Association of connexin43 with E3 ubiquitin ligase TRIM21 reveals a mechanism for gap junction phosphodegron control.

Gap junctions (GJs) are sites of direct cell-to-cell communication formed by the connexin (Cx) family of ion channel proteins. The aberrant intercellular communication mediated by GJs is associated with a variety of hereditary and acquired human diseases. GJs utilize a highly interconnected network that is indispensible for synthesis, trafficking and degradation of their constituent proteins. By unbiased proteomic examination and network enrichment, we identified interacting components of the ubiquitin proteasome system associated with Cx43. LC-MS/MS identification and quantification of tryptic peptides from IP materials revealed a variety of interacting candidates, including the E3 ligase TRIM21 and ubiquitin. The interaction of Cx43 with TRIM21 was confirmed by confocal microscopy and coimmunoprecipitation of these proteins from C6 rat glioma and mouse primary astrocyte cultures. To gain a better understanding of this interaction, complexes isolated by high-resolution size-exclusion chromatography revea...