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G Pejler

Publications and source records attributed to G Pejler.

36 records · Page 2Linked to original sources
PubMed1994

Inhibition of rat mast cell protease 1 by vitronectin.

Rat mast cell protease 1 (RMCP-1) is a chymotrypsin-like serine protease specifically expressed by connective tissue-type mast cells. The enzyme is stored in the secretory granules in a macromolecular complex with heparin proteoglycan. In the present investigation it was shown that RMCP-1 is inhibited by vitronectin (VN), an RGD-containing adhesive glycoprotein with heparin-binding properties. RMCP-1 that had been separated from heparin proteoglycan was less susceptible to inhibition than RMCP-1 present in complex with heparin proteoglycan. Pre-incubation of VN with purified heparin partially blocked the RMCP-1 inhibiting activity of VN. Plasma VN had negligible RMCP-1-inhibiting activity. However, heat treatment of plasma VN, which is known to expose the heparin-binding domain, induced RMCP-1-inhibiting activity. Affinity chromatography on immobilized VN showed that RMCP-1 bound with high affinity to VN. The binding of RMCP-1 to VN was not heparin-dependent since free RMCP-1 bound with equal affinity to the immobilized VN as RMCP-1 present in complex with heparin. The inhibition of RMCP-1 by VN was shown to be reversible.

Animals↗
PubMed1994

Interaction of heparin with rat mast cell protease 1.

Heparin is a sulfated glycosaminoglycan, synthesized by connective tissue-type mast cells. Rat mast cell protease 1 (RMCP-1), a chymotrypsin-like serine protease expressed specifically by connective tissue-type mast cells, is recovered in a macromolecular complex with heparin proteoglycan. The heparin.RMCP-1 complexes are stored in the secretory granules of the cells and are released following mast cell activation. We showed previously that dissociation of RMCP-1 from heparin resulted in loss of protease activity, as measured by its ability to inactivate thrombin. In the present report the binding of heparin to RMCP-1 was characterized. Affinity chromatography on heparin-Sepharose showed that RMCP-1 displayed high affinity for heparin, with approximately 1.2 M NaCl being required for elution of RMCP-1 from the affinity matrix. The structural requirements for the binding of heparin to RMCP-1 were investigated. Heparan sulfate, chondroitin sulfate, and dermatan sulfate, three glycosaminoglycans structurally related to heparin, were > or = 80-fold less effective in binding to RMCP-1 than heparin. The 2-O-sulfate, 6-O-sulfate, and N-sulfate groups in heparin were all shown to contribute in the binding. The minimal heparin sequence required for binding to RMCP-1 was found in a 14-saccharide fraction. 14-Saccharide species, obtained after separation by anion exchange chromatography, showed continuously increased binding with increasing anionic charge densities. The 16-18-saccharides were the smallest heparin oligosaccharides capable of accelerating the inactivation of thrombin by RMCP-1.

Animals↗
PubMed1994

Inactivation of thrombin by a complex between rat mast-cell protease 1 and heparin proteoglycan.

Rat peritoneal mast cells were shown to inactivate thrombin rapidly. The thrombin-inactivating activity was purified to homogeneity by a combination of anion-exchange chromatography and h.p.l.c. on a Superdex 75 column. The purified thrombin inactivator had an apparent molecular mass of 29 kDa and an N-terminal amino acid sequence identical to rat mast-cell protease 1 (RMCP-1). After labelling of the mast cells in vivo with 35SO4(2-), RMCP-1 was recovered in a macromolecular complex with [35S]heparin proteoglycans. Dissociation of RMCP-1 from the heparin proteoglycans by Superdex 75 chromatography in the presence of 2 M NaCl resulted in a marked loss of the thrombin-inactivating activity displayed by the enzyme. When RMCP-1 was reconstituted with either endogenous [35S]heparin proteoglycans or standard pig mucosal heparin, the enzyme regained its thrombin-inactivating properties. Affinity chromatography of endogenous [35S]heparin on matrix-linked RMCP-1 demonstrated that all of the heparin molecules contained high-affinity binding sites for the mast-cell protease. In contrast, the endogenous mast-cell heparin showed low affinity for antithrombin, a protease inhibitor involved in the regulation of coagulation enzymes.

