km23‐1/DYNLRB1 regulation of MEK/ERK signaling and R‐Ras in invasive human colorectal cancer cells

We previously found that km23‐1/DYNLRB1 is required for transforming growth factor‐β (TGFβ) production through Ras/ERK pathways in TGFβ‐sensitive epithelial cells and in human colorectal cancer (CRC) cells. Here we demonstrate that km23‐1/DYNLRB1 is required for mitogen‐activated protein kinase kinase (MEK) activation in human CRC cells, detected by km23‐1/DYNLRB1‐siRNA inhibition of phospho‐(p)‐MEK immunostaining in RKO cells. Furthermore, we show that CRISPR‐Cas9 knock‐out (KO) of km23‐1/DYNLRB1 reduced cell migration in two additional CRC models, HCT116 and DLD‐1. Of interest, in contrast to our previous work showing that dynein motor activity was required for TGFβ‐mediated nuclear translocation of Smad2, in the current report, we demonstrate for the first time that disruption of dynein motor activity did not reduce TGFβ‐mediated activation of MEK1/2 or c‐Jun N‐terminal kinase (JNK). Moreover, size exclusion chromatography of RKO cell lysates revealed that B‐Raf, extracellular signal‐regulated kinase (ERK), and p‐ERK were not present in the large molecular weight fractions containing dynein holocomplex components. Furthermore, sucrose gradient fractionation of cell lysates from both HCT116 and CBS CRC cells demonstrated that km23‐1/DYNLRB1 co‐sedimented with Ras, p‐ERK, and ERK in fractions that did not contain components of holo‐dynein. Thus, km23‐1/DYNLRB1 may be associated with activated Ras/ERK signaling complexes in cell compartments that do not contain the dynein holoprotein complex, suggesting dynein‐independent km23‐1/DYNLRB1 functions in Ras/ERK signaling. Finally, of the Ras isoforms, R‐Ras is most often associated with cell migration, adhesion, and protrusive activity. Here, we show that a significant fraction of km23‐1/DYNLRB1 and RRas wase co‐localized at the protruding edges of migrating HCT116 cells, suggesting an important role for the km23‐1/DYNLRB1‐R‐Ras complex in CRC invasion.     

CCN2 expression and localization in melanoma cells

The matricellular protein connective tissue growth factor (CTGF, CCN2) is overexpressed in several forms of cancer and may represent a novel target in anti-cancer therapy. However, whether CCN2 is expressed in melanoma cells is unknown. The highly metastatic murine melanoma cell line B16(F10) was used for our studies. Real time polymerase chain reaction analysis was used to detect mRNA expression of CCN1, CCN2, CCN3 and CCN4 in Western blot and immunofluorescence analyses were used to detect CCN2 protein. Inhibitors of signal transduction cascades were used to probe the mechanism underlying CCN2 expression in B16(F10) cells. CCN2 was expressed in B16(F10) cells, and was reduced by the FAK/src inhibitor PP2 and the MEK/ERK inhibitor U0126 indicating that CCN2 acts downstream of these pathways in B16(F10) murine melanoma cells. Expression of CCN1, CCN3 and CCN4 was not reduced by PP2 or U0126; in fact, expression of CCN4 mRNA was elevated by PP2 or U0126 treatment. To our surprise, CCN2 protein was detected in the nuclei of B16(F10) cells, and was undetectable in the cytoplasm. CCN2 was expressed in B16(F10) melanoma cells, adding to the list of cancer cells in which CCN2 is expressed. Of the CCN family members tested, only CCN2 is downstream of the highly oncogenic MEK/ERK pathway. CCN2 should be further evaluated for a possible role in melanoma growth and progression.     

Astragaloside IV improves pulmonary arterial hypertension by increasing the expression of CCN1 and activating the ERK1/2 pathway

