Molecular mechanisms regulating the form and function of atypical calcium sensor proteins.

调节非典型钙传感器蛋白的形式和功能的分子机制。

• 批准号: RGPIN-2020-07171
• 负责人: Stathopulos, Peter
• 金额: $ 2.62万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=741639
• 关键词: Molecular; mechanisms; regulating; form; function

Cells with a discrete nucleus use calcium ions (Ca2+) to transmit signals that are an essential part of their lifecycle. These signals include both normal and danger responses such as reproduction, cell stress and death. All these cells have evolved a toolkit comprised of protein molecules that are tailored to sense Ca2+ changes in specific cellular compartments. Many toolkit components rely on vast differences in Ca2+ levels to mediate precise cell signals. For example, stromal interaction molecules (STIMs) are proteins located inside the cell on the endoplasmic reticulum (ER) membrane, which encloses a specialized compartment containing high Ca2+ levels. STIMs respond to the depletion of ER Ca2+ by interacting with Orai channel proteins located on the outside plasma membrane of the cell. This interaction causes Orai channels to open, permitting Ca2+ to move into the cell. Mitochondria take up this increased Ca2+ to influence intracellular Ca2+ signals and regulate the production of ATP, the energy currency of the cell. However, prolonged increases in mitochondrial Ca2+ can be catastrophic as cell death pathways are activated. Thus, mitochondria have evolved the use of the leucine zipper EF-hand containing transmembrane protein-1 (LETM1) protein to precisely control mitochondrial Ca2+ levels. Both STIMs and LETM1 contain a protein apparatus known as the EF-hand motif, which typically undergoes structural changes after interacting with Ca2+. These conformational changes trigger downstream protein-protein interactions and signal propagation. Remarkably, the STIM and LETM1 Ca2+ binding EF-hands appear to be atypically unpaired. Further, the manner that these EF-hands function based on the atomic compositions and the effects of environment-specific chemical modifications remain poorly understood. Thus, this research program aims to expose how single Ca2+ binding EF-hands have been integrated into cellular Ca2+ sensing components, how chemical modifications caused by cell stress effect sensitivities to Ca2+ and how the EF-hand structures and protein interaction targets change with and without Ca2+. Our research will provide new insights into key features that establish the specific Ca2+ sensory functions of STIMs and LETM1. Further, we will reveal the role of naturally occurring chemical modifications in modulating STIM function and provide the first atomic-level insights into how LETM1 EF-hand structure is related to function. Collectively, this knowledge will provide a framework for the development of new research tools, engineered to sense changes in Ca2+, cell stresses and control cellular responses, as well as drive future research hypothesis aimed at fully understanding the mechanistic basis for the ubiquitous STIM and LETM1 functions. The program will benefit Canada by providing multidisciplinary training for numerous diverse individuals, which will help secure future careers and innovations in the natural sciences.

具有离散核的细胞使用钙离子(Ca~(2+))来传递信号，这是它们生命周期的重要组成部分。这些信号既包括正常反应，也包括危险反应，如繁殖、细胞应激和死亡。所有这些细胞都进化出了一个由蛋白质分子组成的工具包，这些蛋白质分子是为感知特定细胞隔间的钙变化而量身定做的。许多工具箱组件依赖于钙离子水平的巨大差异来调节精确的细胞信号。例如，间质相互作用分子(STIMs)是位于细胞内内质网(ER)膜上的蛋白质，内质网(ER)膜包裹着一个含有高钙水平的特殊隔室。STIMs通过与位于细胞外质膜上的Orai通道蛋白相互作用来应对内质网钙离子的耗竭。这种相互作用导致Orai通道开放，允许钙离子进入细胞内。线粒体吸收这些增加的钙离子来影响细胞内的钙信号，并调节细胞能量流通ATP的产生。然而，随着细胞死亡途径的激活，线粒体钙离子的持续增加可能是灾难性的。因此，线粒体已经进化出利用亮氨酸拉链EF-Hand包含跨膜蛋白-1(LETM1)蛋白来精确控制线粒体的钙水平。STIMS和LETM1都含有一种被称为EF-Hand基序的蛋白质装置，它通常在与钙离子相互作用后经历结构变化。这些构象变化触发了下游蛋白质之间的相互作用和信号传播。值得注意的是，STIM和LETM1钙结合的EF手似乎不成对。此外，这些EF-HAND基于原子组成和环境特定化学修饰的影响发挥作用的方式仍然知之甚少。因此，本研究计划旨在揭示单个与钙离子结合的EF-Hand如何整合到细胞内的钙敏感成分中，细胞应激引起的化学修饰如何影响对Ca~(2+)的敏感性，以及EF-Hand的结构和蛋白质相互作用靶标在有和没有Ca~(2+)的情况下是如何变化的。我们的研究将为确定STIMS和LETM1的特定钙感受功能的关键特征提供新的见解。此外，我们将揭示自然发生的化学修饰在调节STIM功能中的作用，并首次在原子水平上深入了解LETM1 EF-Hand结构与功能的关系。总而言之，这些知识将为开发新的研究工具提供一个框架，这些工具旨在感知钙离子的变化、细胞压力和控制细胞反应，并推动未来的研究假设，旨在全面了解无处不在的STIM和LETM1功能的机制基础。该计划将为众多不同的个人提供多学科培训，从而使加拿大受益，这将有助于确保未来的职业生涯和自然科学领域的创新。