Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In contrast to fibroblasts, the exposure of G0/G1-arrested J774 cells, a murine macrophage-like tumor cell line, with either active or esterolytically inactive diisopropyl phosphorofluoridate-conjugated alpha-thrombin (the enzymatically active form of thrombin, EC 3.4.21.5) results in a mitogenic response as measured by increased [3H]thymidine incorporation. This response to thrombin is optimal at 10 nM and is specifically blocked by hirudin, a high-affinity thrombin inhibitor. When prethrombin 1 [a single-chain prothrombin derivative lacking fragment 1, resulting from the action of thrombin on prothrombin] is cleaved with cyanogen bromide, a fragment (peptide CB67-129) is produced that, like the parent thrombin molecule, is mitogenic for J774 cells but not for fibroblasts. Limited tryptic digests of this fragment retain the ability to stimulate macrophages--a function that can be mimicked by a synthetic tetradecapeptide homologue of CB67-129 (representing residues 367-380 of the human thrombin B chain sequence) but not by any of a series of well-known growth promoters, including platelet-derived growth factor, epidermal growth factor, nerve growth factor, and fibroblast epidermal growth factor, nerve growth factor, and fibroblast growth factor. The mitogenic effects of this peptide are not limited to J774 cells but can be expressed in other macrophage-like tumor cell lines, including P388D1, RAW, and PU5. In addition to increased [3H]thymidine incorporation, the synthetic B chain peptide stimulates cell proliferation as evidenced by a dose-dependent increase in total protein per culture well and cell number. We conclude that the thrombin molecule contains a macrophage growth factor domain that is separate and distinct from its active center. Thus, thrombin, in addition to its major role in hemostasis and thrombosis, may also have important functions in such basic processes as the inflammatory response and monocytopoiesis.
...
PMID:Identification of a thrombin sequence with growth factor activity on macrophages. 345 76

A specific radioimmunoassay for type beta transforming growth factor (TGF-beta) was developed and used to show that human platelets treated with thrombin release TGF-beta as a consequence of degranulation. The thrombin concentrations required to induce release of TGF-beta parallel those concentrations that release the alpha-granule marker, beta-thromboglobulin. Related studies showed that TGF-beta acts on early passage, explant cultures of bovine aortic smooth muscle cells by inhibiting the effect of mitogens on proliferation of subconfluent cell monolayers yet synergizing with mitogens to stimulate growth of the same cells when cultured in soft agar. The results show that primary cultures of bovine aortic smooth muscle cells and established normal rat kidney cells behave similarly with regard to TGF-beta action. Moreover, the data suggest that platelet-mediated proliferation of aortic smooth muscle cells in vivo may not result solely from the stimulatory effect of platelet-derived growth factor (PDGF), but rather from an interaction of platelet factors which has the intrinsic ability to limit as well as stimulate mitosis.
...
PMID:Type beta transforming growth factor in human platelets: release during platelet degranulation and action on vascular smooth muscle cells. 345 14

Bovine basic fibroblast growth factor (bFGF) is a potent mitogen isolated from bovine pituitary glands and brain. The addition of homogeneous bFGF to primary cultures of rat cerebral cortical neurons markedly enhances cell survival and elaboration of neurites. These effects are dose-dependent, with optimal stimulation occurring at a concentration of 500 pg/ml. Maintenance of survival and neurite outgrowth require the continuous presence of bFGF. Other growth factors, such as thrombin, platelet-derived growth factor, beta nerve growth factor, and interleukin 2, have no effect on neuronal survival or process formation. Although the cellular site(s) of bFGF synthesis has not yet been established, these results suggest that bFGF may function as a neurotrophic agent in the central nervous system.
...
PMID:Basic fibroblast growth factor supports the survival of cerebral cortical neurons in primary culture. 346 83

Heparin and related glycosaminoglycans are potent inhibitors of both in vivo and in vitro smooth muscle cell (SMC) proliferation. We have found that epidermal growth factor (EGF) reverses the antiproliferative effects of heparin. Other known SMC mitogens, including platelet-derived growth factor (PDGF), insulin-like growth factor-1 (IGF-1), and thrombin, were unable to prevent heparin action. The EGF specificity was further demonstrated by developing a biological growth assay in which EGF or PDGF, at concentrations as low as 1 ng/ml, stimulated SMC growth in the absence of other serum components. Under these conditions, EGF, but not PDGF, suppressed heparin inhibition as well. The ability of EGF to reverse heparin inhibition was only observed when mitogen and glycosaminoglycan were added to SMC at similar times. If SMC were pretreated with heparin for 48 hours prior to EGF addition, the protective effects of EGF were lost. Heparin did not directly prevent 125I-EGF or platelet-derived EGF-like peptides from binding to the EGF receptor on SMC. However, cultures that were pretreated with heparin for 48 hours bound 49% less 125I-EGF than cultures that had been pretreated with the mucopolysaccharide for only 2 hours or that had not been preexposed to heparin. In previous studies, we have established that heparin exerts its maximal inhibitory activity after a 48-hour treatment of SMC (Reilly et al. 1986). Taken together, these data suggest that heparin may exert its antiproliferative potential by slowly and specifically altering SMC response to EGF-like mitogens of platelet origin.
...
PMID:Antiproliferative effects of heparin on vascular smooth muscle cells are reversed by epidermal growth factor. 349 40

