技术资料

Protein kinase CK2 (formerly casein kinase II) is a serine/threonine kinase overexpressed in many human tumors,transformed cell lines,and rapidly proliferating tissues. Recent data have shown that many cancers involve inappropriate reactivation of Wnt signaling through ectopic expression of Wnts themselves,as has been seen in a number of human breast cancers,or through mutation of intermediates in the Wnt pathway,such as adenomatous polyposis coli or beta-catenin,as described in colon and other cancers. Wnts are secreted factors that are important in embryonic development,but overexpression of certain Wnts,such as Wnt-1,leads to proliferation and transformation of cells. We report that upon stable transfection of Wnt-1 into the mouse mammary epithelial cell line C57MG,morphological changes and increased proliferation are accompanied by increased levels of CK2,as well as of beta-catenin. CK2 and beta-catenin co-precipitate with the Dvl proteins,which are Wnt signaling intermediates. A major phosphoprotein of the size of beta-catenin appears in in vitro kinase reactions performed on the Dvl immunoprecipitates. In vitro translated beta-catenin,Dvl-2,and Dvl-3 are phosphorylated by CK2. The selective CK2 inhibitor apigenin blocks proliferation of Wnt-1-transfected cells,abrogates phosphorylation of beta-catenin,and reduces beta-catenin and Dvl protein levels. These results demonstrate that endogenous CK2 is a positive regulator of Wnt signaling and growth of mammary epithelial cells. View Publication

Y-27632 [(+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide++ + dihydrochloride] is widely used as a specific inhibitor of the Rho-associated coiled-coil forming protein serine/threonine kinase (ROCK) family of protein kinases. This study examined the inhibition mechanism and profile of actions of Y-27632 and a related compound,Y-30141 [(+)-(R)-trans- 4-(1-aminoethyl)-N-(1H-pyrrolo[2,3-b]pyridin-4-yl)cyclohexan-ecarboxamide dihydrochloride]. Y-27632 and Y-30141 inhibited the kinase activity of both ROCK-I and ROCK-II in vitro,and this inhibition was reversed by ATP in a competitive manner. This suggests that these compounds inhibit the kinases by binding to the catalytic site. Their affinities for ROCK kinases as determined by K(i) values were at least 20 to 30 times higher than those for two other Rho effector kinases,citron kinase and protein kinase PKN. [(3)H]Y-30141 was taken up by cells in a temperature- and time-dependent and saturable manner,and this uptake was competed with unlabeled Y-27632. No concentrated accumulation was found,suggesting that the uptake is a carrier-mediated facilitated diffusion. Y-27632 abolished stress fibers in Swiss 3T3 cells at 10 microM,but the G(1)-S phase transition of the cell cycle and cytokinesis were little affected at this concentration. Y-30141 was 10 times more potent than Y-27632 in inhibiting the kinase activity and stress fiber formation,and it caused significant delay in the G(1)-S transition and inhibition of cytokinesis at 10 microM. View Publication

Green tea has shown remarkable anti-inflammatory and cancer chemopreventive effects in many animal tumor bioassays,cell culture systems,and epidemiological studies. Many of these biological effects of green tea are mediated by epigallocatechin 3-gallate (EGCG),the major polyphenol present therein. We have earlier shown that EGCG treatment results in apoptosis of several cancer cells,but not of normal cells (J. Natl. Cancer Inst. 89,1881-1886 (1997)). The mechanism of this differential response of EGCG is not known. In this study,we investigated the involvement of NF-kappaB during these differential responses of EGCG. EGCG treatment resulted in a dose-dependent (i) inhibition of cell growth,(ii) G0/G1-phase arrest of the cell cycle,and (iii) induction of apoptosis in human epidermoid carcinoma (A431) cells,but not in normal human epidermal keratinocytes (NHEK). Electromobility shift assay revealed that EGCG (10-80 microM) treatment results in lowering of NF-kappaB levels in both the cytoplasm and nucleus in a dose-dependent manner in both A431 cells and NHEK,albeit at different concentrations. EGCG treatment was found to result in a dose-based differential inhibition of TNF-alpha- and LPS-mediated activation of NF-kappaB in these cells. The inhibition of NF-kappaB constitutive expression and activation in NHEK was observed only at high concentrations. The immunoblot analysis also demonstrated a similar pattern of inhibition of the constitutive expression as well as activation of NF-kappaB/p65 nuclear protein. This inhibition of TNF-alpha-caused NF-kappaB activation was mediated via the phosphorylative degradation of its inhibitory protein IkappaBalpha. Taken together,EGCG was found to impart differential dose-based NF-kappaB inhibitory response in cancer cells vs normal cells; i.e.,EGCG-mediated inhibition of NF-kappaB constitutive expression and activation was found to occur at much higher dose of EGCG in NHEK as compared to A431 cells. This study suggests that EGCG-caused cell cycle deregulation and apoptosis of cancer cells may be mediated through NF-kappaB inhibition. View Publication

