Type 2 diabetes mellitus (T2DM) is one of the major chronic diseases, whose prevalence is increasing dramatically worldwide and can lead to a range of serious complications. Wnt ligands (Wnts) and ...their activating Wnt signalling pathways are closely involved in the regulation of various processes that are important for the occurrence and progression of T2DM and related complications. However, our understanding of their roles in these diseases is quite rudimentary due to the numerous family members of Wnts and conflicting effects via activating the canonical and/or non‐canonical Wnt signalling pathways. In this review, we summarize the current findings on the expression pattern and exact role of each human Wnt in T2DM and related complications, including Wnt1, Wnt2, Wnt2b, Wnt3, Wnt3a, Wnt4, Wnt5a, Wnt5b, Wnt6, Wnt7a, Wnt7b, Wnt8a, Wnt8b, Wnt9a, Wnt9b, Wnt10a, Wnt10b, Wnt11 and Wnt16. Moreover, the role of main antagonists (sFRPs and WIF‐1) and coreceptor (LRP6) of Wnts in T2DM and related complications and main challenges in designing Wnt‐based therapeutic approaches for these diseases are discussed. We hope a deep understanding of the mechanistic links between Wnt signalling pathways and diabetic‐related diseases will ultimately result in a better management of these diseases.
Alzheimer's disease (AD) is the most common neurodegenerative disorder and the most frequent cause of dementia in the aged population. According to the amyloid hypothesis, the amyloid‐β (Aβ) peptide ...plays a key role in the pathogenesis of AD. Aβ is generated from the amyloidogenic processing of amyloid precursor protein and can aggregate to form oligomers, which have been described as a major synaptotoxic agent in neurons. Dysfunction of Wnt signaling has been linked to increased Aβ formation; however, several other studies have argued against this possibility. Herein, we use multiple experimental approaches to confirm that the inhibition of Wnt signaling promoted the amyloidogenic proteolytic processing of amyloid precursor protein. We also demonstrate that inhibiting Wnt signaling increases the production of the Aβ42 peptide, the Aβ42/Aβ40 ratio, and the levels of Aβ oligomers such as trimers and tetramers. Moreover, we show that activating Wnt signaling reduces the levels of Aβ42 and its aggregates, increases Aβ40 levels, and reduces the Aβ42/Aβ40 ratio. Finally, we show that the protective effects observed in response to activation of the Wnt pathway rely on β‐catenin‐dependent transcription, which is demonstrated experimentally via the expression of various ‘mutant forms of β‐catenin’. Together, our findings indicate that loss of the Wnt signaling pathway may contribute to the pathogenesis of AD.
Wnt signaling plays key roles in Alzheimer's disease (AD). We proposed a positive feedback between Wnt and Aβ production. Activation of signaling favored non‐amyloidogenic APP processing and decreases the Aβ42 concentration, activating the Wnt target genes transcription that continue repressing the Aβ42 formation. Inhibition of Wnt pathway induced amyloidogenic APP processing and high Aβ42 levels, which in turn triggers signaling dysfunction. In summary, Wnt signaling dysfunction could contribute to Aβ generation in AD.
Wnt proteins are secreted glycoproteins that regulate multiple processes crucial to the development and tissue homeostasis of multicellular organisms, including tissue patterning, proliferation, cell ...fate specification, cell polarity and migration. To elicit these effects, Wnts act as autocrine as well as paracrine signalling molecules between Wnt-producing and Wnt-receiving cells. More than 40 years after the discovery of the Wg/Wnt pathway, it is still unclear how they are transported to fulfil their paracrine signalling functions. Several mechanisms have been proposed to mediate intercellular Wnt transport, including Wnt-binding proteins, lipoproteins, exosomes and cytonemes. In this Review, we describe the evidence for each proposed mechanism, and discuss how they may contribute to Wnt dispersal in tissue-specific and context-dependent manners, to regulate embryonic development precisely and maintain the internal steady state within a defined tissue.
