Combined deletion of p38γ and p38δ reduces skin inflammation and protects from carcinogenesis

MAPK13 controls structural remodeling and disease after epithelial injury

All living organisms are charged with repair after injury particularly at epithelial barrier sites, but in some cases this response leads instead to structural remodeling and long-term disease. Identifying the molecular and cellular control of this divergence is key to disease modification. In that regard, stress kinase control of epithelial stem cells is a rational entry point for study. Here we examine the potential for mitogen-activated protein kinase 13 (MAPK13) regulation of epithelial stem cells using models of respiratory viral injury and post-viral lung disease. We show that Mapk13 gene-knockout mice handle acute infectious illness as expected but are protected against structural remodeling manifest as basal-epithelial stem cell (basal-ESC) hyperplasia-metaplasia, immune activation, and mucinous differentiation. In corresponding cell models, Mapk13-deficiency directly attenuates basal-ESC growth and organoid formation. Extension to human studies shows marked induction/activation of basal-cell MAPK13 in clinical samples of comparable remodeling found in asthma and COPD. Here again, MAPK13 gene-knockdown inhibits human basal-ESC growth in culture. Together, the data identify MAPK13 as a control for structural remodeling and disease after epithelial injury and as a suitable target for down-regulation as a disease-modifying strategy.

p38γ MAPK Inflammatory and Metabolic Signaling in Physiology and Disease

p38γ MAPK (also called ERK6 or SAPK3) is a family member of stress-activated MAPKs and has common and specific roles as compared to other p38 proteins in signal transduction. Recent studies showed that, in addition to inflammation, p38γ metabolic signaling is involved in physiological exercise and in pathogenesis of cancer, diabetes, and Alzheimer's disease, indicating its potential as a therapeutic target. p38γphosphorylates at least 19 substrates through which p38γ activity is further modified to regulate life-important cellular processes such as proliferation, differentiation, cell death, and transformation, thereby impacting biological outcomes of p38γ-driven pathogenesis. P38γ signaling is characterized by its unique reciprocal regulation with its specific phosphatase PTPH1 and by its direct binding to promoter DNAs, leading to transcriptional activation of targets including cancer-like stem cell drivers. This paper will review recent findings about p38γ inflammation and metabolic signaling in physiology and diseases. Moreover, we will discuss the progress in the development of p38γ-specific pharmacological inhibitors for therapeutic intervention in disease prevention and treatment by targeting the p38γ signaling network.

P38γ modulates the lipid metabolism in non-alcoholic fatty liver disease by regulating the JAK-STAT signaling pathway

Non-alcoholic fatty liver disease (NAFLD) is a major health problem in Western countries and has become the most common cause of chronic liver disease. Although NAFLD is closely associated with obesity, inflammation, and insulin resistance, its pathogenesis remains unclear. The disease begins with excessive accumulation of triglycerides in the liver, which in turn leads to liver cell damage, steatosis, inflammation, and so on. P38γ is one of the four isoforms of P38 mitogen-activated protein kinases (P38 MAPKs) that contributes to inflammation in different diseases. In this research, we investigated the role of P38γ in NAFLD. In vivo, a NAFLD model was established by feeding C57BL/6J mice with a methionine- and choline-deficient (MCD) diet and adeno-associated virus (AAV9-shRNA-P38γ) was injected into C57BL/6J mice by tail vein for knockdown P38γ. The results indicated that the expression level of P38γ was upregulated in MCD-fed mice. Furthermore, the downregulation of P38γ significantly attenuated liver injury and lipid accumulation in mice. In vitro, mouse hepatocytes AML-12 were treated with free fatty acid (FFA). We found that P38γ was obviously increased in FFA-treated AML-12 cells, whereas knockdown of P38γ significantly suppressed lipid accumulation in FFA-treated AML-12 cells. Furthermore, P38γ regulated the Janus Kinase-Signal transducers and activators of transcription (JAK-STAT) signaling pathway. Inhibition of P38γ can inhibit the JAK-STAT signaling pathway, thereby inhibiting lipid accumulation in FFA-treated AML-12 cells. In conclusion, our results suggest that targeting P38γ contributes to the suppression of lipid accumulation in fatty liver disease.