Amino Acid Sequence↗
PubMed1993

Thrombin is inactivated by mast cell secretory granule chymase.

In a recent paper we demonstrated that cultures of murine adherent peritoneal cells expressed cell surface-associated serine protease activity that specifically inactivated thrombin by cleaving the enzyme into defined proteolytic fragments (Pejler, G., and Seljelid, R. (1992) J. Biol. Chem. 267, 3136-3142). In the present report, the purification and further characterization of the thrombin-inactivating serine protease is described. The serine protease is shown to be expressed by mast cells. Purification of the thrombin-inactivating serine protease by a combination of anion-exchange chromatography and Superdex 75 chromatography showed that the enzyme had an apparent molecular mass of 28 kDa. N-terminal sequence analysis of the purified protein demonstrated 100% identity of the thrombin-inactivating serine protease with the secretory granule chymases: murine mast cell protease 3 and murine mast cell protease 4. The serine protease showed chymotrypsin-like substrate specificity. The thrombin-inactivating activity was markedly enhanced by optimal concentrations of heparin.

Amino Acid Sequence↗
PubMed1993

Cisplatin-induced platelet activation requires mononuclear cells: role of GMP-140 and modulation of procoagulant activity.

Cytotoxic drugs may potentiate the thrombotic complications in patients with malignancies and platelet function abnormalities have been reported after initiation of cisplatin therapy. This report describes a prolonged activation of platelets over 6-24 h co-culture with peripheral blood mononuclear cells (PBM) by pharmacological doses of cisplatin. Cisplatin had no direct effect on platelets and depended on PBM to produce aggregation which was apparently not mediated by products of the cyclooxygenase or lipoxygenase pathways, by platelet activation factor (PAF) or by thrombin. Although platelet aggregation normally involves the binding of fibrinogen to the beta 3 integrin, GP IIb-IIIa, on activated platelets, the cisplatin-dependent platelet aggregation observed in the co-culture experiments was not inhibited by an anti-GP IIb-IIIa monoclonal antibody which blocks fibrinogen-dependent aggregation nor by an adhesive peptide containing the RGDS integrin recognition sequence. Rather, aggregation appeared to involve a novel 140 kD granule membrane protein (GMP-140) mediated mechanism since aggregation was almost completely blocked by Fab fragments of an antibody to GMP-140 and was inhibited by fluid-phase GMP-140. At concentrations of cisplatin, adriamycin, and LPS that induced equivalent levels of tissue factor of blood monocytes, prothrombinase activity was significantly greater in cultures containing cisplatin. Prothrombinase activity was dependent on the presence of platelets and the rate of thrombin formation was enhanced by factor Xa generated by the tissue factor-factor VIIa complex. These studies suggest that the vascular and thrombotic complications associated with cisplatin therapy are mediated, at least in part, by platelet activation and aggregation and monocyte procoagulant activity.

Blood Coagulation Factors↗
PubMed1992

Inactivation of thrombin by murine peritoneal macrophages.

We recently showed that murine peritoneal macrophages cultured in vitro express potent prothrombinase activity (Lindahl, U., Pejler, G., Bøgwald, J., and Seljelid, R. (1989) Arch. Biochem. Biophys. 273, 180-188). In the present report, we demonstrate that the macrophages also express anticoagulant activity by inactivating the thrombin that is formed due to the action of the prothrombinase. Addition of exogenous purified thrombin to the macrophage cultures resulted in inactivation of the enzyme at a maximum rate of approximately 5 micrograms/h/10(6) cells. The inactivation appeared to be specific for thrombin, since neither Factor Xa, chymotrypsin, nor trypsin, three serine proteases exhibiting homology with thrombin, were inactivated by the macrophages. Thrombin-inactivating activity was not secreted into the culture medium. Inhibitors of endocytosis did not decrease the rate by which thrombin was inactivated, suggesting that internalization of the coagulation factor was not required. In contrast, the thrombin-inactivating activity was strongly inhibited by the polycation Polybrene. Anion-exchange chromatography of extracts obtained after Triton X-100-solubilization of the macrophages demonstrated that the thrombin-inactivating activity exhibited a high negative charge. Incubation of the thrombin-inactivating activity recovered after anion-exchange chromatography with unlabeled thrombin, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, showed that thrombin was proteolytically cleaved into defined fragments. Similar proteolytic fragments were obtained when 125I-labeled thrombin was added to macrophage cultures. Degradation of thrombin was blocked by phenylmethanesulfonic fluoride, an inhibitor of serine proteases, but not by inhibitors of other classes of proteases. Thrombin that had been chemically modified at its active site was degraded at the same rate by the macrophages as active thrombin. Taken together, these findings indicate that the murine macrophages express surface-bound serine protease activity that specifically inactivates thrombin by proteolytic cleavage. The significance of thrombin-inactivating activity in relation to the involvement of macrophage procoagulant activity in the immune response is discussed.

