DESMOPLAKIN EXPRESSION AND ORGANIZATION AT HUMAN UMBILICAL VEIN ENDOTHELIAL CELL-TO-CELL JUNCTIONS

Desmoplakin is an intracellular component of desmosomes which plays a role in the anchorage of intermediate filaments to these structures. W e report here that, despite the absence of desmosomes, cultured endoth elial cells from human umbilical vein express desmoplakin I and II bot h at mRNA and protein level, Desmoplakin I/II are found only in the de tergent insoluble fraction suggesting that most of the protein is link ed to the cytoskeleton, Desmoplakin I/II could be detected by western blot only in long confluent cells even if desmoplakin mRNA levels are unchanged by cell confluency. This suggests that desmoplakin might be stabilized at protein level by its association with junctional compone nts, Immunofluorescence confocal microscopy showed that desmoplakin co distributes with VE-cadherin and plakoglobin along the lateral cell me mbrane, In contrast, desmoplakin localization was distinct from that o f PECAM, an endothelial specific junctional protein localized outside adherence junctions, Endothelial cells do not have keratins but they e xpress vimentin, In confluent cells vimentin forms peripheral filament s which attach to the cell membrane in areas at desmoplakin localizati on, These data suggest that desmoplakin may participate in the molecul ar organization of interendothelial junctions by interacting with VE-c adherin and promoting vimentin anchorage, This new type of intercellul ar junction seems to correspond to the 'complexus adhaerentes' describ ed in vivo in lymphatic endothelium.