Structure-based discovery of prescription drugs that interact with the norepinephrine transporter, NET

Department of Bioengineering and Therapeutic Sciences, and California Institute for Quantitative Biosciences, University of California, San Francisco, CA 94158, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 09/2011; 108(38):15810-5. DOI: 10.1073/pnas.1106030108
Source: PubMed


The norepinephrine transporter (NET) transports norepinephrine from the synapse into presynaptic neurons, where norepinephrine regulates signaling pathways associated with cardiovascular effects and behavioral traits via binding to various receptors (e.g., β2-adrenergic receptor). NET is a known target for a variety of prescription drugs, including antidepressants and psychostimulants, and may mediate off-target effects of other prescription drugs. Here, we identify prescription drugs that bind NET, using virtual ligand screening followed by experimental validation of predicted ligands. We began by constructing a comparative structural model of NET based on its alignment to the atomic structure of a prokaryotic NET homolog, the leucine transporter LeuT. The modeled binding site was validated by confirming that known NET ligands can be docked favorably compared to nonbinding molecules. We then computationally screened 6,436 drugs from the Kyoto Encyclopedia of Genes and Genomes (KEGG DRUG) against the NET model. Ten of the 18 high-scoring drugs tested experimentally were found to be NET inhibitors; five of these were chemically novel ligands of NET. These results may rationalize the efficacy of several sympathetic (tuaminoheptane) and antidepressant (tranylcypromine) drugs, as well as side effects of diabetes (phenformin) and Alzheimer's (talsaclidine) drugs. The observations highlight the utility of virtual screening against a comparative model, even when the target shares less than 30% sequence identity with its template structure and no known ligands in the primary binding site.

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    • "NE undergoing nonneuronal uptake is metabolized to O-methylated derivatives by catechol-O-methyltransferase (COMT). substances as cocaine and amphetamines (Iversen, 2000; Kristensen et al., 2011; Schlessingera et al., 2011). "
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    ABSTRACT: Neuronal norepinephrine (NE) uptake is a crucial step in noradrenergic neurotransmission that regulates NE concentration in the synaptic cleft. It is a key mechanism mediated by the NE transporter (NET) which takes the neurotransmitter into the presynaptic neuron terminal or the adrenal medulla chromaffin cell. The activity of NET is short and long terms modulated by phosphorylation mediated by protein kinases A, C, and G and calcium-calmodulin-dependent protein kinase, whereas the transporter availability at the cell surface is regulated by glycosylation. Several neuropeptides like angiotensins II, III, and 1-7, bradykinin, natriuretic peptides, as well as endothelins (ETs) regulate a wide variety of biological effects, including noradrenergic transmission and in particular neuronal NE uptake. Diverse reports, including studies from our laboratory, show that ETs differentially modulate the activity and expression of NET not only in normal conditions but also in diverse cardiovascular diseases such as congestive heart failure and hypertension. Current literature supports a key role for the interaction between ETs and NE in maintaining neurotransmission homeostasis and further suggests that this interaction may represent a potential therapeutic target for various diseases, particularly hypertension. © 2015 Elsevier Inc. All rights reserved.
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    • "Consequently, the correlation between the docking score obtained for the best poses with experimentally determined binding free energies is usually poor. Nevertheless, in a recent study, Schlessinger et al. used a homology model of a norepinephrine transporter and molecular docking to successfully predict the prescription drugs which specifically bind to it [173]. With the availability of data from chemical genomics and high-throughput screening [28], [174], the combination of multiple flexible docking tools with chemoinformatics may boost the performance of structure-based virtual screening [175]. "
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    • "Among the 3 drugs examined, it was found that NB cells uptake MIBG via a receptor-mediated process due to the expression of NET on their surface. Phenformin may use a similar mechanism as MIBG since it has been shown to bind NET (18). Phenformin can also easily diffuse into the cells due to the presence of the phenol ring. "
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