Evolutionary biochemistry of pentameric ligand-gated ion channels

在最基本的层面上，我们的神经系统是一个由被称为神经元的特殊细胞组成的复杂回路，它们通过电信号相互交流。这个过程依赖于嵌入在神经元膜上的蛋白质，称为离子通道，其活动既产生又传播这些电信号。数十亿年的进化导致了惊人的离子通道多样性，不同类型的离子通道在各种刺激下打开和关闭。配体门控离子通道，在结合小的化学配体时打开，是大自然的终极分子传感器。它们通过将小分子的结合与跨膜离子传导孔的打开相结合，将化学信号转化为电脉冲。我新的研究计划的短期目标是了解配体门控离子通道功能的机制。从长远来看，这一见解将用于指导具有独特化学特异性的配体门控离子通道的工程设计。这些基于配体门控离子通道的“生物传感器”将被遗传编码，这意味着它可以无缝地集成到未来基于细胞的治疗和诊断系统中。我们设计配体门控离子通道生物传感器的能力受到目前我们对通道结构、功能和机制的理解差距的限制。为了揭示神秘的配体门控离子通道功能的结构和机制基础，该研究将由研究生和本科生组成的团队进行，将一种新的创新进化生物化学方法与单分子生物物理实验相结合。进化生物化学方法包括绘制蛋白质的进化史，以追踪氨基酸序列的变化，这些变化产生了现代蛋白质的功能。重构了祖先配体门控离子通道的氨基酸序列，使这些祖先通道能够在单分子水平上“复活”和表征。这种新兴的方法代表了一种探索配体门控离子通道氨基酸序列的合理方法，以阐明阻碍传统方法的结构-功能关系。结果将更好地理解配体门控离子通道结构和功能的基本方面，这将为设计具有独特性能的通道打开大门，用于化学生物传感器。这些基因编码的生物传感器将具有广泛的诊断、治疗和工业应用，为加拿大人带来社会经济效益。

At its most basic level our nervous system is an intricate circuit of specialized cells called neurons that communicate with each other using electrical signals. This process relies on proteins embedded in the neuronal membrane, called ion channels, whose activity both generates and propagates these electrical signals. Billions of years of evolution have led to a staggering array of ion channel diversity, with different ion channel types opening and closing in response to a variety of stimuli.Ligand-gated ion channels, which open upon binding small chemical ligands, are Nature's ultimate molecular sensors. They convert chemical signals into electrical impulses by coupling the binding of small molecules to the opening of a membrane-spanning ion conducting pore. The short-term goal of my new research program is to understand mechanisms of ligand-gated ion channel function. In the long-term, this insight will be used to guide the engineering of ligand-gated ion channels with unique chemical specificities. These ligand-gated ion channel-based “biosensors” will be genetically encoded, meaning that can be seamlessly integrated into future cell-based therapeutic and diagnostic systems.Our ability to engineer ligand-gated ion channel biosensors is limited by current gaps in our understanding of channel structure, function, and mechanism. To uncover the structural and mechanistic basis of enigmatic ligand-gated ion channel functions, the proposed research, which will be carried out by a team of graduate and undergraduate students, will couple a new and innovative evolutionary biochemistry approach to single molecule biophysical experiments. The evolutionary biochemistry approach involves charting the evolutionary history of proteins, in order to trace the changes in amino acid sequence that gave rise to modern day protein functions. The amino acid sequences of ancestral ligand-gated ion channels are reconstructed so that these ancestral channels can be “resurrected” and characterized at the single molecule level. This new and emerging approach represents a rational way of exploring ligand-gated ion channel amino acid sequences, in order to illuminate structure-function relationships that have stymied conventional approaches. The result will be a better understanding of fundamental aspects of ligand-gated ion channel structure and function, which will open the door to designing channels with unique properties for use as chemical biosensors. These genetically encoded biosensors will have broad diagnostic, therapeutic and industrial applications, leading to socio-economic benefits for Canadians.