Identification of Small-Molecule Positive Modulators of Calcitonin-like Receptor-Based Receptors

Area of Science:

• Pharmacology
• Molecular Biology
• Drug Discovery

Background:

• Class B G protein-coupled receptors (GPCRs) are therapeutically important, yet small-molecule drug development is challenging.
• The calcitonin-like receptor (CLR) is implicated in migraine, cardiovascular disease, and inflammatory bowel disease.
• CLR requires coupling with receptor activity-modifying proteins (RAMPs) to form functional heterodimeric receptors for adrenomedullin and calcitonin gene-related peptide.

Purpose of the Study:

• To identify and characterize novel small molecules that positively modulate CLR:RAMP complexes.
• To investigate the therapeutic potential of these modulators in relevant cellular models.
• To explore potential binding sites for these small-molecule modulators.

Main Methods:

• High-throughput screening using a β-arrestin recruitment assay.
• Medicinal chemistry optimization of initial hits.
• Assays to confirm selectivity against the calcitonin receptor.
• Measurement of cAMP signaling in a vascular cell line.
• Molecular modeling and binding experiments.

Main Results:

• Discovery of small molecules that positively modulate CLR signaling across all three RAMPs.
• Compounds demonstrated selectivity, showing no activity at the related calcitonin receptor.
• Positive modulation of cAMP signaling observed in a vascular cell model, indicating translational potential.
• Binding studies ruled out extracellular binding sites, while molecular modeling suggested allosteric binding pockets.

Conclusions:

• These represent the first described small-molecule positive modulators for CLR:RAMP complexes.
• The identified compounds offer a promising starting point for developing therapeutics targeting CLR-mediated pathways.
• The findings provide insights into potential allosteric modulation mechanisms for Class B GPCRs.