title: 17Beta-estradiol modulates hMT1 melatonin receptor function.
abstract: Estrogen modulates expression and function of G-protein-coupled receptors. The goal of this study was to assess the effect of 17beta-estradiol (10 nM) exposure for 1 (E1) or 6 (E6) days on density and function of hMT1 and hMT2 melatonin receptors expressed in Chinese hamster ovary (CHO) cells (CHO-MT1/CHO-MT2 cells). This strain of CHO cells expressed both estrogen receptor alpha and beta mRNAs, as determined by RT-PCR amplification. 17beta-Estradiol treatment did not modify the affinity of either receptor; however, it significantly increased the density of 2-[125I]iodomelatonin-binding sites in CHO-MT2 cells. 17beta-Estradiol treatment (1-6 days) did not affect the potency of melatonin to inhibit forskolin stimulation of cAMP formation through activation of either MT1 or MT2 receptors; however, it significantly attenuated the maximal inhibition of forskolin-stimulated cAMP formation induced by melatonin (0.01-1 microM) in CHO-MT1 cells. Melatonin stimulation of [35S]GTPgammaS binding to CHO-MT1 cell membranes was also attenuated following estradiol treatment. The inverse agonist luzindole reduced basal [35S]GTPgammaS binding in estradiol-treated cells but not in control CHO-MT1 cells, suggesting that estradiol promotes constitutive activity of MT1 melatonin receptors. We suggest that 17beta-estradiol differentially affects MT1 and MT2 melatonin receptor functions, attenuates melatonin responses through activation of MT1 receptors, and increases the MT2 receptors density.
authors.affiliation: Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611-3008, USA.
authors.forename: Monica I
authors.initials: MI
authors.lastname: Masana
authors.forename: Jose M
authors.initials: JM
authors.lastname: Soares
authors.forename: Margarita L
authors.initials: ML
authors.lastname: Dubocovich
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D016466:CHO Cells; D003001:Cloning, Molecular / Q000379:methods; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D047629:Estrogen Receptor beta / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000493:pharmacokinetics; D006801:Humans; D007456:Iodine Isotopes / Q000493:pharmacokinetics; D008550:Melatonin / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D011869:Radioligand Assay / Q000379:methods; D044122:Receptor, Melatonin, MT1 / Q000502:physiology*; D044123:Receptor, Melatonin, MT2 / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013460:Sulfur Isotopes / Q000493:pharmacokinetics; D013997:Time Factors
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D007456:Iodine Isotopes; D012333:RNA, Messenger; D044122:Receptor, Melatonin, MT1; D044123:Receptor, Melatonin, MT2; D013460:Sulfur Isotopes; D005576:Colforsin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D004958:Estradiol; D000242:Cyclic AMP; D008550:Melatonin