Deletion of p38γ attenuates ethanol consumption- and acetaminophen-induced liver injury in mice through promoting Dlg1

Acetaminophen (APAP) is one of the major causes of drug-induced acute liver injury, and ethanol may aggravate APAP-induced liver injury. The problem of ethanol- and APAP-induced liver injury becomes increasingly prominent, but the mechanism of ethanol- and APAP-induced liver injury remains ambiguous. p38γ is one of the four isoforms of P38 mitogen activated protein kinases, that contributes to inflammation in different diseases. In this study we investigated the role of p38γ in ethanol- and APAP-induced liver injury. Liver injury was induced in male C57BL/6 J mice by giving liquid diet containing 5% ethanol (v/v) for 10 days, followed by gavage of ethanol (25% (v/v), 6 g/kg) once or injecting APAP (200 mg/kg, ip), or combined the both treatments. We showed that ethanol significantly aggravated APAP-induced liver injury in C57BL/6 J mice. Moreover, the expression level of p38γ was up-regulated in the liver of ethanol-, APAP- and ethanol+APAP-treated mice. Knockdown of p38γ markedly attenuated liver injury, inflammation, and steatosis in ethanol+APAP-treated mice. Liver sections of p38γ-knockdown mice displayed lower levels of Oil Red O stained dots and small leaky shapes. AML-12 cells were exposed to APAP (5 mM), ethanol (100 mM) or combined treatments. We showed that P38γ was markedly increased in ethanol+APAP-treated AML-12 cells, whereas knockdown of p38γ significantly inhibited inflammation, lipid accumulation and oxidative stress in ethanol+APAP-treated AML-12 cells. Furthermore, we revealed that p38γ could combine with Dlg1, a member of membrane-associated guanylate kinase family. Deletion of p38γ up-regulated the expression level of Dlg1 in ethanol+APAP-treated AML-12 cells. In summary, our results suggest that p38γ functions as an important regulator in ethanol- and APAP-induced liver injury through modulation of Dlg1.

Title: p38δ Regulates IL6 Expression Modulating ERK Phosphorylation in Preadipocytes

IL6 is an essential cytokine in metabolism regulation and for intercommunication among different organs and tissues. IL6 produced by different tissues has different functions and therefore it is very important to understand the mechanism of its expression in adipose tissue. In this work we demonstrated that IL6 expression in mouse preadipocytes, like in human, is partially dependent on Wnt5a and JNK. Using mouse preadipocytes lacking each one of the p38 SAPK family members, we have shown that IL6 expression is also p38γ and p38δ dependent. In fact, the lack of some of these two kinases increases IL6 expression without altering that of Wnt5a. Moreover, we show that the absence of p38δ promotes greater ERK1/2 phosphorylation in a MEK1/2 independent manner, and that this increased ERK1/2 phosphorylation state is contributing to the higher IL6 expression in p38δ^−/- preadipocytes. These results suggest a new crosstalk between two MAPK signaling pathway, p38δ and ERK1/2, where p38δ modulates the phosphorylation state of ERK1/2.

The p38 MAPK Components and Modulators as Biomarkers and Molecular Targets in Cancer

The mitogen-activated protein kinase (MAPK) family is an important bridge in the transduction of extracellular and intracellular signals in different responses at the cellular level. Within this MAPK family, the p38 kinases can be found altered in various diseases, including cancer, where these kinases play a fundamental role, sometimes with antagonistic mechanisms of action, depending on several factors. In fact, this family has an immense number of functionalities, many of them yet to be discovered in terms of regulation and action in different types of cancer, being directly involved in the response to cancer therapies. To date, three main groups of MAPKs have been identified in mammals: the extracellular signal-regulated kinases (ERK), Jun N-terminal kinase (JNK), and the different isoforms of p38 (α, β, γ, δ). In this review, we highlight the mechanism of action of these kinases, taking into account their extensive regulation at the cellular level through various modifications and modulations, including a wide variety of microRNAs. We also analyze the importance of the different isoforms expressed in the different tissues and their possible role as biomarkers and molecular targets. In addition, we include the latest preclinical and clinical trials with different p38-related drugs that are ongoing with hopeful expectations in the present/future of developing precision medicine in cancer.

