Resolving the structural basis for developmental changes in muscle ACh receptor function: it takes nerve.

The nicotinic acetylcholine (ACh) receptor undergoes extensive alterations in functional properties during muscle development. One such alteration, the developmental acquisition of the 'junctional' form of the channel, has been attributed to post-translational modification of pre-existing 'non-junctional' receptor channels. However, the discovery that a switch between the epsilon- and gamma-subunits of the muscle ACh receptor results in the 'junctional' form of the channel suggests a transcriptional mechanism of control. Although this issue is by no means settled, recent molecular biological and electrophysiological studies offer new ideas as to how innervation regulates the expression of functionally distinct forms of this receptor/channel.