Identification of Mel<sub>1a</sub> 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

Conway, Shaun; Drew, Janice E.; Canning, Sarah J.; Barrett, Perry; Jockers, Ralf; Strosberg, A. D.; Guardiola‐Lemaître, B.; Delagrange, P; Morgan, Peter J.

doi:10.1016/s0014-5793(97)00315-3

Cited by 39 publications

(38 citation statements)

References 19 publications

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“…In the binding experiments, we compared the 2-iodomelatonin-binding abilities of GT1–7 cells to those of HEK293 cells, which express melatonin receptors [24,25], and NIH3T3 cells, which are commonly used as a negative control for the 2- iodomelatonin binding assay [26,27]. The GT1–7 and NIH3T3 cells showed similar binding abilities in the presence of 100 p M radiolabeled 2-iodomelatonin (fig.…”

Section: Resultsmentioning

confidence: 99%

Cetrorelix, a Gonadotropin-Releasing Hormone Antagonist, Induces the Expression of Melatonin Receptor 1a in the Gonadotropin-Releasing Hormone Neuronal Cell Line GT1–7

Ishii

Sato²,

Yin³

et al. 2009

Neuroendocrinology

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Melatonin has been implicated in the control of the reproductive system, and the modulatory actions of melatonin on gonadotropin-releasing hormone (GnRH) neurons have been assumed to be indirectly mediated through afferent neurons. However, our previous studies demonstrate sexually dimorphic modulation of A-type γ-aminobutyric acid (GABA) receptor (GABA_AR) currents by melatonin in adult rat GnRH neurons and a preferential expression of melatonin 1a receptor (MT1) in male GnRH neurons. Using immortalized GnRH neurons (GT1–7 cells), the present study investigated the mechanism by which the expression of melatonin receptors is regulated in GnRH neurons. Like endogenous GnRH neurons, GT1–7 cells express both GnRH and GnRH receptor mRNAs, indicating that the cells have a self-stimulatory system. A 2-iodomelatonin binding assay and RT-PCR analysis demonstrated that the cells expressed neither MT1 nor MT2. However, treatment of GT1–7 cells with the GnRH antagonist cetrorelix significantly increased 2-iodomelatonin binding and induced a time- and concentration-dependent MT1 mRNA expression. The GABA_AR currents were then measured using a perforated patch-clamp technique to examine whether the treatment with cetrorelix changed the responses to melatonin. Melatonin augmented the GABA_AR currents in GT1–7 cells treated with 1 μM cetrorelix for 24 h, while melatonin decreased the currents in the cells not treated with cetrorelix, probably via receptor-independent processes. The present results suggest that GnRH downregulates the expression of MT1 via an autocrine-paracrine mechanism in GT1–7 cells, and modifies the melatonin-induced modulation of GABA_AR currents. These findings may provide one possible mechanism for the sexually dimorphic responses to melatonin in adult rat GnRH neurons.

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Section: Resultsmentioning

confidence: 99%

Cetrorelix, a Gonadotropin-Releasing Hormone Antagonist, Induces the Expression of Melatonin Receptor 1a in the Gonadotropin-Releasing Hormone Neuronal Cell Line GT1–7

Ishii

Sato²,

Yin³

et al. 2009

Neuroendocrinology

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“…After RT-PCR, the amplified DNA products were separated on a 1.5% agarose gel and stained with ethidium bromide. Southern blotting analysis was performed, and blots were hybridized with synthetic 32 P-labeled oligonucleotide probes: 5Ј-TGCGTTCCTGAGCTTCTT-GTTCCGATACAC-3Ј (154-183) for Mel 1a [14], and 5Ј-TGCGTTCCGGAGCTTGCGGTTCCTGAGCAC-3Ј (193-222) for Mel 1b [14].…”

Section: Mel 1a and Mel 1b Expression By Rt-pcrmentioning

confidence: 99%

Growth-inhibitory activity of melatonin on human androgen-independent DU 145 prostate cancer cells