The Role of p38γ in Cancer: From review to outlook

p38γ is a member of the p38 Mitogen Activated Protein Kinases (p38 MAPKs). It contains four subtypes in mammalian cells encoded by different genes including p38α (MAPK14), p38β (MAPK11), p38γ (MAPK12), and p38δ (MAPK13). Recent studies revealed that p38γ may exhibit a crucial role in tumorigenesis and cancer aggressiveness. Despite the large number of published literatures, further researches are demanded to clarify its role in cancer development, the tissue-specific function and associated novel treatment strategies. In this article, we provide the latest view on the connection between p38γ and malignant tumors, highlighting the function of p38γ. The clinical value of p38γ is also discussed, helping the translation into the remarkable therapeutic strategy in tumor diseases.

p38β - MAPK11 and its role in female cancers

Background

The p38MAPK family of Mitogen Activated Protein Kinases are a group of signalling molecules involved in cell growth, survival, proliferation and differentiation. The widely studied p38α isoform is ubiquitously expressed and is implicated in a number of cancer pathologies, as are p38γ and p38δ. However, the mechanistic role of the isoform, p38β, remains fairly elusive. Recent studies suggest a possible role of p38β in both breast and endometrial cancer with research suggesting involvement in bone metastasis and cancer cell survival. Female tissue specific cancers such as breast, endometrial, uterine and ovary account for over 3,000,000 cancer related incidents annually; advancements in therapeutics and treatment however require a deeper understanding of the molecular aetiology associated with these diseases. This study provides an overview of the MAPK signalling molecule p38β (MAPK11) in female cancers using an in-silico approach.

Methods

A detailed gene expression and methylation analysis was performed using datasets from cBioportal, CanSar and MEXPRESS. Breast, Uterine Endometrial, Cervical, Ovarian and Uterine Carcinosarcoma TCGA cancer datasets were used and analysed.

Results

Data using cBioportal and CanSAR suggest that expression of p38β is lower in cancers: BRCA, UCEC, UCS, CESC and OV compared to normal tissue. Methylation data from SMART and MEXPRESS indicate significant probe level variation of CpG island methylation status of the gene MAPK11. Analysis of the genes’ two CpG islands shows that the gene was hypermethylated in the CpG1 with increased methylation seen in BRCA, CESC and UCEC cancer data sets with a slight increase of expression recorded in cancer samples. CpG2 exhibited hypomethylation with no significant difference between samples and high levels of expression. Further analysis from MEXPRESS revealed no significance between probe methylation and altered levels of expression. In addition, no difference in the expression of BRCA oestrogen/progesterone/HER2 status was seen.

Conclusion

This data provides an overview of the expression of p38β in female tissue specific cancers, showing a decrease in expression of the gene in BRCA, UCEC, CESC, UCS and OV, increasing the understanding of p38β MAPK expression and offering insight for future in-vitro investigation and therapeutic application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-021-00834-9.

A Special View of What Was Almost Forgotten: p38δ MAPK

The p38δ mitogen-activated protein kinase is an important signal transduction enzyme. p38δ has recently emerged as a drug target due to its tissue-specific expression patterns and its critical roles in regulation of cellular processes related to cancer and inflammatory diseases, such as cell proliferation, cell migration, apoptosis, and inflammatory responses. However, potent and specific p38δ inhibitors have not been defined so far. Moreover, in cancer disease, p38δ appears to act as a tumor suppressor or tumor promoter according to cancer and cell type studied. In this review, we outline the current understanding of p38δ roles in each cancer type, to define whether it is possible to delineate new cancer therapies based on small-molecule p38δ inhibitors. We also highlight recent advances made in the design of molecules with potential to inhibit p38 isoforms and discuss structural approaches to guide the search for p38δ inhibitors.

