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Bupropion and its photoreactive analog (±)-SADU-3-72 interact with luminal and non-luminal sites at human α4β2 nicotinic acetylcholine receptors

Arias, HR and Feuerbach, Dominik and Ortello, M (2012) Bupropion and its photoreactive analog (±)-SADU-3-72 interact with luminal and non-luminal sites at human α4β2 nicotinic acetylcholine receptors. Biomembranes.

Abstract

ABSTRACT
The interaction of (±)-bupropion [(±)-BP] with the human (h) α4β2 nicotinic acetylcholine receptor (AChR) was compared to that for its photoreactive analog (±)-2-(N-tert-butylamino)-3’-iodo-4’-azidopropiophenone [(±)-SADU-3-72]. Ca2+ influx results indicated that (±)-SADU-3-72 and (±)-BP inhibit hα4β2 AChRs with practically the same potency. However, (±)-SADU-3-72 binds to the [3H]imipramine sites at resting and desensitized hα4β2 AChRs with 3-fold higher affinity compared to that for (±)-BP, which is supported by molecular docking results. The docking results also indicate that each isomer of BP and SADU-3-72, in the protonated state, interacts with luminal and non-luminal sites. In the channel lumen, both ligands bind to two overlapping subsites, one that overlaps the imipramine site, and another much closer to the cytoplasmic side. Regarding the non-luminal sites, there are three differentiated domains, including the transmembrane (TMD), extracellular (ECD), and ECD-TMD junctional domains. In the ECD-TMD junction, BP and SADU-3-72 bind to overlapping sites. Interestingly, only SADU-3-72 binds to intrasubunit and intersubunit sites in the TMD, and to additional sites in the ECD. Our results are consistent with a model where BP and SADU-3-72 bind to overlapping sites in the luminal and ECD-TMD junctional domains of the hα4β2, whereas only SADU-3-72 binds to additional non-luminal sites. Based on these results, (±)-SADU-3-72 is a promising photoreactive probe for mapping the BP binding sites in the hα4β2 AChR ion channel in particular, as well as to study non-luminal sites for noncompetitive antagonists in general.

Item Type: Article
Date Deposited: 10 May 2016 23:45
Last Modified: 10 May 2016 23:45
URI: https://oak.novartis.com/id/eprint/28598

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