Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat astrocytes synthesize and secrete two types of plasminogen activators (PAs), tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA), whose functions are related to cell proliferation, migration, and differentiation during development. The regulation of PAs produced by brain astrocytes is poorly understood. In a previous report we demonstrated that t-PA and u-PA are each independently regulated by cAMP-dependent protein kinase and protein kinase-C. In the present study we examined the effects of three well characterized astrocyte mitogens, insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF), and platelet-derived growth factor (PDGF), on the PA activities produced and secreted by rat astrocytes in vitro. We found that IGF-I and EGF increase cell-associated total PA activity in astrocyte-conditioned medium (CM). The effects of both growth factors were dose and time dependent, and maximal stimulation was achieved after 72 h of treatment with the highest dose tested (100 nM). IGF-I stimulated the cell-associated PA activity more than the CM activity, whereas EGF showed an opposite pattern, suggesting that the secretion of PA is differentially modulated by IGF-I and EGF. PDGF had no effect on astrocyte PA activities at any dose or time point included in the study. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis/zymography showed type-specific changes in CM and cell-associated PA activity after growth factor treatment. IGF-I stimulated only t-PA, whereas EGF induced a marked increase in u-PA activity and a more limited increase in t-PA. PDGF did not modify either t-PA or u-PA activity. In summary, our results show that IGF-I and EGF each had different effects on PA activities, whereas PDGF had no effect. This diversity in the patterns of growth factor regulation of PAs suggests that the production of astrocyte PAs is not simply related to mitogenesis. More likely, astrocyte PAs are involved in a wide range of growth factor-mediated actions in the developing brain.
 ...
PMID:Differential regulation of astrocyte plasminogen activators by insulin-like growth factor-I and epidermal growth factor. 819 86

Vitamin D3, 1 alpha,25(OH)2D3, and its metabolites regulate the growth and differentiation of several cell types. Vitamin D3 and its analogue, calcipotriol (MC 903), inhibit the proliferation of cultured human and mouse keratinocytes and induce keratinocyte differentiation. Calcipotriol is effective in the treatment of psoriasis in which increased plasminogen activator activity has been reported. We analyzed therefore the effects of calcipotriol and vitamin D3 on the production of plasminogen activator (PA) activity in human keratinocytes and a mouse keratinocyte cell line. Caseinolysis-in-agarose assays indicated that vitamin D3 decreases total PA activity in both keratinocyte culture systems. Zymographic analyses of the medium indicated that the secreted activator was of the urokinase type (u-PA). A decrease was observed also in extracellular matrix and membrane-associated u-PA activity of vitamin D3 and calcipotriol treated cells. Immunoblotting analysis of the conditioned medium from human keratinocytes revealed a decrease in the u-PA protein levels. Accordingly, Northern hybridization analysis of the respective mRNAs indicated a rapid decrease in urokinase mRNA levels. Calcipotriol decreased u-PA activity also in the presence of inducers of u-PA activity like transforming growth factor-beta, epidermal growth factor, and phorbol-12-myristate-13-acetate. Calcipotriol also caused a decrease in tissue type PA (t-PA) activity of the keratinocytes. Most t-PA activity was associated with the extracellular matrices and cell membranes as revealed by zymographic analysis. Paradoxically, the secretion and deposition of the matrix of plasminogen activator inhibitor type 1 decreased in calcipotriol-treated cells. The results indicate that a major effect of vitamin D3 on cultured keratinocytes is a decrease of plasminogen activator activity.
 ...
PMID:Vitamin D3 and calcipotriol decrease extracellular plasminogen activator activity in cultured keratinocytes. 822 32

The fibrinolytic activity of low molecular weight (LMW) single-chain urokinase-type plasminogen activator (scu-PA) lacking the epidermal growth factor domain and the kringle domain was compared with the activity of high molecular weight (HMW) scu-PA. LMW scu-PA was 1-5 times less active than HMW scu-PA in a fibrin plate method, in a purified fibrin clot lysis assay and in a plasma clot lysis assay. Time course experiments in a chromogenic plasminogen activator assay suggested that LMW scu-PA was less sensitive to activation by plasmin than HMW scu-PA. This was confirmed in a scu-PA activation test, which showed that at a concentration of 40 IU/ml LMW scu-PA required a three-fold higher plasmin concentration for 50% activation in 20 min than did HMW scu-PA. Kinetic experiments in the presence of 0.1 M NaCl showed non-standard Michaelis-Menten kinetics for the activation by plasmin of both HMW and LMW scu-PA. In contrast, standard kinetics was observed at 0.15 M NaCl, showing a 2.6-fold lower catalytic efficiency for LMW scu-PA than for HMW scu-PA. It is concluded that the plasmin activation of LMW scu-PA is about three times slower than the activation of HMW scu-PA. This explains, at least partially, the lower fibrinolytic activity of LMW scu-PA in comparison with HMW scu-PA.
 ...
PMID:Comparison of the in vitro fibrinolytic activities of low and high molecular weight single-chain urokinase-type plasminogen activator. 825 53

