Role of Cyclic AMP in Mediating the Effects of MSH, Norepinephrine, and Melatonin on Frog Skin Color

Abe, Kaoru; Robison, G. Alan; Liddle, Grant W.; Butcher, R.W.; Nicholson, Wendell E.; Baird, Coleen P.

doi:10.1210/endo-85-4-674

Cited by 153 publications

(45 citation statements)

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“…In addition, specific 125I-Mel binding in acutely transfected cells is inhibited by six ligands in a rank order that is identical to that reported for the endogenous receptor in reptiles, birds, and mammals (4,,7, 9). The ability of the recombinant Xenopus melatonin receptor to inhibit the forskolinstimulated increase in cAMP accumulation in stably transfected CHO cells is consistent with studies ofthe endogenous receptor showing that a major signal transduction pathway for the high-affinity receptor is inhibition of adenylyl cyclase (13,15 …”

Section: Discussionsupporting

confidence: 82%

“…12). This action is mediated through a high-affinity melatonin receptor that is coupled to inhibitory G protein (Gi) (13,14). Using a cDNA library constructed from an immortalized cell line ofXenopus dermal melanophores and a mammalian cell expression cloning strategy, we have succeeded in cloning a high-affinity melatonin receptor.…”

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confidence: 99%

“…We next examined whether the recombinant melatonin receptor is coupled to inhibition of adenylyl cyclase as occurs with the endogenous receptor in Xenopus dermal melanophores (13,15 10 A&M forskolin (Fig. 3); the maximal inhibition of the mean forskolin-stimulated cAMP value was 68% at 10-8 M melatonin.…”

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confidence: 99%

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Expression cloning of a high-affinity melatonin receptor from Xenopus dermal melanophores.

Ebisawa

Karne

Lerner

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

398

225

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Using an expression cloning strategy, a highanit meltonin receptor cDNA has been isolated from Xenopus laei dermal melanophores. Transient expression of the cDNA in COS-7 cells resulted in h-affinity 2-[125I-odomneatonn binding (Kd = 6.3 ± 0.3 x 10-11 M). In addition, six ligands exhibited a rank order of inhibition of specific 2-uI has revealed the presence of high-affinity melatonin receptors (Kd < 2 x 10-10 M) (4-6). Receptor affinity is sensitive to guanine nucleotides and activation of the receptors consistently leads to inhibition of adenylyl cyclase through a pertussis toxin-sensitive mechanism (7-11). High-affinity melatonin receptors thus appear to belong to the superfamily of guanine nucleotide binding protein (G protein)-coupled receptors. To better understand how melatonin acts at a cellular and molecular level, it is important to determine melatonin receptor structure.One of the earliest described actions of melatonin is its ability to cause melanin aggregation in dermal melanophores of amphibians (for review, see ref. 12). This action is mediated through a high-affinity melatonin receptor that is coupled to inhibitory G protein (Gi) (13,14). Using a cDNA library constructed from an immortalized cell line ofXenopus dermal melanophores and a mammalian cell expression cloning strategy, we have succeeded in cloning a high-affinity melatonin receptor. The cDNA encodes a protein that is a newly discovered member of the G protein-coupled receptor family. 11 MATERIALS AND METHODS Expression Cloning. Xenopus laevis dermal melanophores were cultured as described (15). The melanophores were derived from a clonal line that was isolated from a primary culture. Total cellular RNA was isolated from melanophores by extraction with guanidinium thiocyanate and separation in cesium chloride. Melanosomes were removed as described before centrifugation on the cesium chloride gradient (16). Poly(A)+ RNA was isolated by established methods (17).A random-primed cDNA library was constructed with a kit from Pharmacia. Double-stranded cDNA was ligated with nonpalindromic BstXI/EcoRI adaptors (Invitrogen). The cDNA was size-fractionated on an agarose gel, and cDNA>2 2 kb was recovered by electroelution. The size-selected cDNA was ligated into the expression vector pcDNAI (Invitrogen) and introduced into Escherichia coli MC1061/P3 by electroporation.A total of 4 x 105 recombinants were obtained from 5 pg of poly(A)+ RNA and divided into 54 pools of "7400 clones each. Plasmid DNA was prepared from each pool by the alkaline lysis method and transfected into COS-7 cells by the DEAE-dextran method (18). Three days after transfection, cells were incubated with 90 pM 125I-Mel in 50 mM Tris-HCl (pH 7.4) containing 100 mM NaCI, 5 mM KCl, 2 mM CaCl2, and 5% Nu-Serum I (Collaborative Biomedical Products, Bedford, MA) for 2 hr at room temperature. Cells were washed, air dried, and exposed to x-ray film for 14 days. A pool of clones that showed positive signals was subdivided, and the transfection procedure was repeated. This ...

