Dbnl and β-catenin promote pro-N-cadherin processing to maintain apico-basal polarity.

The neural tube forms when neural stem cells arrange into a pseudostratified, single-cell-layered epithelium, with a marked apico-basal polarity, and in which adherens junctions (AJs) concentrate in the subapical domain. We previously reported that sustained β-catenin expression promotes the formation of enlarged apical complexes (ACs), enhancing apico-basal polarity, although the mechanism through which this occurs remained unclear. Here, we show that β-catenin interacts with phosphorylated pro-N-cadherin early in its transit through the Golgi apparatus, promoting propeptide excision and the final maturation of N-cadherin. We describe a new β-catenin-dependent interaction of N-cadherin with Drebrin-like (Dbnl), an actin-binding protein that is involved in anterograde Golgi trafficking of proteins. Notably, Dbnl knockdown led to pro-N-cadherin accumulation and limited AJ formation. In brief, we demonstrate that Dbnl and Drebrin-like β-catenin assist in the maturation of pro-N-cadherin, which is critical for AJ formation and for the recruitment AC components like aPKC and, consequently, for the maintenance of apico-basal polarity.