PKA-mediated phosphorylation of EPEC-Tir at serine residues 434 and 463: A novel pathway in regulating Rac1 GTPase function

Ponatinib Activates an Inflammatory Response in Endothelial Cells via ERK5 SUMOylation

Ponatinib is a multi-targeted third generation tyrosine kinase inhibitor (TKI) used in the treatment of chronic myeloid leukemia (CML) patients harboring the Abelson (Abl)-breakpoint cluster region (Bcr) T315I mutation. In spite of having superb clinical efficacy, ponatinib triggers severe vascular adverse events (VAEs) that significantly limit its therapeutic potential. On vascular endothelial cells (ECs), ponatinib promotes EC dysfunction and apoptosis, and inhibits angiogenesis. Furthermore, ponatinib-mediated anti-angiogenic effect has been suggested to play a partial role in systemic and pulmonary hypertension via inhibition of vascular endothelial growth factor receptor 2 (VEGFR2). Even though ponatinib-associated VAEs are well documented, their etiology remains largely unknown, making it difficult to efficiently counteract treatment-related adversities. Therefore, a better understanding of the mechanisms by which ponatinib mediates VAEs is critical. In cultured human aortic ECs (HAECs) treated with ponatinib, we found an increase in nuclear factor NF-kB/p65 phosphorylation and NF-kB activity, inflammatory gene expression, cell permeability, and cell apoptosis. Mechanistically, ponatinib abolished extracellular signal-regulated kinase 5 (ERK5) transcriptional activity even under activation by its upstream kinase mitogen-activated protein kinase kinase 5α (CA-MEK5α). Ponatinib also diminished expression of ERK5 responsive genes such as Krüppel-like Factor 2/4 (klf2/4) and eNOS. Because ERK5 SUMOylation counteracts its transcriptional activity, we examined the effect of ponatinib on ERK5 SUMOylation, and found that ERK5 SUMOylation is increased by ponatinib. We also found that ponatibib-mediated increased inflammatory gene expression and decreased anti-inflammatory gene expression were reversed when ERK5 SUMOylation was inhibited endogenously or exogenously. Overall, we propose a novel mechanism by which ponatinib up-regulates endothelial ERK5 SUMOylation and shifts ECs to an inflammatory phenotype, disrupting vascular homeostasis.

Bis (3-bromo-4,5-dihydroxybenzyl) ether, a novel bromophenol from the marine red alga Polysiphonia morrowii that suppresses LPS-induced inflammatory response by inhibiting ROS-mediated ERK signaling pathway in RAW 264.7 macrophages

Inflammation is a pathophysiological defense response against various factors for maintaining homeostasis in the body. However, when continued excessive inflammation becomes chronic, various chronic diseases can develop. Therefore, effective treatment before chronic inflammation development is essential. Bis (3-bromo-4,5-dihydroxybenzyl) ether (BBDE, C₁₄H₁₂Br₂O₅) is a novel bromophenol isolated from the red alga Polysiphonia morrowii. The beneficial physiological functions of various bromophenols are known, but whether BBDE has beneficial physiological functions is unknown. Therefore, we first investigated whether BBDE exerts any anti-inflammatory effect. We demonstrated that BBDE inhibits inflammation by reducing inflammatory mediators, such as nitric oxide, prostaglandin E2, iNOS, COX2, and pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-1β, and interleukin-6), in LPS-induced macrophage cells. To examine the mechanism of action by which BBDE inhibits inflammation, we confirmed its effect on signal transduction and ROS generation. BBDE selectively inhibited ERK phosphorylation in the mitogen-activated protein kinase pathways. Moreover BBDE suppressed LPS-induced ROS generation in RAW 264.7 macrophage cells. Inhibition of LPS-induced ROS generation by BBDE also caused ERK inactivation and an inflammatory reaction. Therefore, BBDE inhibits LPS-induced inflammation by inhibiting the ROS-mediated ERK signaling pathway in RAW 264.7 macrophage cells and thus can be useful for treating inflammatory diseases.

Mechanism underlying the contractile activity of UTP in the mammalian heart

We previously reported that uridine 5'-triphosphate (UTP), a pyrimidine nucleoside triphosphate produced a concentration- and time-dependent increase in the contraction force in isolated right atrial preparations from patients undergoing cardiac bypass surgery due to angina pectoris. The stimulation of the force of contraction was sustained rather than transient. In the present study, we tried to elucidate the underlying receptor and signal transduction for this effect of UTP. Therefore, we measured the effect of UTP on force of contraction, phosphorylation of p38 and ERK1/2, in human atrial preparations, atrial preparations from genetically modified mice, cardiomyocytes from adult mice and cardiomyocytes from neonatal rats. UTP exerted a positive inotropic effect in isolated electrically driven left atrial preparations from wild-type (WT) mice and P2Y₂-, P2Y₄- and P2Y₆-receptor knockout mice. Therefore, we concluded that these P2Y receptors did not mediate the inotropic effects of UTP in atrial preparations from mice. However, UTP (like ATP) increased the phosphorylation states of p38 and ERK1/2 in neonatal rat cardiomyocytes, adult mouse cardiomyocytes and human atrial tissue in vitro. U0126, a MEK 1/2- signal cascade inhibitor, attenuated this phosphorylation and the positive inotropic effects of UTP in murine and human atrial preparations. We suggest that presently unknown receptors mediate the positive inotropic effect of UTP in murine and human atria. We hypothesize that UTP stimulates inotropy via p38 or ERK1/2 phosphorylation. We speculate that UTP may be a valuable target in the development of new drugs aimed at treating human systolic heart failure.

Dihydroartemisinin sensitizes Lewis lung carcinoma cells to carboplatin therapy via p38 mitogen-activated protein kinase activation

Dihydroartemisinin (DHA), a semi-synthetic derivative of artemisinin isolated from the traditional Chinese herb Artemisia annua, is an effective novel antimalarial agent. Studies have suggested that it also exhibits anticancer effects when administered alone or in combination with conventional chemotherapeutic agents. The present study investigated the therapeutic effect of DHA combined with carboplatin (CBP) on Lewis lung carcinoma (LLC) cells and the possible underlying molecular mechanisms. MTT and clonogenic assays demonstrated that the proliferation activity of LLC cells was inhibited in a dose-dependent manner by DHA combined with CBP. In addition, flow cytometry analysis revealed that cell cycle arrest was induced at the G₀/G₁ phase and apoptosis was induced following treatment with the combination. When administered in combination with CBP, DHA exhibited more effective anticancer activity compared with DHA or CBP used alone, via increased apoptosis. Following treatment with DHA with or without CBP, the expression of phosphorylated-p38 mitogen-activated protein kinase (MAPK), which can be inhibited with the selective inhibitor SB202190, was detected by western blotting. To summarize, the results of the present study indicated that DHA may sensitize LLC cells to CBP therapy via the activation of p38MAPK, which suggests that a combined treatment of DHA and CBP may be a potential novel therapeutic schedule for lung adenocarcinoma.

Abnormal Sphingolipid World in Inflammation Specific for Lysosomal Storage Diseases and Skin Disorders

Research in recent years has shown that sphingolipids are essential signalling molecules for the proper biological and structural functioning of cells. Long-term studies on the metabolism of sphingolipids have provided evidence for their role in the pathogenesis of a number of diseases. As many inflammatory diseases, such as lysosomal storage disorders and some dermatologic diseases, including psoriasis, atopic dermatitis and ichthyoses, are associated with the altered composition and metabolism of sphingolipids, more studies precisely determining the responsibilities of these compounds for disease states are required to develop novel pharmacological treatment opportunities. It is worth emphasizing that knowledge from the study of inflammatory metabolic diseases and especially the possibility of their treatment may lead to insight into related metabolic pathways, including those involved in the formation of the epidermal barrier and providing new approaches towards workable therapies.

NMR Spectroscopy to Study MAP Kinase Binding to MAP Kinase Phosphatases

NMR spectroscopy and other solution methods are increasingly being used to obtain novel insights into the mechanisms by which MAPK regulatory proteins bind and direct the activity of MAPKs. Here, we describe how interactions between the MAPK p38α and its regulatory proteins are studied using NMR spectroscopy, isothermal titration calorimetry, and small angle X-ray scattering (SAXS).

