Pineal circadian clocks gate arylalkylamine N-acetyltransferase gene expression in the mouse pineal gland
Pineal circadian clocks gate arylalkylamine N-acetyltransferase gene expression in the mouse pineal gland
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DOI：
10.1111/j.1471-4159.2004.03008.x
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发表时间：
2005-04-01
影响因子：
4.7
通讯作者：
Liang, J
中科院分区：
文献类型：
--
作者：
Fukuhara, C;Yamazaki, S;Liang, J
人们认为哺乳动物的生物钟仅位于下丘脑的视交叉上核。最近的研究表明，某些大脑区域和周围组织也可能有内在的生物钟。然而，“外周生物钟”所扮演的角色尚未完全阐明。在本研究中，我们使用小鼠松果体研究了它们的功能，发现肾上腺素受体刺激后芳基烷基胺 N-乙酰转移酶（Aa-Nat，EC 2.3.1.87，褪黑素合成的限速酶）基因的表达取决于一天中的时间，甚至在体外（门控）也是如此。在褪黑激素充足和褪黑激素缺乏的小鼠松果体中均观察到相位依赖性 Aa-Nat 反应。磷酸二酯酶不太可能抑制 Aa-Nat 诱导，因为磷酸二酯酶抑制剂本身对 mRNA 水平没有影响。无论异丙肾上腺素存在或不存在，嘌呤霉素均不能有效诱导 Aa-Nat mRNA 水平，这表明新合成的蛋白质可能不需要控制 Aa-Nat 反应。我们还发现Period1-荧光素酶转基因小鼠松果体中Period1-发光的表达具有昼夜节律依赖性：生物钟可能在培养物中发挥作用。在没有异丙肾上腺素的情况下，Aa-Nat mRNA 水平没有表现出明显的昼夜节律，因此表明 Aa-Nat mRNA 水平是由肾上腺素能机制诱导的，而不是由松果体生物钟诱导的。我们的结果表明，松果体生物钟可能决定 Aa-Nat 基因表达对视交叉上核（例如，主生物钟）输入做出反应的时间。 g。肾上腺素能刺激。
In mammals it has been thought that the circadian clock localizes only in the suprachiasmatic nucleus of the hypothalamus. Recent studies have revealed that certain brain regions and peripheral tissues may also have intrinsic circadian clocks. However, the roles played by 'peripheral circadian clocks' have not been fully elucidated. In this study, we investigated their function using mouse pineal glands, and found that expression of the arylalkylamine N-acetyltransferase (Aa-Nat, EC 2.3.1.87, the rate-limiting enzyme of melatonin synthesis) gene after adrenergic receptor stimulation depended on the time of day even in vitro (gating). Phase-dependent Aa-Nat responses were observed in both melatonin-proficient and melatonin-deficient mouse pineal glands. Phosphodiesterases are unlikely to suppress Aa-Nat induction because a phosphodiesterase inhibitor itself had no effect on the mRNA levels. Puromycin was ineffective in inducing Aa-Nat mRNA levels in either the presence or absence of isoproterenol, suggesting that newly synthesized proteins may not be necessary to gate the Aa-Nat responses. We also discovered circadian dependence of the expression of Period1-luminescence in Period1-luciferase transgenic mouse pineal glands: circadian clocks may be functional in culture. Aa-Nat mRNA levels showed no significant circadian rhythms in the absence of isoproterenol, thus suggesting that Aa-Nat mRNA levels are induced by adrenergic mechanisms, not by a pineal circadian clock. Our results suggest that the pineal circadian clock may determine timing when Aa-Nat gene expression can respond to inputs from the master circadian clock in the suprachiasmatic nucleus, e. g. adrenergic stimulation.