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

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Query: UNIPROT:P00750 (PLA)
16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Basic fibroblast growth factor (bFGF) is a potent mitogen for human bone marrow stromal cells and stimulates haematopoiesis in vitro. We report here that primary human bone marrow cultures contain bFGF and express heparin-like bFGF binding sites on the cell surface and in the extracellular matrix (ECM). bFGF bound predominantly to a 200-kD cell surface heparan sulfate proteoglycan (HSPG), which was also found in conditioned medium. bFGF was released from bone marrow cultures by incubation with phosphatidylinositol-specific phospholipase C (PI-PLC) and, less efficiently, by plasmin. Solubilized bFGF was found as a complex with the 200-kD HSPG. The complex was biologically active as shown by its ability to stimulate plasminogen activator production in bovine aortic endothelial cells. bFGF-HSPG complexes of bovine endothelial cells, however, were not released by PI-PLC. While only trace amounts of the bFGF-binding 200-kD HSPG were released spontaneously from bone marrow cultures, incubation with PI-PLC solubilized almost all of the 200-kD HSPG. The HSPG could be metabolically labeled with ethanolamine or palmitate, which was partially removed by treatment with PI-PLC. These findings indicate linkage of the HSPG to the cell surface via a phosphatidylinositol anchor. Plasmin released the 200-kD HSPG less efficiently than PI-PLC. We conclude that HSPGs of human bone marrow serve as a reservoir for bFGF, from which it can be released in a biologically active form via a dual mechanism; one involving a putative endogenous phospholipase, the other involving the proteolytic cascade of plasminogen activation.
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PMID:Phospholipase C release of basic fibroblast growth factor from human bone marrow cultures as a biologically active complex with a phosphatidylinositol-anchored heparan sulfate proteoglycan. 165 37

Cultured bovine capillary endothelial (BCE) cells were found to synthesize and secrete high molecular mass heparan sulfate proteoglycans and glycosaminoglycans, which bound basic fibroblast growth factor (bFGF). The secreted heparan sulfate molecules were purified by DEAE cellulose chromatography, followed by Sepharose 4B chromatography and affinity chromatography on immobilized bFGF. Most of the heparinase-sensitive sulfated molecules secreted into the medium by BCE cells bound to immobilized bFGF at low salt concentrations. However, elution from bFGF with increasing salt concentrations demonstrated varying affinities for bFGF among the secreted heparan sulfate molecules, with part of the heparan sulfate requiring NaCl concentrations between 1.0 and 1.5 M for elution. Cell extracts prepared from BCE cells also contained a bFGF-binding heparan sulfate proteoglycan, which could be released from the intact cells by a short proteinase treatment. The purified bFGF-binding heparan sulfate competed with 125I-bFGF for binding to low-affinity binding sites but not to high-affinity sites on the cells. Heparan sulfate did not interfere with bFGF stimulation of plasminogen activator activity in BCE cells in agreement with its lack of effect on binding of 125I-bFGF to high-affinity sites. Soluble bFGF was readily degraded by plasmin, whereas bFGF bound to heparan sulfate was protected from proteolytic degradation. Treatment of the heparan sulfate with heparinase before addition of plasmin abolished the protection and resulted in degradation of bFGF by the added proteinase. The results suggest that heparan sulfate released either directly by cells or through proteolytic degradation of their extracellular milieu may act as carrier for bFGF and facilitate the diffusion of locally produced growth factor by competing with its binding to surrounding matrix structures. Simultaneously, the secreted heparan sulfate glycosaminoglycans protect the growth factor from proteolytic degradation by extracellular proteinases, which are abundant at sites of neovascularization or cell invasion.
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PMID:Endothelial cell-derived heparan sulfate binds basic fibroblast growth factor and protects it from proteolytic degradation. 297 Oct 68

