Characterization of E-cadherin-containing junctions involving skin-deriveddendritic cells

Adherens junctions are sites of contact between epithelial cells in which a dhesion is mediated by hemophilic interactions of classical cadherins that are linked to the cytoskeleton via catenins, E-cadherin constitutes the maj or adhesion molecule in adherens junctions of keratinocytes (KC) and mediat es the binding of Langerhans cells to KC in vitro. To characterize structur es responsible for E-cadherin-mediated binding of Langerhans cells, we util ized Langerhans cells-like fetal skin-derived dendritic cells (FSDDC) capab le of E-cadherin-mediated adhesion. Confocal microscopy of FSDDC aggregates demonstrated colocalization of E-cadherin and catenins to areas of cell-ce ll contact. Immunopreciptiation confirmed a physical association of E-cadhe rin with intracellular catenins (alpha-, beta-, gamma-catenin/plakoglobin a nd p120(CAS)). Transmission electron microscopy of FSDDC aggregates reveale d structures with features of adherens junctions in areas of cell-cell cont act, and post-embedding immunoelectron microscopy localized beta-catenin to these regions. To characterize junctions that accounted for the adhesion o f Langerhans cells-like dendritic cells and KC, disaggregated FSDDC were co cultured with primary murine KC, Transmission electron microscopy analysis of cocultures demonstrated FSDDC-KC contacts that were analogous to those s een in FSDDC aggregates. Confocal microscopy demonstrated focal accumulatio ns of E-cadherin and colocalization of beta-catenin in areas of contact bet ween KC and immature (Langerhans cell-like) dendritic cells, but not in are as of contact between KC and mature (lymph node dendritic cell-like) dendri tic cells. E-cadherin in Langerhans cells appears to be localized in struct ures that resemble adherens junctions formed by nonpolarized epithelial cel ls. Loss of ability to form or maintain these structures after the inductio n of Langerhans cells activation/maturation likely results in the attenuati on of Langerhans cells-KC adhesion that preceeds Langerhans cells emigratio n from the epidermis.