Wnt induces LRP6 signalosomes and promotes dishevelled-dependent LRP6 phosphorylation

Signalling pathways in a nutshell: from pathogenesis to therapeutical implications in prostate cancer

From tumorigenesis to the establishment of local or metastatic high-grade tumours, an integral part of the cellular lifespan relies on various signalling pathways. Particular pathways that allow cells to proliferate by creating a network of new blood vessels have been documented, whereas other pathways are primarily involved with a migration to distant body parts, partially through the process of epithelial-mesenchymal transition (EMT). This review will discuss the different signalling pathways, such as TGF-β, Cripto-1, Wnt pathways, Hedgehog, Notch and NF-κB pathways, and how they promote tumour initiation and progression by influencing diverse cellular processes and EMT in general and in benign and malignant prostate tumours. This review will discuss only the critical pathways. Therefore, many other types of signalling pathways which are related to prostate cancer will not be discussed. Possibilities for further investigation will be mentioned, as many underlying mechanisms involved in these pathways have potential as targets in future tumour therapy. This review will also introduce some novel clinical trials relating to the inhibition of signalling pathways and their clinical outcomes.

WNT-induced association of Frizzled and LRP6 is not sufficient for the initiation of WNT/β-catenin signaling

The Wingless/Int-1 (WNT) signaling network is essential to orchestrate central physiological processes such as embryonic development and tissue homeostasis. In the currently held tenet, WNT/β-catenin signaling is initiated by WNT-induced recruitment of Frizzleds (FZDs) and LRP5/6 followed by the formation of a multiprotein signalosome complex. Here, we use bioluminescence resonance energy transfer (BRET) to show that different WNT paralogs dynamically trigger FZD-LRP6 association. While WNT-induced receptor interaction was independent of C-terminal LRP6 phosphorylation, it was allosterically modulated by binding of the phosphoprotein Dishevelled (DVL) to FZD. WNT-16B emerged as a ligand of particular interest, as it efficiently promoted FZD-LRP6 association but, unlike WNT-3A, did not lead to WNT/β-catenin signaling. Transcriptomic analysis further revealed distinct transcriptional fingerprints of WNT-3A and WNT-16B stimulation in HEK293 cells. Additionally, single-molecule tracking demonstrated that, despite increasing FZD5 and LRP6 confinement, WNT-16B stimulation did not result in formation of higher-order receptor clusters, in contrast to WNT-3A. Our results suggest that FZD-WNT-LRP5/6 complex formation alone is not sufficient for the initiation of WNT/β-catenin signaling. Instead, we propose a two-step model, where initial ligand-induced FZD-LRP6 association must be followed by receptor clustering into higher-order complexes and subsequent phosphorylation of LRP6 for efficient activation of WNT/β-catenin signaling.

Wnt signalosome assembly is governed by conformational flexibility of Axin and by the AP2 clathrin adaptor

Wnt signal transduction relies on the direct inhibition of GSK3 by phosphorylated PPPSPxS motifs within the cytoplasmic tail of the LRP6 co-receptor. How GSK3 is recruited to LRP6 remains unclear. Here, we use nuclear magnetic resonance spectroscopy to identify the membrane-proximal PPPSPxS motif and its flanking sequences as the primary binding site for both Axin and GSK3, and an intrinsically disordered segment of Axin as its LRP6-interacting region (LIR). Co-immunoprecipitation and CRISPR-engineered mutations in endogenous Axin indicate that its docking at LRP6 is antagonized by a phospho-dependent foldback within LIR and by a PRTxR motif that allows Axin and GSK3 to form a multi-pronged interaction which favors their detachment from LRP6. Crucially, signaling by LRP6 also depends on its binding to the AP2 clathrin adaptor. We propose that the Wnt-driven clustering of LRP6 within clathrin-coated locales allows the Axin-GSK complex to dock at adjacent LRP6 molecules, while also exposing it to co-targeted kinases that change its activity in Wnt signal transduction.

Mechanistic insights into Wnt-β-catenin pathway activation and signal transduction

In multicellular organisms, Wnt proteins govern stem and progenitor cell renewal and differentiation to regulate embryonic development, adult tissue homeostasis and tissue regeneration. Defects in canonical Wnt signalling, which is transduced intracellularly by β-catenin, have been associated with developmental disorders, degenerative diseases and cancers. Although a simple model describing Wnt-β-catenin signalling is widely used to introduce this pathway and has largely remained unchanged over the past 30 years, in this Review we discuss recent studies that have provided important new insights into the mechanisms of Wnt production, receptor activation and intracellular signalling that advance our understanding of the molecular mechanisms that underlie this important cell-cell communication system. In addition, we review the recent development of molecules capable of activating the Wnt-β-catenin pathway with selectivity in vitro and in vivo that is enabling new lines of study to pave the way for the development of Wnt therapies for the treatment of human diseases.

A Novel tRF, HCETSR, Derived From tRNA-Glu/TTC, Inhibits HCC Malignancy by Regulating the SPBTN1-catenin Complex Axis

tRNA-derived fragments (tRFs), a novel class of small non-coding RNAs cleaved from transfer RNAs, have been implicated in tumor regulation. In this study, the role of a specific tRF, HCETSR is investigated, which is significantly downregulated in hepatocellular carcinoma (HCC) and correlates with advanced tumor burden and higher HCC mortality. Functional analyses revealed that HCETSR inhibits HCC malignancy and serves as an independent predictor of poor prognosis. Mechanistically, a novel SPTBN1/catenin complex axis regulated by HCETSR is identified. HCETSR binds to a critical domain of SPTBN1, disrupting its interaction with the catenin complex (comprising β-catenin, α-catenin, and P120-catenin), and facilitates the transfer of the catenin complex from the cell membrane to the nucleus. Specifically, HCETSR decreases the proteasomal degradation of β-catenin and inhibits the synthesis of nascent β-catenin. Furthermore, HCETSR suppresses the transcriptional activity of LEF1 through P120-catenin rather than α-catenin, thereby reducing β-catenin's influence on LEF1 activity. It is demonstrated that HCETSR is spliced from tRNA-Glu/TTC. The biogenesis of HCETSR and tRNA-Glu/TTC is regulated by the spliceosome and Dicer1. In conclusion, These findings suggest that HCETSR, derived from tRNA-Glu/TTC, inhibits HCC malignancy via modulation of the SPTBN1/catenin axis and may represent a promising prognostic marker and therapeutic strategy for HCC.

VPS45 Contributes to the Progression of Hepatocellular Carcinoma by Triggering the Wnt/β-Catenin Signaling Pathway

Vacuolar protein sorting 45 (VPS45) has recently been implicated in the development of ovarian cancer and non-small cell lung cancer. However, its role in the onset and progression of hepatocellular carcinoma (HCC) remains unclear. This study aims to elucidate the function of VPS45 in HCC. Bioassays were conducted to assess the prognostic significance of VPS45 in HCC. Techniques such as western blotting and real-time quantitative polymerase chain reaction (qRT-PCR) were used to confirm the expression levels of VPS45 in HCC tissues and cell lines, as well as to evaluate the expression of downstream effectors in its potential tumorigenic pathways. The impact of VPS45 on HCC cell invasion, proliferation, and migration was assessed using the Cell Counting Kit-8 (CCK-8), wound healing, and transwell assays. Furthermore, the effect of VPS45 on HCC tumorigenesis in vivo was evaluated through subcutaneous tumor formation assays in BALB/c nude mice. VPS45 is markedly overexpressed in both HCC tissues and cell lines. Its expression escalates with advancing tumor grade and clinical stage, and high VPS45 levels are indicative of poor prognosis. In vitro experiments revealed that VPS45 overexpression significantly boosts HCC cell proliferation, migration, and invasion. Conversely, VPS45 knockdown hindered HCC progression in vivo. Investigation into pathway protein expression suggests that VPS45 facilitates HCC progression through its involvement in the Wnt/β-catenin signaling pathway. The overexpression of VPS45 contributes to the development of malignant phenotypes in HCC cells, resulting in a poor prognosis. Targeting VPS45 may offer a viable therapeutic strategy for managing HCC.

