Connexin43 phosphorylation and cytoprotection in the heart.
ABSTRACT The fundamental role played by connexins including connexin43 (Cx43) in forming intercellular communication channels (gap junctions), ensuring electrical and metabolic coupling between cells, has long been recognized and extensively investigated. There is also increasing recognition that Cx43, and other connexins, have additional roles, such as the ability to regulate cell proliferation, migration, and cytoprotection. Multiple phosphorylation sites, targets of different signaling pathways, are present at the regulatory, C-terminal domain of Cx43, and contribute to constitutive as well as transient phosphorylation Cx43 patterns, responding to ever-changing environmental stimuli and corresponding cellular needs. The present paper will focus on Cx43 in the heart, and provide an overview of the emerging recognition of a relationship between Cx43, its phosphorylation pattern, and development of resistance to injury. We will also review our recent work regarding the role of an enhanced phosphorylation state of Cx43 in cardioprotection. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
SourceAvailable from: Ajaz Ahmad Waza[Show abstract] [Hide abstract]
ABSTRACT: We have recently shown that adenosine-triphosphate-sensitive potassium [K(+)(ATP)] channel protein subunit, Kir6.1 is a phosphospecific interaction partner of the gap-junction protein connexin43 (Cx43). Since, both Cx43 and K(+)(ATP) are known to be involved in cell survial during hypoxia, we addressed the question, whether the interaction between Cx43 and K(+)(ATP) has a role in protecting cell against hypoxia-induced cell death. We report here that the Kir6.1 protein interacts, in a phosphospecific manner with Cx43 in the mitochondria of cardiomyocytic cell line H9C2. The hypoxia for 12-hours resulted in the appreciable increase in the phosphorylation at the serine 262 (S262) of the Cx43 with the concomitant increase in the Cx43 and Kir6.1 interaction. Moreover, the increased interaction was mediated by a signalling pathway involving PKC and more specifically by PKC epsilon. Functional implications of the association between the Cx43 and Kir6.1 was found to prevent mitochondria mediated hypoxia induced cell apoptosis. Our results demonstrate that PKC epsilon regulate the interaction between Cx43 and Kir6.1 in the cardiomyocyte mitochondria and this interaction prevents hypoxia induced cell death. Our results provide an interesting lead in developing effective strategies to protect cardiomyocytes from hypoxia/ischemia induced cell death.Cellular Signalling 05/2014; DOI:10.1016/j.cellsig.2014.05.002 · 4.47 Impact Factor
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ABSTRACT: Fibroblast growth factor-2 (FGF-2) protects the heart from ischemia and reperfusion- induced cell death by a mechanism linked to protein kinase C (PKC)ε-mediated connexin43 (Cx43) phosphorylation. Cx43 localizes predominantly to gap junctions but has also been detected at subsarcolemmal (SSM), but not interfibrillar (IFM), mitochondria, where it is considered important for cardioprotection. We have now examined the effect of FGF-2 administration to the heart on resistance to calcium-induced permeability transition (mPTP) of isolated SSM versus IFM suspensions, in relation to mitochondrial PKCε/Cx43 levels, phosphorylation, and presence of peptide Gap27, a Cx43 channel blocker.Methods and ResultsFGF-2 perfusion increased resistance to calcium-induced mPTP in SSM and IFM suspensions by 2.9- and 1.7-fold, respectively, compared to their counterparts from vehicle-perfused hearts, assessed spectrophotometrically as cyclosporine A-inhibitable swelling. The salutary effect of FGF-2 was lost in SSM but not IFM in the presence of Gap27. FGF-2 perfusion increased relative levels of PKCε, phospho(p) PKCε and Tom-20 translocase in SSM and IFM, and of Cx43 in SSM. Phospho-serine (pS) 262-, and pS368- Cx43 showed a 30-fold and 8-fold increase, respectively, in SSM from FGF-2-treated, compared to untreated, hearts. Stimulation of control SSM with phorbol 12-myristate 13-acetate (PMA), a PKC activator, increased both calcium tolerance and mitochondrial Cx43 phosphorylation at S262 and S368. The PMA-induced phosphorylation of mitochondrial Cx43 was prevented by εV1-2, a PKCε-inhibiting peptide. SSM are more responsive than IFM to FGF-2-triggered protection from calcium-induced mPTP, by a mitochondrial Cx43-channel-mediated pathway, associated with mitochondrial Cx43 phosphorylation at PKCε-target sites.Cardiovascular Research 03/2014; DOI:10.1093/cvr/cvu066 · 5.81 Impact Factor
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ABSTRACT: Background Remote ischemic preconditioning (RIPC) protects the heart from ischemia and reperfusion (I/R) injury. The underlying molecular mechanisms are unclear. It has been demonstrated that Connexin 43 (Cx43) is critically involved in cardioprotective interventions including classical ischemic preconditioning. In the present study we investigated the influence of RIPC on the expression patterns of Cx43 after I/R in the rat heart in vivo.Methods Male Wistar rats were subjected to 35 min regional myocardial ischemia followed by 2 h reperfusion with or without 4 cycles of 5 minutes bilateral hind limb ischemia and reperfusion (RIPC), to RIPC without ischemia or underwent no intervention (Sham). Infarct size was measured by TTC staining. The myocardium was divided into area at risk (AAR) and area not at risk (non AAR). Expression of Cx43-mRNA and protein was analyzed by qPCR and Western Blot analysis, respectively. Localization of Cx43 was visualized by confocal immunofluorescence staining.ResultsRIPC reduced the infarct size (I/R: 73¿±¿5% vs.Journal of Translational Medicine 08/2014; 12(1):228. DOI:10.1186/s12967-014-0228-8 · 3.99 Impact Factor