The aim of the present study was to investigate the underlying mechanism of AS-IV and CCN1 in PAH and to evaluate whether the protective effect of AS-IV against PAH is associated with CCN1 and its related signalling pathway. In vivo, male SD rats were intraperitoneally injected with monocrotaline (MCT, 60 mg/kg) or exposed to hypoxia (10% oxygen) and gavaged with AS-IV (20, 40 and 80 mg/kg/day) to create a PAH model. In vitro, human pulmonary artery endothelial cells (hPAECs) were exposed to hypoxia (3% oxygen) or monocrotaline pyrrole (MCTP, 60 μg/mL) and treated with AS-IV (10, 20 and 40 μM), EGF (10 nM, ERK agonist), small interfering CCN1 (CCN1 siRNA) and recombinant CCN1 protein (rCCN1, 100 ng/mL). We identified the differences in the expression of genes in the lung tissues of PAH rats by proteomics. At the same time, we dynamically detected the expression of CCN1 by Western blot both in vivo and in vitro. The Western blot experimental results showed that the expression of CCN1 increased in the early stage of PAH and decreased in the advanced stage of PAH. The results showed that compared with the control group, MCT- and hypoxia-induced increased the hemodynamic parameters and apoptosis. AS-IV can improve PAH, as characterized by decreased hemodynamic parameters, vascular wall area ratio (WA%), vascular wall thickness ratio (WT%) and α-SMA expression and inhibition of cell apoptosis. Moreover, the improvement of PAH by AS-IV was accompanied by increased CCN1 expression, which activated the ERK1/2 signalling pathway. Meanwhile, CCN1 and p-ERK1/2 were inhibited by siCCN1 and promoted by rCCN1. EGF not only activated the ERK1/2 signalling pathway but also induced the expression of CCN1. In conclusion, AS-IV improves PAH by increasing the expression of CCN1 and activating the ERK1/2 signalling pathway. The results of our study provide a theoretical basis for additional study on the protective effect of AS-IV against PAH.     

Cyclosporin A通过MEK/ERK1/2信号通路调节滋养细胞titin表达

探讨MEK/ERK1/2信号通路在Cyclosporin A(CsA)诱导滋养细胞表达titin中的作用。应用RT-PCR、Western blot检测CsA诱导的滋养细胞titin的表达水平,Western blot检测CsA作用于滋养细胞后ERK1/2的活化程度,并观察MEK特异性抑制剂U0126对其mRNA转录的影响。发现CsA以时间和剂量依赖方式诱导titin表达,并刺激滋养细胞ERK1/2的活化,U0126以剂量依赖方式抑制CsA诱导的titin表达。结果表明CsA通过活化MEK/ERK1/2信号通路诱导滋养细胞titin 的表达,改变其生物学行为,从而有利于胚胎着床及早期发育。     

Rab11a通过PI3K/AKT和Ras/MEK/ERK信号通路调节胰腺癌细胞凋亡和侵袭

目的:探究Rab11a在胰腺癌中的表达模式及其对肿瘤生长和转移的影响.方法:通过免疫组织化学法、RT-PCR和Western blot检测60例胰腺癌患者的癌组织和癌旁组织中Rab11a的表达.通过对人胰腺癌细胞系PANC1转染靶向Rab11a的小干扰RNA或过表达Rab11a的pcDNA3.1质粒考察Rab11a对细...     

沙眼衣原体生长依赖MEK/ERK信号通路的激活

衣原体感染可激活宿主细胞的MEK/ERK信号通路,但该信号通路对表原体生长的影响尚不清楚.通过Western blot和免疫荧光试验分别检测MEK/ERK信号通路阻断后沙眼衣原体(Chlamydia trachomatis,Ct)主要外膜蛋白(MOMP)表达及沙眼衣原体感染滴度的变化.研究MEK/ERK信号通路对沙眼衣原体生长的影响.研究发现,MEK/ERK信号通路阻断后MOMP表达减少,同时衣原体感染滴度也明显降低.结果表明沙眼衣原体的生长依赖MEK/ERK信号通路的激活.     

Association of RDM1 with osteosarcoma progression via cell cycle and MEK/ERK signalling pathway regulation

RAD52 motif-containing 1 (RDM1), a key regulator of DNA double-strand break repair and recombination, has been reported to play an important role in the development of various human cancers, such as papillary thyroid carcinoma, neuroblastoma and lung cancer. However, the effect of RDM1 on osteosarcoma (OS) progression remains unclear. Here, this study mainly explored the connection between RDM1 and OS progression, as well as the underlying mechanism. It was found that RDM1 was highly expressed in OS cells compared with human osteoblast cells. Knockdown of RDM1 caused OS cell proliferation inhibition, cell apoptosis promotion and cell cycle arrest at G1 stage, whereas RDM1 overexpression resulted in the opposite phenotypes. Furthermore, RDM1 silencing leads to a significant decrease in tumour growth in xenograft mouse model. RDM1 also increased the protein levels of MEK 1/2 and ERK 1/2. All these findings suggest that RDM1 plays an oncogenic role in OS via stimulating cell cycle transition from G1 to S stage, and regulating MEK/ERK signalling pathway, providing a promising therapeutic factor for the treatment of OS.     

