Zhao H, Liang Y, Xu Z, Wang L, Zhou F, Li Z, Jin J, Yang Y, Fang Z, Hu Y, Zhang L, Su J, Zha XN-glycosylation affects the adhesive function of E-Cadherin through modifying the composition of adherens junctions (AJs) in human breast carcinoma cell line MDA-MB-435. J Cell Biochem 104(1): 162-175
ABSTRACT E-cadherin mediates calcium-dependent cell-cell adhesion between epithelial cells. The ectodomain of human E-cadherin contains four potential N-glycosylation sites at Asn residues 554, 566, 618, and 633. In this study, the role of N-glycosylation in E-cadherin-mediated cell-cell adhesion was investigated by site-directed mutagenesis. In MDA-MB-435 cells, all four potential N-glycosylation sites of human E-cadherin were N-glycosylated. Removal of N-glycan at Asn-633 dramatically affected E-cadherin stability. In contrast, mutant E-cadherin lacking the other three N-glycans showed similar protein stability in comparison with wild-type E-cadherin. Moreover, N-glycans at Asn-554 and Asn-566 were found to affect E-cadherin-mediated calcium-dependent cell-cell adhesion, and removal of either of the two N-glycans caused a significant decrease in calcium-dependent cell-cell adhesion accompanied with elevated cell migration. Analysis of the composition of adherens junctions (AJs) revealed that removal of N-glycans on E-cadherin resulted in elevated tyrosine phosphorylation level of beta-catenin and reduced beta- and alpha-catenins at AJs. These findings demonstrate that N-glycosylation may affect the adhesive function of E-cadherin through modifying the composition of AJs.
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- "Nutrient stress reduces LGR5 expression demonstrated that LGR5 membrane expression was dramatically reduced in both TMC-treated LoVo and LS174t-LGR5 cells (Figure 2C and D, respectively). Detection of E-cadherin in LoVo cells served not only as a membrane marker, but also demonstrated that TMC treatment does not universally deplete cell surface expression of all glycosylated membrane proteins such as E-cadherin (Figure 2E) (Zhao et al, 2008). Detection of E-cadherin in the LS174t cell line was not possible in keeping with a previously reported CDH1 mutation (Efstathiou et al, 1999). "
ABSTRACT: Background: LGR5 is an important marker of intestinal stem cells and performs its vital functions at the cell membrane. Despite the importance of LGR5 to both normal and cancer stem cell biology, it is not known how microenvironmental stress affects the expression and subcellular distribution of the protein. Methods: Nutrient stress was induced through glucose starvation. Glycosylation status was assessed using endoglycosidase or tunicamycin treatment. Flow cytometry and confocal microscopy were used to assess subcellular distribution of LGR5. Results: Glucose deprivation altered the glycosylation status of LGR5 resulting in reduced protein stability and cell surface expression. Furthermore, inhibiting LGR5 glycosylation resulted in depleted surface expression and reduced localisation in the cis-Golgi network. Conclusions: Nutrient stress within a tumour microenvironment has the capacity to alter LGR5 protein stability and membrane localisation through modulation of LGR5 glycosylation status. As LGR5 surface localisation is required for enhanced Wnt signalling, this is the first report to show a mechanism by which the microenvironment could affect LGR5 function.British Journal of Cancer 01/2015; 112(4). DOI:10.1038/bjc.2015.4 · 4.84 Impact Factor
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- "Western blot analysis indicated no shift in electrophoretic migration by SDS PAGE, suggesting that LSR was not heavily glycosylated (Additional file 2: Figure S2A). To verify that the de-glycosylating agents were functioning properly in the same cell line, expression of a known glycoprotein (E-cadherin) was assessed [43,44]. Treatment of MCF-7 cells with tunicamycin or swainsonine decreased the levels of glycosylated E-cadherin (top band) and increased the non-glycosylated (bottom) bands, thus confirming activity of the de-glycosylation agents (Additional file 2: Figure S2A). "