et al. 2000

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BACKGROUND. The pineal hormone melatonin has been shown to exert a direct oncostatic activity on neoplastic cells, particularly from breast cancer. In the present study, we evaluated the effects of melatonin on the proliferation and on the cell cycle distribution of human androgen-independent DU 145 prostate cancer cells. Experiments were also performed to gain insights into the possible mechanism of action of the hormone. METHODS. The effects of melatonin on DU 145 cell proliferation was analyzed by counting the cells by hemocytometer at the end of treatment. The effects of the pineal hormone on cell cycle distribution were evaluated by FACS analysis. RT-PCR studies were performed to detect Mel 1a and Mel 1b expression in DU 145 cells. The cellular localization of 125 I-melatonin binding sites was investigated by radioreceptor assay. A commercially available binding-protein assay kit was utilized to evaluate intracellular cAMP levels. RESULTS. Melatonin, in physiological doses, significantly inhibited DU 145 cell proliferation and induced cell cycle withdrawal by accumulating cells in G0/G1 phase. The mRNA for Mel 1a receptors was found to be expressed in DU 145 cells; however, by radioreceptor assay, no binding sites for 125 I-melatonin could be detected in membrane preparations, suggesting that, in these cells, the level of translation of this mRNA is too low to possibly mediate the antiproliferative action of the hormone. In agreement with this hypothesis, melatonin did not affect forskolin-induced intracellular cAMP accumulation. Binding sites for 125 I-melatonin were found in nuclear extracts of DU 145 cells. CONCLUSIONS. Melatonin exerts a direct oncostatic activity on human androgenindependent prostate cancer cells, by affecting cell cycle progression. This activity seems to be mediated by nuclear, but not by membrane, receptors.

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“…However, after chronic duration-dependent exposure to melatonin, followed by rapid withdrawal of melatonin, the MT 1 receptors mediate a profound sensitisation of adenylate cyclase resulting in not only a significant increase in basal levels of cAMP, but also a potentiated increase in cAMP in response to a pituitary adenylate cyclase-activating polypeptide stimulatory hormone action (16,17). Such an effect may be physiologically important to the interpretation of the seasonal effect of melatonin on prolactin secretion from the pars distalis.Inhibition of cAMP by the melatonin receptor MT 1 has been demonstrated in a variety of heterologous cell systems, including NIH3T3 cells, HEK293 cells, mouse L-cells and Chinese hamster ovary (CHO) cells (12,(18)(19)(20). In CHO cells, melatonin has also been demonstrated to sensitise adenylate…”

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confidence: 99%

The Human MT₁ Melatonin Receptor Stimulates cAMP Production in the Human Neuroblastoma Cell Line SH‐SY5Y Cells Via a Calcium‐Calmodulin Signal Transduction Pathway

Schuster

Williams²,

Morris³

et al. 2005

J Neuroendocrinology

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Melatonin regulates circadian and seasonal physiology via melatonin receptors expressed in the brain. However, little is known about the signal transduction mechanisms that mediate the action of melatonin in neuronal cells. To begin to address this issue, we expressed the human MT(1) receptor in the human neuroblastoma SH-SY5Y cell line. In this cell line, melatonin acutely stimulated cAMP synthesis through a calcium-calmodulin dependent pathway. This stimulatory effect was independent of an interaction with G(i) or G(s) G proteins and dependent upon internal calcium stores. Melatonin also potentiated forskolin-activated cAMP synthesis. Differentiation of the neuroblastoma cells with retinoic acid to the neuronal phenotype did not alter the ability of melatonin to acutely stimulate cAMP. These data may be relevant to the neuronal action of melatonin and highlight the importance of the cellular context of expression of melatonin and other G protein-coupled receptors.

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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

Cited by 39 publications

References 19 publications

Cetrorelix, a Gonadotropin-Releasing Hormone Antagonist, Induces the Expression of Melatonin Receptor 1a in the Gonadotropin-Releasing Hormone Neuronal Cell Line GT1–7

Cetrorelix, a Gonadotropin-Releasing Hormone Antagonist, Induces the Expression of Melatonin Receptor 1a in the Gonadotropin-Releasing Hormone Neuronal Cell Line GT1–7

Growth-inhibitory activity of melatonin on human androgen-independent DU 145 prostate cancer cells

The Human MT₁ Melatonin Receptor Stimulates cAMP Production in the Human Neuroblastoma Cell Line SH‐SY5Y Cells Via a Calcium‐Calmodulin Signal Transduction Pathway

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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

Cited by 39 publications

References 19 publications

Cetrorelix, a Gonadotropin-Releasing Hormone Antagonist, Induces the Expression of Melatonin Receptor 1a in the Gonadotropin-Releasing Hormone Neuronal Cell Line GT1–7

Cetrorelix, a Gonadotropin-Releasing Hormone Antagonist, Induces the Expression of Melatonin Receptor 1a in the Gonadotropin-Releasing Hormone Neuronal Cell Line GT1–7

Growth-inhibitory activity of melatonin on human androgen-independent DU 145 prostate cancer cells

The Human MT1 Melatonin Receptor Stimulates cAMP Production in the Human Neuroblastoma Cell Line SH‐SY5Y Cells Via a Calcium‐Calmodulin Signal Transduction Pathway

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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

The Human MT₁ Melatonin Receptor Stimulates cAMP Production in the Human Neuroblastoma Cell Line SH‐SY5Y Cells Via a Calcium‐Calmodulin Signal Transduction Pathway