A Role for Leu118 of Loop E in Agonist Binding to the α7 Nicotinic Acetylcholine Receptor

Abstract

Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels mediating fast cholinergic synaptic transmission in the brain and at neuromuscular junctions. We used the structure of the acetylcholine binding protein from Lymnaea stagnalis to model the chicken ␣7 agonist-binding domain. The initial models and a preliminary docking study suggested that position Leu118 may play an important role in determining agonist actions on ␣7. A prediction from these in silico studies, that L118E and L118D would retain binding to acetylcholine but L118K and L118R would not, was confirmed in electrophysiological studies on functional recombinant mutant receptors expressed in Xenopus laevis oocytes. The functional studies also demonstrated that residues at position 118 have a dramatic effect on the actions of imidacloprid (a partial agonist of wild-type ␣7 receptors) and its des-nitro derivative. Molecular dynamics simulations confirmed that Leu118 can strongly influence agonist binding and that the model was robust in terms of its prediction for acetylcholine binding. Together, the results indicate a role for Leu118 in influencing agonist actions on ␣7 nAChRs.

Transcripts of the nicotinic acetylcholine receptor subunit gene Pxylα6 with premature stop codons are associated with spinosad resistance in diamondback moth, Plutella xylostella

“…We observed a putative novel editing site (4a, resulting in a S131G substitution), consistent with a previous report (Baxter et al 2010). Substituting serine with glycine at this position may affect protein folding or receptor function as it occurs in loop E, which is important for agonist binding (Amiri et al 2008). This putative editing site was only seen in G88, but not Wapio or Pearl-Sel, suggesting it is not involved in spinosad resistance.…”

A nicotinic acetylcholine receptor transmembrane point mutation (G275E) associated with resistance to spinosad in Frankliniella occidentalis

“…, ; Amiri et al . ). By comparing the functional properties of the vertebrate α7 nAChR containing a TM3 A272E mutation, it has been possible to demonstrate that this mutation has no significant effect on acetylcholine potency, as might be expected for a mutation located far from the extracellular binding site for acetylcholine.…”

Diverse Actions and Target-Site Selectivity of Neonicotinoids: Structural Insights

“…Because these amino acids are predicted to play a role in the agonist recognition, the effects of Leu118 mutations on the responses to ACh and imidacloprid were investigated. The L118E mutation almost completely blocked the response to imidacloprid, leaving the response to ACh, whereas the reverse was the case for L118K and L118R mutations (Amiri et al, 2008), suggesting a contribution to efficacy. Some insect nAChR ␣ subunits possess a basic residue at this position.…”