Nanomedicine innovations in colon and rectal cancer: advances in targeted drug and gene delivery systems

Nanotechnology has revolutionized cancer diagnostics and therapy, offering unprecedented possibilities to overcome the constraints of conventional treatments. This study provides a detailed overview of the current progress and difficulties in the creation of nanostructured materials, with a specific emphasis on their use in drug and gene delivery systems. The study examines tactics that attempt to improve the effectiveness and safety of chemotherapeutic drugs such as doxorubicin (Dox) by focusing on the potential of antibody-drug conjugates and functionalized nanoparticles. Moreover, it clarifies the challenges encountered in administering nanoparticles orally for gastrointestinal treatments, emphasizing the crucial physicochemical properties that affect their behavior in the gastrointestinal system. This study highlights the transformational potential of nanostructured materials in precision oncology by examining advanced breakthroughs such cell membrane-camouflaged nanoparticles and inorganic nanoparticles designed for gastrointestinal disorders. The text investigates the processes involved in the absorption of nanoparticles and their destruction in lysosomes, revealing the many methods in which enterocytes take up these particles. This study strongly supports the use of advanced nanoparticle-based methods to reduce the harmful effects on the whole body and improve the effectiveness of therapy, based on a thorough examination of current experiments on animals and humans. The main objective of this paper is to provide a fundamental comprehension that will stimulate more investigation and practical use in the field of cancer nanomedicine, advancing its boundaries.

Wnt/β-catenin pathway activation is associated with glucocorticoid secretion in adrenocortical carcinoma, but not directly with immune cell infiltration

Background

In advanced adrenocortical carcinoma (ACC), the response rate to immune checkpoint inhibition (ICI) is only ~15%. Glucocorticoid (GC) secretion and the activation of the Wnt/β-catenin pathway have been suggested to contribute to low tumour immune cell infiltration. The transcription factor lymphoid enhancer factor 1 (LEF-1) transduces β-catenin (CTNNB1)-mediated transcriptional activation.

Objective

To understand the contribution of Wnt/β-catenin pathway activation and glucocorticoid receptor (GR) signalling to the immunologically cold ACC tumour microenvironment.

Methods

Semi-quantitative immunohistochemistry (IHC) of β-catenin (CTNNB1), LEF-1, GR and T cell markers CD3, CD4, CD8, Fox P3 in 59 ACC samples. Targeted RNA expression analysis of 354 immune-related genes in 58 additional ACC tissue specimens. Correlative analyses with clinical data.

Results

Nuclear LEF-1 and CTNNB1 protein expression were positively correlated in ACC tissue (Pearson R2 = 0.1283, p=0.0046). High, moderate and low protein expression was detected in 24.1%, 53.2% and 19.3% of samples for LEF-1, and 30.6%, 43.5% and 19.3% for CTNNB1, respectively. We found higher LEF-1 expression in GC-secreting tumours which did not differ from inactive tumours in terms of GR expression. T cell markers, as evaluated by IHC, were not associated with expression of Wnt/β-catenin pathway markers. At RNA level, tumours with high LEF-1 expression showed significant downregulation of 37 transcripts (including 8 involved in antigen presentation). High LEF-1 expression levels correlated with worse overall survival in this cohort. This was not the case for CTNNB1 and GR.

Conclusion

Lef-1 expression is useful as a biomarker of activated Wnt/β-catenin signalling in ACC. Wnt/β-catenin pathway activation was not associated with reduced immune cell markers in ACC but GC secretion and may be related to tumoural antigen presentation.

Uncovering Phenotypic Expansion in AXIN2-Related Disorders through Precision Animal Modeling

Heterozygous pathogenic variants in AXIN2 are associated with oligodontia-colorectal cancer syndrome (ODCRCS), a disorder characterized by oligodontia, colorectal cancer, and in some cases, sparse hair and eyebrows. We have identified four individuals with one of two de novo , heterozygous variants (NM_004655.4:c.196G>A, p.(Glu66Lys) and c.199G>A, p.(Gly67Arg)) in AXIN2 whose presentations expand the phenotype of AXIN2-related disorders. In addition to ODCRCS features, these individuals have global developmental delay, microcephaly, and limb, ophthalmologic, and renal abnormalities. Structural modeling of these variants suggests that they disrupt AXIN2 binding to tankyrase, which regulates AXIN2 levels through PARsylation and subsequent proteasomal degradation. To test whether these variants produce a phenotype in vivo , we utilized an innovative prime editing N1 screen to phenotype heterozygous (p.E66K) mouse embryos, which were perinatal lethal with short palate and skeletal abnormalities, contrary to published viable Axin2 null mouse models. Modeling of the p.E66K variant in the Drosophila wing revealed gain-of-function activity compared to reference AXIN2. However, the variant showed loss-of-function activity in the fly eye compared to reference AXIN2, suggesting that the mechanism by which p.E66K affects AXIN2 function is cell context-dependent. Together, our studies in humans, mice, and flies demonstrate that specific variants in the tankyrase-binding domain of AXIN2 are pathogenic, leading to phenotypic expansion with context-dependent effects on AXIN2 function and WNT signaling. Moreover, the modeling strategies used to demonstrate variant pathogenicity may be beneficial for the resolution of other de novo heterozygous variants of uncertain significance associated with congenital anomalies in humans.

Wnt signalosomes: What we know that we do not know

Signaling through the Wnt/β-catenin pathway is relayed through three multiprotein complexes: (1) the membrane-associated signalosome, which includes the activated Wnt receptors, (2) the cytoplasmic destruction complex that regulates turnover of the transcriptional coactivator β-catenin, and (3) the nuclear enhanceosome that mediates pathway-specific transcription. Recent discoveries have revealed that Wnt receptor activities are tightly regulated to maintain proper tissue homeostasis and that aberrant receptor upregulation enhances Wnt signaling to drive tumorigenesis, highlighting the importance of signalosome control. These studies have focused on the detailed process by which Wnt ligands engage their coreceptors, LRP5/6 and Frizzled. However, the components that constitute the signalosome and the regulation of their assembly remain undefined. In this review, we discuss Wnt/β-catenin signalosome composition and the mechanisms that regulate signalosome assembly, including the role of biomolecular condensates and ubiquitylation. We also summarize the evidence for the presence of Wnt ligand-independent signalosome formation.

Emerging regulatory mechanisms and functions of biomolecular condensates: implications for therapeutic targets

Cells orchestrate their processes through complex interactions, precisely organizing biomolecules in space and time. Recent discoveries have highlighted the crucial role of biomolecular condensates-membrane-less assemblies formed through the condensation of proteins, nucleic acids, and other molecules-in driving efficient and dynamic cellular processes. These condensates are integral to various physiological functions, such as gene expression and intracellular signal transduction, enabling rapid and finely tuned cellular responses. Their ability to regulate cellular signaling pathways is particularly significant, as it requires a careful balance between flexibility and precision. Disruption of this balance can lead to pathological conditions, including neurodegenerative diseases, cancer, and viral infections. Consequently, biomolecular condensates have emerged as promising therapeutic targets, with the potential to offer novel approaches to disease treatment. In this review, we present the recent insights into the regulatory mechanisms by which biomolecular condensates influence intracellular signaling pathways, their roles in health and disease, and potential strategies for modulating condensate dynamics as a therapeutic approach. Understanding these emerging principles may provide valuable directions for developing effective treatments targeting the aberrant behavior of biomolecular condensates in various diseases.