Centrosome Dynamics and Its Role in Inflammatory Response and Metastatic Process

Metastasis is a process by which cancer cells escape from the location of the primary tumor invading normal tissues at distant organs. Chromosomal instability (CIN) is a hallmark of human cancer, associated with metastasis and therapeutic resistance. The centrosome plays a major role in organizing the microtubule cytoskeleton in animal cells regulating cellular architecture and cell division. Loss of centrosome integrity activates the p38-p53-p21 pathway, which results in cell-cycle arrest or senescence and acts as a cell-cycle checkpoint pathway. Structural and numerical centrosome abnormalities can lead to aneuploidy and CIN. New findings derived from studies on cancer and rare genetic disorders suggest that centrosome dysfunction alters the cellular microenvironment through Rho GTPases, p38, and JNK (c-Jun N-terminal Kinase)-dependent signaling in a way that is favorable for pro-invasive secretory phenotypes and aneuploidy tolerance. We here review recent data on how centrosomes act as complex molecular platforms for Rho GTPases and p38 MAPK (Mitogen activated kinase) signaling at the crossroads of CIN, cytoskeleton remodeling, and immune evasion via both cell-autonomous and non-autonomous mechanisms.

Emerging roles of microRNAs in intestinal ischemia/reperfusion-induced injury: a review

Intestinal ischemia/reperfusion (II/R) injury is a serious pathological phenomenon in underlying hemorrhagic shock, trauma, strangulated intestinal obstruction, and acute mesenteric ischemia which associated with high morbidity and mortality. MicroRNAs (miRNAs, miRs) are endogenous non-coding RNAs that regulate post-transcriptionally target mRNA translation via degrading it and/or suppressing protein synthesis. This review discusses on the role of some miRNAs in underlying II/R injury. Some of these miRNAs can have protective action through agomiR or specific antagomiR, and others can have destructive effects in the basal level of II/R insult. Based on these literature reviews, II/R injury affects several miRNAs and their specific target genes. Some miRNAs upregulate under condition of II/R injury, and multiple miRNAs downregulate following II/R damage. Data of this review have been collected from the scientific articles published in databases such as Science Direct, Scopus, PubMed, Web of Science, and Scientific Information Database from 2000 to 2020. It is shown a correlation between changes in the expression of miRNAs and autophagy, inflammation, oxidative stress, apoptosis, and epithelial barrier function. Taken together, agomiR or antagomiR of some miRNAs can be considered as one new target for the research and development of innovative drugs to the prevention or treatment of II/R damage.

p38β and Cancer: The Beginning of the Road

The p38 mitogen-activated protein kinase (MAPK) signaling pathway is implicated in cancer biology and has been widely studied over the past two decades as a potential therapeutic target. Most of the biological and pathological implications of p38MAPK signaling are often associated with p38α (MAPK14). Recently, several members of the p38 family, including p38γ and p38δ, have been shown to play a crucial role in several pathologies including cancer. However, the specific role of p38β (MAPK11) in cancer is still elusive, and further investigation is needed. Here, we summarize what is currently known about the role of p38β in different types of tumors and its putative implication in cancer therapy. All evidence suggests that p38β might be a key player in cancer development, and could be an important therapeutic target in several pathologies, including cancer.