U937 monocytic cells are shown here to express a range of PDE4,cAMP-specific phosphodiesterase (PDE) isoenzymes: the long isoenzymes,PDE4A4,PDE4D5 and PDE4D3,plus the short isoenzyme,PDE4B2. These isoenzymes provide around 76% of the total cAMP PDE activity of U937 cells. The specific activities of the total PDE4A,PDE4B and PDE4D activities were 0.63+/-0.09,8.8+/-0.2 and 34.4+/-2.9 pmol/min per mg of protein respectively. The PDE4 selective inhibitor,rolipram,inhibited immunopurified PDE4B and PDE4D activities similarly,with IC(50) values of approx. 130 nM and 240 nM respectively. In contrast,rolipram inhibited immunopurified PDE4A activity with a dramatically lower IC(50) value of around 3 nM. Rolipram increased phosphorylation of cAMP-response-element-binding protein (CREB) in U937 cells in a dose-dependent fashion,which implied the presence of both high affinity (IC(50) value approx. 1 nM) and low affinity (IC(50) value approx. 120 nM) components. Rolipram dose-dependently inhibited the interferon-gamma (IFN-gamma)-stimulated phosphorylation of p38 mitogen-activated protein (MAP) kinase in a simple monotonic fashion with an IC(50) value of approx. 290 nM. On this basis,it is suggested that rolipram inhibition of PDE4A4 is involved in regulating CREB phosphorylation but not IFN-gamma-stimulated p38 MAP kinase phosphorylation. PDE4A4 was also selectively activated by challenge of U937 cells with either bacterial lipopolysaccharide (LPS) or IFN-gamma through a process which was attenuated by both wortmannin and rapamycin. It is proposed that the PDE4A4 isoform is involved in compartmentalized cAMP signalling responses in U937 monocytes. View Publication

Cell fate during development is defined by transcription factors that act as molecular switches to activate or repress specific gene expression programmes. The POU transcription factor Oct-3/4 (encoded by Pou5f1) is a candidate regulator in pluripotent and germline cells and is essential for the initial formation of a pluripotent founder cell population in the mammalian embryo. Here we use conditional expression and repression in embryonic stem (ES) cells to determine requirements for Oct-3/4 in the maintenance of developmental potency. Although transcriptional determination has usually been considered as a binary on-off control system,we found that the precise level of Oct-3/4 governs three distinct fates of ES cells. A less than twofold increase in expression causes differentiation into primitive endoderm and mesoderm. In contrast,repression of Oct-3/4 induces loss of pluripotency and dedifferentiation to trophectoderm. Thus a critical amount of Oct-3/4 is required to sustain stem-cell self-renewal,and up- or downregulation induce divergent developmental programmes. Our findings establish a role for Oct-3/4 as a master regulator of pluripotency that controls lineage commitment and illustrate the sophistication of critical transcriptional regulators and the consequent importance of quantitative analyses. View Publication

Potent inhibition of Janus kinase 3 was found for a series of naphthyl(beta-aminoethyl)ketones (e.g. 7,pIC50 = 7.1+/-0.3). Further studies indicated that these compounds fragment in less than 1 h by retro-Michael reaction in the Jak3 in vitro ELISA assay procedure. The breakdown product of 7,2-naphthylvinyl ketone (22,pIC50 = 6.8+/-0.3) showed very similar inhibitory activity to 7. Compounds 7 (in neutral buffer) and 22 will be useful pharmacological tools for the investigation of the Janus tyrosine kinase Jak3. View Publication

