General structures and subcellular distribution of catenin-uncoupled tailless cadherin mutants. (A) Schematic representation of the tailless EcDendra-Δ748-KL mutant. The extracellular cadherin-like repeats (1–5); the transmembrane domain (TM); the short, 17-aa-long fragment that is located between the transmembrane and the p120-binding domains in the intact E-cadherin (yellow box); and the Dendra tag (Dendra) are shown. To stabilize the mutant on the cell surface, two endocytic signals (K738 and LL motif) that are present in the remaining intracellular fragment are point inactivated (not depicted). Point mutations used in our study and their effects on cadherin dimerization are indicated (see also Table S1). (B) Double immunofluorescence microscopy of A-431 cells expressing EcDendra-Δ748-KL. The cells were stained with rabbit anti-Dendra (Dendra) and mouse anti–β-catenin (β-catenin) antibodies. Note the precise colocalization of the mutant to the endogenous cadherin–catenin complex. (C) The same experiment as in B with A-431 cells expressing EcDendra-Δ748-KL mutants harboring different point mutations (shown in A). Note that mutations that change only X or only strand-swap dimerization do not prevent targeting of the mutant to the cell–cell contact and its colocalization with the endogenous cadherin. Only a double mutation (W2A/K14E) inactivating both interactions completely uncouples the mutant from endogenous cadherin. Bar, 40 µM.