The WNT signal transduction cascade is a main regulator of development throughout the animal kingdom. Wnts are also key drivers of most types of tissue stem cells in adult mammals. Unsurprisingly, ...mutated Wnt pathway components are causative to multiple growth-related pathologies and to cancer. Here, we describe the core Wnt/β-catenin signaling pathway, how it controls stem cells, and contributes to disease. Finally, we discuss strategies for Wnt-based therapies.
The WNT pathway, a key regulator of development and stem cell function throughout the animal kingdom, is linked to a number of growth-related pathologies and to cancer.
Gliomas comprise heterogeneous malignant glial and stromal cells. While blood vessel co-option is a potential mechanism to escape anti-angiogenic therapy, the relevance of glial phenotype in this ...process is unclear. We show that Olig2+ oligodendrocyte precursor-like glioma cells invade by single-cell vessel co-option and preserve the blood-brain barrier (BBB). Conversely, Olig2-negative glioma cells form dense perivascular collections and promote angiogenesis and BBB breakdown, leading to innate immune cell activation. Experimentally, Olig2 promotes Wnt7b expression, a finding that correlates in human glioma profiling. Targeted Wnt7a/7b deletion or pharmacologic Wnt inhibition blocks Olig2+ glioma single-cell vessel co-option and enhances responses to temozolomide. Finally, Olig2 and Wnt7 become upregulated after anti-VEGF treatment in preclinical models and patients. Thus, glial-encoded pathways regulate distinct glioma-vascular microenvironmental interactions.
•Glial phenotype regulates glioma co-option or angiogenesis•Glioma oligodendrocyte-like (OPCL) cells express Wnt7 necessary for co-option•Wnt inhibitors significantly improve survival with temozolomide•Anti-VEGF-treatment of glioma selects for Olig2/Wnt7+ cells
Griveau et al. show that Olig2+ glioma cells invade by single-cell vessel co-option, whereas Olig2− glioma cells promote angiogenesis and that anti-VEGF treatment selects for the Olig2+/Wnt7+ phenotype. Wnt7 is necessary for vessel co-option, and Wnt inhibition enhances the response to temozolomide treatment.
While the cytosolic events of Wnt/β‐catenin signaling (canonical Wnt signaling) pathway have been widely studied, only little is known about the molecular mechanisms involved in Wnt binding to its ...receptors at the plasma membrane. Here, we reveal the influence of the immediate plasma membrane environment on the canonical Wnt–receptor interaction. While the receptors are distributed both in ordered and disordered environments, Wnt binding to its receptors selectively occurs in more ordered membrane environments which appear to cointernalize with the Wnt‐receptor complex. Moreover, Wnt/β‐catenin signaling is significantly reduced when the membrane order is disturbed by specific inhibitors of certain lipids that prefer to localize at the ordered environments. Similarly, a reduction in Wnt signaling activity is observed in Niemann–Pick Type C disease cells where trafficking of ordered membrane lipid components to the plasma membrane is genetically impaired. We thus conclude that ordered plasma membrane environments are essential for binding of canonical Wnts to their receptor complexes and downstream signaling activity.
Heterogeneous plasma membrane organization is crucial for its function. Here, using biochemical and biophysical tools, we show that canonical Wnt binding to its receptor complex occurs preferentially in ordered membrane environments, which are enriched with saturated lipids and cholesterol. These ordered membrane regions are cointernalized with the canonical Wnt‐receptor complex and initiate the β‐catenin‐dependent Wnt signaling.