Ankylosing spondylitis: From pathogenesis to therapy

Ankylosing spondylitis (AS) is an autoimmune rheumatic disease that primarily affects the axial joints, with its etiology complex and still not fully understood. The unknown pathogenesis of AS limits the development of treatment strategies, so keeping up-to-date with the current research on AS can help in searching for potential therapeutic targets. In addition to the classic HLA-B27 genetic susceptibility and Th17-related inflammatory signals, increasing research is focusing on the influence of autoantigen-centered autoimmune responses and bone stromal cells on the onset of AS. Autoantigens derived from gut microbiota and preferential TCR both exacerbate the autoimmune response in patients with AS. Furthermore, dysregulated bone metabolism also promotes pathological new bone formation in AS. Current treatments approved for AS almost focus on the management of inflammation with inconsistent treatment results due to the heterogeneity of patients. In this review, we systematically summarized various pathogenesis and management of AS, meanwhile discussed the underlying risk factors and potential therapeutic targets.

Aberrant Wnt/β-catenin signaling in the mesenchymal stem cells of LZTFL1-depleted mice leads to increased adipogenesis, with implications for obesity

Obesity is one of the main clinical characteristics associated with the heterogeneous genetic disorder Bardet-Biedl syndrome (BBS). Leucine zipper transcription factor like 1 (LZTFL1) is a member of the BBS gene family. Our work showed that Lztfl1knockout (LZKO) mice display the obesity phenotype as early as 3 months of age. Mesenchymal stem cells (MSCs) are multipotent stem cells that can differentiate into various cell types, including adipocytes. To understand the role of LZTFL1 in adipogenesis, we analyzed MSCs isolated from LZKO mouse compact bones (CB-MSCs). Compared to wildtype (WT), LZKO CB-MSCs had elongated primary cilia with tapered tips and increased levels of peroxisome proliferator-activated receptor γ (PPARγ), a key transcription factor that favors adipogenesis, and nuclear glucocorticoid receptor (GR), a transcription factor involved in Pparg activation. Also, LZKO CB-MSCs had a lower level of total β-catenin, a core factor of the antiadipogenic canonical Wnt/b-catenin signaling pathway involved in limiting the nuclear localization of GR. Interaction between caveolin1 (CAV1) and LRP6, the main receptor for canonical Wnt signaling, is known to be critical for Wnt pathway activation and β-catenin stabilization. Compared to WT cells, LZKO cells had elevated total, cell-surface, and lipid-raft-associated LRP6 and reduced CAV1, strongly indicating alterations in the components of the Wnt-signaling pathway. We show that in the absence of LZTFL1, adipogenesis-restraining Wnt/β-catenin signaling is inhibited, and adipogenesis-favorable factors are stimulated in CB-MSCs, leading to enhanced adipogenesis. Evidence provided here could help in understanding the mechanism and molecular basis of obesity in LZTFL1-defective patients.

Cilia as Wnt signaling organelles

Cilia and Wnt signaling have a complex relationship, wherein Wnt regulates cilia and, conversely, cilia may affect Wnt signaling. Recently, it was shown that Wnt receptors are present in flagella, primary cilia, and multicilia, where they transmit an intraciliary signal that is independent of β-catenin. Intraciliary Wnt signaling promotes ciliogenesis, affecting male fertility, adipogenesis, and mucociliary clearance. Wnt also stimulates the beating of motile cilia, highlighting that these nanomotors, too, are chemosensory. Intraciliary Wnt signaling employs a Wnt-protein phosphatase 1 (PP1) signaling axis, involving the canonical Wnt pathway's inhibition of glycogen synthase kinase 3 (GSK3) to repress PP1 activity. Collectively, these findings support that cilia are Wnt signaling organelles, with implications for ciliopathies and cancer.

Evaluation of LRP6, SFRP3, and DVL1 Protein Concentrations in Serum of Patients with Gastroenteropancreatic or Bronchopulmonary Neuroendocrine Tumors

Introduction: Neuroendocrine tumors are a diverse group of tumors predominantly found in the gastrointestinal tract or respiratory system. Methods: This retrospective study aimed to measure the serum concentrations of LRP6 (low-density lipoprotein receptor-related protein 6), SFRP3 (secreted frizzled-related protein 3), and DVL1 (segment polarity protein dishevelled homolog) using the ELISA method in patients with NETs (N = 80) and a control group (N = 62). We evaluated the results against various demographic, clinicopathological, and biochemical characteristics. Results: Our analyses revealed that the concentration of SFRP3 in patients with neuroendocrine tumors was significantly elevated (p < 0.001) compared to the control group. Additionally, DVL1 concentrations were significantly higher (p < 0.01) in patients with BP-NETs compared to GEP-NETs. Furthermore, DVL1 analysis showed a moderate negative correlation with chromogranin A (p < 0.001) and weak negative correlations with serotonin (p < 0.05) and 5-HIAA (p < 0.05). Significant negative correlations were also observed between DVL1 and age in the control group (p < 0.01), and between LRP6 and Ki-67 in the study group. Conclusions: These results suggest that changes in the SFRP3 and DVL1 pathways play a key role in NET development. Elevated levels of these proteins highlight their importance in tumor biology, with SFRP3 and DVL1 potentially being crucial in NET molecular mechanisms. Further research is needed to explore their roles and potential in diagnosis and treatment.

The Role and Mechanism of TRIM Proteins in Gastric Cancer

Tripartite motif (TRIM) family proteins, distinguished by their N-terminal region that includes a Really Interesting New Gene (RING) domain with E3 ligase activity, two B-box domains, and a coiled-coil region, have been recognized as significant contributors in carcinogenesis, primarily via the ubiquitin-proteasome system (UPS) for degrading proteins. Mechanistically, these proteins modulate a variety of signaling pathways, including Wnt/β-catenin, PI3K/AKT, and TGF-β/Smad, contributing to cellular regulation, and also impact cellular activities through non-signaling mechanisms, including modulation of gene transcription, protein degradation, and stability via protein-protein interactions. Currently, growing evidence indicates that TRIM proteins emerge as potential regulators in gastric cancer, exhibiting both tumor-suppressive and oncogenic roles. Given their critical involvement in cellular processes and the notable challenges of gastric cancer, exploring the specific contributions of TRIM proteins to this disease is necessary. Consequently, this review elucidates the roles and mechanisms of TRIM proteins in gastric cancer, emphasizing their potential as therapeutic targets and prognostic factors.

Endogenous oligomer formation underlies DVL2 condensates and promotes Wnt/β-catenin signaling

Activation of the Wnt/β-catenin pathway crucially depends on the polymerization of dishevelled 2 (DVL2) into biomolecular condensates. However, given the low affinity of known DVL2 self-interaction sites and its low cellular concentration, it is unclear how polymers can form. Here, we detect oligomeric DVL2 complexes at endogenous protein levels in human cell lines, using a biochemical ultracentrifugation assay. We identify a low-complexity region (LCR4) in the C-terminus whose deletion and fusion decreased and increased the complexes, respectively. Notably, LCR4-induced complexes correlated with the formation of microscopically visible multimeric condensates. Adjacent to LCR4, we mapped a conserved domain (CD2) promoting condensates only. Molecularly, LCR4 and CD2 mediated DVL2 self-interaction via aggregating residues and phenylalanine stickers, respectively. Point mutations inactivating these interaction sites impaired Wnt pathway activation by DVL2. Our study discovers DVL2 complexes with functional importance for Wnt/β-catenin signaling. Moreover, we provide evidence that DVL2 condensates form in two steps by pre-oligomerization via high-affinity interaction sites, such as LCR4, and subsequent condensation via low-affinity interaction sites, such as CD2.

