The function of MC3R (melanocortin 3 receptor, ENSG00000124089) is as follows. G protein-coupled receptor for melanocyte-stimulating hormones (alpha, beta, and gamma-MSH) and corticotropin/ACTH, which are peptide products of the POMC precursor (PubMed:37524700, PubMed:8463333). Upon activation, couples to G(s) protein, stimulating adenylate cyclase and the cAMP-dependent signaling pathway, which contributes to the regulation of energy homeostasis (PubMed:18231126, PubMed:37524700, PubMed:8463333). Required for expression of anticipatory patterns of activity and wakefulness during periods of limited nutrient availability and for the normal regulation of circadian clock activity in the brain (By similarity). Binding of the Agouti-related protein/AGPR antagonist precludes alpha-MSH-induced signaling, blocking cAMP production (PubMed:9311920). {ECO:0000250|UniProtKB:P33033, ECO:0000269|PubMed:18231126, ECO:0000269|PubMed:37524700, ECO:0000269|PubMed:8463333, ECO:0000269|PubMed:9311920}.