ABSTRACT: Background Translational exploration of bacterial toxins has come to the forefront of research given their potential as a chemotherapeutic tool. Studies in select tissues have demonstrated that Clostridium perfringens iota toxin binds to CD44 and lipolysis stimulated lipoprotein receptor (LSR) cell-surface proteins. We recently demonstrated that LSR expression correlates with estrogen receptor positive breast cancers and that LSR signaling directs aggressive, tumor-initiating cell behaviors. Herein, we identify the mechanisms of iota toxin cytotoxicity in a tissue-specific, breast cancer model with the ultimate goal of laying the foundation for using iota toxin as a targeted breast cancer therapy. Methods In vitro model systems were used to determine the cytotoxic effect of iota toxin on breast cancer intrinsic subtypes. The use of overexpression and knockdown technologies confirmed the roles of LSR and CD44 in regulating iota toxin endocytosis and induction of cell death. Lastly, cytotoxicity assays were used to demonstrate the effect of iota toxin on a validated set of tamoxifen resistant breast cancer cell lines. Results Treatment of 14 breast cancer cell lines revealed that LSR+/CD44- lines were highly sensitive, LSR+/CD44+ lines were slightly sensitive, and LSR-/CD44+ lines were resistant to iota cytotoxicity. Reduction in LSR expression resulted in a significant decrease in toxin sensitivity; however, overexpression of CD44 conveyed toxin resistance. CD44 overexpression was correlated with decreased toxin-stimulated lysosome formation and decreased cytosolic levels of iota toxin. These findings indicated that expression of CD44 drives iota toxin resistance through inhibition of endocytosis in breast cancer cells, a role not previously defined for CD44. Moreover, tamoxifen-resistant breast cancer cells exhibited robust expression of LSR and were highly sensitive to iota-induced cytotoxicity. Conclusions Collectively, these data are the first to show that iota toxin has the potential to be an effective, targeted therapy for breast cancer.Molecular Cancer 07/2014; 13(1):163. DOI:10.1186/1476-4598-13-163 · 4.26 Impact Factor
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- "N-glycosylation contributes up to 20% of E-cadherin total mass, and several reports support the involvement of N-glycans in the modulation of E-cadherin-mediated tumor cell-cell adhesion , , . E-cadherin sialylation pattern was evaluated by immunoprecipitation followed by lectin blot analysis. "
ABSTRACT: In our previous studies we have described that ST3Gal III transfected pancreatic adenocarcinoma Capan-1 and MDAPanc-28 cells show increased membrane expression levels of sialyl-Lewis x (SLex) along with a concomitant decrease in α2,6-sialic acid compared to control cells. Here we have addressed the role of this glycosylation pattern in the functional properties of two glycoproteins involved in the processes of cancer cell invasion and migration, α2β1 integrin, the main receptor for type 1 collagen, and E-cadherin, responsible for cell-cell contacts and whose deregulation determines cell invasive capabilities. Our results demonstrate that ST3Gal III transfectants showed reduced cell-cell aggregation and increased invasive capacities. ST3Gal III transfected Capan-1 cells exhibited higher SLex and lower α2,6-sialic acid content on the glycans of their α2β1 integrin molecules. As a consequence, higher phosphorylation of focal adhesion kinase tyrosine 397, which is recognized as one of the first steps of integrin-derived signaling pathways, was observed in these cells upon adhesion to type 1 collagen. This molecular mechanism underlies the increased migration through collagen of these cells. In addition, the pancreatic adenocarcinoma cell lines as well as human pancreatic tumor tissues showed colocalization of SLex and E-cadherin, which was higher in the ST3Gal III transfectants. In conclusion, changes in the sialylation pattern of α2β1 integrin and E-cadherin appear to influence the functional role of these two glycoproteins supporting the role of these glycans as an underlying mechanism regulating pancreatic cancer cell adhesion and invasion.PLoS ONE 05/2014; 9(5):e98595. DOI:10.1371/journal.pone.0098595 · 3.23 Impact Factor