A Wnt/Calcium Signaling Cascade Regulates Neuronal Excitability and Trafficking of NMDARs

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.

Nobiletin regulates intracellular Ca2+ levels via IP3R and ameliorates neuroinflammation in Aβ42-induced astrocytes

Astrocytes are the major glial cells in the human brain and provide crucial metabolic and trophic support to neurons. The amyloid-β peptide (Aβ) alter the morphological and functional properties of astrocytes and induce inflammation and calcium dysregulation, contributing to Alzheimer's disease (AD) pathology. Recent studies highlight the role of Toll-like receptor (TLR) 4/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling in inflammation. Reactive oxygen species (ROS) generated due to Aβ, induce apoptosis in the brain cells worsening AD progression. Astrocytic cell surface receptors, such as purinergic receptors (P2Y1 and P2Y2), metabotropic glutamate receptor (mGLUR)5, α7 nicotinic acetylcholine receptor (α7nAChR), and N-methyl-d-aspartate receptors (NMDARs), have been suggested to interact with inositol trisphosphate receptor (IP3R) on the endoplasmic reticulum (ER) to induce Ca2+ movement from ER to cytoplasm, causing Ca2+ dysregulation. We found that the citrus flavonoid nobiletin (NOB) protected primary astrocytes from Aβ42-induced cytotoxicity and inhibited TLR4/NF-κB signaling in Aβ42-induced primary rat astrocytes. NOB was found to regulate Aβ42-induced ROS levels through Keap1-Nrf2 pathway. The receptors P2Y1, P2Y2, mGLUR5, α7nAChR, and NMDARs induced intracellular Ca2+ levels by activating IP3R and NOB regulated them, thereby regulating intracellular Ca2+ levels. Molecular docking analysis revealed a possible interaction between NOB and IP3R in IP3R regulation. Furthermore, RNA sequencing revealed various NOB-mediated biological signaling pathways, such as the AD-presenilin, AD-amyloid secretase, and Wnt signaling pathway, suggesting possible neuroprotective roles of NOB. To conclude, NOB is a promising therapeutic agent for AD and works by modulating AD pathology at various levels in Aβ42-induced primary rat astrocytes.

The multifaceted role of Wnt canonical signalling in neurogenesis, neuroinflammation, and hyperexcitability in mesial temporal lobe epilepsy

Epilepsy is a neurological disorder characterised by unprovoked, repetitive seizures caused by abnormal neuronal firing. The Wnt/β-Catenin signalling pathway is involved in seizure-induced neurogenesis, aberrant neurogenesis, neuroinflammation, and hyperexcitability associated with epileptic disorder. Wnt/β-Catenin signalling is crucial for early brain development processes including neuronal patterning, synapse formation, and N-methyl-d-aspartate receptor (NMDAR) regulation. Disruption of molecular networks such as Wnt/β-catenin signalling in epilepsy could offer encouraging anti-epileptogenic targets. So, with a better understanding of the canonical Wnt/-Catenin pathway, we highlight in this review the important elements of Wnt/-Catenin signalling specifically in Mesial Temporal Lobe Epilepsy (MTLE) for potential therapeutic targets.

The emerging understanding of Frizzled receptors

The Wnt signaling pathway is a huge network governing development and homeostasis, dysregulation of which is associated with a myriad of human diseases. The Frizzled receptor (FZD) family comprises receptors for Wnt ligands, which indispensably mediate Wnt signaling jointly with a variety of co-receptors. Studies of FZDs have revealed that 10 FZD subtypes play diverse roles in physiological processes. At the same time, dysregulation of FZDs is also responsible for various diseases, in particular human cancers. Enormous attention has been paid to the molecular understanding and targeted therapy of FZDs in the past decade. In this review, we summarize the latest research on FZD structure, function, regulation and targeted therapy, providing a basis for guiding future research in this field.

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.

Canonical and noncanonical Wnt signaling: Multilayered mediators, signaling mechanisms and major signaling crosstalk

Wnt signaling plays a major role in regulating cell proliferation and differentiation. The Wnt ligands are a family of 19 secreted glycoproteins that mediate their signaling effects via binding to Frizzled receptors and LRP5/6 coreceptors and transducing the signal either through β-catenin in the canonical pathway or through a series of other proteins in the noncanonical pathway. Many of the individual components of both canonical and noncanonical Wnt signaling have additional functions throughout the body, establishing the complex interplay between Wnt signaling and other signaling pathways. This crosstalk between Wnt signaling and other pathways gives Wnt signaling a vital role in many cellular and organ processes. Dysregulation of this system has been implicated in many diseases affecting a wide array of organ systems, including cancer and embryological defects, and can even cause embryonic lethality. The complexity of this system and its interacting proteins have made Wnt signaling a target for many therapeutic treatments. However, both stimulatory and inhibitory treatments come with potential risks that need to be addressed. This review synthesized much of the current knowledge on the Wnt signaling pathway, beginning with the history of Wnt signaling. It thoroughly described the different variants of Wnt signaling, including canonical, noncanonical Wnt/PCP, and the noncanonical Wnt/Ca2+ pathway. Further description involved each of its components and their involvement in other cellular processes. Finally, this review explained the various other pathways and processes that crosstalk with Wnt signaling.

ROR2 homodimerization is sufficient to activate a neuronal Wnt/calcium signaling pathway

Wnt signaling plays a key role in the mature CNS by regulating trafficking of NMDA-type glutamate receptors and intrinsic properties of neurons. The Wnt receptor ROR2 has been identified as a necessary component of the neuronal Wnt5a/Ca2+ signaling pathway that regulates synaptic and neuronal function. Since ROR2 is considered a pseudokinase, its mechanism for downstream signaling upon ligand binding has been controversial. It has been suggested that its role is to function as a coreceptor of a G-protein-coupled Wnt receptor of the Frizzled family. We show that chemically induced homodimerization of ROR2 is sufficient to recapitulate key signaling events downstream of receptor activation in neurons, including PKC and JNK kinases activation, elevation of somatic and dendritic Ca2+ levels, and increased trafficking of NMDARs to synapses. In addition, we show that homodimerization of ROR2 induces phosphorylation of the receptor on Tyr residues. Point mutations in the conserved but presumed nonfunctional ATP-binding site of the receptor prevent its phosphorylation, as well as downstream signaling. This suggests an active kinase domain. Our results indicate that ROR2 can signal independently of Frizzled receptors to regulate the trafficking of a key synaptic component. Additionally, they suggest that homodimerization can overcome structural conformations that render the tyrosine kinase inactive. A better understanding of ROR2 signaling is crucial for comprehending the regulation of synaptic and neuronal function in normal brain processes in mature animals.

Convergence of Calcium Channel Regulation and Mechanotransduction in Skeletal Regenerative Biomaterial Design

Cells are known to perceive their microenvironment through extracellular and intracellular mechanical signals. Upon sensing mechanical stimuli, cells can initiate various downstream signaling pathways that are vital to regulating proliferation, growth, and homeostasis. One such physiologic activity modulated by mechanical stimuli is osteogenic differentiation. The process of osteogenic mechanotransduction is regulated by numerous calcium ion channels-including channels coupled to cilia, mechanosensitive and voltage-sensitive channels, and channels associated with the endoplasmic reticulum. Evidence suggests these channels are implicated in osteogenic pathways such as the YAP/TAZ and canonical Wnt pathways. This review aims to describe the involvement of calcium channels in regulating osteogenic differentiation in response to mechanical loading and characterize the fashion in which those channels directly or indirectly mediate this process. The mechanotransduction pathway is a promising target for the development of regenerative materials for clinical applications due to its independence from exogenous growth factor supplementation. As such, also described are examples of osteogenic biomaterial strategies that involve the discussed calcium ion channels, calcium-dependent cellular structures, or calcium ion-regulating cellular features. Understanding the distinct ways calcium channels and signaling regulate these processes may uncover potential targets for advancing biomaterials with regenerative osteogenic capabilities.

