A p38 Mitogen-Activated Protein Kinase-Regulated Myocyte Enhancer Factor 2-β-Catenin Interaction Enhances Canonical Wnt Signaling

Microstructure, wear, and corrosion properties of PEEK-based composite coating incorporating titania- and copper-doped mesoporous bioactive glass nanoparticles

Poor wear- and corrosion-resistance of 316L SS implants are critical problems in orthopedic implants. This study aims to improve the wear- and corrosion-resistance of 316L SS through surface coating. In this study, a bilayer composite coating consisting of polyether ether ketone (PEEK) as the first layer, and titania (TiO2)- and Cu-doped mesoporous bioactive glass nanoparticles (Cu-MBGNs) were deposited as the second layer on a 316L SS via electrophoretic deposition (EPD). Scanning electron microscopy (SEM) images of the bilayer composite coating showed the distribution of TiO2 and Cu-MBGNs within the PEEK matrix. Energy dispersive spectroscopy (EDS) analysis confirmed the presence of TiO2 and Cu-MBGNs in the bilayer composite coating. Fourier transform infrared spectroscopy (FTIR) identified the functional groups attributed to the PEEK, TiO2 and Cu-MBGNs. X-ray diffraction (XRD) analysis confirmed the presence of TiO2 (anatase) and Cu-MBGNs in the bilayer composite coating. The coating exhibited a strong antibacterial effect against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Incorporating TiO2/Cu-MBGNs into the bilayer composite coating significantly modified the surface of 316L SS by improving the wear- and corrosion-resistance. Pin on disc test revealed that the specific wear rate of ∼(0.4570 ± 0.009) × 10-6 mm3 Nm-1 of the PEEK coating decreased to (0.0482 ± 0.007) × 10-6 mm3 Nm-1 on incorporating TiO2/Cu-MBGNs in PEEK coating under a normal load of 10 N in Dulbecco's Modified Eagle Medium (DMEM). Furthermore, electrochemical impedance spectroscopy (EIS) results revealed that the impedance value of the bilayer composite coating remained ∼4.56 × 105 Ω cm2 compared to 8.81 × 103 Ω cm2 of 316L SS after 24 h immersion in phosphate-buffered saline (PBS). Thus, this study demonstrated that the wear- and corrosion-resistance of 316L SS can be improved by incorporating TiO2/Cu-MBGNs in PEEK-based composite coatings for orthopedic applications.

Multiple myeloma: signaling pathways and targeted therapy

Multiple myeloma (MM) is the second most common hematological malignancy of plasma cells, characterized by osteolytic bone lesions, anemia, hypercalcemia, renal failure, and the accumulation of malignant plasma cells. The pathogenesis of MM involves the interaction between MM cells and the bone marrow microenvironment through soluble cytokines and cell adhesion molecules, which activate various signaling pathways such as PI3K/AKT/mTOR, RAS/MAPK, JAK/STAT, Wnt/β-catenin, and NF-κB pathways. Aberrant activation of these pathways contributes to the proliferation, survival, migration, and drug resistance of myeloma cells, making them attractive targets for therapeutic intervention. Currently, approved drugs targeting these signaling pathways in MM are limited, with many inhibitors and inducers still in preclinical or clinical research stages. Therapeutic options for MM include non-targeted drugs like alkylating agents, corticosteroids, immunomodulatory drugs, proteasome inhibitors, and histone deacetylase inhibitors. Additionally, targeted drugs such as monoclonal antibodies, chimeric antigen receptor T cells, bispecific T-cell engagers, and bispecific antibodies are being used in MM treatment. Despite significant advancements in MM treatment, the disease remains incurable, emphasizing the need for the development of novel or combined targeted therapies based on emerging theoretical knowledge, technologies, and platforms. In this review, we highlight the key role of signaling pathways in the malignant progression and treatment of MM, exploring advances in targeted therapy and potential treatments to offer further insights for improving MM management and outcomes.

