E-cadherin binds to desmoglein to facilitate desmosome assembly.

Omer Shafraz,Carien M Niessen,Sanjeevi Sivasankar,Matthias Rübsam,Amber L Caldara,Sara N Stahley,Andrew P Kowalczyk

doi:10.7554/elife.37629

Abstract

Desmosomes are adhesive junctions composed of two desmosomal cadherins: desmocollin (Dsc) and desmoglein (Dsg). Previous studies demonstrate that E-cadherin (Ecad), an adhesive protein that interacts in both trans (between opposing cells) and cis (on the same cell surface) conformations, facilitates desmosome assembly via an unknown mechanism. Here we use structure-function analysis to resolve the mechanistic roles of Ecad in desmosome formation. Using AFM force measurements, we demonstrate that Ecad interacts with isoform 2 of Dsg via a conserved Leu-175 on the Ecad cis binding interface. Super-resolution imaging reveals that Ecad is enriched in nascent desmosomes, supporting a role for Ecad in early desmosome assembly. Finally, confocal imaging demonstrates that desmosome assembly is initiated at sites of Ecad mediated adhesion, and that Ecad-L175 is required for efficient Dsg2 and desmoplakin recruitment to intercellular contacts. We propose that Ecad trans interactions at nascent cell-cell contacts initiate the recruitment of Dsg through direct cis interactions with Ecad which facilitates desmosome assembly.

Highlights

The formation, organization and maintenance of complex tissue structures are mediated by the cadherin superfamily of cell-cell adhesion proteins, a large protein group composed of four major subfamilies: classical cadherins, desmosomal cadherins, protocadherins and atypical cadherins (Brasch et al, 2012)
Identical concentrations of biotinylated cadherins were immobilized on atomic force microscope (AFM) tips and glass coverslip (CS) substrates that were functionalized with polyethylene glycol (PEG) tethers and decorated with streptavidin protein (Figure 1A and B), (Materials and methods), (Lowndes et al, 2014; Manibog et al, 2014; Rakshit et al, 2012; Sivasankar et al, 2009; Zhang et al, 2009)
We show that Ecad and Dsg2 bind via a conserved Leu 175 on the Ecad cis binding interface and form short-lived heterophilic complexes that localize to early desmosomes and efficiently recruit desmosomal proteins to sites of intercellular contact formation

Summary

Introduction

The formation, organization and maintenance of complex tissue structures are mediated by the cadherin superfamily of cell-cell adhesion proteins, a large protein group composed of four major subfamilies: classical cadherins, desmosomal cadherins, protocadherins and atypical cadherins (Brasch et al, 2012). Of these proteins, desmosomal cadherins and classical cadherins are essential for the maintenance of tissue integrity (Rubsam et al, 2017a). Isoforms 1 and 3 are restricted to complex epithelial tissues (Green and Simpson, 2007) and their loss of function leads to epidermal fragility, such as in the autoimmune blistering disease pemphigus (Amagai and Stanley, 2012)

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Conclusion