Structural and Functional Insights into Dishevelled-Mediated Wnt Signaling

Dishevelled (DVL) proteins precisely control Wnt signaling pathways with many effectors. While substantial research has advanced our understanding of DVL's role in Wnt pathways, key questions regarding its regulatory mechanisms and interactions remain unresolved. Herein, we present the recent advances and perspectives on how DVL regulates signaling. The experimentally determined conserved domain structures of DVL in conjunction with AlphaFold-predicted structures are used to understand the DVL's role in Wnt signaling regulation. We also summarize the role of DVL in various diseases and provide insights into further directions for research on the DVL-mediated signaling mechanisms. These findings underscore the importance of DVL as a pharmaceutical target or biological marker in diseases, offering exciting potential for future biomedical applications.

Carboxy-terminal polyglutamylation regulates signaling and phase separation of the Dishevelled protein

Polyglutamylation is a reversible posttranslational modification that is catalyzed by enzymes of the tubulin tyrosine ligase-like (TTLL) family. Here, we found that TTLL11 generates a previously unknown type of polyglutamylation that is initiated by the addition of a glutamate residue to the free C-terminal carboxyl group of a substrate protein. TTLL11 efficiently polyglutamylates the Wnt signaling protein Dishevelled 3 (DVL3), thereby changing the interactome of DVL3. Polyglutamylation increases the capacity of DVL3 to get phosphorylated, to undergo phase separation, and to act in the noncanonical Wnt pathway. Both carboxy-terminal polyglutamylation and the resulting reduction in phase separation capacity of DVL3 can be reverted by the deglutamylating enzyme CCP6, demonstrating a causal relationship between TTLL11-mediated polyglutamylation and phase separation. Thus, C-terminal polyglutamylation represents a new type of posttranslational modification, broadening the range of proteins that can be modified by polyglutamylation and providing the first evidence that polyglutamylation can modulate protein phase separation.

Wnt/β-catenin signaling pathway: proteins' roles in osteoporosis and cancer diseases and the regulatory effects of natural compounds on osteoporosis

Osteoblasts are mainly derived from mesenchymal stem cells in the bone marrow. These stem cells can differentiate into osteoblasts, which have the functions of secreting bone matrix, promoting bone formation, and participating in bone remodeling. The abnormality of osteoblasts can cause a variety of bone-related diseases, including osteoporosis, delayed fracture healing, and skeletal deformities. In recent years, with the side effects caused by the application of PTH drugs, biphosphonate drugs, and calmodulin drugs, people have carried out more in-depth research on the mechanism of osteoblast differentiation, and are actively looking for natural compounds for the treatment of osteoporosis. The Wnt/β-catenin signaling pathway is considered to be one of the important pathways of osteoblast differentiation, and has become an important target for the treatment of osteoporosis. The Wnt/β-catenin signaling pathway, whether its activation is enhanced or its expression is weakened, will cause a variety of diseases including tumors. This review will summarize the effect of Wnt/β-catenin signaling pathway on osteoblast differentiation and the correlation between the related proteins in the pathway and human diseases. At the same time, the latest research progress of natural compounds targeting Wnt/β-catenin signaling pathway against osteoporosis is summarized.

International Union of Basic and Clinical Pharmacology CXV: The Class F of G Protein-Coupled Receptors

The class F of G protein-coupled receptors (GPCRs) consists of 10 Frizzleds (FZD1-10) and Smoothened (SMO). FZDs bind and are activated by secreted lipoglycoproteins of the Wingless/Int-1 (WNT) family, and SMO is indirectly activated by the Hedgehog (Hh) family of morphogens acting on the transmembrane protein Patched. The advance of our understanding of FZDs and SMO as dynamic transmembrane receptors and molecular machines, which emerged during the past 14 years since the first-class F GPCR IUPHAR nomenclature report, justifies an update. This article focuses on the advances in molecular pharmacology and structural biology providing new mechanistic insight into ligand recognition, receptor activation mechanisms, signal initiation, and signal specification. Furthermore, class F GPCRs continue to develop as drug targets, and novel technologies and tools such as genetically encoded biosensors and CRISP/Cas9 edited cell systems have contributed to refined functional analysis of these receptors. Also, advances in crystal structure analysis and cryogenic electron microscopy contribute to the rapid development of our knowledge about structure-function relationships, providing a great starting point for drug development. Despite the progress, questions and challenges remain to fully understand the complexity of the WNT/FZD and Hh/SMO signaling systems. SIGNIFICANCE STATEMENT: The recent years of research have brought about substantial functional and structural insight into mechanisms of activation of Frizzleds and Smoothened. While the advance furthers our mechanistic understanding of ligand recognition, receptor activation, signal specification, and initiation, broader opportunities emerge that allow targeting class F GPCRs for therapy and regenerative medicine employing both biologics and small molecule compounds.

Methylarginine targeting chimeras for lysosomal degradation of intracellular proteins

A paradigm shift in drug development is the discovery of small molecules that harness the ubiquitin-proteasomal pathway to eliminate pathogenic proteins. Here we provide a modality for targeted protein degradation in lysosomes. We exploit an endogenous lysosomal pathway whereby protein arginine methyltransferases (PRMTs) initiate substrate degradation via arginine methylation. We developed a heterobifunctional small molecule, methylarginine targeting chimera (MrTAC), that recruits PRMT1 to a target protein for induced degradation in lysosomes. MrTAC compounds degraded substrates across cell lines, timescales and doses. MrTAC degradation required target protein methylation for subsequent lysosomal delivery via microautophagy. A library of MrTAC molecules exemplified the generality of MrTAC to degrade known targets and neo-substrates-glycogen synthase kinase 3β, MYC, bromodomain-containing protein 4 and histone deacetylase 6. MrTAC selectively degraded target proteins and drove biological loss-of-function phenotypes in survival, transcription and proliferation. Collectively, MrTAC demonstrates the utility of endogenous lysosomal proteolysis in the generation of a new class of small molecule degraders.

Exploring DIX-DIX Homo- and Hetero-Oligomers in Wnt Signaling with AlphaFold2

Wnt signaling is involved in embryo development and cancer. The binding between the DIX domains of Axin1/2, Dishevelled1/2/3, and Coiled-coil-DIX1 is essential for Wnt/β-catenin signaling. Structural and biological studies have revealed that DIX domains are polymerized through head-to-tail interface interactions, which are indispensable for activating β-catenin Wnt signaling. Although different isoforms of Dvl and Axin proteins display both redundant and specific functions in Wnt signaling, the specificity of DIX-mediated interactions remains unclear due to technical challenges. Using AlphaFold2(AF2), we predict the structures of 6 homodimers and 22 heterodimers of DIX domains without templates and compare them with the reported X-ray complex structures. PRODIGY is used to calculate the binding affinities of these DIX complexes. Our results show that the Axin2 DIX homodimer has a stronger binding affinity than the Axin1 DIX homodimer. Among Dishevelled (Dvl) proteins, the binding affinity of the Dvl1 DIX homodimer is stronger than that of Dvl2 and Dvl3. The Coiled-coil-DIX1(Ccd1) DIX homodimer shows weaker binding than the Axin1 DIX homodimer. Generally, heterodimer interactions tend to be stronger than those of homodimers. Our findings provide insights into the mechanism of the Wnt signaling pathway and highlight the potential of AF2 and PRODIGY for studying protein-protein interactions in signaling pathways.

