Cloning and characterization of MEK6, a novel member of the mitogen-activated protein kinase kinase cascade

Molecular targets for management of diabetes: Remodelling of white adipose to brown adipose tissue

Diabetes mellitus is a disorder characterised metabolic dysfunction that results in elevated glucose level in the bloodstream. Diabetes is of two types, type1 and type 2 diabetes. Obesity is considered as one of the major reasons intended for incidence of diabetes hence it turns out to be essential to study about the adipose tissue which is responsible for fat storage in body. Adipose tissues play significant role in maintaining the balance between energy stabilization and homeostasis. The three forms of adipose tissue are - White adipose tissue (WAT), Brown adipose tissue (BAT) and Beige adipose tissue (intermediate form). The amount of BAT gets reduced, and WAT starts to increase with the age. WAT when exposed to certain stimuli gets converted to BAT by the help of certain transcriptional regulators. The browning of WAT has been a matter of study to treat the metabolic disorders and to initiate the expenditure of energy. The three main regulators responsible for the browning of WAT are PRDM16, PPARγ and PGC-1α via various cellular and molecular mechanism. Presented review article includes the detailed elaborative aspect of genes and proteins involved in conversion of WAT to BAT.

1,3-Dichloroadamantyl-Containing Ureas as Potential Triple Inhibitors of Soluble Epoxide Hydrolase, p38 MAPK and c-Raf

Soluble epoxide hydrolase (sEH) is an enzyme involved in the metabolism of bioactive lipid signaling molecules. sEH converts epoxyeicosatrienoic acids (EET) to virtually inactive dihydroxyeicosatrienoic acids (DHET). The first acids are "medicinal" molecules, the second increase the inflammatory infiltration of cells. Mitogen-activated protein kinases (p38 MAPKs) are key protein kinases involved in the production of inflammatory mediators, including tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2). p38 MAPK signaling plays an important role in the regulation of cellular processes, especially inflammation. The proto-oncogenic serine/threonine protein kinase Raf (c-Raf) is a major component of the mitogen-activated protein kinase (MAPK) pathway: ERK1/2 signaling. Normal cellular Raf genes can also mutate and become oncogenes, overloading the activity of MEK1/2 and ERK1/2. The development of multitarget inhibitors is a promising strategy for the treatment of socially dangerous diseases. We synthesized 1,3-disubstituted ureas and diureas containing a dichloroadamantyl moiety. The results of computational methods show that soluble epoxide hydrolase inhibitors can act on two more targets in different signaling pathways of mitogen-activated protein kinases p38 MAPK and c-Raf. The two chlorine atoms in the adamantyl moiety may provide additional Cl-π interactions in the active site of human sEH. Molecular dynamics studies have shown that the stability of ligand-protein complexes largely depends on the "spacer effect." The compound containing a bridge between the chloroadamantyl fragment and the ureide group forms more stable ligand-protein complexes with sEH and p38 MAPK, which indicates a better conformational ability of the molecule in the active sites of these targets. In turn, a compound containing two chlorine atoms forms a more stable complex with c-Raf, probably due to the presence of additional halogen bonds of chlorine atoms with amino acid residues.

Functional analysis of two mitogen-activated protein kinases involved in thermal resistance of the predatory mite Neoseiulus californicus (Acari: Phytoseiidae)

Predatory mites are important biological control agents used against phytophagous mites and small insects. They face various environmental pressures, especially fluctuating climate factors. Neoseiulus californicus, a commercially available phytoseiid mite, is adapted to a wide range of temperature conditions. We investigated the regulatory mechanisms governing the plastic response of N. californicus for coping with environmental temperature variations. The mitogen-activated protein kinase (MAPK) signaling pathway is a highly conserved pathway of cell signal transduction that responds to environmental stress. We isolated two MAPKK genes (NcMAPKK4 and NcMAPKK6) from N. californicus and studied their functions. Developmental stage-specific expression level analysis showed that in adults, particularly females, NcMAPKK4 and NcMAPKK6 levels were higher than in other developmental stages. The expression level analysis at extremely high and low temperature conditions demonstrated that NcMAPKK4 could be induced significantly by adverse thermal stresses, whereas NcMAPKK6 distinctly responded to heat shock, indicating their different roles in thermal stress responses. After silencing of NcMAPKK4, both heat and cold resistance decreased significantly, whereas NcMAPKK6 knockdown had a greater influence on heat resistance. Knockdown of NcMAPKKs also reduced the activities of antioxidant enzymes, suggesting the regulation of NcMAPKKs was closely related to the antioxidant process in oxidative stress caused by external stimuli. These results indicate an important role of NcMAPKKs in the response to thermal stress and provide insight into the MAPK cascade pathway in the environmental adaptation mechanisms of phytoseiid mites.

Regulation of the p38-MAPK pathway by hyperosmolarity and by WNK kinases

p38-MAPK is a stress-response kinase activated by hyperosmolarity. Here we interrogated the pathways involved. We show that p38-MAPK signaling is activated by hyperosmotic stimulation in various solutions, cell types and colonic organoids. Hyperosmolarity sensing is detected at the level of the upstream activators of p38-MAPK: TRAF2/ASK1 (but not Rac1) and MKK3/6/4. While WNK kinases are known osmo-sensors, we found, unexpectedly, that short (2 h) inhibition of WNKs (with WNK463) led to elevated p38-MAPK activity under hyperosmolarity, which was mediated by WNK463-dependent stimulation of TAK1 or TRAF2/ASK1, the upstream activators of MKK3/6/4. However, this effect was temporary and was reversed by long-term (2 days) incubation with WNK463. Accordingly, 2 days (but not 2 h) inhibition of p38-MAPK or its upstream activators ASK1 or TAK1, or WNKs, diminished regulatory volume increase (RVI) following cell shrinkage under hyperosmolarity. We also show that RVI mediated by the ion transporter NKCC1 is dependent on p38-MAPK. Since WNKs are known activators of NKCC1, we propose a WNK- > NKCC1- > p38-MAPK pathway that controls RVI. This pathway is augmented by NHE1. Additionally, hyperosmolarity inhibited mTORC1 activation and cell proliferation. Thus, activation of p38-MAPK and WNKs is important for RVI and for cell proliferation.

MAP2K6 remodels chromatin and facilitates reprogramming by activating Gatad2b-phosphorylation dependent heterochromatin loosening

Somatic cell reprogramming is an ideal model for studying epigenetic regulation as it undergoes dramatic chromatin remodeling. However, a role for phosphorylation signaling in chromatin protein modifications for reprogramming remains unclear. Here, we identified mitogen-activated protein kinase kinase 6 (Mkk6) as a chromatin relaxer and found that it could significantly enhance reprogramming. The function of Mkk6 in heterochromatin loosening and reprogramming requires its kinase activity but does not depend on its best-known target, P38. We identified Gatad2b as a novel target of Mkk6 phosphorylation that acts downstream to elevate histone acetylation levels and loosen heterochromatin. As a result, Mkk6 over-expression facilitates binding of Sox2 and Klf4 to their targets and promotes pluripotency gene expression during reprogramming. Our studies not only reveal an Mkk phosphorylation mediated modulation of chromatin status in reprogramming, but also provide new rationales to further investigate and improve the cell fate determination processes.

Thermal Bioprinting Causes Ample Alterations of Expression of LUCAT1, IL6, CCL26, and NRN1L Genes and Massive Phosphorylation of Critical Oncogenic Drug Resistance Pathways in Breast Cancer Cells

Bioprinting technology merges engineering and biological fields and together, they possess a great translational potential, which can tremendously impact the future of regenerative medicine and drug discovery. However, the molecular effects elicited by thermal inkjet bioprinting in breast cancer cells remains elusive. Previous studies have suggested that bioprinting can be used to model tissues for drug discovery and pharmacology. We report viability, apoptosis, phosphorylation, and RNA sequence analysis of bioprinted MCF7 breast cancer cells at separate timepoints post-bioprinting. An Annexin A5-FITC apoptosis stain was used in combination with flow cytometry at 2 and 24 h post-bioprinting. Antibody arrays using a Human phospho-MAPK array kit was performed 24 h post-bioprinting. RNA sequence analysis was conducted in samples collected at 2, 7, and 24 h post-bioprinting. The post-bioprinting cell viability averages were 77 and 76% at 24 h and 48 h, with 31 and 64% apoptotic cells at 2 and 24 h after bioprinting. A total of 21 kinases were phosphorylated in the bioprinted cells and 9 were phosphorylated in the manually seeded controls. The RNA seq analysis in the bioprinted cells identified a total of 12,235 genes, of which 9.7% were significantly differentially expressed. Using a ±2-fold change as the cutoff, 266 upregulated and 206 downregulated genes were observed in the bioprinted cells, with the following 5 genes uniquely expressed NRN1L, LUCAT1, IL6, CCL26, and LOC401585. This suggests that thermal inkjet bioprinting is stimulating large scale gene alterations that could potentially be utilized for drug discovery. Moreover, bioprinting activates key pathways implicated in drug resistance, cell motility, proliferation, survival, and differentiation.