Adult human mesenchymal stem cells are primary,multipotent cells capable of differentiating to osteocytic,chondrocytic,and adipocytic lineages when stimulated under appropriate conditions. To characterize the molecular mechanisms that regulate osteogenic differentiation,we examined the contribution of mitogen-activated protein kinase family members,ERK,JNK,and p38. Treatment of these stem cells with osteogenic supplements resulted in a sustained phase of ERK activation from day 7 to day 11 that coincided with differentiation,before decreasing to basal levels. Activation of JNK occurred much later (day 13 to day 17) in the osteogenic differentiation process. This JNK activation was associated with extracellular matrix synthesis and increased calcium deposition,the two hallmarks of bone formation. Inhibition of ERK activation by PD98059,a specific inhibitor of the ERK signaling pathway,blocked the osteogenic differentiation in a dose-dependent manner,as did transfection with a dominant negative form of MAP kinase kinase (MEK-1). Significantly,the blockage of osteogenic differentiation resulted in the adipogenic differentiation of the stem cells and the expression of adipose-specific mRNAs peroxisome proliferator-activated receptor gamma2,aP2,and lipoprotein lipase. These observations provide a potential mechanism involving MAP kinase activation in osteogenic differentiation of adult stem cells and suggest that commitment of hMSCs into osteogenic or adipogenic lineages is governed by activation or inhibition of ERK,respectively. View Publication

Hematologic malignancies such as acute and chronic myeloid leukemia are characterized by the malignant transformation of immature CD34(+) progenitor cells. Transformation is associated with elevated expression of the Wilm's tumor gene encoded transcription factor (WT1). Here we demonstrate that WT1 can serve as a target for cytotoxic T lymphocytes (CTL) with exquisite specificity for leukemic progenitor cells. HLA-A0201- restricted CTL specific for WT1 kill leukemia cell lines and inhibit colony formation by transformed CD34(+) progenitor cells isolated from patients with chronic myeloid leukemia (CML),whereas colony formation by normal CD34(+) progenitor cells is unaffected. Thus,the tissue-specific transcription factor WT1 is an ideal target for CTL-mediated purging of leukemic progenitor cells in vitro and for antigen-specific therapy of leukemia and other WT1-expressing malignancies in vivo. View Publication

We report here the cloning,expression,and characterization of human PDE11A1,a member of a distinct cyclic nucleotide phosphodiesterase (PDE) family. PDE11A exhibits textless/=50% amino acid identity with the catalytic domains of all other PDEs,being most similar to PDE5,and has distinct biochemical properties. The human PDE11A1 cDNA isolated contains a complete open reading frame encoding a 490-amino acid enzyme with a predicted molecular mass of 55,786 Da. At the N terminus PDE11A1 has a single GAF domain homologous to that found in other signaling molecules,including PDE2,PDE5,PDE6,and PDE10,which constitutes a potential allosteric binding site for cGMP or another small ligand. Tissue distribution studies indicate that PDE11A mRNA occurs at highest levels in skeletal muscle,prostate,kidney,liver,pituitary,and salivary glands and testis. PDE11A is expressed as at least three major transcripts of approximately 10.5,approximately 8.5,and approximately 6.0 kb,thus suggesting the existence of multiple subtypes. This possibility is further supported by the detection of three distinct proteins of approximately 78,approximately 65,and approximately 56 kDa by Western blotting of human tissues for PDE11A isoforms. Recombinant human PDE11A1 hydrolyzes both cGMP and cAMP with K(m) values of 0.52 microM and 1.04 microM,respectively,and similar V(max) values. Therefore,PDE11A represents a dual-substrate PDE that may regulate both cGMP and cAMP under physiological conditions. PDE11A is sensitive to the nonselective PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX) as well as zaprinast and dipyridamole,inhibitors that are generally considered relatively specific for the cGMP-selective PDEs,with IC(50) values of 49.8 microM,12.0 microM,and 0.37 microM,respectively. View Publication

The small heat-shock protein HSP25 is expressed in the heart early during development,and although multiple roles for HSP25 have been proposed,its specific role during development and differentiation is not known. P19 is an embryonal carcinoma cell line which can be induced to differentiate in vitro into either cardiomyocytes or neurons. We have used P19 to examine the role of HSP25 in differentiation. We found that HSP25 expression is strongly increased in P19 cardiomyocytes. Antisense HSP25 expression reduced the extent of cardiomyocyte differentiation and resulted in reduced expression of cardiac actin and the intermediate filament desmin and reduced level of cardiac mRNAs. Thus,HSP25 is necessary for differentiation of P19 into cardiomyocytes. In contrast,P19 neurons did not express HSP25 and antisense HSP25 expression had no effect on neuronal differentiation. The phosphorylation of HSP25 by the p38/SAPK2 pathway is known to be important for certain of its functions. Inhibition of this pathway by the specific inhibitor SB203580 prevented cardiomyocyte differentiation of P19 cells. In contrast,PD90589,which inhibits the ERK1/2 pathway,had no effect. Surprisingly,cardiogenesis was only sensitive to SB203580 during the first 2 days of differentiation,before HSP25 expression increases. In contrast to the effect of antisense HSP25,SB203580 reduced the level of expression of the mesodermal marker Brachyury-T during differentiation. Therefore,we propose that the p38 pathway acts on an essential target during early cardiogenesis. Once this initial step is complete,HSP25 is necessary for the functional differentiation of P19 cardiomyocytes,but its phosphorylation by p38/SAPK2 is not required. View Publication

