimers.
• Cellular assays to assess β2AR dimerization and nanocluster formation.
• Functional studies to evaluate signaling bias and allosteric modulation.

Main Results:

• AP-7-168 acts as a molecular glue, stabilizing β2AR homodimers.
• Cryo-EM structures reveal AP-7-168 binding within transmembrane helices 3, 4, and 5 of adjacent protomers.
• AP-7-168 binding prevents β-arrestin coupling and promotes β2AR nanocluster formation in cells.
• The molecule selectively biases β2AR signaling through this dimerization mechanism.

Conclusions:

• Ligand-induced dimerization is a novel mechanism for allosteric GPCR modulation.
• AP-7-168 provides a chemical tool to probe and induce β2AR dimerization.
• Targeting GPCR dimerization offers a promising therapeutic strategy for diseases involving β2AR signaling.