JNK and NF-κB signaling pathways are involved in cytokine changes in patients with congenital heart disease prior to and after transcatheter closure

Congenital heart disease (CHD) is a problem in the structure of the heart that is present at birth. Due to advances in interventional cardiology, CHD may currently be without surgery. The present study aimed to explore the molecular mechanism underlying CHD. A total of 200 cases of CHD treated by transcatheter closure as well as 200 controls were retrospectively assessed. Serum cytokines prior to and after treatment were assessed by reverse-transcription quantitative polymerase chain reaction analysis. Furthermore, the levels of proteins associated with c-Jun N-terminal kinase (JNK) and nuclear factor (NF)-κB were assessed by western blot analysis and immunohistochemistry. Furthermore, an animal model of CHD in young pigs was successfully constructed and treated with inhibitors of JNK and/or NF-κB to investigate the roles of these pathways in CHD. The results revealed that tumor necrosis factor-α, interleukin (IL)-6 and IL-8 were significantly elevated in the experimental group following transcatheter closure treatment, compared with those in the healthy control group, and the serum levels of the anti-inflammatory cytokine IL-10 were significantly reduced. Phosphorylated c-Jun and p65 levels in the experimental group were notably higher in the experimental group compared with the control group, but were restored to normal levels following transcatheter closure treatment. Similar results were also obtained in the pig model. The results of the present study suggested that the CHD-associated changes in cytokines, as well as their recovery following transcatheter closure treatment were associated with the JNK and NF-κB signaling pathways. The present study may provide further understanding of the underlying molecular mechanisms in CHD and propose a potential novel target for the treatment of CHD.

ALDH7A1 is a protein that protects Atlantic salmon against Aeromonas salmonicida at the early stages of infection

Aldehyde dehydrogenases (ALDHs) belong to a super-family of detoxifying proteins and perform a significant role in developing epithelial homeostasis, protecting cells from toxic aldehydes and drug resistance. However, the activity and function of these detoxifying proteins remain unknown, especially in fish. In our research, we aimed to study functions of aldehyde dehydrogenase 7A1 (ALDH7A1) in Atlantic salmon infected by Aeromonas salmonicida. Recombinant ALDH7A1 (rALDH7A1) was verified by SDS-PAGE and western blot. The molecular mass of the deduced amino acid sequence of rALDH7A1 is 58.9 kDa with an estimated pI of 7.09. Only a low complexity region (¹⁴¹yvegvgevqeyvdv¹⁵³) without a signal peptide existed in rALDH7A1. Results of ELISA indicated that rALDH7A1 exhibited apparent binding activities with A. salmonicida and its expression was highest in fish kidney. A Real-Time PCR (qRT-PCR) assay in kidneys confirmed that fish in this experiment were authentically infected and bacterial loads in rALDH7A1-adminsitered fish were significantly reduced at an early stage of infection. Meanwhile, we found the mRNA expression of NF-kβ, P-38 MAPK, caspase-3 and TNF-α were mainly up-regulated at 72 h in the kidneys and livers of highly infected fish injected with rALDH7A1, and the same variation trend existed in fish spleens at 12 h. Consistent with these observations, neutralization experiments in vivo indicated that rALDH7A1 could obviously reduce the death rate compared to the BSA and control group. Taken together, we concluded that rALDH7A1 could act in host immune defense against bacterial infection and decrease the mortality rate of Atlantic salmon at early stages of infection with A. salmonicida.

Scaffold Proteins in Gastrointestinal Tumors as a Shortcut to Oncoprotein Activation

BACKGROUND

The development of cancer involves uncontrolled cell proliferation, and multiple signaling pathways that regulate cell proliferation have been found to be dysregulated in cancers. Extracellular signal-regulated protein kinase (ERK) is one of three major subtypes in the mitogen-activated protein kinase (MAPK) families. The MAPK/ERK pathway (RAS/RAF1/MEK/ERK) plays an important part in promoting cell proliferation in response to growth factors, thereby serving as a driving signal in gastrointestinal (GI) tumors. In contrast, the p53 tumor suppressor functions as a "guardian of the genome" and stops cell proliferation when oncogenic signaling is activated.

SUMMARY

Both pathways constrain each other in healthy GI epithelium, facilitating controlled proliferation that is essential for tissue repair and regeneration. However, in GI tumors, the MAPK/ERK and p53 pathways are commonly dysregulated, in part due to abnormal posttranslational modifications. Hyperphosphorylation of the ERK protein causes sustained activation of cell proliferation, whereas hypoacetylation of the p53 protein impairs its transcriptional function and blocks cell apoptosis. Multiple scaffold proteins have been found to regulate the posttranslational modifications of ERK and p53 proteins in GI tumors.

KEY MESSAGE

Abnormal expression of scaffold proteins may contribute to the dysregulation of the MAPK and p53 signaling pathways and thereby contribute to the development of GI tumors.

PRACTICAL IMPLICATIONS

Scaffold proteins are potential biomarkers and therapeutic targets in GI tumors.

Identification of PTPN1 as a novel negative regulator of the JNK MAPK pathway using a synthetic screening for pathway-specific phosphatases

The mitogen activated protein kinase (MAPK) signaling cascades transmit extracellular stimulations to generate various cellular responses via the sequential and reversible phosphorylation of kinases. Since the strength and duration of kinase phosphorylation within the pathway determine the cellular response, both kinases and phosphatases play an essential role in the precise control of MAPK pathway activation and attenuation. Thus, the identification of pathway-specific phosphatases is critical for understanding the functional mechanisms by which the MAPK pathway is regulated. To identify phosphatases specific to the c-Jun N-terminal kinase (JNK) MAPK pathway, a synthetic screening approach was utilized in which phosphatases were individually tethered to the JNK pathway specific-JIP1 scaffold protein. Of 77 mammalian phosphatases tested, PTPN1 led to the inhibition of JNK pathway activation. Further analyses revealed that of three pathway member kinases, PTPN1 directly dephosphorylates JNK, the terminal kinase of the pathway, and negatively regulates the JNK MAPK pathway. Specifically, PTPN1 appears to regulate the overall signaling magnitude, rather than the adaptation timing, suggesting that PTPN1 might be involved in the control and maintenance of signaling noise. Finally, the negative regulation of the JNK MAPK pathway by PTPN1 was found to reduce the tumor necrosis factor α (TNFα)-dependent cell death response.

Expression of the interleukin-21 and phosphorylated extracellular signal regulated kinase 1/2 in Kimura disease

OBJECTIVE

To investigate the expressions of interleukin (IL)-21 and phosphorylated extracellular signal regulated kinase 1/2 (pERK1/2) in Kimura disease (KD) and to correlate the findings with clinical and prognostic variables.

METHODS

Immunohistochemical analysis of IL-21 and pERK1/2 was performed in 18 cases of KD and five gender- and age-matched control samples. Clinical data were extracted and patients followed up for a mean period of 32.1 months.

RESULTS

After a mean follow-up period of 32.1 months (range 1-102 months), recurrence was diagnosed as the end point for seven patients-that is, a 44% (7/16) cumulative recurrence rate. In comparison with gender- and age-matched controls, patients showed strong in situ expressions of IL-21 and pERK1/2, respectively (p<0.05). Patients with strong IL-21 staining intensity and overexpression of pERK1/2 had a lower recurrence rate than those with moderate staining intensity (p=0.049, p=0.019, respectively). However, differences were not statistically significant by gender, age, eosinophils, location, multiplicity, laterality, size, duration and primary outbreak. pERK1/2 was the independent prognostic factor (p=0.020), while age, gender, eosinophils, multiplicity, laterality, size, duration, primary outbreak and expression of IL-21 were not.

CONCLUSIONS

This study suggests that the IL-21/pERK1/2 pathway is activated in KD, and pERK1/2 might be considered as a potential prognostic indicator in KD.