Structural insights into the Caprin-2 HR1 domain in canonical Wnt signaling

The canonical Wnt signaling pathway plays crucial roles in cell fate decisions as well as in pathogenesis of various diseases. Previously, we reported Caprin-2 as a new regulator of canonical Wnt signaling through a mechanism of facilitating LRP5/6 phosphorylation. Here, we resolved the crystal structure of the N-terminal homologous region 1 (HR1) domain of human Caprin-2. HR1 domain is so far only observed in Caprin-2 and its homologous protein Caprin-1, and the function of this domain remains largely mysterious. Here, the structure showed that HR1 domain of human Caprin-2 forms a homo-dimer and exhibits an overall structure roughly resembling the appearance of a pair of scissors. Moreover, we found that residues R200 and R201, which located at a basic cluster within the N-terminal "blades" region, are critical for Caprin-2's localization to the plasma membrane. In line with this, mutations targeting these two residues decrease Caprin-2's activity in the canonical Wnt signaling. Overall, we characterized a previously unknown "scissors"-like structure of the full-length HR1 domain and revealed its function in mediating Caprin-2's localization to the plasma membrane.

Class-Wide Analysis of Frizzled-Dishevelled Interactions Using BRET Biosensors Reveals Functional Differences among Receptor Paralogs

Wingless/Int-1 (WNT) signaling is mediated by WNT binding to 10 Frizzleds (FZD1-10), which propagate the signal inside the cell by interacting with different transducers, most prominently the phosphoprotein Dishevelled (DVL). Despite recent progress, questions about WNT/FZD selectivity and paralog-dependent differences in the FZD/DVL interaction remain unanswered. Here, we present a class-wide analysis of the FZD/DVL interaction using the DEP domain of DVL as a proxy in bioluminescence resonance energy transfer (BRET) techniques. Most FZDs engage in a constitutive high-affinity interaction with DEP. Stimulation of unimolecular FZD/DEP BRET sensors with different ligands revealed that most paralogs are dynamic in the FZD/DEP interface, showing distinct profiles in terms of ligand selectivity and signal kinetics. This study underlines mechanistic differences in terms of how allosteric communication between FZDs and their main signal transducer DVL occurs. Moreover, the unimolecular sensors represent the first receptor-focused biosensors to surpass the requirements for high-throughput screening, facilitating FZD-targeted drug discovery.

Non-coding RNAs in hepatocellular carcinoma metastasis: Remarkable indicators and potential oncogenic mechanism

Non-coding RNAs (ncRNAs), as key regulators involving in intercellular biological processes, are more prominent in many malignancies, especially for hepatocellular carcinoma (HCC). Herein, we conduct a comprehensive review to summarize diverse ncRNAs roles in HCC metastatic mechanism. We focus on four signaling pathways that predominate in HCC metastatic process, including Wnt/β-catenin, HIF-1α, IL-6, and TGF-β pathways. MicroRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) employed different mechanisms to participate in the regulation of the key genes in these pathways, typical as interaction with DNA to control transcription, with RNA to control translation, and with protein to control stability. Therefore, ncRNAs may become potential biomarkers and therapeutic targets for HCC metastasis.

The importance of the circRNA/Wnt axis in gliomas: Biological functions and clinical opportunities

Gliomas are among the most common cancers in the central nervous system, arising through various signaling pathways. One significant pathway is Wnt signaling, a tightly regulated process that plays a crucial role in gliomagenesis and development. The current study aims to explore the relationship between circular RNAs (circRNAs) and the Wnt/β-catenin signaling pathway in gliomas, considering the growing recognition of circRNAs in disease pathogenesis. A comprehensive review of recent research was conducted to investigate the roles of circRNAs in gliomas, focusing on their expression patterns and interactions with the Wnt signaling pathway. The analysis included studies examining circRNAs' function as microRNA sponges and their impact on glioma biology. The findings reveal that circRNAs are differentially expressed in gliomas and significantly influence the occurrence, growth, and metastasis of these tumors. Specifically, circRNAs interact with the Wnt signaling pathway, affecting glioma development and progression. This interaction highlights the importance of circRNAs in glioma pathophysiology. Understanding the regulatory network involving circRNAs and Wnt signaling offers valuable insights into glioma pathophysiology. CircRNAs hold promise as diagnostic and prognostic biomarkers and may serve as targets for novel therapeutic strategies in glioma treatment.

Positive cooperativity in synergistic activation of Wnt proteins

BACKGROUND

Wnt proteins are crucial for embryonic development, stem cell growth, and tissue regeneration. Wnt signaling pathway is activated when Wnt proteins bind to cell membrane receptors.

METHODS AND RESULTS

We employed a luciferase reporter assay in HEK293STF cells to measure Wnt protein-induced signaling. We observed that Wnt3a uniquely promotes the Wnt/β-catenin pathway through positive cooperativity. Additionally, MFH-ND, a molecular mimic of Wnt ligands, markedly increased Wnt3a-induced signaling in a dose-responsive manner. This suggests that various Wnt ligands can synergistically enhance Wnt pathway activation.

CONCLUSIONS

The study suggests the likelihood of various Wnt ligands coexisting in a single signalosome on the cell membrane, providing new insights into the complexities of Wnt signaling mechanisms.

Coxsackievirus A10 impairs nail regeneration and induces onychomadesis by mimicking DKK1 to attenuate Wnt signaling

Coxsackievirus A10 (CV-A10) infection, a prominent cause of childhood hand-foot-and-mouth disease (HFMD), frequently manifests with the intriguing phenomenon of onychomadesis, characterized by nail shedding. However, the underlying mechanism is elusive. Here, we found that CV-A10 infection in mice could suppress Wnt/β-catenin signaling by restraining LDL receptor-related protein 6 (LRP6) phosphorylation and β-catenin accumulation and lead to onychomadesis. Mechanistically, CV-A10 mimics Dickkopf-related protein 1 (DKK1) to interact with Kringle-containing transmembrane protein 1 (KRM1), the CV-A10 cellular receptor. We further found that Wnt agonist (GSK3β inhibitor) CHIR99021 can restore nail stem cell differentiation and protect against nail shedding. These findings provide novel insights into the pathogenesis of CV-A10 and related viruses in onychomadesis and guide prognosis assessment and clinical treatment of the disease.

GSK3 regulation Wnt/β-catenin signaling affects adipogenesis in bovine skeletal muscle fibro/adipogenic progenitors

Clarifying the cellular origin and regulatory mechanisms of intramuscular fat (IMF) deposition is crucial for improving beef quality. Here, we used single-nucleus RNA sequencing to analyze the structure and heterogeneity of skeletal muscle cell populations in different developmental stages of Yanbian cattle and identified eight cell types in two developmental stages of calves and adults. Among them, fibro/adipogenic progenitors (FAPs) expressing CD29 (ITGA7)pos and CD56 (NCAM1)neg surface markers were committed to IMF deposition in beef cattle and expressed major Wnt ligands and receptors. LY2090314/XAV-939 was used to activate/inhibit Wnt/β-catenin signal. The results showed that the blockade of Glycogen Synthase Kinase 3 (GSK3) by LY2090314 promoted the stabilization of β-catenin and reduced the expression of genes related adipogenic differentiation (e.g., PPARγ and C/EBPα) in bovine FAPs, confirming the anti-adipogenic effect of GSK3. XAV-939 inhibition of the Wnt/β-catenin pathway promoted the lipid accumulation capacity of FAPs. Furthermore, we found that blocking GSK3 enhanced the paracrine effects of FAPs-MuSCs and increased myotube formation in muscle satellite cells (MuSCs). Overall, our results outline a single-cell atlas of skeletal muscle development in Yanbian cattle, revealed the role of Wnt/GSK3/β-catenin signaling in FAPs adipogenesis, and provide a theoretical basis for further regulation of bovine IMF deposition.

