Desiphering the structural origins of functional multimodality in bacterial mechanosensitive ion channels

离子通道是生命科学的核心，因为它直接参与信号转导、衰老、癌症和神经变性。尽管对特定膜蛋白的结构和功能的基本理解取得了进展（1988年、1997年、2003年和2012年的诺贝尔化学奖），但这只是冰山一角。现在迫切需要开发新的触发器来控制致命病原体细胞膜上的毛孔，并解决抗菌素耐药性问题，这是全世界最常见的死亡原因。我们期望通过利用一种古老而普遍存在的离子通道调节机制来实现这一目标，这种机制被称为机械感觉。后者是膜蛋白感知脂质膜内发生的张力变化并通过改变其结构和功能对这些变化作出反应的能力。这一建议旨在获得机械感觉的基本认识，并破译其与其他形式的离子通道调节共存的分子基础。为此，我们将剖析形成其分子基础的各个步骤，并确定负责将压力感应能力传递给通道的常见但必要的结构元素。脂质膜在离子通道调节中的潜在影响的基本方面以及压力敏感通道的功能多功能性的生理作用将被阐明。为此，我们将确定独特的结构特征，这些结构特征允许机械敏感通道的功能多模态及其对其他刺激（如离子、pH值或特定分子）的响应能力，以及机械触发。在该项目中，我们将开发并遵循一种综合的多学科方法，以建立机械激活和配体门控之间的联系。拟议的研究将涉及使用一套最先进的结构（冷冻电子显微镜和X射线晶体学），生化（蛋白质纯化），生物物理（电子顺磁共振波谱和电生理学）和复杂的计算方法（分子动力学）来解决有关细菌机械敏感离子通道家族不同成员在分子水平上的机制和调节的问题。总的来说，我们期望将参与通道机械激活的膜内力转化为特定的分子刺激，这将模拟机械转导。类似于光遗传学，这是一个在过去几年里大规模发展的领域，它基于蛋白质与光的古老物理特性的相互作用，压力传感是自然界最基本的调节机制之一，将使一个全新的领域出现。

Ion channels are central to life sciences due to direct involvement in signal transduction, aging, cancer and neurodegeneration. Despite progress in the fundamental understanding of the structure and function of specific membrane proteins (Nobel Prizes in Chemistry 1988, 1997, 2003 and 2012), this has only been the tip of the iceberg. There is now an immediate need for the development of novel triggers to control pores in the cell membrane of deadly pathogens and tackle antimicrobial resistance, the most common cause of death worldwide. We anticipate to achieve that by exploiting an ancient and ubiquitous mechanism of ion channel regulation named mechanosensation. The latter is the ability of membrane proteins to sense tension changes occurring within the lipid membrane and respond to these by altering their structure and function. This proposal aims to gain a fundamental understanding of mechanosensation and decipher the molecular basis of its co-existence with other forms of ion channel regulation. To this end, we will dissect the individual steps that form its molecular basis and identify the common, but essential structural elements responsible to transduce pressure-sensing abilities to channels. The fundamental aspect of the underlying impact of the lipid membrane in ion channel regulation along with the physiological role of the functional versatility of pressure sensitive channels will be elucidated. To this end, we will identify the unique structural features which allow functional multimodality of mechanosensitive channels and their ability to respond to other stimuli, such as ions, pH or specific molecules, in addition to mechanical triggers. Within the project we will develop and follow an integrated multidisciplinary approach in order to establish a link between mechanical-activation and ligand-gating. The proposed studies will involve using a suite of state-of-the-art structural (Cryo Electron Microscopy and X -Ray crystallography), biochemical (Protein Purification), biophysical (Electron Paramagnetic Resonance spectroscopy and Electrophysiology) and sophisticated computational methods (Molecular Dynamics) to address questions pertaining to the mechanism and regulation of distinct members of the bacterial mechanosensitive ion channel family at a molecular level.Collectively, we anticipate to translate forces within the membrane participating in the mechanical activation of channels into specific molecular stimuli, which would mimic mechanotransduction. Similar to optogenetics, a field which has massively evolved over the last years and is based on the interaction of proteins with the ancient physical property of light, pressure sensing, one of nature's most fundamental regulatory mechanisms, would enable a radically novel field to emerge.