Animals↗
PubMed1992

Effective anticoagulation by a low molecular weight heparin (Fragmin) in hemodialysis with a highly permeable polysulfone membrane.

The efficacy and kinetics of a low molecular weight heparin fragment (LMWH-fragment, Fragmin) were studied during one hemodialysis session with a highly permeable polysulfone membrane and compared to a second dialysis session using a conventional cuprophane membrane. All patients received 5000 U of Fragmin given as an injection into the arterial line at start of dialysis. The anticoagulative efficacy was evaluated by measuring plasma fibrinopeptide A concentrations. LMWH-fragment concentrations in plasma and ultrafiltrate were determined by an amidolytic activity assay and by a radioimmunoassay using a monoclonal antibody. During hemodialysis with cuprophane and polysulfone membranes the fibrinopeptide A concentrations were low indicating adequate anticoagulation. LMWH concentrations in plasma did not differ in the two membranes at any time. The LMWH-fragment in the ultrafiltrate could neither be detected with the amidolytic assay nor with the radioimmunoassay. We conclude that a single injection of Fragmin effectively prevents clotting during hemodialysis with a highly polysulfone membrane. No significant amounts of the anticoagulant are lost over the dialysis membrane.

Aged↗
PubMed1989

A prothrombinase complex of mouse peritoneal macrophages.

Addition of prothrombin to mouse peritoneal macrophages in vitro resulted in the formation of a thrombin-like enzyme, as demonstrated by use of the luminogenic peptide substrate S-2621. The prothrombinase activity was sedimented by high-speed centrifugation following homogenization of the cells and was abolished by treatment of the cells with the nonionic detergent Triton X-100 at 0.02% concentration. Moreover, the activity was drastically reduced by maintaining cultures in the presence of warfarin and, presumably due to competitive substrate inhibition, by adding S-2222, a chromogenic peptide substrate for Factor Xa. These findings suggest that prothrombin cleavage is catalyzed by Factor Xa at the macrophage surface. The generated thrombin was inhibited by antithrombin, and this reaction was accelerated by heparin with high affinity for antithrombin but not by the corresponding oligosaccharides composed of 8-14 monosaccharide units. Such oligosaccharides which are capable of accelerating the inactivation of Factor Xa by antithrombin, inhibited thrombin formation from prothrombin in the macrophage cultures, presumably by promoting inactivation by antithrombin of Factor Xa in a prothrombinase complex. Activation of the macrophage coagulation system, as proposed to occur in certain inflammatory conditions, thus may be modulated at various levels by heparin, or heparin oligosaccharides, released from mast cells.

Animals↗
PubMed1989

Anti-thrombin activities of heparin. Effect of saccharide chain length on thrombin inhibition by heparin cofactor II and by antithrombin.