B Cell Development and T-Dependent Antibody Response Are Regulated by p38γ and p38δ

p38MAP kinase (MAPK) signal transduction pathways are important regulators of inflammation and the immune response; their involvement in immune cell development and function is still largely unknown. Here we analysed the role of the p38 MAPK isoforms p38γ and p38δ in B cell differentiation in bone marrow (BM) and spleen, using mice lacking p38γ and p38δ, or conditional knockout mice that lack both p38γ and p38δ specifically in the B cell compartment. We found that the B cell differentiation programme in the BM was not affected in p38γ/δ-deficient mice. Moreover, these mice had reduced numbers of peripheral B cells as well as altered marginal zone B cell differentiation in the spleen. Expression of co-stimulatory proteins and activation markers in p38γ/δ-deficient B cells are diminished in response to B cell receptor (BCR) and CD40 stimulation; p38γ and p38δ were necessary for B cell proliferation induced by BCR and CD40 but not by TLR4 signaling. Furthermore, p38γ/δ-null mice produced significantly lower antibody responses to T-dependent antigens. Our results identify unreported functions for p38γ and p38δ in B cells and in the T-dependent humoral response; and show that the combined activity of these kinases is needed for peripheral B cell differentiation and function.

Cell Type-Specific p38δ Targeting Reveals a Context-, Stage-, and Sex-Dependent Regulation of Skin Carcinogenesis

Activation and/or upregulated expression of p38δ are demonstrated in human skin malignancies including cutaneous squamous cell carcinoma, suggesting a role for p38δ in skin carcinogenesis. We previously reported that mice with germline deletion of the p38δ gene are significantly protected from chemical skin carcinogenesis. Here, we investigated the effects of cell-selective targeted ablation of p38δ in keratinocytes and in immune (myeloid) cells on skin tumor development in a two-stage 7,12-dimethylbenz(a)anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA) chemical mouse skin carcinogenesis model. Conditional keratinocyte-specific p38δ ablation (p38δ-cKO^∆K) did not influence the latency, incidence, or multiplicity of chemically-induced skin tumors, but led to increased tumor volume in females during the TPA promotion stage, and reduced malignant progression in males and females relative to their wild-type counterparts. In contrast, conditional myeloid cell-specific p38δ deletion (p38δ-cKO^∆M) inhibited DMBA/TPA-induced skin tumorigenesis in male but not female mice. Thus, tumor onset was delayed, and tumor incidence, multiplicity, and volume were reduced in p38δ-cKO^∆M males compared with control wild-type males. Moreover, the percentage of male mice with malignant tumors was decreased in the p38δ-cKO^∆M group relative to their wild-type counterparts. Collectively, these results reveal that cell-specific p38δ targeting modifies susceptibility to chemical skin carcinogenesis in a context-, stage-, and sex-specific manner.

MicroRNA-351-5p aggravates intestinal ischaemia/reperfusion injury through the targeting of MAPK13 and Sirtuin-6

BACKGROUND AND PURPOSE

Intestinal ischaemia-reperfusion (II/R) injury is a serious clinical problem. Here we have investigated novel mechanisms and new drug targets in II/R injury by searching for microRNAs regulating such injury.

EXPERIMENTAL APPROACH

We used hypoxia/reoxygenation (H/R) of IEC-6 cell cultures and models of II/R models in rats and mice. Microarray assays were used to identify target miRNAs from rat intestinal. Real-time PCR, Western blot and dual luciferase reporter assays, and agomir and antagomir in vitro and in vivo were used to assess the effects of the target miRNA on II/R injury.

KEY RESULTS

The miR-351-5p was differentially expressed in our models and it targeted MAPK13 and sirtuin-6. This miRNA reduced levels of sirtuin-6 and AMP-activated protein kinase phosphorylation, and activated forkhead box O3 (FoxO3α) phosphorylation to cause oxidative stress. Also, miR-351-5p markedly reduced MAPK13 level, activated polycystic kidney disease 1/NF-κB signal and increased NF-κB (p65). Moreover, miR-351-5p up-regulated levels of Bcl2-associated X, cytochrome c, apoptotic peptidase activating factor 1, cleaved-caspase 3 and cleaved-caspase 9 by reducing sirtuin-6 levels to promote apoptosis. In addition, miR-351-5p mimic in IEC-6 cells and agomir in mice aggravated these effects, and miR-351-5p inhibitor and antagomir in mice alleviated these actions.

