Abstract 9561: Connexin43 Interacts with Voltage-Gated Sodium Channel 1.5 in the Perinexus
Rapid depolarization of the myocyte sarcolemma during the cardiac action potential (AP) is dependent on the voltage-gated sodium channel Nav1.5. Gap junctions (GJs) are thought responsible for propagation of AP between myocardial cells. Connexin43 (Cx43) is the primary isoform of GJ subunit in the working ventricular myocardium, where it localizes at intercalated disks. Previous reports from our lab have shown that the interaction of Zonula Occludens-1 (ZO-1) with Cx43 regulates the size of GJ plaques. We have further demonstrated that this interaction regulates GJ size by governing the transition of functioning connexon hemichannels into GJ intercellular channels. Moreover, we have recently determined in epithelial cells that Cx43/ZO-1 interaction extends from the GJ to a region of nonjunctional membrane proximal to the plaque called the perinexus. Here, we examine the hypotheses that cardiac GJs are also surrounded by a perinexus and that this domain contains both connexons and other channels involved in AP generation and propagation. Using the Duolink in situ protein-protein interaction assay it is confirmed that cardiomyocytes also display perinexal Cx43/ZO-1 interactions. It is also demonstrated by analysis of connexin-connexin interaction in situ that the cardiac perinexus exhibits a high density of connexon hemichannels composed of Cx43. In a further novel result, we find that the perinexus contains Nav1.5 complexed with Cx43, but not ZO-1. Additionally, preliminary data indicates that CT-1, an inhibitor of Cx43/ZO-1 binding, increases interaction between Nav1.5 and Cx43 in the perinexus. Taken together, our data confirm that cardiomyocyte GJs exhibit a perinexus. The localization of Nav1.5 in the perinexus suggests that this ephapse-like domain of close sarcolemmal apposition between myocytes has assignments in AP propagation independent of the canonical electrotonic pathway.
- © 2011 by American Heart Association, Inc.