Channel Behavior and Voltage Gating of a Cx43 Mutant Simulating Preconditioning

Background: Ischemic preconditioning induces lateralization and dephosphorylation of Connexin 43 (Cx43). However, the Cx43 protein that remains at intercalated disks may be phosphorylated by casein kinase 1 (CK1) and protein kinase C (PKC), and both kinases provide cardioprotection from further ischemic injury. Here we explore the channel characteristics of a Cx43 mutant mimicking preconditioning by CK1 and PKC phosphorylation. Materials and Methods: Whole-cell patch-clamp recordings were performed in cells expressing the mutant Cx43pc (S325,328,330,368D, S365A-Cx43), and the connexin electrical behavior was analyzed at the single channel and macroscopic level. Results: Cx43pc hemichannels opened readily, whereas gap junctions channels displayed amplitudes between the wild-type and CK1 phosphorylated forms, and weaker voltage gating than either counterpart. Conclusions: Ischemic preconditioning and the ensuing phosphorylation of Cx43 by PKC may render junctional channels insensitive to transjunctional voltages, allowing the preservation of intercellular communication in ischemic conditions.