Mature neurons from iPSCs unveil neurodegeneration-related pathways in mucopolysaccharidosis type II: GSK-3β inhibition for therapeutic potential

Mucopolysaccharidosis (MPS) type II is caused by a deficiency of iduronate-2-sulfatase and is characterized by the accumulation of glycosaminoglycans (GAGs). Without effective therapy, the severe form of MPS II causes progressive neurodegeneration and death. This study generated multiple clones of induced pluripotent stem cells (iPSCs) and their isogenic controls (ISO) from four patients with MPS II neurodegeneration. MPS II-iPSCs were successfully differentiated into cortical neurons with characteristic biochemical and cellular phenotypes, including axonal beadings positive for phosphorylated tau, and unique electrophysiological abnormalities, which were mostly rescued in ISO-iPSC-derived neurons. RNA sequencing analysis uncovered dysregulation in three major signaling pathways, including Wnt/β-catenin, p38 MAP kinase, and calcium pathways, in mature MPS II neurons. Further mechanistic characterization indicated that the dysregulation in calcium signaling led to an elevated intracellular calcium level, which might be linked to compromised survival of neurons. Based on these dysregulated pathways, several related chemicals and drugs were tested using this mature MPS II neuron-based platform and a small-molecule glycogen synthase kinase-3β inhibitor was found to significantly rescue neuronal survival, neurite morphology, and electrophysiological abnormalities in MPS II neurons. Our results underscore that the MPS II-iPSC-based platform significantly contributes to unraveling the mechanisms underlying the degeneration and death of MPS II neurons and assessing potential drug candidates. Furthermore, the study revealed that targeting the specific dysregulation of signaling pathways downstream of GAG accumulation in MPS II neurons with a well-characterized drug could potentially ameliorate neuronal degeneration.

A Protective Role of Canonical Wnt/β-Catenin Pathway in Pathogenic Bacteria-Induced Inflammatory Responses

Inflammation is a complex host defensive response against various disease-associated pathogens. A baseline extent of inflammation is supposed to be tightly associated with a sequence of immune-modulated processes, resulting in the protection of the host organism against pathogen invasion; however, as a matter of fact is that an uncontrolled inflammatory cascade is the main factor responsible for the host damage, accordingly suggesting a significant and indispensable involvement of negative feedback mechanism in modulation of inflammation. Evidence accumulated so far has supported a repressive effect of the canonical Wnt/β-catenin pathway on microbial-triggered inflammation via diverse mechanisms, although that consequence is dependent on the cellular context, types of stimuli, and cytokine environment. It is of particular interest and importance to comprehend the precise way in which the Wnt/β-catenin pathway is activated, due to its essential anti-inflammatory properties. It is assumed that an inflammatory milieu is necessary for initiating and activating this signaling, implying that Wnt activity is responsible for shielding tissues from overwhelming inflammation, thus sustaining a balanced physiological condition against bacterial infection. This review gathers the recent efforts to elucidate the mechanistic details through how Wnt/β-catenin signaling modulates anti-inflammatory responses in response to bacterial infection and its interactions with other inflammatory signals, which warrants further study for the development of specific interventions for the treatment of inflammatory diseases. Further clinical trials from different disease settings are required.

Notch1 Is Involved in Physiologic Cardiac Hypertrophy of Mice via the p38 Signaling Pathway after Voluntary Running

Appropriate exercise such as voluntary wheel-running can induce physiological cardiac hypertrophy. Notch1 plays an important role in cardiac hypertrophy; however, the experimental results are inconsistent. In this experiment, we aimed to explore the role of Notch1 in physiological cardiac hypertrophy. Twenty-nine adult male mice were randomly divided into a Notch1 heterozygous deficient control (Notch1^+/- CON) group, a Notch1 heterozygous deficient running (Notch1^+/- RUN) group, a wild type control (WT CON) group, and a wild type running (WT RUN) group. Mice in the Notch1^+/- RUN and WT RUN groups had access to voluntary wheel-running for two weeks. Next, the cardiac function of all of the mice was examined by echocardiography. The H&E staining, Masson trichrome staining, and a Western blot assay were carried out to analyze cardiac hypertrophy, cardiac fibrosis, and the expression of proteins relating to cardiac hypertrophy. After two-weeks of running, the Notch1 receptor expression was decreased in the hearts of the WT RUN group. The degree of cardiac hypertrophy in the Notch1^+/- RUN mice was lower than that of their littermate control. Compared to the Notch1^+/- CON group, Notch1 heterozygous deficiency could lead to a decrease in Beclin-1 expression and the ratio of LC3II/LC3I in the Notch1^+/- RUN group. The results suggest that Notch1 heterozygous deficiency could partly dampen the induction of autophagy. Moreover, Notch1 deficiency may lead to the inactivation of p38 and the reduction of β-catenin expression in the Notch1^+/- RUN group. In conclusion, Notch1 plays a critical role in physiologic cardiac hypertrophy through the p38 signaling pathway. Our results will help to understand the underlying mechanism of Notch1 on physiological cardiac hypertrophy.

