Connexin 43 phosphorylation by casein kinase 1 is essential for the cardioprotection by ischemic preconditioning

Abstract

Myocardial connexin 43 (Cx43) forms gap junctions and hemichannels, and is also present within subsarcolemmal mitochondria. The protein is phosphorylated by several kinases including mitogen-activated protein kinase (MAPK), protein kinase C (PKC), and casein kinase 1 (CK1). A reduction in Cx43 content abrogates myocardial infarct size reduction by ischemic preconditioning (IPC). The present study characterizes the contribution of Cx43 phosphorylation towards mitochondrial function, hemichannel activity, and the cardioprotection by IPC in wild-type (WT) mice and in mice in which Cx43-phosphorylation sites targeted by above kinases are mutated to non-phosphorylatable residues (Cx43MAPKmut, Cx43PKCmut, and Cx43CK1mut mice). The amount of Cx43 in the left ventricle and in mitochondria was reduced in all mutant strains compared to WT mice and Cx43 phosphorylation was altered at residues not directly targeted by the mutations. Whereas complex 1 respiration was reduced in all strains, complex 2 respiration was decreased in Cx43CK1mut mice only. In Cx43 epitope-mutated mice, formation of reactive oxygen species and opening of the mitochondrial permeability transition pore were not affected. The hemichannel open probability was reduced in Cx43PKCmut and Cx43CK1mut but not in Cx43MAPKmut cardiomyocytes. Infarct size in isolated saline-perfused hearts after ischemia/reperfusion (45 min/120 min) was comparable between genotypes and was significantly reduced by IPC (3 × 3 min ischemia/5 min reperfusion) in WT, Cx43MAPKmut, and Cx43PKCmut, but not in Cx43CK1mut mice, an effect independent from the amount of Cx43 and the probability of hemichannel opening. Taken together, our study shows that alterations of Cx43 phosphorylation affect specific cellular functions and highlights the importance of Cx43 phosphorylation by CK1 for IPC’s cardioprotection.

Intracellular Redistribution of Left Ventricular Connexin 43 Contributes to the Remodeling of Electrical Properties of the Heart in Insulin-resistant Elderly Rats

“…63 Overall insight to this subject: innovation is needed for the production of connexin-based therapeutics, although there is little information about the use of connexin-based therapeutics in the clinic for the treatment of either arrhythmia or any other heart disease with an enhancement of gap-junctional communication (i.e., improvement of lowered conduction) via treatment with a connexinbased therapeutic. [65][66][67] Overall, we, here, demonstrated that not only reduced levels of pCx43 and Cx43 but also their apparent internalizations and lateralizations may be associated with abnormal ventricular repolarization, which in turn leads to long-QT in the Aged-group under insulin resistance, similar to the MetS-group. In this regard, although the underlying mechanisms of these two syndromes include alterations in electrophysiological properties of cardiomyocytes besides changes in the heart tissues, further studies are needed to clarify the exact mechanism responsible for the existence of these changes under insulin resistance.…”

“…63 Overall insight to this subject: innovation is needed for the production of connexin-based therapeutics, although there is little information about the use of connexin-based therapeutics in the clinic for the treatment of either arrhythmia or any other heart disease with an enhancement of gap-junctional communication (i.e., improvement of lowered conduction) via treatment with a connexin-based therapeutic. 65–67…”

Distinct Effects of Escitalopram and Vortioxetine on Astroglial L-Glutamate Release Associated with Connexin43

“…The other discrepancy between Cx43 expression in the plasma membrane and L-glutamate release through activated astroglial hemichannels suggests the possibility that subchronic 5-HT1AR activation suppresses hemichannel activity. Cx43 has various phosphorylation sites which receive inhibitory and excitatory regulation [ 76 , 77 , 78 ]. Taken together with the hemichannel regulation system associated with phosphorylation, the suppression of ERK phosphorylation induced by the subchronic administration of BP554 suggests that astroglial L-glutamate release through activated hemichannels is probably reduced by the attenuation of hemichannel activity.…”

Heat Shock Protein 90 as Therapeutic Target for CVDs and Heart Ageing

“…Recently, the central role of mitochondrial HSP90 and connexin 43 (Cx43) in IpostC cardioprotection was shown [ 37 ]. Cx43 is the predominant protein forming gap junctions and hemichannels in the ventricular myocardium, thus crucial for intercellular electrical conduction, cardioprotection and cell survival in mammals [ 38 ]. Application of IpostC on rat heart-derived H9c2 cells and neonatal rat cardiomyocytes resulted in increased total and mitochondrial levels of HSP90, the mitochondria-to-sarcolemma ratio of Cx43, increased levels of Bcl-2 and decreased Bax levels in both sarcolemma and mitochondrial fractions [ 37 ].…”