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W D Schleuning

Publications and source records attributed to W D Schleuning.

At least 55 records · Page 3Linked to original sources
PubMed1993

Interaction of urokinase-type plasminogenactivator (u-PA) with its cellular receptor (u-PAR) induces phosphorylation on tyrosine of a 38 kDa protein.

We demonstrate by immunoprecipitation that u-PAR is associated with a 38 kDa protein that is phosphorylated on tyrosine after u-PA treatment of cells. As tyrosine phosphorylation is the hallmark of many signal transduction pathways that promote growth and differentiation, these data suggest that u-PA, besides its role as a regulatory protease, might act as a para- or autocrine hormone.

Chromatography, Affinity↗
PubMed1993

Bovine urokinase-type plasminogen activator and its receptor: cloning and induction by retinoic acid.

Full-length cDNAs encoding bovine urokinase-type plasminogen activator (u-PA) and urokinase receptor (u-PAR) were cloned from an aortic endothelial cell cDNA library using PCR-amplified cDNA fragments as probes. Bovine u-PA amino acid identity ranges from 79.5 to 70.9% when compared to its pig, human, baboon and mouse analogues, while bovine u-PAR is 61.8 and 59.6% identical to its human and mouse counterparts, respectively. All Cys residues previously found in mature u-PA and u-PAR from these different species are also conserved in the bovine molecules. Bovine u-PA and its cell-surface receptor display one and six potential sites of N-linked glycosylation, respectively. Northern blot hybridization demonstrated a moderate induction of u-PA and u-PAR mRNA in bovine aortic endothelial cells after treatment with 10 nM and 1 microM retinoic acid for 8 hours.

Amino Acid Sequence↗
PubMed1993

Expression of human endothelin receptor ETB by Escherichia coli transformants.

Membrane fractions from Escherichia coli transformed with an expression vector for the human endothelin receptor ETB were found to exhibit specific and saturable binding sites for labeled ET-1. Binding properties were similar to those observed in eukaryotic cells: KD was 110 pM and the three endothelin isoforms were equipotent in competition experiments. The importance of the cysteines located in each of the three extracellular loops was assessed by replacing them individually with alanine residues. Impaired binding was observed in each case but the effect was far more pronounced for the cysteine mutants of the first and second loop pointing to their critical importance for active ETB expression.

Base Sequence↗
PubMed1993

Bibrotoxin, a novel member of the endothelin/sarafotoxin peptide family, from the venom of the burrowing asp Atractaspis bibroni.

A new member of the endothelin/sarafotoxin family of vasoconstrictor peptides, bibrotoxin (BTX), was isolated from the venom of the burrowing asp Atractaspis bibroni by reversed-phase FPLC. The amino acid sequence of BTX differs from SRTX-b in the substitution Ala4 instead of Lys4, which suggests that it represents the peptide isoform of Atractaspis bibroni corresponding to SRTX-b. BTX competed for [125I]ET-1 binding to human ETB-type receptor with a Ki of 3.2 x 10(-9) M compared to 4.2 x 10(-9) M for SRTX-b. In rat thorax aorta BTX induced vasoconstrictions with a threshold concentration of 3 x 10(-8) M compared to 1 x 10(-9) for ET-1.

Amino Acid Sequence↗
PubMed1993

Extracellular cysteine residues 174 and 255 are essential for active expression of human endothelin receptor ETB in Escherichia coli.

The coding sequences for the non-isopeptide-selective human endothelin receptor ETB were introduced into the prokaryotic expression vector pKK233-2, and the resulting construct was used for transformation of competent E. coli JM105 cells. Specific binding was observed for bacterial membrane fractions, using labeled ET-1 as a ligand. Site-directed mutagenesis was employed to individually modify the triplets for the cysteines of the first and second extracellular loops of ETB to alanine codons. E. coli JM105 transformed with the mutated plasmids no longer displayed specific ET-1 binding to membranes, which suggests a crucial role for these extracellular cysteines in agonist binding or receptor stability.

Cell Membrane↗
PubMed1993

Binding characteristics of recombinant human endothelin receptors ETA and ETB expressed in baby hamster kidney cells.

Expression constructs for human endothelin (ET) receptors ETA and ETB were made by subcloning the corresponding coding sequences into the pMPSV/CMV vector. They were used together with plasmids bearing resistances to puromycin and hygromycin for transfection of baby hamster kidney cells. Culture in the presence of both antibiotics allowed the selection of cell lines stably expressing one receptor or the other. Competitive binding experiments using ET-1 and ET-3 showed the typical isopeptide-selective and non-isopeptide-selective profiles for recombinant ETA and ETB, respectively.

Animals↗
PubMed1993

Transcripts for cysteine-rich secretory protein-1 (CRISP-1; DE/AEG) and the novel related CRISP-3 are expressed under androgen control in the mouse salivary gland.

