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991.
已有研究证实蟾毒灵具有抑制肿瘤细胞增殖及诱导细胞凋亡的作用,在白血病治疗中疗效显著,然而其机制尚未阐明。本研究试图探讨蟾毒灵对人红系白血病(HEL)细胞增殖,肾母细胞瘤基因1 (Wilms'tumor 1 gene, WT1)甲基化的影响及其可能的作用机制。本研究采用不同浓度的蟾毒灵处理HEL细胞,观察细胞形态、增殖情况和细胞周期,采用RT-PCR、Western blotting和免疫细胞化学法检测WT1的mRNA和蛋白表达水平,并用甲基化特异性分析WT1的DNA甲基化和DNA甲基转移酶3a (DNMT3a)的蛋白表达水平。研究结果表明,蟾毒灵对HEL细胞的增殖抑制作用呈剂量依赖性,抑制率为23.13%~84.62%。在蟾毒灵处理的HEL细胞中观察到典型的凋亡形态特征;细胞周期增殖指数由75.45降至49.67;WT1 mRNA及其蛋白表达水平随着蟾毒灵剂量的增加而逐渐降低,同时WT1基因的甲基化状态由未甲基化状态变为部分或完全甲基化状态。而蟾毒灵处理后DNMT3a蛋白的表达水平逐渐增加,呈剂量依赖性。我们的研究初步说明蟾毒灵不仅能显著抑制HEL细胞增殖,阻滞G0/G1期细胞周期,还能诱导细胞凋亡,下调WT1的表达水平。 相似文献
992.
Transforming growth factor-β (TGF-β) and glial-cell-line-derived neurotrophic factor (GDNF) have been shown to synergize in
several paradigms of neuronal survival. We have previously shown that cerebellar granule neurons (CGN) degenerate in low potassium
via ERK1/2 (extra-cellular-regulated kinase)-dependent plasma membrane (PM) damage and caspase-3-dependent DNA fragmentation.
Here, we have investigated the putative synergistic function of GDNF and TGF-β in CGN degeneration. GDNF alone prevents low-potassium-induced
caspase-3 activation and DNA fragmentation but does not affect either low-potassium-induced ERK activation or PM damage. TGF-β
alone does not affect low-potassium-induced DNA fragmentation but potentiates low-potassium-induced PM damage. This effect
of TGF-β is independent of ERK1/2 activation but dependent on p38-MAPK (mitogen-activated protein kinase) activation. When
co-applied with TGF-β, GDNF paradoxically antagonizes TGF-β-induced potentiation of PM damage by inhibiting TGF-β-induced
p38-MAPK activation. In addition, PI3K (phosphatidylinositol 3-kinase) inhibitors abolish the GDNF effect. This study thus
demonstrates a differential mechanism of action of GDNF and TGF-β on CGN degeneration. GDNF inhibits caspase-3-dependent DNA
fragmentation but does not affect ERK-dependent PM damage. However, GDNF can attenuate TGF-β-induced p38-MAPK-dependent PM
damage via the PI3K pathway.
This work was supported by the Deutsche Forschungsgemeinschaft (STR 616/1–2) and by a fellowship (Young Investigator Award)
from the Medical Faculty, University of Heidelberg, Germany to S. Subramaniam. 相似文献
993.
