E-cadherin interactome complexity and robustness resolved by quantitative proteomics

E-cadherin-mediated cell-cell adhesion and signaling plays an essential role in development and maintenance of healthy epithelial tissues. Adhesiveness mediated by E-cadherin is conferred by its extracellular cadherin domains and is regulated by an assembly of adaptors and enzymes associated with its cytoplasmic tail. Here, we used proximity biotinylation and quantitative proteomics to identify 561 proteins in the vicinity of E-cadherin’s cytoplasmic tail. Isolation of E-cadherin-mediated adhesion plaques from a cell-glass interface added positional context to the proteomic results. Moreover, using expression of GFP-tagged fusion proteins, we determine the subcellular localization of 83 of the E-cadherin proximal proteins, and identify 24 novel adherens junction components. We employed a structure-informed database of protein-protein interactions to construct a comprehensive E-cadherin interactome, containing 82 known and 419 previously uncharacterized proteins. Finally, we found that calcium chelation did not disrupt most protein interactions with E-cadherin, suggesting that most E-cadherin interactions are independent of cell-cell adhesion.