The peptide hormone calcitonion (CT) is the founding member of a family of peptides that comprises amylin (AMY), calcitonin gene-related peptides (CGRPα and CGRPα), adrenomedullin (AM), intermedin (IMD), and calcitonin receptor-stimulating peptide (CRSP). Because of their structural similarity, they can cross-react at their cognate receptors. The first calcitonin receptor (CTR) was cloned in 199. It belongs to G-protein-coupled receptors (GPCRs). It binds with high affinity and responds to CT. The binding of CT to its receptor results in the activation of either adenylate cyclase or phospholipase C. CT receptors are highly expressed in osteoclasts, in the kidney and in the hypothalamus in areas involved with pain, perception, and appetite. The receptors of the other members of the family are made up of subunits. These subunits include: the CTR; the calcitonin receptor-like receptor (CLR), and three accessory proteins termed receptor activity-modifying proteins (RAMPs). Thus, CLR requires RAMP1 to function as a CGRP preferring receptor. The association of CLR with RAMP2 or 3 results in AM receptors. The association of the CTR with RAMPs 1, 2, and 3 functions as the AMY receptors. The CTR does not require RAMPs to bind and respond to CT.
Girgis, S. I., Moradi-Bidhendi, N., & Mancini, L. (2013). Calcitonin Receptor. In Encyclopedia of Biological Chemistry: Second Edition (pp. 270–274). Elsevier Inc. https://doi.org/10.1016/B978-0-12-378630-2.00328-5