Intravenous injection of human or mouse serum or platelet material secreted from appropriately stimulated platelets ("releasate") together with antigen alleviates the immunosuppression in SJL/J mice induced by injection of irradiated lymphoma cells or in (CB6)F1 mice induced by injection of concanavalin A. We now report that injection of releasate from 10(6) human platelets restores plaque-forming cells to the unsuppressed number; greater amounts increase responses further. Immunoregulatory activity is released from platelets exposed to thrombin in parallel with other alpha-granule components. Heparin-agarose absorbs activity. Purified platelet factor 4 (PF4) has activity; beta-thromboglobulin and platelet-derived growth factor have little or none. Activity in serum is neutralized by goat anti-human PF4. An enzymatic step is necessary for production of immunoregulatory activity. Releasates boiled immediately after platelet aggregation with 250 nM A23187 or those produced by adding A23187 in the presence of 100 microM serine protease inhibitor (p-amidinophenyl)methanesulfonyl fluoride (APMSF) are ineffective, whereas releasates boiled or mixed with APMSF after incubation for 60 min are active. Activity is generated by incubating a mixture of heparin-absorbed releasate (as enzyme source) and heparin-agarose eluate of releasate made in the presence of APMSF (as substrate source). The enzymatic step does not alter the heparin-neutralizing activity of PF4. Apparently a secreted platelet protease converts PF4 to a form with immunoregulatory activity.
...
PMID:Protease-induced immunoregulatory activity of platelet factor 4. 351 62

A growth factor (HGF) stimulating DNA synthesis of adult rat hepatocytes in primary culture was found in rat platelets. HGF was purified from rat platelets to homogeneity by a three-step procedure: stimulation of its release from platelets by thrombin, cation-exchanger fast protein liquid chromatography on a Mono S column, and heparin-Sepharose chromatography. HGF was clearly distinguishable from the platelet-derived growth factor (PDGF) by fast protein liquid chromatography. HGF was a heat- and acid-labile cationic protein that was inactivated by reduction with dithiothreitol. Its molecular mass was estimated to be 27 kDa by NaDodSO4/PAGE and its amino acid composition was very different from that of PDGF. The purified HGF stimulated DNA synthesis in adult rat hepatocytes at 2 ng/ml and was maximally effective at 20 ng/ml; its effect was additive or synergistic with those of insulin and EGF, depending on their combinations. HGF did not stimulate DNA synthesis of Swiss 3T3 cells, while PDGF did not stimulate that of hepatocytes. Thus, HGF showed clearly different cell specificity from PDGF in its growth-promoting activities. These findings indicate that HGF is a growth factor in platelets for mature hepatocytes.
...
PMID:Purification and characterization of a growth factor from rat platelets for mature parenchymal hepatocytes in primary cultures. 352 86

Cultured endothelial cells secrete a platelet-derived growth factor-like molecule (PDGFc). We examined the effects of purified human alpha-thrombin on the production of PDGFc in cultures of human umbilical vein endothelial cells (HUVE) using a specific radioreceptor assay for PDGF. Addition of physiologically relevant concentrations of alpha-thrombin (0.1 to 10 U/ml) induced a time- and dose-dependent increase in the release of PDGFc into the culture medium. Significant stimulation of PDGFc release was observed as early as 1.5 h after addition of alpha-thrombin (10 U/ml) with a 4.9 +/- 1.1 fold increase at 24 h (mean +/- SEM of nine experiments, P less than 0.01). alpha-Thrombin treatment of HUVE did not affect cell viability as assessed by trypan blue dye exclusion. The receptor binding of PDGFc secreted by HUVE in response to alpha-thrombin was inhibited by monospecific antibody to purified human PDGF indicating that the molecule(s) is closely related to PDGF. alpha-Thrombin inactivated with diisopropylfluorophosphate was without stimulatory effect. Lysis of HUVE by repeated cycles of freeze/thaw released minimal PDGFc (less than 0.3 ng per 10(6) cells) compared to levels of PDGFc released into supernatant medium in response to alpha-thrombin (greater than 5.0 ng per 10(6) cells after a 24-h incubation with 10 U/ml alpha-thrombin). Moreover, incubation of freeze/thaw lysates of HUVE with alpha-thrombin failed to release PDGFc. Over a 3-h time course, however, alpha-thrombin-induced secretion of PDGFc was not prevented by cycloheximide. We conclude that alpha-thrombin induces secretion of PDGFc from HUVE by a nonlytic mechanism requiring the serine esterase activity of the enzyme. Although this effect does not initially require de novo protein synthesis, it does require cell-mediated conversion of PDGFc from an inactive to an active form.
...
PMID:Alpha-thrombin induces release of platelet-derived growth factor-like molecule(s) by cultured human endothelial cells. 374 65