A basic understanding of growth cone dynamics and developmental events involving growth cones requires an understanding of the function and regulation of molecules associated with and released by growth cones. Rat sympathetic neurons in culture release a urokinase-like plasminogen activator from their distal processes and/or growth cones (Pittman, 1985a). When sympathetic neurons are grown in cocultures with heart cells, however, plasminogen activator activity is not detected. The absence of plasminogen activator activity in cocultures of sympathetic neurons and heart cells appears to be due to the release of an inhibitor of plasminogen activator by heart cells. This inhibitor has a molecular weight of approximately 50 kDa in the presence of SDS and apparent molecular weights of approximately 50 and greater than 2000 kDa under native conditions. A significant fraction of the large-molecular-weight form of the inhibitor is converted to the smaller form following treatment with heparinase. Extremely stable complexes of 68 and 80 kDa are formed between the heart inhibitor and the plasminogen activator, urokinase, such that the complexes withstand boiling in SDS/mercaptoethanol. The data are consistent with the formation of an 80 kDa urokinase-inhibitor complex in the presence of heparan sulfate proteoglycan and a 68 kDa complex in the absence of heparan sulfate proteoglycan. A highly purified preparation of the heart inhibitor produces a 2- to 3-fold increase in neurite outgrowth from sympathetic neurons. These data indicate that the activity of the plasminogen activator released by sympathetic neurons can be regulated by a normal target tissue and that this regulation may result in increased neurite outgrowth from the neurons.
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PMID:Characterization of an inhibitor of neuronal plasminogen activator released by heart cells. 362 68

Using modeling of heparin-fibroblast growth factor interactions, we replaced four basic residues of basic fibroblast growth factor (FGF-2) with neutral glutamine residues by site-specific mutagenesis to give the mutants K128Q, K138Q, K128Q-K138Q, R129Q, K134Q, and R129Q-K134Q. The FGF mutants were characterized for their receptor and heparin binding affinities, mitogenic and cell proliferation activities, and their ability to induce plasminogen activator (PA) production and in vitro angiogenesis by cultured endothelial cells. Heparin binding properties and biological activities of the three mutants involving R129 and K134 remained essentially unchanged; however, significant changes for three mutants involving K128 and K138 were found. The KD values for heparin binding for K128Q and K138Q mutants were increased about 10-fold, and that for the K128Q-K138Q double mutant was increased by about 100-fold. The mutant K128Q-K138Q required a 10-fold higher concentration of heparin to promote binding to heparan sulfate proteoglycan (HSPG)-deficient CHO cells transfected with fibroblast growth factor receptor-1 (FGFR1) or to induce DNA synthesis in HSPG-deficient myeloid cells transfected with FGFR1. Binding affinities of the mutants to cell surface receptors on BHK-21 cells, however, were similar to that of wild-type FGF-2. In endothelial cell proliferation assays the activities of K128Q and K128Q-K138Q were about 10-fold lower than that of the wild-type protein, whereas the K138Q mutant exhibited wild-type activity. In addition, the K128Q-K138Q mutant displayed a markedly lowered capacity to induce PA activity in cultured endothelial cells and to form capillary-like structures in an in vitro angiogenesis model.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Diminished heparin binding of a basic fibroblast growth factor mutant is associated with reduced receptor binding, mitogenesis, plasminogen activator induction, and in vitro angiogenesis. 752 51

Epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) stimulates cell migration, proliferation and the formation of tube-like structures of human microvascular endothelial cells in culture. Heparin-binding EGF-like growth factor(HB-EGF), which shows 35% homology with EGF/TGF-alpha, is a member of the EGF family, and it is ubiquitous in many tissues and organs. We examined whether or not HB-EGF induced angiogenic responses in human microvascular endothelial cells. HB-EGF inhibited the binding of (125) I-EGF to the EGF receptor and induced autophosphorylation of the receptor on endothelial cells. Exogenous HB-EGF induced the loss of more than 70% of the EGF receptor from the cell surface within 30 min, with similar kinetics to that of EGF. The level of c-fos mRNA markedly increased at 30 min in response to HB-EGF as well as EGF. A gel shift assay demonstrated the activation of the transcription factor p91 by HB-EGF and EGF. This factor directly interacts with EGF receptor and mediates the activation of c-fos gene promoter. HB-EGF enhanced the mRNA expression of tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) mRNA. However, the enhancement of t-PA and PAI-1 by HB-EGF was less than that by EGF. Heparitinase/chlorate, which digests the heparan sulfate proteoglycan of the endothelial cell surface, restored both t-PA and PAI-1 mRNA levels in response to HB-EGF in a manner similar to that by EGF. HB-EGF at 10 ng/ml developed tube-like structures in type I collagen gel at similar levels to that of EGF at 10 ng/ml, suggesting that HB-EGF is also a potent angiogenic factor in the model system for angiogenesis. The tubulogenesis activity of HB-EGF is discussed in relation to the expression of the t-PA and PAI-1 genes.
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PMID:Heparin-binding epidermal growth factor-like growth factor: p91 activation induction of plasminogen activator/inhibitor, and tubular morphogenesis in human microvascular endothelial cells. 860 52