Amelioration of cadmium-induced cardiac impairment by taurine 总被引:1,自引:0,他引:1
The present study has been designed to investigate the protective role of taurine (2-aminoethanesulfonic acid), a sulfur containing conditionally essential amino acid, against cadmium-induced cardiac dysfunction in mice. Cadmium chloride (CdCl(2)) was used as the source of cadmium and it was administered orally at a dose of 4mg/kg body weight for 6 days. Cadmium exposure caused significant accumulation of the cadmium and iron in mice hearts tissue. Levels of serum specific markers related to cardiac impairments, e.g. total cholesterol, HDL cholesterol and triglyceride were altered due to cadmium toxicity. Reduction in the activities of antioxidant enzymes, namely, superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx) and glucose-6-phosphate dehydrogenase (G6PD) have been observed in cadmium exposed mice. Cadmium intoxication also decreased the cardiac glutathione (GSH) and total thiols contents and increased the levels of oxidized glutathione (GSSG), lipid peroxidation end products, protein carbonyl content and the extent of DNA fragmentation. Oral administration of taurine at a dose of 100mg/kg body weight for 5 days, however, prevented all the toxin-induced oxidative impairments mentioned above. "Ferric Reducing/Antioxidant Power (FRAP) assay" showed that taurine could protect the cardiac tissue by preventing cadmium-induced reduction of the intracellular antioxidant power. Histological examination of cardiac segments also supported the beneficial role of taurine against cadmium-induced damages in the murine hearts. Effect of a well established antioxidant, vitamin C has been included in the study as a positive control. Combining all, results suggest that taurine attenuates cadmium-induced impairment in mice hearts. 相似文献
994.
Marten H Hyun T Gomi K Seo S Hedrich R Roelfsema MR 《The Plant journal : for cell and molecular biology》2008,55(4):698-708
Light-induced stomatal opening in C3 and C4 plants is mediated by two signalling pathways. One pathway is specific for blue light and involves phototropins, while the second pathway depends on photosyntheticaly active radiation (PAR). Here, the role of Nt MPK4 in light-induced stomatal opening was studied, as silencing of this MAP kinase stimulates stomatal opening. Stomata of Nt MPK4-silenced plants do not close in elevated atmospheric CO2 , and show a reduced response to PAR. However, stomatal closure can still be induced by abscisic acid. Measurements using multi-barrelled intracellular micro-electrodes showed that CO2 activates plasma membrane anion channels in wild-type Nicotiana tabacum guard cells, but not in Nt MPK4-silenced cells. Anion channels were also activated in wild-type guard cells after switching off PAR. In approximately half of these cells, activation of anion channels was accompanied by an increase in the cytosolic free Ca2+ concentration. The activity of anion channels was higher in cells showing a parallel increase in cytosolic Ca2+ than in those with steady Ca2+ levels. Both the darkness-induced anion channel activation and Ca2+ signals were repressed in Nt MPK4-silenced guard cells. These data show that CO2 and darkness can activate anion channels in a Ca2+ -independent manner, but the anion channel activity is enhanced by parallel increases in the cytosolic Ca2+ concentration. Nt MPK4 plays an essential role in CO2 - and darkness-induced activation of guard-cell anion channels, through Ca2+ -independent as well as Ca2+ -dependent signalling pathways. 相似文献
995.
Recently, we demonstrated the transactivation of the epidermal growth factor receptor (EGFR) in response to interferon γ (IFNγ) in epidermoid carcinoma A431 cells. It was shown that IFNγ-induced EGFR transactivation is impossible in the some cancer epithelial cells. Here, we hypothesize that IFNγ-dependent EGFR transactivation in these cells correlates to the amount of EGFR on the surface of the cell. To test this suggestion, a line of stably transfected HEK293 cells (HEK293Δ99 cells) expressing a high level of mutant EGFR that lacked 99 C-terminal residues was obtained. Unlike the parent HEK293 cells, which lacked transactivation, HEK293Δ99 cells demonstrated EGFR transactivation in response to IFNγ. In HEK293Δ99 and A431 cells, the time courses of EGFR activation induced by IFNγ have the same pattern. In HEK293Δ99, as in A431 cells, IFNγ-induced EGFR transactivation requires EGFR kinase activity and occurs via an autophosphorylation mechanism. Taken together, these data provide direct evidence for the dependence of IFNγ-induced EGFR transactivation upon EGFR expression level in epithelial cells. 相似文献
996.