The interactions of two proteinase inhibitors, heparin cofactor II and antithrombin, with thrombin are potentiated by heparin. Using two methods, we have studied the potentiating effects of a series of heparin (poly)saccharides with high affinity for antithrombin and mean Mr ranging from approx. 1700 to 18,800. First, catalytic amounts of heparin (poly)saccharide were added to purified systems containing thrombin and either heparin cofactor II or antithrombin. Residual thrombin activity was determined with a chromogenic substrate. It was found that only the higher-Mr polysaccharides (Mr greater than 8000) efficiently catalysed thrombin inhibition by heparin cofactor II, there being a progressive catalytic effect with increasing Mr of the polysaccharide. Weak accelerating effects were noted with low-Mr saccharides (Mr less than 8000). This contrasted with the well-characterized interaction of heparin with antithrombin and thrombin, where heparin oligosaccharides of Mr less than 5400 had absolutely no ability to accelerate the reaction, while (poly)saccharides of Mr exceeding 5400 showed rapidly increasing catalytic activity with increasing Mr. Secondly, these and other heparin preparations were added in a wide concentration range to plasma with which 125I-labelled thrombin was then incubated for 30 s. Inhibited thrombin was determined from the distribution of labelled thrombin amongst inhibitor-thrombin complexes, predominantly antithrombin-thrombin and heparin cofactor II-thrombin complexes. In this situation, where the inhibitors competed for thrombin and for the (poly)saccharides, it was found that, provided the latter were of high affinity for antithrombin and exceeded a Mr of 5400, thrombin inhibition in plasma was mediated largely through antithrombin. Polysaccharides of Mr exceeding 8000 that were of low affinity for antithrombin accelerated thrombin inhibition in plasma through their interaction with heparin cofactor II. High concentrations of saccharides of Mr 1700-5400 exhibited a size-dependent acceleration of thrombin inhibition, not through their interaction with antithrombin, but through their interaction with heparin cofactor II.

Antithrombins↗
PubMed1989

Location of the antithrombin-binding sequence in the heparin chain.

The antithrombin-binding region of heparin is a pentasaccharide sequence with the predominant structure -GlcNAc(6-OSO3)-GlcA-GlcNSO3(3,6-di-OSO3)-Ido A(2-OSO3)- GlcNSO3(6-OSO3)-. By using the 3-O-sulfated glucosamine residue as a marker for the anti-thrombin-binding sequence, the location of this sequence within the heparin chain was investigated. Heparin with high affinity for antithrombin (HA-heparin) contains few N-acetyl groups located outside the antithrombin-binding region, and cleavage at such groups was therefore expected to be essentially restricted to this region. HA-heparin was cleaved at N-acetylated glucosamine units by partial deacetylation followed by treatment with nitrous acid at pH 3.9, and the resulting fragments with low affinity for anti-thrombin (LA-fragments) were recovered after affinity chromatography on immobilized antithrombin. The LA-fragments were further divided into subfractions of different molecular size by gel chromatography and were then analyzed with regard to the occurrence of the nonreducing terminal GlcA-GlcNSO3(3,6-di-OS-O3)- sequence. Such units were present in small, intermediate-sized as well as large fragments, suggesting that the antithrombin-binding regions were randomly distributed along the heparin chains. In another set of experiments, HA-heparin was subjected to limited, random depolymerization by nitrous acid (pH 1.5), and the resulting reducing terminal anhydromannose residues were labeled by treatment with NaB3H4. The molecular weight distributions of such labeled LA-fragments, determined by gel chromatography, again conformed to a random distribution of the antithrombin-binding sequence within the heparin chains. These results are in apparent disagreement with previous reports (Radoff, S., and Danishefsky, I. (1984) J. Biol. Chem. 259, 166-172; Rosenfeld, L., and Danishefsky, I. (1988) J. Biol. Chem. 263, 262-266) which suggest that the antithrombin-binding region is preferentially located at the nonreducing terminus of the heparin molecule.

Antithrombins↗
PubMed1988

Monoclonal antibodies specific for oligosaccharides prepared by partial nitrous acid deamination of heparin.

Monoclonal antibodies were raised against a conjugate between heparin oligosaccharides and human serum albumin. The oligosaccharides were prepared by partial nitrous acid degradation of heparin and were coupled to human serum albumin by reductive amination. Characterization of the antibodies secreted by one of the resulting clones showed that they recognize a determinant present in the oligosaccharide antigen, but not in intact heparin, nor in a variety of related polysaccharides. Degradation of heparin by nitrous acid generates a 2,5-anhydro-D-mannose residue at the reducing end of the resulting oligosaccharides, and it is concluded that this structure is essential for interaction with the antibodies. Reduced oligosaccharides (containing a terminal anhydromannitol residue) are also active. After gel chromatography of partially degraded heparin, the smallest components capable of binding to the antibodies were found in a tetrasaccharide fraction. Affinity chromatography on immobilized monoclonal antibodies separated this tetrasaccharide fraction into distinct populations of binding and nonbinding species. Structural analysis showed that the tetrasaccharide fraction that bound to the monoclonal antibodies contained one single component with the structure IdoA(2-OSO3)-GlcNSO3 (6-OSO3)-IdoA(2-OSO3)-aManR(6-OSO3), whereas the fraction that did not bind to the antibodies contained a mixture of different structures.

