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: EC:4.2.2.7 (heparinase)
1,270 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Midkine (MK), a retinoic acid-inducible heparin-binding protein, is a mitogen which initiates a cascade of intracellular protein tyrosine phosphorylation mediated by the JAK/STAT pathway after binding to its high affinity p200(+)/MKR cell surface receptor in the G401 cell line [Ratovitski, E. A. (1998) J. Biol. Chem. 273, 3654-3660]. In this study, we determined the biophysical characteristics of purified recombinant murine MK and analyzed the requirements for ligand multimerization and cell surface proteoglycan binding for the G401 cell mitogenic activity of MK. Our studies indicate that the secreted form of MK (M = 13 kDa) exists in solution as an asymmetric monomer with a frictional coefficient of 1. 48 and a Stokes radius of 23.7 A. By constructing bead models of MK using the program AtoB and the program HYDRO to predict the hydrodynamic properties of each model, our data suggest that MK has a dumb-bell shape in solution composed of independent N- and C-terminal domains separated by an extended linker. This asymmetric MK monomer is a biologically active ligand with mitogenic activity on G401 cells in vitro. Neither heparin-induced formation of noncovalent MK multimers nor tissue transglutaminase II covalent multimerization of MK enhanced MK mitogenic activity in this system. Since neither heparin competition nor cell treatment with chondroitinase ABC or heparinase III abolished the mitogenic effects of MK on G401 cells, cell-surface proteoglycan binding by MK does not appear to be a requirement for its observed mitogenic effects. These results provide strong evidence that the MK-specific p200(+)/MKR has distinctive biochemical properties which distinguish it from the receptor tyrosine phosphatase cell-surface proteoglycan PTPzeta/RPTPbeta and support the hypothesis that the diverse biological effects of MK are mediated by multiple cell-specific signal transduction receptors.
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PMID:Monomeric midkine induces tumor cell proliferation in the absence of cell-surface proteoglycan binding. 1082 69

In the absence of heparan sulfate (HS) on the surface of target cells, or free heparin (HP) in the vicinity of their receptors, fibroblast growth factor (FGF) family members cannot exert their biological activity and are easily damaged by proteolysis. This limits the utility of FGFs in a variety of applications including treatment of surgical, burn, and periodontal tissue wounds, gastric ulcers, segmental bony defects, ligament and spinal cord injury. Here we describe an FGF analog engineered to overcome this limitation by fusing FGF-1 with HS proteoglycan (PG) core protein. The fusion protein (PG-FGF-1), which was expressed in Chinese hamster ovary cells and collected from the conditioned medium, possessed both HS and chondroitin sulfate sugar chains. After fractionation, intact PG-FGF-1 proteins with little affinity to immobilized HP and high-level HS modification, but not their heparitinase or heparinase digests, exerted mitogenic activity independent of exogenous HP toward HS-free Ba/F3 transfectants expressing FGF receptor. Although PG-FGF-1 was resistant to tryptic digestion, its physiological degradation with a combination of heparitinase and trypsin augmented its mitogenic activity toward human endothelial cells. The same treatment abolished the activity of simple FGF-1 protein. By constructing a biologically active proteoglycan-FGF-1 fusion protein, we have demonstrated an approach that may prove effective for engineering not only FGF family members, but other HP-binding molecules as well.
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PMID:Engineering of an FGF-proteoglycan fusion protein with heparin-independent, mitogenic activity. 1083 2

Neutrophil-induced damage to the protective epithelium has been implicated in mucosal disorders associated with hypoxia, and such damage may be initiated by epithelial-derived chemokines. Because chemokines can bind to membrane proteoglycans, we hypothesized that chemokines may associate with epithelial surfaces and activate polymorphonuclear neutrophils (PMN). Epithelial hypoxia (pO2 20 torr) resulted in a time-dependent induction of interleukin-8 (IL-8) mRNA, soluble protein, as well as surface protein. Such surface IL-8 expression was demonstrated to be dependent on heparinase III expression, and extensions of these experiments indicated that hypoxia induces epithelial perlecan expression in parallel with IL-8. Finally, co-incubation of post-hypoxic epithelia with human PMN induced IL-8-dependent expression of the PMN beta2-integrin CD11b/18. These data indicate that chemokines liberated from epithelia may exist in a surface-bound, bioactive form and that hypoxia may regulate proteoglycan expression.
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PMID:Parallel induction of epithelial surface-associated chemokine and proteoglycan by cellular hypoxia: implications for neutrophil activation. 1094 70