CONCLUSIONS AND IMPLICATIONS

Our data showed that miR-351-5p aggravated II/R injury by promoting intestinal mucosal oxidative stress, inflammation and apoptosis by targeting MAPK13 and sirtuin-6.These data provide new insights into the mechanisms regulating II/R injury, and of miR-351-5p could be considered as a novel therapeutic target for such injury.

Targeting an oncogenic kinase/phosphatase signaling network for cancer therapy

Protein kinases and phosphatases signal by phosphorylation and dephosphorylation to precisely control the activities of their individual and common substrates for a coordinated cellular outcome. In many situations, a kinase/phosphatase complex signals dynamically in time and space through their reciprocal regulations and their cooperative actions on a substrate. This complex may be essential for malignant transformation and progression and can therefore be considered as a target for therapeutic intervention. p38γ is a unique MAPK family member that contains a PDZ motif at its C-terminus and interacts with a PDZ domain-containing protein tyrosine phosphatase PTPH1. This PDZ-coupled binding is required for both PTPH1 dephosphorylation and inactivation of p38γ and for p38γ phosphorylation and activation of PTPH1. Moreover, the p38γ/PTPH1 complex can further regulate their substrates phosphorylation and dephosphorylation, which impacts Ras transformation, malignant growth and progression, and therapeutic response. This review will use the p38γ/PTPH1 signaling network as an example to discuss the potential of targeting the kinase/phosphatase signaling complex for development of novel targeted cancer therapy.

Myeloid cell deficiency of p38γ/p38δ protects against candidiasis and regulates antifungal immunity

Candida albicans is a frequent aetiologic agent of sepsis associated with high mortality in immunocompromised patients. Developing new antifungal therapies is a medical need due to the low efficiency and resistance to current antifungal drugs. Here, we show that p38γ and p38δ regulate the innate immune response to C. albicans We describe a new TAK1-TPL2-MKK1-ERK1/2 pathway in macrophages, which is activated by Dectin-1 engagement and positively regulated by p38γ/p38δ. In mice, p38γ/p38δ deficiency protects against C. albicans infection by increasing ROS and iNOS production and thus the antifungal capacity of neutrophils and macrophages, and by decreasing the hyper-inflammation that leads to severe host damage. Leucocyte recruitment to infected kidneys and production of inflammatory mediators are decreased in p38γ/δ-null mice, reducing septic shock. p38γ/p38δ in myeloid cells are critical for this effect. Moreover, pharmacological inhibition of p38γ/p38δ in mice reduces fungal burden, revealing that these p38MAPKs may be therapeutic targets for treating C. albicans infection in humans.

Deregulation of the pRb-E2F4 axis alters epidermal homeostasis and favors tumor development

E2F/RB activity is altered in most human tumors. The retinoblastoma family of proteins plays a key role in regulating the progression of the cell cycle from the G1 to S phases. This is achieved through negative regulation of E2F transcription factors, important positive regulators of cell cycle entry. E2F family members are divided into two groups: activators (E2F1-E2F3a) and repressors (E2F3b-E2F8). E2F4 accounts for a large part of the E2F activity and is a main E2F repressor member in vivo. Perturbations in the balance from quiescence towards proliferation contribute to increased mitotic gene expression levels frequently observed in cancer. We have previously reported that combined Rb1-Rbl1 or Rb1-E2f1 ablation in epidermis produces important alterations in epidermal proliferation and differentiation, leading to tumor development. However, the possible roles of E2F4 in this context are still to be determined. Here, we show the absence of any discernible phenotype in the skin of mice lacking of E2f4. In contrast, the inducible loss of Rb1 in the epidermis of E2F4-null mice produced multiple skin abnormalities including altered differentiation and proliferation, spontaneous wounds, carcinoma in situ development and stem cell perturbations. All these phenotypic alterations are associated with extensive gene expression changes, the induction of c-myc and the Akt activation. Moreover the whole transcriptome analyses in comparison with previous models generated also revealed extensive changes in multiple repressive complexes and in transcription factor activity. These results point to E2F4 as a master regulator in multiple steps of epidermal homeostasis in Rb1 absence.