Role of hippocampal Wnt signaling pathways on contextual fear memory reconsolidation

Memories already consolidated when reactivated return to a labile state and can be modified, this process is known as reconsolidation. It is known the Wnt signaling pathways can modulate hippocampal synaptic plasticity as well as learning and memory. Yet, Wnt signaling pathways interact with NMDA (N-methyl-D-aspartate) receptors. However, whether canonical Wnt/β-catenin and non-canonical Wnt/Ca2+ signaling pathways are required in the CA1 region of hippocampus for contextual fear memory reconsolidation remains unclear. So, here we verified that the inhibition of canonical Wnt/β-catenin pathway with DKK1 (Dickkopf-1) into CA1 impaired the reconsolidation of contextual fear conditioning (CFC) memory when administered immediately and 2h after reactivation session but not 6h later, while the inhibition of non-canonical Wnt/Ca²⁺ signaling pathway with SFRP1 (Secreted frizzled-related protein-1) into CA1 immediately after reactivation session had no effect. Moreover, the impairment induced by DKK1 was blocked by the administration of the agonist of the NMDA receptors glycine site, D-Serine, immediately and 2h after reactivation session. We found that hippocampal canonical Wnt/β-catenin is necessary to the reconsolidation of CFC memory at least two hours after reactivation, while non-canonical Wnt/Ca²⁺ signaling pathway is not involved in this process and, that there is a link between Wnt/β-catenin signaling pathway and NMDA receptors. In view of this, this study provides new evidence regarding the neural mechanisms underlying contextual fear memory reconsolidation and contributes to provide a new possible target for the treatment of fear related disorders.

Microglial WNT5A supports dendritic spines maturation and neuronal firing

There is increasing evidence showing that microglia play a critical role in mediating synapse formation and spine growth, although the molecular mechanism remains elusive. Here, we demonstrate that the secreted morphogen WNT family member 5A (WNT5A) is the most abundant WNT expressed in microglia and that it promotes neuronal maturation. Co-culture of microglia with Thy1-YFP+ differentiated neurons significantly increased neuronal spine density and reduced dendritic spine turnover rate, which was diminished by silencing microglial Wnt5a in vitro. Co-cultured microglia increased post-synaptic marker PSD95 and synaptic density as determined by the co-localization of PSD95 with pre-synaptic marker VGLUT2 in vitro. The silencing of Wnt5a expression in microglia partially reduced both PSD95 and synaptic densities. Co-culture of differentiated neurons with microglia significantly enhanced neuronal firing rate as measured by multiple electrode array, which was significantly reduced by silencing microglial Wnt5a at 23 days differentiation in vitro. These findings demonstrate that microglia can mediate spine maturation and regulate neuronal excitability via WNT5A secretion indicating possible pathological roles of dysfunctional microglia in developmental disorders.

How Are Synapses Born? A Functional and Molecular View of the Role of the Wnt Signaling Pathway

Synaptic transmission is a dynamic process that requires precise regulation. Early in life, we must be able to forge appropriate connections (add and remove) to control our behavior. Neurons must recognize appropriate targets, and external soluble factors that activate specific signaling cascades provide the regulation needed to achieve this goal. Wnt signaling has been implicated in several forms of synaptic plasticity, including functional and structural changes associated with brain development. The analysis of synapses from an electrophysiological perspective allows us to characterize the functional role of cellular signaling pathways involved in brain development. The application of quantal theory to principles of developmental plasticity offers the possibility of dissecting the function of structural changes associated with the birth of new synapses as well as the maturation of immature silent synapses. Here, we focus on electrophysiological and molecular evidence that the Wnt signaling pathway regulates glutamatergic synaptic transmission, specifically N-methyl-d-aspartate receptors (NMDARs), to control the birth of new synapses. We also focus on the role of Wnts in the conversion of silent synapses into functional synapses.

Cocaine and Its Abstinence Condition Modulate Striatal and Hippocampal Wnt Signaling in a Male Rat Model of Drug Self-Administration

Recent years have provided more and more evidence confirming the important role of Wnt/β-catenin signaling in the pathophysiology of mental illnesses, including cocaine use disorder. High relapse rates, which is a hallmark of drug addiction, prompt the study of changes in Wnt signaling elements (Wnt5a, Wnt7b, and Ctnnb1) in the motivational aspects of cocaine use and early drug-free period (3 days after the last exposure to cocaine). For this purpose, an animal model of intravenous cocaine self-administration and two types of drug-free period (extinction training and abstinence in the home cage) were used. The studies showed that chronic cocaine self-administration mainly disturbs the expression of Wnt5a and Ctnnb1 (the gene encoding β-catenin) in the examined brain structures (striatum and hippocampus), and the examined types of early abstinence are characterized by a different pattern of changes in the expression of these genes. At the same time, in cocaine self-administrated animals, there were no changes in the level of Wnt5a and β-catenin proteins at the tested time points. Moreover, exposure to cocaine induces a significant reduction in the striatal and hippocampal expression of miR-374 and miR-544, which can regulate Wnt5a levels post-transcriptionally. In summary, previous observations from experimenter-administered cocaine have not been fully validated in the cocaine self-administration model. Yoked cocaine administration appears to disrupt Wnt signaling more than cocaine self-administration. The condition of the cocaine-free period, the routes of drug administration, and the motivational aspect of drug administration play an important role in the type of drug-induced molecular changes observed. Furthermore, in-depth research involving additional brain regions is needed to determine the exact role of Wnt signaling in short-term and long-lasting plasticity as well as in the motivational aspects of cocaine use, and thus to assess its potential as a target for new drug therapy for cocaine use disorder.

Wnt-5a induces the conversion of silent to functional synapses in the hippocampus

Synapse unsilencing is an essential mechanism for experience-dependent plasticity. Here, we showed that the application of the ligand Wnt-5a converts glutamatergic silent synapses into functional ones by increasing both α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) currents (IAMPA and INMDA, respectively). These effects were mimicked by the hexapeptide Foxy-5 and inhibited by secreted frizzled-related protein sFRP-2. INMDA potentiation was produced by increased synaptic potency, followed by an increase in the probability of release (Pr), even in the presence of 7-nitro-2,3-dioxo-1,4-dihydroquinoxaline-6-carbonitrile (CNQX). At a longer time of Wnt-5a exposure, the Pr increments were higher in INMDA than in IAMPA. In the presence of NMDAR inhibitors, Wnt-5a-induced conversion was fully inhibited in 69.0% of silent synapses, whereas in the remaining synapses were converted into functional one. Our study findings showed that the Wnt-5a-activated pathway triggers AMPAR insertion into mammalian glutamatergic synapses, unsilencing non-functional synapses and promoting the formation of nascent synapses during the early postnatal development of the brain circuits.

Wnt 5a mediated inflammatory injury of renal tubular epithelial cells dependent on calcium signaling pathway in Trichloroethylene sensitized mice

Patients with trichloroethene-induced Trichloroethylene hypersensitivity syndrome (THS) often present kidney injury. However, the role of Wnt 5a/Ca2+ pathway in renal tubular injury in Trichloroethylene (TCE) sensitized mice remains unclear. This study aimed to investigate how Wnt 5a/Ca2+ pathway induced renal tubular epithelial cell injury in TCE sensitized mice. A total of 84 female BALB/c Specific Pathogen Free mice aged 6-8 weeks were used to establish TCE sensitized mouse models. Renal histology and serum levels of α1-MG and β2-MG were used to assess the renal injury. The renal protein levels of Wnt 5a, ROR2, FZD5, PLC, p-CaMKII, IκB α, p-IκB α, NF-κB(p65), TNF α, IL 6 and IL 1β were measured. The levels of serum α1-MG and β2-MG and TNF α, IL 6 and IL 1β levels in the kidney tissue were significantly increased in TCE sensitized positive group. However, Box5 pretreatment inhibited the expression of PLC, p-CaMKII, p65 and attenuated the injury of renal tubular epithelial cells and suppressed the upregulated expression of the above cytokines. In addition, KN93 also reduced nuclear translocation of p65 and renal injury as well as the elevated cytokines by inhibiting CaMKII. These data identify Wnt 5a binding to ROR2 and FZD5, p65 nuclear translocation, and inflammatory cytokine release as a novel mechanism for renal tubular epithelial cells injury by sensitization with TCE. Box5 or KN93 pretreatment can block the expression of inflammatory cytokines and reduce the injury of renal tubular epithelial cells.

