Receptor-activity-modifying protein 1 forms heterodimers with two G-protein-coupled receptors to define ligand recognition.

Receptor-activity-modifying proteins (RAMPs) with single transmembrane domains define the function of two G-protein-coupled receptors of the B family. Cell-surface complexes of human RAMP1 (hRAMP1) and human calcitonin (CT) receptor isotype 2 (hCTR2) or rat CT-receptor-like receptor (rCRLR) have now been identified through protein cross-linking, co-immunoprecipitation and confocal microscopy. They are two distinct CT-gene-related peptide (CGRP) receptors coupled to cAMP production and pharmacologically distinguished by the CT and CGRP antagonists salmon CT(8-32) and human or rat CGRP(8-37). Thus direct molecular interactions of hRAMP1 with hCTR2 or rCRLR are required for CGRP recognition. hCTR2, moreover, adopts non-traditional functions through its association with hRAMP1.