In this paper, we investigated how epidermal growth factor (EGF) acts on growth and regulation of extracellular matrix components and their degenerative enzymes in uterine cervical adenocarcinoma cells in vitro. Effects of EGF on cell growth, DNA synthesis, and laminin, collagen IV, and tissue plasminogen activator (t-PA) production of human uterine cervical adenocarcinoma cell line OMC-4 were examined, together with the characteristics of its EGF receptors. Scatchard plot of EGF binding to OMC-4 indicated two classes of binding sites with a dissociation constant of 170 pM and 510 pM. The total binding sites were 1.6 x 10(5)sites/cell. The number of OMC-4 cells did not increase in the presence of EGF, whereas 3H-thymidine incorporation was inhibited by EGF at concentrations of 1 and 10 nM. The production of laminin and collagen IV by OMC-4 cells was inhibited by EGF, whereas that of t-PA was significantly promoted at the physiological concentration of 0.1 nM. These results suggest that EGF is closely associated with regulation of proliferation and extracellular matrix degradation of uterine cervical adenocarcinoma cells.
 ...
PMID:Characterization of epidermal growth factor (EGF) receptor and biological effect of EGF on human uterine cervical adenocarcinoma cell line OMC-4. 829 19

Murine embryonal carcinoma cells do not express detectable cell-surface epidermal growth factor receptors (EGF-R) but after 2 days of differentiation induced by retinoic acid (RA) increasingly express mRNA and protein encoded by the EGF receptor gene (Joh et al., Cell Growth and Differentiation 3, 315, 1992). The effect on morphology, growth, and differentiation of the introduction of expression vectors that produce either a truncated, kinase-negative mouse EGF receptor or an antisense mRNA was studied in P19 embryonal carcinoma (EC) cells before and after differentiation. The presence of either construct should lead to the reduction of EGF-R expression by either the dominant negative effects of a truncated protein or the inhibition of endogenous EGF-R mRNA production/translation by complementary RNA, respectively. Cells were cotransfected with the bacterial neomycin resistance gene and constitutively expressing clones were selected with G418. The cytomegalovirus LTR promoter/enhancer was found to be very inefficiently activated in P19 EC cells. After RA addition, changes in gene expression included induction of both the exogenous truncated constructs and endogenous EGF-R. Differentiation was gauged by the expression of tissue-type plasminogen activator and intermediate filament protein markers of neural tissues, as well as EGF-R. The expression of 120-kDa truncated EGF-Rs was high in four clones, but all 10 clones examined had diminished abilities to differentiate after RA induction compared to four control cell lines. Similarly, the majority of antisense transfected clones was unable to differentiate normally. The results indicate that the reduced expression of EGF-Rs in differentiating EC cells inhibits the rate, frequency, and extent of differentiation after RA induction. We conclude that the expression of EGF-Rs plays a role in the stimulation of differentiation and we speculate that the mechanism involves the tyrosine kinase activity of the receptor.
 ...
PMID:Inhibition of differentiation in P19 embryonal carcinoma cells by the expression of vectors encoding truncated or antisense EGF receptor. 836 61

uK2t-PA is a hybrid plasminogen activator in which the epidermal growth factor-like domain of the urokinase-type plasminogen activator precedes the kringle 2 and catalytic domains of tissue-type plasminogen activator. The molecules are expressed in Chinese hamster ovary cells in two variant forms, a type II form in which only the protease domain is glycosylated, and a type I form in which both the kringle 2 and the protease domains carry N-acetyllactosamine type glycans. The two forms differed slightly in their affinity for fibrin and fibrinogen, which allowed their separation, but the stimulation of plasminogen activation of the type II form by fibrin was up to eight-fold lower than that of the type II form. The sensitivity to fibrin could be restored by treatment of the type I form with N-glycanase or sialidase. Enzymatic activity vs low molecular weight substrates was not influenced by the glycosylation of kringle 2.
 ...
PMID:Functional effects of kringle 2 glycosylation in a hybrid plasminogen activator. 838 98

Protein-protein interactions can be guided by contacts between surface loops within proteins. We therefore investigated the hypothesis that novel protein-protein interactions could be created using a strategy of "loop grafting" in which the amino acid sequence of a biologically active, flexible loop on one protein is used to replace a surface loop present on an unrelated protein. To test this hypothesis we replaced a surface loop within an epidermal growth factor module with the complementarity-determining region of a monoclonal antibody. Specifically, the HCDR3 from Fab-9, an antibody selected to bind the beta 3-integrins with nanomolar affinity (Smith, J. W., Hu, D., Satterthwait, A., Pinz-Sweeney, S., and Barbas, C. F., III (1994) J. Biol. Chem. 269, 32788-32795), was grafted into the epidermal growth factor-like module of human tissue-type plasminogen activator (t-PA). The resulting variant of t-PA bound to the platelet integrin alpha IIb beta 3 with nanomolar affinity, retained full enzymatic activity, and was stimulated normally by the physiological co-factor fibrin. Binding of the novel variant of t-PA to integrin alpha IIb beta 3 was dependent on the presence of divalent cations and was inhibited by an RGD-containing peptide, demonstrating that, like the donor antibody, the novel t-PA binds specifically to the ligand-binding site of the integrin. These findings suggest that surface loops within protein modules can, at least in some cases, be interchangeable and that phage display can be combined with loop grafting to direct proteins, at high affinity, to selected targets. In principle, these targets could include not only other proteins but also peptides, nucleic acids, carbohydrates, lipids, or even uncharacterized markers of specific cell types, tissues, or viruses.
 ...
PMID:Protein loop grafting to construct a variant of tissue-type plasminogen activator that binds platelet integrin alpha IIb beta 3. 853 Apr 79

