ABSTRACT
δ-Catenin binds the juxtamembrane domain of E-cadherin and is known to be overexpressed in some human tumors. However, the functions of δ-catenin in epithelial cells and carcinomas remain elusive. We found that prostate cancer cells overexpressing δ-catenin show an increase in multi-layer growth in culture. In these cells, δ-catenin colocalizes with E-cadherin at the plasma membrane, and the E-cadherin processing is noticeably elevated. E-Cadherin processing induced by δ-catenin is serum-dependent and requires MMP- and PS-1/γ-secretase-mediated activities. A deletion mutant of δ-catenin that deprives the ability of δ-catenin to bind E-cadherin or to recruit PS-1 to E-cadherin totally abolishes the δ-catenin-induced E-cadherin processing and the multi-layer growth of the cells. In addition, prostate cancer cells overexpressing δ-catenin display an elevated total ß-catenin level and increase its nuclear distribution, resulting in the activation of ß-catenin/LEF-1-mediated transcription and their downstream target genes as well as androgen receptor-mediated transcription. Indeed, human prostate tumor xenograft in nude mice, which is derived from cells overexpressing δ-catenin, shows increased ß-catenin nuclear localization and more rapid growth rates. Moreover, the metastatic xenograft tumor weights positively correlate with the level of 29kD E-cadherin fragment, and primary human prostate tumor tissues also show elevated levels of δ-catenin expression and the E-cadherin processing. Taken together, these results suggest that δ-catenin plays an important role in prostate cancer progression through inducing E-cadherin processing and thereby activating ß-catenin-mediated oncogenic signals.
Subject(s)
Cadherins/metabolism , Catenins/physiology , Prostatic Neoplasms/pathology , Protein Processing, Post-Translational , Signal Transduction/physiology , beta Catenin/physiology , Animals , Cell Line, Tumor , Disease Progression , Humans , Male , Mice , Mice, Nude , Delta CateninABSTRACT
E-cadherin is a member of the cadherin family of Ca(2+)-dependent cell-cell adhesion molecules. p120-Catenin and delta-catenin are known to bind to similar juxtamembrane regions of E-cadherin, and p120-catenin is known to stabilize E-cadherin. However, the function of competition between p120-catenin and delta-catenin for E-cadherin has not been fully explained. In this report, we show that cells overexpressing delta-catenin contain less p120-catenin than control cells at the cell-cell interface and that this causes the relocalization of p120-catenin from the plasma membrane to the cytosol. We show that successful binding by either one to E-cadherin adversely affects the stability of the other.
Subject(s)
Adenocarcinoma/metabolism , Cadherins/metabolism , Catenins/metabolism , Neoplasm Proteins/metabolism , Prostatic Neoplasms/metabolism , Animals , Binding, Competitive , Catenins/chemistry , Catenins/genetics , Cell Line, Tumor , Cytosol/metabolism , Gene Expression Regulation, Neoplastic , Humans , Male , Membrane Proteins/metabolism , Mice , NIH 3T3 Cells , Protein Binding , Protein Isoforms/metabolism , Protein Stability , Protein Structure, Tertiary , Protein Transport , Recombinant Fusion Proteins/metabolism , Up-Regulation , Delta CateninABSTRACT
Delta-catenin was first identified because of its interaction with presenilin-1, and its aberrant expression has been reported in various human tumors and in patients with Cri-du-Chat syndrome, a form of mental retardation. However, the mechanism whereby delta-catenin is regulated in cells has not been fully elucidated. We investigated the possibility that glycogen-synthase kinase-3 (GSK-3) phosphorylates delta-catenin and thus affects its stability. Initially, we found that the level of delta-catenin was greater and the half-life of delta-catenin was longer in GSK-3beta(-/-) fibroblasts than those in GSK-3beta(+/+) fibroblasts. Furthermore, four different approaches designed to specifically inhibit GSK-3 activity, i.e. GSK-3-specific chemical inhibitors, Wnt-3a conditioned media, small interfering RNAs, and GSK-3alpha and -3beta kinase dead constructs, consistently showed that the levels of endogenous delta-catenin in CWR22Rv-1 prostate carcinoma cells and primary cortical neurons were increased by inhibiting GSK-3 activity. In addition, it was found that both GSK-3alpha and -3beta interact with and phosphorylate delta-catenin. The phosphorylation of DeltaC207-delta-catenin (lacking 207 C-terminal residues) and T1078A delta-catenin by GSK-3 was noticeably reduced compared with that of wild type delta-catenin, and the data from liquid chromatography-tandem mass spectrometry analyses suggest that the Thr(1078) residue of delta-catenin is one of the GSK-3 phosphorylation sites. Treatment with MG132 or ALLN, specific inhibitors of proteosome-dependent proteolysis, increased delta-catenin levels and caused an accumulation of ubiquitinated delta-catenin. It was also found that GSK-3 triggers the ubiquitination of delta-catenin. These results suggest that GSK-3 interacts with and phosphorylates delta-catenin and thereby negatively affects its stability by enabling its ubiquitination/proteosome-mediated proteolysis.
Subject(s)
Cell Adhesion Molecules/metabolism , Glycogen Synthase Kinase 3/metabolism , Phosphoproteins/metabolism , Proteasome Endopeptidase Complex/chemistry , Ubiquitin/chemistry , Animals , Catenins , Culture Media, Conditioned/pharmacology , Enzyme Inhibitors/pharmacology , Fibroblasts/metabolism , Glycogen Synthase Kinase 3 beta , Humans , Mice , Neurons/metabolism , Phosphorylation , Rats , Rats, Sprague-Dawley , Delta CateninABSTRACT
Wnt and Notch1 signaling pathways play an important role in a variety of biological processes including embryonic induction, the polarity of cell division, cell fate, and cell growth. Although there is evidence that the two main signaling pathways can modulate each other, the precise mechanism is not completely understood. This report shows that beta-catenin can regulate the level and transcriptional activity of the Notch1 and Notch1 intracellular domain (NICD). The in vivo and in vitro results demonstrate that beta-catenin binds with Notch1 and NICD, for which its Armadillo repeat domain is essential. It was further demonstrated that beta-catenin could upregulate the level of Notch1 and NICD, possibly by competing the common ubiquitin-dependent degradation machinery. In addition, beta-catenin enhanced the transcriptional activity of NICD on the hairy and enhancer of split 1 (HES1) and CSL through its C-terminal transactivation domain. This effect of cooperative regulation by beta-catenin could also be observed in bone morphogenetic protein 2 (BMP2) induced osteogenic differentiation of C2C12 cells. beta-catenin coexpression with NICD enhanced the alkaline phosphatase (ALP) activity in C2C12 cells compared with either beta-catenin or NICD expression alone. Culturing C2C12 cells on Delta-1 coated dishes together with Wnt3-conditioned media induced noticeable increases in ALP staining, verifying that employed physiological levels of NICD and beta-catenin are sufficient to induce ALP activation. Furthermore, effects of beta-catenin on Notch1 were dramatically diminished by overexpressed LEF1. Overall, our data suggest that beta-catenin can act as a switching molecule between the classical TCF/LEF1 mediated pathway and NICD mediated pathway.
