Ion channels activity of SARS-CoV-2 envelope protein through calcium influx assay using large unilamellar vesicles.

Abstract

The envelope (E) protein of the SARS-CoV-2 virus is a membrane-bound viroporin that conducts cations across the endoplasmic reticulum Golgi intermediate compartment (ERGIC) membrane of the host cell to cause virus pathogenicity. Channel opening by acidic pH and Ca2+ increases the population of the dynamic lipid-facing conformation. Here, we developed an assay for the calcium channel activity of SARS-CoV-2 envelope (ETM) protein. The calcium-sensitive fluorescence indicator, frua-2, was incorporated into large unilamellar vesicles (LUVs). After establishing a calcium gradient across the liposomal membranes, native or mutated ETM protein was added. The resulting calcium influx into the LUV detected through the fluorescence changes of fura-2 was used as a qualitative test for the electrophysiological properties of ETM protein.This discovery of ETM protein calcium influx activity may be a target for E inhibitors against SARS-CoV-2 and related coronaviruses.