Abstract
E-cadherin-catenin complexes mediate cell-cell adhesion on the basolateral membrane of epithelial cells. The cytoplasmic tail of E-cadherin supports multiple protein interactions, including binding of beta-catenin at the C terminus and of p120ctn to the juxtamembrane domain. The temporal assembly and polarized trafficking of the complex or its individual components to the basolateral membrane are not fully understood. In Madin-Darby canine kidney cells at steady state and after treatment with cycloheximide or temperature blocks, E-cadherin and beta-catenin localized to the Golgi complex, but p120ctn was found only at the basolateral plasma membrane. We previously identified a dileucine sorting motif (Leu586-Leu587, termed S1) in the juxtamembrane domain of E-cadherin and now show that it is required to target full-length E-cadherin to the basolateral membrane. Removal of S1 resulted in missorting of E-cadherin mutants (EcadDeltaS1) to the apical membrane; beta-catenin was simultaneously missorted and appeared at the apical membrane. p120ctn was not mistargeted with EcadDeltaS1, but could be recruited to the E-cadherin-catenin complex only at the basolateral membrane. These findings help define the temporal assembly and sorting of the E-cadherin-catenin complex and show that membrane recruitment of p120ctn in polarized cells is contextual and confined to the basolateral membrane.
Highlights
Classical cadherins are part of a family of cell-surface glycoproteins that mediate cell-cell adhesion in most solid tissues of the mammalian body [1, 2]
⌭-cadherin-green fluorescent protein (GFP) and -Catenin, but Not p120ctn, Are Found on Intracellular Membranes—In MDCK cells, transiently expressed GFP-tagged E-cadherin (Ecad-GFP) [21] produced the same staining pattern as endogenous E-cadherin; it was found predominantly at the basolateral membrane, and newly synthesized Ecad-GFP was seen in a perinuclear Golgi compartment (Fig. 2A)
Costaining of -catenin with Ecad-GFP occurred at the level of the Golgi complex, consistent with previous studies showing that -catenin associates with E-cadherin early in the biosynthetic pathway [19]
Summary
Classical cadherins are part of a family of cell-surface glycoproteins that mediate cell-cell adhesion in most solid tissues of the mammalian body [1, 2]. ⌭-cadherin-GFP and -Catenin, but Not p120ctn, Are Found on Intracellular Membranes—In MDCK cells, transiently expressed GFP-tagged E-cadherin (Ecad-GFP) [21] produced the same staining pattern as endogenous E-cadherin; it was found predominantly at the basolateral membrane, and newly synthesized Ecad-GFP was seen in a perinuclear Golgi compartment (Fig. 2A). Both endogenous -catenin and p120ctn co-localized with Ecad-GFP at the basolateral cell surface (Fig. 2A).
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