Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK.
Curr Biol. 2009 Dec 15;19(23):2031-6. doi: 10.1016/j.cub.2009.10.024. Epub 2009 Nov 12.
The central circadian pacemaker of the suprachiasmatic nucleus (SCN) is characterized as a series of transcriptional/posttranslational feedback loops. How this molecular mechanism coordinates daily rhythms in the SCN and hence the organism is poorly understood. We conducted the first systematic exploration of the "circadian intracellular proteome" of the SCN and revealed that approximately 13% of soluble proteins are subject to circadian regulation. Many of these proteins have underlying nonrhythmic mRNAs, so they have not previously been noted as circadian. Circadian proteins of the SCN include rate-limiting factors in metabolism, protein trafficking, and, intriguingly, synaptic vesicle recycling. We investigated the role of this clock-regulated pathway by treating organotypic cultures of SCN with botulinum toxin A or dynasore to block exocytosis and endocytosis. These manipulations of synaptic vesicle recycling compromised circadian gene expression, both across the SCN as a circuit and within individual SCN neurons. These findings reveal how basic cellular processes within the SCN are subject to circadian regulation and how disruption of these processes interferes with SCN cellular pacemaking. Specifically, we highlight synaptic vesicle cycling as a novel point of clock cell regulation in mammals.
视交叉上核（SCN）的中央生物钟起搏器的特征是一系列转录/翻译后反馈回路。目前人们对这种分子机制如何协调 SCN 中的日常节律以及机体节律知之甚少。我们首次对 SCN 的“生物钟细胞内蛋白质组”进行了系统探索，结果表明约 13%的可溶性蛋白受到节律调节。这些蛋白质中的许多都有潜在的非节律性 mRNA，因此以前并未被认为是节律性的。SCN 的生物钟蛋白包括代谢、蛋白质运输中的限速因子，以及有趣的是突触小泡再循环。我们通过用肉毒杆菌毒素 A 或 dynasore 处理 SCN 器官型培养物来阻断胞吐作用和胞吞作用，从而研究了这条时钟调节途径的作用。这些对突触小泡再循环的操作破坏了整个 SCN 作为一个回路以及单个 SCN 神经元中的节律基因表达。这些发现揭示了 SCN 内的基本细胞过程如何受到节律调节，以及这些过程的中断如何干扰 SCN 细胞的起搏。具体而言，我们强调了突触小泡循环作为哺乳动物中时钟细胞调节的一个新的关键点。
