Subcellular trafficking, pentameric assembly, and subunit stoichiometry of neuronal nicotinic acetylcholine receptors containing f luorescently labeled α6 and α3 subunits. Mol Pharmacol 2008; 73

Neuronal nicotinic acetylcholine (ACh) receptors are ligand-gated, cation-selective ion channels. Nicotinic receptors con-taining 4, 6, 2, and 3 subunits are expressed in midbrain dopaminergic neurons, and they are implicated in the response to smoked nicotine. Here, we have studied the cell biological and biophysical properties of receptors containing 6 and 3 subunits by using fluorescent proteins fused within the M3-M4 intracellular loop. Receptors containing fluorescently tagged 3 subunits were fully functional compared with receptors with untagged 3 subunits. We find that 3- and 6-containing receptors are highly expressed in neurons and that they colo-calize with coexpressed, fluorescent 4 and 2 subunits in neuronal soma and dendrites. Förster resonance energy trans-fer (FRET) reveals efficient, specific assembly of 3 and 6 int