Rosenthal J J C, Gilly W F
Department of Physiology, UCLA School of Medicine, Los Angeles, California, USA.
Neurosignals. 2003 May-Jun;12(3):126-41. doi: 10.1159/000072160.
Our modern understanding of channels as discrete voltage-sensitive and ion-selective entities comes largely from a series of classical studies using the squid giant axon. This system has also been critical for understanding how transporters and synaptic transmission operate. This review outlines attempts to assign molecular identities to the extensively studied physiological properties of this system. As it turns out, this is no simple task. Molecular candidates for voltage-gated Na(+), K(+), and Ca(2+) channels, as well as ion transporters have been isolated from the squid nervous system. Both physiological and molecular approaches have been used to equate these cloned gene products with their native counterparts. In the case of the delayed rectifier K(+) conductance, the most thoroughly studied example, two major issues further complicate the equation. First, the ability of K(+) channel monomers to form heteromultimers with unique properties must be considered. Second, squid K(+) channel mRNAs are extensively edited, a process that can generate a wide variety of channel proteins from a common gene. The giant axon system is beginning to play an important role in understanding the biological relevance of this latter process.
我们如今将通道理解为离散的电压敏感型和离子选择性实体，这在很大程度上源于一系列使用枪乌贼巨大轴突的经典研究。该系统对于理解转运体和突触传递的运作方式也至关重要。这篇综述概述了为这个系统经过广泛研究的生理特性确定分子身份的尝试。事实证明，这并非一项简单的任务。电压门控钠通道、钾通道和钙通道以及离子转运体的分子候选物已从枪乌贼神经系统中分离出来。生理方法和分子方法都已被用于将这些克隆的基因产物与其天然对应物等同起来。以研究最为透彻的延迟整流钾电导为例，有两个主要问题使这种等同关系进一步复杂化。首先，必须考虑钾通道单体形成具有独特性质的异源多聚体的能力。其次，枪乌贼钾通道mRNA被广泛编辑，这一过程能够从一个共同基因产生各种各样的通道蛋白。巨大轴突系统在理解后一过程的生物学意义方面正开始发挥重要作用。
