Polymorphism and signalling of melatonin receptors.
Melatonin receptors belong to the superfamily of G protein-coupled receptors. Cloning of Mel1c receptors expressed in Xenopus skin revealed the existence of a polymorphism for these receptors. Heterologous expression of the two allelic isoforms, called Mel1c(alpha) and Mel1c(beta), indicated functional differences in their signalling properties. Both isoforms are coupled to the cAMP and cGMP pathways. However, the alpha isoform is preferentially coupled to the cAMP pathway, whereas the beta isoform couples preferentially to the cGMP pathway. Coupling differences may be explained by the fact that five of the six amino acid substitutions between the two isoforms are localized within intracellular receptor regions potentially involved in G protein coupling. Allelic isoforms were also observed for Mel1a receptors expressed in ovine pars tuberalis, suggesting that polymorphism is a general feature of the melatonin receptor family. We also evaluated the potential of the two human melatonin receptor subtypes, Mel1a and Mel1b, to modulate the cGMP pathway. Melatonin inhibited intracellular cGMP levels in a dose-dependent manner in HEK293 cells transfected with the human Mel1b receptor. This was not the case for HEK293 cells transfected with the human Mel1a receptor. In conclusion, our results indicate that the expression of receptor subtypes and isoforms may permit differential signalling between melatonin receptors.
Laboratoire d'immuno-pharmacologie moléculaire, Institut Cochin de génétique moléculaire, CNRS-UPR0415 et Université Paris-VII, France.
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Brydon
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Petit
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de Coppet
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Barrett
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Morgan
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Strosberg
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Jockers
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D006152:Cyclic GMP / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000502:physiology; D006162:Guanylate Cyclase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008550:Melatonin / Q000502:physiology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009599:Nitroprusside / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011110:Polymorphism, Genetic; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000502:physiology*; D011810:Quinoxalines / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000145:classification / Q000235:genetics / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000145:classification / Q000235:genetics / Q000502:physiology*; D044094:Receptors, Melatonin; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012756:Sheep; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D012867:Skin / Q000378:metabolism; D013045:Species Specificity; D014162:Transfection; D014982:Xenopus laevis / Q000235:genetics
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D010069:Oxadiazoles; D020033:Protein Isoforms; D011810:Quinoxalines; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin; D011993:Recombinant Fusion Proteins; D009599:Nitroprusside; D005576:Colforsin; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D008550:Melatonin; D015056:1-Methyl-3-isobutylxanthine