Therapeutic approaches and novel antifibrotic agents in renal fibrosis: A comprehensive review

Renal fibrosis (RF) is one of the underlying pathological conditions leading to progressive loss of renal function and end-stage renal disease (ESRD). Over the years, various therapeutic approaches have been explored to combat RF and prevent ESRD. Despite significant advances in understanding the underlying molecular mechanism(s), effective therapeutic interventions for RF are limited. Current therapeutic strategies primarily target these underlying mechanisms to halt or reverse fibrotic progression. Inhibition of transforming growth factor-β (TGF-β) signaling, a pivotal mediator of RF has emerged as a central strategy to manage RF. Small molecules, peptides, and monoclonal antibodies that target TGF-β receptors or downstream effectors have demonstrated potential in preclinical models. Modulating the renin-angiotensin system and targeting the endothelin system also provide established approaches for controlling fibrosis-related hemodynamic changes. Complementary to pharmacological strategies, lifestyle modifications, and dietary interventions contribute to holistic management. This comprehensive review aims to summarize the underlying mechanisms of RF and provide an overview of the therapeutic strategies and novel antifibrotic agents that hold promise in its treatment.

Physalis Calyx seu Fructus inhibited pulmonary fibrosis through regulating Wnt/β-catenin signaling pathway

BACKGROUND

Pulmonary fibrosis is a chronic and advancing interstitial lung disease, and there is an urgent need for novel agents for its therapy. Physalis Calyx seu Fructus (PCF) has been utilized in traditional Chinese medicine to treat respiratory disorders with a long history, however, the therapeutic effect and mechanism of PCF against pulmonary fibrosis are still unclear.

PURPOSE

To assess therapeutic efficacy and underlying mechanism of 75 % ethanol extract of PCF (PCF-EtOH) against pulmonary fibrosis, as well as to discover active constituents in PCF.

METHODS

A bleomycin-stimulated mice model was established to assess potential therapy of PCF-EtOH against pulmonary fibrosis in vivo. A lipopolysaccharide-induced inflammatory model in RAW 264.7 cells and a transforming growth factor β1-induced fibrosis model in MRC-5 cells were established to assess potential therapy and mechanisms of purified constituents in PCF-EtOH. UPLC-MS/MS analysis was adopted to ascertain the constituents of PCF-EtOH. Network pharmacology was employed to forecast targets of PCF against pulmonary fibrosis.

RESULTS

PCF-EtOH ameliorated bleomycin-induced pulmonary fibrosis through repressing inflammatory response and extracellular matrix deposition. Meanwhile, PCF-EtOH inhibited Wnt/β-catenin pathway through decreasing β-catenin nuclear accumulation and promoting phosphorylation. Furthermore, withanolides and flavonoids were presumed to be main active compounds of PCF against pulmonary fibrosis based on the network pharmacology. Importantly, we found an extensive presence of withanolides in PCF-EtOH. Physapubescin, a typical withanolide in PCF-EtOH, inhibited the inflammatory response, extracellular matrix deposition, and Wnt/β-catenin pathway. Notably, physapubescin demonstrated a more potent antifibrotic effect than pirfenidone, a clinically approved antifibrotic drug, in the tested model.

CONCLUSION

Withanolides and flavonoids are responsible for the inhibitory effect of PCF-EtOH against pulmonary fibrosis. Withanolides may represent a class of promising therapeutic agents against pulmonary fibrosis, and an in-depth exploration is warranted to validate this proposition.

Wnt/β-catenin signaling components and mechanisms in bone formation, homeostasis, and disease

Wnts are secreted, lipid-modified proteins that bind to different receptors on the cell surface to activate canonical or non-canonical Wnt signaling pathways, which control various biological processes throughout embryonic development and adult life. Aberrant Wnt signaling pathway underlies a wide range of human disease pathogeneses. In this review, we provide an update of Wnt/β-catenin signaling components and mechanisms in bone formation, homeostasis, and diseases. The Wnt proteins, receptors, activators, inhibitors, and the crosstalk of Wnt signaling pathways with other signaling pathways are summarized and discussed. We mainly review Wnt signaling functions in bone formation, homeostasis, and related diseases, and summarize mouse models carrying genetic modifications of Wnt signaling components. Moreover, the therapeutic strategies for treating bone diseases by targeting Wnt signaling, including the extracellular molecules, cytosol components, and nuclear components of Wnt signaling are reviewed. In summary, this paper reviews our current understanding of the mechanisms by which Wnt signaling regulates bone formation, homeostasis, and the efforts targeting Wnt signaling for treating bone diseases. Finally, the paper evaluates the important questions in Wnt signaling to be further explored based on the progress of new biological analytical technologies.

Wnt signaling in cell adhesion, development, and colon cancer

Wnt signaling is essential for embryonic development, influencing processes such as axis formation, cell proliferation and differentiation, cell fate decisions, and axon guidance. It also plays a role in maintaining tissue homeostasis in adult organisms. The loss of normal cell polarity and adhesion caused by Wnt signaling activation is a fundamental step for tumor progression and metastasis. Activating the canonical Wnt pathway is a driving force in many human cancers, especially colorectal, hepatocellular, and mammary carcinomas. Wnt causes the stabilization and nuclear transport of newly synthesized transcriptional regulator β-catenin. The generally accepted view is that the canonical effects of Wnt growth factors are caused by the transcription of β-catenin target genes. Here, we review recent findings that indicate Wnt is a regulator of many other cellular physiological activities, such as macropinocytosis, endosome trafficking, protein stability, focal adhesions, and lysosomal activity. Some of these regulatory responses occur within minutes and do not require new protein synthesis, indicating that there is much more to Wnt beyond the well-established transcriptional role of β-catenin. The main conclusion that emerges from these studies is that in basal cell conditions, the activity of the key protein kinase GSK3, which is inhibited by Wnt pathway activation, normally represses the actin machinery that orchestrates macropinocytosis with implications in cancer. These contributions expand our understanding of the multifaceted roles of Wnt signaling in cellular processes, development, and cancer, providing insights into potential therapeutic targets and strategies.

E3 ubiquitin ligase Deltex facilitates the expansion of Wingless gradient and antagonizes Wingless signaling through a conserved mechanism of transcriptional effector Armadillo/β-catenin degradation

The Wnt/Wg pathway controls myriads of biological phenomena throughout the development and adult life of all organisms across the phyla. Thus, an aberrant Wnt signaling is associated with a wide range of pathologies in humans. Tight regulation of Wnt/Wg signaling is required to maintain proper cellular homeostasis. Here, we report a novel role of E3 ubiquitin ligase Deltex in Wg signaling regulation. Drosophila dx genetically interacts with wg and its pathway components. Furthermore, Dx LOF results in a reduced spreading of Wg while its over-expression expands the diffusion gradient of the morphogen. We attribute this change in Wg gradient to the endocytosis of Wg through Dx which directly affects the short- and long-range Wg targets. We also demonstrate the role of Dx in regulating Wg effector Armadillo where Dx down-regulates Arm through proteasomal degradation. We also showed the conservation of Dx function in the mammalian system where DTX1 is shown to bind with β-catenin and facilitates its proteolytic degradation, spotlighting a novel step that potentially modulates Wnt/Wg signaling cascade.