Expression of the gene for cysteine-rich secretory protein-1 (CRISP-1), the counterpart of the rat sperm-coating protein DE/AEG, was evidenced in male mouse salivary gland by both isolation of the corresponding cDNA clone and RNA blot analysis. In addition, the cDNA coding for the new related CRISP-3, which shares 77% amino acid identity with CRISP-1, was isolated from a salivary gland cDNA library. The activity of CRISP-1 and -3 genes in mouse salivary gland is strongly androgen dependent, as seen in castrated males; also, no CRISP-1 and only weak CRISP-3 expression was detected in female salivary gland. A variety of tissues were tested for the presence of CRISP-3 transcripts, but specific signals were only found in salivary gland. The results of genomic DNA blot analysis are compatible with the existence of single discrete genes for CRISP-1 and CRISP-3.

Amino Acid Sequence↗
PubMed1992

Plasminogen activators from the saliva of Desmodus rotundus (common vampire bat): unique fibrin specificity.

The saliva of D. rotundus contains at least four plasminogen activators (PAs) which all require fibrin as a cofactor. D. rotundus salivary PAs (DSPAs) exhibit a sequential array of structural motifs such as "Finger" (F), "EGF" (E), "Kringle" (K) and "Protease" (P) which was elucidated by cDNA cloning and sequencing. The respective domain organizations are: FEKP (DSPA alpha 1 and DSPA alpha 2), EKP (DSPA beta) and KP (DSPA gamma). In all four forms the plasmin-sensitive site of tPA is obliterated, indicating that they function as single-chain enzymes. DSPA alpha 1 differs from alpha 2 by amino acid substitutions found mainly in the F, E and K domain, 11% of the total sequence. DSPA beta and gamma, while being closely related to alpha 2, still exhibit 2 and 13 amino acid exchanges, respectively. These sequence heterogeneities, together with results of Southern blot hybridization experiments, strongly suggest that the four DSPA mRNA species originate from different genes. All four forms of DSPA have been expressed in animal cell culture and DSPA alpha 1 was chosen for a detailed pharmacological characterization. In vitro DSPA alpha 1 activity is enhanced 50,000-fold in the presence of fibrin, whereas the activity of single chain tPA is only enhanced 100-fold. At equally effective thrombolytic doses DSPA causes lower bleeding incidence in a rat mesenteric vein model and exhibits high potency, clot selectivity, and speed in the dissolution of fibrin embolized into the lung of anesthetized rats. In the copper coil-induced dog coronary heart infarction model, at doses that achieve patency at equal rates, reocclusion is significantly less frequent than with tPA. These results indicate that DSPA alpha 1 may be a safer and more efficacious thrombolytic agent than the PAs currently in clinical use.

Amino Acid Sequence↗
PubMed1992

High-level secretion of the four salivary plasminogen activators from the vampire bat Desmodus rotundus by stably transfected baby hamster kidney cells.

The cDNAs coding for the four Desmodus rotundus salivary plasminogen activators (DSPAs) were subcloned into the mammalian expression vector, pMPSV/CMV, which carries the myeloproliferative sarcoma virus promoter and the cytomegalovirus enhancer. These constructs were transfected, together with plasmids harbouring Geneticin (G418)-resistance and puromycin-resistance genes, into baby hamster kidney cells. Through the selective pressure of both antibiotics, cell clones constitutively overexpressing the DSPA alpha 1, DSPA alpha 2, DSPA beta or DSPA gamma cDNAs were obtained. Secretion of active DSPAs was confirmed by zymographic analysis and quantified using a fibrin plate assay and ELISA.

Animals↗
PubMed1992

Cell-specific regulation of plasminogen activator inhibitor 1 and tissue type plasminogen activator release by human kidney mesangial cells.