Characterization of a Nerve Growth Factor-Stimulated Protein Kinase in PC12 Cells Which Phosphorylates Microtubule-Associated Protein 2 and pp250 总被引:10,自引:5,他引:10
Gary E. Landreth Deanna S. Smith Craig McCabe Cynthia Gittinger 《Journal of neurochemistry》1990,55(2):514-523
Treatment of PC12 cells with nerve growth factor (NGF) resulted in the rapid, but transient, activation of a protein kinase which specifically phosphorylated an endogenous 250-kDa cytoskeletal protein (pp250). We report that the microtubule-associated protein, MAP2, is an alternative substrate for the NGF-activated kinase. NGF treatment maximally activated the kinase within 5 min; however, the activity declined with longer exposure to NGF. The enzyme was localized predominantly in microsomal and soluble fractions and phosphorylated MAP2 on serine and threonine residues. The soluble enzyme was fractionated by DEAE chromatography and gel filtration and had an apparent Mr of 45,000. The enzyme was purified to near homogeneity by chromatofocussing and had a pI of 4.9. Kinetic analysis revealed that NGF treatment caused a sevenfold increase in Vmax for MAP2. The Km with respect to the MAP2 substrate was approximately 50 nM and was not altered by NGF treatment. A novel feature of the NGF-stimulated enzyme was its sharp dependence on Mn2+ concentration. The active enzyme is likely to be phosphorylated, because inclusion of phosphatase inhibitors was required for recovery of optimal activity and the activity was lost on treatment of the enzyme with alkaline phosphatase. Histones, tubulin, casein, bovine serum albumin, and the ribosomal subunit protein S-6 were not phosphorylated by this enzyme. The NGF-stimulated kinase was distinct from A kinase, C kinase, or other NGF-stimulated kinases. The rapid and transient activation of the protein kinase upon NGF treatment suggests that the enzyme may play a role in signal transduction in PC12 cells. 相似文献
997.
Haruaki Uchiyama Koichi Ohara Kazuko Haga Tatsuya Haga Arata Ichiyama 《Journal of neurochemistry》1990,54(6):1870-1881
Muscarinic acetylcholine receptors purified from porcine cerebra or atria were covalently labeled with [3H]propylbenzilylcholine mustard ([3H]PrBCM), and then the labeled receptors were subjected to limited hydrolysis with trypsin, V8 protease, and lysyl endopeptidase, followed by analysis involving sodium dodecyl sulfate-polyacrylamide gel electrophoresis, fluorography, autoradiography, or immunostaining. The labeled peptides were located on the basis of their reactivity with antibodies raised against three synthetic peptides with partial sequences of the m1 or m2 receptor, and of their sensitivity to endoglycosidase F, which was taken as evidence that they contain glycosylation sites near the N terminus. The [3H]PrBCM-binding site in both cerebral and atrial receptors was found to be located between the N terminus and the second intracellular loop, because the size of the smallest deglycosylated peptide that contained both the [3H]PrBCM-binding and glycosylation sites was approximately 16 kDa. Cerebral receptors were 32P-phosphorylated with protein kinase C, and the major phosphorylation sites in cerebral muscarinic receptors were found to be located in a C-terminal segment including a part of the third intracellular loop, because a 32P-labeled peptide of 12-14 kDa reacted with anti-(m1 C-terminal peptide) antiserum. The presence of an intramolecular disulfide bond, probably between Cys 98 and Cys 178 in the first and second extracellular loops, respectively, was suggested by the finding that a peptide of approximately 17 kDa containing the [3H]PrBCM-binding site, but not the glycosylation sites, was partly converted to a peptide of approximately 12 kDa on treatment with beta-mercaptoethanol. 相似文献
998.
