Spatiotemporal modeling of signal transduction in yeast

描述（由申请人提供）：检测和响应信号分子的空间梯度的能力是真核细胞中许多生物过程的基础，例如分化、迁移和形态发生。虽然人们对信号传导和梯度传感所需的蛋白质了解很多，但它们相互作用以传递有关环境的信息并产生蛋白质活性内部梯度的精确机制仍不清楚。该建议旨在建立受体内吞作用在调节信号传导活性和酿酒酵母（酵母）的交配反应中的梯度传感的作用。酵母根据信息素的浓度进行发育决策。在高水平的信息素，他们的生长停滞，并产生一个交配投影（“shmoo”形态）。在中等浓度下，它们在增加信息素梯度的方向上伸长（化养生长）。这一决定需要交配反应途径传递有关外部信息素浓度的定量信息。通过数学建模和实验分析相结合，我们积累了强有力的证据来支持的想法，信息素浓度的信号活动的幅度，但作为信号持续时间的信息传输。该建议的一个目标是检验受体内吞作用在这种“剂量-持续时间”转换中起重要作用的假设。一些实验和理论研究表明，受体的内吞作用是建立细胞极性的重要。最近的理论研究也表明，受体内吞作用增加细胞的能力，以检测信号分子的外部梯度。第二个目标是测试受体内吞作用增加酵母检测信息素梯度和跟踪随时间变化的梯度的能力的假设。具体目标是：目标1。描述受体内吞作用在调节信号活性中的作用。这一目的检验了受体内吞作用提供了剂量-持续时间编码机制的假设。数学建模与实验方法相结合，比较野生型和定义的酵母突变株的信号活性和响应。目标2.描述受体内吞作用在梯度感应中的作用。这一目标使用数学和实验方法来测试的假设，受体内吞作用增加酵母的能力，检测信息素梯度。目标3.描述酵母对变化的外部条件的反应能力。这一目标测试的假设，受体内吞作用允许酵母跟踪时间依赖性信息素梯度。我们最近开发了一种微流体装置，可以及时调节梯度的方向，这是我们研究酵母跟踪不断变化的环境条件的能力的实验设计的一个关键特征。 公共卫生相关性：检测和响应信号分子的空间梯度的能力对于真核细胞中的许多生物学过程（例如分化、迁移和形态发生）是基本的。本项目旨在将联合收割机计算方法与实验分析相结合，以开发酵母中信号和梯度传感的预测模型。由于酵母长期以来一直是人类激素、神经递质和感觉反应的原型，这些研究的结果可能最终导致治疗人类疾病的新策略。

DESCRIPTION (provided by applicant): The ability to detect and respond to spatial gradients of signaling molecules is fundamental for many biological processes in eukaryotic cells, such as differentiation, migration and morphogenesis. While much is known about the proteins that are required for signal transduction and gradient sensing, the precise mechanism by which they interact to transmit information about the environment and create internal gradients of protein activity remain unclear. This proposal seeks to establish the role of receptor endocytosis in modulating signaling activity and gradient sensing in the mating response of Saccharomyces cerevisiae (yeast). Yeast undergo a developmental decision based on the concentration of pheromone. At high pheromone levels, they growth arrest and generate a mating projection ("shmoo" morphology). At intermediate concentrations they elongate in the direction of an increasing pheromone gradient (chemotrophic growth). This decision requires that the mating response pathway transmit quantitative information about the external pheromone concentration. Through a combination of mathematical modeling and experimental analysis we accumulated strong evidence to support the idea that information about pheromone concentration is transmitted not as the amplitude of signal activity but as signal duration. One goal of this proposal is to test the hypothesis that receptor endocytosis plays an important role in this "dose-to-duration" conversion. Several experimental and theoretical investigations have suggested that receptor endocytosis is important for establishing cell polarity. Recent theoretical investigations also have suggested that receptor endocytosis increase cell's ability to detect external gradients of signaling molecules. A second goal is to test the hypothesis that receptor endocytosis increases yeast's ability to detect pheromone gradients and track gradients that change in time. The specific aims are: Aim 1. Characterize the role of receptor endocytosis in modulating signal activity. This aim tests the hypothesis that receptor endocytosis provides a mechanism for dose-to-duration encoding. Mathematical modeling is combined with experimental approaches to compare signal activity and responses in wild-type and defined mutant strains of yeast. Aim 2. Characterize the role of receptor endocytosis in gradient sensing. This aim uses mathematical and experimental approaches to test the hypothesis that receptor endocytosis increases yeast's ability to detect a pheromone gradient. Aim 3. Characterize yeast's ability to respond to changing external conditions. This aim tests the hypothesis that receptor endocytosis allows yeast to track time-dependent pheromone gradients. Our recent development of a microfluidics device that allows the direction of a gradient to be modulated in time is a critical feature of our experimental design for investigating yeast's ability to track changing environmental conditions. PUBLIC HEALTH RELEVANCE: The ability to detect and respond to spatial gradients of signaling molecules is fundamental for many biological processes in eukaryotic cells, such as differentiation, migration and morphogenesis. This project seeks to combine computational approaches with experimental analysis to develop predictive models of signaling and gradient sensing in yeast. Because yeast has long served as a prototype for hormone, neurotransmitter and sensory responses in humans, the results of these investigations may ultimately lead to novel strategies for treating human disease.