Growth arrest signaling of the Raf/MEK/ERK pathway in cancer

The Raf/MEK/extraceUular signal-regulated kinase （ERK） pathway has a pivotal role in facilitating cell proliferation, and its deregulated activation is a central signature of many epithelial cancers. However paradoxically, sustained activity of Raf/MEK/ERK can also result in growth arrest in many different cell types. This anti-proliferative Raf/MEK/ERK signaling also has physiological significance, as exemplified by its potential as a tumor suppressive mechanism. Therefore, significant questions include in which cell types and by what mechanisms this pathway can mediate such an opposing context of signaling. Particularly, our understating of the role of ERK1 and ERK2, the focal points of pathway signaling, in growth arrest signaling is still limited. This review discusses these aspects of Raf/MEK/ ERK-mediated growth arrest signaling.     

NBS1 is required for IGF-1 induced cellular proliferation through the Ras/Raf/MEK/ERK cascade

NBS1 is a member of the Mre11–Rad50–NBS1 complex, which plays a role in cellular responses to DNA damage and the maintenance of genomic stability. Transgenic mice models and clinical symptoms of NBS patients have shown that NBS1 exerts pleiotropic actions on the growth and development of mammals. The present study showed that after repression of endogenous NBS1 levels using short interfering RNA, hTERT-RPE cells demonstrated impaired proliferation and a poor response to IGF-1. NBS1 down-regulated cells displayed disturbances in periodical oscillations of cyclin E and A and delayed cell cycle progression. Remarkably, lower phosphorylation levels of c-Raf and diminished activity of Erk1/2 in response to IGF-1 suggest a link among NBS1, IGF-1 signaling and the Ras/Raf/MEK/ERK cascade. The functional relevance of NBS1 in mitogenic signaling and initiation of cell cycle progression were demonstrated in NBS1 down-regulated cells where IGF-1 had a limited ability to induce the FOS and CCND1 expressions. In conclusion, our findings provide strong evidence that NBS1 has a functional role in IGF-1 signaling for the promotion of cell proliferation via the Ras/Raf/MEK/ERK cascade.     

PARP-1-induced cell death through inhibition of the MEK/ERK pathway in MNNG-treated HeLa cells

Poly(ADP-ribose) polymerase-1 (PARP-1) hyper-activation promotes cell death but the signaling events downstream of PARP-1 activation are not fully identified. To gain further information on the implication of PARP-1 activation and PAR synthesis on signaling pathways influencing cell death, we exposed HeLa cells to the DNA alkylating agent N-methyl-N′-methyl-nitro-N-nitrosoguanidine (MNNG). We found that massive PAR synthesis leads to down-regulation of ERK1/2 phosphorylation, Bax translocation to the mitochondria, release of cytochrome c and AIF and subsequently cell death. Inhibition of massive PAR synthesis following MNNG exposure with the PARP inhibitor PJ34 prevented those events leading to cell survival, whereas inhibition of ERK1/2 phosphorylation by inhibiting MEK counteracted the cytoprotective effect of PJ34. Together, our results provide evidence that PARP-1-induced cell death by MNNG exposure in HeLa cells is mediated in part through inhibition of the MEK/ERK signaling pathway and that inhibition of massive PAR synthesis by PJ34, which promotes sustained activation of ERK1/2, leads to cytoprotection.     

Synthesis and study of benzothiazole conjugates in the control of cell proliferation by modulating Ras/MEK/ERK-dependent pathway in MCF-7 cells

By applying a methodology, a series of benzothiazole–pyrrole based conjugates (4a–r) were synthesized and evaluated for their antiproliferative activity. Compounds such as 4a, 4c, 4e, 4g–j, 4m, 4n, 4o and 4r exhibited significant cytotoxic effect in the MCF-7 cell line. Cell cycle effects were examined for these conjugates at 2 μM as well as 4 μM concentrations and FACS analysis show an increase of G2/M phase cells with concomitant decrease of G1 phase cells thereby indicating G2/M cell cycle arrest by them. Interestingly 4o and 4r are effective in causing apoptosis in MCF-7 cells. Moreover, 4o showed down regulation of oncogenic expression of Ras and its downstream effector molecules such as MEK1, ERK1/2, p38 MAPK and VEGF. The apoptotic aspect of this conjugate is further evidenced by increased expression of caspase-9 in MCF-7 cells. Hence these small molecules have the potential to control both the cell proliferation as well as the invasion process in the highly malignant breast cancers.     