Wnt Signaling Interactor WTIP (Wilms Tumor Interacting Protein) Underlies Novel Mechanism for Cardiac Hypertrophy

BACKGROUND

The study of hypertrophic cardiomyopathy (HCM) can yield insight into the mechanisms underlying the complex trait of cardiac hypertrophy. To date, most genetic variants associated with HCM have been found in sarcomeric genes. Here, we describe a novel HCM-associated variant in the noncanonical Wnt signaling interactor WTIP (Wilms tumor interacting protein) and provide evidence of a role for WTIP in complex disease.

METHODS

In a family affected by HCM, we used exome sequencing and identity-by-descent analysis to identify a novel variant in WTIP (p.Y233F). We knocked down WTIP in isolated neonatal rat ventricular myocytes with lentivirally delivered short hairpin ribonucleic acids and in Danio rerio via morpholino injection. We performed weighted gene coexpression network analysis for WTIP in human cardiac tissue, as well as association analysis for WTIP variation and left ventricular hypertrophy. Finally, we generated induced pluripotent stem cell-derived cardiomyocytes from patient tissue, characterized size and calcium cycling, and determined the effect of verapamil treatment on calcium dynamics.

RESULTS

WTIP knockdown caused hypertrophy in neonatal rat ventricular myocytes and increased cardiac hypertrophy, peak calcium, and resting calcium in D rerio. Network analysis of human cardiac tissue indicated WTIP as a central coordinator of prohypertrophic networks, while common variation at the WTIP locus was associated with human left ventricular hypertrophy. Patient-derived WTIP p.Y233F-induced pluripotent stem cell-derived cardiomyocytes recapitulated cellular hypertrophy and increased resting calcium, which was ameliorated by verapamil.

CONCLUSIONS

We demonstrate that a novel genetic variant found in a family with HCM disrupts binding to a known Wnt signaling protein, misregulating cardiomyocyte calcium dynamics. Further, in orthogonal model systems, we show that expression of the gene WTIP is important in complex cardiac hypertrophy phenotypes. These findings, derived from the observation of a rare Mendelian disease variant, uncover a novel disease mechanism with implications across diverse forms of cardiac hypertrophy.

Deletion of Wnt10a Is Implicated in Hippocampal Neurodegeneration in Mice

The hippocampus plays an important role in maintaining normal cognitive function and is closely associated with the neuropathogenesis of dementia. Wnt signaling is relevant to neuronal development and maturation, synaptic formation, and plasticity. The role of Wnt10a in hippocampus-associated cognition, however, is largely unclear. Here, we examined the morphological and functional alterations in the hippocampus of Wnt10a-knockout (Wnt10a-/-) mice. Neurobehavioral tests revealed that Wnt10a-/- mice exhibited spatial memory impairment and anxiety-like behavior. Immunostaining and Western blot findings showed that the protein expressions of β-catenin, brain-derived neurotrophic factor, and doublecortin were significantly decreased and that the number of activated microglia increased, accompanied by amyloid-β accumulation, synaptic dysfunction, and microglia-associated neuroinflammation in the hippocampi of Wnt10a-/- mice. Our findings revealed that the deletion of Wnt10a decreased neurogenesis, impaired synaptic function, and induced hippocampal neuroinflammation, eventually leading to hippocampal neurodegeneration and memory deficit, possibly through the β-catenin signaling pathway, providing a novel insight into preventive approaches for hippocampus-dependent cognitive impairment.

GPR177 in A-fiber sensory neurons drives diabetic neuropathic pain via WNT-mediated TRPV1 activation

Diabetic neuropathic pain (DNP) is a common and devastating complication in patients with diabetes. The mechanisms mediating DNP are not completely elucidated, and effective treatments are lacking. A-fiber sensory neurons have been shown to mediate the development of mechanical allodynia in neuropathic pain, yet the molecular basis underlying the contribution of A-fiber neurons is still unclear. Here, we report that the orphan G protein-coupled receptor 177 (GPR177) in A-fiber neurons drives DNP via WNT5a-mediated activation of transient receptor potential vanilloid receptor-1 (TRPV1) ion channel. GPR177 is mainly expressed in large-diameter A-fiber dorsal root ganglion (DRG) neurons and required for the development of DNP in mice. Mechanistically, we found that GPR177 mediated the secretion of WNT5a from A-fiber DRG neurons into cerebrospinal fluid (CSF), which was necessary for the maintenance of DNP. Extracellular perfusion of WNT5a induced rapid currents in both TRPV1-expressing heterologous cells and nociceptive DRG neurons. Computer simulations revealed that WNT5a has the potential to bind the residues at the extracellular S5-S6 loop of TRPV1. Using a peptide able to disrupt the predicted WNT5a/TRPV1 interaction suppressed DNP- and WNT5a-induced neuropathic pain symptoms in rodents. We confirmed GPR177/WNT5A coexpression in human DRG neurons and WNT5A secretion in CSF from patients with DNP. Thus, our results reveal a role for WNT5a as an endogenous and potent TRPV1 agonist, and the GPR177-WNT5a-TRPV1 axis as a driver of DNP pathogenesis in rodents. Our findings identified a potential analgesic target that might relieve neuropathic pain in patients with diabetes.

Dishevelled coordinates phosphoinositide kinases PI4KIIIα and PIP5KIγ for efficient PtdInsP2 synthesis

Phosphatidylinositol(4,5)-bisphosphate (PtdInsP2) is an important modulator of many cellular processes, and its abundance in the plasma membrane is closely regulated. We examined the hypothesis that members of the Dishevelled scaffolding protein family can bind the lipid kinases phosphatidylinositol 4-kinase (PI4K) and phosphatidylinositol 4-phosphate 5-kinase (PIP5K), facilitating synthesis of PtdInsP2 directly from phosphatidylinositol. We used several assays for PtdInsP2 to examine the cooperative function of phosphoinositide kinases and the Dishevelled protein Dvl3 in the context of two receptor signaling cascades. Simultaneous overexpression of PI4KIIIα (also known as PI4KA) and PIP5KIγ (also known as PIP5K1C) had a synergistic effect on PtdInsP2 synthesis that was recapitulated by overexpression of Dvl3. Increasing the activity of Dvl3 by overexpression increased resting plasma membrane PtdInsP2. Knockdown of Dvl3 reduced resting plasma membrane PtdInsP2 and slowed PtdInsP2 resynthesis following receptor activation. We confirm that Dvl3 promotes coupling of PI4KIIIα and PIP5KIγ and show that this interaction is essential for efficient resynthesis of PtdInsP2 following receptor activation.

Loss of IRF2BPL impairs neuronal maintenance through excess Wnt signaling

De novo truncations in Interferon Regulatory Factor 2 Binding Protein Like (IRF2BPL) lead to severe childhood-onset neurodegenerative disorders. To determine how loss of IRF2BPL causes neural dysfunction, we examined its function in Drosophila and zebrafish. Overexpression of either IRF2BPL or Pits, the Drosophila ortholog, represses Wnt transcription in flies. In contrast, neuronal depletion of Pits leads to increased wingless (wg) levels in the brain and is associated with axonal loss, whereas inhibition of Wg signaling is neuroprotective. Moreover, increased neuronal expression of wg in flies is sufficient to cause age-dependent axonal loss, similar to reduction of Pits. Loss of irf2bpl in zebrafish also causes neurological defects with an associated increase in wnt1 transcription and downstream signaling. WNT1 is also increased in patient-derived astrocytes, and pharmacological inhibition of Wnt suppresses the neurological phenotypes. Last, IRF2BPL and the Wnt antagonist, CKIα, physically and genetically interact, showing that IRF2BPL and CkIα antagonize Wnt transcription and signaling.

