Wnt signaling controls the phosphorylation status of beta-catenin

Impact of GSK-3β and CK-1δ on Wnt signaling pathway in alzheimer disease: A dual target approach

Alzheimer's disease (AD) is an enigmatic neurological illness that offers few treatment options. Recent exploration has highlighted the crucial connection of the Wnt signaling pathway in AD pathogenesis, shedding light on potential therapeutic targets. The present study focuses on the dual targeting of glycogen synthase kinase-3β (GSK-3β) and casein kinase-1δ (CK-1δ) within the framework of the Wnt signaling pathway as a possible technique for AD intervention. GSK-3β and CK-1δ are multifunctional kinases known for their roles in tau hyperphosphorylation, amyloid processing, and synaptic dysfunction, all of which are major hallmarks of Alzheimer's disease. They are intricately linked to Wnt signaling, which plays a pivotal part in sustaining neuronal function and synaptic plasticity. Dysregulation of the Wnt pathway in AD contributes to cognitive decline and neurodegeneration. This review delves into the molecular mechanisms by which GSK-3β and CK-1δ impact the Wnt signaling pathway, elucidating their roles in AD pathogenesis. We discuss the potential of small-molecule inhibitors along with their SAR studies along with the multi-targetd approach targeting GSK-3β and CK-1δ to modulate Wnt signaling and mitigate AD-related pathology. In summary, the dual targeting of GSK-3β and CK-1δ within the framework of the Wnt signaling pathway presents an innovative and promising avenue for future AD therapies, offering new hope for patients and caregivers in the quest to combat this challenging condition.

EGFR-dependent endocytosis of Wnt9a and Fzd9b promotes β-catenin signaling during hematopoietic stem cell development in zebrafish

Cell-to-cell communication through secreted Wnt ligands that bind to members of the Frizzled (Fzd) family of transmembrane receptors is critical for development and homeostasis. Wnt9a signals through Fzd9b, the co-receptor LRP5 or LRP6 (LRP5/6), and the epidermal growth factor receptor (EGFR) to promote early proliferation of zebrafish and human hematopoietic stem cells during development. Here, we developed fluorescently labeled, biologically active Wnt9a and Fzd9b fusion proteins to demonstrate that EGFR-dependent endocytosis of the ligand-receptor complex was required for signaling. In human cells, the Wnt9a-Fzd9b complex was rapidly endocytosed and trafficked through early and late endosomes, lysosomes, and the endoplasmic reticulum. Using small-molecule inhibitors and genetic and knockdown approaches, we found that Wnt9a-Fzd9b endocytosis required EGFR-mediated phosphorylation of the Fzd9b tail, caveolin, and the scaffolding protein EGFR protein substrate 15 (EPS15). LRP5/6 and the downstream signaling component AXIN were required for Wnt9a-Fzd9b signaling but not for endocytosis. Knockdown or loss of EPS15 impaired hematopoietic stem cell development in zebrafish. Other Wnt ligands do not require endocytosis for signaling activity, implying that specific modes of endocytosis and trafficking may represent a method by which Wnt-Fzd specificity is established.

Wnt signaling regulates chemokine production and cell migration of circulating human monocytes

The β-catenin dependent canonical Wnt signaling pathway plays a crucial role in maintaining normal homeostasis. However, when dysregulated, Wnt signaling is closely associated with various pathological conditions, including inflammation and different types of cancer.Here, we show a new connection between the leukocyte inflammatory response and the Wnt signaling pathway. Specifically, we demonstrate that circulating human primary monocytes express distinct Wnt signaling components and are susceptible to stimulation by the classical Wnt ligand-Wnt-3a. Although this stimulation increased the levels of β-catenin protein, the expression of the classical Wnt-target genes was not affected. Intriguingly, treating circulating human monocytes with Wnt-3a induces the secretion of cytokines and chemokines, enhancing monocyte migration. Mechanistically, the enhanced monocyte migration in response to Wnt stimuli is mediated through CCL2, a strong monocyte-chemoattractant.To further explore the physiological relevance of these findings, we conducted ex-vivo experiments using blood samples of patients with rheumatic joint diseases (RJD) - conditions where monocytes are known to be dysfunctional. Wnt-3a generated a unique cytokine expression profile, which was significantly distinct from that observed in monocytes obtained from healthy donors.Thus, our results provide the first evidence that Wnt-3a may serve as a potent stimulator of monocyte-driven immune processes. These findings contribute to our understanding of inflammatory diseases and, more importantly, shed light on the role of a core signaling pathway in the circulation.

Muscarinic receptor agonist-induced βPix binding to β-catenin promotes colon neoplasia

M3 muscarinic receptors (M3R) modulate β-catenin signaling and colon neoplasia. CDC42/RAC guanine nucleotide exchange factor, βPix, binds to β-catenin in colon cancer cells, augmenting β-catenin transcriptional activity. Using in silico, in vitro, and in vivo approaches, we explored whether these actions are regulated by M3R. At the invasive fronts of murine and human colon cancers, we detected co-localized nuclear expression of βPix and β-catenin in stem cells overexpressing M3R. Using immunohistochemistry, immunoprecipitation, proximity ligand, and fluorescent cell sorting assays in human tissues and established and primary human colon cancer cell cultures, we detected time-dependent M3R agonist-induced cytoplasmic and nuclear association of βPix with β-catenin. βPix knockdown attenuated M3R agonist-induced human colon cancer cell proliferation, migration, invasion, and expression of PTGS2, the gene encoding cyclooxygenase-2, a key player in colon neoplasia. Overexpressing βPix dose-dependently augmented β-catenin binding to the transcription factor TCF4. In a murine model of sporadic colon cancer, advanced neoplasia was attenuated in conditional knockout mice with intestinal epithelial cell deficiency of βPix. Expression levels of β-catenin target genes and proteins relevant to colon neoplasia, including c-Myc and Ptgs2, were reduced in colon tumors from βPix-deficient conditional knockout mice. Targeting the M3R/βPix/β-catenin axis may have therapeutic potential.

The WNT/β-catenin system in chronic kidney disease-mineral bone disorder syndrome

BACKGROUND

The WNT/β-catenin system is an evolutionarily conserved signaling pathway that plays a crucial role in morphogenesis and cell tissue formation during embryogenesis. Although usually suppressed in adulthood, it can be reactivated during organ damage and regeneration. Transient activation of the WNT/β-catenin pathway stimulates tissue regeneration after acute kidney injury, while persistent (uncontrolled) activation can promote the development of chronic kidney disease (CKD). CKD-MBD is a clinical syndrome that develops with systemic mineral and bone metabolism disorders caused by CKD, characterized by abnormal bone mineral metabolism and/or extraosseous calcification, as well as cardiovascular disease associated with CKD, including vascular stiffness and calcification.

OBJECTIVE

This paper aims to comprehensively review the WNT/β-catenin signaling pathway in relation to CKD-MBD, focusing on its components, regulatory molecules, and regulatory mechanisms. Additionally, this review highlights the challenges and opportunities for using small molecular compounds to target the WNT/β-catenin signaling pathway in CKD-MBD therapy.

METHODS

We conducted a comprehensive literature review using various scientific databases, including PubMed, Scopus, and Web of Science, to identify relevant articles. We searched for articles that discussed the WNT/β-catenin signaling pathway, CKD-MBD, and their relationship. We also reviewed articles that discussed the components of the WNT/β-catenin signaling pathway, its regulatory molecules, and regulatory mechanisms.

RESULTS

The WNT/β-catenin signaling pathway plays a crucial role in CKD-MBD by promoting vascular calcification and bone mineral metabolism disorders. The pathway's components include WNT ligands, Frizzled receptors, and LRP5/6 co-receptors, which initiate downstream signaling cascades leading to the activation of β-catenin. Several regulatory molecules, including GSK-3β, APC, and Axin, modulate β-catenin activation. The WNT/β-catenin signaling pathway also interacts with other signaling pathways, such as the BMP pathway, to regulate CKD-MBD.

CONCLUSIONS

The WNT/β-catenin signaling pathway is a potential therapeutic target for CKD-MBD. Small molecular compounds that target the components or regulatory molecules of the pathway may provide a promising approach to treat CKD-MBD. However, more research is needed to identify safe and effective compounds and to determine the optimal dosages and treatment regimens.

Downregulation of β-Catenin Contributes to type II Alveolar Epithelial Stem Cell Resistance to Epithelial-Mesenchymal Transition by Lowing Lin28/let-7 Ratios in Fibrosis-Resistant Mice after Thoracic Irradiation

Transdifferentiation of type II alveolar cells (AECII) is a major cause for radiation-induced lung fibrosis (RILF). Cell differentiation phenotype is determined by Lin28 (undifferentiated marker) and let-7 (differentiated marker) in a see-saw-pattern. Therefore, differentiation phenotype can be extrapolated based on Lin28/let-7 ratio. Lin28 is activated by β-catenin. To the best of our knowledge this study was the first to use the single primary AECII freshly isolated from irradiated lungs of fibrosis-resistant C3H/HeNHsd strain to further confirm RILF mechanism by comparing its differences in AECII phenotype status/state and cell differentiation regulators to fibrosis-prone C57BL/6j mice. Results showed that radiation pneumonitis and fibrotic lesions were seen in C3H/HeNHsd and C57BL/6j mouse strains, respectively. mRNAs of E-cadherin, EpCAM, HOPX and proSP-C (epithelial phenotype biomarkers) were significantly downregulated in single primary AECII isolated from irradiated lungs of both strains. Unlike C57BL/6j, α-SMA and Vimentin (mesenchymal phenotype biomarkers) were not upregulated in single AECII from irradiated C3H/HeNHsd. Profibrotic molecules, TGF-β1 mRNA was upregulated and β-catenin was significantly downregulated in AECII after irradiation (both P < 0.01). In contrast, transcriptions for GSK-3β, TGF-β1 and β-catenin were enhanced in isolated single AECII from irradiated C57BL/6j (P < 0.01-P < 0.001). The Lin28/let-7 ratios were much lower in single primary AECII from C3H/HeNHsd after irradiation vs. C57BL/6j. In conclusion, AECII from irradiated C3H/HeNHsd did not undergo epithelial-mesenchymal transition (EMT) and lower ratios of Lin28/let-7 contributed to AECII relatively higher differentiated status, leading to increased susceptibility to radiation stress and a failure in transdifferentiation in the absence of β-catenin. Reducing β-catenin expression and the ratios of Lin28/let-7 may be a promising strategy to prevent radiation fibrosis.

Aberrant cell state plasticity mediated by developmental reprogramming precedes colorectal cancer initiation

Cell state plasticity is carefully regulated in adult epithelia to prevent cancer. The aberrant expansion of the normally restricted capability for cell state plasticity in neoplasia is poorly defined. Using genetically engineered and carcinogen-induced mouse models of intestinal neoplasia, we observed that impaired differentiation is a conserved event preceding cancer development. Single-cell RNA sequencing (scRNA-seq) of premalignant lesions from mouse models and a patient with hereditary polyposis revealed that cancer initiates by adopting an aberrant transcriptional state characterized by regenerative activity, marked by Ly6a (Sca-1), and reactivation of fetal intestinal genes, including Tacstd2 (Trop2). Genetic inactivation of Sox9 prevented adenoma formation, obstructed the emergence of regenerative and fetal programs, and restored multilineage differentiation by scRNA-seq. Expanded chromatin accessibility at regeneration and fetal genes upon Apc inactivation was reduced by concomitant Sox9 suppression. These studies indicate that aberrant cell state plasticity mediated by unabated regenerative activity and developmental reprogramming precedes cancer development.

Patterns of NFkB activation resulting from damage, reactive microglia, cytokines, and growth factors in the mouse retina

Müller glia are a cellular source for neuronal regeneration in vertebrate retinas. However, the capacity for retinal regeneration varies widely across species. Understanding the mechanisms that regulate the reprogramming of Müller glia into progenitor cells is key to reversing the loss of vision that occurs with retinal diseases. In the mammalian retina, NFkB signaling promotes glial reactivity and represses the reprogramming of Müller glia into progenitor cells. Here we investigate different cytokines, growth factors, cell signaling pathways, and damage paradigms that influence NFkB-signaling in the mouse retina. We find that exogenous TNF and IL1β potently activate NFkB-signaling in Müller glia in undamaged retinas, and this activation is independent of microglia. By comparison, TLR1/2 agonist indirectly activates NFkB-signaling in Müller glia, and this activation depends on the presence of microglia as Tlr2 is predominantly expressed by microglia, but not other types of retinal cells. Exogenous FGF2 did not activate NFkB-signaling, whereas CNTF, Osteopontin, WNT4, or inhibition of GSK3β activated NFkB in Müller glia in the absence of neuronal damage. By comparison, dexamethasone, a glucocorticoid agonist, suppressed NFkB-signaling in Müller glia in damaged retinas, in addition to reducing numbers of dying cells and the accumulation of reactive microglia. Although NMDA-induced retinal damage activated NFkB in Müller glia, optic nerve crush had no effect on NFkB activation within the retina, whereas glial cells within the optic nerve were responsive. We conclude that the NFkB pathway is activated in retinal Müller glia in response to many different cell signaling pathways, and activation often depends on signals produced by reactive microglia.

Histopathological Changes In Lung Tissue Caused By Diabetes: A Review

Diabetes mellitus associated with oxidative stress and inflammation can affect many organs. While the effects of diabetes on many organs are well known and documented, its mechanisms of action on the lung are known far less. Hyperglycemia can lead to lung damage by increasing oxidative stresses and inflammation. Diabetes may be a trigger for pulmonary fibrosis, as studies suggest that there may be an important link between pulmonary fibrosis and diabetes. In this review, the histopathological changes caused by diabetes in the lung tissue were summarized. In addition, changes in the lung due to inflammation, oxidative stress and pulmonary fibrosis mechanisms were evaluated.

Targeting Doublecortin-Like Kinase 1 (DCLK1)-Regulated SARS-CoV-2 Pathogenesis in COVID-19

Host factors play critical roles in SARS-CoV-2 infection-associated pathology and the severity of COVID-19. In this study, we systematically analyzed the roles of SARS-CoV-2-induced host factors, doublecortin-like kinase 1 (DCLK1), and S100A9 in viral pathogenesis. In autopsied subjects with COVID-19 and pre-existing chronic liver disease, we observed high levels of DCLK1 and S100A9 expression and immunosuppressive (DCLK1⁺S100A9⁺CD206⁺) M2-like macrophages and N2-like neutrophils in lungs and livers. DCLK1 and S100A9 expression were rarely observed in normal controls, COVID-19-negative subjects with chronic lung disease, or COVID-19 subjects without chronic liver disease. In hospitalized patients with COVID-19, we detected 2 to 3-fold increased levels of circulating DCLK1⁺S100A9⁺ mononuclear cells that correlated with disease severity. We validated the SARS-CoV-2-dependent generation of these double-positive immune cells in coculture. SARS-CoV-2-induced DCLK1 expression correlated with the activation of β-catenin, a known regulator of the DCLK1 promoter. Gain and loss of function studies showed that DCLK1 kinase amplified live virus production and promoted cytokine, chemokine, and growth factor secretion by peripheral blood mononuclear cells. Inhibition of DCLK1 kinase blocked pro-inflammatory caspase-1/interleukin-1β signaling in infected cells. Treatment of SARS-CoV-2-infected cells with inhibitors of DCLK1 kinase and S100A9 normalized cytokine/chemokine profiles and attenuated DCLK1 expression and β-catenin activation. In conclusion, we report previously unidentified roles of DCLK1 in augmenting SARS-CoV-2 viremia, inflammatory cytokine expression, and dysregulation of immune cells involved in innate immunity. DCLK1 could be a potential therapeutic target for COVID-19, especially in patients with underlying comorbid diseases associated with DCLK1 expression.

IMPORTANCE High mortality in COVID-19 is associated with underlying comorbidities such as chronic liver diseases. Successful treatment of severe/critical COVID-19 remains challenging. Herein, we report a targetable host factor, DCLK1, that amplifies SARS-CoV-2 production, cytokine secretion, and inflammatory pathways via activation of β-catenin(p65)/DCLK1/S100A9/NF-κB signaling. Furthermore, we observed in the lung, liver, and blood an increased prevalence of immune cells coexpressing DCLK1 and S100A9, a myeloid-derived proinflammatory protein. These cells were associated with increased disease severity in COVID-19 patients. Finally, we used a novel small-molecule inhibitor of DCLK1 kinase (DCLK1-IN-1) and S100A9 inhibitor (tasquinimod) to decrease virus production in vitro and normalize hyperinflammatory responses known to contribute to disease severity in COVID-19.

Genetic and pharmacologic suppression of PPARγ enhances NELL-1-stimulated bone regeneration

Recent investigations into mechanisms behind the development of osteoporosis suggest that suppressing PPARγ-mediated adipogenesis can improve bone formation and bone mineral density. In this study, we investigated a co-treatment strategy to enhance bone formation by combining NELL-1, an osteogenic molecule that has been extensively studied for its potential use as a therapeutic for osteoporosis, with two methods of PPARγ suppression. First, we suppressed PPARγ genetically using lentiviral PPARγ-shRNA in immunocompromised mice for a proof of concept. Second, we used a PPARγ antagonist to suppress PPARγ pharmacologically in immunocompetent senile osteopenic mice for clinical transability. We found that the co-treatment strategy significantly increased bone formation, increased the proliferation stage cell population, decreased late apoptosis of primary mouse BMSCs, and increased osteogenic marker mRNA levels in comparison to the single agent treatment groups. The addition of PPARγ suppression to NELL-1 therapy enhanced NELL-1's effects on bone formation by upregulating anabolic processes without altering NELL-1's inhibitory effects on osteoclastic and adipogenic activities. Our findings suggest that combining PPARγ suppression with therapeutic NELL-1 may be a viable method that can be further developed as a novel strategy to reverse bone loss and decrease marrow adiposity in age-related osteoporosis.

A novel β-catenin/BCL9 complex inhibitor blocks oncogenic Wnt signaling and disrupts cholesterol homeostasis in colorectal cancer

Dysregulated Wnt/β-catenin signaling is implicated in the pathogenesis of many human cancers, including colorectal cancer (CRC), making it an attractive clinical target. With the aim of inhibiting oncogenic Wnt activity, we developed a high-throughput screening AlphaScreen assay to identify selective small-molecule inhibitors of the interaction between β-catenin and its coactivator BCL9. We identified a compound that consistently bound to β-catenin and specifically inhibited in vivo native β-catenin/BCL9 complex formation in CRC cell lines. This compound inhibited Wnt activity, down-regulated expression of the Wnt/β-catenin signature in gene expression studies, disrupted cholesterol homeostasis, and significantly reduced the proliferation of CRC cell lines and tumor growth in a xenograft mouse model of CRC. This study has therefore identified a specific small-molecule inhibitor of oncogenic Wnt signaling, which may have value as a probe for functional studies and has important implications for the development of novel therapies in patients with CRC.

Counteractive and cooperative actions of muscle β-catenin and CaV1.1 during early neuromuscular synapse formation

Activity-dependent calcium signals in developing muscle play a crucial role in neuromuscular junction (NMJ) formation. However, its downstream effectors and interactions with other regulators of pre- and postsynaptic differentiation are poorly understood. Here, we demonstrate that the skeletal muscle calcium channel Ca_V1.1 and β-catenin interact in various ways to control NMJ development. They differentially regulate nerve branching and presynaptic innervation patterns during the initial phase of NMJ formation. Conversely, they cooperate in regulating postsynaptic AChR clustering, synapse formation, and the proper organization of muscle fibers in mouse diaphragm. Ca_V1.1 does not directly regulate β-catenin expression but differentially controls the activity of its transcriptional co-regulators TCF/Lef and YAP. These findings suggest a crosstalk between Ca_V1.1 and β-catenin in the activity-dependent transcriptional regulation of genes involved in specific pre- and postsynaptic aspects of NMJ formation.

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Neuromuscular junction formation requires either muscle calcium or β-catenin signaling

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Complementary actions of Ca_V1.1 and β-catenin control presynaptic innervation patterns

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Parallel actions of Ca_V1.1 and β-catenin are crucial for postsynaptic AChR clustering

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Loss of Ca_V1.1 differentially regulates activity of β-catenin targets TCF/Lef and YAP

The Wnt Pathway: From Signaling Mechanisms to Synthetic Modulators

The Wnt pathway is central to a host of developmental and disease-related processes. The remarkable conservation of this intercellular signaling cascade throughout metazoan lineages indicates that it coevolved with multicellularity to regulate the generation and spatial arrangement of distinct cell types. By regulating cell fate specification, mitotic activity, and cell polarity, Wnt signaling orchestrates development and tissue homeostasis, and its dysregulation is implicated in developmental defects, cancer, and degenerative disorders. We review advances in our understanding of this key pathway, from Wnt protein production and secretion to relay of the signal in the cytoplasm of the receiving cell. We discuss the evolutionary history of this pathway as well as endogenous and synthetic modulators of its activity. Finally, we highlight remaining gaps in our knowledge of Wnt signal transduction and avenues for future research. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Glutamine promotes the generation of B10+ cells via the mTOR/GSK3 pathway

Alterations in cell metabolism can shift the differentiation of immune cells towards a regulatory or inflammatory phenotype, thus opening up new therapeutic opportunities for immune-related diseases. Indeed, growing knowledge on T cell metabolism has revealed differences in the metabolic programs of suppressive regulatory T cells (Tregs) as compared to inflammatory Th1 and Th17 cells. In addition to Tregs, IL-10-producing regulatory B cells are crucial for maintaining tolerance, inhibiting inflammation and autoimmunity. Yet, the metabolic networks regulating diverse B lymphocyte responses are not well known. Here, we show that glutaminase blockade decreased downstream mTOR activation and attenuated IL-10 secretion. Direct suppression of mTOR activity by rapamycin selectively impaired IL-10 production by B cells whereas secretion was restored upon GSK3 inhibition. Mechanistically, we found mTORC1 activation leads to GSK3 inhibition, identifying a key signalling pathway regulating IL-10 secretion by B lymphocytes. Thus, our results identify glutaminolysis and the mTOR/GSK3 signalling axis, as critical regulators of the generation of IL-10 producing B cells with regulatory functions. This article is protected by copyright. All rights reserved.

Regulation of Limbal Epithelial Stem Cells: Importance of the Niche

Limbal epithelial stem/progenitor cells (LSCs) reside in a niche that contains finely tuned balances of various signaling pathways including Wnt, Notch, BMP, Shh, YAP, and TGFβ. The activation or inhibition of these pathways is frequently dependent on the interactions of LSCs with various niche cell types and extracellular substrates. In addition to receiving molecular signals from growth factors, cytokines, and other soluble molecules, LSCs also respond to their surrounding physical structure via mechanotransduction, interaction with the ECM, and interactions with other cell types. Damage to LSCs or their niche leads to limbal stem cell deficiency (LSCD). The field of LSCD treatment would greatly benefit from an understanding of the molecular regulation of LSCs in vitro and in vivo. This review synthesizes current literature around the niche factors and signaling pathways that influence LSC function. Future development of LSCD therapies should consider all these niche factors to achieve improved long-term restoration of the LSC population.

Human limbal epithelial stem cell regulation, bioengineering and function

The corneal epithelium is continuously renewed by limbal stem/progenitor cells (LSCs), a cell population harbored in a highly regulated niche located at the limbus. Dysfunction and/or loss of LSCs and their niche cause limbal stem cell deficiency (LSCD), a disease that is marked by invasion of conjunctival epithelium into the cornea and results in failure of epithelial wound healing. Corneal opacity, pain, loss of vision, and blindness are the consequences of LSCD. Successful treatment of LSCD depends on accurate diagnosis and staging of the disease and requires restoration of functional LSCs and their niche. This review highlights the major advances in the identification of potential LSC biomarkers and components of the LSC niche, understanding of LSC regulation, methods and regulatory standards in bioengineering of LSCs, and diagnosis and staging of LSCD. Overall, this review presents key points for researchers and clinicians alike to consider in deepening the understanding of LSC biology and improving LSCD therapies.

Brick Strex: a robust device built of LEGO bricks for mechanical manipulation of cells

Cellular forces, mechanics and other physical factors are important co-regulators of normal cell and tissue physiology. These cues are often misregulated in diseases such as cancer, where altered tissue mechanics contribute to the disease progression. Furthermore, intercellular tensile and compressive force-related signaling is highlighted in collective cell behavior during development. However, the mechanistic understanding on the role of physical forces in regulation of cellular physiology, including gene expression and signaling, is still lacking. This is partly because studies on the molecular mechanisms of force transmission require easily controllable experimental designs. These approaches should enable both easy mechanical manipulation of cells and, importantly, readouts ranging from microscopy imaging to biochemical assays. To achieve a robust solution for mechanical manipulation of cells, we developed devices built of LEGO bricks allowing manual, motorized and/or cyclic cell stretching and compression studies. By using these devices, we show that [Formula: see text]-catenin responds differentially to epithelial monolayer stretching and lateral compression, either localizing more to the cell nuclei or cell-cell junctions, respectively. In addition, we show that epithelial compression drives cytoplasmic retention and phosphorylation of transcription coregulator YAP1. We provide a complete part listing and video assembly instructions, allowing other researchers to build and use the devices in cellular mechanics-related studies.

Trop-2 induces ADAM10-mediated cleavage of E-cadherin and drives EMT-less metastasis in colon cancer

We recently reported that activation of Trop-2 through its cleavage at R87-T88 by ADAM10 underlies Trop-2–driven progression of colon cancer. However, the mechanism of action and pathological impact of Trop-2 in metastatic diffusion remain unexplored. Through searches for molecular determinants of cancer metastasis, we identified TROP2 as unique in its up-regulation across independent colon cancer metastasis models. Overexpression of wild-type Trop-2 in KM12SM human colon cancer cells increased liver metastasis rates in vivo in immunosuppressed mice. Metastatic growth was further enhanced by a tail-less, activated ΔcytoTrop-2 mutant, indicating the Trop-2 tail as a pivotal inhibitory signaling element. In primary tumors and metastases, transcriptome analysis showed no down-regulation of CDH1 by transcription factors for epithelial-to-mesenchymal transition, thus suggesting that the pro-metastatic activity of Trop-2 is through alternative mechanisms. Trop-2 can tightly interact with ADAM10. Here, Trop-2 bound E-cadherin and stimulated ADAM10-mediated proteolytic cleavage of E-cadherin intracellular domain. This induced detachment of E-cadherin from β-actin, and loss of cell-cell adhesion, acquisition of invasive capability, and membrane-driven activation of β-catenin signaling, which were further enhanced by the ΔcytoTrop-2 mutant. This Trop-2/E-cadherin/β-catenin program led to anti-apoptotic signaling, increased cell migration, and enhanced cancer-cell survival. In patients with colon cancer, activation of this Trop-2–centered program led to significantly reduced relapse-free and overall survival, indicating a major impact on progression to metastatic disease. Recently, the anti-Trop-2 mAb Sacituzumab govitecan-hziy was shown to be active against metastatic breast cancer. Our findings define the key relevance of Trop-2 as a target in metastatic colon cancer.

Arrest of WNT/β-catenin signaling enables the transition from pluripotent to differentiated germ cells in mouse ovaries

Germ cells form the basis for sexual reproduction by producing gametes. In ovaries, primordial germ cells exit the cell cycle and the pluripotency-associated state, differentiate into oogonia, and initiate meiosis. Despite the importance of germ cell differentiation for sexual reproduction, signaling pathways regulating their fate remain largely unknown. Here, we show in mouse embryonic ovaries that germ cell-intrinsic β-catenin activity maintains pluripotency and that its repression is essential to allow differentiation and meiosis entry in a timely manner. Accordingly, in β-catenin loss-of-function and gain-of-function mouse models, the germ cells precociously enter meiosis or remain in the pluripotent state, respectively. We further show that interaction of β-catenin and the pluripotent-associated factor POU5F1 in the nucleus is associated with germ cell pluripotency. The exit of this complex from the nucleus correlates with germ cell differentiation, a process promoted by the up-regulation of Znrf3, a negative regulator of WNT/β-catenin signaling. Together, these data identify the molecular basis of the transition from primordial germ cells to oogonia and demonstrate that β-catenin is a central gatekeeper in ovarian differentiation and gametogenesis.

Allosteric Modulation of GSK-3β as a New Therapeutic Approach in Limb Girdle Muscular Dystrophy R1 Calpain 3-Related

Limb-girdle muscular dystrophy R1 calpain 3-related (LGMDR1) is an autosomal recessive muscular dystrophy produced by mutations in the CAPN3 gene. It is a rare disease and there is no cure or treatment for the disease while the pathophysiological mechanism by which the absence of calpain 3 provokes the dystrophy in muscles is not clear. However, key proteins implicated in Wnt and mTOR signaling pathways, which regulate muscle homeostasis, showed a considerable reduction in their expression and in their phosphorylation in LGMDR1 patients' muscles. Finally, the administration of tideglusib and VP0.7, ATP non-competitive inhibitors of glycogen synthase kinase 3β (GSK-3β), restore the expression and phosphorylation of these proteins in LGMDR1 cells, opening the possibility of their use as therapeutic options.

The B56α subunit of PP2A is necessary for mesenchymal stem cell commitment to adipocyte

Adipose tissue plays a major role in maintaining organismal metabolic equilibrium. Control over the fate decision from mesenchymal stem cells (MSCs) to adipocyte differentiation involves coordinated command of phosphorylation. Protein phosphatase 2A plays an important role in Wnt pathway and adipocyte development, yet how PP2A complexes actively respond to adipocyte differentiation signals and acquire specificity in the face of the promiscuous activity of its catalytic subunit remains unknown. Here, we report the PP2A phosphatase B subunit B56α is specifically induced during adipocyte differentiation and mediates PP2A to dephosphorylate GSK3β, thereby blocking Wnt activity and driving adipocyte differentiation. Using an inducible B56α knock-out mouse, we further demonstrate that B56α is essential for gonadal adipose tissue development in vivo and required for the fate decision of adipocytes over osteoblasts. Moreover, we show B56α expression is driven by the adipocyte transcription factor PPARγ thereby establishing a novel link between PPARγ signaling and Wnt blockade. Overall, our results reveal B56α is a necessary part of the machinery dictating the transition from pre-adipocyte to mature adipocyte and provide fundamental insights into how PP2A complex specifically and actively regulates unique signaling pathway in biology.

TAZ inhibits acinar cell differentiation but promotes immature ductal cell proliferation in adult mouse salivary glands

There are currently no treatments for salivary gland diseases, making it vital to understand signaling mechanisms operating in acinar and ductal cells so as to develop regenerative therapies. To date, little work has focused on elucidating the signaling cascades controlling the differentiation of these cell types in adult mammals. To analyze the function of the Hippo-TAZ/YAP1 pathway in adult mouse salivary glands, we generated adMOB1DKO mice in which both MOB1A and MOB1B were TAM-inducibly deleted when the animals were adults. Three weeks after TAM treatment, adMOB1DKO mice exhibited smaller submandibular glands (SMGs) than controls with a decreased number of acinar cells and an increased number of immature dysplastic ductal cells. The mutants suffered from reduced saliva production accompanied by mild inflammatory cell infiltration and fibrosis in SMGs, similar to the Sjogren's syndrome. MOB1-deficient acinar cells showed normal proliferation and apoptosis but decreased differentiation, leading to an increase in acinar/ductal bilineage progenitor cells. These changes were TAZ-dependent but YAP1-independent. Biochemically, MOB1-deficient salivary epithelial cells showed activation of the TAZ/YAP1 and β-catenin in ductal cells, but reduced SOX2 and SOX10 expression in acinar cells. Thus, Hippo-TAZ signaling is critical for proper ductal and acinar cell differentiation and function in adult mice.

MNS1 promotes hepatocarcinogenesis and metastasis via activating PI3K/AKT by translocating β-catenin and predicts poor prognosis

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is a fatal disease characterized by vast molecular heterogeneity. Although major advances in tumour genetics has led to the identification of new biomarkers, the prognosis of patients with HCC remains dismal.

METHODS

Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and western blot (WB) were used to evaluate meiosis-specific nuclear structural 1 (MNS1) expression in HCC cells. Immunohistochemistry staining was used to evaluate MNS1 expression in HCC tissues. Clinical significance of MNS1 was evaluated by Cox regression analysis. Transwell assays were conducted to assess cells migration ability. Cell counting kit-8 and colony formation assays were performed to detect cells proliferation ability. NOD/SCID/γc(null) (NOG) mice model was adopted to investigate functions of MNS1 in vivo.

RESULTS

The expression of MNS1, which is elevated in most HCC tissues, correlated with poor survival in HCC patients. Functional experiments revealed the oncogenic role of MNS1, which promotes HCC growth and metastasis through AKT-dependent modulation of β-catenin. β-Catenin expression was crucial for MNS1's oncogenic effects. MNS1 indirectly translocated β-catenin from the cytoplasm to the nucleus via the MNS1-GSK3β axis.

CONCLUSIONS

MNS1 promotes HCC growth and metastasis via activating PI3K/AKT signalling and may serve as an important prognostic biomarker as well as potential novel therapeutic target for HCC.

Captopril, a Renin-Angiotensin System Inhibitor, Attenuates Features of Tumor Invasion and Down-Regulates C-Myc Expression in a Mouse Model of Colorectal Cancer Liver Metastasis

Simple Summary

Approximately 25% of patients with colorectal cancer will present with or develop colorectal liver metastasis (CRLM). Surgical resection of CRLM offers these patients the best chance of a cure. However, liver resection and the subsequent regenerative response has been linked to tumor recurrence in the liver remnant. The Wnt/β-catenin pathway is one of many pathways common to both post-hepatectomy liver regeneration and tumorigenesis. Wnt signaling modulates multiple genes of the renin-angiotensin system (RAS), and Wnt inhibition can attenuate fibrotic responses and improve cancer outcomes via diverse mechanisms. In this study, we investigate the effects of captopril, a RAS inhibitor (RASi), on the Wnt/β-catenin pathway and phenotypic changes associated with tumor progression in the context of the regenerating liver. We show that RASi induced increased Wnt signaling whilst downregulating features of epithelial-to-mesenchymal transition (EMT). Furthermore, RASi induced significant down-regulation of Wnt target genes, c-myc and cyclin D1, indicating that expression of these genes can be down-regulated by RASi despite the accumulation of stabilized β-catenin.

Abstract

(1) Background: Recent clinical and experimental data suggests that the liver’s regenerative response following partial hepatectomy can stimulate tumor recurrence in the liver remnant. The Wnt/β-catenin pathway plays important roles in both colorectal cancer carcinogenesis and liver regeneration. Studies have shown that the Wnt/β-catenin pathway regulates multiple renin-angiotensin system (RAS) genes, whilst RAS inhibition (RASi) reduces tumor burden and progression. This study explores whether RASi attenuates features of tumor progression in the regenerating liver post-hepatectomy by modulating Wnt/β-catenin signaling. (2) Methods: Male CBA mice underwent CRLM induction, followed one week later by 70% partial hepatectomy. Mice were treated daily with captopril, a RASi, at 250 mg/kg/day or vehicle control from experimental Day 4. Tumor and liver samples were analyzed for RAS and Wnt signaling markers using qRT-PCR and immunohistochemistry. (3) Results: Treatment with captopril reduced the expression of down-stream Wnt target genes, including a significant reduction in both c-myc and cyclin-D1, despite activating Wnt signaling. This was a tumor-specific response that was not elicited in corresponding liver samples. (4) Conclusions: We report for the first time decreased c-myc expression in colorectal tumors following RASi treatment in vivo. Decreased c-myc expression was accompanied by an attenuated invasive phenotype, despite increased Wnt signaling.

Enhancing WNT Signaling Restores Cortical Neuronal Spine Maturation and Synaptogenesis in Tbr1 Mutants

Tbr1 is a high-confidence autism spectrum disorder (ASD) gene encoding a transcription factor with distinct pre- and postnatal functions. Postnatally, Tbr1 conditional knockout (CKO) mutants and constitutive heterozygotes have immature dendritic spines and reduced synaptic density. Tbr1 regulates expression of several genes that underlie synaptic defects, including a kinesin (Kif1a) and a WNT-signaling ligand (Wnt7b). Furthermore, Tbr1 mutant corticothalamic neurons have reduced thalamic axonal arborization. LiCl and a GSK3β inhibitor, two WNT-signaling agonists, robustly rescue the dendritic spines and the synaptic and axonal defects, suggesting that this could have relevance for therapeutic approaches in some forms of ASD.

Fazel Darbandi et al. demonstrate that TBR1 directly regulates transcriptional circuits in cortical layers 5 and 6, which promote dendritic spine and synaptic density. Enhancing WNT signaling rescues dendritic spine maturation and synaptogenesis defects in Tbr1 mutants. These results provide insights into mechanisms that underlie ASD pathophysiology.

Hearing Loss Caused by HCMV Infection through Regulating the Wnt and Notch Signaling Pathways

Hearing loss is one of the most prevalent sensory disabilities worldwide with huge social and economic burdens. The leading cause of sensorineural hearing loss (SNHL) in children is congenital cytomegalovirus (CMV) infection. Though the implementation of universal screening and early intervention such as antiviral or anti-inflammatory ameliorate the severity of CMV-associated diseases, direct and targeted therapeutics is still seriously lacking. The major hurdle for it is that the mechanism of CMV induced SNHL has not yet been well understood. In this review, we focus on the impact of CMV infection on the key players in inner ear development including the Wnt and Notch signaling pathways. Investigations on these interactions may gain new insights into viral pathogenesis and reveal novel targets for therapy.

Prenatal exposure to low doses of fungicides corrupts neurogenesis in neonates

Neurogenesis plays a crucial role during neurodevelopment and its dysfunction can lead to neurodevelopmental disorders. A recent hypothesis stipulates that exogenous factors could corrupt this process and predispose to neurodegenerative disorders later in life. The presence of pesticide residues in the diet represents a threat of which we have recently become aware of. Indeed, they could corrupt neurogenesis, especially during gestation, potentially leading to impaired neuronal and synaptic functions. Since the effects of this low-noise contamination have not yet been evaluated on the neurodevelopment, we investigated the impact of fungicide residues on WT mice exposed throughout gestation. Thus, mice were exposed to fungicides, cyprodinil, mepanipyrim and pyrimethanil, alone at 0.1 μg/L during gestation until P3. Besides, another group was exposed to a cocktail of these three fungicides (0.1 μg/L each) for the same time. Exposure was performed through drinking water at the regulatory limit dose of the European countries (0.1 μg/L). No general toxicity was observed in neonates on body and brain weight upon fungicide exposure. However, results showed that gestational exposure to fungicide residues substantially promoted an increase of neural precursor cells at P3. This corrupted neurogenesis was linked to increased levels of β-catenin, likely through the crosstalk of the PI3K/Akt and Wnt/β-catenin pathways, both involved in cell proliferation. Fungicide exposure also altered protein expression of PSD95 and NMDA receptors in P3 neonates, two targets of the β-catenin signaling pathway. Adult neural stem cell extractions from mice treated with the fungicide cocktail, showed an increase proliferation and differentiation combined with a reduction of their migration properties. In addition, in vitro studies on hippocampal primary cell cultures treated with various concentrations of fungicides showed neurotoxic effects. To conclude, corruption of neurogenesis by this chemical assault could be a fertile ground for the development of neurological diseases later in life.

Exploring the structural significance of molecular switch mechanism alias motif phosphorylation in Wnt/β-catenin and their crucial role in triple-negative breast cancer

β-Catenin, a key transcriptional factor involved in the canonical Wnt signaling pathway, is regulated by a cascade of phosphorylations and plays a major role in the progression of triple-negative breast cancer (TNBC). However, the phosphorylation induced conformational changes in a β-Catenin is still poorly understood. Hence, we adopted a conventional molecular dynamics approach to study phosphorylations present in a sequence motif Ser ^552 675 and Tyr⁶⁷⁰ of the β-Catenin domain and analyzed in terms of structural transitions, bond formation, and folding-misfolding conformations. Our results unveil the β-Catenin linear motif 549-555 (RRTSMGG) of armadillo repeats domain prefers order to disorder state. In contrast, helix C associated with 670-678 (YKKRLSVEL) motif prefers disorder to order upon phosphorylation of Ser ^552 675 and Tyr⁶⁷⁰. In addition, the crucial secondary structural transition from α-helix to coil induced by phospho Ser⁵⁵² and phospho Tyr⁶⁷⁰ of β-Catenin ARM domain connecting helix C modifies conformational diversity and binding affinities of the complex interaction in functional regulation significantly. Moreover, the post phosphorylation disrupted the hydrogen bond interactions (Ser552-Arg549, Arg550-Asp546 and Ser675-Lys672) and abolished the residual alliance with hydrophobic interactions (Tyr670-Leu674) that easily interrupt in secondary structure packing as well as folding conformations connecting ARM and helix C (R10, 12 & R1C) compared to unphosphorylation. Our integrated computational analysis may help in shedding light on understanding the induced folding and unfolding pattern due to motif phosphorylations. Overall, our results provide an atomistic structural description of the way phosphorylation facilitates conformational and dynamic changes in β-Catenin, a fundamental molecular switch mechanism in triple-negative breast cancer pathogenesis.

Nischarin downregulation attenuates cell injury induced by oxidative stress via Wnt signaling

Nischarin (NISCH) is a key protein functioning as a molecular scaffold and thereby hosting interactions with several protein partners. Here, we aimed to investigate whether NISCH downregulation could protect rat pheochromocytoma (PC12) cells against oxidative stress-induced injury using a model of cell injury induced by hydrogen peroxide (H2O2). Cell viability was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis rate was evaluated using flow cytometry. The expressions of apoptosis-related proteins Bax, Bcl-2, caspase-3 and NISCH were examined via Western blot analysis and immunofluorescence staining analyses. The expressions of NISCH, glycogen synthase kinase-3β (GSK-3β) and T-cell factor-1 (TCF-1) were examined using Western blot analysis. The results showed that incubation of H2O2 for 48 h significantly decreased the cell viability, increased the cell apoptosis rate and the NISCH expression in PC12 cells, whereas NISCH downregulation blocked the effects of H2O2 on cells. In addition, the expression of Bcl-2 was significantly reduced, and the expression of Bax and caspase-3 were significantly increased by H2O2 treatment. However, these effects were partially inhibited by the downregulation of NISCH. Furthermore, H2O2 significantly weakened the transduction of Wnt signaling, including the increases of GSK-3β and TCF-1 expressions and the decrease of β-catenin expression, while NISCH downregulation attenuated the effect of H2O2 on Wnt signaling. Moreover, inhibition of the Wnt pathway further decreased the cell viability and promoted the cell apoptosis induced by H2O2 in PC12 cells. Our results suggest that NISCH downregulation may protect cells against oxidative stress-induced injury through regulating the transduction of Wnt signaling.

Effect of Klotho protein during porcine oocyte maturation via Wnt signaling

Klotho protein is well-known as an anti-aging agent, however, several studies have suggested that Klotho protein also increases antioxidant activity and the reproductive system, as Klotho protein is closely associated with Wnt signaling. The objective of our study was to investigate the enhancement of porcine oocyte in vitro maturation via the Klotho protein-Wnt signaling pathway. Following immunohistochemistry and ELISA, we treated cells with Klotho protein during in vitro maturation. Lithium Chloride, a specific activator of Wnt signaling, was subsequently co-administered with Klotho protein. Mature oocytes subjected to treatments were used for the analysis of embryonic development, qRT-PCR, and immunocytochemistry. Treatment with 5pg/ml Klotho protein significantly increased cumulus cell expansion, blastocyst formation rates, and the total cell number of blastocysts. During cotreatment with 5mM Lithium Chloride and 5pg/ml Klotho protein, blastocyst formation rates were the highest in Klotho protein-treated oocytes and the lowest in Lithium Chloride-treated oocytes. Expression levels of Wnt signaling-related transcripts and proteins were significantly impacted by Klotho protein and Lithium Chloride. Moreover, cellular ATP levels and antioxidant activities were enhanced by Klotho protein treatment. These findings suggest a significant involvement of the Klotho protein-Wnt signaling mechanism in porcine oocyte maturation.

Pancreatic Ductal Adenocarcinoma (PDAC) Organoids: The Shining Light at the End of the Tunnel for Drug Response Prediction and Personalized Medicine

Simple Summary

Pancreatic ductal adenocarcinoma (PDAC) causes massive medical problems because of late diagnosis and limited responsiveness to standard chemotherapeutic treatments. This makes PDAC one of the major causes of death by cancer. To address this problem, novel tools for early diagnosis and therapy are needed. The recent development of PDAC organoids, which represent micro-scale mini-tumors, offers promising new options for personalized drug-testing based on primary PDAC patient material. This overview article summarizes and discusses the current state-of-the-art in exploiting the organoid technology to improve clinical management of PDAC.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) represents 90% of pancreatic malignancies. In contrast to many other tumor entities, the prognosis of PDAC has not significantly improved during the past thirty years. Patients are often diagnosed too late, leading to an overall five-year survival rate below 10%. More dramatically, PDAC cases are on the rise and it is expected to become the second leading cause of death by cancer in western countries by 2030. Currently, the use of gemcitabine/nab-paclitaxel or FOLFIRINOX remains the standard chemotherapy treatment but still with limited efficiency. There is an urgent need for the development of early diagnostic and therapeutic tools. To this point, in the past 5 years, organoid technology has emerged as a revolution in the field of PDAC personalized medicine. Here, we are reviewing and discussing the current technical and scientific knowledge on PDAC organoids, their future perspectives, and how they can represent a game change in the fight against PDAC by improving both diagnosis and treatment options.

Aquaporin 1 promotes sensitivity of anthracycline chemotherapy in breast cancer by inhibiting β-catenin degradation to enhance TopoIIα activity

Anthracyclines are a class of conventional and commonly used frontline chemotherapy drugs to treat breast cancer. However, the anthracycline-based regimens can only reduce breast cancer mortality by 20–30%. Furthermore, there is no appropriate biomarker for predicting responses to this kind of chemotherapy currently. Here we report our findings that may fill this gap by showing the AQP1 (Aquaporin1) protein as a potential response predictor in the anthracycline chemotherapy. We showed that breast cancer patients with a high level of AQP1 expression who underwent the anthracycline treatment had a better clinical outcome relative to those with a low level of AQP1 expression. In the exploration of the underlying mechanisms, we found that the AQP1 and glycogen synthase kinase-3β (GSK3β) competitively interacted with the 12 armadillo repeats of β-catenin, followed by the inhibition of the β-catenin degradation that led to β-catenin’s accumulation in the cytoplasm and nuclear translocation. The nuclear β-catenin interacted with TopoIIα and enhanced TopoIIα’s activity, which resulted in a high sensitivity of breast cancer cells to anthracyclines. We also found, the miR-320a-3p can attenuate the anthracycline’s chemosensitivity by inhibiting the AQP1 expression. Taken together, our findings suggest the efficacy of AQP1 as a response predictor in the anthracycline chemotherapy. The application of our study includes, but is not limited to, facilitating screening of the most appropriate breast cancer patients (who have a high AQP1 expression) for better anthracycline chemotherapy and improved prognosis purposes.

Glycogen synthase kinase-3β promotes radiation-induced lung fibrosis by regulating β-catenin/lin28 signaling network to determine type II alveolar stem cell transdifferentiation state

The role of type II alveolar epithelial stem cells (AEC II) for alveolar repair in radiation-induced lung fibrosis (RILF) remains largely unknown, mainly because of AEC II phenotype's spontaneous change in vitro. Cell differentiation status is determined by Lin28 and let-7 miRNAs in see-saw-pattern. Lin28, a repressor of let-7 and a stem cell marker, is activated by β-catenin. The expression of β-catenin is regulated by GSK-3β/TGF-β1 signaling. To understand the true role of AEC II in RILF, we freshly isolated primary AEC II directly from thoracically irradiated lungs. We then explored the expressions of cell phenotype markers and differentiation regulators in these isolated AEC II to analyze the correlation between GSK-3β/TGF-β1/β-catenin signaling pathway, lin28/let-7 balance, and AEC II phenotypes at different injury phases following irradiation. Results showed that isolated single primary cells displayed AEC II ultrastructural features and proSP-C positive. The gene expressions of prosp-c (an AEC II biomarker) and hopx (an AEC I marker) significantly increased in isolated AEC II during injury repair phase (P < .001 and P < .05) but decreased at end-stage of injury, while mesenchymal markers increased in both isolated AEC II and irradiated lungs. mRNA levels of gsk-3β, tgf-β1, and β-catenin increased in all irradiated AEC II, but more pronounced in the second half of injury phase (P < .05-P < .001). Similarly, the expression of lin28 was also significantly elevated in isolated AEC II at the late phase (P < .05-P < .001). Four let-7 miRNAs were significantly upregulated in all irradiated AEC II groups (P < .05-P < .001). The time-dependent and highly consistent uptrends for four lin28/let-7 ratios in sorted AEC II contrasted to downtrends in irradiated lungs. In conclusion, RILF occurred when GSK-3β/TGF-β1 signaling increased β-catenin levels, which led to the augmentation of AEC II population by elevated lin28/let-7 ratio and the transcription of profibrotic cytokines and factors, thereby inducing AEC II to undergo transdifferentiation into mesenchymal cells.

LGRs in Skeletal Tissues: An Emerging Role for Wnt-Associated Adult Stem Cell Markers in Bone

Leucine‐rich repeat‐containing G protein‐coupled receptors (LGRs) are adult stem cell markers that have been described across various stem cell niches, and expression of LGRs and their corresponding ligands (R‐spondins) has now been reported in multiple bone‐specific cell types. The skeleton harbors elusive somatic stem cell populations that are exceedingly compartment‐specific and under tight regulation from various signaling pathways. Skeletal progenitors give rise to multiple tissues during development and during regenerative processes of bone, requiring postnatal endochondral and intramembranous ossification. The relevance of LGRs and the LGR/R‐spondin ligand interaction in bone and tooth biology is becoming increasingly appreciated. LGRs may define specific stem cell and progenitor populations and their behavior during both development and regeneration, and their role as Wnt‐associated receptors with specific ligands poses these proteins as unique therapeutic targets via potential R‐spondin agonism. This review seeks to outline the current literature on LGRs in the context of bone and its associated tissues, and points to key future directions for studying the functional role of LGRs and ligands in skeletal biology. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Doublecortin-like kinase 1 promotes hepatocyte clonogenicity and oncogenic programming via non-canonical β-catenin-dependent mechanism

Chronic liver injury is a risk factor for cirrhosis and hepatocellular carcinoma (HCC). The molecular mechanisms that regulate the decision between normal injury repair and neoplastic initiation are unclear. Doublecortin-like kinase 1 (DCLK1), a tumor stem cell marker, is induced during cirrhosis and HCC. Here, we demonstrate that DCLK1-overexpressing primary human hepatocytes formed spheroids in suspension cultures. Spheroids derived from DCLK1-overexpressing hepatoma cells showed high level expression of active β-catenin, α-fetoprotein, and SOX9, suggesting that DCLK1 overexpression induces clonogenicity and dedifferentiated phenotypes in hepatoma cells. DCLK1 overexpression in hepatoma cells also increased phosphorylation of GSK-3β at Ser⁹. This was associated with an induction of a 48-kDa active β-catenin with a preserved hypophosphorylated N-terminus that interacted with nuclear TCF-4 resulting in luciferase reporter activity and cyclin D1 expression. DCLK1 downregulation inhibited 48-kDa β-catenin expression. The proteasome inhibitor bortezomib did not block the 48-kDa β-catenin, instead, caused a threefold accumulation, suggesting a proteasome-independent mechanism. Liver tissues from patients with cirrhosis and HCC revealed epithelial co-staining of DCLK1 and active β-catenin, and cleaved E-cadherin. Repopulated DCLK1-overexpressing primary human hepatocytes in humanized FRG mouse livers demonstrated active β-catenin. In conclusion, DCLK1 regulates oncogenic signaling and clonogenicity of hepatocytes by a novel non-canonical/atypical β-catenin-dependent mechanism.

β-catenin-mediated Wnt signal transduction proceeds through an endocytosis-independent mechanism

The Wnt pathway is a key intercellular signaling cascade that regulates development, tissue homeostasis, and regeneration. However, gaps remain in our understanding of the molecular events that take place between ligand-receptor binding and target gene transcription. We used a novel tool for quantitative, real-time assessment of endogenous pathway activation, measured in single cells, to answer an unresolved question in the field-whether receptor endocytosis is required for Wnt signal transduction. We combined knockdown or knockout of essential components of clathrin-mediated endocytosis with quantitative assessment of Wnt signal transduction in mouse embryonic stem cells (mESCs). Disruption of clathrin-mediated endocytosis did not affect accumulation and nuclear translocation of β-catenin, as measured by single-cell live imaging of endogenous β-catenin, and subsequent target gene transcription. Disruption of another receptor endocytosis pathway, caveolin-mediated endocytosis, did not affect Wnt pathway activation in mESCs. Additional results in multiple cell lines support that endocytosis is not a requirement for Wnt signal transduction. We show that off-target effects of a drug used to inhibit endocytosis may be one source of the discrepancy among reports on the role of endocytosis in Wnt signaling.

Expression of E-cadherin and β-catenin in Laryngeal and Hypopharyngeal Squamous Cell Carcinomas

INTRODUCTION AND OBJECTIVES

Dysfunction of the E-cadherin/catenin complex is directly related to carcinogenesis and metastases development. The aim of this paper is to investigate the prognostic significance of E-cadherin and β-catenin expression in surgically treated laryngeal and hypopharyngeal squamous cell carcinomas.

MATERIAL AND METHODS

Tumour tissue samples were obtained from 133 consecutive patients with squamous cell carcinomas of the head and neck: 68 of the larynx and 65 hypopharyngeal carcinomas, who underwent surgical treatment in our hospital between 2000 and 2005. E-cadherin and β-catenin expression was analysed by immunohistochemistry, quantifying the percentage of stained cells and the intensity of staining.

RESULTS

E-cadherin and β-catenin expression was evaluable in 59 laryngeal carcinomas and in 58 cases of hypopharyngeal carcinomas. In the laryngeal tumours, a significant association was found between the low expression of membrane β-catenin with T4 tumours and tumour recurrence. In the hypopharynx there was a significant association between positive expression of nuclear β-catenin and poor histological differentiation (P=.02). In the multivariate analysis, only the presence of lymph node metastases was an independent predictive factor of decreased disease-specific survival in laryngeal squamous cell carcinomas.

CONCLUSIONS

The expression of E-cadherin and β-catenin does not show prognostic significance in laryngeal and hypopharyngeal squamous cell carcinomas over the TNM classification.

The Hepatitis B Virus Pre-Core Protein p22 Activates Wnt Signaling

An emerging theme for Wnt-addicted cancers is that the pathway is regulated at multiple steps via various mechanisms. Infection with hepatitis B virus (HBV) is a major risk factor for liver cancer, as is deregulated Wnt signaling, however, the interaction between these two causes is poorly understood. To investigate this interaction, we screened the effect of the various HBV proteins for their effect on Wnt/β-catenin signaling and identified the pre-core protein p22 as a novel and potent activator of TCF/β-catenin transcription. The effect of p22 on TCF/β-catenin transcription was dose dependent and inhibited by dominant-negative TCF4. HBV p22 activated synthetic and native Wnt target gene promoter reporters, and TCF/β-catenin target gene expression in vivo. Importantly, HBV p22 activated Wnt signaling on its own and in addition to Wnt or β-catenin induced Wnt signaling. Furthermore, HBV p22 elevated TCF/β-catenin transcription above constitutive activation in colon cancer cells due to mutations in downstream genes of the Wnt pathway, namely APC and CTNNB1. Collectively, our data identifies a previously unappreciated role for the HBV pre-core protein p22 in elevating Wnt signaling. Understanding the molecular mechanisms of p22 activity will provide insight into how Wnt signaling is fine-tuned in cancer.

Eugenol restricts Cancer Stem Cell population by degradation of β-catenin via N-terminal Ser37 phosphorylation-an in vivo and in vitro experimental evaluation

Eugenol a phenylpropanoid, predominantly found in clove is a very common spice in daily cuisine. It already reported to have anti-breast cancer activity. In this study, the effect of eugenol on CSC (Cancer Stem Cell) markers and its main regulator β-catenin both in vivo Ehrlich Ascites Carcinoma (EAC) cell line and in vitro MCF-7 cell line was investigated with that of the untreated group. The therapeutic doses were found to significantly induce apoptosis leaving normal mice and cells unaffected. The in-depth analysis revealed the downregulation of β-catenin thereby facilitating its degradation by N-terminal phosphorylation of Ser37 residue. Significant downregulation of various CSC markers was also observed in vivo after eugenol treatment those are regulated by the intracellular status of β-catenin. These findings were validated by the effect of eugenol on the formation of the secondary sphere in vitro. Notable downregulation of the enriched stemness of secondary mammosphere was detected by the significantly decreased percentage of CD44⁺/CD24^-/low population after eugenol treatment along with their distorted morphology and smaller the number of spheres. The underlying mechanism revealed significant downregulation of β-catenin and the set of CSC markers along with their reduced mRNA expression in secondary sphere culture. Therefore, it can be concluded from the study that eugenol exerts its chemotherapeutic potential by impeding β-catenin nuclear translocation thereby promoting its cytoplasmic degradation as a result stemness is being suppressed potentially even if in the enriched state. Therefore the study contributes to reduce the cancer-induced complications associated with the CSC population. This will ultimately confer the longer and improved patient's life.

Interleukin-1 Signaling Mediates Obesity-Promoted Elevations in Inflammatory Cytokines, Wnt Activation, and Epithelial Proliferation in the Mouse Colon

Obesity is a prominent risk factor for colorectal cancer (CRC). One mechanism by which obesity promotes the development of CRC is by generating a chronic, low-grade state of colonic inflammation. Interleukin-1β (IL-1β), a proinflammatory cytokine often elevated in obesity, is known to activate several procarcinogenic signaling pathways that are implicated in colonic carcinogenesis. We therefore sought to define the role of IL-1β in mediating some of the early biochemical and molecular events leading up to obesity-promoted CRC. Twenty-five wild-type (WT) C57BL/6J mice and 24 lacking a functional IL-1 receptor (IL1R^-/-) were each randomized to either low-fat or high-fat diets, resulting in lean and obese mice. Compared to WT lean controls, WT obese mice displayed 30%-80% greater concentrations of IL-1β and tumor necrosis factor-α (TNF-α) in the colonic mucosa (IL-1β: P = 0.04; TNF-α: P < 0.05), activation of the Wnt signaling cascade [evidenced by a 2-fold increase in colonic crypt cells displaying intranuclear β-catenin (P < 0.03)], and a significant expansion of the proliferation zone of the colonic crypt (P < 0.04). These obesity-induced alterations in colonic cytokines, Wnt signaling, and proliferation were absent in the obese IL1R^-/- mice. In the absence of IL-1 signaling, obesity-induced elevations of colonic IL-1β, TNF-α, Wnt activation, and enhanced epithelial proliferation no longer occur. These observations underscore the important mechanistic roles that IL-1 signaling appears to play in mediating the procancerous effects of obesity in the colon, thereby identifying a potential target for future strategies aimed at chemoprevention.

Stabilization of Intrinsically Disordered DKK2 Protein by Fusion to RNA-Binding Domain

Intrinsic disorders are a common feature of hub proteins in eukaryotic interactomes controlling the signaling pathways. The intrinsically disordered proteins (IDPs) are prone to misfolding, and maintaining their functional stability remains a major challenge in validating their therapeutic potentials. Considering that IDPs are highly enriched in RNA-binding proteins (RBPs), here we reasoned and confirmed that IDPs could be stabilized by fusion to RBPs. Dickkopf2 (DKK2), Wnt antagonist and a prototype IDP, was fused with lysyl-tRNA synthetase (LysRS), with or without the fragment crystallizable (Fc) domain of an immunoglobulin and expressed predominantly as a soluble form from a bacterial host. The functional competence was confirmed by in vitro Wnt signaling reporter and tube formation in human umbilical vein endothelial cells (HUVECs) and in vivo Matrigel plug assay. The removal of LysRS by site-specific protease cleavage prompted the insoluble aggregation, confirming that the linkage to RBP chaperones the functional competence of IDPs. While addressing to DKK2 as a key modulator for cancer and ischemic vascular diseases, our results suggest the use of RBPs as stabilizers of disordered proteinaceous materials for acquiring and maintaining the structural stability and functional competence, which would impact the druggability of a variety of IDPs from human proteome.

Nuclear localization of β-catenin and expression of target genes are associated with increased Wnt secretion in oral dysplasia

OBJECTIVES

To evaluate the localization of β-catenin in oral dysplastic cells, the expression of target genes upregulated in oral dysplasia, and the role of Wnt ligands in these events.

MATERIALS AND METHODS

Subcellular localization of total and non-phosphorylated (transcriptionally active) β-catenin was evaluated by immunofluorescence and biochemical fractionation in dysplastic oral keratinocytes (DOK), non-dysplastic oral keratinocytes (OKF6), oral squamous carcinoma cells (CAL27) and primary oral keratinocytes. Tcf/Lef-dependent transcription was measured by luciferase reporter assays. Expression of target genes, survivin and cyclin D1, was evaluated by RT-qPCR and Western blotting. Wnt secretion was inhibited with the inhibitor of porcupine, C59. Wnt3a and β-catenin were evaluated in biopsies by tissue immunofluorescence.

RESULTS

Immunofluorescence and fractionation experiments showed augmented nuclear β-catenin (total and transcriptionally active) in DOK, when compared with OKF6 and CAL27 cells. Intriguingly, conditioned medium from DOK promoted nuclear accumulation of β-catenin and Tcf/Lef-dependent transcription in OKF6 and primary oral keratinocytes, suggesting the participation of secreted factors. Treatment of DOK with C59 decreased Wnt3a secretion, nuclear β-catenin and the expression of survivin and cyclin D1 at both mRNA and protein levels. Accordingly, DOK secreted higher Wnt3a levels than OKF6, and inhibition of Wnt3a secretion prevented DOK-induced Tcf/Lef-dependent transcription in OKF6. These observations were confirmed in clinical samples, since tissue immunofluorescence analysis showed simultaneous expression of Wnt3a and nuclear β-catenin in oral dysplasia, but not in healthy mucosa biopsies.

CONCLUSION

These data indicate that secretion of Wnt ligands is critical for β-catenin nuclear localization and expression of target genes in oral dysplasia.

Bacillus/Trapa japonica Fruit Extract Ferment Filtrate enhances human hair follicle dermal papilla cell proliferation via the Akt/ERK/GSK-3β signaling pathway

BACKGROUND

Despite advances in medical treatments, the proportion of the population suffering from alopecia is increasing, creating a need for new treatments to control hair loss and prevent balding. Treatments based on plant-derived compounds could potentially prevent hair loss. Human hair follicle dermal papilla (HDP) cells, a type of specialized fibroblast in the hair bulb, play an essential role in controlling hair growth and in conditions such as androgenic alopecia. We examined the effect of Bacillus/Trapa japonica fruit ferment filtrate extracts (TJFs) on HDP cells to determine whether activation of the Akt/ERK/GSK-3β signaling pathway improved HDP cell proliferation.

METHODS

We prepared TJFs using various methods. The extract properties were analyzed using WST-1, Lowry, and cell migration assays as well as immunofluorescence staining. We also determined the cell cycle stage and performed western blotting and an in ovo chick chorioallantoic membrane assay. Last, we constructed an organotypic three-dimensional cell culture model for immunohistochemical use.

RESULTS

Our study confirmed that the TJFs contained numerous peptides and five unknown fractions. The TJFs stimulated HDP cell proliferation and migration via the Akt/ERK/GSK-3β signaling pathway. To verify that the Akt/ERK/GSK-3β pathway affected HDP cell proliferation, we treated HDP cells with LY294002 (an Akt inhibitor), BIO (a GSK-3β inhibitor), and PD98059 (an ERK inhibitor). The TJFs also induced cell cycle progression, inhibited type І 5α-reductase, decreased apoptosis, and enhanced angiogenesis (vascular expansion). In addition to these signaling pathways, proteins including insulin-like growth factor-1 and keratinocyte growth factor, stimulating hair growth, were detected in the three-dimensional cell culture model.

CONCLUSIONS

Our results confirmed that TJFs enhance HDP cell proliferation via the Akt/ERK/GSK-3β signaling pathway, suggesting a potential treatment for alopecia.

CGK062, a small chemical molecule, inhibits cancer upregulated gene 2‑induced oncogenesis through NEK2 and β‑catenin

The mechanisms through which cancer‑upregulated gene 2 (CUG2), a novel oncogene, affects Wnt/β‑catenin signaling, essential for tumorigenesis, are unclear. In this study, we aimed to elucidate some of these mechanisms in A549 lung cancer cells. Under the overexpression of CUG2, the protein levels and activity of β‑catenin were evaluated by western blot analysis and luciferase assay. To examine a biological consequence of β‑catenin under CUG2 overexpression, cell migration, invasion and sphere formation assay were performed. The upregulation of β‑catenin induced by CUG2 overexpression was also accessed by xenotransplantation in mice. We first found that CUG2 overexpression increased β‑catenin expression and activity. The suppression of β‑catenin decreased cancer stem cell (CSC)‑like phenotypes, indicating that β‑catenin is involved in CUG2‑mediated CSC‑like phenotypes. Notably, CUG2 overexpression increased the phosphorylation of β‑catenin at Ser33/Ser37, which is known to recruit E3 ligase for β‑catenin degradation. Moreover, CUG2 interacted with and enhanced the expression and kinase activity of never in mitosis gene A‑related kinase 2 (NEK2). Recombinant NEK2 phosphorylated β‑catenin at Ser33/Ser37, while NEK2 knockdown decreased the phosphorylation of β‑catenin, suggesting that NEK2 is involved in the phosphorylation of β‑catenin at Ser33/Ser37. Treatment with CGK062, a small chemical molecule, which promotes the phosphorylation of β‑catenin at Ser33/Ser37 through protein kinase C (PKC)α to induce its degradation, reduced β‑catenin levels and inhibited the CUG2‑induced features of malignant tumors, including increased cell migration, invasion and sphere formation. Furthermore, CGK062 treatment suppressed CUG2‑mediated tumor formation in nude mice. Taken together, the findings of this study suggest that CUG2 enhances the phosphorylation of β‑catenin at Ser33/Ser37 by activating NEK2, thus stabilizing β‑catenin. CGK062 may thus have potential for use as a therapeutic drug against CUG2‑overexpressing lung cancer cells.

An immunohistochemical approach to detect oncogenic CTNNB1 mutations in primary neoplastic tissues

The Wnt/β-catenin signaling pathway is dysregulated in different types of neoplasms including colorectal cancer (CRC). Aberrant activation of this signaling pathway is a key early event in the development of colorectal neoplasms, and is mainly caused by loss of function mutations in Adenomatous Polyposis Coli (APC), and less frequently by β-catenin stabilization mutations via missense or interstitial genomic deletions in CTNNB1. In this study, we have defined an immunohistochemical algorithm to dissect Wnt pathway alterations in formalin-fixed and paraffin-embedded neoplastic tissues. Basically, consecutive sections of tumor specimens were stained by immunohistochemistry with two different monoclonal antibodies against β-catenin: one (anti-active β-catenin antibody) recognizes hypo-phosphorylated β-catenin and the other recognizes the total pool of β-catenin. We validated the strategy in the HCT116 CRC cell line which has an in-frame deletion of β-catenin serine 45, and then studied human tumor microarrays containing colon adenomas, CRCs, solid pseudopapillary neoplasms of the pancreas as well as the whole tissue sections of CRCs, desmoid fibromatosis, and pilomatrixoma of the skin. In some tumors, we found strong β-catenin cytoplasmic and/or nuclear staining with the total β-catenin antibody but no staining with the anti-active β-catenin antibody. This was inferred to be an altered/mutant β-catenin staining pattern. All six colon adenomas of the 126 total adenomas studied for the altered/mutant β-catenin staining pattern had presumptively pathogenic point mutations or deletions in CTNNB1. Four of 10 CRCs with the alterated/mutant β-catenin staining pattern studied in depth, from 181 total CRCs from tissue microarray, had pathogenic CTNNB1 mutations. The frequencies of CTNNB1 alterations in non-colonic tumors with altered/mutant β-catenin staining ranged between 46 and 100%. Our results demonstrate that the immunohistochemical approach described here can detect oncogenic forms of β-catenin in primary tissue samples and can also highlight other tumors with presumptive novel defects activating the Wnt/β-catenin pathway.

Pathogenic Feed-Forward Mechanisms in Alzheimer's and Parkinson's Disease Converge on GSK-3

Alzheimer's disease (AD) and Parkinson's disease (PD) share many commonalities ranging from signaling deficits such as altered cholinergic activity, neurotrophin and insulin signaling to cell stress cascades that result in proteinopathy, mitochondrial dysfunction and neuronal cell death. These pathological processes are not unidirectional, but are intertwined, resulting in a series of feed-forward loops that worsen symptoms and advance disease progression. At the center of these loops is glycogen synthase kinase-3 (GSK-3), a keystone protein involved in many of the multidirectional biological processes that contribute to AD and PD neuropathology. Here, a unified overview of the involvement of GSK-3 in the major processes involved in these diseases will be presented. The mechanisms by which these processes are linked will be discussed and the feed-forward pathways identified. In this regard, this review will put forth the notion that combination therapy, targeting these multiple facets of AD or PD neuropathology is a necessary next step in the search for effective therapies.