Receptor for MSH (alpha, beta) and ACTH (PubMed:8034052). Does not seem to be active with gamma-MSH (PubMed:8034052). The activity of this receptor is mediated by G proteins which activate adenylate cyclase (PubMed:8034052). Mediates melanogenesis, the production of eumelanin (black/brown) and phaeomelanin (red/yellow), via regulation of cAMP signaling in melanocytes (By similarity). Interacts with MGRN1, but does not undergo MGRN1-mediated ubiquitination; this interaction competes with GNAS-binding and thus inhibits agonist-induced cAMP production. Interacts with OPN3; the interaction results in a decrease in MC1R-mediated cAMP signaling and ultimately a decrease in melanin production in melanocytes. Highly expressed in the testis. Belongs to the G-protein coupled receptor 1 family.