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Identification of Mel 1a 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
Author(s) -
Conway Shaun,
Drew Janice E,
Canning Sarah J,
Barrett Perry,
Jockers Ralf,
Strosberg A.Donny,
Guardiola-Lemaitre Beatrice,
Delagrange Phillipe,
Morgan Peter J
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(97)00315-3
Subject(s) - luzindole , melatonin receptor , hek 293 cells , melatonin , receptor , forskolin , g protein coupled receptor , medicine , endocrinology , biology , biochemistry
Binding assays using 2‐[ 125 I]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 Mel 1a melatonin receptors. Challenge of HEK293 cells with 1 μM melatonin had no effect on forskolin stimulated cyclic AMP levels, whereas in HEK293 cells engineered to stably over‐express the human Mel 1a melatonin receptor ( B max >400 fmol/mg protein) melatonin dose‐dependently inhibited stimulated cyclic AMP levels (IC 50 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.