p38γ and p38δ Are Involved in T Lymphocyte Development

p38 mitogen-activated protein kinase (MAPK) signal transduction pathways are essential regulators of the immune response. Particularly, p38γ and p38δ regulate many immune cell functions such as cytokine production, migration, or T cell activation; however, their involvement in immune cell development is largely unknown. Here, we analysed the role of p38 MAPK isoforms p38γ and p38δ in T cell differentiation in the thymus and in lymph nodes, using mice deficient in p38γ, p38δ, or in both. We found that the T cell differentiation program in the thymus was affected at different stages in p38γ-, p38δ-, and p38γ/δ-deficient mice, and also peripheral T cell homaeostasis was compromised. Particularly, p38δ deletion affects different stages of early CD4⁻CD8⁻ double-negative thymocyte development, whereas lack of p38γ favours thymocyte positive selection from CD4⁺CD8⁺ double-positive to CD4⁺ or CD8⁺ single-positive cells. Our results identify unreported functions for p38γ and p38δ in T cells.

p38γ and p38δ: From Spectators to Key Physiological Players

Although the physiological roles of p38γ and p38δ signalling pathways are largely unknown, new genetic and pharmacological tools are providing groundbreaking information on the function of these two stress-activated protein kinases. Recent studies show the importance of p38γ and p38δ in the regulation of processes as diverse as cytokine production, protein synthesis, exocytosis, cell migration, gene expression, and neuron activity, which have an acute impact on the development of pathologies related to inflammation, diabetes, neurodegeneration, and cancer. These recent breakthroughs are resolving some of the questions that have long been asked regarding the function of p38γ and p38δ in biology and pathology.

Heat Shock Factor 1 Is a Substrate for p38 Mitogen-Activated Protein Kinases

Heat shock factor 1 (HSF1) monitors the structural integrity of the proteome. Phosphorylation at S326 is a hallmark for HSF1 activation, but the identity of the kinase(s) phosphorylating this site has remained elusive. We show here that the dietary agent phenethyl isothiocyanate (PEITC) inhibits heat shock protein 90 (Hsp90), the main negative regulator of HSF1; activates p38 mitogen-activated protein kinase (MAPK); and increases S326 phosphorylation, trimerization, and nuclear translocation of HSF1, and the transcription of a luciferase reporter, as well as the endogenous prototypic HSF1 target Hsp70. In vitro, all members of the p38 MAPK family rapidly and stoichiometrically catalyze the S326 phosphorylation. The use of stable knockdown cell lines and inhibitors indicated that among the p38 MAPKs, p38γ is the principal isoform responsible for the phosphorylation of HSF1 at S326 in cells. A protease-mass spectrometry approach confirmed S326 phosphorylation and unexpectedly revealed that p38 MAPK also catalyzes the phosphorylation of HSF1 at S303/307, previously known repressive posttranslational modifications. Thus, we have identified p38 MAPKs as highly efficient catalysts for the phosphorylation of HSF1. Furthermore, our findings suggest that the magnitude and persistence of activation of p38 MAPK are important determinants of the extent and duration of the heat shock response.