Non-canonical Wnt signaling (encompassing Wnt/PCP and WntCa2+) has a dual identity in the literature. One stream of research investigates its role in antagonizing canonical Wnt/β-catenin signaling in ...cancer, typically through Ca2+, while the other stream investigates its effect on polarity in development, typically through Vangl2. Rarely do these topics intersect or overlap. What has become clear is that Wnt5a can mobilize intracellular calcium stores to inhibit Wnt/β-catenin in cancer cells but there is no evidence that Vangl2 is involved in this process. Conversely, Wnt5a can independently activate Vangl2 to affect polarity and migration but the role of calcium in this process is also limited. Further, Vangl2 has also been implicated in inhibiting Wnt/β-catenin signaling in development. The consensus is that a cell can differentiate between canonical and non-canonical Wnt signaling when presented with a choice, always choosing non-canonical at the expense of canonical Wnt signaling. However, these are rare events in vivo. Given the shared resources between non-canonical and canonical Wnt signaling it is perplexing that there is not more in vivo evidence for cross talk between these two pathways. In this review we discuss the intersection of non-canonical Wnt, with a focus on Wnt/PCP, and Wnt/β-catenin signaling in an attempt to shed some light on pathways that rarely meet at a crossroads in vivo.
Mammalian sex determination is controlled by the antagonistic interactions of two genetic pathways: The SRY-SOX9-FGF9 network promotes testis determination partly by opposing proovarian pathways, ...while RSPO1/WNT-β-catenin/FOXL2 signals control ovary development by inhibiting SRY-SOX9-FGF9. The molecular basis of this mutual antagonism is unclear. Here we show that ZNRF3, a WNT signaling antagonist and direct target of RSPO1-mediated inhibition, is required for sex determination in mice. XY mice lacking ZNRF3 exhibit complete or partial gonadal sex reversal, or related defects. These abnormalities are associated with ectopic WNT/β-catenin activity and reduced Sox9 expression during fetal sex determination. Using exome sequencing of individuals with 46, XY disorders of sex development, we identified three human ZNRF3 variants in very rare cases of XY female presentation. We tested two missense variants and show that these disrupt ZNRF3 activity in both human cell lines and zebrafish embryo assays. Our data identify a testis-determining function for ZNRF3 and indicate a mechanism of direct molecular interaction between two mutually antagonistic organogenetic pathways.
Wnts are secreted proteins that bind to cell surface receptors to activate downstream signaling cascades. Normal Wnt signaling plays key roles in embryonic development and adult tissue homeostasis. ...The secretion of Wnt ligands, the turnover of Wnt receptors, and the signaling transduction are tightly regulated and fine-tuned to keep the signaling output "just right." Hyperactivated Wnt signaling due to recurrent genetic alterations drives several human cancers. Elevated Wnt signaling also confers resistance to multiple conventional and targeted cancer therapies through diverse mechanisms including maintaining the cancer stem cell population, enhancing DNA damage repair, facilitating transcriptional plasticity, and promoting immune evasion. Different classes of Wnt signaling inhibitors targeting key nodes of the pathway have been developed and show efficacy in treating Wnt-driven cancers and subverting Wnt-mediated therapy resistance in preclinical studies. Several of these inhibitors have advanced to clinical trials, both singly and in combination with other existing US Food and Drug Administration-approved anti-cancer modalities. In the near future, pharmacological inhibition of Wnt signaling may be a real choice for patients with cancer. SIGNIFICANCE STATEMENT: The latest insights in Wnt signaling, ranging from basic biology to therapeutic implications in cancer, are reviewed. Recent studies extend understanding of this ancient signaling pathway and describe the development and improvement of anti-Wnt therapeutic modalities for cancer.
The Wnt-β-catenin signaling pathway is an evolutionarily conserved cell-cell communication system that is important for stem cell renewal, cell proliferation and cell differentiation both during ...embryogenesis and during adult tissue homeostasis. Genetic or epigenetic events leading to hypo- or hyper-activation of the Wnt-β-catenin signaling cascade have also been associated with human diseases such as cancer. Understanding how this pathway functions is thus integral for developing therapies to treat diseases or for regenerative medicine approaches. Here, and in the accompanying poster, we provide an overview of Wnt-β-catenin signaling and briefly highlight its key functions during development and adult tissue homeostasis.
PDF
