Rap1 acts via multiple mechanisms to position Canoe and adherens junctions and mediate apical-basal polarity establishment

Development. 2018 Jan 26;145(2):dev157941. doi: 10.1242/dev.157941.

Abstract

Epithelial apical-basal polarity drives assembly and function of most animal tissues. Polarity initiation requires cell-cell adherens junction assembly at the apical-basolateral boundary. Defining the mechanisms underlying polarity establishment remains a key issue. Drosophila embryos provide an ideal model, as 6000 polarized cells assemble simultaneously. Current data place the actin-junctional linker Canoe (fly homolog of Afadin) at the top of the polarity hierarchy, where it directs Bazooka/Par3 and adherens junction positioning. Here we define mechanisms regulating Canoe localization/function. Spatial organization of Canoe is multifaceted, involving membrane localization, recruitment to nascent junctions and macromolecular assembly at tricellular junctions. Our data suggest apical activation of the small GTPase Rap1 regulates all three events, but support multiple modes of regulation. The Rap1GEF Dizzy (PDZ-GEF) is crucial for Canoe tricellular junction enrichment but not apical retention. The Rap1-interacting RA domains of Canoe mediate adherens junction and tricellular junction recruitment but are dispensable for membrane localization. Our data also support a role for Canoe multimerization. These multifactorial inputs shape Canoe localization, correct Bazooka and adherens junction positioning, and thus apical-basal polarity. We integrate the existing data into a new polarity establishment model.

Keywords: Cadherin; Canoe/Afadin, Drosophila; Cell adhesion; Epithelia; Morphogenesis; Polarity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adherens Junctions / metabolism
  • Animals
  • Animals, Genetically Modified
  • Cell Polarity / genetics
  • Cell Polarity / physiology*
  • Drosophila Proteins / chemistry
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / embryology*
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / metabolism*
  • Female
  • Gastrulation
  • Gene Knockdown Techniques
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Male
  • Models, Biological
  • Protein Interaction Domains and Motifs
  • Protein Transport
  • RNA Interference
  • Shelterin Complex
  • Telomere-Binding Proteins / chemistry
  • Telomere-Binding Proteins / genetics
  • Telomere-Binding Proteins / metabolism*

Substances

  • Drosophila Proteins
  • Guanine Nucleotide Exchange Factors
  • Intracellular Signaling Peptides and Proteins
  • PDZ-GEF protein, Drosophila
  • RAP1 protein, Drosophila
  • Shelterin Complex
  • Telomere-Binding Proteins
  • baz protein, Drosophila
  • cno protein, Drosophila