Expression variations in ectodysplasin-A gene (eda) may contribute to morphological divergence of scales in haplochromine cichlids

BACKGROUND

Elasmoid scales are one of the most common dermal appendages and can be found in almost all species of bony fish differing greatly in their shape. Whilst the genetic underpinnings behind elasmoid scale development have been investigated, not much is known about the mechanisms involved in moulding of scales. To investigate the links between gene expression differences and morphological divergence, we inferred shape variation of scales from two different areas of the body (anterior and posterior) stemming from ten haplochromine cichlid species from different origins (Lake Tanganyika, Lake Malawi, Lake Victoria and riverine). Additionally, we investigated transcriptional differences of a set of genes known to be involved in scale development and morphogenesis in fish.

RESULTS

We found that scales from the anterior and posterior part of the body strongly differ in their overall shape, and a separate look on scales from each body part revealed similar trajectories of shape differences considering the lake origin of single investigated species. Above all, nine as well as 11 out of 16 target genes showed expression differences between the lakes for the anterior and posterior dataset, respectively. Whereas in posterior scales four genes (dlx5, eda, rankl and shh) revealed significant correlations between expression and morphological differentiation, in anterior scales only one gene (eda) showed such a correlation. Furthermore, eda displayed the most significant expression difference between species of Lake Tanganyika and species of the other two younger lakes. Finally, we found genetic differences in downstream regions of eda gene (e.g., in the eda-tnfsf13b inter-genic region) that are associated with observed expression differences. This is reminiscent of a genetic difference in the eda-tnfsf13b inter-genic region which leads to gain or loss of armour plates in stickleback.

CONCLUSION

These findings provide evidence for cross-species transcriptional differences of an important morphogenetic factor, eda, which is involved in formation of ectodermal appendages. These expression differences appeared to be associated with morphological differences observed in the scales of haplochromine cichlids indicating potential role of eda mediated signal in divergent scale morphogenesis in fish.

MEF2 in cardiac hypertrophy in response to hypertension

Hypertension is a globally prevalent pathological condition and an underlying risk factor for the development of cardiac hypertrophy leading to heart failure. Myocyte enhancer factor 2 (Mef2) has been identified as one of the primary effectors of morphological changes in the hypertensive heart, as part of a complex network of molecular signaling controlling cardiac gene expression. Experimental chronic pressure-overload models that mimic hypertension in the mammalian heart lead to the activation of various pathological mechanisms that result in structural changes leading to debilitating cardiac hypertrophy and ultimately heart failure. The purpose here is to survey the literature implicating Mef2 in hypertension induced cardiac hypertrophy, towards illuminating points of interest for understanding and potentially treating heart failure.

TAZ exhibits phase separation properties and interacts with Smad7 and β-catenin to repress skeletal myogenesis

Hippo signaling in Drosophila and mammals is prominent in regulating cell proliferation, death and differentiation. Hippo signaling effectors (YAP/TAZ) exhibit crosstalk with transforming growth factor-β (TGF-β)-Smad and Wnt-β-catenin pathways. Previously, we implicated Smad7 and β-catenin in myogenesis. Therefore, we assessed a potential role of TAZ on theSmad7/β-catenin complex in muscle cells. Here, we document functional interactions between Smad7, TAZ and β-catenin in myogenic cells. Ectopic TAZ expression resulted in repression of the muscle-specific creatine kinase muscle (ckm) gene promoter and its corresponding protein level. Depletion of endogenous TAZ enhanced ckm promoter activation. Ectopic TAZ, while potently active on a TEAD reporter (HIP-HOP), repressed myogenin and myod enhancer regions and Myogenin protein level. Additionally, a Wnt/β-catenin readout (TOP flash) demonstrated TAZ inhibition of β-catenin activity. In myoblasts, TAZ is predominantly localized in nuclear speckles, while in differentiation conditions TAZ is hyperphosphorylated at Ser 89 leading to enhanced cytoplasmic sequestration. Finally, live cell imaging indicates that TAZ exhibits properties of liquid-liquid phase separation (LLPS). These observations indicate that TAZ, as an effector of Hippo signaling, supresses the myogenic differentiation machinery.

