Understanding the interplay between osmotic stress response and ion homeostasis in Saccharomyces cerevisiae: An approach integrating in-vivo imaging, microfluidics and mathematical modeling.

酿酒酵母的高渗胁迫反应是微生物中研究最多的胁迫适应机制之一。它允许细胞在外部渗透压增加的条件下生长，例如在细胞周围的液体蒸发的情况下。通过高渗透压甘油（HOG）信号级联实现适应，其促进小渗透压甘油的产生，从而增加细胞内渗透压。除了保持渗透平衡外，细胞还必须确保细胞内离子浓度保持在特定范围内，因为某些离子是不同生理功能所需的，而其他离子在高浓度下是有毒的。细胞通过各种离子特异性膜转运蛋白和泵实现离子稳态，这些转运蛋白和泵根据离子条件进行调节。这两种调节机制是相互联系的，因为离子浓度的变化也会对渗透压产生影响。此外，两种适应机制之间存在几种已知的相互作用，例如响应HOG途径激活的离子转运蛋白表达的变化。虽然这两个系统已经被研究了非常详细的隔离，一个整体的画面，这两个如何一起工作，以实现动态平衡仍然是hailey.In这项研究中的相互作用的调节和离子动态平衡系统将探索通过开发一个完整的系统的综合数学模型。该模型将基于一组丰富的体内离子浓度测量值，以响应外部渗透压和离子浓度的各种扰动。将使用荧光传感器蛋白或染料在体内监测离子浓度和膜电位变化，其甚至允许量化单细胞中的离子浓度变化。还将使用荧光蛋白观察信号传导活性和基因表达。外部离子浓度和渗透压将使用微流体装置来控制，微流体装置提供了产生精确且随时间变化的输入信号的可能性，这将有助于破译系统的动态。这些先前不可用的离子浓度的体内测量与微流体装置的先进刺激方法相结合，将使开发奥斯莫和离子调节系统的综合模型成为可能，这将有助于理解这两个系统如何共同作用以实现体内平衡。

The hyperosmotic stress response in Saccharomyces cerevisiae is one of the best studied stress adaptation mechanisms in a microorganism. It allows cells to grow in conditions where the external osmolarity increases, for example in case the liquid surrounding of the cell is evaporating. Adaptation is achieved via the high osmolarity glycerol (HOG) signaling cascade, which promotes the production of the small osmolyte glycerol, thereby increasing intracellular osmolarity. In addition to keeping osmotic balance, cells also have to ensure that intracellular ion concentrations are held within specific bounds, since certain ions are required for different physiological functions, while others are toxic at high concentrations. Cells achieve ion homeostasis via various ion specific membrane transporters and pumps, which are regulated according to ionic conditions. The two regulation mechanisms are linked, since ion concentration changes will also have an impact on osmotic pressure. In addition there are several known interactions between the two adaptation mechanisms, for example changes in ion transporter expression in response to HOG pathway activation. While both systems have been studied in great detail in isolation, a holistic picture of how the two work together in order to achieve homeostasis is remains elusive.In this study the interplay of the osmoregulation and the ion homeostasis system will be explored by developing an integrative mathematical model of the complete system. The model will be based on a wealth set of in vivo ion concentration measurements in response to various perturbations of external osmolarity and ion concentrations. Ion concentration- and membrane potential changes will be monitored in vivo using fluorescent sensor proteins or dyes, which even allow to quantify ion concentration changes in single cells. Also signaling activity and gene expression will be observed using fluorescent proteins. External ion concentrations and osmotic pressure will be controlled using a microfluidic device, which provides the possibility to generate precise and time-varying input signals, which will facilitate deciphering the dynamics of the system. These previously unavailable in vivo measurements of ion concentrations in combination with the advanced stimulation methods of a microfluidic device will make it possible to develop an integrative model of the osmo- and ion regulation systems, that will help to understand how the two systems act together in order to achieve homeostasis.