MC2R

MC2R (melanocortin 2 receptor) is a G protein-coupled receptor that serves as the physiological receptor for adrenocorticotropic hormone (ACTH) and is essential for the regulation of adrenocortical function and steroidogenesis^[1][2]. Mechanistically, ACTH binding to MC2R activates intracellular cAMP-dependent signaling pathways that promote glucocorticoid biosynthesis and support adrenal endocrine function^[1]. MC2R occupies a central position within the hypothalamic-pituitary-adrenal axis, where it mediates hormonal responses to physiological stress and maintains corticosteroid homeostasis^[2]. In disease settings, genetic defects in MC2R impair ACTH responsiveness and are a recognized cause of familial glucocorticoid deficiency, highlighting the receptor’s critical role in adrenal development and glucocorticoid production. Compared with other melanocortin receptor family members, MC2R displays a unique ligand selectivity profile because it is activated exclusively by ACTH, whereas other melanocortin receptors respond to multiple melanocortin peptides including α-MSH, β-MSH, and γ-MSH^[2][3]. Functional activity of MC2R also differs from related isoforms through its dependence on melanocortin receptor accessory proteins (MRAPs), which are required for efficient receptor trafficking, ligand binding, and signaling competence^[4]. For experimental applications, ACTH and its clinically used analogs, including cosyntropin, serve as established MC2R agonists, while emerging antagonists such as CRN04894 provide pharmacological tools for investigating receptor-specific signaling and adrenal endocrine regulation^[3].