A novel MKK gene (EcMKK6) in Epinephelus coioides: Identification, characterization and its response to Vibrio alginolyticus and SGIV infection

Mitogen-activated protein kinase 6 (MKK6) is one of the major important central regulatory proteins response to environmental and physiological stimuli. In this study, a novel MKK6, EcMKK6, was isolated from Epinephelus coioides, an economically important cultured fish in China and Southeast Asian counties. The open reading frame (ORF) of EcMKK6 is 1077 bp encoding 358 amino acids. EcMKK6 contains a serine/threonine protein kinase (S_TKc) domain, a tyrosine kinase catalytic domain, a conserved dual phosphorylation site in the SVAKT motif and a conserved DVD domain. By in situ hybridization (ISH) with Digoxigenin-labeled probe, EcMKK6 mainly located at the cytoplasm of cells, and a little appears in the nucleus. EcMKK6 mRNA can be detected in all eleven tissues examined, but the expression level is different in these tissues. After challenge with Vibrio alginolyticus and Singapore grouper iridovirus (SGIV), the transcription level of EcMKK6 was apparently up-regulated in the tissues examined. The data demonstrated that the sequence and the characters of EcMKK6 were conserved, EcMKK6 showed tissue-specific expression profiles in healthy grouper, and the expression was significantly varied after pathogen infection, indicating that EcMKK6 may play important roles in E. coioides during pathogen-caused inflammation.

Linear Energy Transfer Modulates Radiation-Induced NF-kappa B Activation and Expression of its Downstream Target Genes

Nuclear factor kappaB (NF-κB) is a central transcription factor in the immune system and modulates cell survival in response to radiotherapy. Activation of NF-κB was shown to be an early step in the cellular response to ultraviolet A (UVA) and ionizing radiation exposure in human cells. NF-κB activation by the genotoxic stress-dependent sub-pathway after exposure to different radiation qualities had been evaluated to a very limited extent. In addition, the resulting gene expression profile, which shapes the cellular and tissue response, is unknown. Therefore, in this study the activation of NF-κB after exposure to low- and high-linear energy transfer (LET) radiation and the expression of its target genes were analyzed in human embryonic kidney (HEK) cells. The activation of NF-κB via canonical and genotoxic stress-induced pathways was visualized by the cell line HEK-pNF-κB-d2EGFP/Neo L2 carrying the destabilized enhanced green fluorescent protein (d2EGFP) as reporter. The NF-κB-dependent d2EGFP expression after irradiation with X rays and heavy ions was evaluated by flow cytometry. Because of differences in the extent of NF-κB activation after irradiation with X rays (significant NF-κB activation for doses >4 Gy) and heavy ions (significant NF-κB activation at doses as low as 1 Gy), it was expected that radiation quality (LET) played an important role in the cellular radiation response. In addition, the relative biological effectiveness (RBE) of NF-κB activation and reduction of cellular survival were compared for heavy ions having a broad LET range (∼0.3-9,674 keV/μm). Furthermore, the effect of LET on NF-κB target gene expression was analyzed by real-time reverse transcriptase quantitative PCR (RT-qPCR). The maximal RBE for NF-κB activation and cell killing occurred at an LET value of 80 and 175 keV/μm, respectively. There was a dose-dependent increase in expression of NF-κB target genes NF-κB1A and CXCL8. A qPCR array of 84 NF-κB target genes revealed that TNF and a set of CXCL genes (CXCL1, CXCL2, CXCL8, CXCL10), CCL2, VCAM1, CD83, NF-κB1, NF-κB2 and NF-κBIA were strongly upregulated after exposure to X rays and neon ions (LET 92 keV/μm). After heavy-ion irradiations, it was noted that the expression of NF-κB target genes such as chemokines and CD83 was highest at an LET value that coincided with the LET resulting in maximal NF-κB activation, whereas expression of the NF-κB inhibitory gene NFKBIA was induced transiently by all radiation qualities investigated. Taken together, these findings clearly demonstrate that NF-κB activation and NF-κB-dependent gene expression by heavy ions are highest in the LET range of ∼50-200 keV/μm. The upregulated chemokines and cytokines (CXCL1, CXCL2, CXCL10, CXCL8/IL-8 and TNF) could be important for cell-cell communication among hit as well as nonhit cells (bystander effect).

P38 activation induces the dissociation of tristetraprolin from Argonaute 2 to increase ARE-mRNA stabilization

ARE-mRNAs are actively degraded with tristetraprolin (TTP) in resting cells while they turn into stable messengers in activated cells. P38 plays a crucial role in stabilizing ARE-mRNA. Here we reveal that P38 activation represses the interaction between TTP and Ago2, thus restraining TTP from being targeted into processing bodies and stabilizing ARE-mRNA.

A genetic variation associated with plasma erythropoietin and a non-coding transcript of PRKAR1A in sickle cell disease

Blood erythropoietin (EPO) increases primarily to hypoxia. In sickle cell anaemia (homozygous HBBE6V; HbSS), plasma EPO is elevated due to hemolytic anaemia-related hypoxia. Hydroxyurea treatment reduces haemolysis and anaemia by increasing foetal haemoglobin, which leads to lower hypoxic transcriptional responses in blood mononuclear cells but paradoxically further increases EPO. To investigate this apparent hypoxia-independent EPO regulation, we assessed two sickle cell disease (SCD) cohorts for genetic associations with plasma EPO, by prioritizing 237,079 quantitative trait loci for expression level and/or transcript isoform variations of 12,727 genes derived from SCD blood mononuclear cells. We found an association between the T allele of SNP rs60684937 and increased plasma EPO (n = 567, combined P = 5.5 × 10 − 8 adjusted for haemoglobin and hydroxyurea) and validated it in independent SCD patients (n = 183, P = 0.018). The T allele of rs60684937 was associated with a relatively increased expression of a non-coding transcript of PRKAR1A (cAMP-dependent protein kinase type I-alpha regulatory subunit) in 58 SCD patients (P = 7.9 × 10 − 7) and 58 HapMap Yoruba samples (P = 0.0011). In conclusion, we demonstrate that plasma EPO elevation with hydroxyurea in SCD is independent of hypoxic responses and that genetic variation at SNP rs60684937 may contribute to EPO regulation through a cAMP-dependent protein kinase A pathway.

