Different Interaction between the Agonist JN403 and the Competitive Antagonist Methyllycaconitine with the Human α7 Nicotinic Acetylcholine Receptor

Abstract

The interaction of the agonist JN403 with the human (h) alpha7 nicotinic acetylcholine receptor (AChR) was compared to that for the competitive antagonist methyllycaconitine (MLA). The receptor selectivity of JN403 was studied on the halpha7, halpha3beta4, and halpha4beta2 AChRs. The results established that the cationic center and the hydrophobic group found in JN430 and MLA are important for the interaction with the AChRs. MLA preincubation inhibits JN403-induced Ca(2+) influx in GH3-halpha7 cells with a potency 160-fold higher than that when MLA is co-injected with JN403. The most probable explanation, based on our dynamics results, is that MLA (more specifically the 3-methyl-2,5-dioxopyrrole ring and the B-D rings) stabilizes the resting conformational state. The order of receptor specificity for JN403 is as follows: halpha7 > halpha3beta4 ( approximately 40-fold) > halpha4beta2 ( approximately 500-fold). This specificity is based on a larger number of hydrogen bonds between the carbamate group (another pharmacophore) of JN403 and the halpha7 sites, the electrostatic repulsion between the positively charged residues around the halpha3beta4 sites and the cationic center of JN403, fewer hydrogen bonds for the interaction of JN403 with the halpha3beta4 AChR, and an unfavorable van der Waals interaction between JN403 and the alpha4-beta2 interface. The higher receptor specificity for JN403 could be important for the treatment of alpha7-related disorders, including dementias, pain-related ailments, depression, anxiety, and wound healing.

Covalent Trapping of Methyllycaconitine at the α4-α4 Interface of the α4β2 Nicotinic Acetylcholine Receptor

“…The preincubation was required to observe maximal insurmountable inhibition of the ␣4␤2 nAChR in this study, which suggests a slow onset of MLA binding to the ␣4-␣4 interface. Similar observations have been made for human ␣7 nAChRs where preincubation has been demonstrated to increase the potency of MLA inhibition of JN403-induced currents (43). In our covalent trapping study, the pseudo first order rate constant for binding and reaction of MLA-maleimide (1 M) at the (␣4[D204C]) 2 (␤2) 3 Ϫ1 .…”

Nicotinic Receptors in Neurodegeneration

“…S24795 is a novel α-7 nAChR agonist able to interact with Aß peptide facilitating its release from the α-7 nAChR and restoring the receptor function [156]. JN403 is another novel α-7 potent and partial agonist of human nAChR [157] that inhibits the interaction of Aß peptide with α7 nAChRs and prevents the formation of Aβ/α7 nAChR complexes in vivo [158]. …”

Novel Positive Allosteric Modulators of the Human α7 Nicotinic Acetylcholine Receptor

“…To determine whether compounds 1À4 modulate the binding of a radioligand to the AChR agonist sites, the effect of these compounds on binding of [ 3 H]MLA to hR7 AChRs, on binding of [ 3 H]epibatidine to hR7 and hR3β4 AChRs, and on binding of [ 3 H]cytisine to hR4β2 and Torpedo AChRs was determined as described previously. 19 To determine whether these compounds bind to the AChR ion channel, additional [ R-Bungarotoxin is a competitive antagonist that maintains the AChR in the resting (closed) state. 23 .…”

“…A cutoff of 1.4 Å was used to account for the van der Waals interactions as previously explained. 19 Calculation of the Root-Mean-Square Deviation Values of Compound 2. The conformations of the AChRÀPAM complexes were extracted every 10 ps from the simulation trajectory and superposed with the initial structure by least-squares fitting of the atoms of the protein.…”