1,720,969 research outputs found
Tumor necrosis factor-α regulates mRNA for urokinase-type plasminogen activator and type-1 plasminogen activator inhibitor in human neoplastic cell lines
No full textTumor necrosis factor-α (TNF-α) was found to induce type-1 plasminogen activator inhibitor (PAI-1) antigen in the human fibrosarcoma cell line HT-1080, and PAI-1 and urokinase-type plasminogen activator (u-PA) antigens in the human carcinoma cell line T-CAR1; tissue-type plasminogen activator (t-PA) antigen was not affected or slightly decreased. The effects in HT-1080 and T-CAR1 cells were preceded by increases in the cellular levels of the corresponding mRNAs. Cycloheximide caused an increase of PAI-1 mRNA in T-CAR1 cells, but not in HT-1080 cells; during this increase the relative abundance of the two PAI-1 mRNA species, of 2.3 kb and 3.4 kb, respectively, changed strongly in favor of the longer transcript. We conclude that TNF-α may affect proteolytic activity in the microenvironment of cells in malignant tumors by affecting gene expression of u-PA and PAI-1. © 1989
The regulatory region of the human plasminogen activator inhibitor type-1 (PAI-1) gene
No full textThe human gene for plasminogen activator inhibitor type-1 (PAI-1) has been isolated and its promoter region characterized. PAI-1 regulation by glucocortiooids, transforming growth factor-β (TGF-β) and the phorbol ester PMA is shown to be exerted at the promoter level. A fragment spanning 805 nuclectides of the 5′ flanking and 72 of the 5′ untraslated region contain information enough to promote transcription and to respond to glucocorticoids when fused to a reporter gene and transfected into human fibrosarccma cells. A moderately repectitive DNA sequence, containing a TATA box, a GRE consensus, a Z-DNA forming sequence and two imperfect direct repeats at the extremities, is present a few nucleotides 5′ of the human PAI-1 gene transcription start site, raising the possiblity that this gene could have been activated by DNA insertion during evolution. © 1988 IRL Press Limited
Plasminogen activator inhibitor type-1 protein, mRNA and gene transcription are increased by phorbol esters in human rhabdomyosarcoma cells
No full textBy use of an enzyme-linked immunosorbent assay, we have found that phorbol 12-myristate 13-acetate (PMA) causes an approximately 10-fold increase in the level of type-1 plasminogen activator inhibitor (PAI-1) accumulated in conditioned medium of the human rhabdomyosarcoma cell line. Half-maximal stimulation occurred at ≃15 nM PMA. The effect was only observed with phorbol esters that are tumor promoting. Maximal levels of secreted PAI-1 were observed 24 h after PMA addition. The increase in secreted PAI-I was preceded by a transient approximately 10-fold increase in intracellular PAI-1 content, maximal at 8 h after PMA addition. There was a 20-fold increase in the cellular level of two 2.3- and 3.4-kilobase PAI-1 mRNAs and a more than 5-fold increase in the PAI-1 gene transcription rate. The protein synthesis inhibitor cycloheximide (10 μg/ml) also increased the level of PAI-1 mRNA, and when both cycloheximide and PMA were used, an additive effect was observed. Cycloheximide changed the ratio between the two PAI-1 mRNAs in favor of the 3.4-kilobase species. Overall, the data show that transcriptional activation of the PAI-1 gene forms part of the pleiotropic responses to tumor-promoting phorbol esters
A common response element mediates differential effects of phorbol esters and forskolin on type‐1 plasminogen activator inhibitor gene expression in human breast carcinoma cells
No full textWe have characterized regulation of type‐1 plasminogen activator inhibitor (PAI‐1) gene expression by phorbol 12‐myristate 13‐acetate (PMA) and the cAMP‐inducing agent forskolin in the human breast carcinoma cell line MCF‐7. PMA caused a strong induction of PAI‐1, while forskolin suppressed the PMA response. Transfection experiments with fusion genes showed that sequences mediating PMA induction as well as forskolin suppression were present between base pairs –100 and –30 of the 57prime;‐flanking region of the PAI‐1 gene. The region was found to contain two Sp1 binding sites. A proximal sequence in the region, TGAGTTCA (P box), with sequence similarity to phorbol ester response elements (TRE) as well as to cAMP response elements (CRE), bound a low‐abundance, as yet unidentified nuclear protein in MCF‐7 cells. This sequence had a higher affinity to purified c‐jun homodimer than to c‐jun/c‐fos heterodimer in MCF‐7 nuclear extracts; it had no affinity to the proteins binding to CRE consensus sequences in these extracts. A distal TRE‐like sequence, TGAGTGG (D box), had a weak affinity to c‐jun/c‐fos heterodimer and c‐jun homodimer; binding of proteins to this sequence was facilitated by binding of proteins to the P box. Both the P box and the D box were necessary for PMA responsiveness, suggesting a cooperativity between the two binding sites. A mutation of the P box removing the CRE similarity abolished the forskolin suppression of the PMA response. We propose that the protein kinase C and the protein kinase A signal‐transduction pathways, with opposite effects on PAI‐1 gene expression, converge by modulating differently P‐box‐binding proteins. Copyright © 1994, Wiley Blackwell. All rights reserve
