Computational Screening of Novel Mitogen-activated Protein Kinase Kinase-1 （MEK1） Inhibitors by Docking and Scoring

The mitogen-activated protein kinase （MAPK） cell signal transduction pathways play a key role in determining the survival of cells. If these pathways can be controlled, they will prohibit the proliferation of cancer cells. To attain this goal, the authors utilize many drugs to interact with mitogen-activated protein kinase kinase-1 （MEK1） in MAPK, and use computer aided drug design （CADD） to analyze the ligand activities of proteins in MEKL The results show that in these drugs, the aromatic group in the terminal of the protein and the PHE209 will induce the stacking force, which is highly related to the actual activities of these drugs.

Mitogen-activated protein kinase-activated protein kinase 2 regulates tumor necrosis factor-induced interleukin-6 expression via human antigen R

Background Human antigen R （HuR） is a ubiquitously expressed member of the ELAV family, and has relatively high cytoplasmic abundance in lung tissue regenerating after injury. In this study, we investigated whether mitogen-activated protein kinase （MAPK）-activated protein kinase 2 （MK2） and HuR participate in the tumor necrosis factor （TNF）-induced expression of interleukin-6 （IL-6）. Methods Human pulmonary microvascular endothelial cells were treated with TNF following short interfering RNAmediated knockdown of MK2 or HuR. Cell supernatants were collected to detect the mRNA and protein expression of IL-6 at different time points, The expression and half-life of IL-6 mRNA were then determined in cells that had been treated with actinomycin D. Finally, after knockdown of MK2, the cytoplasmic expression of HuR protein was analyzed using Western blotting. Results MK2 or HuR knockdown decreased both the mRNA and protein expression of IL-6 in TNF-stimulated cells. In MK2 knockdown cells, the half-life of IL-6 mRNA was reduced to 36 minutes, compared with 67 minutes in the control group. In HuR knockdown cells, the half-life of IL-6 mRNA decreased from 62 minutes to 24 minutes. Further analysis revealed that knockdown of MK2 resulted in reduced HuR protein expression in the cytoplasm. Conclusions MK2 regulates the TNF-induced expression of IL-6 by influencing the cytoplasmic levels of HuR.

Mechanisms of extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor signal transduction pathway in depressive disorder

The extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor signal transduction pathway plays an important role in the mechanism of action of antidepressant drugs and has dominated recent studies on the pathogenesis of depression. In the present review we summarize the known roles of extracellular signal-regulated kinase, cAMP response element-binding protein and brain-derived neurotrophic factor in the pathogenesis of depression and in the mechanism of action of antidepressant medicines. The extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor pathway has potential to be used as a biological index to help diagnose depression, and as such it is considered as an important new target in the treatment of depression.

Ethylene signaling is required for the acceleration of cell death induced by the activation of AtMEK5 in Arabidopsis

Mitogen-activated protein kinases （MAPKs） are involved in the regulation of plant growth, development and responses to a wide variety of stimuli. In a conditional gain-of-function transgenic system, the activation of AtMEKS, a MAPK kinase, can in turn activate endogenous AtMAPK3 and AtMAPK6, and can lead to a striking increase in ethylene production and induce hypersensitive response （HR）-like cell death in Arabidopsis. However, the role of the increased ethylene production in regulating this HR-like cell death remains unknown. Using Arabidopsis transgenic plants that express AtMEK5DD, an active mutant of AtMEK5 that is under the control of a steroid-inducible promoter, we tested the contribution of ethylene to cell death. We found that ethylene biosynthesis occurs before cell death. Cell death was delayed by inhibiting AtMEKS-induced ethylene production using inhibitors ofACC-synthases, ACC- oxidases or ethylene receptors. In the mutants AtMEK5^DD/etrl-1 and AtMEK5^DD/ein2-1, both of which showed insensitivity to ethylene, the expression ofAtMEK5DD protein, activity of AtMAPK3 and AtMAPK6, and ethylene produc- tion were the same as those seen in AtMEK5^DD transgenic plants, but cell death was also delayed. These data suggest that ethylene signaling perception is required to accelerate cell death that is induced by AtMEK5 activation.