Multifaceted effects of LRP6 in cancer: exploring tumor development, immune modulation and targeted therapies

Low-density lipoprotein receptor (LDLR)-related protein 6 (LRP6), a member of the LDLR superfamily of cell surface receptors, is most widely known as a crucial co-receptor in the activation of canonical Wnt/β-catenin signaling. This signaling pathway is implicated in multiple biological processes, such as lipoprotein metabolism, protease regulation, cell differentiation, and migration. LRP6 is frequently overexpressed in a variety of tumors, including liver cancer, colorectal cancer, and prostate cancer, and is generally considered an oncogene that promotes tumor proliferation, migration, and invasion. However, there are exceptions; some studies have reported that LRP6 inhibits lung metastasis of breast cancer through its ectodomain (LRP6N), and patients with low LRP6 expression tend to have a poor prognosis. Thus, the role of LRP6 in tumors remains controversial. Although limited studies have shown that LRP6 is associated with the expression and roles of a variety of immune cells in tumors, the interaction of LRP6 with the tumor microenvironment (TME) is not fully understood. Furthermore, it is crucial to acknowledge that LRP6 can engage with alternative pathways, including the mTORC1, CXCL12/CXCR4, and KRAS signaling pathways mentioned earlier, resulting in the regulation of biological functions independent of canonical Wnt/β-catenin signaling. Due to the potential of LRP6 as a molecular target for cancer therapy, various treatment modalities have been developed to directly or indirectly inhibit LRP6 function, demonstrating promising anti-cancer effects across multiple cancer types. This review will concentrate on exploring the expression, function, and potential therapeutic applications of LRP6 in different cancer types, along with its influence on the TME.

Wnt/β-catenin signaling pathway in carcinogenesis and cancer therapy

The Wnt/β-catenin signaling pathway plays a crucial role in various physiological processes, encompassing development, tissue homeostasis, and cell proliferation. Under normal physiological conditions, the Wnt/β-catenin signaling pathway is meticulously regulated. However, aberrant activation of this pathway and downstream target genes can occur due to mutations in key components of the Wnt/β-catenin pathway, epigenetic modifications, and crosstalk with other signaling pathways. Consequently, these dysregulations contribute significantly to tumor initiation and progression. Therapies targeting the Wnt/β-catenin signaling transduction have exhibited promising prospects and potential for tumor treatment. An increasing number of medications targeting this pathway are continuously being developed and validated. This comprehensive review aims to summarize the latest advances in our understanding of the role played by the Wnt/β-catenin signaling pathway in carcinogenesis and targeted therapy, providing valuable insights into acknowledging current opportunities and challenges associated with targeting this signaling pathway in cancer research and treatment.

Ileal Crohn's Disease Exhibits Reduced Activity of Phospholipase C-β3-Dependent Wnt/β-Catenin Signaling Pathway

Crohn's disease is a chronic, debilitating, inflammatory bowel disease. Here, we report a critical role of phospholipase C-β3 (PLC-β3) in intestinal homeostasis. In PLC-β3-deficient mice, exposure to oral dextran sodium sulfate induced lethality and severe inflammation in the small intestine. The lethality was due to PLC-β3 deficiency in multiple non-hematopoietic cell types. PLC-β3 deficiency resulted in reduced Wnt/β-catenin signaling, which is essential for homeostasis and the regeneration of the intestinal epithelium. PLC-β3 regulated the Wnt/β-catenin pathway in small intestinal epithelial cells (IECs) at transcriptional, epigenetic, and, potentially, protein-protein interaction levels. PLC-β3-deficient IECs were unable to respond to stimulation by R-spondin 1, an enhancer of Wnt/β-catenin signaling. Reduced expression of PLC-β3 and its signature genes was found in biopsies of patients with ileal Crohn's disease. PLC-β regulation of Wnt signaling was evolutionally conserved in Drosophila. Our data indicate that a reduction in PLC-β3-mediated Wnt/β-catenin signaling contributes to the pathogenesis of ileal Crohn's disease.

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.

The interplay between Wnt signaling pathways and microtubule dynamics

Wnt signaling pathways represent an evolutionarily highly conserved, intricate network of molecular interactions that regulates various aspects of cellular behavior, including embryonic development and tissue homeostasis. Wnt signaling pathways share the β-catenin-dependent (canonical) and the multiple β-catenin-independent (non-canonical) pathways. These pathways collectively orchestrate a wide range of cellular processes through distinct mechanisms of action. Both the β-catenin-dependent and β-catenin-independent pathways are closely intertwined with microtubule dynamics, underscoring the complex crosstalk between Wnt signaling and the cellular cytoskeleton. This interplay involves several mechanisms, including how the components of Wnt signaling can influence the stability, organization, and distribution of microtubules. The modulation of microtubule dynamics by Wnt signaling plays a crucial role in coordinating cellular behaviors and responses to external signals. In this comprehensive review, we discussed the current understanding of how Wnt signaling and microtubule dynamics intersect in various aspects of cellular behavior. This study provides insights into our understanding of these crucial cellular processes.

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.

The scaffold protein AXIN1: gene ontology, signal network, and physiological function

AXIN1, has been initially identified as a prominent antagonist within the WNT/β-catenin signaling pathway, and subsequently unveiled its integral involvement across a diverse spectrum of signaling cascades. These encompass the WNT/β-catenin, Hippo, TGFβ, AMPK, mTOR, MAPK, and antioxidant signaling pathways. The versatile engagement of AXIN1 underscores its pivotal role in the modulation of developmental biological signaling, maintenance of metabolic homeostasis, and coordination of cellular stress responses. The multifaceted functionalities of AXIN1 render it as a compelling candidate for targeted intervention in the realms of degenerative pathologies, systemic metabolic disorders, cancer therapeutics, and anti-aging strategies. This review provides an intricate exploration of the mechanisms governing mammalian AXIN1 gene expression and protein turnover since its initial discovery, while also elucidating its significance in the regulation of signaling pathways, tissue development, and carcinogenesis. Furthermore, we have introduced the innovative concept of the AXIN1-Associated Phosphokinase Complex (AAPC), where the scaffold protein AXIN1 assumes a pivotal role in orchestrating site-specific phosphorylation modifications through interactions with various phosphokinases and their respective substrates.

R-spondin-1 induces Axin degradation via the LRP6-CK1ε axis

R-spondins (RSPOs) are secreted signaling molecules that potentiate the Wnt/β-catenin pathway by cooperating with Wnt ligands. RSPO1 is crucial in tissue development and tissue homeostasis. However, the molecular mechanism by which RSPOs activate Wnt/β-catenin signaling remains elusive. In this study, we found that RSPOs could mediate the degradation of Axin through the ubiquitin-proteasome pathway. The results of Co-IP showed that the recombinant RSPO1 protein promoted the interaction between Axin1 and CK1ε. Either knockout of the CK1ε gene or treatment with the CK1δ/CK1ε inhibitor SR3029 caused an increase in Axin1 protein levels and attenuated RSPO1-induced degradation of the Axin1 protein. Moreover, we observed an increase in the number of associations of LRP6 with CK1ε and Axin1 following RSPO1 stimulation. Overexpression of LRP6 further potentiated Axin1 degradation mediated by RSPO1 or CK1ε. In addition, recombinant RSPO1 and Wnt3A proteins synergistically downregulated the protein expression of Axin1 and enhanced the transcriptional activity of the SuperTOPFlash reporter. Taken together, these results uncover the novel mechanism by which RSPOs activate Wnt/β-catenin signaling through LRP6/CK1ε-mediated degradation of Axin.

