Cleavage of β-Catenin and Plakoglobin and Shedding of VE-Cadherin during Endothelial Apoptosis: Evidence for a Role for Caspases and Metalloproteinases

Abstract

Growth factor deprivation of endothelial cells induces apoptosis, which is characterized by membrane blebbing, cell rounding, and subsequent loss of cell-matrix and cell-cell contacts. In this study, we show that initiation of endothelial apoptosis correlates with cleavage and disassembly of intracellular and extracellular components of adherens junctions. beta-Catenin and plakoglobin, which form intracellular links between vascular endothelial cadherin (VE-cadherin) and actin-binding alpha-catenin in adherens junctions, are cleaved in apoptotic cells. In vitro incubations of cell lysates and immunoprecipitates with recombinant caspases indicate that CPP32 and Mch2 are involved, possibly by initiating proteolytic processing. Cleaved beta-catenin from lysates of apoptotic cells does not bind to endogenous alpha-catenin, whereas plakoglobin retains its binding capacity. The extracellular portion of the adherens junctions is also altered during apoptosis because VE-cadherin, which mediates endothelial cell-cell interactions, dramatically decreases on the surface of cells. An extracellular fragment of VE-cadherin can be detected in the conditioned medium, and this "shedding" of VE-cadherin can be blocked by an inhibitor of metalloproteinases. Thus, cleavage of beta-catenin and plakoglobin and shedding of VE-cadherin may act in concert to disrupt structural and signaling properties of adherens junctions and may actively interrupt extracellular signals required for endothelial cell survival.

Extracellular cleavage and shedding of P-cadherin: a mechanism underlying the invasive behaviour of breast cancer cells

“…The mechanism of ectodomain cleavage of adhesion proteins, mediated by MMPs, has been already well described (Lochter et al, 1997;Herren et al, 1998;Noe et al, 2001). MMP-3 and MMP-7 have a role in the shedding of the extracellular domain of E-cadherin, generating a soluble 80 kDa fragment (Noe et al, 2001).…”

“…Given that MMPs were already described to shed the extracellular domains of membrane glycoproteins, including E-cadherin, giving rise to a soluble fragment with pro-invasive activity (Lochter et al, 1997;Herren et al, 1998;Noe et al, 2001), we looked forward for the presence of soluble fragments of cadherins in the conditioned medium from the studied cell lines. Surprisingly, no significant differences were observed concerning the presence of soluble E-cadherin (sE-cad); however, sP-cad was increased 8.7-fold in the conditioned medium from MCF-7/AZ.Pcad cells (Figure 6c).…”

Bioelectrical impedance assay to monitor changes in cell shape during apoptosis

“…Herein, catenins are the molecular linker between the microfilaments and specialized transmembrane proteins, so-called cadherins, that make contact to cadherins on the opposing cell surface. Herren et al (1998) furthermore found cleavage of the extracellular domains of VE-cadherin in apoptotic endothelial cells by secreted matrix metallo-proteinases (MMP). Thus, the rapid decrease of impedance after induction of apoptosis may be the result of both processes: disintegration of adherens junctions in concert with proteolysis of actin filaments.…”

Wnt-signalling pathway in ovarian epithelial tumours: increased expression of β-catenin and GSK3β

“…In fact, the absence of E-cadherin can lead to an accumulation of free bcatenin and increased transactivation, which can be competed out by transient transfections with E-cadherin (Orsulic et al, 1999). Beta-catenin was recently found to be involved in apoptosis (Herren et al, 1998). Their finding that caspases have the capacity to cleave b-catenin proteolytically at the N-and C-terminal, which will reduce a-catenin binding, release actin filaments and reduce cell -cell interaction, indicates that b-catenin has an important role at a late stage of apoptosis.…”