The most widespread desmosomal cadherin, desmoglein 2, is a novel target of caspase 3‐mediated apoptotic machinery

Abstract

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.

Desmoglein-2: A Novel Regulator of Apoptosis in the Intestinal Epithelium

“…A significant decrease in tDsg2 after the treatment of the IECs with the caspase inhibitor Z-VAD(OMe)-FMK was observed. These findings and another report (Cirillo et al, 2008) support involvement of a caspase(s) in Dsg2 cleavage. Whether tDsg2 is a caspase-induced proteolytic product in apoptosis remains to be determined.…”

“…However, the closely related armadillo family proteins ␤-catenin and p120, which localize predominantly in adherens junctions, did not colocalize with the internalized Dsg2 C terminus (data not shown), suggesting that Pg is associated with the internalized Dsg2 C terminus. That the internalized Dsg2 C terminus colocalized with Pg, but not DSP, suggests that interactions between desmosomal plaque components are disrupted during the onset of apoptosis as shown in other desmosomal disassembly models (Calkins et al, 2006;Cirillo et al, 2008). In further support of a possible role of Pg in early phase of apoptosis, we also observed an increase in the TX-100 -insoluble pool of Pg (data not shown).…”

150th Anniversary Series: Desmosomes and the Hallmarks of Cancer

“…During apoptosis, a large set of substrate proteins including adhesion molecules including desmosomal cadherins, cytoskeletal proteins, and their regulators were identified as caspase substrates. Interestingly, after induction of apoptosis not only a caspase-mediated cleavage within the cytosolic domain but also a release of the extracellular domain of desmosomal cadherins was observed Cirillo et al, 2008;Dusek et al, 2006;Weiske et al, 2001). In addition, proteins of the desmosomal plaque have been identified as caspase targets (Aho, 2004;Kalinin et al, 2005;Weiske et al, 2001).…”

Pemphigus vulgaris autoimmune globulin induces Src-dependent tyrosine-phosphorylation of plakophilin 3 and its detachment from desmoglein 3

“…Immunofluorescence procedures and the extent of cell detachment (acantholysis) in cell monolayers were measured according to previously published protocols [15] with minor modifications [16]. Briefly, the images of 10 representative microscopic fields were recorded and the percentage of acantholysis in each field was computed by subtracting the percentage of the area of cell coverage from the total area of the microscopic field (taken as 100%).…”