Myoepithelial cells in situ and in vitro exert important paracrine effects on carcinoma cells which are mediated by high expression of extracellular matrix molecules, proteinase inhibitors and angiogenic inhibitors. Myoepithelial xenografts (human matrix secreting (HMS)-X, HMS-3X and HMS-4X) established from benign human salivary gland and breast myoepithelial tumors accumulate an abundant extracellular matrix which can be extracted with 6 M urea and 2 M guanidinium hydrochloride to form a gel at 25-37 degrees C. This gel, termed Humatrix, exhibits different biochemical and biological properties than the conventional non-human matrical gels in existence, i.e. Matrigel and Vitrogen 100. Whereas Matrigel consists mainly of basement membrane molecules, e.g. laminin, type IV collagen and heparan sulfate proteoglycan, and Vitrogen 100 consists mainly of non-basement membrane molecules, e.g. type I and type III collagen, Humatrix contains significant amounts of both basement membrane and non-basement membrane molecules, including large amounts of chondroitin sulfate proteoglycan. Like Matrigel, Humatrix contains bound growth factors, including epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I); unlike Matrigel, which contains predominantly significant quantities of bound proteinases, including tissue-type plasminogen activator (tPA), matrix metalloproteinase (MMP)-2 and MMP-9, and angiogenic factors, including basic fibroblast growth factor (bFGF) and transforming growth factor (TGF)-beta, Humatrix contains predominantly bound proteinase inhibitors such as protease nexin II (PN-II) and alpha1-antitrypsin and angiogenic inhibitors such as thrombospondin-1. Humatrix selectively stimulates the growth and tumorigenicity of human myoepithelial cell lines but inhibits invasion, angiogenesis and metastasis of other non-myoepithelial malignant cell lines. Because of its myoepithelial origin Humatrix represents a more natural source of extracellular matrix molecules and bound factors that carcinoma cells encounter in vivo.
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PMID:Humatrix, a novel myoepithelial matrical gel with unique biochemical and biological properties. 948 91

Accumulating evidence has suggested that cytosolic phospholipase A(2) (cPLA(2)) and several secretory PLA(2) (sPLA(2)) isozymes are signaling PLA(2)s that are functionally coupled with downstream cyclooxygenase (COX) isozymes for prostaglandin (PG) biosynthesis. Arachidonic acid (AA) released by cPLA(2) and sPLA(2)s is supplied to both COX-1 and COX-2 in the immediate, and predominantly to COX-2 in the delayed, PG-biosynthetic responses. Vimentin, an intermediate filament component, acts as a functional perinuclear adapter for cPLA(2), in which the C2 domain of cPLA(2) associates with the head domain of vimentin in a Ca(2+)-sensitive manner. The heparin-binding signaling sPLA(2)-IIA, IID and V bind the glycosylphosphatidylinositol-anchored heparan sulfate proteoglycan glypican, which plays a role in sorting of these isozymes into caveolae and perinuclear compartments. Phospholipid scramblase, which facilitates transbilayer movement of anionic phospholipids, renders the cellular membranes more susceptible to signaling sPLA(2)s. There is functional cooperation between cPLA(2) and signaling sPLA(2)s in that prior activation of cPLA(2) is required for the signaling sPLA(2)s to act properly. cPLA(2)-derived AA is oxidized by 12/15-lipoxygenase, the products of which not only augment the induction of sPLA(2) expression, but also cause membrane perturbation, leading to increased cellular susceptibility to the signaling sPLA(2)s. sPLA(2)-X, a heparin-non-binding sPLA(2) isozyme, is capable of releasing AA from intact cells in the absence of cofactors. This property is attributed to its ability to avidly hydrolyze zwitterionic phosphatidylcholine, a major phospholipid in the outer plasma membrane. sPLA(2)-V can also utilize this route in several cell types. Taken together, the AA-releasing function of sPLA(2)s depends on the presence of regulatory cofactors and interfacial binding to membrane phospholipids, which differ according to cell type, stimuli, secretory processes, and subcellular distributions.
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PMID:Cellular components that functionally interact with signaling phospholipase A(2)s. 1108 Jun 85