An Updated Review on Marine Anticancer Compounds: The Use of Virtual Screening for the Discovery of Small-Molecule Cancer Drugs

Marine secondary metabolites are a promising source of unexploited drugs that have a wide structural diversity and have shown a variety of biological activities. These compounds are produced in response to the harsh and competitive conditions that occur in the marine environment. Invertebrates are considered to be among the groups with the richest biodiversity. To date, a significant number of marine natural products (MNPs) have been established as antineoplastic drugs. This review gives an overview of MNPs, both in research or clinical stages, from diverse organisms that were reported as being active or potentially active in cancer treatment in the past seventeen years (from January 2000 until April 2017) and describes their putative mechanisms of action. The structural diversity of MNPs is also highlighted and compared with the small-molecule anticancer drugs in clinical use. In addition, this review examines the use of virtual screening for MNP-based drug discovery and reveals that classical approaches for the selection of drug candidates based on ADMET (absorption, distribution, metabolism, excretion, and toxicity) filtering may miss potential anticancer lead compounds. Finally, we introduce a novel and publically accessible chemical library of MNPs for virtual screening purposes.

CCR5 expression in inflammatory bowel disease and its correlation with inflammatory cells and β-arrestin2 expression

OBJECTIVE

To elucidate the correlation of expression of CC chemokine receptor 5 (CCR5) with degrees of inflammatory cells infiltration and expression of β-arrestin2 in biopsic intestinal mucosa of the patients with inflammatory bowel disease (IBD).

METHODS

Paraffin sections were derived from 53 patients with active IBD, 26 patients with remissive IBD and 30 healthy people. Immunohistochemical envision two-step method was used to test the expression of CCR5 and β-arrestin2 in biopsic intestinal mucosa. HE and toluidine blue staining were used to detect the pathological cytological analysis and classification in lamina propria of colonic mucosa.

RESULTS

The positive rate, strong positive rate and immunohistochemical score of CCR5 expression in active IBD were significantly higher than that in normal controls and remissive IBD (p < .05). CCR5 expression had no obvious correlation with clinical severity, lesion distribution and endoscopic classification of active IBD. Neutrophils, eosinophils and lymphocytes in active IBD were significantly higher than that in normal controls and remissive IBD (p < .05), while the lymphocyte grade had a positive correlation with CCR5 expression (p = .042, r = .286). Mastocytes in active IBD, remissive IBD and normal controls had no obvious difference (p > .05). β-arrestin2 expression was significantly lower in active IBD than that in remissive IBD and normal controls, and it had a negative correlation with CCR5 expression (p = .01, r = -.247).

CONCLUSIONS

CCR5 is highly expressed in active IBD, and it has positive correlation with lymphocyte grade and negative correlation with expression of β-arrestin2.

IQGAP1 Mediates Hcp1-Promoted Escherichia coli Meningitis by Stimulating the MAPK Pathway

Escherichia coli-induced meningitis remains a life-threatening disease despite recent advances in the field of antibiotics-based therapeutics, necessitating continued research on its pathogenesis. The current study aims to elucidate the mechanism through which hemolysin-coregulated protein 1 (Hcp1) induces the apoptosis of human brain microvascular endothelial cells (HBMEC). Co-immunoprecipitation coupled with mass spectrometric (MS) characterization led to the identification of IQ motif containing GTPase activating protein 1 (IQGAP1) as a downstream target of Hcp1. IQGAP1 was found to be up-regulated by Hcp1 treatment and mediate the stimulation of HBMEC apoptosis. It was shown that Hcp1 could compete against Smurf1 for binding to IQGAP1, thereby rescuing the latter from ubiquitin-dependent degradation. Subsequent study suggested that IQGAP1 could stimulate the MAPK signaling pathway by promoting the phosphorylation of ERK1/2, an effect that was blocked by U0126, an MAPK inhibitor. Furthermore, U0126 also demonstrated therapeutic potential against E. coli meningitis in a mouse model. Taken together, our results suggested the feasibility of targeting the MAPK pathway as a putative therapeutic strategy against bacterial meningitis.

KSR as a therapeutic target for Ras-dependent cancers

INTRODUCTION

Targeting downstream effectors required for oncogenic Ras signaling is a potential alternative or complement to the development of more direct approaches targeting Ras in the treatment of Ras-dependent cancers. Areas covered: Here we review literature pertaining to the molecular scaffold Kinase Suppressor of Ras (KSR) and its role in promoting signals critical to tumor maintenance. We summarize the phenotypes in knockout models, describe the role of KSR in cancer, and outline the structure and function of the KSR1 and KSR2 proteins. We then focus on the most recent literature that describes the crystal structure of the kinase domain of KSR2 in complex with MEK1, KSR-RAF dimerization particularly in response to RAF inhibition, and novel attempts to target KSR proteins directly. Expert opinion: KSR is a downstream effector of Ras-mediated tumorigenesis that is dispensable for normal growth and development, making it a desirable target for the development of novel therapeutics with a high therapeutic index. Recent advances have revealed that KSR can be functionally inhibited using a small molecule that stabilizes KSR in an inactive conformation. The efficacy and potential for this novel approach to be used clinically in the treatment of Ras-driven cancers is still being investigated.

Enteric glial cells counteract Clostridium difficile Toxin B through a NADPH oxidase/ROS/JNK/caspase-3 axis, without involving mitochondrial pathways

Enteric glial cells (EGCs) are components of the intestinal epithelial barrier essential for regulating the enteric nervous system. Clostridium difficile is the most common cause of antibiotic-associated colitis, toxin B (TcdB) being the major virulence factor, due to its ability to breach the intestinal epithelial barrier and to act on other cell types. Here we investigated TcdB effects on EGCs and the activated molecular mechanisms. Already at 2 hours, TcdB triggered ROS formation originating from NADPH-oxidase, as demonstrated by their reduction in the presence of the NADPH-oxidase inhibitor ML171. Although EGCs mitochondria support almost completely the cellular ATP need, TcdB exerted weak effects on EGCs in terms of ATP and mitochondrial functionality, mitochondrial ROS production occurring as a late event. ROS activated the JNK signalling and overexpression of the proapoptotic Bim not followed by cytochrome c or AIF release to activate the downstream apoptotic cascade. EGCs underwent DNA fragmentation through activation of the ROS/JNK/caspase-3 axis, evidenced by the ability of ML171, N-acetylcysteine, and the JNK inhibitor SP600125 to inhibit caspase-3 or to contrast apoptosis. Therefore, TcdB aggressiveness towards EGCs is mainly restricted to the cytosolic compartment, which represents a peculiar feature, since TcdB primarily influences mitochondria in other cellular types.

Cannabinoid CB2 receptors are involved in the protection of RAW264.7 macrophages against the oxidative stress: an in vitro study

Research in the last decades has widely investigated the anti-oxidant properties of natural products as a therapeutic approach for the prevention and the treatment of oxidative-stress related disorders. In this context, several studies were aimed to evaluate the therapeutic potential of phytocannabinoids, the bioactive compounds of Cannabis sativa. Here, we examined the anti-oxidant ability of Cannabigerol (CBG), a non-psychotropic cannabinoid, still little known, into counteracting the hydrogen peroxide (H₂O₂)-induced oxidative stress in murine RAW264.7 macrophages. In addition, we tested selective receptor antagonists for cannabinoid receptors and specifically CB1R (SR141716A) and CB2R (AM630) in order to investigate through which CBG may exert its action. Taken together, our in vitro results showed that CBG is able to counteract oxidative stress by activation of CB2 receptors. CB2 antagonist pre-treatment indeed blocked the protective effects of CBG in H₂O₂ stimulated macrophages, while CB1R was not involved. Specifically, CBG exhibited a potent action in inhibiting oxidative stress, by down-regulation of the main oxidative markers (iNOS, nitrotyrosine and PARP-1), by preventing IκB-α phosphorylation and translocation of the nuclear factor-κB (NF-κB) and also via the modulation of MAP kinases pathway. On the other hand, CBG was found to increase anti-oxidant defense of cells by modulating superoxide dismutase-1 (SOD-1) expression and thus inhibiting cell death (results focused on balance between Bax and Bcl-2). Based on its anti-oxidant activities, CBG may hold great promise as an anti-oxidant agent and therefore used in clinical practice as a new approach in oxidative-stress related disorders.