Human mesangial cells in culture synthesize and secrete plasminogen activator inhibitor 1 (PAI-1) and tissue-type plasminogen activator (t-PA). Phorbol myristate acetate (PMA), a known activator of protein kinase C, induces a three to four-fold increase in t-PA and PAI-1 release over a period of 24 h, whereas cell-associated t-PA and PAI-1 levels remain relatively stable. A similar effect is obtained with oleylacetyl glycerol, a more physiologic protein kinase C activator. The effect of PMA is suppressed in the presence of H7, an inhibitor of cellular protein kinases, and by cycloheximide and actinomycin D, indicating a requirement for de novo protein and RNA synthesis, respectively. Northern blot analysis of PMA-treated cells reveals a rapid and transient increase in PAI-1 mRNA reaching a maximum after 4-8 h, whereas increase in t-PA mRNA levels requires 24 h. Activation of protein kinase A by addition of 8-bromocyclic AMP (8-bromo cAMP) has no significant effect on PAI-1 release but inhibits the PMA-mediated increases in PAI-1 antigen and mRNA. Addition of 8-bromo cAMP alone does not affect t-PA release. When added to PMA-stimulated cells, 8-bromo cAMP inhibits t-PA release in a dose-dependent manner, but causes a superinduction of t-PA mRNA. 8-bromo cAMP also induces a decrease in PMA-stimulated intracellular t-PA release. Similar inhibition is observed after stimulation of endogenous adenylate cyclase with prostaglandin E1 or isoproterenol. This indicates that protein kinase A activation may inhibit PMA-stimulated t-PA release via a post-transcriptional effect, e.g. inhibition of protein synthesis or activation of protein degradation. In conclusion, hormones or mediators which activate protein kinase C can stimulate t-PA and PAI-1 synthesis in human mesangial cells. Protein kinase A activation has no effect on the basal release of PAI-1 and t-PA by human mesangial cells, and, in contrast to endothelial cells, it inhibits both PMA-stimulated PAI-1 and t-PA releases. This cell-specific regulation of t-PA and PAI-1 seems to be mediated by differential transcriptional and post transcriptional mechanisms.

Blotting, Northern↗
PubMed1992

Thrombolytic properties of Desmodus rotundus (vampire bat) salivary plasminogen activator in experimental pulmonary embolism in rats.

rDSPA alpha 1 (recombinant Desmodus salivary plasminogen activator alpha 1) is a recombinant protein corresponding to a natural plasminogen activator from the vampire bat Desmodus rotundus. The thrombolytic properties of rDSPA alpha 1 and tissue-type plasminogen activator (t-PA) were compared in a rat model of pulmonary embolism. Whole blood clots, produced in vitro and labeled with 125I-fibrinogen, were embolized into the lungs of anesthetized rats. Thrombolysis was calculated from the difference between initial clot radioactivity and that remaining in the lungs at 60 minutes. Blood was sampled for gamma counting, measurement of hemostatic factors, and plasminogen activator antigen levels. Thrombolysis at 3, 10, 30, and 100 nmol/kg intravenously (10% bolus, 90% over 60 minutes) amounted to 30% +/- 2%, 51% +/- 4%, 85% +/- 4%, 98% +/- 0% for rDSPA alpha 1 and 30% +/- 3%, 41% +/- 3%, 57% +/- 6%, 93% +/- 2% for t-PA (controls: 29% +/- 2%; mean +/- SEM, n greater than or equal to 6). t-PA at 100 nmol/kg significantly decreased fibrinogen, plasminogen, and alpha 2-antiplasmin levels by 33% +/- 7%, 38% +/- 8%, and 61% +/- 9%, whereas rDSPA alpha 1 at 100 nmol/kg only lowered alpha 2-antiplasmin significantly (by 29% +/- 6%). Compared with t-PA, rDSPA alpha 1 is the more potent and more clot selective (fibrin specific) thrombolytic agent. These results suggest that rDSPA alpha 1 may be safer and more efficacious than currently used thrombolytics.

Animals↗
PubMed1992

Allelic dimorphism in the human tissue-type plasminogen activator (TPA) gene as a result of an Alu insertion/deletion event.

Polymerase chain reaction and direct sequencing were used to investigate an amplified DNA fragment containing the suspected polymorphic site of all known intragenic restriction fragment length polymorphisms (RFLPs) within the human tissue-type plasminogen activator (TPA) gene. Sequence data obtained showed that these RFLPs were all generated by the presence or absence of one of the two Alu sequences located in intron h of the human TPA gene. Furthermore, one of the direct repeats flanking this Alu sequence was absent in the minor allele. In addition to indicating the presence of an Alu insertion in an ancestral human TPA gene, these findings suggest a slip-replication mechanism for the deletion of this Alu repeat, once inserted into the gene. As both alleles have been observed in similar frequencies among different ethnic groups, the insertion or subsequent deletion of this Alu sequence in the human TPA gene must have occurred early in human evolution.

Alleles↗
PubMed1992

Expression of high levels of human tissue plasminogen activator in yeast under the control of an inducible GAL promoter.

The human tissue plasminogen activator (h-tPA) cDNA was fused either with the leader sequence of the killer toxin of Kluyveromyces lactis or with the Saccharomyces diastaticus glucoamylase leader peptide and cloned in the yeast expression vector under the control of the inducible USAgal/CYC1 promoter. The recombinant tPA is produced in yeast as a single-chain glycosylated polypeptide of 66-72 kDa, which accumulates intracellularly associated with a membrane fraction. Using two-step fed-batch fermentation, a productivity up to 100 mg/l of active intracellular tPA was obtained.

Fermentation↗
PubMed1992

Tumor necrosis factor alpha increases antifibrinolytic activity of cultured human mesangial cells.

