Mechanistic analysis of dynamic scaffolding in a cellular signaling network

细胞通过复杂的蛋白质网络收集和处理有关外部世界的信息 以及我们称之为信号转导机制的小分子。的功能能力 转换设备通常是巨大的；微弱的输入信号可以被选择性地放大和过滤 对生理刺激的最佳感知和反馈控制层提供了复杂的调节 特性和对输出饱和的保护。例如，眼睛的感觉神经元可以 在黑暗适应的条件下，对单光子的吸收产生可靠的电响应，但 还可以调整增益以在明亮的日光条件下继续工作，而不会出现响应饱和。这个 我们研究计划的总体目标是了解信令系统如何为这样的功能 特征，以及疾病过程是如何由潜在机制的缺陷引起的。 在这个应用中，我们建议从机械上理解一种特定的大分子络合物，即 果蝇的视觉功能所必需的。该复合体由多个PDZ结构域蛋白组装而成，称为 我们最近的工作表明，这种蛋白质不是作为被动的支架，而是一种动态的 在视觉信号的时间尺度上经历光相关构象变化的机器。在 在这里提出的实验过程中，我们将(1)了解确切的生理过程 由INAD动力学控制，(2)定义光信号如何耦合到构象切换 INAD，(3)定义构象变化如何调节视觉输出，以及(4)进行研究，以了解 INAD组织信号分子的空间梯度。INAD已经成为一个经典的模型系统 以了解信号系统的大分子组织。我们期待这部作品将揭露 新的INAD功能机制，并将有助于解决目前的脚手架模型。 支架被认为可以提高许多细胞中信号事件的效率和特异性，并且 支架的缺陷与多种疾病过程有关，包括癌症、慢性 发炎和发育异常。通过展示支架蛋白如何也能 通过动态构象变化来塑造信号事件，这项工作应该有助于扩展我们的 了解细胞信号系统的正常和病理状态。

Cells collect and process information about the external world through elaborate networks of proteins and small molecules that we call the signal transduction machinery. The functional capability of the transduction machinery is often prodigious; weak input signals can be selectively amplified and filtered for optimal sensing of physiological stimuli, and layers of feedback control provide for complex regulatory characteristics and protection against output saturation. For example, sensory neurons of the eye can generate reliable electrical responses to the absorption of single photons under dark adapted conditions, but can also adjust the gain to continue operating in bright daylight conditions without response saturation. The overall goal of our research program is to understand how signaling systems provide for such functional characteristics, and how disease processes arise from defects in the underlying mechanisms. In this application, we propose to mechanistically understand a specific macromolecular complex that is required for visual function in Drosophila. The complex is assembled by a multi-PDZ domain protein called InaD, and our recent work shows that rather than acting as a passive scaffold, this protein is a dynamic machine that undergoes light-dependent conformational changes at the time scale of visual signaling. In the course of the experiments proposed here, we will (1) understand the exact physiological processes controlled by InaD dynamics, (2) define how light-signaling is coupled to the conformational switching of InaD, (3) define how the conformational change regulates the visual output, and (4) carry out studies to see if InaD organizes spatial gradients of signaling molecules. InaD has already served as a classic model system for understanding macromolecular organization of signaling systems. We expect that this work will expose new mechanisms of InaD function, and will help resolve current models for scaffolding in general. Scaffolding is thought to enhance the efficiency and specificity of signaling events in many cells, and defects in scaffolding have been associated with diverse disease processes, including cancer, chronic inflammaton, and developmental abnormalities. By showing how scaffolding proteins can alsoactively shape signaling events through dynamical conformational change, this work should help extend our understanding of the normal and pathological states of cellular signlaing systems.