Knockdown of L1CAM significantly reduces metastasis in a xenograft model of human melanoma: L1CAM is a potential target for anti-melanoma therapy

Finding additional functional targets for combination therapy could improve the outcome for melanoma patients. In a spontaneous metastasis xenograft model of human melanoma a shRNA mediated knockdown of L1CAM more than sevenfold reduced the number of lung metastases after the induction of subcutaneous tumors for two human melanoma cell lines (MeWo, MV3). Whole genome expression arrays of the initially L1CAM high MeWo subcutaneous tumors revealed unchanged or downregulated genes involved in epithelial to mesenchymal transition (EMT) except an upregulation of Jagged 1, indicating a compensatory change in Notch signaling especially as Jagged 1 expression showed an increase in MeWo L1CAM metastases and Jagged 1 was expressed in metastases of the initially L1CAM low MV3 cells as well. Expression of 17 genes showed concordant regulation for L1CAM knockdown tumors of both cell lines. The changes in gene expression indicated changes in the EMT network of the melanoma cells and an increase in p53/p21 and p38 activity contributing to the reduced metastatic potential of the L1CAM knockdowns. Taken together, these data make L1CAM a highly interesting therapeutic target to prevent further metastatic spread in melanoma patients.

p38 (Mapk14/11) occupies a regulatory node governing entry into primitive endoderm differentiation during preimplantation mouse embryo development

During mouse preimplantation embryo development, the classically described second cell-fate decision involves the specification and segregation, in blastocyst inner cell mass (ICM), of primitive endoderm (PrE) from pluripotent epiblast (EPI). The active role of fibroblast growth factor (Fgf) signalling during PrE differentiation, particularly in the context of Erk1/2 pathway activation, is well described. However, we report that p38 family mitogen-activated protein kinases (namely p38α/Mapk14 and p38β/Mapk11; referred to as p38-Mapk14/11) also participate in PrE formation. Specifically, functional p38-Mapk14/11 are required, during early-blastocyst maturation, to assist uncommitted ICM cells, expressing both EPI and earlier PrE markers, to fully commit to PrE differentiation. Moreover, functional activation of p38-Mapk14/11 is, as reported for Erk1/2, under the control of Fgf-receptor signalling, plus active Tak1 kinase (involved in non-canonical bone morphogenetic protein (Bmp)-receptor-mediated PrE differentiation). However, we demonstrate that the critical window of p38-Mapk14/11 activation precedes the E3.75 timepoint (defined by the initiation of the classical ‘salt and pepper’ expression pattern of mutually exclusive EPI and PrE markers), whereas appropriate lineage maturation is still achievable when Erk1/2 activity (via Mek1/2 inhibition) is limited to a period after E3.75. We propose that active p38-Mapk14/11 act as enablers, and Erk1/2 as drivers, of PrE differentiation during ICM lineage specification and segregation.

SB203580 Modulates p38 MAPK Signaling and Dengue Virus-Induced Liver Injury by Reducing MAPKAPK2, HSP27, and ATF2 Phosphorylation

Dengue virus (DENV) infection causes organ injuries, and the liver is one of the most important sites of DENV infection, where viral replication generates a high viral load. The molecular mechanism of DENV-induced liver injury is still under investigation. The mitogen activated protein kinases (MAPKs), including p38 MAPK, have roles in the hepatic cell apoptosis induced by DENV. However, the in vivo role of p38 MAPK in DENV-induced liver injury is not fully understood. In this study, we investigated the role of SB203580, a p38 MAPK inhibitor, in a mouse model of DENV infection. Both the hematological parameters, leucopenia and thrombocytopenia, were improved by SB203580 treatment and liver transaminases and histopathology were also improved. We used a real-time PCR microarray to profile the expression of apoptosis-related genes. Tumor necrosis factor α, caspase 9, caspase 8, and caspase 3 proteins were significantly lower in the SB203580-treated DENV-infected mice than that in the infected control mice. Increased expressions of cytokines including TNF-α, IL-6 and IL-10, and chemokines including RANTES and IP-10 in DENV infection were reduced by SB203580 treatment. DENV infection induced the phosphorylation of p38MAPK, and its downstream signals including MAPKAPK2, HSP27 and ATF-2. SB203580 treatment did not decrease the phosphorylation of p38 MAPK, but it significantly reduced the phosphorylation of MAPKAPK2, HSP27, and ATF2. Therefore, SB203580 modulates the downstream signals to p38 MAPK and reduces DENV-induced liver injury.

The contribution of CMP kinase to the efficiency of DNA repair

Cellular supply of deoxynucleoside triphosphates (dNTPs) is crucial for DNA replication and repair. In this study, we investigated the role of CMP/UMP kinase (CMPK), an enzyme catalyzes CDP formation, in DNA repair. Knockdown of CMPK delays DNA repair during recovery from UV damage in serum-deprived cells but not in the cells without serum deprivation. Exogenous supply of cytidine or deoxycytidine facilitates DNA repair dependent on CMPK in serum-deprived cells, suggesting that the synthesis of dCDP or CDP determines the rate of repair. However, CMPK knockdown does not affect the steady state level of dCTP in serum-deprived cells. We then found the localization of CMPK at DNA damage sites and its complex formation with Tip60 and ribonucleotide reductase. Our analysis demonstrated that the N-terminal 32-amino-acid of CMPK is required for its recruitment to DNA damage sites in a Tip60-dependent manner. Re-expression of wild-type but not N-terminus deleted CMPK restores the efficiency of DNA repair in CMPK knockdown cells. We proposed that site-specific dCDP formation via CMPK provides a means to facilitate DNA repair in serum-deprived cells.

Photo-electrochemical Bioanalysis of Guanosine Monophosphate Using Coupled Enzymatic Reactions at a CdS/ZnS Quantum Dot Electrode

A photo-electrochemical sensor for the specific detection of guanosine monophosphate (GMP) is demonstrated, based on three enzymes combined in a coupled reaction assay. The first reaction involves the adenosine triphosphate (ATP)-dependent conversion of GMP to guanosine diphosphate (GDP) by guanylate kinase, which warrants substrate specificity. The reaction products ADP and GDPare co-substrates for the enzymatic conversion of phosphoenolpyruvate to pyruvate in a second reaction mediated by pyruvate kinase. Pyruvate in turn is the co-substrate for lactate dehydrogenase that generates lactate via oxidation of nicotinamide adenine dinucleotide (reduced form) NADH to NAD(+). This third enzymatic reaction is electrochemically detected. For this purpose a CdS/ZnS quantum dot (QD) electrode is illuminated and the photocurrent response under fixed potential conditions is evaluated. The sequential enzyme reactions are first evaluated in solution. Subsequently, a sensor for GMP is constructed using polyelectrolytes for enzyme immobilization.

Insights into open/closed conformations of the catalytically active human guanylate kinase as investigated by small-angle X-ray scattering

Abstract

Bio-catalysis is the outcome of a subtle interplay between internal motions in enzymes and chemical kinetics. Small-angle X-ray scattering (SAXS) investigation of an enzyme’s internal motions during catalysis offers an integral view of the protein’s structural plasticity, dynamics, and function, which is useful for understanding allosteric effects and developing novel medicines. Guanylate kinase (GMPK) is an essential enzyme involved in the guanine nucleotide metabolism of unicellular and multicellular organisms. It is also required for the intracellular activation of numerous antiviral and anticancer purine nucleoside analog prodrugs. Catalytically active recombinant human GMPK (hGMPK) was purified for the first time and changes in the size and shape of open/closed hGMPK were tracked by SAXS. The binding of substrates (GMP + AMPPNP or Ap5G or GMP + ADP) resulted in the compaction of size and shape of hGMPK. The structural changes between open and completely closed hGMPK conformation were confirmed by observing differences in the hGMPK secondary structures with circular dichroism spectroscopy.

Graphical abstract

Electronic supplementary material

The online version of this article (doi:10.1007/s00249-015-1079-9) contains supplementary material, which is available to authorized users.

Expression patterns of immune-associated genes in external genital and perianal warts treated with sinecatechins

The role of human papillomavirus (HPV) in human disease includes external genital and perianal warts (EGW), with some HPV genotypes having oncogenic potential (i.e., HPV-16 and -18). While green-tea extracts have antitumor and antiproliferative effects in vitro, the mechanism of action of sinecatechins in the treatment of EGW is not well understood. To investigate the role of immune-regulated genes further, an open-label, single institution, prospective study was conducted enrolling patients with clinically diagnosed EGW. Thirty subjects were enrolled, and 18 completed the trial. All patients applied sinecatechins 15% ointment to target lesions in the study. RNA expression microarrays were obtained from treated EGW lesions and analyzed for differential gene expression of immune-regulated genes. HPV types were analyzed and, based on copy number, were stratified into virological responders (VR) or nonresponders (VNR). Gene expression analysis of RNA samples was performed using TaqMan arrays for human T cell receptor and CD3 complex (TCR), Toll-like receptors (TLR) pathway, interferon (IFN) pathway, and antigen processing pathway. A total of 256 genes were analyzed across the four arrays. Genes that were significantly regulated between VRs and VNRs were CREB3L4, HIST1H3A, HIST1H3H, IFNA1, IFNA4, IFNA5, IFNA6, IFNA8, IFNA14, IFNG, IFNAR1, IL6, IRF9, MAPK4, MAPK5, MAPK14, NET1, and PIK3C2A in the IFN array. In the TCR array, HLA_B was found to be statistically significantly upregulated in both the VR and VNR groups; concomitantly, CD8A was found to be statistically significantly downregulated only in VRs. In the TLR array, only LBP and MAPK8 were found to be differentially regulated. In the antigen processing array, HLA-A, HLA-C, HLA-DMA, HLA-DMB, HLA-F, PSMA5, PSMB8, and PSMB9 were differentially downregulated. Based on these findings, it was determined that sinecatechins treatment modulates and downregulates genes involved in the pro-inflammatory response to HPV infection.

