Potential independent action of sigma receptor ligands through inhibition of the Kv2.1 channel.

Xinying Liu,Christopher R Mccurdy,Jun Li,Huan Yang,Lian-Wang Guo,Bikash R Pattnaik,Timur Mavlyutov,Yingmei Fu

doi:10.18632/oncotarget.19581

Abstract

The sigma-1 receptor (σ1-R) and sigma-2 receptor (σ2-R) are potential drug targets for treatment of cancer, pain, depression, retinal degeneration and other neuronal diseases. Previous reports show that sigma-1 receptor modulates the activities of multiple channels. We are interested in possible sigma receptor modulation of Kv2.1, a K+ channel abundant in retinal photoreceptors. We tested the effect of established sigma receptor ligands on Kv2.1 channels which were stably expressed in HEK293 cells. Surprisingly, σ1-R antagonists inhibited Kv2.1 currents in both wild type and σ1-R knockout HEK293 cells that we engineered using the CRISPR/Cas9 technology. Moreover, PB28, a σ1-R antagonist and also σ2-R agonist, inhibited Kv2.1 in σ1-R knockout cells, but this action was not blocked by the σ2-R antagonists that did not have an effect on Kv2.1. We also observed inhibition of electroretinogram by PB28 in wild type as well as σ1-R knockout mice. Thus, the results in this study indicate that the Kv2.1-inhibiting function of the sigma ligands is not sigma receptor dependent, suggesting a direct effect of these ligands on the Kv2.1 channel.

Highlights

Sigma receptors are classified into the sigma-1 (σ1-R) and sigma-2 receptor (σ2-R) subtypes based on their distinct as well as shared ligand binding characteristics [1]
We tested the effect of established sigma receptor ligands on Kv2.1 channels which were stably expressed in HEK293 cells
Using a human cell line overexpressing Kv2.1 and with σ1R depleted via genome editing, we identified an σ-R-independent Kv2.1-inhibitory function of a defined group of ligands that were previously characterized as σ-R-selective

Summary

Introduction

Sigma receptors are classified into the sigma-1 (σ1-R) and sigma-2 receptor (σ2-R) subtypes based on their distinct as well as shared ligand binding characteristics [1]. A great majority of σ1-R (and all σ2-R) modulations were identified via pharmacology using σ-R agonists and antagonists, many of which are known to bind other targets too [9]. The best known σ1-R function probably is its modulations of voltage-gated Ca2+ [1013], Na+ [14,15,16] and K+ channels [17,18,19], via direct or indirect interactions [20]. Σ1-R inhibits the activity of several K+ channels, including Kv1.2, Kv1.3, and Kv1.4 [18, 19, 21]; its interactions with these proteins were confirmed by co-immunoprecipitation experiments [19, 21] The best known σ1-R function probably is its modulations of voltage-gated Ca2+ [1013], Na+ [14,15,16] and K+ channels [17,18,19], via direct or indirect interactions [20]. σ1-R inhibits the activity of several K+ channels, including Kv1.2, Kv1.3, and Kv1.4 [18, 19, 21]; its interactions with these proteins were confirmed by co-immunoprecipitation experiments [19, 21]

Methods

Findings

Discussion

Conclusion