Circadian regulation of ion dynamics and ageing: implications for the rhythmic proteome.

内源性时钟将生物体生理和行为组织成24小时（昼夜节律）节律，以适应白天和黑夜的不同生理需求。与外界时间的不一致，如时差或夜班工作，与癌症、糖尿病等疾病的风险增加以及过早衰老有关。每个细胞都有自己的时钟，它赋予从DNA复制和有丝分裂到蛋白质合成和降解的几个细胞过程昼夜节律性。我们发现Na+， K+和Cl-在质膜上有节奏地输入和输出，以渗透补偿细胞质可溶性蛋白丰度的日常变化。这种自我平衡控制机制防止了水的代偿性运动，而水会随着大分子含量的变化而变化，并允许细胞保持体积恒定。重要的是，我们发现需要一个完整的离子运输系统来适应新的蛋白质合成。与此相一致的是，对细胞内离子组成的操纵会影响mTORC1的活性，mTORC1是一种调节细胞代谢和生长以适应营养可用性的蛋白质复合物，从而阻止蛋白质翻译。在这项提议中，我们的目标是进一步研究细胞内离子组成调节mTORC1信号级联和蛋白质合成的机制，以及这如何重塑昼夜蛋白质组。我们还将分析渗透物和氨基酸对缓冲机制的贡献，以及它们的（节律性）丰度如何与mTORC1活性以及分解代谢和合成代谢过程之间的分配联系起来。最后，我们的初步数据表明，细胞内几种离子的丰度在年轻和年老小鼠之间发生了变化。因此，我们的目标是研究这种渗透缓冲机制如何受到年龄的影响，以及这如何影响体内的昼夜蛋白组。我们的研究结果将揭示将渗透调节与mTORC1活性和蛋白质组重塑联系起来的基本机制，并将对理解由异常蛋白质稳态（包括衰老）引起的许多疾病的病理生理学具有重要意义。

An endogenous clock organises organismal physiology and behaviour into 24-hour (circadian) rhythms, to accommodate the different physiological demands of day and night. The misalignment with the external time, as it occurs with jet lag or nightshift work is associated with an increased risk for diseases such as cancer and diabetes, and premature ageing. Each cell has its own clock, which confers circadian rhythmicity to several cellular processes from DNA replication and mitosis to protein synthesis and degradation. We found that Na+, K+, and, Cl- are rhythmically imported and exported across the plasma membrane to osmotically compensate for daily changes in cytosolic soluble protein abundance. This homeostatic control mechanism prevents the compensatory movement of water that would follow upon variation in macromolecule content and allows the cells to keep their volume constant. Importantly, we found that an intact ion transport system is required to accommodate new protein synthesis. In line with this, the manipulation of the intracellular ionic composition affects the activity of mTORC1, a protein complex that tunes cellular metabolism and growth to nutrient availability, thus preventing protein translation. In this proposal, we aim to further investigate the mechanisms by which the intracellular ionic composition regulates the mTORC1 signalling cascade and protein synthesis and how this remodels the circadian proteome. We will also analyse the contribution of osmolytes and amino acids to the buffering mechanism and how their (rhythmic) abundance links to mTORC1 activity and the partitioning between catabolic and anabolic processes. Finally, our preliminary data suggest that the intracellular abundance of several ions changes between young and old mice. Therefore, we aim to investigate how this osmotic buffering mechanism is affected by age and how this impacts the circadian proteome in vivo. Our findings will reveal fundamental mechanisms that link osmoregulation to mTORC1 activity and proteome remodelling and will have important implications for understanding the pathophysiology of many diseases caused by aberrant protein homeostasis, including ageing.