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Interlocked positive and negative feedback network motifs regulate ?-catenin activity in the adherens junction pathway.

ABSTRACT: The integrity of epithelial tissue architecture is maintained through adherens junctions that are created through extracellular homotypic protein-protein interactions between cadherin molecules. Cadherins also provide an intracellular scaffold for the formation of a multiprotein complex that contains signaling proteins, including ?-catenin. Environmental factors and controlled tissue reorganization disrupt adherens junctions by cleaving the extracellular binding domain and initiating a series of transcriptional events that aim to restore tissue homeostasis. However, it remains unclear how alterations in cell adhesion coordinate transcriptional events, including those mediated by ?-catenin in this pathway. Here were used quantitative single-cell and population-level in vitro assays to quantify the endogenous pathway dynamics after the proteolytic disruption of the adherens junctions. Using prior knowledge of isolated elements of the overall network, we interpreted these data using in silico model-based inference to identify the topology of the regulatory network. Collectively the data suggest that the regulatory network contains interlocked network motifs consisting of a positive feedback loop, which is used to restore the integrity of adherens junctions, and a negative feedback loop, which is used to limit ?-catenin-induced gene expression.

SUBMITTER: Klinke DJ

PROVIDER: S-EPMC4710243 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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Interlocked positive and negative feedback network motifs regulate β-catenin activity in the adherens junction pathway.

Klinke David J DJ Horvath Nicholas N Cuppett Vanessa V Wu Yueting Y Deng Wentao W Kanj Rania R

Molecular biology of the cell 20150729 22

The integrity of epithelial tissue architecture is maintained through adherens junctions that are created through extracellular homotypic protein-protein interactions between cadherin molecules. Cadherins also provide an intracellular scaffold for the formation of a multiprotein complex that contains signaling proteins, including β-catenin. Environmental factors and controlled tissue reorganization disrupt adherens junctions by cleaving the extracellular binding domain and initiating a series of ...[more]

PMID: 26224311

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Project description:Background: Negative-pressure wound therapy has become widely available in modern chronic wound cares. Accelerated keratinocyte (HaCaT cell) movements and decreased E-cadherin expressions induced by the applied negative pressure gradient of 125 mmHg (NP) have been reported in previous studies. However, the molecular mechanism for E-cadherin regulations under NP remains unexplored. We highlighted the signal transduction involved in NP-induced E-cadherin regulation for keratinocytes in the study. Results: Microarray results showed that catenin 1 (CTNND1) gene, the gene encoding the p120-catenin (p120ctn) in cell-cell junctions, was significantly (p = 0.0005) upregulated in HaCaT cells under NP for 12 hours in comparison with those at ambient pressure (AP). Cell fractionations and immunoblotting data showed that NP increased p120ctn phosphorylation, and resulted in p120ctn translocation from the plasma membrane to the cytoplasm. Fluorescent stains suggested that NP diminished the co-localization of p120ctn and E-cadherin on the plasma membrane. Similar phenomenon was also observed in the cells with overexpressed p120ctn at NP. Interestingly, overexpression of dN- p120ctn, a deletion mutant of p120ctn without the N-terminal phosphorylation sites, restored the adherens junctions (AJ) at NP. Knockdown of p120ctn with lentiviral small hairpin RNA not only diminished E-cadherin expressions but also accelerated cell movement at AP. Conclusions: Phosphorylation of p120ctn is endowed to respond rapidly to NP and contributes to the AJ disassembly. This NP-induced E-cadherin downregulation can possibly accelerate wound-healing process. Conclusions: Phosphorylation of p120ctn is endowed to respond rapidly to NP and contributes to the AJ disassembly. This NP-induced E-cadherin downregulation can possibly accelerate wound-healing process. HaCaT cells under negative pressure (NP) gradient of 125 mmHg for 12 hours in comparison with those at ambient pressure (AP) were tested for RNA extraction and hybridization on Affymetrix microarrays. The experiments have been biological replicated three times. The differential expression gene between NP and AP were selected and validated with qPCR method.

Project description:UNLABELLED:Gap junctional intercellular communication (GJIC) plays a critical role in the regulation of tissue homeostasis and carcinogenesis and is modulated by the levels, subcellular localization, and posttranslational modification of gap junction proteins, the connexins (Cx). Here, using oval cell-like rat liver epithelial cells, we demonstrate that the RNA-binding protein HuR promotes GJIC through two mechanisms. First, HuR silencing lowered the levels of Cx43 protein and Cx43 messenger RNA (mRNA), and decreased Cx43 mRNA half-life. This regulation was likely due to the direct stabilization of Cx43 mRNA by HuR, because HuR associated directly with Cx43 mRNA, a transcript that bears signature adenylate-uridylate-rich (AU-rich) and uridylate-rich (U-rich) sequences in its 3'-untranslated region. Second, HuR silencing reduced both half-life and the levels of beta-catenin mRNA, also a target of HuR; accordingly, HuR silencing lowered the levels of whole-cell and membrane-associated beta-catenin. Coimmunoprecipitation experiments showed a direct interaction between beta-catenin and Cx43. Small interfering RNA (siRNA)-mediated depletion of beta-catenin recapitulated the effects of decreasing HuR levels: it attenuated GJIC, decreased Cx43 levels, and redistributed Cx43 to the cytoplasm, suggesting that depletion of beta-catenin in HuR-silenced cells contributed to lowering Cx43 levels at the membrane. Finally, HuR was demonstrated to support GJIC after exposure to a genotoxic agent, doxorubicin, or an inducer of differentiation processes, retinoic acid, thus pointing to a crucial role of HuR in the cellular response to stress and in physiological processes modulated by GJIC. CONCLUSION:HuR promotes gap junctional intercellular communication in rat liver epithelial cells through two related regulatory processes, by enhancing the expression of Cx43 and by increasing the expression of beta-catenin, which, in turn, interacts with Cx43 and is required for proper positioning of Cx43 at the plasma membrane.

Dataset Information

Interlocked positive and negative feedback network motifs regulate ?-catenin activity in the adherens junction pathway.

Publications

Interlocked positive and negative feedback network motifs regulate β-catenin activity in the adherens junction pathway.

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