Human arterial endothelial cells were cultured in vitro for up to 40 cumulative population doublings. Culture conditions similar to those required for long-term propagation of human umbilical vein endothelial cells were employed. These included fibronectin-coated culture vessels, 5 to 20% fetal bovine serum, endothelial cell growth factor, and heparin. Thoracic aorta endothelial cells were larger than iliac artery endothelial cells. Both cell types stained positively for Factor VIII antigen by immunofluorescence. A decrease in confluent density as a function of population doubling level was correlated with the appearance of large, senescent cells in the cultures. Serum growth factors to which the arterial endothelial cells responded included insulin, transferrin, epidermal growth factor, thrombin, and somatomedins. The effect of thrombin did not require the availability of the active site of the protease. The effect of the somatomedins was only seen in the presence of heparin. Neither platelet-derived growth factor nor hydrocortisone induced arterial endothelial cell proliferation. These growth factor responses were also observed on the part of human umbilical vein endothelial cells.
...
PMID:Growth factor responses of human arterial endothelial cells in vitro. 375 96

We have investigated the epidermal growth factor (EGF)-stimulated tyrosine-specific protein kinase activity in quiescent cultures of diploid human fibroblasts that have a well characterized mitogenic response to EGF. We developed a method of permeabilizing cells with digitonin or other agents that permitted the rapid labeling of cellular proteins with exogenously added [gamma-32P]ATP while allowing only about 25% of marker cytosolic enzymes to escape from the cells. When phosphatases were inhibited with zinc and vanadate, EGF induced up to 8-fold stimulation of the incorporation of radioactivity from [gamma-32P]ATP into a 35-kDa band on sodium dodecyl sulfate gels. Alkali treatment of gels showed that EGF stimulated the phosphorylation of bands with apparent molecular masses of 170, 45, 35, 26, 22, and 21 kDa. Phosphoamino acid analysis was performed on the 170- and 35-kDa bands and revealed that the EGF-stimulated phosphorylation was on tyrosyl residues. The 35-kDa band was resolved into four spots by two-dimensional gel electrophoresis. The most acidic form was the most prominent and it was precipitated by an antiserum against a 35-kDa protein from A-431 cells; heretofore, this protein has only been reported to be phosphorylated in an EGF-dependent manner by A-431 membranes in vitro (Fava, R. A., and Cohen, S. (1984) J. Biol. Chem. 259, 2636-2645). This antiserum also precipitated a 35-kDa phospho-protein from extracts of intact [32P]orthophosphate-labeled fibroblasts which was phosphorylated on tyrosine in an EGF-dependent manner. None of the forms of the 35-kDa phosphoproteins labeled in permeabilized cells were immunologically related to the 34-kDa protein that is a substrate for the tyrosyl kinase encoded by Rous sarcoma virus. Other mitogens (serum, insulin, platelet-derived growth factor, and thrombin) did not detectably stimulate phosphorylation in permeabilized cells.
...
PMID:Epidermal growth factor stimulates tyrosine phosphorylation of specific proteins in permeabilized human fibroblasts. 387 22

We have investigated the effect of topically applied mitogenic preparations on the healing of full-thickness skin wounds in the Syrian hamster. In an attempt to accelerate the healing process, dexamethasone and insulin, platelet-derived growth factor, fibroblast growth factor, thrombin, defined medium F for fibroblasts, liver cell supernatant, epidermal growth factor, and colostrum were applied to the wounds. These mitogens had no significant influence on the rate of wound contraction or on the time to complete healing in full-thickness, noncompromised skin wounds in this animal model.
...
PMID:Growth factors and wound healing in the hamster. 389 6


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

---