Insights into channel function via channel dysfunction

Abstract

The nicotinic synapse has been a touchstone for advances in neuroscience ever since Jean Nicot, the French ambassador to Portugal, sent some tobacco seeds home to Paris in 1550 with a note that the New World plant had interesting effects when smoked. Now the muscle nicotinic acetylcholine receptor (nAChR) is a well-studied example of ligand-gated ion channels. After a motor neuron is stimulated, the nerve impulse reaches the presynaptic terminal, where it evokes release of acetylcholine (ACh) into the synapse. The nAChR depolarizes the postsynaptic muscle and triggers muscle action potentials; muscle contraction follows. To date, several nAChR subtypes have been successfully isolated, purified, imaged, and expressed, and unitary currents have been recorded from these channels (1). Researchers continue to unravel the molecular mechanisms of these macromolecules that are embedded in membranes at vertebrate nerve-muscle synapses, at invertebrate nicotinic synapses (which explains why nicotine-producing tobacco plants have a select advantage against invertebrate pests), and in the vertebrate central system (which explains Jean Nicot's fascination with those leaves). However, the precise structural events that trigger channel opening or "gating" remain mostly unknown.

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