title: Connexin mimetic peptides inhibit Cx43 hemichannel opening triggered by voltage and intracellular Ca2+ elevation.
abstract: 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.
authors.affiliation: Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Belgium.
authors.forename: Nan
authors.initials: N
authors.lastname: Wang
authors.forename: Marijke
authors.initials: M
authors.lastname: De Bock
authors.forename: Gudrun
authors.initials: G
authors.lastname: Antoons
authors.forename: Ashish K
authors.initials: AK
authors.lastname: Gadicherla
authors.forename: Mélissa
authors.initials: M
authors.lastname: Bol
authors.forename: Elke
authors.initials: E
authors.lastname: Decrock
authors.forename: William Howard
authors.initials: WH
authors.lastname: Evans
authors.forename: Karin R
authors.initials: KR
authors.lastname: Sipido
authors.forename: Feliksas F
authors.initials: FF
authors.lastname: Bukauskas
authors.forename: Luc
authors.initials: L
authors.lastname: Leybaert
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018031:Connexin 43 / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010455:Peptides; D013552:Swine
chemical_list: D018031:Connexin 43; C500216:GJA1 protein, human; C514423:Gap 26 peptide; D007473:Ion Channels; D010455:Peptides; D002118:Calcium