BPGAP1 spatially integrates JNK/ERK signaling crosstalk in oncogenesis

Simultaneous hyperactivation of stress-activated protein kinase/c-Jun N-terminal protein kinase (SAPK/JNK) and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK) signaling cascades has been reported in carcinogenesis. However, how they are integrated to promote oncogenesis remains unknown. By analyzing breast invasive carcinoma database (The Cancer Genome Altas), we found that the mRNA expression levels of both JNK1 and ERK2 are positively correlated with the mRNA level of EEA1, an endosome associated protein, indicating the potential JNK/ERK crosstalk at endosome. Unbiased screen of different endosome-associated Rab GTPases reveals that late endosome serves as a unique platform to integrate JNK/ERK signaling. Furthermore, we identify that BPGAP1 (a BCH domain-containing, Cdc42GAP-like Rho GTPase-activating protein) promotes MEK partner 1 (MP1)-induced ERK activation on late endosome through scaffolding MP1/MEK1 complex. This regulatory function requires phosphorylation of BPGAP1 by JNK at its C terminal tail (Ser424) to unlock its autoinhibitory conformation. Consequently, phosphorylated BPGAP1 facilitates endosomal ERK signaling transduction to the nucleus, driving cell proliferation and transformation via the ERK-Myc-CyclinA axis. BPGAP1 therefore provides a crucial spatiotemporal checkpoint where JNK and MP1/MEK1 work in concert to regulate endosomal and nuclear ERK signaling in cell proliferation control.

Absence of IQGAP1 Protein Leads to Insulin Resistance

Insulin binds to the insulin receptor (IR) and induces tyrosine phosphorylation of the receptor and insulin receptor substrate-1 (IRS-1), leading to activation of the PKB/Akt and MAPK/ERK pathways. IQGAP1 is a scaffold protein that interacts with multiple binding partners and integrates diverse signaling cascades. Here we show that IQGAP1 associates with both IR and IRS-1 and influences insulin action. In vitro analysis with pure proteins revealed that the IQ region of IQGAP1 binds directly to the intracellular domain of IR. Similarly, the phosphotyrosine-binding domain of IRS-1 mediates a direct interaction with the C-terminal tail of IQGAP1. Consistent with these observations, both IR and IRS-1 co-immunoprecipitated with IQGAP1 from cells. Investigation of the functional effects of the interactions revealed that in the absence of IQGAP1, insulin-stimulated phosphorylation of Akt and ERK, as well as the association of phosphatidylinositol 3-kinase with IRS-1, were significantly decreased. Importantly, loss of IQGAP1 results in impaired insulin signaling and glucose homeostasis in vivo Collectively, these data reveal that IQGAP1 is a scaffold for IR and IRS-1 and implicate IQGAP1 as a participant in insulin signaling.

Negative feedback regulation of the ERK1/2 MAPK pathway

The extracellular signal-regulated kinase 1/2 (ERK1/2) mitogen-activated protein kinase (MAPK) signalling pathway regulates many cellular functions, including proliferation, differentiation, and transformation. To reliably convert external stimuli into specific cellular responses and to adapt to environmental circumstances, the pathway must be integrated into the overall signalling activity of the cell. Multiple mechanisms have evolved to perform this role. In this review, we will focus on negative feedback mechanisms and examine how they shape ERK1/2 MAPK signalling. We will first discuss the extensive number of negative feedback loops targeting the different components of the ERK1/2 MAPK cascade, specifically the direct posttranslational modification of pathway components by downstream protein kinases and the induction of de novo gene synthesis of specific pathway inhibitors. We will then evaluate how negative feedback modulates the spatiotemporal signalling dynamics of the ERK1/2 pathway regarding signalling amplitude and duration as well as subcellular localisation. Aberrant ERK1/2 activation results in deregulated proliferation and malignant transformation in model systems and is commonly observed in human tumours. Inhibition of the ERK1/2 pathway thus represents an attractive target for the treatment of malignant tumours with increased ERK1/2 activity. We will, therefore, discuss the effect of ERK1/2 MAPK feedback regulation on cancer treatment and how it contributes to reduced clinical efficacy of therapeutic agents and the development of drug resistance.

Structural Basis for the Subversion of MAP Kinase Signaling by an Intrinsically Disordered Parasite Secreted Agonist

The causative agent of toxoplasmosis, the intracellular parasite Toxoplasma gondii, delivers a protein, GRA24, into the cells it infects that interacts with the mitogen-activated protein (MAP) kinase p38α (MAPK14), leading to activation and nuclear translocation of the host kinase and a subsequent inflammatory response that controls the progress of the parasite. The purification of a recombinant complex of GRA24 and human p38α has allowed the molecular basis of this activation to be determined. GRA24 is shown to be intrinsically disordered, binding two kinases that act independently, and is the only factor required to bypass the canonical mitogen-activated protein kinase activation pathway. An adapted kinase interaction motif (KIM) forms a highly stable complex that competes with cytoplasmic regulatory partners. In addition, the recombinant complex forms a powerful in vitro tool to evaluate the specificity and effectiveness of p38α inhibitors that have advanced to clinical trials, as it provides a hitherto unavailable stable and highly active form of p38α.

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Toxoplasmosis controls its host immune response via a protein effector, GRA24

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A recombinant complex of GRA24 and MAPK p38α demonstrates how the protein works

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An adapted KIM domain ensures activation and a sustained inflammatory response

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The recombinant complex is useful in the evaluation of p38 inhibitors

Adipokine CTRP6 improves PPARγ activation to alleviate angiotensin II-induced hypertension and vascular endothelial dysfunction in spontaneously hypertensive rats

Angiotensin II (AngII) is the most important component of angiotensin, which has been regarded as a major contributor to the incidence of hypertension and vascular endothelial dysfunction. The adipocytokine C1q/TNF-related protein 6 (CTRP6) was recently reported to have multiple protective effects on cardiac and cardiovascular function. However, the exact role of CTRP6 in the progression of AngII induced hypertension and vascular endothelial function remains unclear. Here, we showed that serum CTRP6 content was significantly downregulated in SHRs, accompanied by a marked increase in arterial systolic pressure and serum AngII, CRP and ET-1 content. Then, pcDNA3.1-mediated CTRP6 delivery or CTRP6 siRNA was injected into SHRs. CTRP6 overexpression caused a significant decrease in AngII expression and AngII-mediated hypertension and vascular endothelial inflammation. In contrast, CTRP6 knockdown had the opposite effect to CTRP6 overexpression. Moreover, we found that CTRP6 positively regulated the activation of the ERK1/2 signaling pathway and the expression of peroxisome proliferator-activated receptor γ (PPARγ), a recently proven negative regulator of AngII, in the brain and vascular endothelium of SHRs. Finally, CTRP6 was overexpressed in endothelial cells, and caused a significant increase in PPARγ activation and suppression in AngII-mediated vascular endothelial dysfunction and apoptosis. The effect of that could be rescued by the ERK inhibitor PD98059. In contrast, silencing CTRP6 suppressed PPARγ activation and exacerbated AngII-mediated vascular endothelial dysfunction and apoptosis. In conclusion, CTRP6 improves PPARγ activation and alleviates AngII-induced hypertension and vascular endothelial dysfunction.

Free fatty acid G-protein coupled receptor signaling in M1 skewed white adipose tissue macrophages

Obesity is associated with the establishment and maintenance of a low grade, chronically inflamed state in the white adipose tissue (WAT) of the body. The WAT macrophage population is a major cellular participant in this inflammatory process that significantly contributes to the pathophysiology of the disease, with the adipose depots of obese individuals, relative to lean counterparts, having an elevated number of macrophages that are skewed towards a pro-inflammatory phenotype. Alterations in the WAT lipid micro-environment, and specifically the availability of free fatty acids, are believed to contribute towards the obesity-related quantitative and functional changes observed in these cells. This review specifically addresses the involvement of the five G-protein coupled free fatty acid receptors which bind exogenous FFAs and signal in macrophages. Particular focus is placed on the involvement of these receptors in macrophage migration and cytokine production, two important aspects that modulate inflammation.

The function of Shoc2: A scaffold and beyond

The extracellular signal-regulated kinase (ERK1/2) cascade regulates a myriad of functions in multicellular organisms. Scaffold proteins provide critical spatial and temporal control over the specificity of signaling. Shoc2 is a scaffold that accelerates activity of the ERK1/2 pathway. Loss of Shoc2 expression in mice results in embryonic lethality, thus highlighting the essential role of Shoc2 in embryogenesis. In agreement, patients carrying mutated Shoc2 suffer from a wide spectrum of developmental deficiencies. Efforts to understand the mechanisms by which Shoc2 controls ERK1/2 activity revealed the intricate machinery that governs the ability of Shoc2 to transduce signals of the ERK1/2 pathway. Understanding the mechanisms by which Shoc2 contributes to a high degree of specificity of ERK1/2 signaling as well as deciphering the biological functions of Shoc2 in development and human disorders are major unresolved questions.

