Epithelial cell-cell adhesion is controlled by multiprotein complexes that include E-cadherin-mediated adherens junctions (AJs) and ZO-1-containing tight junctions (TJs). Previously, we reported that reduction of E-cadherin N-glycosylation in normal and cancer cells promoted stabilization of AJs through changes in the composition and cytoskeletal association of E-cadherin scaffolds. Here, we show that enhanced interaction of hypoglycosylated E-cadherin-containing AJs with protein phosphatase 2A (PP2A) represents a mechanism for promoting TJ assembly. In MDCK cells, attenuation of cellular N-glycosylation with siRNA to DPAGT1, the first gene in the N-glycosylation pathway, reduced N-glycosylation of surface E-cadherin and resulted in increased recruitment of stabilizing proteins gamma-catenin, alpha-catenin, vinculin and PP2A to AJs. Greater association of PP2A with AJs correlated with diminished binding of PP2A to ZO-1 and claudin-1 and with increased pools of serine-phosphorylated ZO-1 and claudin-1. More ZO-1 was found in complexes with occludin and claudin-1, and this corresponded to enhanced transepithelial resistance (TER), indicating physiological assembly of TJs. Similar maturation of AJs and TJs was detected after transfection of MDCK cells with the hypoglycosylated E-cadherin variant, V13. Our data indicate that E-cadherin N-glycans coordinate the maturity of AJs with the assembly of TJs by affecting the association of PP2A with these junctional complexes.
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| http://dx.doi.org/10.1016/j.yexcr.2010.02.008 | DOI Listing |
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Reductions in both expression of the dystroglycan core protein and functional glycosylation of the α-dystroglycan (αDG) subunit have been reported in a number of cancers and may contribute to disease progression. In the case of prostate cancer, one mechanism that contributes to αDG hypoglycosylation is transcriptional down-regulation of LARGE2 (GYLTY1B), a glycosyltransferase that produces the functional (laminin-binding) glycan on αDG, but the mechanism(s) underlying reduction of LARGE2 mRNA remain unclear. Here, we show that αDG hypoglycosylation is associated with epithelial-to-mesenchymal transition (EMT)-like status.
View Article and Find Full Text PDF[Effect of hypoglycosylated E-cadherins on proliferation and invasiveness of tongue squamous cell carcinoma].
Shanghai Kou Qiang Yi Xue
February 2014
School of Stomatology, Shandong University. Jinan 250012;Shandong Province,
Purpose: To investigate the effect of N-glycosylated E-cadherins on proliferation and invasiveness of tongue squamous cell carcinoma CAL 27 cells, and to study the effect of hypoglycosylation of E-cadherins on the stability of adherens junctions (AJs) mediated by E-cadherins.
Methods: Human tongue squamous cell carcinoma CAL 27 cells were respectively transfected with the plasmids encoding either hypoglycosylated or wild-type E-cadherins with FLAG as tags. Western blot of FLAG was used to detect the expression of exogenous E-cadherins in the transfected cells after 48 hours.
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Department of Molecular and Cell Biology, Boston University Medical Center, 72 East Concord Street, EVANS-E438, Boston, MA 02118, USA.
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Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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Department of Molecular and Cell Biology, Boston University Medical Campus, Boston, MA, USA.
Oral cancer is one of the most aggressive epithelial malignancies, whose incidence is on the rise. Previous studies have shown that in a subset of human oral squamous cell carcinoma (OSCC) tumor specimens, overexpression of the DPAGT1 gene, encoding the dolichol-P-dependent N-acetylglucoseamine-1-phosphate transferase, a key regulator of the metabolic pathway of protein N-glycosylation, drives tumor cell discohesion by inhibiting E-cadherin adhesive function. Recently, we reported that DPAGT1 was a target of the canonical Wnt signaling pathway.
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