SARS-CoV-2 E and 3a proteins are inducers of pannexin currents

Barbara Oliveira Mendes (1) , Malak Alameh (1, 2) , Beatrice Ollivier (1) , Jerome Montnach (1) , Nicolas Bidere (3, 4) , Frederique Souaze (4) , Nicolas Escriou (5) , Flavien Charpentier (1) , Isabelle Baro (1) , Michel de Waard (1, 2) , Gildas Loussouarn (1)

1 ITX-lab - ITX-lab unité de recherche de l'institut du thorax UMR1087 UMR6291
2 LabEx Ion Channels Science and Therapeutics [France]
3 CRCI2NA / Eq 6 - Signaling in Oncogenesis, Angiogenesis and Permeability - SOAP
4 CRCI2NA - Centre de Recherche en Cancérologie et Immunologie Intégrée Nantes-Angers
5 Département de Santé Globale - Department Global Health

Controversial reports have suggested that SARS-CoV E and 3a proteins may be viroporins that conduct currents through the plasma membrane of the infected cells. If true, these proteins would represent accessible targets for the development of new antiviral drugs by using high-throughput patch-clamp techniques. Here we aimed at better characterizing the cell responses induced by E or 3a protein with a particular focus on the ion conductances measured at the cell surface. First, we show that expression of SARS-CoV-2 E or 3a protein in CHO cells gives rise to cells with newly-acquired round shape, tending to detach from the Petri dish. This suggests that cell death is induced upon expression of E or 3a protein. We confirmed this hypothesis by using flow cytometry, in agreement with earlier reports on other cell types. In adhering cells expressing E or 3a protein, whole-cell currents were in fact not different from the control condition indicating that E and 3a proteins are not plasma membrane viroporins. In contrast, recording currents on detached cells uncovered outwardly-rectifying currents, much larger than those observed in control. The current characteristics are reminiscent of what was previously observed in cells expressing SARS-CoV-1 E or 3a proteins. Herein, we illustrate for the first time that carbenoxolone blocks these outward currents suggesting that they are conducted by pannexin channels, mostly likely activated by cell morphology change and/or cell death. Alongside we also demonstrate that truncation of the C-terminal PDZ binding motifs reduces the proportion of dying cells but does not prevent pannexin currents suggesting distinct pathways for cell death and pannexin currents induced by E and 3a proteins. We conclude that SARS-CoV-2 E and 3a proteins are not acting as viroporins expressed at the plasma membrane.

Domaines: Maladies infectieuses; Biophysique

Barbara Oliveira Mendes, Malak Alameh, Beatrice Ollivier, Jerome Montnach, Nicolas Bidere, et al.. SARS-CoV-2 E and 3a proteins are inducers of pannexin currents. 2022. ⟨hal-03823805⟩