The Crumbs complex is an important determinant of epithelial apical-basal polarity that functions in regulation of tight junctions, resistance to epithelial-to-mesenchymal transitions and as a tumor suppressor. Although the functional role of the Crumbs complex is being elucidated, its regulation is poorly understood. Here we show that suppression of RNF146, an E3 ubiquitin ligase that recognizes ADP-ribosylated substrates, and Tankyrase, disrupts the junctional Crumbs complex and disturbs the function of tight junctions. We show that RNF146 binds a number of polarity-associated proteins, in particular members of the Angiomotin (AMOT) family. Accordingly, AMOT proteins are ADP-ribosylated by Tankyrase, which drives ubiquitination by RNF146 and subsequent degradation. Ablation of RNF146 or Tankyrase, as well as overexpression of AMOT, relocated PALS1 (a Crumbs complex component) from the apical membrane to internal puncta, a phenotype that is rescued by AMOTL2 knockdown. We thus reveal a novel function of RNF146 and Tankyrase in stabilizing the Crumbs complex via downregulation of AMOT proteins at the apical membrane.
- Received February 24, 2016.
- Accepted July 22, 2016.
- © 2016. Published by The Company of Biologists Ltd