Connexin mimetic peptides inhibit Cx43 hemichannel opening triggered by voltage and intracellular Ca2+ elevation

• DOI: 10.1007/s00395-012-0304-2
• Publication Date: 2012-10-19T22:41:13Z
• Authors: Nan Wang; Marijke De Bock; Gudrun Antoons; Ashish K. Gadicherla; Mélissa Bol; Elke Decrock; William Howard Evans; Karin R. Sipido; Feliksas F. Bukau...; Luc Leybaert
• Keywords: 0301 basic medicine; 0303 health sciences; Patch-Clamp Techniques; Swine; Ion Channels; Membrane Potentials; 03 medical and health sciences; Connexin 43; Animals; Humans; Calcium; Myocytes, Cardiac; Peptides; HeLa Cells

Connexin mimetic peptides (CxMPs), such as Gap26 and Gap27, are known as inhibitors of gap junction channels but evidence is accruing that these peptides also inhibit unapposed/non-junctional hemichannels (HCs) residing in the plasma membrane. We used voltage clamp studies to investigate the effect of Gap26/27 at the single channel level. Such an approach allows unequivocal identification of HC currents by their single channel conductance that is typically ~220 pS for Cx43. In HeLa cells stably transfected with Cx43 (HeLa-Cx43), Gap26/27 peptides inhibited Cx43 HC unitary currents over minutes and increased the voltage threshold for HC opening. By contrast, an elevation of intracellular calcium ([Ca(2+)](i)) to 200-500 nM potentiated the unitary HC current activity and lowered the voltage threshold for HC opening. Interestingly, Gap26/27 inhibited the Ca(2+)-potentiated HC currents and prevented lowering of the voltage threshold for HC opening. Experiments on isolated pig ventricular cardiomyocytes, which display strong endogenous Cx43 expression, demonstrated voltage-activated unitary currents with biophysical properties of Cx43 HCs that were inhibited by small interfering RNA targeting Cx43. As observed in HeLa-Cx43 cells, HC current activity in ventricular cardiomyocytes was potentiated by [Ca(2+)](i) elevation to 500 nM and was inhibited by Gap26/27. Our results indicate that under pathological conditions, when [Ca(2+)](i) is elevated, Cx43 HC opening is promoted in cardiomyocytes and CxMPs counteract this effect.