MEF2A transcriptionally upregulates the expression of ZEB2 and CTNNB1 in colorectal cancer to promote tumor progression

Colorectal cancer (CRC) is one of the leading cancers worldwide, accounting for high morbidity and mortality. The mechanisms governing tumor growth and metastasis in CRC require detailed investigation. The results of the present study indicated that the transcription factor (TF) myocyte enhancer factor 2A (MEF2A) plays a dual role in promoting proliferation and metastasis of CRC by inducing the epithelial-mesenchymal transition (EMT) and activation of WNT/β-catenin signaling. Aberrant expression of MEF2A in CRC clinical specimens was significantly associated with poor prognosis and metastasis. Functionally, MEF2A directly binds to the promoter region to initiate the transcription of ZEB2 and CTNNB1. Simultaneous activation of the expression of EMT-related TFs and Wnt/β-catenin signaling by MEF2A overexpression induced the EMT and increased the frequency of tumor formation and metastasis. The present study identified a new critical oncogene involved in the growth and metastasis of CRC, providing a potential novel therapeutic target for CRC intervention.

Smad7:β-catenin complex regulates myogenic gene transcription

Recent reports indicate that Smad7 promotes skeletal muscle differentiation and growth. We previously documented a non-canonical role of nuclear Smad7 during myogenesis, independent of its role in TGF-β signaling. Here further characterization of the myogenic function of Smad7 revealed β-catenin as a Smad7 interacting protein. Biochemical analysis identified a Smad7 interaction domain (SID) between aa575 and aa683 of β-catenin. Reporter gene analysis and chromatin immunoprecipitation demonstrated that Smad7 and β-catenin are cooperatively recruited to the extensively characterized ckm promoter proximal region to facilitate its muscle restricted transcriptional activation in myogenic cells. Depletion of endogenous Smad7 and β-catenin in muscle cells reduced ckm promoter activity indicating their role during myogenesis. Deletion of the β-catenin SID substantially reduced the effect of Smad7 on the ckm promoter and exogenous expression of SID abolished β-catenin function, indicating that SID functions as a trans dominant-negative regulator of β-catenin activity. β-catenin interaction with the Mediator kinase complex through its Med12 subunit led us to identify MED13 as an additional Smad7-binding partner. Collectively, these studies document a novel function of a Smad7-MED12/13-β-catenin complex at the ckm locus, indicating a key role of this complex in the program of myogenic gene expression underlying skeletal muscle development and regeneration.

MEF-2 isoforms' (A-D) roles in development and tumorigenesis

Myocyte enhancer factor (MEF)-2 plays a critical role in proliferation, differentiation, and development of various cell types in a tissue specific manner. Four isoforms of MEF-2 (A-D) differentially participate in controlling the cell fate during the developmental phases of cardiac, muscle, vascular, immune and skeletal systems. Through their associations with various cellular factors MEF-2 isoforms can trigger alterations in complex protein networks and modulate various stages of cellular differentiation, proliferation, survival and apoptosis. The role of the MEF-2 family of transcription factors in the development has been investigated in various cell types, and the evolving alterations in this family of transcription factors have resulted in a diverse and wide spectrum of disease phenotypes, ranging from cancer to infection. This review provides a comprehensive account on MEF-2 isoforms (A-D) from their respective localization, signaling, role in development and tumorigenesis as well as their association with histone deacetylases (HDACs), which can be exploited for therapeutic intervention.

Vascular smooth muscle-MAPK14 is required for neointimal hyperplasia by suppressing VSMC differentiation and inducing proliferation and inflammation

Injury-induced stenosis is a serious vascular complication. We previously reported that p38α (MAPK14), a redox-regulated p38MAPK family member was a negative regulator of the VSMC contractile phenotype in vitro. Here we evaluated the function of VSMC-MAPK14 in vivo in injury-induced neointima hyperplasia and the underlying mechanism using an inducible SMC-MAPK14 knockout mouse line (iSMC-MAPK14^-/-). We show that MAPK14 expression and activity were induced in VSMCs after carotid artery ligation injury in mice and ex vivo cultured human saphenous veins. While the vasculature from iSMC-MAPK14^-/- mice was indistinguishable from wildtype littermate controls at baseline, these mice exhibited reduced neointima formation following carotid artery ligation injury. Concomitantly, there was an increased VSMC contractile protein expression in the injured vessels and a decrease in proliferating cells. Blockade of MAPK14 through a selective inhibitor suppressed, while activation of MAPK14 by forced expression of an upstream MAPK14 kinase promoted VSMC proliferation in cultured VSMCs. Genome wide RNA array combined with VSMC lineage tracing studies uncovered that vascular injury evoked robust inflammatory responses including the activation of proinflammatory gene expression and accumulation of CD45 positive inflammatory cells, which were attenuated in iSMC-MAPK14^-/- mice. Using multiple pharmacological and molecular approaches to manipulate MAPK14 pathway, we further confirmed the critical role of MAPK14 in activating proinflammatory gene expression in cultured VSMCs, which occurs in a p65/NFkB-dependent pathway. Finally, we found that NOX4 contributes to MAPK14 suppression of the VSMC contractile phenotype. Our results revealed that VSMC-MAPK14 is required for injury-induced neointima formation, likely through suppressing VSMC differentiation and promoting VSMC proliferation and inflammation. Our study will provide mechanistic insights into therapeutic strategies for mitigation of vascular stenosis.