MKK6 is upregulated in human esophageal, stomach, and colon cancers

Expression analysis of MKK6 protein in solid tumors has never been investigated. Here, we report systematic analysis of MKK6 protein in different types of human tumor samples using western blotting and immunofluorescence techniques. We observed significant increase in the expression of MKK6 in Esophageal, Stomach, and Colon cancers as compared to controls. Results were alternately confirmed by Immunofluorescence studies. Upregulation of MKK6 protein is indicative of its role in human cancers and could possibly be used as a novel diagnostic or prognostic marker in these cancers.

Role of p38 MAP Kinase Signal Transduction in Solid Tumors

Mitogen-activated protein kinases (MAPKs) mediate a wide variety of cellular behaviors in response to extracellular stimuli. One of the main subgroups, the p38 MAP kinases, has been implicated in a wide range of complex biologic processes, such as cell proliferation, cell differentiation, cell death, cell migration, and invasion. Dysregulation of p38 MAPK levels in patients are associated with advanced stages and short survival in cancer patients (e.g., prostate, breast, bladder, liver, and lung cancer). p38 MAPK plays a dual role as a regulator of cell death, and it can either mediate cell survival or cell death depending not only on the type of stimulus but also in a cell type specific manner. In addition to modulating cell survival, an essential role of p38 MAPK in modulation of cell migration and invasion offers a distinct opportunity to target this pathway with respect to tumor metastasis. The specific function of p38 MAPK appears to depend not only on the cell type but also on the stimuli and/or the isoform that is activated. p38 MAPK signaling pathway is activated in response to diverse stimuli and mediates its function by components downstream of p38. Extrapolation of the knowledge gained from laboratory findings is essential to address the clinical significance of p38 MAPK signaling pathways. The goal of this review is to provide an overview on recent progress made in defining the functions of p38 MAPK pathways with respect to solid tumor biology and generate testable hypothesis with respect to the role of p38 MAPK as an attractive target for intervention of solid tumors.

Roles of MAPKAPK-2 and HSP27 in the reduction of renal ischemia-reperfusion injury by ischemic postconditioning in rats

PURPOSE

Ischemic postconditioning is a procedure during which intermittent reperfusions are performed in the early phase of reperfusion to protect organs from ischemia/reperfusion injury. And in this study, we mainly investigated the injury-alleviative role of mitogen-activated protein kinase-activating protein kinase-2 (MAPKAPK-2) and heat shock protein 27 (HSP27) in renal ischemic reperfusion injury during the procedure of ischemic postconditioning.

METHODS

Sprague-Dawley rats were randomly divided into four groups. The injury models were prepared by clipping the left renal pedicle of rats after ligating the right renal pedicle for 60 min. In the ischemic postconditioning group, sequential reperfusions were done for 10 s and another ischemia for 10 s for six cycles after kidney ischemia for 60 min. In addition, the specific inhibitor SB203580 was injected through caudal vein before ischemia. Serum creatinine, blood urea nitrogen and the expression of HSP27 and MAPKAPK-2 were detected 1, 3, 6 and 24 h later after reperfusion. Furthermore, phosphorylation of HSP27 and MAPKAPK-2 protein contents, histological changes and apoptosis were compared 24 h later after reperfusion.

RESULTS

Our data showed that ischemic postconditioning attenuated the renal dysfunction and cell apoptosis induced by I/R and increased phosphorylation of MAPKAPK-2 and HSP27. The results indicated that ischemic postconditioning decreased apoptosis and improved renal function.

CONCLUSIONS

Taken together, it is suggested that the renal protective effect may be related to the levels of HSP27 and MAPKAPK-2 activation.

Regulation of Hsf4b nuclear translocation and transcription activity by phosphorylation at threonine 472

Hsf4b, a key regulator of postnatal lens development, is subjected to posttranslational modifications including phosphorylation. However, the phosphorylation sites in Hsf4b and their biological effects on the transcription activity of Hsf4b are poorly understood. Here we examined 17 potential phosphorylation residues in Hsf4b with alanine-scanning assays and found that a T472A mutation diminished Hsf4b-mediated expression of Hsp25 and alphaB-crystallin. In contrast, the phosphomimetic mutation of T472D enhanced their expression. Further investigation demonstrated that Hsf4b could interact with nuclear-transporter importin beta-1 and Hsc70 via amino acids 246-320 and 320-493, respectively. T472A mutation reduced Hsf4bs interaction with importin beta-1, while enhancing its interaction with Hsc7O, resulting in Hsf4b cytosolic re-localization, protein instability and transcription activity attenuation. At the upstream, MEK6 was found to interact with Hsf4b and enhance Hsf4b's nuclear translocation and transcription activity, probably by phosphorylation at sites such as T472. Taken together, our results suggest that phosphotylation of Hsf4b at T472 by protein kinases such as MEI(6 regulates Hsf4b interaction with the importin V I -Hsc7O complex, resulting in blockade of its nuclear translocation and transcriptional activity of Hsf4b.

β-Amyloid-evoked apoptotic cell death is mediated through MKK6-p66shc pathway

We have previously shown the involvement of p66shc in mediating apoptosis. Here, we demonstrate the novel mechanism of β-Amyloid-induced toxicity in the mammalian cells. β-Amyloid leads to the phosphorylation of p66shc at the serine 36 residue and activates MKK6, by mediating the phosphorylation at serine 207 residue. Treatment of cells with antioxidants blocks β-Amyloid-induced serine phosphorylation of MKK6, reactive oxygen species (ROS) generation, and hence protected cells against β-Amyloid-induced cell death. Our results indicate that serine phosphorylation of p66shc is carried out by active MKK6. MKK6 knock-down resulted in decreased serine 36 phosphorylation of p66shc. Co-immunoprecipitation results demonstrate a direct physical association between p66shc and WT MKK6, but not with its mutants. Increase in β-Amyloid-induced ROS production was observed in the presence of MKK6 and p66shc, when compared to triple mutant of MKK6 (inactive) and S36 mutant of p66shc. ROS scavengers and knock-down against p66shc, and MKK6 significantly decreased the endogenous level of active p66shc, ROS production, and cell death. Finally, we show that the MKK6-p66shc complex mediates β-Amyloid-evoked apoptotic cell death.

MEK and the inhibitors: from bench to bedside

Four distinct MAP kinase signaling pathways involving 7 MEK enzymes have been identified. MEK1 and MEK2 are the prototype members of MEK family proteins. Several MEK inhibitors are in clinical trials. Trametinib is being evaluated by FDA for the treatment of metastatic melanoma with BRAF V600 mutation. Selumetinib has been studied in combination with docetaxel in phase II randomized trial in previously treated patients with advanced lung cancer. Selumetinib group had better response rate and progression-free survival. This review also summarized new MEK inhibitors in clinical development, including pimasertib, refametinib, PD-0325901, TAK733, MEK162 (ARRY 438162), RO5126766, WX-554, RO4987655 (CH4987655), GDC-0973 (XL518), and AZD8330.

Activation and function of the MAPKs and their substrates, the MAPK-activated protein kinases

The mitogen-activated protein kinases (MAPKs) regulate diverse cellular programs by relaying extracellular signals to intracellular responses. In mammals, there are more than a dozen MAPK enzymes that coordinately regulate cell proliferation, differentiation, motility, and survival. The best known are the conventional MAPKs, which include the extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun amino-terminal kinases 1 to 3 (JNK1 to -3), p38 (α, β, γ, and δ), and ERK5 families. There are additional, atypical MAPK enzymes, including ERK3/4, ERK7/8, and Nemo-like kinase (NLK), which have distinct regulation and functions. Together, the MAPKs regulate a large number of substrates, including members of a family of protein Ser/Thr kinases termed MAPK-activated protein kinases (MAPKAPKs). The MAPKAPKs are related enzymes that respond to extracellular stimulation through direct MAPK-dependent activation loop phosphorylation and kinase activation. There are five MAPKAPK subfamilies: the p90 ribosomal S6 kinase (RSK), the mitogen- and stress-activated kinase (MSK), the MAPK-interacting kinase (MNK), the MAPK-activated protein kinase 2/3 (MK2/3), and MK5 (also known as p38-regulated/activated protein kinase [PRAK]). These enzymes have diverse biological functions, including regulation of nucleosome and gene expression, mRNA stability and translation, and cell proliferation and survival. Here we review the mechanisms of MAPKAPK activation by the different MAPKs and discuss their physiological roles based on established substrates and recent discoveries.

