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Quantitative assessment of oligomeric amyloid ? peptide binding to ?7 nicotinic receptor.

ABSTRACT: BACKGROUND AND PURPOSE:Progressive dysfunction of cholinergic transmission is a well-known characteristic of Alzheimer's disease (AD). Amyloid ? (A?) peptide oligomers are known to play a central role in AD and are suggested to impair the function of the cholinergic nicotinic ACh receptor ?7 (?7nAChR). However, the mechanism underlying the effect of A? on ?7nAChR function is not fully understood, limiting the therapeutic exploration of this observation in AD. Here, we aimed to detect and characterize A? binding to ?7nAChR, including the possibility of interfering with this interaction for therapeutic purposes. EXPERIMENTAL APPROACH:We developed a specific and quantitative time-resolved FRET (TR-FRET)-based binding assay for A? to ?7nAChR and pharmacologically characterized this interaction. KEY RESULTS:We demonstrated specific and high-affinity (low nanomolar) binding of A? to the orthosteric binding site of ?7nAChR. A? binding was prevented and reversed by the well-characterized orthosteric ligands of ?7nAChR (epibatidine, ?-bungarotoxin, methylylcaconitine, PNU-282987, S24795, and EVP6124) and by the type II positive allosteric modulator (PAM) PNU-120596 but not by the type I PAM NS1738. CONCLUSIONS AND IMPLICATIONS:Our TR-FRET A? binding assay demonstrates for the first time the specific binding of A? to ?7nAChR, which will be a crucial tool for the development, testing, and selection of a novel generation of AD drug candidates targeting A?/?7nAChR complexes with high specificity and fewer side effects compared to currently approved ?7nAChR drugs. LINKED ARTICLES:This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc.

SUBMITTER: Cecon E

PROVIDER: S-EPMC6715828 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Quantitative assessment of oligomeric amyloid β peptide binding to α7 nicotinic receptor.

Cecon Erika E Dam Julie J Luka Marine M Gautier Clément C Chollet Anne-Marie AM Delagrange Philippe P Danober Laurence L Jockers Ralf R

British journal of pharmacology 20190520 18

<h4>Background and purpose</h4>Progressive dysfunction of cholinergic transmission is a well-known characteristic of Alzheimer's disease (AD). Amyloid β (Aβ) peptide oligomers are known to play a central role in AD and are suggested to impair the function of the cholinergic nicotinic ACh receptor α7 (α7nAChR). However, the mechanism underlying the effect of Aβ on α7nAChR function is not fully understood, limiting the therapeutic exploration of this observation in AD. Here, we aimed to detect and ...[more]

PMID: 30981214

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Project description:Amyloid ? peptide (A?) is a key player in the development of Alzheimer's disease (AD). It is the primary component of senile plaques in AD patients and is also found in soluble forms. Cholinergic activity mediated by ?7 nicotinic receptors has been shown to be affected by A? soluble forms. To shed light into the molecular mechanism of this effect, we explored the direct actions of oligomeric A?1-40 and A?1-42 on human ?7 by fluorescence spectroscopy and single-channel recordings. Fluorescence measurements using the conformational sensitive probe crystal violet (CrV) revealed that in the presence of A? ?7 undergoes concentration-dependent conformational changes. Exposure of ?7 to 100 pM A? changes CrV KD towards that of the desensitized state. However, ?7 is still reactive to high carbamylcholine (Carb) concentrations. These observations are compatible with the induction of active/desensitized states as well as of a novel conformational state in the presence of both A? and Carb. At 100 nM A?, ?7 adopts a resting-state-like structure which does not respond to Carb, suggesting stabilization of ?7 in a blocked state. In real time, we found that A? is capable of eliciting ?7 channel activity either in the absence or presence of the positive allosteric modulator (PAM) PNU-120596. Activation by A? is favored at picomolar or low nanomolar concentrations and is not detected at micromolar concentrations. At high A? concentrations, the mean duration of activation episodes elicited by ACh in the presence of PNU-120596 is significantly reduced, an effect compatible with slow open-channel block. We conclude that A? directly affects ?7 function by acting as an agonist and a negative modulator. Whereas the capability of low concentrations of A? to activate ?7 could be beneficial, the reduced ?7 activity in the presence of higher A? concentrations or its long exposure may contribute to the cholinergic signaling deficit and may be involved in the initiation and development of AD.

Dataset Information

Quantitative assessment of oligomeric amyloid ? peptide binding to ?7 nicotinic receptor.

Publications

Quantitative assessment of oligomeric amyloid β peptide binding to α7 nicotinic receptor.

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