Lysophosphatidylserine (1-acyl-2-lyso-PS) has been shown to stimulate histamine release from rat peritoneal mast cells (RPMC) triggered by FcepsilonRI (high affinity receptor for IgE) cross-linking, although the precise mechanism of lyso-PS production has been obscure. In the present study we show that phosphatidylserine-specific phospholipase A(1), PS-PLA(1), stimulates histamine release from RPMC through production of 2-acyl-1-lyso-PS in the presence of FcepsilonRI cross-linker. The potency of 2-acyl-1-lyso-PS was almost equal to that of 1-acyl-2-lyso-PS. A catalytically inactive PS-PLA(1), in which an active serine residue (Ser(166)) was replaced with an alanine residue did not show such activity. sPLA(2)-IIA, another secretory PLA(2) that is capable of producing lyso-PS in vitro, was also a poor histamine inducer against RPMC. PS-PLA(1) significantly stimulated histamine release from crude RPMC, indicating that lyso-PS is mainly derived from cells other than mast cells. In agreement with this phenomenon, the enzyme stimulated the histamine release more efficiently when RPMC were mixed with apoptotic Jurkat cells. Under these conditions, lyso-PS with unsaturated fatty acid was released from the apoptotic cells treated with PS-PLA(1). Finally, heparin, which has affinity for PS-PLA(1), completely blocked the stimulatory effect of the enzyme. In conclusion, PS-PLA(1) may bind to heparan sulfate proteoglycan, efficiently hydrolyze PS appearing on plasma membranes of apoptotic cells, and stimulate mast cell activation mediated by 2-acyl-1-lyso-PS.
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PMID:Phosphatidylserine-specific phospholipase A1 stimulates histamine release from rat peritoneal mast cells through production of 2-acyl-1-lysophosphatidylserine. 1139 20

Cadmium and lead are heavy metals that have been shown to induce vascular disorders such as atherosclerosis in experimental animals. However, little is known about the mechanisms by which cadmium and lead induce vascular toxicity. The toxicity was investigated using a culture system of vascular endothelial and smooth muscle cells. Cadmium destroys the monolayer of endothelial cells and the cytotoxicity is protected by zinc and copper without metallothionein induction. On the other hand, lead does not exhibit cytotoxicity but inhibits the repair of endothelial monolayers after wounding by a lower response to endogenous basic fibroblast growth factor mediated by suppression of the synthesis of perlecan, a large heparan sulfate proteoglycan. In addition, cadmium and lead reduce endothelial fibrinolytic activity by induction of plasminogen activator inhibitor type 1 synthesis and by inhibition of tissue-type plasminogen activator, respectively. In vascular smooth muscle cells, cadmium and lead can promote their proliferation and influence proteoglycan synthesis and fibrinolysis in different manners. These results indicate that cadmium and lead have specific toxicities in the proliferation, fibrinolysis, and extracellular matrix formation of vascular endothelial and smooth muscle cells.
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PMID:[Cell biology of heavy metal toxicity in vascular tissue]. 1504 28

The oral delivery of macromolecules using nanoparticles is limited by secreted mucus, resulting in low contact or internalization via intestinal cells and, thus, both mucus trapping and further low cellular uptake need to be overcome. Here, hydrophilic and electroneutral nanoparticles were developed to overcome mucus trapping and enhance the oral delivery of macromolecules. Mesoporous silica nanoparticles (MSNs) were synthesized and modified with a hydrophilic block polymer (poly(lactic acid)-methoxy poly(ethylene glycol), PLA-PEG), and then an overall electroneutrality and promoted cellular uptake were achieved by sequential modification with cell-penetrating peptides (CPPs). Reduced hydrophobic and electrostatic interactions of MSN@PLA-PEG-CPP with mucus decreased mucus trapping by 36.0%, increased the cellular uptake of MSN@PLA-PEG-CPP by 2.3-folds in mucous conditions via active heparan sulfate proteoglycan receptor (HSPG)-mediated and caveolae-mediated endocytosis and electrostatic interactions. Furthermore, insulin, a model macromolecular drug, was successfully loaded into the nanoparticles (INS@MSN@PLA-PEG-CPP). Compared with insulin solution, in vitro cellular uptake in mucous conditions and in vivo pharmacodynamic effects were significantly increased by 9.1- and 14.2-folds, respectively. As well, all nanoparticles with or without insulin loading presented negligible in vitro and in vivo toxicity. Herein, hydrophilic and electroneutral nanoparticles with sequential PEG and CPP modification could promote cellular uptake against mucus trapping and finally show good prospects for oral insulin delivery.
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PMID:Hydrophilic and Electroneutral Nanoparticles to Overcome Mucus Trapping and Enhance Oral Delivery of Insulin. 3269 99


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