Catherin Niemann Volker Brinkmann Eva Spitzer Guido Hartmann Martin Sachs Helga Naundorf Walter Birchmeier 《The Journal of cell biology》1998,143(2):533-545
We have established a cell culture system that reproduces morphogenic processes in the developing mammary gland. EpH4 mouse mammary epithelial cells cultured in matrigel form branched tubules in the presence of hepatocyte growth factor/scatter factor (HGF/SF), the ligand of the c-met tyrosine kinase receptor. In contrast, alveolar structures are formed in the presence of neuregulin, a ligand of c-erbB tyrosine kinase receptors. These distinct morphogenic responses can also be observed with selected human mammary carcinoma tissue in explant culture. HGF/SF-induced branching was abrogated by the PI3 kinase inhibitors wortmannin and . In contrast, neuregulin- induced alveolar morphogenesis was inhibited by the MAPK kinase inhibitor PD98059. The c-met–mediated response could also be evoked by transfection of a c-met specific substrate, Gab1, which can activate the PI3 kinase pathway. An activated hybrid receptor that contained the intracellular domain of c-erbB2 receptor suffices to induce alveolar morphogenesis, and was observed in the presence of tyrosine residues Y1028, Y1144, Y1201, and Y1226/27 in the substrate-binding domain of c-erbB2. Our data demonstrate that c-met and c-erbB2 signaling elicit distinct morphogenic programs in mammary epithelial cells: formation of branched tubules relies on a pathway involving PI3 kinase, whereas alveolar morphogenesis requires MAPK kinase. LY294002相似文献
999.
Neuregulins: functions,forms, and signaling strategies 总被引:35,自引:0,他引:35
Falls DL 《Experimental cell research》2003,284(1):14-30
The neuregulins (NRGs) are cell-cell signaling proteins that are ligands for receptor tyrosine kinases of the ErbB family. The neuregulin family of genes has four members: NRG1, NRG2, NRG3, and NRG4. Relatively little is known about the biological functions of the NRG2, 3, and 4 proteins, and they are considered in this review only briefly. The NRG1 proteins play essential roles in the nervous system, heart, and breast. There is also evidence for involvement of NRG signaling in the development and function of several other organ systems, and in human disease, including the pathogenesis of schizophrenia and breast cancer. There are many NRG1 isoforms, raising the question "Why so many neuregulins?" Study of mice with targeted mutations ("knockout mice") has demonstrated that isoforms differing in their N-terminal region or in their epidermal growth factor (EGF)-like domain differ in their in vivo functions. These differences in function might arise because of differences in expression pattern or might reflect differences in intrinsic biological characteristics. While differences in expression pattern certainly contribute to the observed differences in in vivo functions, there are also marked differences in intrinsic characteristics that may tailor isoforms for specific signaling requirements, a theme that will be emphasized in this review. 相似文献
1000.
Matthijs G. P. Feenstra Margriet H. A. Botterblom Johanna F. M. van Uum 《Journal of neurochemistry》1998,70(3):1104-1113
Abstract: On-line in vivo microdialysis was used to determine the effects of a 16-min handling period on release of dopamine (DA) in the nucleus accumbens and of DA and noradrenaline (NA) in the medial prefrontal cortex of awake, freely moving rats. DA and NA were determined in one HPLC run. Handling resulted in an immediate and strong increase of both catecholamines in the prefrontal cortex. Maximal values for DA were 295%, and for NA 225%, of controls. DA in the nucleus accumbens was also increased (to 135% of controls) but only after a short delay. Local inhibition of ionotropic glutamate receptors by continuous reversed dialysis of the drugs 6-cyano-7-nitroquinoxaline, d -2-amino-5-phosphonopentanoic acid, or dizocilpine did not significantly affect handling-induced increases in cortical DA and NA release. Neither did the agonist of metabotropic glutamate receptors, trans -(1 S ,3 R )-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), or the GABA-B agonist baclofen. Reversed dialysis of dizocilpine in the nucleus accumbens was equally ineffective, but ACPD inhibited the increase in DA release in this area. Stimulation of metabotropic glutamate receptors in the nucleus accumbens was previously reported to inhibit activation of DA release in that area after stimulation of glutamatergic or dopaminergic afferents. It is concluded that metabotropic receptors in the nucleus accumbens are important for the control of activation of DA release in the accumbens by physiological stimuli but that a similar mechanism is lacking in the prefrontal cortex. 相似文献