The endothelial surface layer (glycocalyx) of cerebral capillaries may increase resistance to blood flow. This hypothesis was investigated in mice by intravenous administration of heparinase (2500 IU/kg body weight in saline), which cleaves proteoglycan junctions of the glycocalyx. Morphology was investigated by transmission electron microscopy. Cerebral perfusion velocity was recorded before and during heparinase or saline treatment using laser-Doppler flowmetry. In addition, cerebral blood flow (CBF) was measured 10 minutes after heparinase or saline treatment using the iodo[14C]antipyrine method. Laser-Doppler flowmetry and CBF measurements were performed during normocapnia and severe hypercapnia (PCO2: 120 mm Hg). After heparinase, morphology showed a reduced thickness of the glycocalyx in cortical microvessels by 43% (P < 0.05) compared with saline-treated controls. Under normocapnic conditions, a 15% (P < 0.05) transient increase of cerebral flow velocity occurred 2.5 to 5 minutes after heparinase injection. Laser-Doppler flow and CBF returned to control values ten minutes after the injection. However, during severe hypercapnia, heparinase treatment resulted in a persisting increase in laser-Doppler flow (6%, P < 0.05) and CBF (30%, P < 0.05). These observations indicate the existence of a flow resistance in cerebral capillaries exerted by the glycocalyx. The transient nature of the CBF increase during normocapnia may be explained by a vascular compensation that is exhausted during severe hypercapnia.
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PMID:Influence of the endothelial glycocalyx on cerebral blood flow in mice. 1108 32

We have analyzed the content of N-unsubstituted glucosamine in heparan sulfate from glypican-1 synthesized by endothelial cells during inhibition of (a) intracellular progression by brefeldin A, (b) heparan sulfate degradation by suramin, and/or (c) endogenous nitrite formation. Glypican-1 from brefeldin A-treated cells carried heparan sulfate chains that were extensively degraded by nitrous acid at pH 3.9, indicating the presence of glucosamines with free amino groups. Chains with such residues were rare in glypican-1 isolated from unperturbed cells and from cells treated with suramin and, surprisingly, when nitrite-deprived. However, when nitrite-deprived cells were simultaneously treated with suramin, such glucosamine residues were more prevalent. To locate these residues, chains were first cleaved at linkages to sulfated l-iduronic acid by heparin lyase and released fragments were separated from core protein carrying heparan sulfate stubs. These stubs were then cleaved off at sites linking N-substituted glucosamines to d-glucuronic acid. These fragments were extensively degraded by nitrous acid at pH 3.9. When purified proteoglycan isolated from brefeldin A-treated cells was incubated with intact cells, endoheparanase-catalyzed degradation generated a core protein with heparan sulfate stubs that were similarly sensitive to nitrous acid. We conclude that there is a concentration of N-unsubstituted glucosamines to the reducing side of the endoheparanase cleavage site in the transition region between unmodified and modified chain segments near the linkage region to the protein. Both sites as well as the heparin lyase-sensitive sites seem to be in close proximity to one another.
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PMID:N-unsubstituted glucosamine in heparan sulfate of recycling glypican-1 from suramin-treated and nitrite-deprived endothelial cells. mapping of nitric oxide/nitrite-susceptible glucosamine residues to clustered sites near the core protein. 1111 Jul 83