Upregulation of Ras/Raf/ERK1/2 signaling and ERK5 in the brain of autistic subjects

Autism is a neurodevelopmental disorder characterized by impairments in social interaction, verbal communication and repetitive behaviors. A number of studies have shown that the Ras/Raf/ERK1/2 (extracellular signal-regulated kinase) signaling pathway plays important roles in the genesis of neural progenitors, learning and memory. Ras/Raf/ERK1/2 and ERK5 have also been shown to have death-promoting apoptotic roles in neural cells. Recent studies have shown a possible association between neural cell death and autism. In addition, two recent studies reported that a deletion of a locus on chromosome 16, which included the mitogen-activated protein kinase 3 (MAPK3) gene that encodes ERK1, is associated with autism. Most recently, our laboratory detected that Ras/Raf/ERK1/2 signaling activities were significantly enhanced in the brain of BTBR mice that model autism, as they exhibit many autism-like behaviors. We thus hypothesized that Ras/Raf/ERK1/2 signaling and ERK5 could be abnormally regulated in the brain of autistic subjects. In this study, we show that the expression of Ras protein was significantly elevated in the frontal cortex of autistic subjects. C-Raf phosphorylation was increased in the frontal cortex, while both C-Raf and A-Raf activities were enhanced in the cerebellum of autistic subjects. We also detected that both the protein expression and activities of ERK1/2 were significantly upregulated in the frontal cortex of autistic subjects, but not in the cerebellum. Furthermore, we showed that ERK5 protein expression is upregulated in both frontal cortex and cerebellum of autistic subjects. These results suggest that the upregulation of Ras/Raf/ERK1/2 signaling and ERK5 activities mainly found in the frontal cortex of autistic subjects may be critically involved in the pathogenesis of autism.     

Involvement of MEK5/ERK5 signaling pathway in manganese-induced cell injury in dopaminergic MN9D cells

BackgroundOver-exposure to manganese (Mn) causes irreversible movement disorders with signs and symptoms similar, but not identical, to idiopathic Parkinson's disease (IPD). Recent data suggest that Mn toxicity occurs in dopaminergic (DA) neurons, although the mechanism remains elusive. This study was designed to investigate whether Mn interfered the apoptotic signaling transduction cascade in DA neurons.MethodsMouse midbrain dopaminergic MN9D cells were exposed to Mn in a concentration range of 0, 400, 800, or 1200 μM as designated as control, low, medium, and high exposure groups, respectively. The flow cytometry with Annexin V/PI double staining and immunohistochemistry were used to assess the apoptosis.ResultsData indicated that Mn exposure caused morphological alterations typical of apoptosis, increased apoptotic cells by 2–8 fold, and produced reactive oxidative species (ROS) by 1.5–2.2 fold as compared to controls (p < 0.05). Studies by qPCR and Western blot revealed that Mn exposure significantly increased the protein expression of extracellular signal-regulated kinase-5 (ERK5) and mitogen-activated ERK kinase-5 (MEK5) (p < 0.05). The presence of BIX02189, a specific inhibitor of MER/ERK, caused a much greater cytotoxicity, i.e., higher cell death, more ROS production, and worsened apoptosis, than did the treatment with Mn alone. Following Mn exposure, the expression of a downstream effector Bcl- 2 was reduced by 48 % while those of Bax and Caspase-3 were increased by 266.7 % and 90.1 %, respectively, as compared to controls (p < 0.05).ConclusionTaken together, these data provide the initial evidence that the signaling transduction cascade mediated by MEK5/ERK5 is responsible to Mn-induced cytotoxicity; Mn exposure, by suppressing anti-apoptotic function while facilitating pro-apoptotic activities, alters neuronal cell’s survival and functionally inhibits DA production by MN9D cells.