The fibrin-specific thrombolyticum tissue-type plasminogen activator (t-PA) has proven to be a potent drug in several clinical trials, but its clinical application is complicated by the rapid clearance of t-PA from the circulation. The rapid plasma clearance of t-PA results from the uptake of t-PA in the liver. t-PA consists of several domains which may be involved in the interaction with the liver. Three domain-deletion mutants, which were produced by the use of a cassette gene system, were studied in vivo and in vitro for their capacity to bind to the various types of rat liver cells. The three mutants lacked, in comparison to control t-PA, the epidermal growth factor (G) domain, the finger (F) domain or the G domain plus the first kringle (K1). The plasma clearance of the three mutants was slower than that of control t-PA. The slower plasma clearance resulted from a decreased liver uptake: 50 and 80% for t-PA mutants and control t-PA respectively. It was found that the K1 domain was of major importance for the uptake of t-PA by liver endothelial cells in vivo and in vitro. The high-affinity binding of t-PA (and t-PA mutants) to parenchymal liver cells depended largely on the presence of the G domain. Other domain(s), like the F, K2 or protease domain, may be responsible for low-affinity, t-PA-specific binding to rat parenchymal liver cells.
 ...
PMID:Interaction of mutants of tissue-type plasminogen activator with liver cells: effect of domain deletions. 861 Nov 54

DSPAalpha1 (Desmodus rotundus salivary plasminogen activator), a plasminogen activator from the saliva of the vampire bat Desmodus rotundus, is an effective thrombolytic agent. An unusual type of posttranslational modification, in which L-fucose is O-glycosidically linked to threonine 61 in the epidermal growth factor domain was found for natural DSPAalpha1 and its recombinant form isolated from Chinese hamster ovary cells. In the present study a combination of carbohydrate and amino acid composition analysis, amino acid sequencing, and mass spectrometry revealed that the L-fucose is bound to residues 56-68 of DSPAalpha1. The amino acid sequence of this glycosylation site agreed with the suggested consensus sequence Cys-Xaa-Xaa-Gly-Gly-Ser/Thr-Cys described for other proteins. Anew strategy for the identification of the modified amino acid was established. Direct evidence for the occurrence of fucosyl-threonine was obtained by mass spectrometry after digestion of the glycopeptide with a mixture of peptidases. On the basis of these results, DSPAalpha1 is a suitable model for studying the influence of O-fucosylation on clearance rates, particularly in comparative studies with the identically fucosylated and structurally related tissue plasminogen activator.
 ...
PMID:O-linked L-fucose is present in Desmodus rotundus salivary plasminogen activator. 863 61

Angiogenesis of capillary endothelial cells includes at least four sequential cellular responses: digestion of basement membrane, migration, proliferation, and differentiation. To study differentiation of endothelial cells, we established a brain capillary endothelial cell line from H-2Kb-tsA58 transgenic mice. These cells are stable at 33 degrees C and display endothelial cell-specific characters, such as expression of von Willebrand factor and binding sites for the lectin Bandeiraea simplifolia, and uptake of acetylated-low density lipoprotein. We measured the effects of a panel of growth factors on cellular responses. A number of factors, such as hepatocyte growth factor, vascular endothelial growth factor, and platelet-derived growth factor (PDGF)-AA failed to induce biological responses. PDGF-BB, epidermal growth factor, and acidic and basic fibroblast growth factor (FGF) induced proliferation of the cells. Of all the factors tested, only acidic FGF and basic FGF induced differentiation of the cells, visualized as the formation of tube-like structures of cells grown in three-dimensional collagen gels. All factors were also analyzed for their effects on plasminogen activator (PA)-induction and migration of the cells. Transfected cells, expressing a chimeric receptor, composed of the extracellular part from the PDGF alpha-receptor and the intracellular part from FGF receptor-1, responded to PDGF-AA treatment with plasminogen activator induction, migration, proliferation, and tube formation in collagen. These results indicate that FGF receptor-1 coupled to signal transduction pathways, leading to differentiation. This novel cell model offers the potential of detailed dissection of signal transduction pathways involved in the differentiation of endothelial cells.
 ...
PMID:Fibroblast growth factor receptor 1-induced differentiation of endothelial cell line established from tsA58 large T transgenic mice. 883 68


<< Previous 1 2 3 4 5 6 7 8 9 10