Activation and Function of the MAPKs and Their Substrates, the MAPK-Activated Protein Kinases

The mitogen-activated protein kinases (MAPKs) regulate diverse cellular programs by relaying extracellular signals to intracellular responses. In mammals, there are more than a dozen MAPK enzymes that coordinately regulate cell proliferation, differentiation, motility, and survival. The best known are the conventional MAPKs, which include the extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun amino-terminal kinases 1 to 3 (JNK1 to -3), p38 (α, β, γ, and δ), and ERK5 families. There are additional, atypical MAPK enzymes, including ERK3/4, ERK7/8, and Nemo-like kinase (NLK), which have distinct regulation and functions. Together, the MAPKs regulate a large number of substrates, including members of a family of protein Ser/Thr kinases termed MAPK-activated protein kinases (MAPKAPKs). The MAPKAPKs are related enzymes that respond to extracellular stimulation through direct MAPK-dependent activation loop phosphorylation and kinase activation. There are five MAPKAPK subfamilies: the p90 ribosomal S6 kinase (RSK), the mitogen- and stress-activated kinase (MSK), the MAPK-interacting kinase (MNK), the MAPK-activated protein kinase 2/3 (MK2/3), and MK5 (also known as p38-regulated/activated protein kinase [PRAK]). These enzymes have diverse biological functions, including regulation of nucleosome and gene expression, mRNA stability and translation, and cell proliferation and survival. Here we review the mechanisms of MAPKAPK activation by the different MAPKs and discuss their physiological roles based on established substrates and recent discoveries.

Modulation of protein kinase signaling cascades by palytoxin

Although known for its acutely toxic action, palytoxin has also been identified as a type of carcinogenic agent called a tumor promoter. In general tumor promoters do not damage DNA, but instead contribute to carcinogenesis by disrupting the regulation of cellular signaling. The identification of palytoxin as a tumor promoter, together with the recognition that the Na(+), K(+)-ATPase is its receptor, led to research on how palytoxin triggers the modulation of signal transduction pathways. This review focuses on mitogen activated protein (MAP) kinases as mediators of palytoxin-stimulated signaling. MAP kinases are a family of serine/threonine kinases that relay a variety of signals to the cellular machinery that regulates cell fate and function. The studies discussed in this review investigated how palytoxin stimulates MAP kinase activity and, in turn, how MAP kinases mediate the response of cells to palytoxin.

GluR6-containing KA receptor mediates the activation of p38 MAP kinase in rat hippocampal CA1 region during brain ischemia injury

Our previous study showed that kainate (KA) receptor subunit GluR6 played an important role in ischemia-induced MLK3 and JNK activation and neuronal degeneration through the GluR6-PSD95-MLK3 signaling module. However, whether the KA receptors subunit GluR6 is involved in the activation of p38 MAP kinase during the transient brain ischemia/reperfusion (I/R) in the rat hippocampal CA1 subfield is still unknown. In this present study, we first evaluated the time-course of phospho-p38 MAP kinase at various time-points after 15 min of ischemia and then observed the effects of antagonist of KA receptor subunit GluR6, GluR6 antisence oligodeoxynucleotides on the phosphorylation of p38 MAP kinase induced by I/R. Results showed that inhibiting KA receptor GluR6 or suppressing the expression of KA receptor GluR6 could down-regulate the elevation of phospho-p38 MAP kinase induced by I/R. These drugs also reduced the phosphorylation of MLK3, MKK3/MKK6, MKK4, and MAPKAPK2. Additionally, our results indicated administration of three drugs, including p38 MAP kinase inhibitor before brain ischemia significantly decreased the number of TUNEL-positive cells detected at 3 days of reperfusion and increased the number of the surviving CA1 pyramidal cells at 5 days of reperfusion after 15 min of ischemia. Taken together, we suggest that GluR6-contained KA receptors can mediate p38 MAP kinase activation through a kinase cascade, including MLK3, MKK3/MKK6, and MKK4 and then induce increased phosphorylation of MAPKAPK-2 during ischemia injury and ultimately result in neuronal cell death in the rat hippocampal CA1 region.

A global transcriptional view of apoptosis in human T-cell activation

Background

T-cell activation is an essential step of immune response. The process of proper T-cell activation is strictly monitored and regulated by apoptosis signaling. Yet, regulation of apoptosis, an integral and crucial facet during the process of T-cell activation, is not well understood.

Methods

In this study, a Gene-Ontology driven global gene expression analysis coupled with protein abundance and activity assays identified genes and pathways associated with regulation of apoptosis in primary human CD3+ T cells and separately CD4+ and CD8+ T cells.

Results

We identified significantly regulated apoptotic genes in several protein families, such as BCL2 proteins, CASPASE proteins, and TNF receptors, and detailed their transcriptional kinetics during the T-cell activation process. Transcriptional patterns of a few select genes (BCL2A1, BBC3 and CASP3) were validated at the protein level. Many of these apoptotic genes are involved in NF-κB signaling pathway, including TNFRSF10A, TNFRSF10B, TRAF4, TRAF1, TRAF3, and TRAF6. Upregulation of NF-κB and IκB family genes (REL, RELA, and RELB, NFKBIA, NFKBIE and NFKB1) at 48 to 96 hours, supported by the increase of phosphorylated RELA (p65), suggests that the involvement of the NF-κB complex in the process of T-cell proliferation is not only regulated at the protein level but also at the transcriptional level. Examination of genes involved in MAP kinase signalling pathway, important in apoptosis, suggests an induction of p38 and ERK1 cascades in T-cell proliferation (at 48 to 96 hours), which was explored using phosphorylation assays for p38 (MAPK14) and ERK1 (MAPK3). An immediate and short-lived increase of AP-1 activity measured by DNA-binding activity suggests a rapid and transient activation of p38 and/or JNK cascades upon T-cell activation.

Conclusion

This comparative genome-scale, transcriptional analysis of T-cell activation in the CD4+ and CD8+ subsets and the mixed CD3+ population identified many apoptosis genes not previously identified in the context of T-cell activation. Furthermore, it provided a comprehensive temporal analysis of the transcriptional program of apoptosis associated with T-cell activation.

Characterization of activation of MAP kinase superfamily in vasculature from diabetic rats

AIM

This study was investigated to characterize the activation mechanism of a mitogen-activated protein (MAP) kinase superfamily in diabetes in aortae and cultured vascular smooth muscle cells (VSMCs) from rats.

METHODS

Male Sprague-Dawley rats were used for this procedure, and diabetes was induced by streptozotocin injection at 50 mg/kg. After 6 weeks, the thoracic aortae from normal and diabetic rats were removed for detection of the MAP kinase superfamily by immunoblot analysis.

RESULTS

In aortae, the protein levels of extracellular signal-regulated protein kinase (ERK)-1, c-jun NH2-terminal protein kinase (JNK)-1 and -2, and p38 increased significantly more in diabetic rats than in normal rats. In contrast, phosphorylated protein levels of ERK-1 and -2, JNK-1, and p38 were significantly more elevated in diabetic rats than in normal rats. In VSMCs from normal rats, a high concentration of glucose cultured for three days significantly increased the phosphorylated protein levels of ERKs and p38, but not JNKs, without any change of these protein levels. Serum interleukin (IL)-1beta was significantly higher in diabetic rats than in normal rats. Several types of proinflammatory cytokine dose-dependently phosphorylated the levels of ERKs, JNK-1, and p38, but not JNK-2, in VSMCs from normal rats. In cells from diabetic rats, phosphorylated protein levels of ERKs and p38 were significantly elevated by IL-1beta. In addition, interferon-gamma phosphorylated the levels of ERKs in diabetic cells more than in normal cells.