Local Wnt signalling in the asymmetric migrating vertebrate cells

Wnt signalling is known to generate cellular asymmetry via Wnt/planar cell polarity pathway (Wnt/PCP). Wnt/PCP acts locally (i) to orient membrane polarity and asymmetric establishment of intercellular junctions via conserved set of PCP proteins most specifically represented by Vangl and Prickle, and (ii) to asymmetrically rearrange cytoskeletal structures via downstream effectors of Dishevelled (Dvl). This process is best described on stable phenotypes of epithelial cells. Here, however, we review the activity of Wnt signalling in migratory cells which experience the extensive rearrangements of cytoskeleton and consequently dynamic asymmetry, making the localised effects of Wnt signalling easier to distinguish. Firstly, we focused on migration of neuronal axons, which allows to study how the pre-existent cellular asymmetry can influence Wnt signalling outcome. Then, we reviewed the role of Wnt signalling in models of mesenchymal migration including neural crest, melanoma, and breast cancer cells. Last, we collected evidence for local Wnt signalling in amoeboid cells, especially lymphocytes. As the outcome of this review, we identify blank spots in our current understanding of this topic, propose models that synthesise the current observations and allow formulation of testable hypotheses for the future research.

Yap Promotes Noncanonical Wnt Signals From Cardiomyocytes for Heart Regeneration

[Figure: see text].

GSK-3β inhibitor TWS119 alleviates hypoxic-ischemic brain damage via a crosstalk with Wnt and Notch signaling pathways in neonatal rats

Preterm infant brain injury is a leading cause of morbidity and disability in survivors of preterm infants. Unfortunately, the effective treatment remains absent. Recent evidence suggests that GSK-3β inhibitor TWS119 has a neuroprotectiverole in adult brain injury by activation of Wnt/β-catenin signaling pathway. However, the role on neonatal brain injury is not yet explored. The study aims to evaluate the effect of TWS119 at 7 d after hypoxic-ischemic brain damage and investigate the mechanism that it regulates Wnt and Notch signaling pathways at 24 h after hypoxic-ischemic brain damage in neonatal rats. Three-day-old rats were randomly divided into 3 groups: sham group, HI group and TWS119 group. The neonatal rats were subjected to left carotid artery ligation followed by 2 h of hypoxia (8.0% O₂). A single dose of TWS119 (30 mg/kg) was intraperitoneally injected 20 min prior to hypoxia-ischemia (HI). At 7 d after HI, TWS119 improved the tissue structure, reduced cell apoptosis, up-regulated bcl-2 expression, up-regulated the expression of PSD-95 and Synapsin-1. At 24 h after HI, it activated Wnt/β-catenin signaling pathway by up-regulation of β-catenin protein expression and wnt3a/wnt5a/wnt7a mRNA expression. Simultaneously, it suppressed Notch signaling pathway by down-regulation of Notch1 and HES-1 proteins expression. Our study suggested that TWS119 performed a neuroprotective function at 7 d after hypoxic-ischemic brain damage via a crosstalk with Wnt/β-catenin and Notch signaling pathways at 24 h after hypoxic-ischemic brain damage in neonatal rats.

Wnt5a modulates dendritic spine dynamics through the regulation of Cofilin via small Rho GTPase activity in hippocampal neurons

Dendritic spines are small, actin-rich protrusions that act as the receiving sites of most excitatory inputs in the central nervous system. The remodeling of the synapse architecture is mediated by actin cytoskeleton dynamics, a process precisely regulated by the small Rho GTPase family. Wnt ligands exert their presynaptic and postsynaptic effects during formation and consolidation of the synaptic structure. Specifically, Wnt5a has been identified as an indispensable synaptogenic factor for the regulation and organization of the postsynaptic side; however, the molecular mechanisms through which Wnt5a induces morphological changes resulting from actin cytoskeleton dynamics within dendritic spines remain unclear. In this work, we employ primary rat hippocampal cultures and HT22 murine hippocampal neuronal cell models, molecular and pharmacological tools, and fluorescence microscopy (laser confocal and epifluorescence) to define the Wnt5a-induced molecular signaling involved in postsynaptic remodeling mediated via the regulation of the small Rho GTPase family. We report that Wnt5a differentially regulates the phosphorylation of Cofilin in neurons through both Ras-related C3 botulinum toxin substrate 1 and cell division cycle 42 depending on the subcellular compartment and the extracellular calcium levels. Additionally, we demonstrate that Wnt5a increases the density of dendritic spines and promotes their maturation via Ras-related C3 botulinum toxin substrate 1. Accordingly, we find that Wnt5a requires the combined activation of small Rho GTPases to increase the levels of filamentous actin, thus promoting the stability of actin filaments. Altogether, these results provide evidence for a new mechanism by which Wnt5a may target actin dynamics, thereby regulating the subsequent morphological changes in dendritic spine architecture.

The transcriptional landscape of Alzheimer's disease and its association with Wnt signaling pathway

Alzheimer's disease (AD) is a neurological disorder primarily affecting the elderly. The disease manifests as progressive deterioration in cognitive functions, leading to a loss of autonomy. The identification of transcriptional changes in susceptible signaling pathways has provided clues to the origin and progression of AD and has pinpointed synapse loss as the prominent event in early stages of the disease. Synapse failure represents a key pathological correlate of cognitive decline in patients. Genetics and transcriptomics studies have also identified novel genes, processes, and pathways associated with AD. This evidence suggests that a deficiency in Wnt signaling pathway contributes to AD pathogenesis by inducing synaptic dysfunction and neuronal degeneration. In the adult nervous system, Wnt signaling plays a crucial role in synaptic physiology, modulating the synaptic vesicle cycle, trafficking neurotransmitter receptors, and modulating the expression of different genes associated with these processes. In this review, we describe the general transcriptional landscape associated with AD, specifically transcriptional changes associated with the Wnt signaling pathway and their effects in the context of disease.

Wnt-Frizzled Signaling Regulates Activity-Mediated Synapse Formation

The formation of synapses is a tightly regulated process that requires the coordinated assembly of the presynaptic and postsynaptic sides. Defects in synaptogenesis during development or in the adult can lead to neurodevelopmental disorders, neurological disorders, and neurodegenerative diseases. In order to develop therapeutic approaches for these neurological conditions, we must first understand the molecular mechanisms that regulate synapse formation. The Wnt family of secreted glycoproteins are key regulators of synapse formation in different model systems from invertebrates to mammals. In this review, we will discuss the role of Wnt signaling in the formation of excitatory synapses in the mammalian brain by focusing on Wnt7a and Wnt5a, two Wnt ligands that play an in vivo role in this process. We will also discuss how changes in neuronal activity modulate the expression and/or release of Wnts, resulting in changes in the localization of surface levels of Frizzled, key Wnt receptors, at the synapse. Thus, changes in neuronal activity influence the magnitude of Wnt signaling, which in turn contributes to activity-mediated synapse formation.