FMRP recruitment of β-catenin to the translation pre-initiation complex represses translation

Canonical Wnt/β-catenin signaling is an essential regulator of various cellular functions throughout development and adulthood. Aberrant Wnt/β-catenin signaling also contributes to various pathologies including cancer, necessitating an understanding of cell context-dependent mechanisms regulating this pathway. Since protein-protein interactions underpin β-catenin function and localization, we sought to identify novel β-catenin interacting partners by affinity purification coupled with tandem mass spectrometry in vascular smooth muscle cells (VSMCs), where β-catenin is involved in both physiological and pathological control of cell proliferation. Here, we report novel components of the VSMC β-catenin interactome. Bioinformatic analysis of the protein networks implies potentially novel functions for β-catenin, particularly in mRNA translation, and we confirm a direct interaction between β-catenin and the fragile X mental retardation protein (FMRP). Biochemical studies reveal a basal recruitment of β-catenin to the messenger ribonucleoprotein and translational pre-initiation complex, fulfilling a translational repressor function. Wnt stimulation antagonizes this function, in part, by sequestering β-catenin away from the pre-initiation complex. In conclusion, we present evidence that β-catenin fulfills a previously unrecognized function in translational repression.

MEF2 signaling and human diseases

The members of myocyte Enhancer Factor 2 (MEF2) protein family was previously believed to function in the development of heart and muscle. Recent reports indicate that they are also closely associated with development and progression of many human diseases. Although their role in cancer biology is well established, the molecular mechanisms underlying their action is yet largely unknown. MEF2 family is closely associated with various signaling pathways, including Ca²⁺ signaling, MAP kinase signaling, Wnt signaling, PI3K/Akt signaling, etc. microRNAs also contribute to regulate the activities of MEF2. In this review, we summarize the known molecular mechanism by which MEF2 family contribute to human diseases.

Ectopic expression of Cdk8 induces eccentric hypertrophy and heart failure

Widespread changes in cardiac gene expression occur during heart failure, yet the mechanisms responsible for coordinating these changes remain poorly understood. The Mediator complex represents a nodal point for modulating transcription by bridging chromatin-bound transcription factors with RNA polymerase II activity; it is reversibly regulated by its cyclin-dependent kinase 8 (Cdk8) kinase submodule. Here, we identified increased Cdk8 protein expression in human failing heart explants and determined the consequence of this increase in cardiac-specific Cdk8-expressing mice. Transgenic Cdk8 overexpression resulted in progressive dilated cardiomyopathy, heart failure, and premature lethality. Prior to functional decline, left ventricular cardiomyocytes were dramatically elongated, with disorganized transverse tubules and dysfunctional calcium handling. RNA sequencing results showed that myofilament gene isoforms not typically expressed in adult cardiomyocytes were enriched, while oxidative phosphorylation and fatty acid biosynthesis genes were downregulated. Interestingly, candidate upstream transcription factor expression levels and MAPK signaling pathways thought to determine cardiomyocyte size remained relatively unaffected, suggesting that Cdk8 functions within a novel growth regulatory pathway. Our findings show that manipulating cardiac gene expression through increased Cdk8 levels is detrimental to the heart by establishing a transcriptional program that induces pathological remodeling and eccentric hypertrophy culminating in heart failure.