Scaffold Proteins Regulating Extracellular Regulated Kinase Function in Cardiac Hypertrophy and Disease

The mitogen activated protein kinase (MAPK)-extracellular regulated kinase 1/2 (ERK1/2) pathway is a central downstream signaling pathway that is activated in cardiac muscle cells during mechanical and agonist-mediated hypertrophy. Studies in genetic mouse models deficient in ERK-associated MAPK components pathway have further reinforced a direct role for this pathway in stress-induced cardiac hypertrophy and disease. However, more recent studies have highlighted that these signaling pathways may exert their regulatory functions in a more compartmentalized manner in cardiac muscle. Emerging data has uncovered specific MAPK scaffolding proteins that tether MAPK/ERK signaling specifically at the sarcomere and plasma membrane in cardiac muscle and show that deficiencies in these scaffolding proteins alter ERK activity and phosphorylation, which are then critical in altering the cardiac myocyte response to stress-induced hypertrophy and disease progression. In this review, we provide insights on ERK-associated scaffolding proteins regulating cardiac myofilament function and their impact on cardiac hypertrophy and disease.

Shoc2-tranduced ERK1/2 motility signals--Novel insights from functional genomics

The extracellular signal-regulated kinase 1 and 2 (ERK1/2) pathway plays a central role in defining various cellular fates. Scaffold proteins modulating ERK1/2 activity control growth factor signals transduced by the pathway. Here, we analyzed signals transduced by Shoc2, a critical positive modulator of ERK1/2 activity. We found that loss of Shoc2 results in impaired cell motility and delays cell attachment. As ERKs control cellular fates by stimulating transcriptional response, we hypothesized that the mechanisms underlying changes in cell adhesion could be revealed by assessing the changes in transcription of Shoc2-depleted cells. Using quantitative RNA-seq analysis, we identified 853 differentially expressed transcripts. Characterization of the differentially expressed genes showed that Shoc2 regulates the pathway at several levels, including expression of genes controlling cell motility, adhesion, crosstalk with the transforming growth factor beta (TGFβ) pathway, and expression of transcription factors. To understand the mechanisms underlying delayed attachment of cells depleted of Shoc2, changes in expression of the protein of extracellular matrix (lectin galactoside-binding soluble 3-binding protein; LGALS3BP) were functionally analyzed. We demonstrated that delayed adhesion of the Shoc2-depleted cells is a result of attenuated expression and secretion of LGALS3BP. Together our results suggest that Shoc2 regulates cell motility by modulating ERK1/2 signals to cell adhesion.

Enhancement of ICAM-1 via the JAK2/STAT3 signaling pathway in a rat model of severe acute pancreatitis-associated lung injury

Acute lung injury (ALI), which is associated with severe acute pancreatitis (SAP), results from damage to the pulmonary microvascular endothelial cells (PMVECs), which in turn leads to high levels of inflammatory cytokines that destroy PMVECs. However, the molecular mechanisms underlying SAP-associated ALI (SAP-ALI) are currently not well understood. Intercellular adhesion molecule-1 (ICAM-1) has been implicated in the persistent migration and accumulation of neutrophils and macrophages, which in turn has been associated with the increased permeability of microvascular endothelial cells. Signal transduction via the Janus kinase-2 (JAK2)/signal transducer and activator of transcription-3 (STAT3) transcription factors has been shown to be involved in inflammation. The present study aimed to investigate the expression levels of ICAM-1 and JAK2/STAT3 signaling components in a rat model of SAP-ALI. SAP was induced in the rat model, and dexamethasone (DEX) was administered to the treatment group. Subsequently, ICAM-1, interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α, JAK2, STAT3 and nuclear factor (NF)-κB mRNA expression levels were determined using reverse transcription-polymerase chain reaction; ICAM-1 protein expression levels were determined using western blotting; and IL-6, IL-8 and TNF-α levels were measured via an enzyme-linked immunosorbent assay. In addition, an immunohistochemical analysis of ICAM-1, NF-κB, JAK2 and STAT3 was conducted, and the protein expression and cell morphology of the lungs in all rats was analyzed. ICAM-1 mRNA and protein expression levels were significantly increased following induction of SAP, and were significantly decreased in the DEX-treated group. Furthermore, treatment with DEX significantly reduced serum expression levels of IL-6, IL-8 and TNF-α and decreased expression levels of NF-κB, JAK2 and STAT3 in the lung tissue, as compared with the untreated SAP group. The present study demonstrated that DEX treatment was able to suppress ICAM-1 mRNA and protein expression in a rat model of SAP-ALI via the inhibition of IL-6 and TNF-α-induced JAK2/STAT3 activation; thus suggesting that DEX treatment may be considered a potential strategy in the treatment of patients with SAP-ALI.

Hydrolyzed fish proteins reduced activation of caspase-3 in H2O2 induced oxidative stressed liver cells isolated from Atlantic salmon (Salmo salar)

Hydrolyzed fish proteins (H-pro) contains high concentrations of free amino acids and low molecular peptides that potentially benefit health. The following study aimed to test whether the water soluble phase of H-pro could reduce apoptosis and inflammation in primary liver cells isolated from Atlantic salmon following H₂O₂ provoked oxidative stress. Cells were grown as monocultures or co-cultured with head kidney cells to assess possible cross talk in inflammation and metabolism during treatments. Cells were grown in media with or without H-pro for 2 days before being stressed with 200 µM H₂O₂ then harvested 24 h post exposure. Both treatments were compared to the respective treatments without H₂O₂ supplementation. Oxidative stressed cells had increased activation of caspase-3, but supplementation with H-pro in the media prior to the oxidative stress reduced caspase-3 activation. In conclusion, free amino acids and low molecular weight peptides from H-pro attenuated oxidative stress, and made cells able to withstand apoptosis after H₂O₂ provoked oxidative stress.

Spatial control of Shoc2-scaffold-mediated ERK1/2 signaling requires remodeling activity of the ATPase PSMC5

The scaffold protein Shoc2 accelerates activity of the ERK1 and ERK2 (ERK1/2, also known as MAPK3 and MAPK1) pathway. Mutations in Shoc2 result in Noonan-like RASopathy, a developmental disorder with a wide spectrum of symptoms. The amplitude of the ERK1/2 signals transduced through the complex is fine-tuned by the HUWE1-mediated ubiquitylation of Shoc2 and its signaling partner RAF-1. Here, we provide a mechanistic basis of how ubiquitylation of Shoc2 and RAF-1 is controlled. We demonstrate that the newly identified binding partner of Shoc2, the (AAA+) ATPase PSMC5, triggers translocation of Shoc2 to endosomes. At the endosomes, PSMC5 displaces the E3 ligase HUWE1 from the scaffolding complex to attenuate ubiquitylation of Shoc2 and RAF-1. We show that a RASopathy mutation that changes the subcellular distribution of Shoc2 leads to alterations in Shoc2 ubiquitylation due to the loss of accessibility to PSMC5. In summary, our results demonstrate that PSMC5 is a new and important player involved in regulating ERK1/2 signal transmission through the remodeling of Shoc2 scaffold complex in a spatially-defined manner.

Kaempferol and inflammation: From chemistry to medicine

Inflammation is an important process of human healing response, wherein the tissues respond to injuries induced by many agents including pathogens. It is characterized by pain, redness and heat in the injured tissues. Chronic inflammation seems to be associated with different types of diseases such as arthritis, allergies, atherosclerosis, and even cancer. In recent years natural product based drugs are considered as the novel therapeutic strategy for prevention and treatment of inflammatory diseases. Among the different types of phyto-constituents present in natural products, flavonoids which occur in many vegetable foods and herbal medicines are considered as the most active constituent, which has the potency to ameliorate inflammation under both in vitro and in vivo conditions. Kaempferol is a natural flavonol present in different plant species, which has been described to possess potent anti-inflammatory properties. Despite the voluminous literature on the anti-inflammatory effects of kaempferol, only very limited review articles has been published on this topic. Hence the present review is aimed to provide a critical overview on the anti-inflammatory effects and the mechanisms of action of kaempferol, based on the current scientific literature. In addition, emphasis is also given on the chemistry, natural sources, bioavailability and toxicity of kaempferol.