Septin 8 is an interaction partner and in vitro substrate of MK5

AIM:To identify novel substrates for the mitogen-activated protein kinase-activated protein kinase 5(MK5).METHODS:Yeast two-hybrid screening with MK5 as bait was used to identify novel possible interaction partners.The binding of putative partner was further examined by glutathione S-transferase(GST) pull-down,co-immunoprecipitation and fluorescence resonance energy transfer(FRET) analysis.In vitro kinase and peptide array assays were used to map MK5 phosphoacceptor sites on the new partner.Confocal microscopy was performed to study the subcellular localization of MK5 and its partners.RESULTS:Septin 8 was identified as a novel interaction partner for MK5 by yeast two-hybrid screening.This interaction was confirmed by GST pull-down,coimmunoprecipitation and FRET analysis.Septin 5,which can form a complex with septin 8,did not interact with MK5.Serine residues 242 and 271 on septin 8 were identified as in vitro MK5 phosphorylation sites.MK5 and septin 8 co-localized in the perinuclear area and in cell protrusions.Moreover,both proteins co-localized with vesicle marker synaptophysin.

Scaffold protein MAPK8IP2 expression is a robust prognostic factor in prostate cancer associated with AR signaling activity

Mitogen-activated protein kinase-8-interacting protein 2(MAPK8IP2)is a scaffold protein that modulates MAPK signal cascades.Although MAPK pathways were heavily implicated in prostate cancer progression,the regulation of MAPK8IP2 expression in prostate cancer is not yet reported.We assessed MAPK8IP2 gene expression in prostate cancer related to disease progression and patient survival outcomes.MAPK8IP2 expression was analyzed using multiple genome-wide gene expression datasets derived from The Cancer Genome Atlas(TCGA)RNA-sequence project and complementary DNA(cDNA)microarrays.Multivariable Cox regressions and log-rank tests were used to analyze the overall survival outcome and progression-free interval.MAPK8IP2 protein expression was evaluated using the immunohistochemistry approach.The quantitative PCR and Western blot methods analyzed androgen-stimulated MAPK8IP2 expression in LNCaP cells.In primary prostate cancer tissues,MAPK8IP2 mRNA expression levels were significantly higher than those in the case-matched benign prostatic tissues.Increased MAPK8IP2 expression was strongly correlated with late tumor stages,lymph node invasion,residual tumors after surgery,higher Gleason scores,and preoperational serum prostate-specific antigen(PSA)levels.MAPK8IP2 upregulation was significantly associated with worse overall survival outcomes and progression-free intervals.In castration-resistant prostate cancers,MAPK8IP2 expression strongly correlated with androgen receptor(AR)signaling activity.In cell culture-based experiments,MAPK8IP2 expression was stimulated by androgens in AR-positive prostate cancer cells.However,MAPK8IP2 expression was blocked by AR antagonists only in androgen-sensitive LNCaP but not castration-resistant C4-2B and 22RV1 cells.These results indicate that MAPK8IP2 is a robust prognostic factor and therapeutic biomarker for prostate cancer.The potential role of MAPK8IP2 in the castration-resistant progression is under further investigation.

pORF5 plasmid protein of Chlamydia trachomatis induces MAPK-mediated pro-inflammatory cytokines via TLR2 activation in THP-1 cells

Infection with Chlamydia trachomatis induces inflammatory pathologies in the urogenital tract that can lead to infertility and ectopic pregnancy. Pathogenesis of infection has been mostly attributed to excessive cytokine production. However, precise mechanisms on how C. trachomatis triggers this production, and which protein（s） stimulate inflammatory cytokines remains unknown. In the present study, the C. trachomatis pORF5 protein induced tumor necrosis factor alpha （TNF-a）, interleukin-1 beta （IL-1β） and interleukin-8 （IL-8） in dose and time-dependent manners in the THP-1 human monocyte cell line. We found that intracellular p38/mitogen-activated protein kinase （MAPK） and extracellular signal-regulated kinase （ERK）/MAPK signaling pathways were required for the induction of TNF- a, IL-1β and IL-8. Blockade of toll-like receptor 2 （TLR2） signaling reduced induction levels of TNF-a, IL-8 and IL-1β. We concluded that the C. trachomatis pORF5 protein might contribute to the inflammatory processes associated with chlamydial infections.

