Functional and Structural Interaction of (−)-Reboxetine with the Human α4β2 Nicotinic Acetylcholine Receptor

Abstract

The interaction of the selective norepinephrine reuptake inhibitor (2)-reboxetine with the human a4b2 nicotinic acetylcholine receptor (nAChR) in different conformational states was studied by several functional and structural approaches. Patch-clamp and Ca 21-influx results indicate that (2)-reboxetine does not activate ha4b2 nAChRs via interaction with the orthosteric sites, but inhibits agonist-induced ha4b2 activation by a noncompetitive mechanism. Consistently, the results from the electrophysiologybased functional approach suggest that (2)-reboxetine may act via open channel block; therefore, it is capable of producing a usedependent type of inhibition of the ha4b2 nAChR function. We tested whether (2)-reboxetine binds to the luminal [ 3 H]imipramine site. The results indicate that, although (2)-reboxetine binds with low affinity to this site, it discriminates between the resting and desensitized ha4b2 nAChR ion channels. Patch-clamp results also indicate that (2)-reboxetine progressively inhibits the ha4b2 nAChR with two-fold higher potency at the end of one-second application of agonist, compared with the peak current. The molecular docking studies show that (2)-reboxetine blocks the ion channel at the level of the imipramine locus, between M2 rings 69 and 149. In addition, we found a (2)-reboxetine conformer that docks in the helix bundle of the a4 subunit, near the middle region. According to molecular dynamics simulations, (2)-reboxetine binding is stable for both sites, albeit less stable than imipramine. The interaction of these drugs with the helix bundle might alter allostericaly the functionality of the channel. In conclusion, the clinical action of (2)-reboxetine may be produced (at least partially) by its inhibitory action on ha4b2 nAChRs.

Phytochemical of Indonesian Macaranga and their Cytotoxic Properties Against P388 Cells

“…This review focuses on the application of in silico approaches to explain the experimental results on the interaction between a variety of nAChRs subtypes and structurally different antidepressants such as TCAs, NSRIs, and DA/NE reuptake inhibitors, as well as mecamylamine [14,15,28,33]. In this regard, the first step involves the construction of the nAChR target by molecular homology [21,22,28,[31][32][33], using the Torpedo nAChR model (Fig.…”

“…In this regard, the first step involves the construction of the nAChR target by molecular homology [21,22,28,[31][32][33], using the Torpedo nAChR model (Fig. 1) as a structural template.…”

“…1) as a structural template. The antidepressants under study were built in the protonated and neutral state, and subsequently docked in the nAChR model [21,22,28,[31][32][33]. Finally, to verify whether the ligand orientation is stable within each binding site, molecular dynamics simulations were performed [28,[31][32][33].…”

“…The Ca 2+ -influx and voltage-clamp results indicate that (-)-reboxetine does not inhibit hα4β2 nAChRs via interaction with the orthosteric sites but by a noncompetitive mechanism and in a dose-response manner [28] ( Table 2). Based on the radioligand displacement experiments, we can infer that although (-)-reboxetine interacts with the [ 3 H] imipramine binding site with relatively low affinity, it discriminates between the resting and desensitized states ( Table 3).…”

“…Based on the radioligand displacement experiments, we can infer that although (-)-reboxetine interacts with the [ 3 H] imipramine binding site with relatively low affinity, it discriminates between the resting and desensitized states ( Table 3). The fact that the calculated n H values are close to unity (Table 3) indicates that (-)-reboxetine inhibits [ 3 H]imipramine binding in a noncooperative manner, suggesting that these ligands bind to overlapping sites [28]. In this regard, molecular docking techniques were applied to determine the (-)-reboxetine binding mode at the hα4β2 nAChR.…”