CONCLUSION

Our results suggest that, under diabetic conditions, the MAP kinase superfamily was activated by different pathways in the vasculature; i.e., ERKs and p38 might be mainly phosphorylated by a complex of high concentrations of glucose and of several types of proinflammatory cytokines, but the phosphorylation of JNK-1 might depend on the concentration of proinflammatory cytokines such as IL-1beta, and/or additional unknown factors, except glucose.

p38 pathway kinases as anti-inflammatory drug targets

Mitogen-activated protein kinases (MAPK) are intracellular signaling molecules involved in cytokine synthesis. Several classes of mammalian MAPK have been identified, including extracellular signal-regulated kinase, c-jun N-terminal kinase, and p38 MAP kinase. p38alpha is a key MAPK involved in tumor necrosis factor alpha and other cytokine production, as well as enzyme induction (cyclooxygenase-2, inducible nitric oxide synthase, and matrix metalloproteinases) and adhesion molecule expression. An understanding of the broad biologic and pathophysiological roles of p38 MAPK family members has grown significantly over the past decade, as has the complexity of the signaling network leading to their activation. Downstream substrates of MAPK include other kinases (e.g., mitogen-activated protein-kinase-activated protein kinase 2) and factors that regulate transcription, nuclear export, and mRNA stability and translation. The high-resolution crystal structure of p38alpha has led to the design of selective inhibitors that have good pharmacological activity. Despite the strong rationale for MAPK inhibitors in human disease, direct proof of concept in the clinic has yet to be demonstrated, with most compounds demonstrating dose-limiting adverse effects. The role of MAPK in inflammation makes them attractive targets for new therapies, and efforts are continuing to identify newer, more selective inhibitors for inflammatory diseases.

Circadian phosphorylation of ATF-2, a potential activator of Period2 gene transcription in the chick pineal gland

Stimulus-induced transcription of the Period gene is a critical step for phase-shift of vertebrate circadian systems. The promoter region of chicken Period2 contains a canonical calcium/cAMP-responsive element, but its functional relevance is not known. The present study shows that cAMP-responsive element-binding protein (CREB) and activating transcription factor-2 (ATF-2) bind to the promoter region of the Period2 gene in the chick pineal gland. In transient transfection assays, a reporter construct containing 0.7-kbp upstream region of chicken Period2 was transactivated by ATF-2, but it was poorly responsive to CREB. In the chick pineal gland, phosphorylation of CREB protein at the kinase-inducible domain was negatively regulated by light. On the other hand, phosphorylation of ATF-2 at the amino-terminal transactivation domain exhibited a circadian rhythm with a daytime peak, suggesting a role for ATF-2 in circadian rhythmicity in the chick pineal gland.

p38 MAPK in regulating cellular responses to ultraviolet radiation

Solar ultraviolet (UV) radiation is a major environmental factor that causes DNA damage, inflammation, erythema, sunburn, immunosuppression, photoaging, gene mutations, and skin cancer. p38 mitogen activated protein kinase (MAPK) are strongly activated by UV radiation, and play important roles in regulating cellular responses to UV. In this review, we examine the role played by p38 MAPK in mediating UV-induced cell cycle, apoptosis, inflammation, and skin tanning response. We review the role played by p38 MAPK in transcriptional regulation of key downstream genes that have been implicated in the regulation of cellular responses to UV radiation. Understanding this will undoubtedly help in the prevention and control of UV-induced damage and the development of novel therapeutic strategies.

Effects of sodium ferulate on amyloid-beta-induced MKK3/MKK6-p38 MAPK-Hsp27 signal pathway and apoptosis in rat hippocampus

AIM

To observe the effects of sodium ferulate (SF) on amyloid beta (Abeta)1-40-induced p38 mitogen-activated protein kinase (MAPK) signal transduction pathway and the neuroprotective effects of SF.

METHODS

Rats were injected intracerebroventricularly with Abeta1-40. Six hours after injection, Western blotting was used to determine the expressions of phosphorylated mitogen-activated protein kinase kinase (MKK) 3/MKK6, phospho-p38 MAPK, interleukin (IL)-1beta, phospho-MAPK activating protein kinase 2 (MAPKAPK-2), the 27 kDa heat shock protein (Hsp27), procaspase-9, -3, and -7 cleavage, and poly (ADP-ribose) polymerase (PARP) cleavage. Seven days after injection, Nissl staining was used to observe the morphological change in hippocampal CA1 regions.

RESULTS

Intracerebroventricular injection of Abeta1-40 induced an increase in phosphorylated MKK3/MKK6 and p38 MAPK expressions in hippocampal tissue. These increases, in combination with enhanced interleukin (IL)-1beta protein expression and reduced phospho-MAPKAPK2 and phospho-Hsp27 expression, mediate the Abeta-induced activation of cell death events as assessed by cleavage of procaspase-9, -3, and -7 and caspase-3 substrate PARP cleavage. Pretreatment with SF (100 mg/kg and 200 mg/kg daily, 3 weeks) significantly prevented Abeta1-40-induced increases in phosphorylated MKK3/MKK6 and p38 MAPK expression. The Abeta1-40-induced increase in IL-1beta protein level was attenuated by pretreatment with SF. In addition, Abeta1-40-induced decreases in phosphorylated MAPKAPK2 and Hsp27 expression were abrogated by administration of SF. In parallel with these findings, Abeta1-40-induced changes in activation of caspase-9, caspase-7, and caspase-3 were inhibited by pretreatment with SF.

CONCLUSION

SF prevents Abeta1-40-induced neurotoxicity through suppression of MKK3/MKK6-p38 MAPK activity and IL-1beta expression and upregulation of phospho-Hsp27 expression.

p38 Mitogen-activated protein kinase activation in endothelial cell is implicated in cell alignment and elongation induced by fluid shear stress

Fluid shear stress is thought to be important in maintaining the phenotype of endothelial cells (ECs) in vivo. The purpose of the study was to determine the effect of varying levels of laminar shear stress on EC elongation and alignment and the role of p38 mitogen-activated protein kinase (MAPK) on the morphologic change induced by shear stress. Cultured bovine aortic ECs were subjected to 1, 4, 7, 14, or 20 dyne/cm(2) laminar steady shear stress. On morphometric analysis of static ECs, the average orientation angle was 41 degrees , whereas after 24 h shear stress at 1, 4, 7, 14, and 20 dyne/cm(2) the angles were 34 degrees, 33 degrees, 16 degrees, 11 degrees, and 10 degrees, respectively. The shape index of static ECs was 0.76, whereas the indexes of ECs exposed to shear stress were 0.72, 0.72, 0.65, 0.50, and 0.47, respectively. The time and the magnitude of activation of p38 MAPK were dependent on the level of shear stress. The results indicate that a minimum shear stress of 7 to 14 dynes/cm(2) is necessary for cell alignment and elongation and this correlates with activity of p38 MAPK. ECs exposed to shear stress in the presence of the p38 MAPK inhibitor SB-203580 did not orient in any manner and the shape index was similar to the static cells.

Palytoxin: exploiting a novel skin tumor promoter to explore signal transduction and carcinogenesis

Palytoxin is a novel skin tumor promoter, which has been used to help probe the role of different types of signaling mechanisms in carcinogenesis. The multistage mouse skin model indicates that tumor promotion is an early, prolonged, and reversible phase of carcinogenesis. Understanding the molecular mechanisms underlying tumor promotion is therefore important for developing strategies to prevent and treat cancer. Naturally occurring tumor promoters that bind to specific cellular receptors have proven to be useful tools for investigating important biochemical events in multistage carcinogenesis. For example, the identification of protein kinase C as the receptor for the prototypical skin tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) (also called phorbol 12-myristate 13-acetate, PMA) provided key evidence that tumor promotion involves the aberrant modulation of signaling cascades that govern cell fate and function. The subsequent discovery that palytoxin, a marine toxin isolated from zoanthids (genus Palythoa), is a potent skin tumor promoter yet does not activate protein kinase C indicated that investigating palytoxin action could help reveal new aspects of tumor promotion. Interestingly, the putative receptor for palytoxin is the Na(+),K(+)-ATPase. This review focuses on palytoxin-stimulated signaling and how palytoxin has been used to investigate alternate biochemical mechanisms by which important targets in carcinogenesis can be modulated.