p38MAPK and Chemotherapy: We Always Need to Hear Both Sides of the Story

The p38MAPK signaling pathway was initially described as a stress response mechanism. In fact, during previous decades, it was considered a pathway with little interest in oncology especially in comparison with other MAPKs such as ERK1/2, known to be target of oncogenes like Ras. However, its involvement in apoptotic cell death phenomena makes this signaling pathway more attractive for many cancer research laboratories. This apoptotic role allows to establish a link between p38MAPK and regular chemotherapeutic agents such as Cisplatin or base analogs (Cytarabine, Gemcitabine or 5-Fluorouracil) which are currently used in hospitals across the world. In fact, and more recently, p38MAPK has also been connected with targeted therapies like tyrosine kinase inhibitors (vg. Imatinib, Sorafenib) and, to a lesser extent, with monoclonal antibodies. In addition, the oncogenic or tumor suppressor potential of this signaling pathway has aroused the interest of the scientific community in evaluating p38MAPK as a novel target for cancer therapy. In this review, we will summarize the role of p38MAPK in chemotherapy as well as the potential that p38MAPK inhibition can bring to cancer therapy. All the evidences suggest that p38MAPK could be a double-edged sword and that the search for the most appropriate candidate patients, depending on their pathology and treatment, will lead to a more rational use of this new therapeutic tool.

First comprehensive structural and biophysical analysis of MAPK13 inhibitors targeting DFG-in and DFG-out binding modes

BACKGROUND

P38 MAP kinases are centrally involved in mediating extracellular signaling in various diseases. While much attention has previously been focused on the ubiquitously expressed family member MAPK14 (p38α), recent studies indicate that family members such as MAPK13 (p38δ) display a more selective cellular and tissue expression and might therefore represent a specific kinase to target in certain diseases.

METHODS

To facilitate the design of potent and specific inhibitors, we present here the structural, biophysical, and functional characterization of two new MAPK13-inhibitor complexes, as well as the first comprehensive structural, biophysical, and functional analysis of MAPK13 complexes with four different inhibitor compounds of greatly varying potency.

RESULTS

These inhibitors display IC50 values either in the nanomolar range or micromolar range (>800-fold range). The nanomolar inhibitors exhibit much longer ligand-enzyme complex half-lives compared to the micromolar inhibitors as measured by biolayer interferometry. Crystal structures of the MAPK13 inhibitor complexes reveal that the nanomolar inhibitors engage MAPK13 in the DFG-out binding mode, while the micromolar inhibitors are in the DFG-in mode. Detailed structural and computational docking analyses suggest that this difference in binding mode engagement is driven by conformational restraints imposed by the chemical structure of the inhibitors, and may be fortified by an additional hydrogen bond to MAPK13 in the nanomolar inhibitors.

CONCLUSIONS

These studies provide a structural basis for understanding the differences in potency exhibited by these inhibitors.

GENERAL SIGNIFICANCE

They also provide the groundwork for future studies to improve specificity, potency, pharmacodynamics, and pharmacokinetic properties.

Redundancy in the World of MAP Kinases: All for One

The protein kinases ERK1 and ERK2 are the effector components of the prototypical ERK1/2 mitogen-activated protein (MAP) kinase pathway. This signaling pathway regulates cell proliferation, differentiation and survival, and is essential for embryonic development and cellular homeostasis. ERK1 and ERK2 homologs share similar biochemical properties but whether they exert specific physiological functions or act redundantly has been a matter of controversy. However, recent studies now provide compelling evidence in support of functionally redundant roles of ERK1 and ERK2 in embryonic development and physiology. In this review, we present a critical assessment of the evidence for the functional specificity or redundancy of MAP kinase isoforms. We focus on the ERK1/ERK2 pathway but also discuss the case of JNK and p38 isoforms.

p38γ and p38δ Mitogen Activated Protein Kinases (MAPKs), New Stars in the MAPK Galaxy

The protein kinases p38γ and p38δ belong to the p38 mitogen-activated protein kinase (MAPK) family. p38MAPK signaling controls many cellular processes and is one of the most conserved mechanisms in eukaryotes for the cellular response to environmental stress and inflammation. Although p38γ and p38δ are widely expressed, it is likely that they perform specific functions in different tissues. Their involvement in human pathologies such as inflammation-related diseases or cancer is starting to be uncovered. In this article we give a general overview and highlight recent advances made in defining the functions of p38γ and p38δ, focusing in innate immunity and inflammation. We consider the potential of the pharmacological targeting of MAPK pathways to treat autoimmune and inflammatory diseases and cancer.