Targeted Mutations Activate Allosteric Modulation of α5-Containing Nicotinic Acetylcholine Receptors.

Nicotinic acetylcholine receptors play vital roles in neuronal communication. The α5 subunit is unique, in that it assembles only into the auxiliary position (the "5th" subunit of the pentamer) of a functional receptor, yet it can have a substantial effect on a receptor's physiological response. In addition, it is expressed in reward and aversive pathways, highlighting its importance in nicotine dependence. The novel α5-α4 interface seems well positioned for selective small molecule binding, yet no agonist activation has been observed. Here, we mutate the α5 subunit to mimic the α4 residues at the agonist binding site. Although no direct activation is observed from several agonists (acetylcholine, nicotine, and cytisine), we were able to modulate the receptor signal response through the introduction of NS9283, a positive allosteric modulator.