Heart ischemia results in connexin43 ubiquitination localized at the intercalated discs

Efficient electric activation and action potential propagation in the heart largely depends on gap junction (GJ) channels, formed by connexins (Cx) localized at the intercalated discs (IDs). Therefore, fine-tuning and maintenance of GJ in cardiomyocytes is essential for normal heart function. Several mechanisms have been implicated in the regulation of the amount of Cx43 at the plasma membrane. Results from our lab demonstrated that Nedd4-mediated ubiquitination of Cx43 signals internalization and degradation of GJ. However, the pathophysiological relevance of this mechanism has never been addressed before. The main objective of this study was to evaluate the involvement of ubiquitination on GJ remodeling, in the ischemic heart. To address this, we used the rat heart Langendorff model and evaluated the ubiquitination profile of Cx43 and its interaction with Nedd4, after 30 min of no-flow ischemia. By confocal microscopy, we show that ischemia induces extensive co-localization of ubiquitin and Nedd4 with Cx43 localized at IDs. Moreover, by subcellular fractionation and co-immunoprecipitation assays, we demonstrate an increased interaction with Nedd4 and ubiquitination of Cx43 localized at IDs. Altogether, these results suggest that ubiquitin is involved in the remodeling of GJ during myocardial ischemia, which requires the recruitment of Nedd4.