Tumor necrosis factor alpha (TNF alpha) is likely to exert a major influence in the pathogenesis of glomerulopathies. Besides its proinflammatory properties. TNF alpha interacts with cell growth and synthesis of components of the fibrinolytic system. In this study, we report the effects of recombinant human TNF alpha on the synthesis of tissue-type plasminogen activator (t-PA) and its inhibitor (PAI-1) by human mesangial cells in culture. We first demonstrate that TNF alpha binds specifically to a single class of high affinity receptors (Kd 5.10(-11) M; 1500 receptors/cell). TNF alpha has an antimitogenic effect on human mesangial cells since it decreased DNA synthesis, measured by 3H-thymidine incorporation, in a dose-dependent manner. Release of cytosolic LDH and incorporated 51Cr was not increased by 100 ng/ml TNF alpha as compared with control, indicating that this monokine is not cytotoxic for cultured human mesangial cells. Zymographic analysis and reverse fibrin autography disclosed a 120 kD t-PA-PAI-1 complex and a 50 kD free form of PAI-1 in the supernatants of both unstimulated and TNF-stimulated cells; PAI-1 was released in excess and free t-PA was not observed. TNF alpha (0 to 100 ng/ml) had no effect on t-PA synthesis, but enhanced PAI-1 release in a time- and dose-dependent manner (97% increase of PAI-1 synthesis after a 24 hour incubation). This effect was abolished by cycloheximide, suggesting that protein synthesis was required. Northern blot analysis showed that TNF alpha increased the steady-state PAI-1 mRNA levels in a time-dependent manner, with a maximal effect at two hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMed1992

Molecular cloning of human endothelin (ET) receptors ETA and ETB.

Complementary DNAs coding for two different endothelin (ET) receptors were isolated from a human lung cDNA library. DNA sequencing revealed that they corresponded to either the ET-1-selective receptor subtype originally identified in cows (ETA) or the nonselective subtype first found in rats (ETB). An open reading frame coding for a 427 (ETA) or a 442 (ETB) amino acid-long protein, with a transmembrane topology also found in other G protein-coupled receptors, was determined. Whereas the amino acid identity is about 90% between the characterized members of a given receptor subtype, with the best conserved parts being the hydrophobic transmembrane domains, less than 60% identity was found between the human A and B subtypes. Southern blot analysis of human genomic DNA revealed the existence of multiple hybridizing bands when using probes derived from the full-length ETA or ETB cDNAs. However, when shorter fragments were selected as probes, only one band remained detectable, which suggests the existence of a single-copy gene for each subtype of ET receptor.

Amino Acid Sequence↗
PubMed1992

Plasminogen activator inhibitor-1 deposition in the extracellular matrix of cultured human mesangial cells.

Human mesangial cells secrete tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1), the latter being secreted in large excess in vitro. We demonstrate that PAI-1 is a major component of the extracellular matrix of cultured human mesangial cells, where its deposition is dependent on cell density. By immunogold silver staining, epipolarization microscopy and dispersive X-ray spectrometry, we have shown that matrix-associated PAI-1 is synthesized by spreading human mesangial cells, as indicated by the time-dependent accumulation of PAI-1 and the inhibitory effect of cycloheximide. Furthermore, by in situ hybridization, PAI-1 mRNA was detected in cultured mesangial cells. t-PA is present inside the cells, or at the cell surface, but is never associated with the extracellular matrix. Exogenous t-PA can remove matrix-associated PAI-1 without affecting cell adhesion. A similar effect was obtained by addition of urokinase-type plasminogen activator (u-PA) but not with fibrinolysis unrelated enzymes. In conclusion, PAI-1 is synthesized by human cultured mesangial cells and is deposited in the extracellular matrix by nonconfluent cells, whereas less PAI-1 is seen between confluent cells. This can explain the absence of detectable PAI-1 in normal human kidney biopsies. t-PA released by mesangial cells can bind and detach matrix PAI-1.

Cells, Cultured↗
PubMed1991

The plasminogen activator family from the salivary gland of the vampire bat Desmodus rotundus: cloning and expression.

Complementary DNAs coding for four Desmodus rotundus salivary plasminogen activators (DSPAs) were isolated and characterized. The predicted amino acid sequences display structural features also found in tissue-type plasminogen activator. The largest forms (DSPA alpha 1 and -alpha 2) contain a signal peptide, a finger (F), an epidermal growth factor (EGF), a kringle, and a serine protease domain, whereas DSPA beta and -gamma lack the F and F-EGF domains, respectively. Additional differences between the four forms suggest that distinct genes code for the members of the DSPA family. Transfection of DSPA-encoding cDNAs, placed under the control of the simian virus 40 late promoter, into COS-1 cells resulted in the secretion of highly fibrin-dependent PAs.

Amino Acid Sequence↗