Triphenylmethylphosphonium is an ion channel ligand of the nicotinic acetylcholine receptor.

Abstract

The lipophilic cation triphenylmethylphosphonium (Ph3MeP+), which is widely used as a sensor for membrane potential with cells, organelles and membrane vesicles, accumulates in membranes rich in nicotinic acetylcholine receptor [from Torpedo marmorata electric organ] in a voltage-independent way. Ph3MeP+ in this system is bound to a cation-binding site of the ion channel that is part of the acetylcholine receptor complex. Binding is stimulated by cholinergic effectors (Kd = 13 .mu.M in the absence of carbamoylcholine; Kd = 1.5 .mu.M in the presence of 10 .mu.M carbamoylcholine), and stimulation is blocked by .alpha.-bungarotoxin. Ph3MeP+ blocks efflux of 22Na from receptor-rich microsacs and appears to compete with the channel ligand phencyclidine for a common binding site. In contrast to the binding of other proven channel ligands, Ph3MeP+-binding is not affected by desensitization.