A novel binding site in the nicotinic acetylcholine receptor for MB327 can explain its allosteric modulation relevant for organophosphorus-poisoning treatment

Kaiser, Jesko; Gertzen, Christoph G. W.; Bernauer, Tamara; Höfner, Georg; Niessen, Karin V.; Seeger, Thomas; Paintner, Franz F.; Wanner, Klaus T.; Worek, Franz; Thiermann, Horst; Gohlke, Holger

doi:10.1016/j.toxlet.2022.11.018

Cited by 12 publications

(24 citation statements)

References 67 publications

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“…The identified binding area at the ECD/TMD border, is in close proximity to one of the MB327 binding sites identified in the computational simulations with the Torpedo nAChR 58 and human muscle-type nAChR. 16 However, static molecular docking experiments as performed in this study are simplified since BPCs seem to compete as big cations with the small conducting cations, and the conductances and polarizability of the receptor have been neglected. 60 The symmetrical BPCs are derived from bispyridinium oxime reactivators of acetylcholine esterase, such as obidoxim and HI-6.…”

Section: ■ Discussionmentioning

confidence: 78%

“…However, limitations of this open state structure and likely differences to the PNU120596-free open state need to be considered. The identified binding area at the ECD/TMD border, is in close proximity to one of the MB327 binding sites identified in the computational simulations with the Torpedo nAChR and human muscle-type nAChR . However, static molecular docking experiments as performed in this study are simplified since BPCs seem to compete as big cations with the small conducting cations, and the conductances and polarizability of the receptor have been neglected …”

Section: Discussionmentioning

confidence: 82%

“…In the α7 nAChR, BPCs show a weaker voltage-dependency than QX-314 (Figure 3), suggesting that they may localize more toward the α7 ECD and to a deeper binding site in the muscletype. However, based on radioligand binding assays with MB327 on purified T. californica membranes 14 and docking and molecular dynamics simulations on a homology model of the human muscle nAChR, 15,16,58 competitive binding to the orthosteric binding site and allosteric binding sites in the extracellular channel vestibule were proposed for different BPCs. In agreement with a binding site within the α7 TM region, we show that the potency of BPCs and QX-314 is clearly reduced at a α7−5HT3 chimera, in which the α7 TM and ICD domains were replaced with the respective 5HT3 sequences (α7 V201−5HT3A , Figure 4).…”

Section: ■ Discussionmentioning

confidence: 99%

“…15 An allosteric modulation by selected BPCs via a binding site in the extracellular domain (ECD) and competitive binding was recently supported by computational approaches. 16 Studies on a α7 nAChR-expressing CHO cell line showed that BPCs act as positive allosteric modulators (PAMs) and promote nAChR resensitization. 17 However, whether a similar mechanism is possible for muscle-type nAChR is not clear.…”

mentioning

confidence: 99%

“…Later studies found competitive binding at the orthosteric ACh-binding at nAChRs from Torpedo californica, and the involvement of a stabilizing, allosteric binding site was proposed for BPCs with longer linkers . An allosteric modulation by selected BPCs via a binding site in the extracellular domain (ECD) and competitive binding was recently supported by computational approaches . Studies on a α7 nAChR-expressing CHO cell line showed that BPCs act as positive allosteric modulators (PAMs) and promote nAChR resensitization .…”

mentioning

confidence: 99%

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Symmetrical Bispyridinium Compounds Act as Open Channel Blockers of Cation-Selective Ion Channels

Haufe,

Loser,

Danker

et al. 2024

ACS Pharmacol. Transl. Sci.

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Current treatments against organophosphate poisoning (OPP) do not directly address effects mediated by the overstimulation of nicotinic acetylcholine receptors (nAChR). Non-oxime bispyridinium compounds (BPC) promote acetylcholine esterase-independent recovery of organophosphate-induced paralysis. Here, we test the hypothesis that they act by positive modulatory action on nAChRs. Using two-electrode voltage clamp analysis in combination with mutagenesis and molecular docking analysis, the potency and molecular mode of action of a series of nine BPCs was investigated on human α7 and muscle-type nAChRs expressed in Xenopus laevis oocytes. The investigated BPCs inhibited α7 and/or muscle-type nAChRs with IC 50 values in the high nanomolar to high micromolar range. Further analysis of the most potent analogues revealed a noncompetitive, voltagedependent inhibition. Co-application with the α7-selective positive allosteric modulator PNU120596 and generation of α7/5HT3 receptor chimeras excluded direct interaction with the PNU120596 binding site and binding to the extracellular domain of the α7 nAChR, suggesting that they act as open channel blockers (OCBs). Molecular docking supported by mutagenesis localized the BPC binding area in the outer channel vestibule between the extracellular and transmembrane domains. Analysis of BPC action on other cation-selective channels suggests a rather nonspecific inhibition of pentameric cation channels. BPCs have been shown to ameliorate organophosphate-induced paralysis in vitro and in vivo. Our data support molecular action as OCBs at α7 and muscle-type nAChRs and suggest that their positive physiological effects are more complex than anticipated and require further investigation.

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Section: ■ Discussionmentioning

confidence: 78%