Curcumin and its Derivatives Targeting Multiple Signaling Pathways to Elicit Anticancer Activity: A Comprehensive Perspective

The uncontrolled growth and spread of aberrant cells characterize the group of disorders known as cancer. According to GLOBOCAN 2022 analysis of cancer patients in either developed countries or developing countries the main concern cancers are breast cancer, lung cancer, and liver cancer which may rise eventually. Natural substances with dietary origins have gained interest for their low toxicity, anti-inflammatory, and antioxidant effects. The evaluation of dietary natural products as chemopreventive and therapeutic agents, the identification, characterization, and synthesis of their active components, as well as the enhancement of their delivery and bioavailability, have all received significant attention. Thus, the treatment strategy for concerning cancers must be significantly evaluated and may include the use of phytochemicals in daily lifestyle. In the present perspective, we discussed one of the potent phytochemicals, that has been used over the past few decades known as curcumin as a panacea drug of the "Cure-all" therapy concept. In our review firstly we included exhausted data from in vivo and in vitro studies on breast cancer, lung cancer, and liver cancer which act through various cancer-targeting pathways at the molecular level. Now, the second is the active constituent of turmeric known as curcumin and its derivatives are enlisted with their targeted protein in the molecular docking studies, which help the researchers design and synthesize new curcumin derivatives with respective implicated molecular and cellular activity. However, curcumin and its substituted derivatives still need to be investigated with unknown targeting mechanism studies in depth.

Resistomycin Inhibits Wnt/β-Catenin Signaling to Induce the Apoptotic Death of Human Colorectal Cancer Cells

Resistomycin is a natural antibiotic related to quinone that has been shown to exhibit robust antitumor activity. To further characterize the mechanistic basis for such activity, human colorectal cancer (CRC) cells were selected as a model to explore the role of Wnt/β-catenin signaling in the ability of resistomycin to induce apoptotic cell death. These analyses revealed that resistomycin was able to suppress β-catenin, TCF4, and GSK-3β expression, together with that of the downstream targets c-Myc and survivin. This coincided with elevated cleaved caspase-3 and Bax protein levels and a decline in Bcl-2 content. When β-catenin was silenced, this further enhanced the ability of resistomycin to induce apoptotic CRC cell death, whereas this apoptotic process was partially ablated when cells were treated using lithium chloride to activate Wnt/β-catenin signaling. Overall, these results support a model wherein resistomycin inhibits Wnt/β-catenin signaling within CRC cells, thereby inducing apoptotic death. Further research may be warranted to better clarify the potential utility of this compound as a candidate drug for use in the treatment of patients suffering from this form of cancer.

The USP46 complex deubiquitylates LRP6 to promote Wnt/β-catenin signaling

The relative abundance of Wnt receptors plays a crucial role in controlling Wnt signaling in tissue homeostasis and human disease. While the ubiquitin ligases that ubiquitylate Wnt receptors are well-characterized, the deubiquitylase that reverses these reactions remains unclear. Herein, we identify USP46, UAF1, and WDR20 (USP46 complex) as positive regulators of Wnt signaling in cultured human cells. We find that the USP46 complex is similarly required for Wnt signaling in Xenopus and zebrafish embryos. We demonstrate that Wnt signaling promotes the association between the USP46 complex and cell surface Wnt coreceptor, LRP6. Knockdown of USP46 decreases steady-state levels of LRP6 and increases the level of ubiquitylated LRP6. In contrast, overexpression of the USP46 complex blocks ubiquitylation of LRP6 by the ubiquitin ligases RNF43 and ZNFR3. Size exclusion chromatography studies suggest that the size of the USP46 cytoplasmic complex increases upon Wnt stimulation. Finally, we show that USP46 is essential for Wnt-dependent intestinal organoid viability, likely via its role in LRP6 receptor homeostasis. We propose a model in which the USP46 complex increases the steady-state level of cell surface LRP6 and facilitates the assembly of LRP6 into signalosomes via a pruning mechanism that removes sterically hindering ubiquitin chains.

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.

Vitamin B6 is governed by the local compartmentalization of metabolic enzymes during growth

Vitamin B6 is a vital micronutrient across cell types and tissues, and dysregulated B6 levels contribute to human disease. Despite its importance, how B6 vitamer levels are regulated is not well understood. Here, we provide evidence that B6 dynamics are rapidly tuned by precise compartmentation of pyridoxal kinase (PDXK), the rate-limiting B6 enzyme. We show that canonical Wnt rapidly led to the accumulation of inactive B6 by shunting cytosolic PDXK into lysosomes. PDXK was modified with methyl-arginine Degron (MrDegron), a protein tag for lysosomes, which enabled delivery via microautophagy. Hyperactive lysosomes resulted in the continuous degradation of PDXK and B6 deficiency that promoted proliferation in Wnt-driven colorectal cancer (CRC) cells. Pharmacological or genetic disruption of the coordinated MrDegron proteolytic pathway was sufficient to reduce CRC survival in cells and organoid models. In sum, this work contributes to the repertoire of micronutrient-regulated processes that enable cancer cell growth and provides insight into the functional impact of B6 deficiencies for survival.

FAT4 overexpression promotes antitumor immunity by regulating the β-catenin/STT3/PD-L1 axis in cervical cancer

BACKGROUND

FAT4 (FAT Atypical Cadherin 4) is a member of the cadherin-associated protein family, which has been shown to function as a tumor suppressor by inhibiting proliferation and metastasis. The Wnt/β-catenin pathway activation is highly associated with PD-L1-associated tumor immune escape. Here, we report the mechanism by which FAT4 overexpression regulates anti-tumor immunity in cervical cancer by inhibiting PD-L1 N-glycosylation and cell membrane localization in a β-catenin-dependent manner.

METHODS

FAT4 expression was first detected in cervical cancer tissues and cell lines. Cell proliferation, clone formation, and immunofluorescence were used to determine the tumor suppressive impact of FAT4 overexpression in vitro, and the findings were confirmed in immunodeficient and immunocomplete mice xenografts. Through functional and mechanistic experiments in vivo and in vitro, we investigated how FAT4 overexpression affects the antitumor immunity via the β-catenin/STT3/PD-L1 axis.

RESULTS

FAT4 is downregulated in cervical cancer tissues and cell lines. We determined that FAT4 binds to β-catenin and antagonizes its nuclear localization, promotes phosphorylation and degradation of β-catenin by the degradation complexes (AXIN1, APC, GSK3β, CK1). FAT4 overexpression decreases programmed death-ligand 1 (PD-L1) mRNA expression at the transcriptional level, and causes aberrant glycosylation of PD-L1 via STT3A at the post-translational modifications (PTMs) level, leading to its endoplasmic reticulum (ER) accumulation and polyubiquitination-dependent degradation. We found that FAT4 overexpression promotes aberrant PD-L1 glycosylation and degradation in a β-catenin-dependent manner, thereby increasing cytotoxic T lymphocyte (CTL) activity in immunoreactive mouse models.

CONCLUSIONS

These findings address the basis of Wnt/β-catenin pathway activation in cervical cancer and provide combination immunotherapy options for targeting the FAT4/β-catenin/STT3/PD-L1 axis. Schematic cartoons showing the antitumor immunity mechanism of FAT4. (left) when Wnts bind to their receptors, which are made up of Frizzled proteins and LRP5/6, the cytoplasmic protein DVL is activated, inducing the aggregation of degradation complexes (AXIN, GSK3β, CK1, APC) to the receptor. Subsequently, stable β-catenin translocates into the nucleus and binds to TCF/LEF and TCF7L2 transcription factors, leading to target genes transcription. The catalytically active subunit of oligosaccharyltransferase, STT3A, enhances PD-L1 glycosylation, and N-glycosylated PD-L1 translocates to the cell membrane via the ER-to-Golgi pathway, resulting in immune evasion. (Right) FAT4 exerts antitumor immunity mainly through following mechanisms: (i) FAT4 binds to β-catenin and antagonizes its nuclear localization, promotes phosphorylation and degradation of β-catenin by the degradation complexes (AXIN1, APC, GSK3β, CK1); (ii) FAT4 inhibits PD-L1 and STT3A transcription in a β-catenin-dependent manner and induces aberrant PD-L1 glycosylation and ubiquitination-dependent degradation; (iii) Promotes activation of cytotoxic T lymphocytes (CTL) and infiltration into the tumor microenvironment.