Structural biology of calcium channels

*所有活细胞都被由油性脂质制成的屏障所包围，该屏障用于保护细胞内容物的完整性，并将它们与环境中不受控制的变化隔离开来。然而，脂溶膜限制了大分子以及细胞生长和繁殖等各种活动所需的带正负电荷的小分子(离子)的交换或转移。生命需要细胞外和细胞内介质之间的持续交换。特别是，快速的生物反应是由于离子的通过，而离子的存在是由特殊的膜蛋白形成的水孔所催化的，这种孔道被称为“离子通道”。电压门控钙通道是执行基本生物任务的离子通道之一。这种纳米机器经过优化，专门用于在细胞中携带钙离子，必须在严格的限制内这样做，因为太多或太少的钙对细胞都是致命的。这种狭窄的操作范围可能在一定程度上解释了这种离子通道的复杂性，这种离子通道实际上是由多个蛋白质在一个大分子复合体中紧密相互作用组成的。这些辅助蛋白质或亚基调节离子的流动。其中一些蛋白质增加了离子通道的流量，另一些则减少了通过离子通道的离子数量。我们长期以来的目标是阐明每一种辅助蛋白质的性质以及它们在离子通道复合体中相互作用的性质。为了实现这一目标，我们多年来开发了结构生物学、生物化学和生物物理方面的特定工具来研究这些蛋白质。我实验室的研究使用精确的电子记录技术来研究钙离子在穿过钙通道和穿过细胞膜时的运动。我们还将钙离子的运动与这些蛋白质的初级和三维结构的变化联系起来。尽管这些蛋白质中的大多数已经被知道了20多年，但去年在这些蛋白质的结构生物学方面的最新进展揭示了一种相对未知的蛋白质，称为伽马亚基，它可能在骨骼肌的功能中发挥决定性作用。因此，这项研究旨在了解骨骼肌中蛋白质-蛋白质与钙通道相互作用的性质和特异性，以便更好地了解这一伽马亚基如何调节细胞膜上的钙流动。这项拟议的研究最终将提供组织特异性蛋白质网络的结构基础，该网络负责引导钙离子通过细胞膜。

***All living cells are surrounded by a barrier made out of oily lipids that serves to protect the integrity of the cell contents and isolate them from uncontrolled variations from the environment. The liposoluble membrane however limits the exchange or transfer of large molecules as well as small negatively and positively charged molecules (ions) which are needed by the cell for various activities including growth and reproduction. Life requires constant exchange between the extracellular and the intracellular media. In particular, fast biological responses result from the passage of ions that is catalyzed by the presence of aqueous pores that are formed by specialized membrane proteins called “ion channels”. The voltage-gated calcium channel is one of those ion channels that perform an essential biological task. This nanomachine is optimized to specifically carry calcium ions in the cell and must do so within strict limits because too much or too little calcium is lethal to the cell. This narrow range of operation could account in part for the complexity of this ion channel that is in fact made of multiple proteins interacting tightly within a macromolecular complex. These auxiliary proteins or subunits regulate the flow of ions. Some of these proteins increase the flow and some decrease the amount of ions going through the ion channel. It has been our long time goal of elucidate the nature of each of these auxiliary proteins and the nature of their interaction within the ion channel complex. To reach this goal, we have developed over the years specific tools in structural biology, biochemistry and biophysics to study these proteins. Research in my lab uses precise electrical recording techniques to study the movement of calcium, as they move through the calcium channel and across the cell membrane. We are also correlating the movement of calcium ions with changes in the primary and tri-dimensional structure of these proteins. Although most of these proteins have been known for more than 20 years, recent advances in the structural biology of these proteins last year have revealed a relatively unknown protein called the gamma subunit that may play a determinant role in the function of the skeletal muscle. The proposed research is thus aimed at understanding the nature and the specificity of the protein -protein interactions with the calcium channel in the skeletal muscle in order to better understand how this gamma subunit modulates calcium fluxes through the cell membrane. The proposed research will ultimately provide the structural basis underlying the tissue-specific protein networks responsible to conduct calcium ions through the cell membrane.