GPR139, also known as the JNJ-10397049-sensitive receptor, is a member of the G protein-coupled receptor (GPCR) family, characterized by seven transmembrane domains. It is primarily expressed in the central nervous system, particularly in various brain regions such as the striatum and hypothalamus, regulating neural activity and potentially being involved in feeding behavior, energy balance, and motor control. GPR139, through the activation of endogenous ligands such as L-phenylalanine and L-tryptophan, may mediate signaling pathways involving cAMP and calcium. Its specific expression pattern and function suggest a potential role in neurological disorders, but further research is needed to elucidate its specific biological functions and the potential impact of mutations.