CAPE increases the expression of SOD3 through epigenetics in human retinal endothelial cells

Extracellular-superoxide dismutase (EC-SOD or SOD3), which catalyzes the dismutation of superoxide anions into hydrogen peroxide, plays a key role in vascular protection against reactive oxygen species (ROS). The excess generation of ROS is closely involved in the pathogenesis of diabetic retinopathy (DR); therefore, the maintenance of SOD3 expression at high levels is important for the prevention of DR. In the present study, we showed that caffeic acid phenethyl ester (CAPE) increased the expression of SOD3 through the acetylation of histone within the SOD3 promoter region in human retinal endothelial cells (HRECs). Histone acetylation within its promoter was focused on the inhibition of histone deacetylase (HDAC), and we examined the involvement of myocyte enhancer factor 2 (MEF2) and HDAC1 in CAPE-elicited SOD3 expression. Our results demonstrate that SOD3 silencing in basal HRECs is regulated by HDAC1 composed with MEF2A/2D hetero dimers. Moreover, phosphorylation of threonine 312 in MEF2A and dissociation of HDAC1 from SOD3 promoter play pivotal roles in CAPE-elicited SOD3 expression. Overall, our findings provide that CAPE may be one of the seed compounds that maintain redox homeostasis.

Down-regulation of miR-125a-5p is associated with salivary adenoid cystic carcinoma progression via targeting p38/JNK/ERK signal pathway

Salivary adenoid cystic carcinoma (SACC) is a relatively uncommon epithelial-like malignancy that can occur in the head and neck region. Despite its slow growth, this aggressive salivary gland tumor frequently recurs and metastasizes to distant organs since lacking effective chemotherapy treatment. MicroRNAs are key regulators in tumor metastasis and progression, but their roles during SACC progression have not been illustrated. In current study, we demonstrate that miR-125a-5p is down-regulated in SACC and closely related to the metastasis and progression in human SACC specimens. In vitro, miR-125a-5p mimic can suppress SACC cell migration and invasion; while blocking miR-125a-5p can relieve the inhibition effect. By using dual-luciferase assay, we confirmed that miR-125a-5p directly targeted to p38 and tissue samples of patients indicated the negative correlation between miR-125a-5p and p38; clinical analysis also showed that low level expression of miR-125a-5p is closely associated with poor prognosis of SACC. Furthermore, down-regulation of miR-125a-5p triggered downstream p38/JNK/ERK activation. Taken together, our results indicate that down-regulation of miR-125a-5p promotes SACC progression through p38 signal pathway and miR-125a-5p can be a potential therapeutic target of SACC.

Neighbours of cancer-related proteins have key influence on pathogenesis and could increase the drug target space for anticancer therapies

Even targeted chemotherapies against solid cancers show a moderate success increasing the need to novel targeting strategies. To address this problem, we designed a systems-level approach investigating the neighbourhood of mutated or differentially expressed cancer-related proteins in four major solid cancers (colon, breast, liver and lung). Using signalling and protein–protein interaction network resources integrated with mutational and expression datasets, we analysed the properties of the direct and indirect interactors (first and second neighbours) of cancer-related proteins, not found previously related to the given cancer type. We found that first neighbours have at least as high degree, betweenness centrality and clustering coefficient as cancer-related proteins themselves, indicating a previously unknown central network position. We identified a complementary strategy for mutated and differentially expressed proteins, where the affect of differentially expressed proteins having smaller network centrality is compensated with high centrality first neighbours. These first neighbours can be considered as key, so far hidden, components in cancer rewiring, with similar importance as mutated proteins. These observations strikingly suggest targeting first neighbours as a novel strategy for disrupting cancer-specific networks. Remarkably, our survey revealed 223 marketed drugs already targeting first neighbour proteins but applied mostly outside oncology, providing a potential list for drug repurposing against solid cancers. For the very central first neighbours, whose direct targeting would cause several side effects, we suggest a cancer-mimicking strategy by targeting their interactors (second neighbours of cancer-related proteins, having a central protein affecting position, similarly to the cancer-related proteins). Hence, we propose to include first neighbours to network medicine based approaches for (but not limited to) anticancer therapies.

Cancer is considered a systems disease in which the interactors of cancer-related proteins have a key role, also as targets to fight cancer. New therapeutic approaches are needed to improve success rates and to identify suitable proteins as novel, alternative drug targets. We designed a computational approach, combining mutation and differential expression data with network information, to analyse the interactions of cancer-related proteins in colon, breast, liver and lung cancer. We found that first (direct) neighbours, not linked previously to the given cancer type, are similarly important as mutated proteins known to be involved in cancer development. We found 223 drugs already in the clinic targeting these proteins but not yet used against cancer as their oncology relevance was hidden so far. Our observations open up new strategies for target selection and anti-cancer drug discovery.

