Connexin43 Hemichannel-Mediated Regulation of Connexin43

Abstract

BackgroundMany signaling molecules and pathways that regulate gap junctions (GJs) protein expression and function are, in fact, also controlled by GJs. We, therefore, speculated an existence of the GJ channel-mediated self-regulation of GJs. Using a cell culture model in which nonjunctional connexin43 (Cx43) hemichannels were activated by cadmium (Cd2+), we tested this hypothesis.Principal FindingsIncubation of Cx43-transfected LLC-PK1 cells with Cd2+ led to an increased expression of Cx43. This effect of Cd2+ was tightly associated with JNK activation. Inhibition of JNK abolished the elevation of Cx43. Further analysis revealed that the changes of JNK and Cx43 were controlled by GSH. Supplement of a membrane-permeable GSH analogue GSH ethyl ester or GSH precursor N-acetyl-cystein abrogated the effects of Cd2+ on JNK activation and Cx43 expression. Indeed, Cd2+ induced extracellular release of GSH. Blockade of Cx43 hemichannels with heptanol or Cx43 mimetic peptide Gap26 to prevent the efflux of GSH significantly attenuated the Cx43-elevating effects of Cd2+.ConclusionsCollectively, our results thus indicate that Cd2+-induced upregulation of Cx43 is through activation of nonjunctional Cx43 hemichannels. Our findings thus support the existence of a hemichannel-mediated self-regulation of Cx43 and provide novel insights into the molecular mechanisms of Cx43 expression and function.

Purinergic control of AMPK activation by ATP released through connexin 43 hemichannels: pivotal roles in hemichannel-mediated cell injury

“…Using this model, we confirmed our findings and explored the possible participation of the signaling cascades in Cd 2+ -induced cell injury. Consistent with our previous reports (Fang et al, 2011;Li et al, 2013), Cd 2+ caused release of ATP into the extracellular space in LLC-PK1 cells expressing EGFP-Cx43, which was significantly prevented by the hemichannel blockers heptanol and lindane (Fig. 6A), indicating an involvement of hemichannels.…”

“…Using an atomic force microscope, Muller and colleagues (Müller et al, 2002) observed that low extracellular Ca 2+ increased the outer pore diameter of hemichannels. Consistently, many investigators have found increased hemichannel permeability (Li et al, 2013;Stout et al, 2002). Here, we detected an increased exchange of small molecules across the cell membrane that was disrupted by blockade of Cx43-forming channels, indicating an involvement of hemichannels.…”

“…We have recently reported that Cd 2+ activates Cx43 hemichannels and causes an extracellular accumulation of ATP in LLC-PK1 cells that express EGFP-Cx43 (Fang et al, 2011;Li et al, 2013). Furthermore, we suggested that there is a role for hemichannels in Cd 2+ -induced cell injury (Fang et al, 2011).…”

“…1D-F). These results indicate that Ca 2+ deprivation activates Cx43 hemichannels and induces extracellular release of ATP (Li et al, 2013;Müller et al, 2002;Stout et al, 2002).…”

Suppression of PKCε-mediated mitochondrial connexin 43 phosphorylation at serine 368 is involved in myocardial mitochondrial dysfunction in a rat model of dilated cardiomyopathy

“…Further investigations demonstrated that inactivation of Cx43 eliminated PMA-induced mitochondrial protection. As the cardiomyocytes were cultured sparsely without cell to cell contact, the targeted inactivation of mtCx43 may have led to the suppression of PMA-induced mitochondrial protection (23,24). These results suggested that activation of PKCε may have attenuated mitochondrial dysfunction in a mtCx43-dependent manner.…”