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Section: Discussionsupporting

confidence: 82%

mentioning

confidence: 99%

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Expression cloning of a high-affinity melatonin receptor from Xenopus dermal melanophores.

Ebisawa

Karne

Lerner

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

398

225

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“…Melatonin inhibits the accumulation of cAMP [33,34] and exerts most of its effects in a pertussis toxin-sensitive fashion [35]. This implies that the melatonin receptor(s) is coupled to an inhibitory G protein (G i ); however, a cholera toxin-sensitive action has also been observed [36], indicating coupling to G 0 .…”

Section: Signal Transduction Of Melatoninmentioning

confidence: 99%

Melatonin receptors in pancreatic islets: good morning to a novel type 2 diabetes gene

et al. 2009

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Melatonin is a circulating hormone that is primarily released from the pineal gland. It is best known as a regulator of seasonal and circadian rhythms; its levels are high during the night and low during the day. Interestingly, insulin levels also exhibit a nocturnal drop, which has previously been suggested to be controlled, at least in part, by melatonin. This regulation can be explained by the proposed inhibitory action of melatonin on insulin release. Indeed, both melatonin receptor 1A (MTNR1A) and MTNR1B are expressed in pancreatic islets. The role of melatonin in the regulation of glucose homeostasis has been highlighted by three independent publications based on genome-wide association studies of traits connected with type 2 diabetes, such as elevated fasting glucose, and, subsequently, of the disease itself. The studies demonstrate a link between variations in the MTNR1B gene, hyperglycaemia, impaired early phase insulin secretion and beta cell function. The risk genotype predicts the future development of type 2 diabetes. Carriers of the risk genotype exhibit increased expression of MTNR1B in islets. This suggests that these individuals may be more sensitive to the actions of melatonin, leading to impaired insulin secretion. Blocking the inhibition of insulin secretion by melatonin may be a novel therapeutic avenue for type 2 diabetes.

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“…However, the cellular mechanism of action of melatonin is poorly understood. Early studies on amphibian skin demonstrated an inhibitory effect of' the hormone upon adenylate cyclase activity (9), but in higher vcrlcbrates the site and mechanism of action have remained elusive (2). Recently, autoradiographic studies have used the analogue, 2-[1251]iodomelatonin to reveal specific, high affinity binding sites for melatonin in the brain and pituitary of mammals ( 10 1 9 , and the melatonin receptor of the ovine pars tuberalis ha.s been subject to extensive pharmacological characterization (16).…”

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Melatonin Inhibits the Activation of Cyclic AMP‐Dependent Protein Kinase in Cultured Pars Tuberalis Cells from Ovine Pituitary

Hazlerigg

Morgan²,

Lawson³

et al. 1991

J Neuroendocrinology

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The effect of melatonin upon the activation of the intracellular effector enzyme, cyclic AMP (CAMP)-dependent protein kinase (PKA), was investigated in primary cultures of ovine pars tuberalis cells. Incubation of these cells with forskolin caused a rapid and dose-dependent activation of PKA (ED, 10-6M). When cells were incubated with forskolin and melatonin simultaneously, the activation of PKA by forskolin was dramatically inhibited. This inhibitory effect of melatonin was dose-dependent (EDa 10-"M).Furthermore, treatment with melatonin rapidly deactivated PKA in cells prestimulated with forskolin. When pars tuberalis cell extracts were incubated with 8N,-[32P]cAMP, an analogue of cAMP used for photoaffinity labelling of native PKA, specific binding was observed in three bands with M, of 54, 52 and 48 kd. representing the regulatory subunits of PKA II (in phosphorylated and dephosphorylated forms) and PKA I, respectively. These results indicate that melatonin is a potent inhibitory regulator of CAMPmediated signal transduction in the ovine pars tuberalis, and suggest that the cellular effects of melatonin in this tissue a r e mediated by the dephosphorylation of specific substrate proteins.

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Role of Cyclic AMP in Mediating the Effects of MSH, Norepinephrine, and Melatonin on Frog Skin Color

Cited by 153 publications

References 0 publications

Expression cloning of a high-affinity melatonin receptor from Xenopus dermal melanophores.

Expression cloning of a high-affinity melatonin receptor from Xenopus dermal melanophores.

Melatonin receptors in pancreatic islets: good morning to a novel type 2 diabetes gene

Melatonin Inhibits the Activation of Cyclic AMP‐Dependent Protein Kinase in Cultured Pars Tuberalis Cells from Ovine Pituitary

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