Lack of coupling between membrane stretching and pannexin-1 hemichannels

Abstract

We investigated whether pannexin-1, a carbenoxolone-sensitive hemichannel activated in erythrocytes by swelling, could be activated by swelling stress and contribute to swelling-activated chloride currents ( I Cl,swell) in HEK-293 cells. We used ethidium bromide uptake as an index of pannexin-1 activation and I C,swell activation as an index of plasma membrane stretching. I Cl,swell activated by a hypotonic solution was reversible inhibited by carbenoxolone (IC 50 98 ± 5 μM). However, the hypotonic solution that activated I Cl,swell did not induce ethidium bromide uptake indicating that pannexin-1 was not activated by cell swelling. The mimetic peptide 10panx1, a pannexin-1 antagonist, did not affect I Cl,swell activation but completely inhibited the ATP-induced ethidium bromide uptake coupled to P2X 7 receptors activation. We conclude that carbenoxolone directly inhibited I Cl,swell independent of pannexin-1 and that pannexin-1 hemichannels are not activated by swelling in HEK-293 cells.