Deficient LEF1 expression is associated with lithium resistance and hyperexcitability in neurons derived from bipolar disorder patients

Bipolar disorder (BD) is a psychiatric condition characterized by depressive and manic episodes that affect 2% of the world population. The first-line long-term treatment for mood stabilization is lithium (Li). Induced pluripotent stem cell modeling of BD using hippocampal dentate gyrus-like neurons derived from Li-responsive (LR) and Li-non-responsive (NR) patients previously showed neuronal hyperexcitability. Li treatment reversed hyperexcitability only on the LR neurons. In this study we searched for specific targets of Li resistance in NR neurons and found that the activity of Wnt/β-catenin signaling pathway was severely affected, with a significant decrease in expression of LEF1. Li targets the Wnt/β-catenin signaling pathway by inhibiting GSK-3β and releasing β-catenin that forms a nuclear complex with TCF/LEF1, activating the Wnt/β-catenin transcription program. Therefore, we propose that downregulation of LEF1 may account for Li resistance in NR neurons. Our results show that valproic acid (VPA), a drug used to treat NR patients that also acts downstream of GSK-3β, upregulated LEF1 and Wnt/β-catenin gene targets, increased transcriptional activity of complex β-catenin/TCF/LEF1, and reduced excitability in NR neurons. In addition, decreasing LEF1 expression in control neurons using shLEF1 caused hyperexcitability, confirming that the impact of VPA on excitability in NR neurons was connected to changes in LEF1 and in the Wnt/β-catenin pathway. Our results suggest that LEF1 may be a useful target for the discovery of new drugs for BD treatment.

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.

Wnt5a promotes hippocampal postsynaptic development and GluN2B-induced expression via the eIF2α HRI kinase

Wnt signaling plays a key role in neurodevelopment and neuronal maturation. Specifically, Wnt5a stimulates postsynaptic assemblies, increases glutamatergic neurotransmission and, through calcium signaling, generates nitric oxide (NO). Trying to unveil the molecular pathway triggering these postsynaptic effects, we found that Wnt5a treatment induces a time-dependent increases in the length of the postsynaptic density (PSD), elicits novel synaptic contacts and facilitates F-actin flow both in in vitro and ex vivo models. These effects were partially abolished by the inhibition of the Heme-regulated eukaryotic initiation factor 2α (HRI) kinase, a kinase which phosphorylates the initiation translational factor eIF2α. When phosphorylated, eIF2α normally avoids the translation of proteins not needed during stress conditions, in order to avoid unnecessary energetic expenses. However, phosphorylated eIF2α promotes the translation of some proteins with more than one open reading frame in its 5′ untranslated region. One of these proteins targeted by Wnt-HRI-eIF2α mediated translation is the GluN2B subunit of the NMDA receptor. The identified increase in GluN2B expression correlated with increased NMDA receptor function. Considering that NMDA receptors are crucial for excitatory synaptic transmission, the molecular pathway described here contributes to the understanding of the fast and plastic translational mechanisms activated during learning and memory processes.

Comprehending the crosstalk between Notch, Wnt and Hedgehog signaling pathways in oral squamous cell carcinoma - clinical implications

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a malignant oral cavity neoplasm that affects many people, especially in developing countries. Despite several advances that have been made in diagnosis and treatment, the morbidity and mortality rates due to OSCC remain high. Accumulating evidence indicates that aberrant activation of cellular signaling pathways, such as the Notch, Wnt and Hedgehog pathways, occurs during the development and metastasis of OSCC. In this review, we have articulated the roles of the Notch, Wnt and Hedgehog signaling pathways in OSCC and their crosstalk during tumor development and progression. We have also examined possible interactions and associations between these pathways and treatment regimens that could be employed to effectively tackle OSCC and/or prevent its recurrence.

CONCLUSIONS

Activation of the Notch signaling pathway upregulates the expression of several genes, including c-Myc, β-catenin, NF-κB and Shh. Associations between the Notch signaling pathway and other pathways have been shown to enhance OSCC tumor aggressiveness. Crosstalk between these pathways supports the maintenance of cancer stem cells (CSCs) and regulates OSCC cell motility. Thus, application of compounds that block these pathways may be a valid strategy to treat OSCC. Such compounds have already been employed in other types of cancer and could be repurposed for OSCC.

Molecular and Functional Links between Neurodevelopmental Processes and Treatment-Induced Neuroendocrine Plasticity in Prostate Cancer Progression

Simple Summary

Treatment-induced neuroendocrine prostate cancer (t-NEPC) is a subtype of castration-resistant prostate cancer (CRPC) which develops under prolonged androgen deprivation therapy. The mechanisms and pathways underlying the t-NEPC are still poorly understood and there are no effective treatments available. Here, we summarize the literature on the molecules and pathways contributing to neuroendocrine phenotype in prostate cancer in the context of their known cellular neurodevelopmental processes. We also discuss the role of tumor microenvironment in neuroendocrine plasticity, future directions, and therapeutic options under clinical investigation for neuroendocrine prostate cancer.

Abstract

Neuroendocrine plasticity and treatment-induced neuroendocrine phenotypes have recently been proposed as important resistance mechanisms underlying prostate cancer progression. Treatment-induced neuroendocrine prostate cancer (t-NEPC) is highly aggressive subtype of castration-resistant prostate cancer which develops for one fifth of patients under prolonged androgen deprivation. In recent years, understanding of molecular features and phenotypic changes in neuroendocrine plasticity has been grown. However, there are still fundamental questions to be answered in this emerging research field, for example, why and how do the prostate cancer treatment-resistant cells acquire neuron-like phenotype. The advantages of the phenotypic change and the role of tumor microenvironment in controlling cellular plasticity and in the emergence of treatment-resistant aggressive forms of prostate cancer is mostly unknown. Here, we discuss the molecular and functional links between neurodevelopmental processes and treatment-induced neuroendocrine plasticity in prostate cancer progression and treatment resistance. We provide an overview of the emergence of neurite-like cells in neuroendocrine prostate cancer cells and whether the reported t-NEPC pathways and proteins relate to neurodevelopmental processes like neurogenesis and axonogenesis during the development of treatment resistance. We also discuss emerging novel therapeutic targets modulating neuroendocrine plasticity.

WNT Signaling Is a Key Player in Alzheimer's Disease

The cellular processes regulated by WNT signaling have been mainly studied during embryonic development and cancer. In the last two decades, the role of WNT in the adult central nervous system has been the focus of interest in our laboratory. In this chapter, we will be summarized β-catenin-dependent and -independent WNT pathways, then we will be revised WNT signaling function at the pre- and post-synaptic level. Concerning Alzheimer's disease (AD) initially, we found that WNT/β-catenin signaling activation exerts a neuroprotective mechanism against the amyloid β (Αβ) peptide toxicity. Later, we found that WNT/β-catenin participates in Tau phosphorylation and in learning and memory. In the last years, we demonstrated that WNT/β-catenin signaling is instrumental in the amyloid precursor protein (APP) processing and that WNT/β-catenin dysfunction results in Aβ production and aggregation. We highlight the importance of WNT/β-catenin signaling dysfunction in the onset of AD and propose that the loss of WNT/β-catenin signaling is a triggering factor of AD. The WNT pathway is therefore positioned as a therapeutic target for AD and could be a valid concept for improving AD therapy. We think that metabolism and inflammation will be relevant when defining future research in the context of WNT signaling and the neurodegeneration associated with AD.

Chronic ethanol exposure differentially alters neuronal function in the medial prefrontal cortex and dentate gyrus

Alterations in the function of prefrontal cortex (PFC) and hippocampus have been implicated in underlying the relapse to alcohol seeking behaviors in humans and animal models of moderate to severe alcohol use disorders (AUD). Here we used chronic intermittent ethanol vapor exposure (CIE), 21d protracted abstinence following CIE (21d AB), and re-exposure to one vapor session during protracted abstinence (re-exposure) to evaluate the effects of chronic ethanol exposure on basal synaptic function, neuronal excitability and expression of key synaptic proteins that play a role in neuronal excitability in the medial PFC (mPFC) and dentate gyrus (DG). CIE consistently enhanced excitability of layer 2/3 pyramidal neurons in the mPFC and granule cell neurons in the DG. In the DG, this effect persisted during 21d AB. Re-exposure did not enhance excitability, suggesting resistance to vapor-induced effects. Analysis of action potential kinetics revealed that altered afterhyperpolarization, rise time and decay time constants are associated with the altered excitability during CIE, 21d AB and re-exposure. Molecular adaptations that may underlie increases in neuronal excitability under these different conditions were identified. Quantitative polymerase chain reaction of large-conductance potassium (BK) channel subunit mRNA in PFC and DG tissue homogenates did not show altered expression patterns of BK subunits. Western blotting demonstrates enhanced phosphorylation of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), and reduced phosphorylation of glutamate receptor GluN2A/2B subunits. These results suggest a novel relationship between activity of CaMKII and GluN receptors in the mPFC and DG, and neuronal excitability in these brain regions in the context of moderate to severe AUD.