IQGAP1 and IQGAP3 Serve Individually Essential Roles in Normal Epidermal Homeostasis and Tumor Progression

IQGAP scaffolding proteins regulate many essential cellular processes including growth factor receptor signaling, cytoskeletal rearrangement, adhesion and proliferation, and are highly expressed in many cancers. Using genetically engineered human skin tissue in vivo, we demonstrate that diminished, sub-physiologic expression of IQGAP1 or IQGAP3 is sufficient to maintain normal epidermal homeostasis, while significantly higher levels are required to support tumorigenesis. To target this tumor-specific IQGAP requirement in vivo, we engineered epidermal keratinocytes to express individual IQGAP protein domains designed to compete with endogenous IQGAPs for effector protein binding. Expression of the IQGAP1-IQM decoy domain in epidermal tissue in vivo inhibits oncogenic Ras-driven MAPK signaling and antagonizes tumorigenesis, without disrupting normal epidermal proliferation or differentiation. These findings define essential non-redundant roles for IQGAP1 and IQGAP3 in epidermis, and demonstrate the potential of IQGAP antagonism for cancer therapy.

A mycobacterial phosphoribosyltransferase promotes bacillary survival by inhibiting oxidative stress and autophagy pathways in macrophages and zebrafish

Mycobacterium tuberculosis employs various strategies to modulate host immune responses to facilitate its persistence in macrophages. The M. tuberculosis cell wall contains numerous glycoproteins with unknown roles in pathogenesis. Here, by using Concanavalin A and LC-MS analysis, we identified a novel mannosylated glycoprotein phosphoribosyltransferase, encoded by Rv3242c from M. tuberculosis cell walls. Homology modeling, bioinformatic analyses, and an assay of phosphoribosyltransferase activity in Mycobacterium smegmatis expressing recombinant Rv3242c (MsmRv3242c) confirmed the mass spectrometry data. Using Mycobacterium marinum-zebrafish and the surrogate MsmRv3242c infection models, we proved that phosphoribosyltransferase is involved in mycobacterial virulence. Histological and infection assays showed that the M. marinum mimG mutant, an Rv3242c orthologue in a pathogenic M. marinum strain, was strongly attenuated in adult zebrafish and also survived less in macrophages. In contrast, infection with wild type and the complemented ΔmimG:Rv3242c M. marinum strains showed prominent pathological features, such as severe emaciation, skin lesions, hemorrhaging, and more zebrafish death. Similarly, recombinant MsmRv3242c bacteria showed increased invasion in non-phagocytic epithelial cells and longer intracellular survival in macrophages as compared with wild type and vector control M. smegmatis strains. Further mechanistic studies revealed that the Rv3242c- and mimG-mediated enhancement of intramacrophagic survival was due to inhibition of autophagy, reactive oxygen species, and reduced activities of superoxide dismutase and catalase enzymes. Infection with MsmRv3242c also activated the MAPK pathway, NF-κB, and inflammatory cytokines. In summary, we show that a novel mycobacterial mannosylated phosphoribosyltransferase acts as a virulence and immunomodulatory factor, suggesting that it may constitute a novel target for antimycobacterial drugs.

IQGAP1: insights into the function of a molecular puppeteer

The intracellular spatiotemporal organization of signaling events is critical for normal cellular function. In response to environmental stimuli, cells utilize highly organized signaling pathways that are subject to multiple layers of regulation. However, the molecular mechanisms that coordinate these complex processes remain an enigma. Scaffolding proteins (scaffolins) have emerged as critical regulators of signaling pathways, many of which have well-described functions in immune cells. IQGAP1, a highly conserved cytoplasmic scaffold protein, is able to curb, compartmentalize, and coordinate multiple signaling pathways in a variety of cell types. IQGAP1 plays a central role in cell-cell interaction, cell adherence, and movement via actin/tubulin-based cytoskeletal reorganization. Evidence also implicates IQGAP1 as an essential regulator of the MAPK and Wnt/β-catenin signaling pathways. Here, we summarize the recent advances on the cellular and molecular biology of IQGAP1. We also describe how this pleiotropic scaffolin acts as a true molecular puppeteer, and highlight the significance of future research regarding the role of IQGAP1 in immune cells.

IQGAPs choreograph cellular signaling from the membrane to the nucleus

Since its discovery in 1994, recognized cellular functions for the scaffold protein IQGAP1 have expanded immensely. Over 100 unique IQGAP1-interacting proteins have been identified, implicating IQGAP1 as a critical integrator of cellular signaling pathways. Initial research established functions for IQGAP1 in cell-cell adhesion, cell migration, and cell signaling. Recent studies have revealed additional IQGAP1 binding partners, expanding the biological roles of IQGAP1. These include crosstalk between signaling cascades, regulation of nuclear function, and Wnt pathway potentiation. Investigation of the IQGAP2 and IQGAP3 homologs demonstrates unique functions, some of which differ from those of IQGAP1. Summarized here are recent observations that enhance our understanding of IQGAP proteins in the integration of diverse signaling pathways.

Butein suppresses ICAM-1 expression through the inhibition of IκBα and c-Jun phosphorylation in TNF-α- and PMA-treated HUVECs

Butein (3,4,2',4'-tetrahydroxychalcone), a flavonoid derivative, has been reported to show several biological actions, including anti-inflammatory and anti-cancer. However, the possible molecular mechanisms involved are poorly understood. Treatment of human umbilical vein endothelial cells (HUVECs) with butein significantly inhibited cell surface intercellular adhesion molecule-1 (ICAM-1) expression, ICAM-1 protein synthesis, and mRNA expression induced by tumor necrotic factor-α (TNF-α) and/or phorbol 12-myristate 13-acetate (PMA). Electrophoretic mobility shift assay revealed that butein blocked activation of transcription factors, nuclear factor-κB (NF-κB) and activator protein-1 (AP-1), induced by TNF-α and PMA. Moreover, butein abolished TNF-α- and PMA-induced IκBα phosphorylation, which participates in NF-κB activation, and PMA-induced phosphorylation of c-Jun, a subunit composed of AP-1. In vitro, butein inhibited the phosphorylation of c-Jun, binding to GST beads, mediated by JNK isolated from PMA-treated cells. The inhibitory action of butein on the JNK-mediated in vitro c-Jun phosphorylation was abrogated in the presence of ATP. These results indicate that in HUVECs, butein suppresses the expression of ICAM-1 mRNA and protein through the inhibition of the activation of NF-κB and AP-1 induced by TNF-α and PMA, that the inhibitory action of butein on NF-κB activation results from the inhibition of IκBα phosphorylation by IκB kinase (IKK), and that the inactivation of PMA-activated AP-1 by butein is due to the blocking of JNK-mediated c-Jun phosphorylation through the inhibition of ATP binding.

Shoc2/Sur8 protein regulates neurite outgrowth

The Shoc2 protein has been implicated in the positive regulation of the Ras-ERK pathway by increasing the functional binding interaction between Ras and Raf, leading to increased ERK activity. Here we found that Shoc2 overexpression induced sustained ERK phosphorylation, notably in the case of EGF stimulation, and Shoc2 knockdown inhibited ERK activation. We demonstrate that ectopic overexpression of human Shoc2 in PC12 cells significantly promotes neurite extension in the presence of EGF, a stimulus that induces proliferation rather than differentiation in these cells. Finally, Shoc2 depletion reduces both NGF-induced neurite outgrowth and ERK activation in PC12 cells. Our data indicate that Shoc2 is essential to modulate the Ras-ERK signaling outcome in cell differentiation processes involved in neurite outgrowth.

p38MAPK activation mediates tumor necrosis factor-α-induced apoptosis in glioma cells

Gliomas are a type of heterogeneous primary central nervous system tumor, which arise from the glial cells; these types of tumor generally respond poorly to surgery, radiation and conventional chemotherapy. Tumor necrosis factor‑α (TNF‑α) has been suggested to produce an antitumor effect by binding to specific receptors on the tumor cell membrane to induce apoptosis. TNF‑α is known to activate a number of signaling pathways, including extracellular signal‑regulated protein kinase, c‑Jun N‑terminal kinase (JNK), p38 mitogen‑activated protein kinase (p38MAPK), nuclear factor‑κB and caspase cascades, depending on the cell type. However, the involvement of p38MAPK signaling in TNF‑α‑induced apoptosis in glioma cells remains unclear. In the current study, the role of p38MAPK in TNF‑α‑induced apoptosis in rat glioma C6 cells was investigated. TNF‑α was observed to induce cell apoptosis and the phosphorylation of p38MAPK in C6 cells. In addition, the inhibition of p38MAPK markedly reduced TNF‑α‑induced apoptosis, while JNK inhibition did not affect apoptosis. Furthermore, p38MAPK transfection altered the cell cycle of glioma cells and increased the rate of apoptosis. It also led to an increase in the level of soluble TNF‑α in the culture supernatant and membrane TNF receptor I levels in tumor cells. In conclusion, the results of the current study demonstrated that the activation of p38MAPK mediates TNF‑α‑induced apoptosis in glioma C6 cells, suggesting p38MAPK as a potential target for glioma therapy.

