Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.7 (plasmin)
 9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activation of latent transforming growth factor beta (LTGF-beta) normally seen in cocultures of bovine aortic endothelial and bovine smooth muscle cells can be inhibited by coculturing the cells with either mannose 6-phosphate (Man-6-P) or antibodies directed against the cation-independent Man-6-P/insulin-like growth factor type II receptor (anti-Man-6-PR). This result was established by measuring the ability of coculture conditioned medium (formed with or without Man-6-P or anti-Man-6-PR) to suppress bovine aortic endothelial cell migration and protease production, activities previously shown to be related to transforming growth factor beta activity. The inhibition by Man-6-P is dose dependent, with maximal inhibition seen at 100 microM and is specific because mannose 1-phosphate and glucose 6-phosphate do not interfere with activation of LTGF-beta. The inhibitory effect of anti-Man-6-PR is also specific and dose dependent; maximal inhibition of activation occurs at 400 micrograms/ml. Control experiments indicate that Man-6-P and anti-Man-6-PR do not interfere with the basal level of migration of bovine aortic endothelial cells, the migration observed when exogenous transforming growth factor beta is added, the activation of transforming growth factor beta by plasmin or transient acidification, and the release of LTGF-beta. Thus, binding to the cation-independent Man-6-P/insulin-like growth factor type II receptor appears to be a requirement for activation of LTGF-beta.
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PMID:Cellular activation of latent transforming growth factor beta requires binding to the cation-independent mannose 6-phosphate/insulin-like growth factor type II receptor. 184 48

Transforming growth factor-beta (TGF-beta) is secreted by most cells as a biologically inactive complex, called the large latent TGF-beta complex. The complex is comprised of latent TGF-beta binding protein (LTBP) and latent TGF-beta, which is mature TGF-beta associated noncovalently with its amino-terminal propeptides. LTBP is disulfide-linked to the amino-terminal propeptide of latent TGF-beta. Active TGF-beta is generated by release of TGF-beta from the complex. Generation of active TGF-beta by macrophages has been reported, but the activation mechanism has not been described. Latent TGF-beta activation by macrophages was characterized using serum-free cultures of resident and thioglycollate-elicited murine peritoneal macrophages that were either unstimulated or LPS-stimulated in vitro. Serum-free conditioned medium was assayed for TGF-beta using a quantitative luciferase-based bioassay. LPS-stimulated thioglycollate-elicited macrophages activated endogenous latent TGF-beta, whereas non-LPS-stimulated thioglycollate-elicited and resident macrophages generated undetectable levels of TGF-beta. Latent TGF-beta activation required plasmin and urokinase (uPA), uPA binding to the uPA receptor, interaction with the cation-independent mannose 6-phosphate/insulin-like growth factor type II receptor, tissue type II transglutaminase, and LTBP. A time-course analysis of latent TGF-beta activation revealed that maximal TGF-beta was generated after 24 h (25 +/- 5 pg/ml). TGF-beta formed within the initial 24 h modulated the plasminogen activator system by down-regulating uPA, suggesting that TGF-beta temporally modulated its own formation by regulating cell-associated uPA.
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PMID:Characterization of latent TGF-beta activation by murine peritoneal macrophages. 763 10

High levels of the cell growth inhibitor transforming growth factor-beta1 (TGF-beta1) are often found in a variety of human cancers. However, the physiological significance of this overexpression depends on the availability of the biologically active form of TGF-beta1 within the extracellular matrix of the tumor microenvironment. To determine the expression and activation status of TGF-beta1 in chemically induced tumors, 6-wk-old A/J mice were injected intraperitoneally with either azoxymethane (AOM) (10 mg/kg body weight, once a week for 6 wk) or normal saline solution, and colon tumors were isolated 24 wk following the last injection. An enzyme-linked immunosorbent assay for TGF-beta1 revealed a significant increase (1.7-fold, P < 0.05) in total TGF-beta1 protein in tumors. Interestingly, while 80% of the total TGF-beta1 in the control colon tissues was in the active form, only 50% was found to be active in tumors. Together with our earlier observations that TGF-beta1 mRNA levels are unchanged in A/J tumors, these data further support a mechanism whereby elevated TGF-beta1 levels result from a defective activation and turnover of this protein. Because plasmin is known to be a major activator of TGF-beta1 in vivo, we hypothesized that reduced plasmin activity may be responsible for the observed dysregulation of TGF-beta1 processing in these behaviorally benign tumors. With a fluorogenic peptide substrate for serine proteases, a deficiency in plasmin activity was found in the tumors. Furthermore, semiquantitative reverse transcription (RT)-polymerase chain reaction (PCR) analysis of a panel of genes involved in the plasminogen activation system, including plasminogen activator inhibitor-1 (PAI-1), urokinase-plasminogen activator (u-PA), and urokinase-receptor (u-PAR-1), demonstrated a significant upregulation (approximately fourfold to sixfold, P < 0.05) in the expression of each of these genes in the tumor tissue. In addition, no significant changes were observed in the expression levels of thrombospondin-1 (TSP-1) and insulin-like growth factor type II receptor (IGF-IIR), which also mediate the activation of latent TGF-beta1. To gain further insight into the functionality of the TGF-beta1 pathway, cDNA microarrays were performed and the expression levels of a panel of 21 TGF-beta1-specific target genes were determined in AOM-induced tumors that overexpress the ligand. A significant dysregulation in the expression of each of these targets was observed, providing evidence of aberrant TGF-beta1 signaling in tumors. Overall, the present study demonstrates a very low plasmin activity in A/J colon tumors, possibly as a result of the potent inhibitory effect of PAI-1 on the plasminogen activation cascade. The observed deficiency in plasmin activity may not be sufficiently compensated for by other mechanisms of latent TGF-beta1 activation, including TSP-1 and IGF-IIR, thereby resulting in a decreased fraction of the biologically active form of TGF-beta1 and subsequent aberration in TGF-beta1-specific gene regulation in A/J tumors.
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PMID:Defective processing of the transforming growth factor-beta1 in azoxymethane-induced mouse colon tumors. 1272 Mar