Regulation of Hspb7 by MEF2 and AP-1: implications for Hspb7 in muscle atrophy

Mycocyte enhancer factor 2 (MEF2) and activator protein 1 (AP-1) transcription complexes have been individually implicated in myogenesis, but their genetic interaction has not previously been addressed. Using MEF2A, c-Jun and Fra-1 chromatin immunoprecipitation sequencing (ChIP-seq) data and predicted AP-1 consensus motifs, we identified putative common MEF2 and AP-1 target genes, several of which are implicated in regulating the actin cytoskeleton. Because muscle atrophy results in remodelling or degradation of the actin cytoskeleton, we characterized the expression of putative MEF2 and AP-1 target genes (Dstn, Flnc, Hspb7, Lmod3 and Plekhh2) under atrophic conditions using dexamethasone (Dex) treatment in skeletal myoblasts. Heat shock protein b7 (Hspb7) was induced by Dex treatment and further analyses revealed that loss of MEF2A using siRNA prevented Dex-regulated induction of Hspb7. Conversely, ectopic Fra-2 or c-Jun expression reduced Dex-mediated upregulation of Hspb7 whereas AP-1 depletion enhanced Hspb7 expression. In vivo, expression of Hspb7 and other autophagy-related genes was upregulated in response to atrophic conditions in mice. Manipulation of Hspb7 levels in mice also impacted gross muscle mass. Collectively, these data indicate that MEF2 and AP-1 confer antagonistic regulation of Hspb7 gene expression in skeletal muscle, with implications for autophagy and muscle atrophy.

p38 MAP kinase is required for Wnt3a-mediated osterix expression independently of Wnt-LRP5/6-GSK3β signaling axis in dental follicle cells

Wnt3a is a secreted glycoprotein that activates the glycogen synthase kinase-3β (GSK3β)/β-catenin signaling pathway through low-density-lipoprotein receptor-related protein (LRP)5/6 co-receptors. Wnt3a has been implicated in periodontal development and homeostasis, as well as in cementum formation. Recently, we have reported that Wnt3a increases alkaline phosphatase expression through the induction of osterix (Osx) expression in dental follicle cells, a precursor of cementoblasts. However, the molecular mechanism by which Wnt3a induces Osx expression is still unknown. In this study, we show that Wnt3a-induced Osx expression was inhibited in the presence of p38 mitogen-activated protein kinase (MAPK) inhibitors (SB203580 and SB202190) at gene and protein levels, as assessed by real-time PCR and immunocytohistochemistry, respectively. Pretreatment of cells with Dickkopf-1, a potent canonical Wnt antagonist binding to LRP5/6 co-receptors, did not influence Wnt3a-mediated p38 MAPK phosphorylation, suggesting that Wnt3a activates p38 MAPK through LRP5/6-independent signaling. On the other hand, pretreatment with p38 MAPK inhibitors had no effects on the phosphorylated status of GSK3β and β-catenin as well as β-catenin nuclear translocation, but inhibited Wnt3a-mediated β-catenin transcriptional activity. These findings suggest that p38 MAPK modulates canonical Wnt signaling at the β-catenin transcriptional level without any crosstalk with the Wnt3a-mediated LRP5/6-GSK3β signaling axis and subsequent β-catenin nuclear translocation. These findings expand our knowledge of the mechanisms controlling periodontal development and regeneration.

p38 MAPK Signaling in Osteoblast Differentiation

The skeleton is a highly dynamic tissue whose structure relies on the balance between bone deposition and resorption. This equilibrium, which depends on osteoblast and osteoclast functions, is controlled by multiple factors that can be modulated post-translationally. Some of the modulators are Mitogen-activated kinases (MAPKs), whose role has been studied in vivo and in vitro. p38-MAPK modifies the transactivation ability of some key transcription factors in chondrocytes, osteoblasts and osteoclasts, which affects their differentiation and function. Several commercially available inhibitors have helped to determine p38 action on these processes. Although it is frequently mentioned in the literature, this chemical approach is not always as accurate as it should be. Conditional knockouts are a useful genetic tool that could unravel the role of p38 in shaping the skeleton. In this review, we will summarize the state of the art on p38 activity during osteoblast differentiation and function, and emphasize the triggers of this MAPK.