Characterization of the interaction between β-catenin and sorting nexin 27: contribution of the type I PDZ-binding motif to Wnt signaling

Abstract

Background: 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 common among all of the sorting nexin family, 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. Furthermore, E-cadherin, but not Axin, GSK3 or Lef-1 was located in SNX27 protein complexes. While overexpression of wild-type β-catenin protein increased TCF-LEF dependent transcriptional activity, an enhanced transcriptional activity was not observed in cells expressing β-Catenin ΔFDTDL or diminished SNX27 expression.These results imply importance of the C-terminal PDZ binding motif for the transcriptional activity of β-catenin and propose that SNX27 might be involved in the assembly of β-catenin complexes in the endosome.

Expression and subcellular localization of USH1C/harmonin in the human retina provide insights into pathomechanisms and therapy

“…Furthermore, yeast two-hybrid assays demonstrated the direct interactions of β-catenin, JAM-B, and filamin A with harmonin (data not shown). β-catenin presumably bind to the PDZ1 and PDZ3 domains of harmonin via a C -terminal type-I PDZ binding motif (DTDL) (DuChez et al, 2019). In contrast, JAM-B contains a canonical type II PDZ targeting motif (FLV) at position 298-300 of its C -terminus, which is likely responsible for binding to harmonin (Ebnet et al, 2003).…”

Sorting Out Sorting Nexins Functions in the Nervous System in Health and Disease

“…Of notice, Snx27 was identified as an alternative-splicing product of Mrt1 (methamphetamine responsive transcript 1) gene that was developmentally regulated and drug-inducible [141]. More recently, a study highlighted how SNX27 interaction with β-catenin, through its PDZ domain, can possibly shape Wnt signaling and, hence, embryonic developmental processes [164]. Furthermore, SNX27 associates with epilepsy [146] and patients with SNX27 variants display seizures, developmental delay, behavioral disturbance, and subcortical brain abnormalities [152].…”

The Usher syndrome 1C protein harmonin regulates canonical Wnt signaling

“…We show this with the present interaction assays in mammalian cells and in situ by PLAs, confirming previous in vitro data ( Johnston et al, 2004 ; Nagel-Wolfrum et al, 2022 ). The binary interaction of harmonin and β -catenin is mediated by binding of the C-terminal tail of β -catenin with its type I PBM (DTDL) ( DuChez et al, 2019 ) to PDZ domains 1 and 3 on harmonin, with a slight preference for PDZ3 ( Nagel-Wolfrum et al, 2022 ). Binding of the C-terminal PBM of β -catenin to PDZ domains has been previously described for interactions with other PDZ domain-containing proteins such as MAGI-1 and LIN7 ( Dobrosotskaya and James, 2000 ; Perego et al, 2000 ).…”

“…However, recent studies have further indicated that PBM-mediated interactions of β -catenin are also essential for its role as a coactivator in the cWnt pathway ( DuChez et al, 2019 ). The interaction of the small PDZ protein EBP50 with the PBM of β -catenin potentiates its transcriptional activity in liver cancer cells ( Shibata et al, 2003 ).…”