Autophagy modulates dynamics of connexins at the plasma membrane in an ubiquitin- dependent manner

Different pathways contribute to the turnover of connexins, the main structural components of gap junctions (GJ). The cellular pool of connexins targeted to each pathway and the functional consequences of degradation through these degradative pathways remain unknown. In this work, we have focused on the contribution of macroautophagy to connexin degradation. Using pharmacological and genetic blockage of macroautophagy both in vitro and in vivo we have found that the cellular pool targeted by this autophagic system is primarily the one organized into GJ. Interruption of connexins’ macroautophagy resulted in their retention at the plasma membrane in the form of functional GJ and the subsequent increased GJ-mediated intercellular diffusion. Upregulation of macroautophagy alone is not sufficient to induce connexin internalization and degradation. To better understand what factors determine the autophagic degradation of GJ connexins, we analyzed the changes undergone by the fraction of plasma membrane connexin 43 targeted for macroautophagy and the sequence of events that trigger this process. We found that Nedd4-mediated ubiquitinylation of the connexin molecule is required to recruit the adaptor protein Eps15 to the GJ and to initiate the autophagy-dependent internalization and degradation of connexin 43. This study unveils a novel regulatory role for http://www.molbiolcell.org/content/suppl/2012/04/09/mbc.E11-10-0844.DC1.html Supplemental Material can be found at: