Wnt/β-catenin signaling: Structure, assembly and endocytosis of the signalosome

Regulation of YAP and Wnt signaling by the endosomal protein MAMDC4

Maintenance of the intestinal epithelium requires constant self-renewal and regeneration. Tight regulation of proliferation and differentiation of intestinal stem cells within the crypt region is critical to maintaining homeostasis. The transcriptional co-factors β-catenin and YAP are required for proliferation during normal homeostasis as well as intestinal regeneration after injury: aberrant signaling activity results in over proliferation and tumorigenesis. Although both YAP and β-catenin activity are controlled along canonical pathways, it is becoming increasingly clear that non-canonical regulation of these transcriptional regulators plays a role in fine tuning their activity. We have shown previously that MAMDC4 (Endotubin, AEGP), an integral membrane protein present in endosomes, regulates both YAP and β-catenin activity in kidney epithelial cells and in the developing intestinal epithelium. Here we show that MAMDC4 interacts with members of the signalosome and mediates cross-talk between YAP and β-catenin. Interestingly, this cross-talk occurs through a non-canonical pathway involving interactions between AMOT:YAP and AMOT:β-catenin.

Vertical Strength Transfer Phenomenon Between Upper Body and Lower Body Exercise: Systematic Scoping Review

BACKGROUND

There are a myriad of exercise variations in which upper body (UB) and lower body (LB) exercises have been intermittently used. However, it is still unclear how training of one body region (e.g. LB) affects adaptations in distant body areas (e.g. UB), and how different UB and LB exercise configurations could help facilitate physiological adaptations of either region; both referred to in this review as vertical strength transfer.

OBJECTIVE

We aimed to investigate the existence of the vertical strength transfer phenomenon as a response to various UB and LB exercise configurations and to identify potential mechanisms underpinning its occurrence.

METHODS

A systematic search using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) for Scoping Reviews protocol was conducted in February 2024 using four databases (Web of Science, MEDLINE, Scopus and CINAHL) to identify peer-reviewed articles that investigated the vertical strength transfer phenomenon.

RESULTS

Of the 5242 identified articles, 24 studies met the inclusion criteria. Findings suggest that the addition of UB strength training to LB endurance exercise may help preserve power-generating capacity for the leg muscle fibres. Furthermore, systemic endocrine responses to high-volume resistance exercise may beneficially modulate adaptations in precedingly or subsequently trained muscles from a different body region, augmenting their strength gains. Last, strength training for LB could result in improved strength of untrained UB, likely due to the increased central neural drive.

CONCLUSIONS

Vertical strength transfer existence is enabled by neurophysiological mechanisms. Future research should involve athletic populations, examining the potential of vertical strength transfer to facilitate athletic performance and preserve strength in injured extremities.

The evolving roles of Wnt signaling in stem cell proliferation and differentiation, the development of human diseases, and therapeutic opportunities

The evolutionarily conserved Wnt signaling pathway plays a central role in development and adult tissue homeostasis across species. Wnt proteins are secreted, lipid-modified signaling molecules that activate the canonical (β-catenin dependent) and non-canonical (β-catenin independent) Wnt signaling pathways. Cellular behaviors such as proliferation, differentiation, maturation, and proper body-axis specification are carried out by the canonical pathway, which is the best characterized of the known Wnt signaling paths. Wnt signaling has emerged as an important factor in stem cell biology and is known to affect the self-renewal of stem cells in various tissues. This includes but is not limited to embryonic, hematopoietic, mesenchymal, gut, neural, and epidermal stem cells. Wnt signaling has also been implicated in tumor cells that exhibit stem cell-like properties. Wnt signaling is crucial for bone formation and presents a potential target for the development of therapeutics for bone disorders. Not surprisingly, aberrant Wnt signaling is also associated with a wide variety of diseases, including cancer. Mutations of Wnt pathway members in cancer can lead to unchecked cell proliferation, epithelial-mesenchymal transition, and metastasis. Altogether, advances in the understanding of dysregulated Wnt signaling in disease have paved the way for the development of novel therapeutics that target components of the Wnt pathway. Beginning with a brief overview of the mechanisms of canonical and non-canonical Wnt, this review aims to summarize the current knowledge of Wnt signaling in stem cells, aberrations to the Wnt pathway associated with diseases, and novel therapeutics targeting the Wnt pathway in preclinical and clinical studies.

Frizzleds act as dynamic pharmacological entities

The Frizzled family of transmembrane receptors (FZD1-10) belongs to the class F of G protein-coupled receptors (GPCRs). FZDs bind to and are activated by Wingless/Int1 (WNT) proteins. The WNT/FZD signaling system regulates crucial aspects of developmental biology and stem-cell regulation. Dysregulation of WNT/FZD communication can lead to developmental defects and diseases such as cancer and fibrosis. Recent insight into the activation mechanisms of FZDs has underlined that protein dynamics and conserved microswitches are essential for FZD-mediated information flow and build the basis for targeting these receptors pharmacologically. In this review, we summarize recent advances in our understanding of FZD activation, and how novel concepts merge and collide with existing dogmas in the field.

Dysregulation of cellular membrane homeostasis as a crucial modulator of cancer risk

Cellular membranes serve as an epicentre combining extracellular and cytosolic components with membranous effectors, which together support numerous fundamental cellular signalling pathways that mediate biological responses. To execute their functions, membrane proteins, lipids and carbohydrates arrange, in a highly coordinated manner, into well-defined assemblies displaying diverse biological and biophysical characteristics that modulate several signalling events. The loss of membrane homeostasis can trigger oncogenic signalling. More recently, it has been documented that select membrane active dietaries (MADs) can reshape biological membranes and subsequently decrease cancer risk. In this review, we emphasize the significance of membrane domain structure, organization and their signalling functionalities as well as how loss of membrane homeostasis can steer aberrant signalling. Moreover, we describe in detail the complexities associated with the examination of these membrane domains and their association with cancer. Finally, we summarize the current literature on MADs and their effects on cellular membranes, including various mechanisms of dietary chemoprevention/interception and the functional links between nutritional bioactives, membrane homeostasis and cancer biology.

Exploring the role of sporadic BRAF and KRAS mutations during colorectal cancer pathogenesis: A spotlight on the contribution of the endosome-lysosome system

The highly heterogenous nature of colorectal cancer can significantly hinder its early and accurate diagnosis, eventually contributing to high mortality rates. The adenoma-carcinoma sequence and serrated polyp-carcinoma sequence are the two most common sequences in sporadic colorectal cancer. Genetic alterations in adenomatous polyposis coli (APC), v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) and tumour protein 53 (TP53) genes are critical in adenoma-carcinoma sequence, whereas v-Raf murine sarcoma viral oncogene homolog B (BRAF) and MutL Homolog1 (MLH1) are driving oncogenes in the serrated polyp-carcinoma sequence. Sporadic mutations in these genes contribute differently to colorectal cancer pathogenesis by introducing distinct alterations in several signalling pathways that rely on the endosome-lysosome system. Unsurprisingly, the endosome-lysosome system plays a pivotal role in the hallmarks of cancer and contributes to specialised colon function. Thus, the endosome-lysosome system might be distinctively influenced by different mutations and these alterations may contribute to the heterogenous nature of sporadic colorectal cancer. This review highlights potential connections between major sporadic colorectal cancer mutations and the diverse pathogenic mechanisms driven by the endosome-lysosome system in colorectal carcinogenesis.

The ubiquitin ligase HUWE1 enhances WNT signaling by antagonizing destruction complex-mediated β-catenin degradation and through a mechanism independent of β-catenin stability

WNT/β-catenin signaling is mediated by the transcriptional coactivator β-catenin (CTNNB1). CTNNB1 abundance is regulated by phosphorylation and proteasomal degradation promoted by a destruction complex composed of the scaffold proteins APC and AXIN1 or AXIN2, and the kinases CSNK1A1 and GSK3A or GSK3B. Loss of CSNK1A1 increases CTNNB1 abundance, resulting in hyperactive WNT signaling. Previously, we demonstrated that the HECT domain ubiquitin ligase HUWE1 is necessary for hyperactive WNT signaling in HAP1 haploid human cells lacking CSNK1A1. Here, we investigate the mechanism underlying this requirement. In the absence of CSNK1A1, GSK3A/GSK3B still phosphorylated a fraction of CTNNB1, promoting its degradation. HUWE1 loss enhanced GSK3A/GSK3B-dependent CTNNB1 phosphorylation, further reducing CTNNB1 abundance. However, the reduction in CTNNB1 caused by HUWE1 loss was disproportionately smaller than the reduction in WNT target gene transcription. To test if the reduction in WNT signaling resulted from reduced CTNNB1 abundance alone, we engineered the endogenous CTNNB1 locus in HAP1 cells to encode a CTNNB1 variant insensitive to destruction complex-mediated phosphorylation and degradation. HUWE1 loss in these cells reduced WNT signaling with no change in CTNNB1 abundance. Genetic interaction and overexpression analyses revealed that the effects of HUWE1 on WNT signaling were not only mediated by GSK3A/GSK3B, but also by APC and AXIN1. Regulation of WNT signaling by HUWE1 required its ubiquitin ligase activity. These results suggest that in cells lacking CSNK1A1, a destruction complex containing APC, AXIN1 and GSK3A/GSK3B downregulates WNT signaling by phosphorylating and targeting CTNNB1 for degradation. HUWE1 enhances WNT signaling by antagonizing this activity. Therefore, HUWE1 enhances WNT/CTNNB1 signaling through two mechanisms, one that regulates CTNNB1 abundance and another that is independent of CTNNB1 stability. Coordinated regulation of CTNNB1 abundance and an independent signaling step by HUWE1 would be an efficient way to control WNT signaling output, enabling sensitive and robust activation of the pathway.

14-3-3ε: a protein with complex physiology function but promising therapeutic potential in cancer

Over the past decade, the role of the 14-3-3 protein has received increasing interest. Seven subtypes of 14-3-3 proteins exhibit high homology; however, each subtype maintains its specificity. The 14-3-3ε protein is involved in various physiological processes, including signal transduction, cell proliferation, apoptosis, autophagy, cell cycle regulation, repolarization of cardiac action, cardiac development, intracellular electrolyte homeostasis, neurodevelopment, and innate immunity. It also plays a significant role in the development and progression of various diseases, such as cardiovascular diseases, inflammatory diseases, neurodegenerative disorders, and cancer. These immense and various involvements of 14-3-3ε in diverse processes makes it a promising target for drug development. Although extensive research has been conducted on 14-3-3 dimers, studies on 14-3-3 monomers are limited. This review aimed to provide an overview of recent reports on the molecular mechanisms involved in the regulation of binding partners by 14-3-3ε, focusing on issues that could help advance the frontiers of this field. Video Abstract.

Osteoblast-derived exosomes promote osteogenic differentiation of osteosarcoma cells via URG4/Wnt signaling pathway

Osteosarcoma is a primary malignant bone tumor. Although surgery and chemotherapy are the main treatment methods, the overall curative effect remains unsatisfactory. Therefore, there is an urgent need to develop new therapeutic options for osteosarcoma. In this study, the effect and molecular mechanism of osteoblast-derived exosomes on the treatment of osteosarcoma were evaluated. Human primary osteoblasts were cultured to observe the effects of osteoblast-derived exosomes on the osteogenic differentiation of osteosarcoma cells both in vitro and in vivo. Alizarin red staining and alkaline phosphatase detection were used to evaluate the degree of osteogenic differentiation, and immunofluorescence and Western blotting were used to detect protein expression. The results showed that osteoblast-derived exosomes effectively inhibited the proliferation of osteosarcoma cells and promoted their mineralization in vitro. The exosomes also significantly inhibited tumor growth and promoted tumor tissue mineralization in vivo. Osteoblast-derived exosomes upregulated the expression of bone sialoprotein, osteonectin, osteopontin, runt-related transcription factor 2, and Wnt inhibitory factor 1, downregulated the expression of cyclin D1, and suppressed the nuclear accumulation of β-catenin and promoted its phosphorylation in vitro and in vivo. However, these effects were significantly reversed by upregulated gene (URG) 4 overexpression. These findings suggest that osteoblast-derived exosomes could activate the osteogenic differentiation process in osteosarcoma cells and promote their differentiation by targeting the URG4/Wnt signaling pathway.

Intestinal Paneth cell differentiation relies on asymmetric regulation of Wnt signaling by Daam1/2

The mammalian intestine is one of the most rapidly self-renewing tissues, driven by stem cells residing at the crypt bottom. Paneth cells form a major element of the niche microenvironment providing various growth factors to orchestrate intestinal stem cell homeostasis, such as Wnt3. Different Wnt ligands can selectively activate β-catenin-dependent (canonical) or -independent (noncanonical) signaling. Here, we report that the Dishevelled-associated activator of morphogenesis 1 (Daam1) and its paralogue Daam2 asymmetrically regulate canonical and noncanonical Wnt (Wnt/PCP) signaling. Daam1/2 interacts with the Wnt inhibitor RNF43, and Daam1/2 double knockout stimulates canonical Wnt signaling by preventing RNF43-dependent degradation of the Wnt receptor, Frizzled (Fzd). Single-cell RNA sequencing analysis revealed that Paneth cell differentiation is impaired by Daam1/2 depletion because of defective Wnt/PCP signaling. Together, we identified Daam1/2 as an unexpected hub molecule coordinating both canonical and noncanonical Wnt, which is fundamental for specifying an adequate number of Paneth cells.

Role of exosomes in metastasis and therapeutic resistance in esophageal cancer

Esophageal cancer (EC) has a high incidence and mortality rate and is emerging as one of the most common health problems globally. Owing to the lack of sensitive detection methods, uncontrollable rapid metastasis, and pervasive treatment resistance, EC is often diagnosed in advanced stages and is susceptible to local recurrence. Exosomes are important components of intercellular communication and the exosome-mediated crosstalk between the cancer and surrounding cells within the tumor microenvironment plays a crucial role in the metastasis, progression, and therapeutic resistance of EC. Considering the critical role of exosomes in tumor pathogenesis, this review focused on elucidating the impact of exosomes on EC metastasis and therapeutic resistance. Here, we summarized the relevant signaling pathways involved in these processes. In addition, we discussed the potential clinical applications of exosomes for the early diagnosis, prognosis, and treatment of EC.

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.

Pathway selectivity in Frizzleds is achieved by conserved micro-switches defining pathway-determining, active conformations

The class Frizzled of G protein-coupled receptors (GPCRs), consisting of ten Frizzled (FZD1-10) paralogs and Smoothened, remains one of the most enigmatic GPCR families. This class mediates signaling predominantly through Disheveled (DVL) or heterotrimeric G proteins. However, the mechanisms underlying pathway selection are elusive. Here we employ a structure-driven mutagenesis approach in combination with an extensive panel of functional signaling readouts to investigate the importance of conserved state-stabilizing residues in FZD5 for signal specification. Similar data were obtained for FZD4 and FZD10 suggesting that our findings can be extrapolated to other members of the FZD family. Comparative molecular dynamics simulations of wild type and selected FZD5 mutants further support the concept that distinct conformational changes in FZDs specify the signal outcome. In conclusion, we find that FZD5 and FZDs in general prefer coupling to DVL rather than heterotrimeric G proteins and that distinct active state micro-switches in the receptor are essential for pathway selection arguing for conformational changes in the receptor protein defining transducer selectivity.

Circular RNAs: novel actors of Wnt signaling pathway in lung cancer progression

Circular RNAs (CircRNAs) are a class of regulatory RNA transcripts, which are ubiquitously expressed in eukaryotes. CircRNA dysregulation has been shown to disrupt the interaction of the Wnt/β-catenin pathway, which regulates several biological processes involved in tumorigenesis, thereby contributing to the development and progression of cancer. Interactions of tumor-derived circRNAs with the Wnt/β-catenin signaling pathway provide both clinical diagnostic biomarkers and promising therapeutic targets. In this review, we outlined current evidence on the roles of circRNAs associated with the Wnt/β-catenin pathway in regulating lung cancer formation and development. We believe that our findings will assist in the advancement or establishment of circRNA-based lung cancer therapeutic approaches.

The recent progress of peptide regulators for the Wnt/β-catenin signaling pathway

Wnt signaling plays an important role in many biological processes such as stem cell self-renewal, cell proliferation, migration, and differentiation. The β-catenin-dependent signaling pathway mainly regulates cell proliferation, differentiation, and migration. In the Wnt/β-catenin signaling pathway, the Wnt family ligands transduce signals through LRP5/6 and Frizzled receptors to the Wnt/β-catenin signaling cascades. Wnt-targeted therapy has garnered extensive attention. The most commonly used approach in targeted therapy is small-molecule regulators. However, it is difficult for small-molecule regulators to make great progress due to their inherent defects. Therapeutic peptide regulators targeting the Wnt signaling pathway have become an alternative therapy, promising to fill the gaps in the clinical application of small-molecule regulators. In this review, we describe recent advances in peptide regulators for Wnt/β-catenin signaling.

Lipolysis and gestational diabetes mellitus onset: a case-cohort genome-wide association study in Chinese

BACKGROUND

Genetic knowledge of gestational diabetes mellitus (GDM) in Chinese women is quite limited. This study aimed to identify the risk factors and mechanism of GDM at the genetic level in a Chinese population.

METHODS

We conducted a genome-wide association study (GWAS) based on single nucleotide polymorphism (SNP) array genotyping (ASA-CHIA Bead chip, Illumina) and a case-cohort study design. Variants including SNPs, copy number variants (CNVs), and insertions-deletions (InDels) were called from genotyping data. A total of 2232 pregnant women were enrolled in their first/second trimester between February 2018 and December 2020 from Anqing Municipal Hospital in Anhui Province, China. The GWAS included 193 GDM patients and 819 subjects without a diabetes diagnosis, and risk ratios (RRs) and their 95% confidence intervals (CIs) were estimated by a regression-based method conditional on the population structure. The calling and quality control of genotyping data were performed following published guidelines. CNVs were merged into CNV regions (CNVR) to simplify analyses. To interpret the GWAS results, gene mapping and overexpression analyses (ORAs) were further performed to prioritize the candidate genes and related biological mechanisms.

RESULTS

We identified 14 CNVRs (false discovery rate corrected P values < 0.05) and two suggestively significant SNPs (P value < 0.00001) associated with GDM, and a total of 19 candidate genes were mapped. Ten genes were significantly enriched in gene sets related to lipase (triglyceride lipase and lipoprotein lipase) activity (LIPF, LIPK, LIPN, and LIPJ genes), oxidoreductase activity (TPH1 and TPH2 genes), and cellular components beta-catenin destruction complex (APC and GSK3B genes), Wnt signalosome (APC and GSK3B genes), and lateral element in the Gene Ontology resource (BRCA1 and SYCP2 genes) by two ORA methods (adjusted P values < 0.05).

CONCLUSIONS

Genes related to lipolysis, redox reaction, and proliferation of islet β-cells are associated with GDM in Chinese women. Energy metabolism, particularly lipolysis, may play an important role in GDM aetiology and pathology, which needs further molecular studies to verify.

Novel Insights into the Role of Kras in Myeloid Differentiation: Engaging with Wnt/β-Catenin Signaling

Cells of the HL-60 myeloid leukemia cell line can be differentiated into neutrophil-like cells by treatment with dimethyl sulfoxide (DMSO). The molecular mechanisms involved in this differentiation process, however, remain unclear. This review focuses on the differentiation of HL-60 cells. Although the Ras proteins, a group of small GTP-binding proteins, are ubiquitously expressed and highly homologous, each has specific molecular functions. Kras was shown to be essential for normal mouse development, whereas Hras and Nras are not. Kras knockout mice develop profound hematopoietic defects, indicating that Kras is required for hematopoiesis in adults. The Wnt/β-catenin signaling pathway plays a crucial role in regulating the homeostasis of hematopoietic cells. The protein β-catenin is a key player in the Wnt/β-catenin signaling pathway. A great deal of evidence shows that the Wnt/β-catenin signaling pathway is deregulated in malignant tumors, including hematological malignancies. Wild-type Kras acts as a tumor suppressor during DMSO-induced differentiation of HL-60 cells. Upon DMSO treatment, Kras translocates to the plasma membrane, and its activity is enhanced. Inhibition of Kras attenuates CD11b expression. DMSO also elevates levels of GSK3β phosphorylation, resulting in the release of unphosphorylated β-catenin from the β-catenin destruction complex and its accumulation in the cytoplasm. The accumulated β-catenin subsequently translocates into the nucleus. Inhibition of Kras attenuates Lef/Tcf-sensitive transcription activity. Thus, upon treatment of HL-60 cells with DMSO, wild-type Kras reacts with the Wnt/β-catenin pathway, thereby regulating the granulocytic differentiation of HL-60 cells. Wild-type Kras and the Wnt/β-catenin signaling pathway are activated sequentially, increasing the levels of expression of C/EBPα, C/EBPε, and granulocyte colony-stimulating factor (G-CSF) receptor.

maea affects head formation through ß-catenin degradation during early Xenopus laevis development

Canonical Wnt signalling plays important roles in early embryogenesis, such as axis formation due to its activation and head formation due to its inhibition. ß-catenin protein stability is a key factor in canonical Wnt signalling. Several E3 ubiquitin ligases contribute to ß-catenin degradation through the ubiquitin/proteasome system. We characterised an E3 ubiquitin ligase gene, Xenopus laevis macrophage erythroblast attacher (maea), during early development. maea transcripts were ubiquitously detected in early embryos. The expression levels of the Wnt target genes nodal homolog 3, gene 1 (nodal3.1), and siamois homeodomain 1 (sia1), which were induced by injection with ß-catenin mRNA, were reduced by maea.S mRNA co-injection. maea.S overexpression at the anterior dorsal region enlarged head structures, whereas Maea knockdown interfered with head formation in Xenopus embryos. Maea.S decreased and ubiquitinated ß-catenin protein. ß-catenin-4KRs protein, which mutated the four lysine (K) residues known as ubiquitinated sites to arginine (R) residues, was also ubiquitinated and degraded by Maea.S. These findings suggest that Maea contributes to β-catenin degradation by ubiquitination of unknown lysine residues in early Xenopus development.

The role of β-catenin in cardiac diseases

The Wnt/β-catenin signaling pathway is a classical Wnt pathway that regulates the stability and nuclear localization of β-catenin and plays an important role in adult heart development and cardiac tissue homeostasis. In recent years, an increasing number of researchers have implicated the dysregulation of this signaling pathway in a variety of cardiac diseases, such as myocardial infarction, arrhythmias, arrhythmogenic cardiomyopathy, diabetic cardiomyopathies, and myocardial hypertrophy. The morbidity and mortality of cardiac diseases are increasing, which brings great challenges to clinical treatment and seriously affects patient health. Thus, understanding the biological roles of the Wnt/β-catenin pathway in these diseases may be essential for cardiac disease treatment and diagnosis to improve patient quality of life. In this review, we summarize current research on the roles of β-catenin in human cardiac diseases and potential inhibitors of Wnt/β-catenin, which may provide new strategies for cardiac disease therapies.

Visualizing WNT signaling in mammalian systems

WNT/CTNNB1 signaling plays a critical role in the development of all multicellular animals. Here, we include both the embryonic stages, during which tissue morphogenesis takes place, and the postnatal stages of development, during which tissue homeostasis occurs. Thus, embryonic development concerns lineage development and cell fate specification, while postnatal development involves tissue maintenance and regeneration. Multiple tools are available to researchers who want to investigate, and ideally visualize, the dynamic and pleiotropic involvement of WNT/CTNNB1 signaling in these processes. Here, we discuss and evaluate the decisions that researchers need to make in identifying the experimental system and appropriate tools for the specific question they want to address, covering different types of WNT/CTNNB1 reporters in cells and mice. At a molecular level, advanced quantitative imaging techniques can provide spatio-temporal information that cannot be provided by traditional biochemical assays. We therefore also highlight some recent studies to show their potential in deciphering the complex and dynamic mechanisms that drive WNT/CTNNB1 signaling.

Mapping the protein binding site of the (pro)renin receptor using in silico 3D structural analysis

We have previously reported that monoclonal antibodies against the (pro)renin receptor [(P)RR] can reduce the Wnt/β-catenin-dependent development of pancreatic ductal adenocarcinoma (PDAC), the most common pancreatic cancer. Antibodies against two (P)RR regions (residues 47–60 and 200–213) located in the extracellular domain (ECD) reduced the proliferation of human PDAC cells in vitro. Although these regions probably participate in the activation of Wnt/β-catenin signaling, their functional significance remains unclear. Moreover, the (P)RR ECD is predicted to possess an intrinsically disordered region (IDR), which allows multiple protein interactions because of its conformational flexibility. In this study, we investigated the significance of the two regions and the IDR by in silico 3D structural analysis using the AlphaFold2 program and evolutionary sequence conservation profile. The model showed that ECD adopted a folded domain (residues 17–269) and had an IDR (residues 270–296). The two regions mapped onto the structural model formed a continuous surface patch comprising evolutionarily conserved hydrophobic residues. The homodimeric structure predicted by AlphaFold2 showed that full-length (P)RR comprising the ECD, single-span transmembrane, and cytoplasmic domains formed a twofold symmetric dimer via the ECD, which explains the experimentally proven homodimerization. The dimer model possessed two hand-shaped grooves with residues 47–60 and 200–213 in their palms and the IDR as their fingers. Based on these findings, we propose that the IDR-containing hydrophobic grooves act as a binding site for (P)RR and perform multiple functions, including Wnt signaling activation.

Stretching Training Rehabilitation Has Potential to Alleviate Ankylosing Spondylitis in Mice by Inactivating the Wnt/β-Catenin Pathway

Ankylosing spondylitis (AS) is a chronic inflammatory disease characterized by invasion of the joints of the central axis that involves soft tissues and joints surrounding the spine. Stretching training rehabilitation (STR) has been widely applied for the treatment of AS. The Wnt/β-catenin signalling pathway is closely related to AS. In this study, we aimed to explore the potential molecular mechanisms underlying the protective effect of STR on AS both in vitro and in vivo. Male DBA/1 mice were employed to establish an AS animal model. Hematoxylin-eosin staining showed that STR reversed pathological damages in bone tissues and the total antioxidant capacity of AS mice and increased the antioxidant capacity by upregulating superoxide dismutase and malondialdehyde expression in DBA/1 mice. The MTT, RT-qPCR, and Western blotting results further indicated that STR improved the survival rate of cells by downregulating the expression of target genes in the Wnt/β-catenin pathway and by inhibiting cell inflammation and apoptosis. In conclusion, our findings indicated that STR treatment might be an effective therapeutical strategy for AS.

Clone wars: From molecules to cell competition in intestinal stem cell homeostasis and disease

The small intestine is among the fastest self-renewing tissues in adult mammals. This rapid turnover is fueled by the intestinal stem cells residing in the intestinal crypt. Wnt signaling plays a pivotal role in regulating intestinal stem cell renewal and differentiation, and the dysregulation of this pathway leads to cancer formation. Several studies demonstrate that intestinal stem cells follow neutral drift dynamics, as they divide symmetrically to generate other equipotent stem cells. Competition for niche space and extrinsic signals in the intestinal crypt is the governing mechanism that regulates stemness versus cell differentiation, but the underlying molecular mechanisms are still poorly understood, and it is not yet clear how this process changes during disease. In this review, we highlight the mechanisms that regulate stem cell homeostasis in the small intestine, focusing on Wnt signaling and its regulation by RNF43 and ZNRF3, key inhibitors of the Wnt pathway. Furthermore, we summarize the evidence supporting the current model of intestinal stem cell regulation, highlighting the principles of neutral drift at the basis of intestinal stem cell homeostasis. Finally, we discuss recent studies showing how cancer cells bypass this mechanism to gain a competitive advantage against neighboring normal cells.

Stem cells in the gut rapidly renew themselves through processes that cancer cells co-opt to trigger tumor development. Gabriele Colozza from the Institute of Molecular Biotechnology in Vienna, Austria, and colleagues review how a network of critical molecular signals and competition for limited space help to regulate the dynamics of stem cells in the intestines. The correct balance between self-renewal and differentiation is tightly controlled by the so-called Wnt signaling pathway and its inhibitors. Competition between dividing cells in the intestinal crypts, the locations between finger-like protrusions in the gut where stem cells are found, provides another protective mechanism against runaway stem cell growth. However, intestinal cancer cells, thanks to their activating mutations, bypass these safeguards to gain a survival advantage. Drugs that target these ‘super-competitive’ behaviors could therefore help combat tumor proliferation.

Effects of the Wnt/β-Catenin Signaling Pathway on Proliferation and Apoptosis of Gastric Cancer Cells

Objective

To explore the effect of the Wnt/β-catenin signaling pathway on the proliferation and apoptosis of gastric cancer cells.

Methods

An MTT colorimetric assay was used to detect the inhibitory effect of the Wnt/β-catenin signaling pathway inhibitor FH535 on the proliferation of MKN45 gastric cancer cells. The cell proliferation index (PI) and apoptosis index (AI) were measured by flow cytometry. The expression levels of β-catenin, c-myc, and cleaved caspase-3 in MKN45 gastric cancer cells were detected.

Results

After using the Wnt/β-catenin signaling pathway inhibitor FH535, MKN45 gastric cancer cells showed obvious shrinkage, death, and cell density decrease. MTT showed that the A value of MKN45 gastric cancer cells in FH535 group was significantly lower than that in the control group (P < 0.05). The survival rate of MKN45 gastric cancer cells in FH535 group was significantly lower than that in the control group (P < 0.05). The cell cycle of gastric cancer was arrested in G0/G1 phase. The expression levels of β-catenin and c-myc protein in MKN45 gastric cancer cells in FH535 group decreased significantly (P < 0.05), while the expression level of cleaved caspase-3 protein increased significantly (P < 0.05).

Conclusion

The Wnt/β-catenin signal molecule can maintain the proliferation of gastric cancer cells. Inhibition of the Wnt/β-catenin signaling pathway can inhibit the proliferation of gastric cancer cells and promote the apoptosis of MKN45 gastric cancer cells.

Molecular mechanism, regulation, and therapeutic targeting of the STAT3 signaling pathway in esophageal cancer (Review)

Esophageal cancer (EC) is the seventh most common cancer globally, and the overall 5-year survival rate is only 20%. Signal transducer and activator of transcription 3 (STAT3) is aberrantly activated in EC, and its activation is associated with a poor prognosis. STAT3 can be activated by canonical pathways such as the JAK/STAT3 pathway as well as non-canonical pathways including the Wnt/STAT3 and COX2/PGE2/STAT3 pathways. Activated STAT3, present as phosphorylated STAT3 (p-STAT3), can be transported into the nucleus to regulate downstream genes, including VEGF, cyclin D1, Bcl-xL, and matrix metalloproteinases (MMPs), to promote cancer cell proliferation and induce resistance to therapy. Non-coding RNAs, including microRNAs (miRNAs/miRs), circular RNAs (circRNAs), and long non-coding RNAs (lncRNAs), play a vital role in regulating the STAT3 signaling pathway in EC. Several miRNAs promote or suppress the function of STAT3 in EC, while lncRNAs and circRNAs primarily promote the effects of STAT3 and the progression of cancer. Additionally, various drugs and natural compounds can target STAT3 to suppress the malignant behavior of EC cells, providing novel insights into potential EC therapies.

Cysteine and glycine-rich protein 2 promotes hypoxic pulmonary vascular smooth muscle cell proliferation through the Wnt3α-β-catenin/lymphoid enhancer-binding factor 1 pathway

Pulmonary hypertension (PH) is mainly characterized by abnormal pulmonary vascular hyperplasia and vascular remodeling, but its mechanism is complicated and currently unclear. Cysteine and glycine-rich protein 2 (Csrp2) has been reported to promote cell proliferation and migration, and affect cell cycle progression. As a new invasive actin-binding factor, Csrp2 increased the invasion and even metastasis of some cancer cells. It was associated with tumor recurrence and chemotherapy resistance. However, the role of Csrp2 in PH remains unknown. We found that Csrp2 expression was increased both in pulmonary arteries (PAs) and smooth muscle cells (PASMCs) in PH. Csrp2 enhanced PASMC proliferation and phenotypic transition. The Wnt3α-β-catenin/lymphoid enhancer-binding factor 1 (LEF1) pathway is involved in cell proliferation and phenotypic transition regulated by Csrp2 expression. These results suggest that hypoxia downregulates YinYang-1 (YY1) and then increases Csrp2 expression. Increased Csrp2 promotes PASMC proliferation and phenotypic transition by activating the Wnt3α-β-catenin/LEF1 pathways, which leads to pulmonary vascular remodeling and even provides a new theoretical basis for studying the pathogenesis and therapeutic targets of PH.

Neuronal ER-Signalosome Proteins as Early Biomarkers in Prodromal Alzheimer's Disease Independent of Amyloid-β Production and Tau Phosphorylation

There exists considerable interest to unveil preclinical period and prodromal stages of Alzheimer's disease (AD). The mild cognitive impairment (MCI) is characterized by significant memory and/or other cognitive domains impairments, and is often considered the prodromal phase of AD. The cerebrospinal fluid (CSF) levels of β-amyloid (βA), total tau (t-tau), and phosphorylated tau (p-tau) have been used as biomarkers of AD albeit their significance as indicators during early stages of AD remains far from accurate. The new biomarkers are being intensively sought as to allow identification of pathological processes underlying early stages of AD. Fifty-three participants (75.4 ± 8.3 years) were classified in three groups as cognitively normal healthy controls (HC), MCI, and subjective memory complaints (SMC). The subjects were subjected to a battery of neurocognitive tests and underwent lumbar puncture for CSF extraction. The CSF levels of estrogen-receptor (ER)-signalosome proteins, βA, t-tau and p-tau, were submitted to univariate, bivariate, and multivariate statistical analyses. We have found that the components of the ER-signalosome, namely, caveolin-1, flotilin-1, and estrogen receptor alpha (ERα), insulin growth factor-1 receptor β (IGF1Rβ), prion protein (PrP), and plasmalemmal voltage dependent anion channel 1 (VDAC) could be detected in the CSF from all subjects of the HC, MCI, and SMC groups. The six proteins appeared elevated in MCI and slightly increased in SMC subjects compared to HC, suggesting that signalosome proteins undergo very early modifications in nerve cells. Using a multivariate approach, we have found that the combination of ERα, IGF-1Rβ, and VDAC are the main determinants of group segregation with resolution enough to predict the MCI stage. The analyses of bivariate relationships indicated that collinearity of ER-signalosome proteins vary depending on the stage, with some pairs displaying opposed relationships between HC and MCI groups, and the SMC stage showing either no relationships or behaviors similar to either HC or MCI stages. The multinomial logistic regression models of changes in ER-signalosome proteins provide reliable predictive criteria, particularly for the MCI. Notably, most of the statistical analyses revealed no significant relationships or interactions with classical AD biomarkers at either disease stage. Finally, the multivariate functions were highly correlated with outcomes from neurocognitive tests for episodic memory. These results demonstrate that alterations in ER-signalosome might provide useful diagnostic information on preclinical stages of AD, independently from classical biomarkers.

HER2-CDH1 Interaction via Wnt/B-Catenin Is Associated with Patients' Survival in HER2-Positive Metastatic Gastric Adenocarcinoma

Simple Summary

A deeper understanding of the molecular mechanisms involved in gastric cacner (GC) pathologenesis would help the identification of prognostic biomarkers and the development of new treatments. Human epidermal growth factor receptor 2 (HER2/ErbB2), a membrane-bound receptor of the EGFR family, may be overexpressed in GC. Trastuzumab is a HER2 inhibitor used to treat HER2+ metastatic gastric cancer (mGC). The present study aims to investigate the relationship between CDH1 mRNA expression and HER2-positivity in mGC using a multiplexed gene expression profile in two series of GC patients: 38 HER2+ and HER2- mGC and 36 HER2- GC with and without metastasis. Our results revealed the relationship between CDH1 and HER2 mRNA expression in mGC via the canonical WNT/β-catenin pathway and identified EGF as an independent prognostic biomarker for survival.

Abstract

Trastuzumab is a human epidermal growth factor receptor 2 (HER2) inhibitor used to treat HER2+ metastatic gastric cancer (mGC). The present study aims to investigate the relationship between CDH1 mRNA expression and HER2-positivity in mGC using a multiplexed gene expression profile in two series of gastric cancer (GC): Series 1 (n = 38): HER2+ and HER2- mGC; Series 2 (n = 36) HER2- GC with and without metastasis. To confirm the results, the same expression profiles were analyzed in 354 GC from The Cancer Genome Atlas (TCGA) dataset. The difference in gene expression connected HER2 overexpression with canonical wingless-type (Wnt)/β-catenin pathway and immunohistochemical (IHC) expression loss of E-cadherin (E-CAD). CDH1 mRNA expression was simultaneously associated with the rs16260-A variant and an increase in E-CAD expression. Differences in retinoic acid receptor alfa (RARA), RPL19 (coding for the 60S ribosomal L19 protein), catenin delta 1 (CTNND1), and epidermal growth factor (EGF) mRNA levels—all included in the Wnt/β-catenin pathway—were found associated with overall survival (OS). RARA, CTNND1, and EGF resulted in independent OS prognostic factors. EGF was confirmed as an independent factor along with TNM stage in HER2-overpressed mGC from TCGA collection. Our study highlighted factors involved in the WNT/β-catenin pathway that interconnected E-CAD with HER2 overexpression and patient survival.

NK4 Regulates Laryngeal Squamous Cell Carcinoma Cell Properties and Inhibits Tumorigenicity by Modulating the DKK1/Wnt/β-Catenin Axis

Objective

To investigate the effects of NK4 gene on the properties and tumorigenicity in laryngeal squamous cell carcinoma cell.

Methods

Here, we used the attenuated Salmonella carrying the NK4 gene to transfect the AMC-HN-8 cells and detected the expression of NK4 by the real-time quantitative polymerase chain reaction (q RT-PCR). The properties of NK4 gene was determined by MTT method, cell scratch test, and flow cytometry. A nude mouse tumorigenesis model was used to evaluate the effect of NK4 gene on the growth of AMC-HN-8 cells in vivo. While a western blot assay was used to assess the expression of DKK1, Wnt1 and β-Catenin in nude mouse tumors.

Results

qRT-PCR showed that the expression of NK4 in the transfection group was significantly higher than that in the control group (P<0.01), and the expression increased with the time of transfection. MTT results showed NK4 overexpression inhibited the proliferation of AMC-HN-8 cells, and the inhibitory activity no longer increased with increasing dose when 30% expression supernatant was added (P<0.01). Scratch experiment showed that NK4 overexpression decreased the cell migration ability (P<0.01). Annexin V/PI double staining experiment showed that NK4 gene induced AMC-HN-8 cell apoptosis (P<0.01), and cell cycle arrest in S phase (P<0.01). NK4 overexpression inhibited tumor formation ability of AMC-HN-8 cells in vivo (P <0.05). WB detection showed that the expression of DKK1 increased, Wnt1 and β-Catenin protein decreased after the high expression of NK4.

Conclusions

NK4 gene inhibit cell proliferation and migration, while promote cell apoptosis, and induce cell cycle arrest in S phase of laryngeal carcinoma AMC-HN-8 cells. NK4 overexpression inhibit the tumorigenesis ability of AMC-HN-8 cells, which may be related to the regulation of DKK1/Wnt1/β-Catenin signal axis.

Functions of the (pro)renin receptor (Atp6ap2) at molecular and system levels: pathological implications in hypertension, renal and brain development, inflammation, and fibrosis

The (pro)renin receptor [(P)RR, Atp6ap2] was initially discovered as a membrane-bound binding partner of prorenin and renin. A soluble (P)RR has additional paracrine effects and is involved in metabolic syndrome and kidney damage. Meanwhile it is clear that most of the effects of the (P)RR are independent of prorenin. In the kidney, (P)RR plays an important role in renal dysfunction by activating proinflammatory and profibrotic molecules. In the brain, (P)RR is expressed in cardiovascular regulatory nuclei and is linked to hypertension. (P)RR is known to be an essential component of the v-ATPase as a key accessory protein and plays an important role in kidney, brain and heart via regulating the pH of the extracellular space and intracellular compartments. V-ATPase and (P)RR together act on WNT and mTOR signalling pathways, which are responsible for cellular homeostasis and autophagy. (P)RR through its role in v-ATPase assembly and function is also important for fast recycling endocytosis by megalin. In the kidney, megalin together with v-ATPase and (P)RR is crucial for endocytic uptake of components of the RAS and their intracellular processing. In the brain, (P)RR, v-ATPases and megalin are important regulators both during development and in the adult. All three proteins are associated with diseases such as XLMR, XMRE, X-linked parkinsonism and epilepsy, cognitive disorders with Parkinsonism, spasticity, intellectual disability, and Alzheimer's Disease which are characterized by impaired neuronal function and/or neuronal loss. The present review focusses on the relevant effects of Atp6ap2 without assigning them necessarily to the RAS. Mechanistically, many effects can be well explained by the role of Atp6ap2 for v-ATPase assembly and function. Furthermore, application of a soluble (P)RR analogue as new therapeutic option is discussed.

Cell Biology of Canonical Wnt Signaling

Wnt signaling has multiple functions beyond the transcriptional effects of β-catenin stabilization. We review recent investigations that uncover new cell physiological effects through the regulation of Wnt receptor endocytosis, Wnt-induced stabilization of proteins (Wnt-STOP), macropinocytosis, increase in lysosomal activity, and metabolic changes. Many of these growth-promoting effects of canonical Wnt occur within minutes and are independent of new protein synthesis. A key element is the sequestration of glycogen synthase kinase 3 (GSK3) inside multivesicular bodies and lysosomes. Twenty percent of human proteins contain consecutive GSK3 phosphorylation motifs, which in the absence of Wnt can form phosphodegrons for polyubiquitination and proteasomal degradation. Wnt signaling by either the pharmacological inhibition of GSK3 or the loss of tumor-suppressor proteins, such as adenomatous polyposis coli (APC) and Axin1, increases lysosomal acidification, anabolic metabolites, and macropinocytosis, which is normally repressed by the GSK3-Axin1-APC destruction complex. The combination of these cell physiological effects drives cell growth. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

From Channels to Canonical Wnt Signaling: A Pathological Perspective

Wnt signaling is an important pathway mainly active during embryonic development and controlling cell proliferation. This regulatory pathway is aberrantly activated in several human diseases. Ion channels are known modulators of several important cellular functions ranging from the tuning of the membrane potential to modulation of intracellular pathways, in particular the influence of ion channels in Wnt signaling regulation has been widely investigated. This review will discuss the known links between ion channels and canonical Wnt signaling, focusing on their possible roles in human metabolic diseases, neurological disorders, and cancer.

Wnt/β-catenin signaling: Structure, assembly and endocytosis of the signalosome

Wnt/β‐catenin signaling is an ancient pathway that regulates key aspects of embryonic development, cell differentiation, proliferation, and adult stem cell homeostasis. Work from different laboratories has shed light on the molecular mechanisms underlying the Wnt pathway, including structural details of ligand–receptor interactions. One key aspect that has emerged from multiple studies is that endocytosis of the receptor complex plays a crucial role in fine‐tuning Wnt/β‐catenin signaling. Endocytosis is a key process involved in both activation as well as attenuation of Wnt signaling, but how this is regulated is still poorly understood. Importantly, recent findings show that Wnt also regulates central metabolic pathways such as the acquisition of nutrients through actin‐driven endocytic mechanisms. In this review, we propose that the Wnt pathway displays diverse characteristics that go beyond the regulation of gene expression, through a connection with the endocytic machinery.

Zooming in on the WNT/CTNNB1 Destruction Complex: Functional Mechanistic Details with Implications for Therapeutic Targeting

WNT/CTNNB1 signaling is crucial for balancing cell proliferation and differentiation in all multicellular animals. CTNNB1 accumulation is the hallmark of WNT/CTNNB1 pathway activation and the key downstream event in both a physiological and an oncogenic context. In the absence of WNT stimulation, the cytoplasmic and nuclear levels of CTNNB1 are kept low because of its sequestration and phosphorylation by the so-called destruction complex, which targets CTNNB1 for proteasomal degradation. In the presence of WNT proteins, or as a result of oncogenic mutations, this process is impaired and CTNNB1 levels become elevated.Here we discuss recent advances in our understanding of destruction complex activity and inactivation, focusing on the individual components and interactions that ultimately control CTNNB1 turnover (in the "WNT off" situation) and stabilization (in the "WNT on" situation). We especially highlight the insights gleaned from recent quantitative, image-based studies, which paint an unprecedentedly detailed picture of the dynamic events that control destruction protein complex composition and function. We argue that these mechanistic details may reveal new opportunities for therapeutic intervention and could result in the destruction complex re-emerging as a target for therapy in cancer.