Molecular Biology of Neural Signaling — Structure and Function of Ionic Channels

Abstract

A new approach to understanding the molecular mechanism of neural signaling has been provided by recombinant DNA technology. Thus, the structure and function of proteins constituting neural elements are being elucidated. These proteins include the nicotinic acetylcholine receptor and the sodium channel which represent ligandgated and voltage-gated ionic channels, respectively. These ionic channels mediate neural signaling by modulating the ion permeability of electrically excitable membranes. The primary structures of the acetylcholine receptor and the sodium channel have been deduced by cloning DNAs complementary to the messenger RNAs coding for the constituent polypeptides, followed by nucleotide sequence analysis of the cDNAs. The cDNAs encoding the acetylcholine receptor subunits have been expressed to generate the functional receptor. This expression system, in conjunction with alteration of the receptor structure by manipulations at the cDNA level, has made it possible to investigate the structure-function relationship of the receptor. These structural and functional studies, as well as the evolution of the ionic channels, will be discussed in this paper.