Scavenger receptor class B type I (SR-BI) mediates the selective uptake of HDL cholesteryl esters (CEs) by the liver. LPL promotes this selective lipid uptake independent of lipolysis. In this study, the role of SR-BI in the mechanism of this LPL-mediated increase in selective CE uptake was explored. Baby hamster kidney (BHK) cells were transfected with the SR-BI cDNA, and significant SR-BI expression could be detected in immunoblots, whereas no SR-BI was visualized in control cells. Y1-BS1 murine adrenocortical cells were cultured without or with adrenocorticotropic hormone, and cells with no detectable or with SR-BI were obtained. These cells incubated without or with LPL in medium containing 125I/[3H]cholesteryl oleyl ether- labeled HDL3; tetrahydrolipstatin inhibited the catalytic activity of LPL. In BHK and in Y1-BS1 cells without or with SR-BI expression, apparent HDL3 selective CE uptake ([3H]CEt - 125I) was detectable. Cellular SR-BI expression promoted HDL3 selective CE uptake by approximately 250-1,900%. In BHK or Y1-BS1 cells, LPL mediated an increase in apparent selective CE uptake. Quantitatively, this stimulating LPL effect was very similar in control cells and in cells with SR-BI expression. The uptake of radiolabeled HDL3 was also investigated in human embryonal kidney 293 (HEK 293) cells that are an established SR-BI-deficient cell model. LPL stimulated [3H]cholesteryl oleyl ether uptake from labeled HDL3 by HEK 293 cells substantially, showing that LPL can induce selective CE uptake from HDL3 independent of SR-BI. To explore the role of cell surface proteoglycans on lipoprotein uptake, we induced proteoglycan deficiency by heparinase treatment. Proteoglycan deficiency decreased the LPL-mediated promotion of HDL3 selective CE uptake. In summary, evidence is presented that the stimulating effect of LPL on HDL3 selective CE uptake is independent of SR-BI and lipolysis. However, cell surface proteoglycans are required for the LPL action on selective CE uptake. It is suggested that pathways distinct from SR-BI mediate selective CE uptake from HDL.
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PMID:Lipoprotein lipase mediates an increase in selective uptake of HDL-associated cholesteryl esters by cells in culture independent of scavenger receptor BI. 1171 43

Proteoglycans have been implicated in the invagination and formation of various embryonal cavitied primordia. In this paper the expression of chondroitin sulphate proteoglycan (CSPG) is analysed in the lens primordium during lens vesicle formation, and demonstrate that this proteoglycan has a specific distribution pattern with regard to invagination and fusion processes in the transformation of placode into lens vesicle. More specifically, CSPG was detected in: (1) the apical surface of lens epithelial cells, where early CSPG expression was observed in the whole of the lens placode whilst in the vesicle phase it was restricted to the posterior epithelium; (2) intense CSPG expression in the basal lamina, which remained constant for the entire period under study; (3) CSPG expression in the intercellular spaces of the lens primordium epithelium, which increased during the invagination of the primordium and which at the vesicle stage was more evident in the posterior epithelium; and (4) CSPG expression on the edges of the lens placode both prior to and during fusion. Treatment with beta- D -xyloside causes significant CSPG depletion in the lens primordium together with severe alterations in the invagination and fusion of the lens vesicle; this leads to the formation of lens primordia which in some cases remain practically flat or show partial invagination defects or fusion disruption. Similar results were obtained by enzyme digestion with chondroitinase AC but not with type II heparinase, which indicates that alterations induced by beta- D -xyloside were due to interference in CSPG synthesis. The findings demonstrate that CSPG is a common component of the lens primordium at the earliest developmental stages during which it undergoes specific modifications. It also includes experimental evidence to show that 'in vivo' CSPG plays an important role in the invagination and fusion processes of the lens primordium.
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PMID:Chondroitin sulphate proteoglycan is involved in lens vesicle morphogenesis in chick embryos. 1182 19