Opposite Transcriptional Regulation in Skeletal Muscle of AMP-activated Protein Kinase γ3 R225Q Transgenic Versus Knock-out Mice

AMP-activated protein kinase (AMPK) is an evolutionarily conserved heterotrimer important for metabolic sensing in all eukaryotes. The muscle-specific isoform of the regulatory gamma-subunit of the kinase, AMPK gamma3, has an important role in glucose uptake, glycogen synthesis, and fat oxidation in white skeletal muscle, as previously demonstrated by physiological characterization of AMPK gamma3 mutant (R225Q) transgenic (TgPrkag3(225Q)) and gamma3 knock-out (Prkag3(-/-)) mice. We determined AMPK gamma3-dependent regulation of gene expression by analyzing global transcription profiles in glycolytic skeletal muscle from gamma3 mutant transgenic and knock-out mice using oligonucleotide microarray technology. Evidence is provided for coordinated and reciprocal regulation of multiple key components in glucose and fat metabolism, as well as skeletal muscle ergogenics in TgPrkag3(225Q) and Prkag3(-/-) mice. The differential gene expression profile was consistent with the physiological differences between the models, providing a molecular mechanism for the observed phenotype. The striking pattern of opposing transcriptional changes between TgPrkag3(225Q) and Prkag3(-/-) mice identifies differentially expressed targets being truly regulated by AMPK and is consistent with the view that R225Q is an activating mutation, in terms of its downstream effects. Additionally, we identified a wide array of novel targets and regulatory pathways for AMPK in skeletal muscle.

Selective activation of mitogen-activated protein (MAP) kinase kinase 3 and p38alpha MAP kinase is essential for cyclic AMP-dependent UCP1 expression in adipocytes

The sympathetic nervous system regulates the activity and expression of uncoupling protein 1 (UCP1) through the three beta-adrenergic receptor subtypes and their ability to raise intracellular cyclic AMP (cAMP) levels. Unexpectedly, we recently discovered that the cAMP-dependent regulation of multiple genes in brown adipocytes, including Ucp1, occurred through the p38 mitogen-activated protein kinases (MAPK) (W. Cao, K. W. Daniel, J. Robidoux, P. Puigserver, A. V. Medvedev, X. Bai, L. M. Floering, B. M. Spiegelman, and S. Collins, Mol. Cell. Biol. 24:3057-3067, 2004). However, no well-defined pathway linking cAMP accumulation or cAMP-dependent protein kinase (PKA) to p38 MAPK has been described. Therefore, in the present study using both in vivo and in vitro models, we have initiated a retrograde approach to define the required components, beginning with the p38 MAPK isoforms themselves and the MAP kinase kinase(s) that regulates them. Our strategy included ectopic expression of wild-type and mutant kinases as well as targeted inhibition of gene expression using small interfering RNA. The results indicate that the beta-adrenergic receptors and PKA lead to a highly selective activation of the p38alpha isoform of MAPK, which in turn promotes Ucp1 gene transcription. In addition, this specific activation of p38alpha relies solely on the presence of MAP kinase kinase 3, despite the expression in brown fat of MKK3, -4, and -6. Finally, of the three scaffold proteins of the JIP family expressed in brown adipocytes, only JIP2 co-immunoprecipitates p38alpha MAPK and MKK3. Therefore, in the brown adipocyte the recently described scaffold protein JIP2 assembles the required factors MKK3 and p38alpha MAPK linking PKA to the control of thermogenic gene expression.

Transcription inhibitors in inflammation

Advances in molecular medicine have revealed a key role for altered gene expression in the aetiology of many inflammatory diseases, including asthma, rheumatoid arthritis, inflammatory bowel disease and sepsis. Until recently, however, modulation of gene transcription has not been the subject of directed pharmaceutical research efforts. Notwithstanding, it is clear that the efficacy of several well-established anti-inflammatory therapeutics is mediated through their ability to modulate gene transcription. Understanding the mechanisms of action of these therapeutics and defining new gene regulatory pathways has stimulated a new wave of anti-inflammatory drug discovery. This update aims to cover our current understanding of transcription inhibitors in inflammation, including the mechanism of action of established therapeutics and the properties of new chemical entities recently described in the literature.

Inhibition of p38 mitogen-activated protein kinase protects the heart against cardiac remodeling in mice with heart failure resulting from myocardial infarction

BACKGROUND

Mitogen-activated protein kinases (MAPKs) have emerged as an important pathophysiologic regulator during the development of heart failure (HF). p38 MAPK activity is elevated in cardiac hypertrophy and HF. We used a mouse model of myocardial infarction (MI) to test the hypotheses that (1) inhibition of p38 MAPK activity may improve cardiac function and remodeling after myocardial infarction (MI) and (2) coadministration of a p38 inhibitor (p38i) and an angiotensin-converting enzyme inhibitor (ACEI) may provide only limited further cardioprotection in this model.

METHODS AND RESULTS

MI was induced in C57BL/6J mice by ligating the left anterior descending coronary artery and then either left untreated or treated with a p38i (SC-409, 30 mg/kg/day in chow), ACEI (enalapril, 20 mg/kg in drinking water), or p38i plus ACEI for 12 weeks. Echocardiography was performed and systolic blood pressure measured before MI and weekly thereafter. At the end of the study, interstitial collagen fraction (ICF) and myocyte cross-sectional area (MCSA) were examined histologically. We found that p38i significantly increased left ventricular ejection fraction and cardiac output and decreased left ventricular area at diastole, ICF, and MCSA. ACEi and p38i each had similar beneficial effects in this mouse model of HF produced by a large MI. Coadministration of p38i and ACEi did not provide any additional benefit.

CONCLUSION

Our data suggest that inhibition of p38 MAPK provides significant cardioprotection in mice with HF post-MI.

Regulation of p38 MAPK by MAPK kinases 3 and 6 in fibroblast-like synoviocytes

The p38 MAPK signal transduction pathway is a key regulator of IL-1 and TNF-alpha production in rheumatoid arthritis. Previous studies demonstrated that upstream MAPK kinases (MKK3 and MKK6) that regulate p38 are activated in rheumatoid arthritis synovium. However, their functional relevance in fibroblast-like synoviocytes (FLS) has not been determined. To investigate the relative contribution of MKK3 and MKK6 to p38 activation, the effect of dominant-negative (DN) MKK3 and MKK6 constructs on cultured FLS was evaluated. Cultured FLS were stimulated with medium or IL-1beta, and immunoblotting was performed. In some experiments, cells were lysed and immunoprecipitated with anti-p38 Ab, followed by in vitro kinase assay with [gamma-(32)P]ATP and GST-activating transcription factor-2 as substrate. IL-1beta rapidly induced p38 phosphorylation in cells transfected with empty vector (pcDNA3.1), but was inhibited by 25% in cells expressing DN MKK3 or DN MKK6. Cotransfection with both DN plasmids decreased phospho-p38 by almost 75%. In vitro kinase assays on IL-1-stimulated FLS also showed that the combination of DN MKK3 and DN MKK6 markedly decreased kinase activity compared with empty vector or the individual DN plasmids. Furthermore, IL-1beta-induced IL-8, IL-6, and matrix metalloproteinase-3 protein production was significantly inhibited in DN MKK3/DN MKK6-transfected cells. The constructs had no effect on the respective mediator mRNA levels. These data demonstrate that MKK3 and MKK6 make individual contributions to p38 activation in FLS after cytokine stimulation, but that both must be blocked for maximum inhibition.

p38 MAPK autophosphorylation drives macrophage IL-12 production during intracellular infection

The intracellular protozoan Toxoplasma gondii triggers rapid MAPK activation in mouse macrophages (Mphi). We used synthetic inhibitors and dominant-negative Mphi mutants to demonstrate that T. gondii triggers IL-12 production in dependence upon p38 MAPK. Chemical inhibition of stress-activated protein kinase/JNK showed that this MAPK was also required for parasite-triggered IL-12 production. Examination of upstream MAPK kinases (MKK) 3, 4, and 6 that function as p38 MAPK activating kinases revealed that parasite infection activates only MKK3. Nevertheless, in MKK3(-/-) Mphi, p38 MAPK activation was near normal and IL-12 production was unaffected. Recently, MKK-independent p38alpha MAPK activation via autophosphorylation was described. Autophosphorylation depends upon p38alpha MAPK association with adaptor protein, TGF-beta-activated protein kinase 1-binding protein-1. We observed TGF-beta-activated protein kinase 1-binding protein-1-p38alpha MAPK association that closely paralleled p38 MAPK phosphorylation during Toxoplasma infection of Mphi. Furthermore, a synthetic p38 catalytic-site inhibitor blocked tachyzoite-induced p38alpha MAPK phosphorylation. These data are the first to demonstrate p38 MAPK autophosphorylation triggered by intracellular infection.

