G protein-coupled receptor 19, member of the class A family of seven-transmembrane G protein-coupled receptors
G-protein coupled receptor 19 is an orphan receptor that is expressed predominantly in neuronal cells during mouse embryogenesis. Its mRNA is found frequently over-expressed in patients with small cell lung cancer. GPR19 shares a significant amino acid sequence identity with the D2 dopamine and neuropeptide Y families of receptors. Human GPR19 gene, intronless in the coding region, also has a distribution in brain overlapping that of the D2 dopamine receptor gene, and is located on chromosome 12. GPR19 is a member of the class A family of GPCRs, which represents a widespread protein family that includes the light-sensitive rhodopsin as well as receptors for biogenic amines, lipids, nucleotides, odorants, peptide hormones, and a variety of other ligands. All GPCRs have a common structural architecture comprising of seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops. A general feature of GPCR signaling is agonist-induced conformational changes in the receptors, leading to activation of the heterotrimeric G proteins, which consist of the guanine nucleotide-binding G-alpha subunit and the dimeric G-beta-gamma subunits. The activated G proteins then bind to and activate numerous downstream effector proteins, which generate second messengers that mediate a broad range of cellular and physiological processes.
Comment:based on the structures of some class A family members with bound ligands (peptides or chemicals), agonists, or antagonists
Comment:Small-molecule chemical ligands tend to bind deeper within the receptor core, compared to a peptide ligand neurotensin, which binds towards the extracellular surface of its receptor.
Jiyao W et al.(2023). "The conserved domain database in 2023.",