Sleep is evolutionarily conserved, thus studying simple invertebrates such as Caenorhabditis elegans can provide mechanistic insight into sleep with single cell resolution. A conserved pathway regulating sleep across phylogeny involves cyclic adenosine monophosphate (cAMP), a ubiquitous second messenger that functions in neurons by activating protein kinase A. C. elegans sleep in response to cellular stress caused by environmental insults [stress-induced sleep (SIS)], a model for studying sleep during sickness. SIS is controlled by simple neural circuitry, thus allowing for cellular dissection of cAMP signaling during sleep. We employed a red-light activated adenylyl cyclase, IlaC22, to identify cells involved in SIS regulation. We found that pan-neuronal activation of IlaC22 disrupts SIS through mechanisms independent of the cAMP response element binding protein. Activating IlaC22 in the single DVA interneuron, the paired RIF interneurons, and in the CEPsh glia identified these cells as wake-promoting. Using a cAMP biosensor, epac1-camps, we found that cAMP is decreased in the RIF and DVA interneurons by neuropeptidergic signaling from the ALA neuron. Ectopic overexpression of sleep-promoting neuropeptides coded by flp-13 and flp-24, released from the ALA, reduced cAMP in the DVA and RIFs, respectively. Overexpression of the wake-promoting neuropeptides coded by pdf-1 increased cAMP levels in the RIFs. Using a combination of optogenetic manipulation and in vivo imaging of cAMP we have identified wake-promoting neurons downstream of the neuropeptidergic output of the ALA. Our data suggest that sleep- and wake-promoting neuropeptides signal to reduce and heighten cAMP levels during sleep, respectively.

中文翻译：

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秀丽隐杆线虫压力诱导睡眠期间，中间神经元通过环磷酸腺苷信号调节运动静止。

睡眠在进化上是保守的，因此研究秀丽隐杆线虫等简单无脊椎动物可以通过单细胞分辨率提供对睡眠机制的深入了解。整个系统发育过程中调节睡眠的保守途径涉及环磷酸腺苷 (cAMP)，它是一种普遍存在的第二信使，通过激活蛋白激酶 AC 来在神经元中发挥作用。研究生病期间睡眠的模型。SIS 由简单的神经回路控制，从而允许在睡眠期间对 cAMP 信号进行细胞解析。我们使用红光激活的腺苷酸环化酶 IlaC22 来鉴定参与 SIS 调节的细胞。我们发现 IlaC22 的全神经元激活通过独立于 cAMP 反应元件结合蛋白的机制破坏 SIS。激活单个 DVA 中间神经元、成对的 RIF 中间神经元和 CEPsh 神经胶质细胞中的 IlaC22，将这些细胞识别为促进唤醒的细胞。使用 cAMP 生物传感器 epac1-camps，我们发现 RIF 和 DVA 中间神经元中的 cAMP 通过来自 ALA 神经元的神经肽能信号传导而减少。由 ALA 释放的 flp-13 和 flp-24 编码的促睡眠神经肽异位过度表达，分别降低 DVA 和 RIF 中的 cAMP。pdf-1 编码的促醒神经肽的过度表达会增加 RIF 中的 cAMP 水平。通过结合光遗传学操作和 cAMP 体内成像，我们已经确定了 ALA 神经肽能输出下游的唤醒神经元。我们的数据表明，促进睡眠和促进觉醒的神经肽分别发出信号，在睡眠期间降低和提高 cAMP 水平。