Characterization of the interaction between Sorting Nexin 27 and β‐Catenin in kidney epithelial cells

Abstract

Sorting Nexin 27 (SNX27) is a 62‐kDa protein localized to early endosomes and known to regulate the intracellular trafficking of ion channels and receptors. In addition to a PX domain, SNX27 is the only sorting family member that contains a PDZ domain. To identify novel SNX27‐PDZ binding partners, we performed a proteomic screen in mouse principal kidney cortical collecting duct cells (mpkCCD) using a GST‐SNX27 fusion construct as bait. We found that the C‐terminal type I PDZ binding motif (DTDL) of β‐Catenin, an adherens junction scaffolding protein and transcriptional co‐activator, interacts directly with SNX27. Using biochemical and immunofluorescent techniques, β‐Catenin was identified in endosomal compartments where co‐localization with SNX27 was observed. As expected, over‐expressed β‐Catenin wild‐type protein was identified in nuclear regions and increased TCF‐LEF dependent transcriptional activity was observed. In contrast, over‐expressed β‐Catenin ΔDTDL was found at sites of cell‐cell contact with transcriptional activity at control levels. These results imply importance of the C‐terminal PDZ binding motif in localization and transcriptional activity of β‐Catenin.