TRANSFORMING GROWTH FACTOR-BETA-1-RESPONSIVE ELEMENT - CLOSELY ASSOCIATED BINDING-SITES FOR USF AND CCAAT-BINDING TRANSCRIPTION FACTOR-NUCLEAR FACTOR-I IN THE TYPE-1 PLASMINOGEN-ACTIVATOR INHIBITOR GENE
No full textTransforming growth factor β (TGF-β) is the name of a group of closely related polypeptides characterized by a multiplicity of effects, including regulation of extracellular proteolysis and turnover of the extracellular matrix. Its cellular mechanism of action is largely unknown. TGF-β1 is a strong and fast inducer of type 1 plasminogen activator inhibitor gene transcription. We have identified a TGF-β1-responsive element in the 5'- flanking region of the human type 1 plasminogen activator inhibitor gene and shown that it is functional both in its natural context and when fused to a heterologous nonresponsive promoter. Footprinting and gel retardation experiments showed that two different nuclear factors, present in extracts from both TGF-β1-treated and nontreated cells, bind to adjacent sequences contained in the responsive unit. A palindromic sequence binds a trans-acting factor(s) of the CCAAT-binding transcription factor-nuclear factor I family. A partially overlapping dyad symmetry interacts with a second protein that much evidence indicates to be USF. USF is a transactivator belonging to the basic helix-loop-helix family of transcription factors. Mutations which abolish the binding of either CCAAT-binding transcription factor-nuclear factor I or USF result in reduction of transcriptional activation upon exposure to TGF-β1, thus showing that both elements of the unit are necessary for the TGF-β1 response. We discuss the possible relationship of these findings to the complexity of the TGF-β action
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
ALPHA-(2)-MACROGLOBULIN RECEPTOR LDL-RECEPTOR-RELATED-PROTEIN (LRP)-DEPENDENT INTERNALIZATION OF THE UROKINASE RECEPTOR
No full textThe GPI-anchored urokinase plasminogen activator receptor (uPAR) does not internalize free urokinase (uPA). On the contrary, uPAR-bound complexes of uPA with its serpin inhibitors PAI-1 (plasminogen activator inhibitor type-1) or PN-1 (protease nexin-l) are readily internalized in several cell types. Here we address the question whether uPAR is internalized as well upon binding of uPA-serpin complexes. Both LB6 clone 19 cells, a mouse cell line transfected with the human uPAR cDNA, and the human U937 monocytic cell line, express in addition to uPAR also the endocytic alpha(2)-macroglobulin receptor/low density lipoprotein receptor-related protein (LRP/alpha(2)-MR) which is required to internalize uPAR-bound uPA-PAI-1 and uPA-PN-1 complexes. Downregulation of cell surface uPAR molecules in U937 cells was detected by cytofluorimetric analysis after uPA-PAI-1 and uPA-PN-1 incubation for 30 min at 37 degrees C; this effect was blocked by preincubation with the ligand of LRP/alpha(2)-MR, RAP (LRP alpha(2)-MR-associated protein), known to block the binding of the uPA complexes to LRP/alpha(2)-MR. Downregulation correlated in time with the intracellular appearance of uPAR as assessed by confocal microscopy and immune-electron microscopy. After 30 min incubation with uPA-PAI-1 or uPA-PN-1 (but not with free uPA), confocal microscopy showed that uPAR staining in permeabilized LB6 clone 19 cells moved from a mostly surface associated to a largely perinuclear position. This effect was inhibited by the LRP/alpha(2)-MR RAP. Perinuclear uPAR did not represent newly synthesized nor a preexisting intracellular pool of uPAR, since this fluorescence pattern was not modified by treatment with the protein synthesis inhibitor cycloheximide, and since in LB6 clone 19 cells all of uPAR was expressed on the cell surface. Immuno-electron microscopy confirmed the plasma membrane to intracellular translocation of uPAR, and its dependence on LRP/alpha(2)-MR in LB6 clone 19 cells only after binding to the uPA-PAI-1 complex. After 30 min incubation at 37 degrees C with uPA-PAI-1, 93% of the specific immunogold particles were present in cytoplasmic vacuoles vs 17.6% in the case of DFP-uPA. We conclude therefore that in the process of uPA-serpin internalization, uPAR itself is internalized, and that internalization requires the LRP/alpha(2)-MR
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