Mc2r, also known as the adrenocorticotropic hormone receptor (ACTHR), is a member of the G protein-coupled receptor family and is a type of melanocortin receptor. It is uniquely activated by adrenocorticotropic hormone (ACTH) and is crucial in the hypothalamic-pituitary-adrenal (HPA) axis. This axis is involved in regulating stress responses, metabolism, and immune function. Its function is also associated with the biosynthesis of glucocorticoids [1,4].

Mutations in the Mc2r gene can lead to type 1 familial glucocorticoid deficiency (FGD). For example, a novel homozygous missense mutation c.326T>A, p.Leu109Gln in the Mc2R gene disrupts cAMP production and protein expression, resulting in ACTH resistance and FGD phenotypes [2]. Also, a novel class of nonpeptide Mc2r antagonists like CRN04894 has been discovered, which may be used to treat ACTH-dependent diseases such as congenital adrenal hyperplasia (CAH) and Cushing's disease (CD) [3]. In cows, ACTH treatment can affect the expression of the Mc2R/MRAP2 complex in the dominant follicle, altering the expression of steroidogenic enzymes [4].

In conclusion, Mc2r is essential for normal physiological function through its role in the HPA axis and glucocorticoid biosynthesis. Studies on gene mutations and the discovery of antagonists have provided insights into its function in diseases like FGD, CAH, and Cushing's disease. Understanding Mc2r helps in elucidating the mechanisms of related diseases and developing potential treatment strategies.