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Coordinate regulation of N-glycosylation gene DPAGT1, canonical Wnt signaling and E-cadherin adhesion.

ABSTRACT: The metabolic pathway of protein N-glycosylation influences intercellular adhesion by affecting the composition and cytoskeletal association of E-cadherin protein complexes, or adherens junctions (AJs). In sparse cells, E-cadherin is modified extensively with complex N-glycans and forms nascent AJs, while in dense cultures, hypoglycosylated E-cadherin drives the assembly of mature AJs with increased levels of ?- and ?-catenins. N-glycosylation of E-cadherin is controlled by the DPAGT1 gene, a key regulator of the N-glycosylation pathway. DPAGT1 is a target of the canonical Wnt signaling pathway, with both ?- and ?-catenins binding to Tcf at its promoter. We now report that DPAGT1 senses cell density through canonical Wnt signaling. In dense cells, depletion of ?-catenin from the DPAGT1 promoter correlated with downregulation of its cellular abundance, while loss of nuclear ?-catenin reflected its greater recruitment to AJs. DPAGT1 itself affected canonical Wnt signaling, with forced changes in its expression resulting in corresponding changes in transcriptionally active ?-catenin and canonical Wnt activity. Remarkably, a 2.4-fold increase in the DPAGT1 mRNA level resulted in increased N-glycosylation and reduced membrane localization of E-cadherin, coincident with dramatic changes in cell morphology. Lastly, we present evidence that N-glycosylation status of E-cadherin controls its antagonism of canonical Wnt signaling. Transfection of hypoglycosylated E-cadherin mutant, V13, but not fully N-glycosylated E-cadherin, into sparse cells inhibited canonical Wnt activity by depleting nuclear ?- and ?-catenins. Collectively, our studies show that cells coordinate DPAGT1 expression and protein N-glycosylation with canonical Wnt signaling and E-cadherin adhesion via positive and negative feedback mechanisms.

SUBMITTER: Sengupta PK

PROVIDER: S-EPMC3613180 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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Coordinate regulation of N-glycosylation gene DPAGT1, canonical Wnt signaling and E-cadherin adhesion.

Sengupta Pritam K PK Bouchie Meghan P MP Nita-Lazar Mihai M Yang Hsiao-Ying HY Kukuruzinska Maria A MA

Journal of cell science 20121123 Pt 2

The metabolic pathway of protein N-glycosylation influences intercellular adhesion by affecting the composition and cytoskeletal association of E-cadherin protein complexes, or adherens junctions (AJs). In sparse cells, E-cadherin is modified extensively with complex N-glycans and forms nascent AJs, while in dense cultures, hypoglycosylated E-cadherin drives the assembly of mature AJs with increased levels of γ- and α-catenins. N-glycosylation of E-cadherin is controlled by the DPAGT1 gene, a ke ...[more]

PMID: 23178939

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Project description:The cellular network composed of the evolutionarily conserved metabolic pathways of protein N-glycosylation, Wnt/?-catenin signaling pathway, and E-cadherin-mediated cell-cell adhesion plays pivotal roles in determining the balance between cell proliferation and intercellular adhesion during development and in maintaining homeostasis in differentiated tissues. These pathways share a highly conserved regulatory molecule, ?-catenin, which functions as both a structural component of E-cadherin junctions and as a co-transcriptional activator of the Wnt/?-catenin signaling pathway, whose target is the N-glycosylation-regulating gene, DPAGT1. Whereas these pathways have been studied independently, little is known about the dynamics of their interaction. Here we present the first numerical model of this network in MDCK cells. Since the network comprises a large number of molecules with varying cell context and time-dependent levels of expression, it can give rise to a wide range of plausible cellular states that are difficult to track. Using known kinetic parameters for individual reactions in the component pathways, we have developed a theoretical framework and gained new insights into cellular regulation of the network. Specifically, we developed a mathematical model to quantify the fold-change in concentration of any molecule included in the mathematical representation of the network in response to a simulated activation of the Wnt/ ?-catenin pathway with Wnt3a under different conditions. We quantified the importance of protein N-glycosylation and synthesis of the DPAGT1 encoded enzyme, GPT, in determining the abundance of cytoplasmic ?-catenin. We confirmed the role of axin in ?-catenin degradation. Finally, our data suggest that cell-cell adhesion is insensitive to E-cadherin recycling in the cell. We validate the model by inhibiting ?-catenin-mediated activation of DPAGT1 expression and predicting changes in cytoplasmic ?-catenin concentration and stability of E-cadherin junctions in response to DPAGT1 inhibition. We show the impact of pathway dysregulation through measurements of cell migration in scratch-wound assays. Collectively, our results highlight the importance of numerical analyses of cellular networks dynamics to gain insights into physiological processes and potential design of therapeutic strategies to prevent epithelial cell invasion in cancer.

Project description:Wnt signaling and cadherin-mediated adhesion have been implicated in both processes of embryonic development and the progression of carcinomas. Recent experimental studies revealed that Wnt signaling and cadherin-mediated cell adhesion have close crosstalk with each other. A comprehensive model that investigates the dynamic balance of ?-catenins in Wnt signaling and cell adhesion will improve our understanding to embryonic development and carcinomas. We constructed a network model to evaluate the dynamic interplay between adhesion and Wnt signaling. The network is decomposed into three interdependent modules: the cell adhesion, the degradation circle and the transcriptional regulation. In the cell adhesion module, we consider the effect of cadherin's lateral clustering. We found adhesion negatively contributes to Wnt signaling through competition for cytoplasmic ?-catenins. In the network of degradation circle, we incorporated features from various existing models. Our simulations reproduced the most recent experimental phenomena with semi-quantitative accuracy. Finally, in the transcriptional regulation module, we developed a function selection strategy to analyze the outcomes of genetic feedback loops in modulating the gene expression of Wnt targets. The specific cellular phenomena such as cadherin switch and Axin oscillation were archived and their biological insights were discussed. Our model provides the theoretical basis of how spatial organization regulates the dynamics of cellular signaling pathways. We suggest that cell adhesion affects Wnt signaling in both negative and positive ways. Cadherins can inhibit Wnt signaling not only in a way as a stoichiometric binding partner of ?-catenins that sequesters them from signaling, but also in a way through their clustering to impacts the rate at which ?-catenins are involved in the destruction loop. Additionally, cadherin clustering increases the phosphorylation rate of ?-catenins and promotes its signaling in nucleus.

Dataset Information

Coordinate regulation of N-glycosylation gene DPAGT1, canonical Wnt signaling and E-cadherin adhesion.

Publications

Coordinate regulation of N-glycosylation gene DPAGT1, canonical Wnt signaling and E-cadherin adhesion.

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