Synthesis and Biological Activities of 4-Phenyl-5-pyridyl-1,3-thiazole Derivatives as p38 MAP Kinase Inhibitors

A novel series of 4-phenyl-5-pyridyl-1,3-thiazole analogues possessing potent in vitro inhibitory activity against p38 mitogen-activated protein kinase and the release of tumor necrosis factor-alpha (TNF-alpha) from human monocytic THP-1 cells stimulated by lipopolysaccharide has been identified. Subsequent structure-activity relationship (SAR) studies and optimization for absorption, distribution, metabolism, and elimination (ADME) profiles led to the identification of compounds 7 g and 10b as orally active lead candidates that block the in vivo production of proinflammatory cytokine (TNF-alpha). In pharmacokinetic studies, compound 10b showed good oral administration in mice and demonstrated significant in vivo anti-inflammatory activity in an anti-collagen monoclonal antibody-induced arthritis mouse model (minimum effective dose (MED)=30 mg/kg). Further elucidation of this class of compounds may provide novel anti-inflammatory agents, such as anti-rheumatoid arthritis drugs.

Potencial anti-apoptótico de p38 en cáncer de próstata

INTRODUCTION

TNF-alpha transduction pathway in prostate cancer seems to be diverted towards p38 activation. P38 may protect prostate tumoral cells from TNF-alpha apoptosis induced. The aim of this study was study the role of p38 in vivo (were evaluated some p38 downstream factors), as well as in vitro (in prostatic tumoral cell lines, LNCaP and PC3, pre-treated with TNF-alpha).

MATERIAL AND METHODS

Two prostatic tumoral cell lines (LNCaP and PC3) were used in in vitro studies. Two different experiments were made: with TNF-alpha (several concentrations) and p38 specific inhibitor (SB203580). The apoptotic index were evaluated using DAPI staining and flow cytometry. P38 activation was measured by Western blot analysis. 15 normal samples (NP) and 27 prostate cancer samples (PC) were used in in vivo study, all of them were processed for immunohistochemistry and Western-blot.

RESULTS

In vitro, TNF-alpha induced apoptosis in LnCap when we increased its concentration but not in PC3. TNF-alpha stimulation led to increase a time-dependent p38 phosphorylation in two intermediate doses whereas in PC3 not changes were found. In LNCaP after its preincubation with SB203580 and TNF-alpha treatment showed a significative increasing of apoptosis. In vivo, all NP samples were found positives to p-Elk-1 and p-ATF-2 (nuclei of epithelial cells). In PC the expression of p-Elk-1 or p-ATF-2 increased and was located in the nucleus and cytoplasm of epithelial cells.

CONCLUSION

Our data in vitro and in vivo suggest that p38 plays a very important role in prostatic tumour progression. These data suggest that the control activation of p38 might be a possible target to cancer prostate treatment.

Low dose beta-carotene supplementation of ferrets attenuates smoke-induced lung phosphorylation of JNK, p38 MAPK, and p53 proteins

We demonstrated previously that smoke exposure and/or high-dose beta-carotene supplementation decreases levels of retinoic acid and retinoic acid receptor beta (RARbeta) protein, but increase levels of c-Jun and proliferating cellular nuclear antigen protein in the lungs of ferrets. In contrast, low-dose beta-carotene can prevent the decreased lung retinoic acid and the smoke-induced lung lesions. In the present study, we investigated whether smoke exposure and/or beta-carotene supplementation could affect Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), and p53 in the lungs of ferrets. Ferrets were subjected to cigarette smoke exposure and either a high or low dose of beta-carotene (2 x 3 factorial design) for 6 mo. There were greater protein levels of phosphorylated JNK, p38, and c-Jun, but lower levels of MAPK phophatase-1 (MKP-1) in groups exposed to smoke and/or high dose beta-carotene. Both phosphorylated-p53 and total p53 were substantially increased in the lungs of these groups. In contrast, low-dose beta-carotene greatly attenuated the smoke-induced phosphorylation of JNK, p38, c-Jun, p53, and total p53, accompanied by upregulated MKP-1. Smoke exposure increased MAPK kinase-4 (MKK4) phosphorylation regardless of beta-carotene supplementation. These data indicate that restoration of retinoic acid and MKP-1 by low-dose beta-carotene in the lungs of ferrets may prevent the smoke-induced activation of the JNK-dependent signaling pathway, p38 MAPK, and the associated phosphorylation of p53, thereby lowering the risk of the smoke-related lung lesions. These data provide supportive evidence that the beneficial vs. detrimental effects of beta-carotene supplementation are related to the dosage of beta-carotene administered.

Expression and activation of mitogen-activated protein kinase kinases-3 and -6 in rheumatoid arthritis

The p38 mitogen-activated protein (MAP) kinase signal transduction pathway regulates the production of interleukin-1 and tumor necrosis factor-alpha. p38 kinase inhibitors are effective in animal models of arthritis and are currently being developed in rheumatoid arthritis (RA). However, little is known about the upstream kinases that control the activation of p38 in RA synovium. In vitro studies previously identified the MAP kinase kinases (MAPKKs) MKK3 and MKK6 as the primary regulators of p38 phosphorylation and activation. To investigate a potential role for MKK3 and MKK6 in RA, we evaluated their expression and regulation in RA synovium and cultured fibroblast-like synoviocytes (FLS). Immunohistochemistry demonstrated that MKK3 and MKK6 are expressed in RA and osteoarthritis (OA) synovium. Digital image analysis showed no significant differences between OA and RA with regard to expression or distribution. However, phosphorylated MKK3/6 expression was significantly higher in RA synovium and was localized to the sublining mononuclear cells and the intimal lining. Actin-normalized Western blot analysis of synovial tissue lysates confirmed the increased expression of phosphorylated MKK3/6 in RA. Western blot analysis demonstrated constitutive expression of MKK3 and MKK6 in RA and OA FLS. Phospho-MKK3 levels were low in medium-treated FLS, but were rapidly increased by interleukin-1 and tumor necrosis factor-alpha, although phospho-MKK6 levels only modestly increased. p38 co-immunoprecipitated with MKK3 and MKK6 from cytokine-stimulated FLS and the complex phosphorylated activating transcription factor-2 in an in vitro kinase assay. These data are the first documentation of MKK3 and MKK6 activation in human inflammatory disease. By forming a complex with p38 in synovial tissue and FLS, these kinases can potentially be targeted to regulate the production of proinflammatory cytokine production in inflamed synovium.

Chromatin-mediated regulation of nucleolar structure and RNA Pol I localization by TOR

The target of rapamycin (TOR) protein is a conserved regulator of ribosome biogenesis, an important process for cell growth and proliferation. However, how TOR is involved remains poorly understood. In this study, we find that rapamycin and nutrient starvation, conditions inhibiting TOR, lead to significant nucleolar size reduction in both yeast and mammalian cells. In yeast, this morphological change is accompanied by release of RNA polymerase I (Pol I) from the nucleolus and inhibition of ribosomal DNA (rDNA) transcription. We also present evidence that TOR regulates association of Rpd3-Sin3 histone deacetylase (HDAC) with rDNA chromatin, leading to site-specific deacetylation of histone H4. Moreover, histone H4 hypoacetylation mutations cause nucleolar size reduction and Pol I delocalization, while rpd3Delta and histone H4 hyperacetylation mutations block the nucleolar changes as a result of TOR inhibition. Taken together, our results suggest a chromatin-mediated mechanism by which TOR modulates nucleolar structure, RNA Pol I localization and rRNA gene expression in response to nutrient availability.