Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Urokinase-type plasminogen activator (uPA) is a key serine protease involved in invasion and metastasis. We had shown that overproduction of uPA in tumor cells is controlled by a phospholipase D-protein kinase C-dependent pathway. Now we studied whether other signaling pathways participate in the regulation of constitutive uPA and metalloproteinase (MMP) overproduction in tumor cells. Staurosporine, a protein kinase inhibitor, stimulated uPA and MMP-9 secretion as measured by radial caseinolysis, zymography and Western blotting. Genistein, a specific tyrosine kinase inhibitor, reduced the constitutive and staurosporine-induced uPA and MMP-9 secretion. Interestingly, the phosphatase inhibitor vanadate stimulated uPA secretion. Verapamil, a calcium channel blocker, inhibited both endogenous and PMA-stimulated secretion of uPA but was unable to inhibit staurosporine-induced secretion. The alcohol n-butanol, a phospholipase D and protein kinase C inhibitor, besides inhibiting constitutive uPA secretion, blocked staurosporine-induced secretion. Our results suggest that constitutive and staurosporine-induced uPA and MMP-9 secretion by LM3 murine mammary tumor cells is controlled by an endogenous tyrosine kinase pathway and probably involves protein phosphatases. In addition, the staurosporine-induced signal regulating urokinase secretion is independent of extracellular calcium but dependent on phospholipase D.
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PMID:Secretion of urokinase and metalloproteinase-9 induced by staurosporine is dependent on a tyrosine kinase pathway in mammary tumor cells. 957 73

Overproduction of urokinase-type plasminogen activator (uPA) and metalloproteases (MMPs) is strongly correlated with tumorigenicity and with invasive and metastatic phenotypes of human and experimental tumors. We demonstrated previously that overproduction of uPA in tumor cells is mediated by a phospholipase D (PLD)- and protein kinase C-dependent mechanism. The oncogenic stimulus of v-Src and v-Ras results in the activation of PLD, which is dependent upon the monomeric GTPase RalA. We have therefore investigated whether RalA plays a role in uPA and MMP overproduction that is observed in response to oncogenic signals. We report here that NIH3T3 cells transformed by both v-Src and v-Ras, constitutively overproduce uPA and that expression of a dominant negative RalA mutant (S28N) blocks overproduction of uPA in both the v-Src-and v-Ras-transformed cells. v-Src and v-Ras also induced an upregulation of the activity of MMP-2 and MMP-9 as detected by zymograms, however only the v-Src induction correlated with MMP protein levels detected by Western blot analysis. The dominant negative RalA mutant blocked increased MMP-2 and 9 overproduction induced by v-Src, but not the increased activity of MMP-2 and 9 induced by v-Ras. And, consistent with a role for the RalA/PLD pathway in mitogenesis and tumor development, the dominant negative RalA mutant completely blocked tumor formation by v-Src- and v-Ras-transformed NIH3T3 cells injected subcutaneously in syngeneic mice. The data presented here implicate RalA and PLD as signaling mediators for tumor formation and protease production by transformed cells.
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PMID:RalA requirement for v-Src- and v-Ras-induced tumorigenicity and overproduction of urokinase-type plasminogen activator: involvement of metalloproteases. 1046 19

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is a highly specific enzyme whose only known substrate is the GPI anchor of cell surface proteins. GPI-PLD measurements, however, are technically difficult since the enzyme is expressed at low levels in cells and tissues, and serum contains large amounts of inactive, latent GPI-PLD interfering with protein-based assays. We have therefore developed a semi-quantitative RT-PCR method to measure mRNA expression of all known GPI-PLD isoforms in cells and tissues. In human ovarian cancer cell lines, GPI-PLD mRNA expression correlated with GPI-PLD enzyme activity and with the shedding of the GPI-anchored tumor and prognostic markers, urokinase receptor and CA125, from the cell surface. This supports a potential role for this enzyme in the generation of circulating prognostic markers in malignant tumors. Similarly, in human epithelial cells of the skin, GPI-PLD mRNA expression increased with tumor progression. Whereas normal keratinocytes did not express significant amounts of GPI-PLD mRNA, expression was dramatically induced by serum in immortalized HaCaT keratinocytes and constitutively high and independent of serum in tumorigenic A431 epidermoid carcinoma cells. In addition, GPI-PLD expression was significantly increased in highly malignant. H-ras-transfected murine bladder carcinoma cells as compared to the low malignant, non-transfected parental cells. The competitive RT-PCR described here represents the first quantitative assay specific for cellular GPI-PLD isoforms, and our in vitro analyses suggest that GPI-PLD expression might be associated with tumor malignancy.
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PMID:GPI-specific phospholipase D mRNA expression in tumor cells of different malignancy. 1209 Apr 69

