calcitonin receptor, member of the class B family of seven-transmembrane G protein-coupled receptors
This group includes G protein-coupled receptors for calcitonin (CT) and calcitonin gene-related peptides (CGRPs). Calcitonin, a 32-amino acid peptide hormone, is involved in calcium metabolism in many mammalian species and acts to reduce blood calcium levels and directly inhibits bone resorption by acting on osteoclast. Thus, CT acts as an antagonist to parathyroid hormone and is commonly used in the treatment of bone disorders. The CT receptor is predominantly found in osteoclasts, kidney, and brain, and is primarily coupled to stimulatory G(s) protein, which leads to activation of adenylate cyclase, thereby increasing cAMP production. CGRP, a member of the calcitonin family of peptides, is a potent vasodilator and may contribute to migraine. It is expressed in the peripheral and central nervous system and exists in two forms in humans (alpha-CGRP and beta-CGRP). CGRP meditates its physiological effects through calcitonin receptor-like receptor (CRLR) and receptor activity-modifying protein 1 (RAMP1), a single transmembrane domain protein. Thus, the CRLR/RAMP1 complex serves as a functional CGRP receptor. On the other hand, the CRLR/RAMP2 and CRLR/RAMP3 complexes function as adrenomedullin-specific receptors. The CT and CGRP receptors belong to the B1 subfamily of class B GPCRs, also referred to as secretin-like receptor family, which includes receptors for polypeptide hormones of 27-141 amino-acid residues such as secretin, glucagon, glucagon-like peptide (GLP), parathyroid hormone (PTH), and corticotropin-releasing factor. These receptors contain the large N-terminal extracellular domain (ECD), which plays a critical role in hormone recognition by binding to the C-terminal portion of the peptide.
Jiyao W et al.(2023). "The conserved domain database in 2023.",