Microtubules modulate melatonin receptors involved in phase-shifting circadian activity rhythms: in vitro and in vivo evidence.
Microtubules modulate melatonin receptors involved in phase-shifting circadian activity rhythms: in vitro and in vivo evidence.
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DOI：
10.1111/j.1600-079x.2008.00644.x
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发表时间：
2009-03
影响因子：
10.3
通讯作者：
Witt-Enderby PA
中科院分区：
文献类型：
--
作者：
Jarzynka MJ;Passey DK;Johnson DA;Konduru NV;Fitz NF;Radio NM;Rasenick M;Benloucif S;Melan MA;Witt-Enderby PA
MT 1褪黑激素受体在中国仓鼠卵巢细胞中的表达仍然敏感的褪黑激素再挑战，即使在慢性褪黑激素暴露时，微管解聚的细胞，暴露，通常导致MT 1受体脱敏。我们将我们的研究结果扩展到MT 2褪黑激素受体，使用体外和体内方法。使用表达人MT 2褪黑激素受体的CHO细胞，与褪黑激素处理的细胞相比，微管解聚防止了受体的高效力状态的数量的损失。此外，微管解聚增加褪黑激素诱导的PKC活性，但不PI水解通过Gi蛋白类似于MT 1 R所示。此外，微管解聚在MT 2-CHO细胞增强交换GTP对Gi-蛋白使用GTP的光亲和类似物。为了测试微管是否能够调节褪黑激素诱导的相移，微管在Long Evans大鼠下丘脑的视交叉上核内特异性解聚，并且评估褪黑激素使其昼夜活动节律相移的功效，并与具有完整SCN微管的动物进行比较。我们发现，使用秋水仙胺或诺考达唑在SCN中的微管解聚增强了10 pM褪黑激素相移Long Evans大鼠的活动节律的功效。在β-光秋水仙碱（秋水仙胺的无活性类似物）存在下不发生增强。总之，这些数据表明，微管动力学可以调节褪黑激素诱导的昼夜活动节律的相移，这可以部分解释为什么昼夜节律紊乱发生在患有与微管紊乱相关的疾病的个体中。
MT1 melatonin receptors expressed in Chinese hamster ovary cells remain sensitive to a melatonin re-challenge even following chronic melatonin exposure when microtubules are depolymerized in the cell, an exposure that normally results in MT1 receptor desensitization. We extended our findings to MT2 melatonin receptors using both in vitro and in vivo approaches. Using CHO cells expressing human MT2 melatonin receptors, microtubule depolymerization prevents the loss in the number of high potency states of the receptor when compared to melatonin-treated cells. Additionally, microtubule depolymerization increases in melatonin-induced PKC activity but not PI hydrolysis via Gi proteins similar to that shown for MT1Rs. Furthermore, microtubule depolymerization in MT2-CHO cells enhances the exchange of GTP on Gi-proteins using a photoaffinity analog of GTP. To test whether microtubules are capable of modulating melatonin-induced phase-shifts, microtubules are depolymerized specifically within the suprachiasmatic nucleus of the hypothalamus of the Long Evans rat and the efficacy of melatonin to phase shift their circadian activity rhythms was assessed and compared to animals with intact SCN microtubules. We find that microtubule depolymerization in the SCN using either Colcemid or nocodazole enhances the efficacy of 10 pM melatonin to phase-shift the activity rhythms of the Long Evans rat. No enhancement occurs in the presence of β-lumicolchicine, the inactive analog of Colcemid. Taken together, these data suggest that microtubule dynamics can modulate melatonin-induced phase shifts of circadian activity rhythms which may explain, in part, why circadian disturbances occur in individuals afflicted with diseases associated with microtubule disturbances.