A mouse splice-site mutant and individuals with atypical chromosome 22q11.2 deletions demonstrate the crucial role for crkl in craniofacial and pharyngeal development

The 22q11.2 deletion syndrome (22q11DS) is thought to be a contiguous gene syndrome caused by haploinsufficiency for a variable number of genes with overlapping function during the development of the craniofacial, pharyngeal and cardiac structures. The complexity of genetic and developmental anomalies resulting in 22q11DS has made attributing causation to specific genes difficult. The CRKL gene resides within the common 3-Mb region, most frequently affected in 22q11DS, and has been shown to play an essential role in the development of tissues affected in 22q11DS. Here, we report the characterisation of a mouse strain we named 'snoopy', harbouring a novel Crkl splice-site mutation that results in a loss of Crkl expression. The snoopy strain exhibits a variable phenotype that includes micrognathia, pharyngeal occlusion, aglossia and holoprosencephaly, and altered retinoic acid and endothelin signalling. Together, these features are reminiscent of malformations occurring in auriculocondylar syndrome and agnathia-otocephaly complex, 2 conditions not previously associated with the CRKL function. Comparison of the features of a cohort of patients harbouring small 22q11.2 deletions centred over the CRKL gene, but sparing TBX1, highlights the role of CRKL in contributing to the craniofacial features of 22q11DS. These analyses demonstrate the central role of Crkl in regulating signalling events in the developing oropharyngeal complex and its potential to contribute to dysmorphology.

The fish oil ingredient, docosahexaenoic acid, activates cytosolic phospholipase A₂ via GPR120 receptor to produce prostaglandin E₂ and plays an anti-inflammatory role in macrophages

Docosahexaenoic acid (DHA) is one of the major ingredients of fish oil and has been reported to have anti-inflammatory properties mediated through the GPR120 receptor. Whether cytosolic phospholipase A2 (cPLA2 ) and lipid mediators produced from cPLA2 activation are involved in the anti-inflammatory role of DHA in macrophages has not been reported. We report here that DHA and the GPR120 agonist, GW9508, activate cPLA2 and cyclooxygenase 2 (COX-2), and cause prostaglandin E2 (PGE2) release in a murine macrophage cell line RAW264.7 and in human primary monocyte-derived macrophages. DHA and GW9508 activate cPLA2 via GPR120 receptor, G protein Gαq and scaffold protein β-arrestin 2. Extracellular signal-regulated kinase 1/2 activation is involved in DHA- and GW9508-induced cPLA2 activation, but not p38 mitogen-activated protein kinase. The anti-inflammatory role of DHA and GW9508 is in part via activation of cPLA2 , COX-2 and production of PGE2 as a cPLA2 inhibitor or a COX-2 inhibitor partially reverses the DHA- and GW9508-induced inhibition of lipopolysaccharide-induced interleukin-6 secretion. The cPLA2 product arachidonic acid and PGE2 also play an anti-inflammatory role. This effect of PGE2 is partially through inhibition of the nuclear factor-κB signalling pathway and through the EP4 receptor of PGE2 because an EP4 inhibitor or knock-down of EP4 partially reverses DHA inhibition of lipopolysaccharide-induced interleukin-6 secretion. Hence, DHA has an anti-inflammatory effect partially through induction of PGE2.

MAPK involvement in cytokine production in response to Corynebacterium pseudotuberculosis infection

Background

Caseous lymphadenitis (CL) is a contagious infectious disease of small ruminants caused by Corynebacterium pseudotuberculosis. Is characterized by the formation of abscesses in the lymph nodes and intestines of infected animals, induced by inflammatory cytokines. The production of cytokines, such as IL-10, TNF-α, IL-4 and IFN-γ, is regulated by mitogen-activated protein kinase (MAPK) pathway activation. The present study investigated the involvement of MAPK pathways (MAPK p38, ERK 1 and ERK 2) with respect to the production of cytokines induced by antigens secreted by C. pseudotuberculosis over a 60-day course of infection. CBA mice (n = 25) were divided into three groups and infected with 10² colony forming units (CFU) of attenuated strain T1, 10² CFU of virulent strain VD57 or sterile saline solution and euthanized after 30 or 60 days. Murine splenocytes were treated with specific inhibitors (MAPK p38 inhibitor, ERK 1/2 inhibitor or ERK 2 inhibitor) and cultured with secreted antigens obtained from pathogenic bacteria (SeT1 or SeVD57).

Results

The MAPK pathways evaluated were observed to be involved in the production of IL-10, under stimulation by secreted antigens, while the MAPK p38 and ERK 1 pathways were shown to be primarily involved in TNF-α production. By contrast, no involvement of the MAPK p38 and ERK 1 and 2 pathways was observed in IFN-γ production, while the ERK 2 pathway demonstrated involvement in IL-4 production only in the mouse splenocytes infected with VD57 under stimulation by SeT1.

Conclusion

The authors hypothesize that MAPK p38 and ERK 1 pathways with respect to TNF-α production, as well as the MAPK p38 and ERK 1 and 2 pathways in relation to IL-10 production under infection by C. pseudotuberculosis are important regulators of cellular response. Additionally, the lack of the MAPK p38 and ERK 1/2 pathways in IFN-γ production in infected CBA murine cells stimulated with the two secreted/excreted antigens, in IL-4 production showing involvement only via the ERK 2 pathway under stimulation by SeT1 antigen during 60-day infection period with the virulent strain, suggests that these pathways regulated the production of pro-inflammatory and regulatory cytokines in the splenic cells of CBA mice.

Homeostatic regulation of meiotic DSB formation by ATM/ATR

Ataxia-telangiectasia mutated (ATM) and RAD3-related (ATR) are widely known as being central players in the mitotic DNA damage response (DDR), mounting responses to DNA double-strand breaks (DSBs) and single-stranded DNA (ssDNA) respectively. The DDR signalling cascade couples cell cycle control to damage-sensing and repair processes in order to prevent untimely cell cycle progression while damage still persists [1]. Both ATM/ATR are, however, also emerging as essential factors in the process of meiosis; a specialised cell cycle programme responsible for the formation of haploid gametes via two sequential nuclear divisions. Central to achieving accurate meiotic chromosome segregation is the introduction of numerous DSBs spread across the genome by the evolutionarily conserved enzyme, Spo11. This review seeks to explore and address how cells utilise ATM/ATR pathways to regulate Spo11-DSB formation, establish DSB homeostasis and ensure meiosis is completed unperturbed.

HUWE1 is a molecular link controlling RAF-1 activity supported by the Shoc2 scaffold

Scaffold proteins play a critical role in controlling the activity of the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway. Shoc2 is a leucine-rich repeat scaffold protein that acts as a positive modulator of ERK1/2 signaling. However, the precise mechanism by which Shoc2 modulates the activity of the ERK1/2 pathway is unclear. Here we report the identification of the E3 ubiquitin ligase HUWE1 as a binding partner and regulator of Shoc2 function. HUWE1 mediates ubiquitination and, consequently, the levels of Shoc2. Additionally, we show that both Shoc2 and HUWE1 are necessary to control the levels and ubiquitination of the Shoc2 signaling partner, RAF-1. Depletion of HUWE1 abolishes RAF-1 ubiquitination, with corresponding changes in ERK1/2 pathway activity occurring. Our results indicate that the HUWE1-mediated ubiquitination of Shoc2 is the switch that regulates the transition from an active to an inactive state of the RAF-1 kinase. Taken together, our results demonstrate that HUWE1 is a novel player involved in regulating ERK1/2 signal transmission through the Shoc2 scaffold complex.

