title: Cellular and molecular biology of orphan G protein-coupled receptors.
abstract: The superfamily of G protein-coupled receptors (GPCRs) is the largest and most diverse group of membrane-spanning proteins. It plays a variety of roles in pathophysiological processes by transmitting extracellular signals to cells via heterotrimeric G proteins. Completion of the human genome project revealed the presence of approximately 168 genes encoding established nonsensory GPCRs, as well as 207 genes predicted to encode novel GPCRs for which the natural ligands remained to be identified, the so-called orphan GPCRs. Eighty-six of these orphans have now been paired to novel or previously known molecules, and 121 remain to be deorphaned. A better understanding of the GPCR structures and classification; knowledge of the receptor activation mechanism, either dependent on or independent of an agonist; increased understanding of the control of GPCR-mediated signal transduction; and development of appropriate ligand screening systems may improve the probability of discovering novel ligands for the remaining orphan GPCRs.
authors.affiliation: Laboratory of G Protein-Coupled Receptors, Korea University College of Medicine, Seoul 136-707, Korea.
authors.forename: Da Young
authors.initials: DY
authors.lastname: Oh
authors.forename: Kyungjin
authors.initials: K
authors.lastname: Kim
authors.forename: Hyuk Bang
authors.initials: HB
authors.lastname: Kwon
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Seong
mesh_terms: D000818:Animals; D001681:Biological Assay; D002118:Calcium / Q000378:metabolism; D051157:Frizzled Receptors / Q000235:genetics / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D010802:Phylogeny; D011487:Protein Conformation; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism; D011964:Receptors, Gastrointestinal Hormone / Q000235:genetics / Q000378:metabolism; D017470:Receptors, Glutamate / Q000235:genetics / Q000378:metabolism; D015290:Second Messenger Systems / Q000502:physiology
chemical_list: D051157:Frizzled Receptors; D043562:Receptors, G-Protein-Coupled; D011964:Receptors, Gastrointestinal Hormone; D017470:Receptors, Glutamate; C029937:secretin receptor; D020962:Heterotrimeric GTP-Binding Proteins; D002118:Calcium