Unique Biased Agonism Profile of βCGRP on CGRP Family Receptors

α- and β-calcitonin gene-related peptides (αCGRP and βCGRP, respectively), together with adrenomedullin (AM) and AM2 are endogenous agonists of the CGRP family of receptors; CGRP receptor (CGRPR), AM₁ receptor (AM₁R), and AM₂ receptor (AM₂R). The high sequence homology and similar tissue distribution of αCGRP and βCGRP suggests they have overlapping physiological roles in pain pathways, inflammation, and metabolism, but recent data indicate potential differences in the signaling capabilities of these peptides. However, a comprehensive pharmacological characterization of βCGRP activity, compared to αCGRP, AM, and AM2 across the three CGRP family receptors, is lacking. In this study, we assessed proximal G protein coupling/activation, cognate second messenger production, regulatory protein recruitment and receptor trafficking induced by αCGRP, βCGRP, AM, and AM2 at the CGRPR, AM₁R, and AM₂R. Our findings revealed a distinct profile of transducer and regulatory protein engagement induced by βCGRP compared to αCGRP across these receptors. The identification of differences in pharmacological profiles for αCGRP and βCGRP indicates that they may have more distinct physiological roles than previously appreciated and may assist in distinguishing the roles of these two peptides for exploitation in targeted drug design.