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)

The myeloid 32D cell line, which grows in suspension and does not express FGF receptors or heparan sulfate proteoglycans, was transfected with the cDNA encoding FGF receptor-1 (32D-flg cells). When co-cultured with glutaraldehyde-fixed Chinese hamster ovary (CHO) cells, the 32D-flg cells remained in suspension in the absence of FGF-2 but attached to the CHO monolayer in the presence of 10 ng/ml FGF-2. In contrast, 32D cells transfected with the vector alone did not attach to the CHO monolayer in the presence of FGF-2. FGF-2-dependent attachment of 32D-flg cells was prevented by inclusion of 10 micrograms/ml heparin in the incubation medium and was diminished when CHO mutants in glycosaminoglycan synthesis or wild-type CHO cells treated with heparinase were used, indicating that the attachment occurred through FGF-2 interactions with heparan sulfates on the CHO cells. Attachment of 32D-flg cells to wild-type CHO cells was half-maximal at 0.4 ng/ml FGF-2 and was also observed with FGF-1 but not FGF-4. 32D-flg cells also attached to living CHO cells in a FGF-2-dependent manner, but attachment was transient at 37 degrees C. Induction of new proteins was not required for FGF-2-dependent attachment, since attachment occurred when the co-cultures were incubated at 4 degrees C and when the 32D-flg cells were preincubated with cycloheximide. FGF-2-dependent attachment of 32D-flg cells was also observed with Balb/C 3T3, NIH 3T3, and bovine capillary endothelial cells. We conclude that attachment is due to FGF-2 binding simultaneously to receptors on the 32D-flg cells and heparan sulfates on the CHO monolayers; thus, the FGF-2 acts as a bridge between receptor-expressing cells and heparan sulfate-bearing cells. In addition, induction of DNA synthesis in 32D-flg cells in response to FGF-2 was potentiated by the CHO-associated heparan sulfates to the same extent as by soluble heparin, indicating that this interaction has functional significance.
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PMID:Fibroblast growth factor-2 can mediate cell attachment by linking receptors and heparan sulfate proteoglycans on neighboring cells. 759 23

Heparan sulfate proteoglycans (HSPG) are obligatory for receptor binding and mitogenic activity of basic fibroblast growth factor (bFGF). Mutant Chinese hamster ovary cells (pgsA-745) deficient in xylosyltransferase are unable to initiate glycosaminoglycan synthesis and hence can not bind bFGF to low- and high-affinity cell surface receptors. Exposure of pgsA-745 cells to beta-D-xylopyranosides containing hydrophobic aglycones resulted in restoration of bFGF binding in a manner similar to that induced by soluble heparin or by heparan sulfate (HS) normally associated with cell surfaces. Restoration of bF-GF binding correlated with the ability of the beta-D-xylosides to prime the synthesis of heparan sulfate. Thus, both heparan sulfate synthesis and bFGF receptor binding were induced by low concentrations (10-30 microM) of estradiol-beta-D-xyloside and naphthyl-beta-D-xyloside, but not by cis/trans-decahydro-2-naphthyl-beta-D-xyloside, which at low concentration primes mainly chondroitin sulfate. The obligatory involvement of xyloside-primed heparan sulfate in restoration of bFGF-receptor binding was also demonstrated by its sensitivity to heparinase treatment and by the lack of restoration activity in CHO cell mutants that lack enzymatic activities required to form the repeating disaccharide unit characteristic of heparan sulfate. Xyloside-primed heparan sulfate binds to the cell surface. Restoration of bFGF receptor binding was induced by both soluble and cell bound xyloside-primed heparan sulfate and was abolished in cells that were exposed to 0.5-1.0 M NaCl prior to the bFGF binding reaction. These results indicate that heparan sulfate chains produced on xyloside primers behave like heparan sulfate chains attached to cellular core proteins in terms of affinity for bFGF and ability to function as low-affinity sites in a dual receptor mechanism characteristic of bFGF and other heparin-binding growth promoting factors.
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PMID:Heparan sulfate primed on beta-D-xylosides restores binding of basic fibroblast growth factor. 775 55

Tumor cells of glial origin express high levels of basic fibroblast growth factor (bFGF) which stimulates their proliferation in an autocrine manner. In the present study we examined bFGF receptor (FGFR) expression and 125I-bFGF binding and processing in a human glioma cell line. RT-PCR demonstrated the co-expression of bFGF and FGFR mRNAs in five glioma cell lines examined. The high-affinity FGFR was visualized in U87-MG glioma cells by crosslinking with 125I-bFGF and by Western blotting with anti-receptor antisera. Both techniques identified a discrete 110-kDa moiety associated with the cell membrane, consistent with the reported size of one of the FGFR-1 isoforms. Western blotting also identified an intracellular receptor pool which was not accessible with exogenous 125I-bFGF. Suramin treatment induced a 2-fold increase in immunoreactive FGFR and a 1.5-fold increase in 125I-bFGF binding sites, indicating that FGFRs are chronically down-regulated by endogenous bFGF in U87-MG cells. Removal of extracellular bFGF with heparin resulted in a rapid, cycloheximide-sensitive increase in high-affinity bFGF binding sites. At 37 degrees C, receptor-bound 125I-bFGF was internalized and subjected to limited proteolytic cleavage over 12 h. U87-MG cells also contained abundant low-affinity bFGF binding sites which were removed by digestion with heparinase III but not by chondroitinase ABC. The presence of heparin (25 micrograms/ml) in the binding reaction eliminated the association of 125I-bFGF with the heparin-like sites but did not prevent binding to the high-affinity receptor. Scatchard binding analysis in the presence of heparin revealed a single class of high-affinity sites in U87-MG cells (Kd = 4.9 +/- 0.9 pM; 10-12 x 10(3) sites per cell). Neither heparin nor heparinase digestion prevented the binding of 125I-bFGF to the detergent-extractable high-affinity receptor, although both treatments significantly reduced the extent of 125I-bFGF association with the receptor. These findings indicate that in U87-MG cells, heparan sulfate proteoglycans may be involved in presentation of bFGF to the high-affinity receptor, but are not essential for high-affinity binding to occur.
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PMID:Basic fibroblast growth factor binding and processing by human glioma cells. 867 45