MICA Cryo-chronobiology: how do cold-inducible chaperones maintain neural clock function under brain temperature fluctuation?

生物钟是生命的基础，使我们适应环境中可预测的变化。这些生物钟的紊乱发生在几种脑部疾病中，包括痴呆——英国的主要死亡原因。了解时钟的工作原理意味着我们可以控制它们；一项应对一些最复杂的全球卫生挑战的新战略。在分子水平上，反馈回路支持全身细胞功能的每日“昼夜节律”。这些节律的24小时周期不受温度变化的影响，确保细胞时钟在不同的体温下不会加速或减慢。然而，值得注意的是，细胞时钟与体温的日常变化同步，这意味着它们必须感知并响应温度的变化。这种时钟装置的“温度悖论”仍然无法解释，特别是对于大脑，神经细胞的活动会产生大脑温度的快速变化。那么，当大脑温度发生变化时，是什么让我们的脑细胞时钟保持稳健的运转呢？昼夜节律和对寒冷的反应是在整个进化过程中保留的关键细胞功能。冷诱导伴侣蛋白（CICs）是一种在低温下具有高活性的蛋白；它们在通常会停止蛋白质生产的条件下保护关键细胞蛋白质的制造。CICs通过与我们每个细胞中DNA转录的信息结合，使这些信息可以翻译成对细胞生存至关重要的蛋白质，包括生物钟的组成部分。CIC活动也以昼夜节律的方式循环，响应体温的日常变化。我提出CIC-clock蛋白的相互作用对脑细胞的计时至关重要。我将测试这些相互作用是否需要在大脑温度变化时维持脑细胞时钟功能。来自脑损伤患者的数据表明，与体温一样，人脑温度也以24小时为周期循环。然而，大脑和体温是不一样的，我们需要知道健康的大脑发生了什么。在与爱丁堡成像公司的合作中，我将使用一种非侵入性核磁共振扫描技术来绘制健康志愿者在一天中不同时间的大脑温度图。同时，我会用无线电发射器远程监测老鼠的大脑温度周期。这些实验将建立正常的人类大脑温度范围，并分离昼夜节律和睡眠-觉醒周期对大脑温度节律的影响。剑桥大学的实验将确定在模拟大脑温度周期下，CIC与时钟蛋白破坏对脑细胞昼夜节律的影响。脑细胞时钟将通过在人类干细胞培养的脑细胞中标记CIC和时钟蛋白的发光报告来“在培养皿中”进行表征。这将使在不同温度下的几天内实时监测CIC和时钟蛋白的循环丰度以及它们之间的转换成为可能。然后，CIC和clock蛋白将被控制，使它们被困在细胞的不同部分，不能再相互作用。这种“捕获”将是完全可逆的，因此在温度变化期间可以打开或关闭cic时钟相互作用，以查看这对时钟功能的影响。最后，无线电发射机实验将在携带CIC和时钟蛋白基因突变的小鼠中重复进行。这项工作将为在痴呆症和其他慢性脑疾病的人类细胞模型中调节CIC-clock相互作用奠定基础。我预测增强CIC活动将保护和恢复脆弱脑细胞的生物钟功能。这项研究结果最终可能会为一系列昼夜节律紊乱的疾病带来新的治疗方法，也会为现代世界管理我们的“昼夜节律健康”带来新的方法。

Biological clocks are fundamental to life, adapting us to predictable changes in our environment. Disruption of these clocks occurs in several brain disorders including dementia - a leading cause of death in the UK. Understanding how clocks work means that we can control them; a fresh strategy to tackle some of our most complex global health challenges.At the molecular level, feedback loops support daily 'circadian' rhythms in cell function throughout the body. The 24-hour cycle of these rhythms is resistant to temperature variation, ensuring that cellular clocks do not speed up or slow down at different body temperatures. Remarkably however, cellular clocks synchronize to daily changes in body temperature, which means they must sense and respond to temperature shift. This 'temperature paradox' of the clockwork remains unexplained, especially for the brain where nerve cell activity produces rapid changes in brain temperature. What then keeps our brain cell clocks ticking robustly as brain temperature changes?Circadian rhythms and responses to cold are critical cellular functions that have been retained throughout evolution. Cold-inducible chaperones (CICs) are highly active proteins at cold temperatures; they safeguard the manufacture of key cellular proteins under conditions that would normally halt protein production. CICs do this by binding to messages transcribed from the DNA in each of our cells so that these messages can be translated into proteins that are critical for cell survival, including components of the clockwork. CIC activity also cycles in a circadian manner, responding to daily changes in body temperature. I propose that CIC-clock protein interactions are critical to timekeeping in brain cells. I will test whether these interactions are required to maintain brain cell clock function as brain temperature changes.Data from patients with brain injury show that, like body temperature, human brain temperature cycles with a 24-hour rhythm. However, brain and body temperature are not the same, and we need to know what happens in the healthy brain. In collaboration with Edinburgh Imaging, I will use a non-invasive MRI scan technique to map brain temperature in healthy volunteers at different times of the day. In parallel, I will monitor brain temperature cycles in mice remotely using radio transmitters. These experiments will establish normal human brain temperature ranges, and separate the effects of circadian and sleep-wake cycles on brain temperature rhythms.Experiments in Cambridge will then determine the impact of CIC versus clock protein disruption on brain cell circadian rhythms under simulated brain temperature cycles. The brain cell clock will be characterized 'in a dish' by tagging CIC and clock proteins with luminescent reporters in brain cells grown from human stem cells. This will make it possible to monitor the cyclic abundance of CIC and clock proteins in real time over several days at different temperatures, and during transitions between them. CIC and clock proteins will then be manipulated so that they are trapped in different parts of the cell and can no longer interact with each other. This 'trapping' will be entirely reversible such that CIC-clock interactions can be switched on or off during temperature shifts, to see what effect this has on clock function. Finally, radio transmitter experiments will be repeated in mice carrying genetic mutations in CIC and clock proteins. This work will establish a basis for modulating CIC-clock interactions in human cellular models of dementia and other chronic brain disorders. I predict that boosting CIC activity will protect and restore clock function in vulnerable brain cells. The results could ultimately lead to new treatments for a range of disorders in which circadian rhythms are disrupted, and also new ways to manage our 'circadian health' in the modern world.