Neuronal defects in a human cellular model of 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11DS) is a highly penetrant and common genetic cause of neuropsychiatric disease. Here we generated induced pluripotent stem cells from 15 individuals with 22q11DS and 15 control individuals and differentiated them into three-dimensional (3D) cerebral cortical organoids. Transcriptional profiling across 100 days showed high reliability of differentiation and revealed changes in neuronal excitability-related genes. Using electrophysiology and live imaging, we identified defects in spontaneous neuronal activity and calcium signaling in both organoid- and 2D-derived cortical neurons. The calcium deficit was related to resting membrane potential changes that led to abnormal inactivation of voltage-gated calcium channels. Heterozygous loss of DGCR8 recapitulated the excitability and calcium phenotypes and its overexpression rescued these defects. Moreover, the 22q11DS calcium abnormality could also be restored by application of antipsychotics. Taken together, our study illustrates how stem cell derived models can be used to uncover and rescue cellular phenotypes associated with genetic forms of neuropsychiatric disease.

Non-pigmented ciliary epithelium derived extracellular vesicles uptake mechanism by the trabecular meshwork

Consistent with increasing findings, extracellular vesicles (EVs), consider as a major constituents of the aqueous humor, have a role as signaling mediators in glaucoma. Following secretion, EVs hold immense promise for utilization as bio-therapeutics and drug delivery vehicles due to their nature as biological nanoparticles that facilitate intercellular molecular transport. Yet, the specific pathway utilizing for transferring signals by EVs in the ocular drainage system is not fully understood. Hence, the objective of this study was to examine internalization mechanisms by which Non-Pigmented Ciliary Epithelium (NPCE)-derived EVs deliver their signals to the Trabecular Meshwork (TM) cells. EVs were isolated and size and concentration were determined. Internalization study of treated EVs with Proteinase-K to achieve removal of surface membrane proteins on EVs was conducted. Energy dependent uptake mechanism was examined under various temperatures. Using uptake inhibitors endocytosis, phagocytosis, and Wnt-TGFβ2 signaling were investigated. TM cells exposed to NPCE EVs demonstrate a significant decrease in the levels of two proteins in two Wnt-TGFb2 signaling proteins levels: p-GSK3β and β-catenin. A significant decrease in the uptake by TM cells of Proteinase-K-treated EVs was found, followed by attenuation of the Wnt-TGFβ2 proteins expression. Energy dependent uptake revealed a significant decrease in EVs internalization. The exposure of TM cells to endocytosis uptake inhibitors abolished the decrease of the Wnt-TGFβ2 proteins levels. Exposure to phagocytosis uptake inhibitor resulted in a partial inhibition of NPCE EVs effect in TM cells. The attenuation of proteins expression levels following uptake inhibitors treatment or EVs membrane proteins removal indicates that Wnt-TGFβ2 signaling in TM cells is mediated through NPCE EVs surface proteins in an active manner that involves endocytosis-dependent routes.

CRELD1 modulates homeostasis of the immune system in mice and humans

CRELD1 is a pivotal factor for heart development, the function of which is unknown in adult life. We here provide evidence that CRELD1 is an important gatekeeper of immune system homeostasis. Exploiting expression variance in large human cohorts contrasting individuals with the lowest and highest CRELD1 expression levels revealed strong phenotypic, functional and transcriptional differences, including reduced CD4⁺ T cell numbers. These findings were validated in T cell-specific Creld1-deficient mice. Loss of Creld1 was associated with simultaneous overactivation and increased apoptosis, resulting in a net loss of T cells with age. Creld1 was transcriptionally and functionally linked to Wnt signaling. Collectively, gene expression variance in large human cohorts combined with murine genetic models, transcriptomics and functional testing defines CRELD1 as an important modulator of immune homeostasis.

Caloric Restriction and Ketogenic Diet Therapy for Epilepsy: A Molecular Approach Involving Wnt Pathway and KATP Channels

Epilepsy is a neurological disorder in which, in many cases, there is poor pharmacological control of seizures. Nevertheless, it may respond beneficially to alternative treatments such as dietary therapy, like the ketogenic diet or caloric restriction. One of the mechanisms of these diets is to produce a hyperpolarization mediated by the adenosine triphosphate (ATP)-sensitive potassium (KATP) channels (KATP channels). An extracellular increase of K+ prevents the release of Ca2+ by inhibiting the signaling of the Wnt pathway and the translocation of β-catenin to the cell nucleus. Wnt ligands hyperpolarize the cells by activating K+ current by Ca2+. Each of the diets described in this paper has in common a lower use of carbohydrates, which leads to biochemical, genetic processes presumed to be involved in the reduction of epileptic seizures. Currently, there is not much information about the genetic processes implicated as well as the possible beneficial effects of diet therapy on epilepsy. In this review, we aim to describe some of the possible genes involved in Wnt pathways, their regulation through the KATP channels which are implicated in each one of the diets, and how they can reduce epileptic seizures at the molecular level.

A Small-Molecule Approach to Restore a Slow-Oxidative Phenotype and Defective CaMKIIβ Signaling in Limb Girdle Muscular Dystrophy

Mutations in CAPN3 cause limb girdle muscular dystrophy R1 (LGMDR1, formerly LGMD2A) and lead to progressive and debilitating muscle wasting. Calpain 3 deficiency is associated with impaired CaMKIIβ signaling and blunted transcriptional programs that encode the slow-oxidative muscle phenotype. We conducted a high-throughput screen on a target of CaMKII (Myl2) to identify compounds to override this signaling defect; 4 were tested in vivo in the Capn3 knockout (C3KO) model of LGMDR1. The leading compound, AMBMP, showed good exposure and was able to reverse the LGMDR1 phenotype in vivo, including improved oxidative properties, increased slow fiber size, and enhanced exercise performance. AMBMP also activated CaMKIIβ signaling, but it did not alter other pathways known to be associated with muscle growth. Thus, AMBMP treatment activates CaMKII and metabolically reprograms skeletal muscle toward a slow muscle phenotype. These proof-of-concept studies lend support for an approach to the development of therapeutics for LGMDR1.

Wnt Signaling Through Nitric Oxide Synthase Promotes the Formation of Multi-Innervated Spines

Structural plasticity of synapses correlates with changes in synaptic strength. Dynamic modifications in dendritic spine number and size are crucial for long-term potentiation (LTP), the cellular correlate of learning and memory. Recent studies have suggested the generation of multi-innervated spines (MIS), in the form of several excitatory presynaptic inputs onto one spine, are crucial for hippocampal memory storage. However, little is known about the molecular mechanisms underlying MIS formation and their contribution to LTP. Using 3D enhanced resolution confocal images, we examined the contribution of Wnt synaptic modulators in MIS formation in the context of LTP. We show that blockage of endogenous Wnts with specific Wnt antagonists supresses the formation of MIS upon chemical LTP induction in cultured hippocampal neurons. Gain- and loss-of-function studies demonstrate that Wnt7a signaling promotes MIS formation through the postsynaptic Wnt scaffold protein Disheveled 1 (Dvl1) by stimulating neuronal nitric oxide (NO) synthase (nNOS). Subsequently, NO activates soluble guanylyl cyclase (sGC) to increase MIS formation. Consistently, we observed an enhanced frequency and amplitude of excitatory postsynaptic currents. Collectively, our findings identify a unique role for Wnt secreted proteins through nNOS/NO/sGC signaling to modulate MIS formation during LTP.

