title: Identification of Mel1a melatonin receptors in the human embryonic kidney cell line HEK293: evidence of G protein-coupled melatonin receptors which do not mediate the inhibition of stimulated cyclic AMP levels.
abstract: Binding assays using 2-[125I]iodomelatonin revealed high-affinity, guanosine 5'-O-(3-thiotriphosphate) sensitive, melatonin binding sites (B(max) 1.1 fmol/mg protein) in the human embryonic kidney cell line HEK293. Competition studies using the selective melatonin receptor antagonist luzindole and RT-PCR techniques identified these sites as human Mel1a melatonin receptors. Challenge of HEK293 cells with 1 microM melatonin had no effect on forskolin stimulated cyclic AMP levels, whereas in HEK293 cells engineered to stably over-express the human Mel1a melatonin receptor (B(max) > 400 fmol/mg protein) melatonin dose-dependently inhibited stimulated cyclic AMP levels (IC50 7.7 pM). These data may indicate that certain tissues, expressing low levels of G protein-coupled melatonin receptors, do not display melatonin mediated inhibition of cAMP.
authors.affiliation: Molecular Neuroendocrinology Group, Rowett Research Institute, Bucksburn, Aberdeen, UK. sco@rri.sari.ac.uk
authors.forename: S
authors.initials: S
authors.lastname: Conway
authors.forename: J E
authors.initials: JE
authors.lastname: Drew
authors.forename: S J
authors.initials: SJ
authors.lastname: Canning
authors.forename: P
authors.initials: P
authors.lastname: Barrett
authors.forename: R
authors.initials: R
authors.lastname: Jockers
authors.forename: A D
authors.initials: AD
authors.lastname: Strosberg
authors.forename: B
authors.initials: B
authors.lastname: Guardiola-Lemaitre
authors.forename: P
authors.initials: P
authors.lastname: Delagrange
authors.forename: P J
authors.initials: PJ
authors.lastname: Morgan
mesh_terms: D001667:Binding, Competitive; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D015698:Genomic Library; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D008550:Melatonin / Q000031:analogs & derivatives / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D044094:Receptors, Melatonin; D017422:Sequence Analysis, DNA; D012701:Serotonin / Q000031:analogs & derivatives / Q000378:metabolism; D015398:Signal Transduction; D014363:Tryptamines / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin; D014363:Tryptamines; C057154:luzindole; D005576:Colforsin; D012701:Serotonin; C044556:2-iodomelatonin; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D008550:Melatonin; C006389:N-acetylserotonin; C012365:6-hydroxymelatonin