Retinoic acid derivatives (retinoids) exert their pleiotropic effects on cell development through specific nuclear receptors,the retinoic acid receptors and retinoid X receptors. Despite recent progress in understanding the cellular and molecular mechanisms of retinoid activity,it is unknown which of the retinoid receptor pathways are involved in the specific processes of sebocyte growth and development. In this study,we investigated the roles of specific retinoid receptors in sebocyte growth and differentiation,by testing the effects of selective retinoic acid receptor and retinoid X receptor ligands at concentrations between 10-10 M and 10-6 M in a primary rat preputial cell monolayer culture system. Cell growth was determined by number of cells and colonies,and cell differentiation by analysis of lipid-forming colonies. All-trans retinoic acid and selective retinoic acid receptor agonists (CD271 = adapalene,an RAR-beta,gamma agonist; CD2043 = retinoic acid receptor pan-agonist; and CD336 = Am580,an RAR-alpha agonist) caused significant decreases in numbers of cells,colonies,and lipid-forming colonies,but with an exception at high doses of all-trans retinoic acid (10-6 M),with which only a small number of colonies grew but they became twice as differentiated as controls (42.2 +/- 4.0% vs 22.6 +/- 2.7%,mean +/- SEM,lipid-forming colonies,p textless 0.01). Furthermore,the RAR-beta,gamma antagonist CD2665 antagonized the suppressive effects of all-trans retinoic acid,adapalene,and CD2043 on both cell growth and differentiation. In contrast,the retinoid X receptor agonist CD2809 increased cell growth slightly and lipid-forming colonies dramatically in a clear dose-related manner to a maximum of 73.7% +/- 6.7% at 10-6 M (p textless 0. 001). Our data suggest that retinoic acid receptors and retinoid X receptors differ in their roles in sebocyte growth and differentiation: (i) retinoic acid receptors,especially the beta and/or gamma subtypes,mediate both the antiproliferative and antidifferentiative effects of retinoids; (ii) retinoid X receptors mediate prominent differentiative and weak proliferative effects; (iii) the antiproliferative and antidifferentiative effects of all-trans retinoic acid are probably mediated by retinoic acid receptors,whereas its differentiative effect at high dose may be mediated by retinoid X receptors via all-trans retinoic acid metabolism to 9-cis retinoic acid,the natural ligand of retinoid X receptors. View Publication

We studied the suitability of collagen-based semisolid medium for assay of endogenous erythroid colony formation performed in myeloproliferative disorders. Bone marrow (BM) mononuclear cells (MNC) from 103 patients suspected of having polycythemia vera (PV,76 patients) or essential thrombocythemia (ET,27 patients) were grown in collagen-based,serum-free,cytokine-free semisolid medium. Colony analysis at day 8 or 10 showed that this collagen assay is specific,as endogenous growth of erythroid colonies was never observed in cultures of 16 healthy donors and 6 chronic myelogenous leukemia (CML) patients. Endogenous erythroid colony formation was observed in 53.3% of patients suspected of PV,with only 15.4% of positive cultures for patients with 1 minor PV criterion and 72% (p = 0.009) of positive cultures for patients with textgreater or =2 minor or 1 major PV criterion. Similarly,endogenous growth of erythroid colonies was found in 44.4% of patients suspected of ET,with 31.6% of positive cultures for patients with 1 ET criterion versus 75% for patients with textgreater or =2 ET criteria. In addition,we found that in collagen gels,tests of erythropoietin (EPO) hypersensitivity in the presence of 0.01 or 0.05 U/ml of EPO and tests of endogenous colony-forming units-megakaryocyte (CFU-MK) formation cannot be used to detect PV or ET,as these tests were positive for,respectively,21.4% and 50% of healthy donors and 83% and 50% of CML patients. A retrospective analysis suggests that collagen assays are more sensitive than methylcellulose assays to assess endogenous growth of erythroid colonies. In summary,serum-free collagen-based colony assays are simple and reliable assays of endogenous growth of erythroid colonies in myeloproliferative diseases. They also appear to be more sensitive than methylcellulose-based assays. View Publication