mRNA expression of DOK1-6 in human breast cancer

AIM:To examine the expression of downstream of tyrosine kinase(DOK)1-6 genes in normal and breast cancer tissue and correlated this with several clinicopathological and prognostic factors.METHODS:DOK1-6 m RNA extraction and reverse transcription were performed on fresh frozen breast cancer tissue samples(n = 112) and normal background breast tissue(n = 31). Tissues were collected between 1991 and 1996 at two centres and all patients underwent mastectomy and ipsilateral axillary node dissection. All tissues were randomly numbered and the details were only made known after all analyses were completed. Transcript levels of expression were determined using real-time polymerase chain reaction and analyzed against TNM stage, tumour grade and clinical outcome over a 10-year follow-up period.RESULTS:DOK-2 and DOK-6 expression decreased with increasing TNM stage. DOK-6 expression decreased with increasing Nottingham Prognostic Index(NPI) [NPI-1 vs NPI-3(mean copy number 15.4 vs 0.22, 95%CI:2.7-27.6, P = 0.018) and NPI-2 vs NPI-3(mean copy number 7.6 vs 0.22, 95%CI:0.1-14.6, P = 0.048)]. After a median follow up period of 10 years, higherlevels of DOK-2 expression were found among patients who remained disease-free compared to those who developed local or distant recurrence(mean copy number 3.94 vs 0.0000096, 95%CI:1.0-6.85, P = 0.0091), and distant recurrence(mean copy number 3.94 vs 0.0025, 95%CI:1.0-6.84, P = 0.0092). Patients who remained disease-free had higher levels of DOK-6 expression compared to those who died from breast cancer.CONCLUSION:Decreasing expression levels of DOK-2 and DOK-6 with increased breast tumour progression supports the notion that DOK-2 and DOK-6 behave as tumour suppressors in human breast cancer.

TRAIL-induced apoptosis of hepatocellular carcinoma cells is augmented by targeted therapies

AIM:To analyze the effect of chemotherapeutic drugs and specific kinase inhibitors,in combination with the death receptor ligand tumor necrosis factor-related apoptosis inducing ligand(TRAIL),on overcoming TRAIL resistance in hepatocellular carcinoma(HCC)and to study the efficacy of agonistic TRAIL antibodies,as well as the commitment of antiapoptotic BCL-2 proteins, in TRAIL-induced apoptosis. METHODS:Surface expression of TRAIL receptors (TRAIL-R1-4)and expression levels of the antiapoptotic BCL-2 proteins MCL-1 and BCL-xL were analyzed by flow cytometry and Western blotting,respectively. Knock-down of MCL-1 and BCL-xL was performed by transfecting specific small interfering RNAs.HCC cellswere treated with kinase inhibitors and chemotherapeutic drugs.Apoptosis induction and cell viability were analyzed via flow cytometry and 3-(4,5-Dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. RESULTS:TRAIL-R1 and-R2 were profoundly expressed on the HCC cell lines Huh7 and Hep-G2. However,treatment of Huh7 and Hep-G2 with TRAIL and agonistic antibodies only induced minor apoptosis rates.Apoptosis resistance towards TRAIL could be considerably reduced by adding the chemotherapeutic drugs 5-fluorouracil and doxorubicin as well as the kinase inhibitors LY294002[inhibition of phosphoinositol- 3-kinase(PI3K)],AG1478(epidermal growth factor receptor kinase),PD98059(MEK1),rapamycin(mam- malian target of rapamycin)and the multi-kinase inhibitor Sorafenib.Furthermore,the antiapoptotic BCL-2 proteins MCL-1 and BCL-xL play a major role in TRAIL resistance:knock-down by RNA interference increased TRAIL-induced apoptosis of HCC cells.Additionally, knock-down of MCL-1 and BCL-xL led to a significant sensitization of HCC cells towards inhibition of both c-Jun N-terminal kinase and PI3K.CONCLUSION:Our data identify the blockage of survival kinases,combination with chemotherapeutic drugs and targeting of antiapoptotic BCL-2 proteins as promising ways to overcome TRAIL resistance in HCC.