WNT regulates programmed muscle remodeling through PLC-β and calcineurin in Caenorhabditis elegans males

The ability of a muscle to break down and reform fibers is vital for development; however, if unregulated, abnormal muscle remodeling can occur, such as in the heart following cardiac infarction. To study how normal developmental remodeling is mediated, we used fluorescently tagged actin, mutant analyses, Ca2+ imaging and controlled Ca2+ release to determine the mechanisms regulating a conspicuous muscle change that occurs in Caenorhabditis elegans males. In hermaphrodites and larval males, the single cell anal depressor muscle, used for waste expulsion, contains bilateral dorsal-ventral sarcomeres. However, prior to male adulthood, the muscle sex-specifically remodels its sarcomeres anteriorly-posteriorly to promote copulation behavior. Although WNT signaling and calcineurin have been implicated separately in muscle remodeling, we unexpectedly found that they participate in the same pathway. We show that WNT signaling through Gαo and PLC-β results in sustained Ca2+ release via IP3 and ryanodine receptors to activate calcineurin. These results highlight the utility of this new model in identifying additional molecules involved in muscle remodeling.

Wnt-PLC-IP3-Connexin-Ca2+ axis maintains ependymal motile cilia in zebrafish spinal cord

Ependymal cells (ECs) are multiciliated neuroepithelial cells that line the ventricles of the brain and the central canal of the spinal cord (SC). How ependymal motile cilia are maintained remains largely unexplored. Here we show that zebrafish embryos deficient in Wnt signaling have defective motile cilia, yet harbor intact basal bodies. With respect to maintenance of ependymal motile cilia, plcδ3a is a target gene of Wnt signaling. Lack of Connexin43 (Cx43), especially its channel function, decreases motile cilia and intercellular Ca²⁺ wave (ICW) propagation. Genetic ablation of cx43 in zebrafish and mice diminished motile cilia. Finally, Cx43 is also expressed in ECs of the human SC. Taken together, our findings indicate that gap junction mediated ICWs play an important role in the maintenance of ependymal motile cilia, and suggest that the enhancement of functional gap junctions by pharmacological or genetic manipulations may be adopted to ameliorate motile ciliopathy.

Ependymal cells are supporting cells in the central nervous system. Here the authors elucidate a signalling axis in zebrafish spinal cord ependymal cells that is important for motile cilia assembly and maintenance, demonstrating that it depends on intercellular propagation of calcium ions via connexin 43.

Neuroprotection from Excitotoxic Injury by Local Administration of Lipid Emulsion into the Brain of Rats

Lipid emulsion was recently shown to attenuate cell death caused by excitotoxic conditions in the heart. There are key similarities between neurons and cardiomyocytes, such as excitability and conductibility, which yield vulnerability to excitotoxic conditions. However, systematic investigations on the protective effects of lipid emulsion in the central nervous system are still lacking. This study aimed to determine the neuroprotective effects of lipid emulsion in an in vivo rat model of kainic acid-induced excitotoxicity through intrahippocampal microinjections. Kainic acid and/or lipid emulsion-injected rats were subjected to the passive avoidance test and elevated plus maze for behavioral assessment. Rats were sacrificed at 24 h and 72 h after kainic acid injections for molecular study, including immunoblotting and qPCR. Brains were also cryosectioned for morphological analysis through cresyl violet staining and Fluorojade-C staining. Anxiety and memory functions were significantly preserved in 1% lipid emulsion-treated rats. Lipid emulsion was dose-dependent on the protein expression of β-catenin and the phosphorylation of GSK3-β and Akt. Wnt1 mRNA expression was elevated in lipid emulsion-treated rats compared to the vehicle. Neurodegeneration was significantly reduced mainly in the CA1 region with increased cell survival. Our results suggest that lipid emulsion has neuroprotective effects against excitotoxic conditions in the brain and may provide new insight into its potential therapeutic utility.

Involvement of Wnt7a in the role of M2c microglia in neural stem cell oligodendrogenesis

Background

The participation of microglia in CNS development and homeostasis indicate that these cells are pivotal for the regeneration that occurs after demyelination. The clearance of myelin debris and the inflammatory-dependent activation of local oligodendrocyte progenitor cells in a demyelinated lesion is dependent on the activation of M2c microglia, which display both phagocytic and healing functions. Emerging interest has been raised about the role of Wnt/β-catenin signaling in oligodendrogenesis and myelination. Besides, cytokines and growth factors released by microglia can control the survival, proliferation, migration, and differentiation of neural stem cells (NSCs), contributing to remyelination through the oligodendrocyte specification of this adult neurogenic niche.

Methods

TMEV-IDD model was used to study the contribution of dorsal SVZ stem cells to newly born oligodendrocytes in the corpus callosum following demyelination by (i) en-face dorsal SVZ preparations; (ii) immunohistochemistry; and (iii) cellular tracking. By RT-PCR, we analyzed the expression of Wnt proteins in demyelinated and remyelinating corpus callosum. Using in vitro approaches with microglia cultures and embryonic NSCs, we studied the role of purified myelin, Wnt proteins, and polarized microglia-conditioned medium to NSC proliferation and differentiation. One-way ANOVA followed by Bonferroni’s post-hoc test, or a Student’s t test were used to establish statistical significance.

Results

The demyelination caused by TMEV infection is paralleled by an increase in B1 cells and pinwheels in the dorsal SVZ, resulting in the mobilization of SVZ proliferative progenitors and their differentiation into mature oligodendrocytes. Demyelination decreased the gene expression of Wnt5a and Wnt7a, which was restored during remyelination. In vitro approaches show that Wnt3a enhances NSC proliferation, while Wnt7a and myelin debris promotes oligodendrogenesis from NSCs. As phagocytic M2c microglia secrete Wnt 7a, their conditioned media was found to induce Wnt/β-Catenin signaling in NSCs promoting an oligodendroglial fate.

Conclusions

We define here the contribution of microglia to Wnt production depending on their activation state, with M1 microglia secreting the Wnt5a protein and M2c microglia secreting Wnt7a. Collectively, our data reveal the role of reparative microglia in NSC oligodendrogenesis with the involvement of Wnt7a.

A Primary Cell and Organoid Platform for Evaluating Pharmacological Responses in Mammary Epithelial Cells

An essential process in predicting the in vivo pharmacological activity of a candidate molecule involves the evaluation of target responses using established model systems. While these models largely comprise immortalized cells, which are often serially passaged as monolayers on uniformly stiff substrates and are modified to overexpress one or more components of the pathway-of-interest, the importance of cell identity, heterogeneity, and three-dimensional (3D) context to target response is gaining increasing attention. Here, we assess intracellular calcium responses in mouse mammary epithelial cells in three distinct model systems: 3D primary organoids, 2D primary epithelial cells, and 2D immortalized cells. Specifically, we assess intracellular calcium responses to a number of extracellular signals implicated in the regulation of basal (or myoepithelial) cell function. These findings provide further insights into cell type and context-specific pharmacological responses in mammary epithelial cells and highlight the opportunities and challenges in the adoption of architecturally complex and heterogeneous in vitro assays in pharmacological research.

