Melatonin-mediated regulation of human MT1 melatonin receptors expressed in mammalian cells
Melatonin-mediated regulation of human MT1 melatonin receptors expressed in mammalian cells
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DOI：
10.1016/j.bcp.2004.01.027
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发表时间：
2004-06-01
影响因子：
5.8
通讯作者：
Dubocovich, ML
中科院分区：
文献类型：
--
作者：
Gerdin, MJ;Masana, MI;Dubocovich, ML
在哺乳动物中，松果体激素褪黑激素激活G蛋白偶联的MT 1和MT 2褪黑激素受体。急性暴露的重组MT1和MT2褪黑激素受体的超生理浓度的褪黑激素差异调节这两个受体的MT2，但不是MT1，表现出快速脱敏和内化。在本研究中，我们试图确定是否长期暴露于超生理和生理浓度的褪黑激素脱敏和/或内化的MT 1褪黑激素受体。使用稳定表达MT 1-FLAG或瞬时表达MT 1-绿色荧光蛋白（GFP）褪黑激素受体的中国仓鼠卵巢（CHO）细胞系，我们发现，长时间（8 h）暴露于超生理浓度的褪黑激素（100 nM）显著增加了MT 1褪黑激素受体的数量，并降低了褪黑激素与2-[I-125]碘褪黑激素竞争的亲和力（K-i）。类似的处理也使MT 1褪黑激素受体介导的刺激[S-35] GTP γ S结合脱敏，但不使受体内化。相比之下，长期暴露于模拟夜间水平（400 pM）的褪黑激素浓度并不影响MT 1褪黑激素受体的数量，褪黑激素的亲和力，或受体的功能敏感性。我们的结论是，在体内内源性褪黑激素并不显着影响MT1褪黑激素受体的功能敏感性，然而，外源性褪黑激素治疗剂量高于生理水平可以脱敏的受体，从而影响介导的生理反应后激活MT1褪黑激素受体。(C)2004爱思唯尔公司All rights reserved.
In mammals, the pineal hormone melatonin activates G protein-coupled MT1 and MT2 melatonin receptors. Acute exposure of recombinant MT1 and MT2 melatonin receptors to supraphysiological concentrations of melatonin differentially regulates these two receptors with the MT2, but not the MT1, exhibiting rapid desensitization and internalization. In the present study, we sought to determine whether prolonged exposure to supraphysiological and physiological concentrations of melatonin desensitized and/ or internalized the MT1 melatonin receptor. Using a Chinese hamster ovary (CHO) cell line stably expressing MT1-FLAG or transiently expressing MT1-green fluorescent protein (GFP) melatonin receptors, we found that prolonged exposure (8 h) to supraphysiological concentrations of melatonin (100 nM) significantly increased the number of MT1 melatonin receptors and decreased the affinity (K-i) of melatonin for competition for 2-[I-125]iodomelatonin. A similar treatment also desensitized the MT1 melatonin receptor-mediated stimulation of [S-35]GTPgammaS binding, but did not internalize the receptor. In contrast, prolonged exposure to a concentration of melatonin mimicking nocturnal levels (400 pM) did not affect the number of MT1 melatonin receptors, the affinity for melatonin, or the functional sensitivity of the receptor. We conclude that in vivo endogenous melatonin does not significantly affect the functional sensitivity of MT1 melatonin receptors, however, exogenous melatonin taken therapeutically at doses above physiological levels could desensitize the receptor thereby affecting physiological responses mediated following activation of MT1 melatonin receptors. (C) 2004 Elsevier Inc. All rights reserved.