Lysophosphatidic acid (LPA) is an important intercellular signaling molecule involved in a myriad of biological responses. Elevated concentrations of LPA are present in the ascites and plasma of ovarian cancer patients suggesting a role for LPA in the pathophysiology of ovarian cancer. We have demonstrated previously that oleoyl (18:1) LPA at concentrations present in ascites induces the secretion of urokinase plasminogen activator (uPA) from ovarian cancer cells, possibly linking LPA to cellular invasion. In this study we sought to elucidate which signaling pathway(s) are involved in LPA-mediated secretion of uPA from ovarian cancer cells. Specific inhibitors were utilized to determine if interference with the p38(MAPK), p42/44(MAPK), and PI3K pathways functionally blocked LPA-mediated uPA secretion. LPA stimulation of ovarian cancer cells markedly increased the phosphorylation and activity of p38(MAPK), p42/p44(MAPK), and PI3K. Both tyrosine phosphorylation and Src kinase activity were required for optimal activation of signaling by LPA including phosphorylation of p38(MAPK). Inhibition of p38(MAPK) signaling by SB202190 completely abrogated LPA-induced uPA secretion, while inhibition of the p42/44(MAPK) or PI3K pathways with PD98059 or wortmannin and LY294002, respectively, decreased but did not completely block uPA secretion. In contrast, inhibitors of phospholipase D or the p70S6 kinase pathway did not alter LPA-induced uPA secretion. Further, tyrosine phosphorylation and functional Src were required for optimal uPA secretion. Finally, LPA induces uPA secretion from ovarian cancer cells predominantly through the LPA2 receptor, with LPA3 contributing to this process. These results indicate that the p38(MAPK) signaling pathway is required for optimal LPA-dependent uPA secretion from ovarian cancer cells.
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PMID:Lysophosphatidic acid induction of urokinase plasminogen activator secretion requires activation of the p38MAPK pathway. 1761 2

The small G-protein ADP-ribosylation factor 6 (Arf6) belongs to the Ras GTPases superfamily and is mostly known for its actin remodeling functions and involvement in the processes of plasma membrane reorganization and vesicular transport. The majority of data indicates that Arf6 contributes to cancer progression through activation of cell motility and invasion. Alternatively, we found that the expression of a wild-type or a constitutively active Arf6 does not influence tumor cell motility and invasion but instead significantly stimulates cell proliferation and activates phospholipase D (PLD). Conversely the expression of a mutant Arf6 (Arf6N48I), that is, unable to interact with PLD has no effect on proliferation but promotes motility, invasion, and matrix degradation by uPA extracellular proteinase. Studying the mechanisms of Arf6-dependent stimulation of cell proliferation, we found some signaling pathways contributing to Arf6 promitogenic activity. Namely, we showed that Arf6 in a PLD-mTORC1-dependent manner activates S6K1 kinase, a well-known regulator of mitogen-stimulated translation initiation. Furthermore, we demonstrated an Arf6-dependent phosphorylation of mTORC1 downstream targets, 4E-BP1 and ribosomal S6 protein, confirming an existence of Arf6-PLD-mTORC1-S6K1/4E-BP1 signaling pathway and also demonstrated its impact on proliferation stimulation. Next, we found that Arf6 activation potentiates Erk1/2 and p38MAP kinases phosphorylation. Surprisingly, p38 opposite to Erk1/2 significantly contributes to Arf6-dependent proliferation increase promoting S6 ribosomal protein phosphorylation at Ser235/236 residues. Therefore, we demonstrated Arf6 proliferation stimulating activity and revealed PLD-mTORC1 and p38MAP kinase as Arf6 partners mediating promitogenic activity. These results highlight a new aspect of Arf6 functioning in cancer cell biology.
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PMID:Arf6 promotes cell proliferation via the PLD-mTORC1 and p38MAPK pathways. 2192 24