Reassembly of JIP1 scaffold complex in JNK MAP kinase pathway using heterologous protein interactions

Formation of signaling protein complexes is crucial for proper signal transduction. Scaffold proteins in MAP kinase pathways are thought to facilitate complex assembly, thereby promoting efficient and specific signaling. To elucidate the assembly mechanism of scaffold complexes in mammals, we attempted to rationally rewire JIP1-dependent JNK MAP kinase pathway via alternative assembly of JIP1 complex. When JIP1-JNK docking interaction in the complex was replaced with heterologous protein interaction domains, such as PDZ domains and JNK-binding domains, a functional scaffold complex was reconstituted, and JNK signaling was rescued. Reassembly of JIP1 complex using heterologous protein interactions was sufficient for restoring of JNK MAP kinase pathway to induce signaling responses, including JNK activation and cell death. These results suggest a simple yet modular mechanism for JIP1 scaffold assembly in mammals.

Genetically encoded molecular probes to visualize and perturb signaling dynamics in living biological systems

In this Commentary, we discuss two sets of genetically encoded molecular tools that have significantly enhanced our ability to observe and manipulate complex biochemical processes in their native context and that have been essential in deepening our molecular understanding of how intracellular signaling networks function. In particular, genetically encoded biosensors are widely used to directly visualize signaling events in living cells, and we highlight several examples of basic biosensor designs that have enabled researchers to capture the spatial and temporal dynamics of numerous signaling molecules, including second messengers and signaling enzymes, with remarkable detail. Similarly, we discuss a number of genetically encoded biochemical perturbation techniques that are being used to manipulate the activity of various signaling molecules with far greater spatial and temporal selectivity than can be achieved using standard pharmacological or genetic techniques, focusing specifically on examples of chemically driven and light-inducible perturbation strategies. We then describe recent efforts to combine these diverse and powerful molecular tools into a unified platform that can be used to elucidate the molecular details of biological processes that may potentially extend well beyond the realm of signal transduction.

Arrestin-dependent activation of JNK family kinases

The activity of all mitogen-activated protein kinases (MAPKs) is stimulated via phosphorylation by upstream MAPK kinases (MAPKK), which are in their turn activated via phosphorylation by MAPKK kinases (MAPKKKs). The cells ensure the specificity of signaling in these cascades by employing a variety of scaffolding proteins that bind matching MAPKKKs, MAPKKs, and MAPKs. All four vertebrate arrestin subtypes bind JNK3, but only arrestin-3 serves as a scaffold, promoting JNK3 activation in intact cells. Arrestin-3-mediated JNK3 activation does not depend on arrestin-3 interaction with G protein-coupled receptors (GPCRs), as demonstrated by the ability of some arrestin mutants that cannot bind receptors to activate JNK3, whereas certain mutants with enhanced GPCR binding fail to promote JNK3 activation. Recent findings suggest that arrestin-3 directly binds both MAPKKs necessary for JNK activation and facilitates JNK3 phosphorylation at both Thr (by MKK4) and Tyr (by MKK7). JNK3 is expressed in a limited set of cell types, whereas JNK1 and JNK2 isoforms are as ubiquitous as arrestin-3. Recent study showed that arrestin-3 facilitates the activation of JNK1 and JNK2, scaffolding MKK4/7-JNK1/2/3 signaling complexes. In all cases, arrestin-3 acts by bringing the kinases together: JNK phosphorylation shows biphasic dependence on arrestin-3, being enhanced at lower and suppressed at supraoptimal concentrations. Thus, arrestin-3 regulates the activity of multiple JNK isoforms, suggesting that it might play a role in survival and apoptosis of all cell types.

Biomolecular scaffolds for enhanced signaling and catalytic efficiency

Proteins inherently are not designed to be standalone entities. Whether it is a multi-step biochemical reaction or a signaling event that triggers several other cascading events, proteins are naturally designed to function cohesively. Several natural systems have been developed through evolution to co-localize the functional proteins of the same pathway in order to ensure efficient communication of signals or intermediates. This review focuses on some selected examples of where synthetic scaffolds inspired by nature have been used to enhance the overall biological pathway performance. Applications encompass both in vivo and in vitro systems that address two key biological events in cell signaling and biosynthesis will be discussed.

Characterization of Golgi scaffold proteins and their roles in compartmentalizing cell signaling

Subcellular compartmentalization has become an important theme in cell signaling. In particular, the Golgi apparatus (GA) plays a prominent role in compartmentalizing signaling cascades that originate at the plasma membrane or other organelles. To precisely regulate this process, cells have evolved a unique class of organizer proteins, termed "scaffold proteins". Sef, PAQR3, PAQR10 and PAQR11 are scaffold proteins that have recently been identified on the GA and are referred to as Golgi scaffolds. The major cell growth signaling pathways, such as Ras/MAPK, PI3K/AKT, insulin and VEGF (vascular endothelial growth factor), are tightly regulated spatially and temporally by these Golgi scaffolds to ensure a physiologically appropriate outcome. Here, we discuss the subcellular localization and characterization of the topology and functional domains of these Golgi scaffolds and summarize their roles in the compartmentalization of cell signaling. We also highlight the physiological and pathological roles of these Golgi scaffolds in tumorigenesis and developmental disorders.

Molecular basis of MAP kinase regulation

Mitogen-activated protein kinases (MAPKs; ERK1/2, p38, JNK, and ERK5) have evolved to transduce environmental and developmental signals (growth factors, stress) into adaptive and programmed responses (differentiation, inflammation, apoptosis). Almost 20 years ago, it was discovered that MAPKs contain a docking site in the C-terminal lobe that binds a conserved 13-16 amino acid sequence known as the D- or KIM-motif (kinase interaction motif). Recent crystal structures of MAPK:KIM-peptide complexes are leading to a precise understanding of how KIM sequences contribute to MAPK selectivity. In addition, new crystal and especially NMR studies are revealing how residues outside the canonical KIM motif interact with specific MAPKs and contribute further to MAPK selectivity and signaling pathway fidelity. In this review, we focus on these recent studies, with an emphasis on the use of NMR spectroscopy, isothermal titration calorimetry and small angle X-ray scattering to investigate these processes.

Effects of valproate sodium on extracellular signal-regulated kinase 1/2 phosphorylation following hippocampal neuronal epileptiform discharge in rats

The aim of the present study was to investigate the effects of valproate sodium (VPAS) on the phosphorylation extracellular signal-regulated kinase 1/2 (ERK1/2) following hippocampal neuronal epileptiform discharge in rat neurons. The study used neurons from female and male neonate Sprague-Dawley (SD) rats (at least 24 h old), which were rapidly decapitated. Following the successful development of the epileptiform discharge cell model, the neurons were divided into two groups, the VPAS group and the control group. In the concentration-response experiment, the neurons were incubated with three different concentrations of VPAS (50, 75 and 100 mg/l) 30 min prior to the epileptiform discharge. The expression of phosphorylated ERK1/2 (p-ERK1/2) was examined using an immunofluorescence technique. In the time-response experiment, the neurons were incubated with VPAS (50 mg/l) and monitored at different time-points (30 min prior to the epileptiform discharge and 0 min, 30 min, 2 h and 6 h subsequent to epileptiform discharge), and western blotting was employed to measure the changes in p-ERK1/2 protein expression. No significant differences in the expression of p-ERK1/2 among the neurons treated with different concentrations of VPAS were identified in the concentration-response experiment. However, in the time-response experiment, the expression of p-ERK1/2 30 min prior to the epileptiform discharge was significantly lower compared with that at the other time-points. Furthermore, 50 mg/l VPAS was capable of decreasing the action potential frequency of the neuronal epileptiform discharge. ERK1/2 was excessively and persistently activated following the epileptiform discharge of the neurons. In addition, a low concentration of VPAS was effective at inhibiting the phosphorylation of ERK1/2 at an earlier period of neuronal epileptiform discharge.