Desmoglein-2
plasma membrane
The most widespread desmosomal cadherin, desmoglein 2, is a novel target of caspase 3-mediated apoptotic machinery.
Apoptotic cells are known to regulate the ordered dismantling of intercellular contacts through caspase activity. Despite the important role of desmoglein (Dsg) 2 in epithelial cell-cell adhesion, the fate of this widespread desmosomal cadherin during apoptosis is yet poorly understood. Here, by means of pharmacological approaches, we investigated whether Dsg2 was targeted by caspases in HaCaT and HT-29 cell lines undergoing staurosporine (STS)-induced apoptosis. Results showed that STS induced a caspase-dependent form of cell-death in both keratinocytes (HaCaT) and enterocytes (HT-29), that associated with progressive depletion of Dsg2 from cell lysates. The proteolytic processing of full-length Dsg2 resulted in the appearance of a 70-kDa fragment which was released into the cytosol. Consistently, immunofluorescence studies revealed that Dsg2 staining was abolished from cell surface whereas the cytoplasmic region of Dsg2 did localize intracellularly. Plakoglobin (Pg) also underwent cleavage and detached from Dsg2. Apoptotic changes paralleled with progressive loss of intercellular adhesion strength. All these biochemical, morphological, and functional changes were regulated by caspase 3. Indeed, in the presence of the caspase 3-inhibitor z-DEVD-fmk, full-length Dsg2 protein levels were preserved, whereas the amount of the 70-kDa fragment was maintained on control levels. Furthermore, cells pretreated with z-DEVD-fmk retained the membrane labeling of Dsg2. Taken together, our data demonstrate that the apoptotic processing of Dsg2 is mediated by caspase 3 in epithelial cells.