Rapid exchange of synaptic and extrasynaptic NMDA receptors in hippocampal CA1 neurons

N-methyl-d-aspartate receptors (NMDARs) are fundamental coincidence detectors of synaptic activity necessary for the induction of synaptic plasticity and synapse stability. Adjusting NMDAR synaptic content, whether by receptor insertion or lateral diffusion between extrasynaptic and synaptic compartments, could play a substantial role defining the characteristics of the NMDAR-mediated excitatory postsynaptic current (EPSC), which in turn would mediate the ability of the synapse to undergo plasticity. Lateral NMDAR movement has been observed in dissociated neurons; however, it is currently unclear whether NMDARs are capable of lateral surface diffusion in hippocampal slices, a more physiologically relevant environment. To test for lateral mobility in rat hippocampal slices, we rapidly blocked synaptic NMDARs using MK-801, a use-dependent and irreversible NMDAR blocker. Following a 5-min washout period, we observed a strong recovery of NMDAR-mediated responses. The degree of the observed recovery was proportional to the amount of induced blockade, independent of levels of intracellular calcium, and mediated primarily by GluN2B-containing NMDA receptors. These results indicate that lateral diffusion of NMDARs could be a mechanism by which synapses rapidly adjust parameters to fine-tune synaptic plasticity.NEW & NOTEWORTHY N-methyl-d-aspartate-type glutamate receptors (NMDARs) have always been considered stable components of synapses. We show that in rat hippocampal slices synaptic NMDARs are in constant exchange with extrasynaptic receptors. This exchange of receptors is mediated primarily by NMDA receptors containing GluN2B, a subunit necessary to undergo synaptic plasticity. Thus this lateral movement of synaptic receptors allows synapses to rapidly regulate the total number of synaptic NMDARs with potential consequences for synaptic plasticity.

SNAP25/syntaxin4/VAMP2/Munc18-1 Complexes in Spinal Dorsal Horn Contributed to Inflammatory Pain

Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) have been implicated in the trafficking of postsynaptic glutamate receptors, including N-methyl-d-aspartate (NMDA)-subtype glutamate receptors (NMDARs) that are critical for nociceptive plasticity and behavioral sensitization. However, the components of SNAREs complex involved in spinal nociceptive processing remain largely unknown. Here we found that SNAP25, syntaxin4, VAMP2 and Munc18-1 were localized at postsynaptic sites and formed the complex in the superficial lamina of spinal cord dorsal horn of rats. The complex formation between these SNAREs components were accelerated after intraplantar injection of complete Freund's adjuvant (CFA), pharmacological removal of GABAergic inhibition or activation of NMDAR in intact rats. The increased SNAP25/syntaxin4/VAMP2/Munc18-1 interaction facilitated the surface delivery and synaptic accumulation of NMDAR during inflammatory pain. Disruption of the molecular interaction between SNAP25 with its SNARE partners by using a blocking peptide derived from the C-terminus of SNAP25 effectively repressed the surface and synaptic accumulation of GluN2B-containing NMDARs in CFA-injected rats. This peptide also alleviated inflammatory mechanical allodynia and thermal hypersensitivity. These data suggested that SNAREs complex assembly in spinal cord dorsal horn was involved in the inflammatory pain hypersensitivity through promoting NMDAR synaptic trafficking.

The Hippo and Wnt signalling pathways: crosstalk during neoplastic progression in gastrointestinal tissue

The Hippo and Wnt signalling pathways play crucial roles in maintaining tissue homeostasis and organ size by orchestrating cell proliferation, differentiation and apoptosis. These pathways have been frequently found to be dysregulated in human cancers. While the canonical signal transduction of Hippo and Wnt has been well studied, emerging evidence shows that these two signalling pathways contribute to and exhibit overlapping functions in gastrointestinal (GI) tumorigenesis. In fact, the core effectors YAP/TAZ in Hippo signalling pathway cooperate with β-catenin in Wnt signalling pathway to promote GI neoplasia. Here, we provide a brief review to summarize the molecular mechanisms underlying the crosstalk between these two pathways and elucidate their involvement in GI tumorigenesis, particularly focusing on the intestine, stomach and liver.

Dickkopf-1 blocks 17β-estradiol-enhanced object memory consolidation in ovariectomized female mice

The memory-enhancing effects of 17β-estradiol (E₂) depend upon rapid activation of several cell-signaling cascades within the dorsal hippocampus (DH). Among the many cell-signaling pathways that mediate memory processes, Wnt/β-catenin signaling has emerged as a potential key player because of its importance to hippocampal development and synaptic plasticity. However, whether E₂ interacts with Wnt/β-catenin signaling to promote memory consolidation is unknown. Therefore, the present study examined whether Wnt/β-catenin signaling within the DH is necessary for E₂-induced memory consolidation in ovariectomized mice tested in the object recognition and object placement tasks. Ovariectomized C57BL/6 mice received immediate post-training infusions of E₂ or vehicle into the dorsal third ventricle plus the endogenous Wnt/β-catenin antagonist Dickkopf-1 (Dkk-1) or vehicle into the DH to assess whether the memory-enhancing effects of E₂ depend on activation of Wnt/β-catenin signaling. Our results suggest that Dkk-1 blocks E₂-induced memory enhancement as hypothesized, but may do so by only moderately blunting Wnt/β-catenin signaling while concurrently activating Wnt/JNK signaling. The current study provides novel insights into the mechanisms through which E₂ enhances memory consolidation in the DH, as well as critical information about the mechanistic actions of Dkk-1.

Tao-Hong-Si-Wu decoction reduces ischemia reperfusion rat myoblast cells calcium overloading and inflammation through the Wnt/IP3R/CAMKII pathway

Limb ischemia reperfusion (LIRI) injury is associated with serious local and systemic effects. Reperfusion may augment tissue injury in excess of that produced by ischemia alone. Calcium overloading and inflammation are considered to be two of the pathological mechanisms of limb ischemia/reperfusion (I/R) injury. Tao-Hong-Si-Wu decoction (THSWD) is a traditional Chinese herbal medicine with a powerful anti-inflammatory properties. We studied the probable restorative effect of THSWD on limb I/R-induced calcium overloading and inflammation in myoblast obtained from gastrocnemius muscle tissues of Sprague-Dawley rats (Frizzled Z5,a wnt5a blocker; KN-93, a calmodulin-dependent protein kinase II (CamkII) blocker; XeC, a IP3R blocker as positive controls). The simulated ischemia and reperfusion(I/R) solutions were used to imitate LIRI environment. The results showed that after I/R treatment, the secretion of proinflammatory factors (TNF-α and IL-1β) and Wnt5a/Ca²⁺ signal molecules (wnt5a, camkII, and IP3R) upregulated significantly, the Ca²⁺ concentration enhanced too in myoblast cells. THSWD pretreatment decreased the secretion of TNF-α and IL-1β, Ca²⁺ concentration; and abated the Wnt5a/Ca²⁺ signal molecules of wnt5a, camkII and IP3R expression activated by I/R injury; but could not abated the Wnt11 and protein kinase C (PKC) expression significantly, the results was similar with Frizzled Z5 treatment cells. Our research illustrated that THSWD may have a mitigating effect on LIRI targeting Wnt/IP3R/CAMKII but not Wnt/IP3R/PKC signaling pathway for the first time. This study may encourage the use of THSWD in the critical clinical settings with LIRI.

Maternal Gastrointestinal Nematode Infection Up-regulates Expression of Genes Associated with Long-Term Potentiation in Perinatal Brains of Uninfected Developing Pups

Establishment of neural networks critical for memory and cognition begins during the perinatal period but studies on the impact of maternal infection are limited. Using a nematode parasite that remains in the maternal intestine, we tested our hypothesis that maternal infection during pregnancy and early lactation would alter perinatal brain gene expression, and that the anti-inflammatory nature of this parasite would promote synaptic plasticity and long-term potentiation. Brain gene expression was largely unaffected two days after birth, but in seven-day old pups, long-term potentiation and four related pathways essential for the development of synaptic plasticity, cognition and memory were up-regulated in pups of infected dams. Interestingly, our data suggest that a lowering of Th1 inflammatory processes may underscore the apparent beneficial impact of maternal intestinal infection on long-term potentiation.