title: 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, is shown also to accumulate in membranes rich in nicotinic acetylcholine receptor in a voltage-independent way. Evidence is presented that 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 microM in the absence of carbamoylcholine; Kd = 1.5 microM in the presence of 10 microM carbamoylcholine), and this 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.
mesh_terms: D001693:Biological Transport, Active / Q000187:drug effects; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism*; D008024:Ligands; D008564:Membrane Potentials; D009861:Onium Compounds; D011950:Receptors, Cholinergic / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D014320:Triphenylmethyl Compounds / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D007473:Ion Channels; D008024:Ligands; D009861:Onium Compounds; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic; D014320:Triphenylmethyl Compounds; C011561:triphenylmethylphosphonium; D012964:Sodium