We have previously shown that enterotoxigenic invasion protein A (Tia), a 25-kDa outer membrane protein encoded on an apparent pathogenicity island of enterotoxigenic Escherichia coli (ETEC) strain H10407, mediates attachment to and invasion into cultured human gastrointestinal epithelial cells. The epithelial cell receptor(s) for Tia has not been identified. Here we show that Tia interacts with cell surface heparan sulfate proteoglycans. Recombinant E. coli expressing Tia mediated invasion into wild-type epithelial cell lines but not invasion into proteoglycan-deficient cells. Furthermore, wild-type eukaryotic cells, but not proteoglycan-deficient eukaryotic cells, attached to immobilized polyhistidine-tagged recombinant Tia (rTia). Binding of epithelial cells to immobilized rTia was inhibited by exogenous heparan sulfate glycosaminoglycans but not by hyaluronic acid, dermatan sulfate, or chondroitin sulfate. Similarly, pretreatment of eukaryotic cells with heparinase I, but not pretreatment of eukaryotic cells with chrondroitinase ABC, inhibited attachment to rTia. In addition, we also observed heparin binding to both immobilized rTia and recombinant E. coli expressing Tia. Heparin binding was inhibited by a synthetic peptide representing a surface loop of Tia, as well as by antibodies directed against this peptide. Additional studies indicated that Tia, as a prokaryotic heparin binding protein, may also interact via sulfated proteoglycan molecular bridges with a number of mammalian heparan sulfate binding proteins. These findings suggest that the binding of Tia to host epithelial cells is mediated at least in part through heparan sulfate proteoglycans and that ETEC belongs on the growing list of pathogens that utilize these ubiquitous cell surface molecules as receptors.
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PMID:Interaction of an uuter membrane protein of enterotoxigenic Escherichia coli with cell surface heparan sulfate proteoglycans. 1185 41

Our current studies have demonstrated that human parainfluenza virus type 3 (HPIV-3) utilizes heparan sulfate (HS) for its efficient cellular entry. HPIV-3 interacted with HS-agarose in vitro and the cellular entry and infection of HPIV-3 were reduced following (a) infection of human epithelial lung A549 cells with HPIV-3 pre-incubated with soluble HS; (b) treatment of A549 cells with heparinase to remove cell surface HS and sodium chlorate (NaClO(3)), a potent inhibitor of proteoglycan sulfation; and (c) infection of HS-deficient mutant CHO cell lines. However, in each instance, complete inhibition of HPIV-3 entry did not occur, suggesting the presence of additional nonproteoglycan cell surface molecule(s) that is required for HPIV-3 entry. Thus the cell surface HS appears to play an important role in efficient cellular entry of HPIV-3.
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PMID:Role of heparan sulfate in human parainfluenza virus type 3 infection. 1209 75

Scavenger receptor class B type I (SR-BI) mediates the selective uptake of HDL cholesteryl esters (CEs) by the liver. Hepatic lipase (HL) promotes this lipid uptake independent from lipolysis. The role of SR-BI in this HL-mediated increase in selective CE uptake was explored. Baby hamster kidney (BHK) cells were transfected with the SR-BI cDNA yielding cells with SR-BI expression, whereas no SR-BI was detected in control cells. These cells were incubated in medium containing 125I [3H]cholesteryl oleyl ether-labeled HDL3 (d = 1.125-1.21 g/ml) and HL was absent or present. Tetrahydrolipstatin (THL) blocked lipolysis. In control BHK cells and in BHK cells with SR-BI, HDL3 selective CE uptake (3H-125I) was detectable and SR-BI promoted this uptake. In both cell types, HL mediated an increase in selective CE uptake from HDL3. Quantitatively, this HL effect was similar in control BHK cells and in BHK cells with SR-BI. These results suggest that HL promotes selective uptake independent from SR-BI. To investigate the role of cell surface proteoglycans on the HL-mediated HDL3 uptake, proteoglycan deficiency was induced by heparinase digestion. Proteoglycan deficiency decreased the HL-mediated promotion of selective CE uptake. In summary, the stimulating HL effect on HDL selective CE uptake is independent from SR-BI and lipolysis. Proteoglycans are a requisite for the HL action on selective uptake. Results suggest that (a) pathway(s) distinct from SR-BI mediate(s) selective CE uptake from HDL.
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PMID:Hepatic lipase mediates an increase in selective uptake of HDL-associated cholesteryl esters by cells in culture independent from SR-BI. 1261 11


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