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

A great deal of evidence has accumulated in recent years for an important but complex role for proteases in tumor development. However, attempts to treat cancer in humans with anti-proteases have been disappointing, and it has been suggested that more basic groundwork is needed before anti-proteases can be effectively applied. Considerable basic information comes from the recognition that earlier results on transformation of chicken embryo fibroblasts (CEF) by the Bryan strain of Rous sarcoma virus (B-RSV) can be explained in terms of proteases and their inhibitors. In particular, the full but reversible normalization of discrete transformed foci by appropriate concentrations of fetal bovine or of calf serum implies a causal role for multiple proteases in transformation, and the efficacy of treatment with a physiological balance of their natural inhibitors. Addition of certain proteases to contact-inhibited normal cultures was then found to stimulate their proliferation. The toxicity of medium produced by CEF heavily transformed with B-RSV suggests that cachexia and other systemic effects of human cancer may result from vascular dissemination of peptides from pericellular proteolysis within tumors. Comprehensive studies revealed significant increases of plasminogen activator and matrix metalloproteinases (MMPs) after infection of CEF with other strains of RSV, and correlation of the proteases with aspects of transformation. A similar role for proteases is indicated in the transformation of mammalian cells by chemical and physical agents. The information gained from functional experiments on cell transformation in culture is complementary to that obtained from the molecular identification of proteases and their inhibitors in all stages of tumor development. The speed, quantification and easy manipulation of the RSV-CEF transformation assay can be combined with current methods of characterizing proteases and anti-proteases to further enrich our basic knowledge of neoplastic development in cells, and facilitate its application to the treatment of cancer.
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PMID:Complementary approaches to understanding the role of proteases and their natural inhibitors in neoplastic development: retrospect and prospect. 1277 Oct 23

The proteolysis-inducing factor (PIF) is produced by cachexia-inducing tumours and initiates protein catabolism in skeletal muscle. The potential signalling pathways linking the release of arachidonic acid (AA) from membrane phospholipids with increased expression of the ubiquitin-proteasome proteolytic pathway by PIF has been studied using C(2)C(12) murine myotubes as a surrogate model of skeletal muscle. The induction of proteasome activity and protein degradation by PIF was blocked by quinacrine, a nonspecific phospholipase A(2) (PLA(2)) inhibitor and trifluroacetyl AA, an inhibitor of cytosolic PLA(2). PIF was shown to increase the expression of calcium-independent cytosolic PLA(2), determined by Western blotting, at the same concentrations as those inducing maximal expression of 20S proteasome alpha-subunits and protein degradation. In addition, both U-73122, which inhibits agonist-induced phospholipase C (PLC) activation and D609, a specific inhibitor of phosphatidylcholine-specific PLC also inhibited PIF-induced proteasome activity. This suggests that both PLA(2) and PLC are involved in the release of AA in response to PIF, and that this is important in the induction of proteasome expression. The two tyrosine kinase inhibitors genistein and tryphostin A23 also attenuated PIF-induced proteasome expression, implicating tyrosine kinase in this process. PIF induced phosphorylation of p44/42 mitogen-activated protein kinase (MAPK) at the same concentrations as that inducing proteasome expression, and the effect was blocked by PD98059, an inhibitor of MAPK kinase, as was also the induction of proteasome expression, suggesting a role for MAPK activation in PIF-induced proteasome expression.
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PMID:Signal transduction pathways involved in proteolysis-inducing factor induced proteasome expression in murine myotubes. 1458 84