Unilateral amyloid-β25-35 injection into the rat amygdala increases the expressions of aberrant tau phosphorylation kinases

Background Neuropathologically, Alzheimer disease （AD） is characterized by the presence of extracellular plaques enriched in β-amyloid peptides; however, the mechanism by which it results in the neurotoxicity is uncertain. The purpose of this study was to investigate whether it would prompt the progress of Alzheimer disease via enhancement of aberrant phosphorylated tau that results from its increased kinase gene expression. Methods Twenty-four male rats were divided into three groups, and each group had 8 rats： control, sham-operated, and Aβ25-35 injected AD model groups. AD rat models were created by unilateral injections of Aβ25-35 into the amygdala. The hyperphosphorylated tau protein was estimated by immunohistochemistry with paired helical filament-1 （PHF-1） antibody and paired helical filament-tau （AT8） antibody. The expressions of glycogen synthase kinase-3β （GSK-3β） and p38 mitogen-activated protein kinase （P38MAPK） mRNA were observed by in situ hybridization. Results Compared with the control and sham-operated groups, the evaluation of paired AT8 and paired helical filament-1 （PHF-1） in the cortexes and hippocampus of the AD model group showed the numbers of AT8 and PHF-1 positive cells, as well as the optical density （OD） values of the proteins were significantly higher （AT8： in CA2： 0.318±0.037 vs. 0.135±0.028, 0.136±0.031; in frontal cortex： 0.278±0.040 vs. 0.130±0.028, 0.190±0.037. PHF-1 ： in CA2： 0.386±0.034 vs. 0.139±0.010, 0.193±0.041; in frontal cortex： 0.395±0.050 vs. 0.159±0.030, 0.190±0.044, respectively, P 〈0.01）; the number of GSK-3β mRNA and P38MAPK mRNA positive cells of the AD model group, as well as the OD values, also increased significantly in the cortexes, hippocampus （GSK-3β-mRNA： in CA2：0.384±0.012 vs. 0.190±0.015, 0.258±0.064; in frontal cortex： 0.398±0.018 vs. 0.184±0.031, 0.218±0.049. P38MAPK mRNA： in CA2：0.409±0.038 vs. 0.161±0.041, 0.189±0.035; in frontal cortex： 0.423±0.070 vs. 0.160±0.032, 0.203±0.053, respectively, P 〈0.01）. Conclusion Unilateral injection of Aβ25-35 into the rat amygdala increases the generation of aberrant phosphorylated tau by increasing GSK-3β and PasMAPKgene expression, that accelerates the process of Alzhemer＇s disease.

Development of small molecule extracellular signal-regulated kinases(ERKs) inhibitors for cancer therapy

The mitogen-activated protein kinase(MAPK)/extracellular signal-regulated kinase 1/2(ERK1/2) signaling pathway is widely activated by a variety of extracellular stimuli, and its dysregulation is associated with the proliferation, invasion, and migration of cancer cells. ERK1/2 is located at the distal end of this pathway and rarely undergoes mutations, making it an attractive target for anticancer drug development. Currently, an increasing number of ERK1/2 inhibitors have been designed and synthesized for antitumor therapy, among which representative compounds have entered clinical trials. When ERK1/2 signal transduction is eliminated, ERK5 may provide a bypass route to rescue proliferation, and weaken the potency of ERK1/2 inhibitors. Therefore, drug research targeting ERK5 or based on the compensatory mechanism of ERK5 for ERK1/2 opens up a new way for oncotherapy. This review provides an overview of the physiological and biological functions of ERKs, focuses on the structure-activity relationships of small molecule inhibitors targeting ERKs, with a view to providing guidance for future drug design and optimization, and discusses the potential therapeutic strategies to overcome drug resistance.