Animals↗
PubMed1987

Structural requirements for the neutralization of heparin-like saccharides by complement S protein/vitronectin.

S protein, a major inhibitor of the assembly of the membrane attack complex of complement, has recently been shown to be identical to the serum spreading factor vitronectin. It also neutralizes the anticoagulant activities of heparin. We have studied the structural requirements for the heparin neutralizing properties of S protein/vitronectin using heparin, heparan sulfate, and heparin oligosaccharides with well defined anticoagulant specificities. The abilities of heparin fractions, Mr 7,800-18,800, with high affinity for antithrombin, and of the International Heparin Standard, to accelerate the inactivation of thrombin and Factor Xa by antithrombin were readily neutralized by S protein/vitronectin. Binding and neutralization of heparin by S protein/vitronectin was inhibited by heparin with low affinity for antithrombin, indicating that S protein/vitronectin can interact with a region on the heparin chain that might serve as a proteinase binding site. S protein/vitronectin efficiently neutralized oligosaccharides of Mr 2,400-7,200, unlike the two other physiologically occurring heparin neutralizing proteins histidine-rich glycoprotein and platelet factor 4. Furthermore, S protein/vitronectin neutralized the anti-Factor Xa activity of a synthetic pentasaccharide comprising the antithrombin-binding sequence of heparin. High molar excess of a synthetic tridecapeptide corresponding to part (amino acids 374-359) of the proposed glycosaminoglycan binding domain of S protein/vitronectin neutralized high affinity heparin and some oligosaccharides, but failed to neutralize the synthetic antithrombin-binding pentasaccharide. Like platelet factor 4, but unlike histidine-rich glycoprotein, S protein/vitronectin readily neutralized the anticoagulant activities of heparan sulfate of Mr approximately 20,000. These findings suggest that S protein/vitronectin may interact through its glycosaminoglycan binding domain(s) with various functional domains of the heparin (heparan sulfate) molecule, including the antithrombin-binding pentasaccharide sequence. Furthermore, the results suggest that S protein/vitronectin may be a physiologically important modulator of the anticoagulant activity of heparin-like material on or near the vascular endothelium.

Antithrombins↗
PubMed1987

Basement-membrane heparan sulphate with high affinity for antithrombin synthesized by normal and transformed mouse mammary epithelial cells.

Basement-membrane proteoglycans, biosynthetically labelled with [35S]sulphate, were isolated from normal and transformed mouse mammary epithelial cells. Proteoglycans synthesized by normal cells contained mainly heparan sulphate and, in addition, small amounts of chondroitin sulphate chains, whereas transformed cells synthesized a relatively higher proportion of chondroitin sulphate. Polysaccharide chains from transformed cells were of lower average Mr and of lower anionic charge density compared with chains isolated from the untransformed counterparts, confirming results reported previously [David & Van den Berghe (1983) J. Biol. Chem. 258, 7338-7344]. A large proportion of the chains isolated from normal cells bound with high affinity to immobilized antithrombin, and the presence of 3-O-sulphated glucosamine residues, previously identified as unique markers for the antithrombin-binding region of heparin [Lindahl, Bäckström, Thunberg & Leder (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 6551-6555], could be demonstrated. A significantly lower proportion of the chains derived from transformed cells bound with high affinity to antithrombin, and a corresponding decrease in the amount of incorporated 3-O-sulphate was observed.

Animals↗
PubMed1987

Structure and antithrombin-binding properties of heparin isolated from the clams Anomalocardia brasiliana and Tivela mactroides.

Heparin with high anticoagulant activity was isolated from the two marine clam species Anomalocardia brasiliana and Tivela mactroides. A large portion of the polysaccharide chains of both preparations bound with high affinity to immobilized antithrombin. Titrations monitored by tryptophan fluorescence showed that clam polysaccharide chains with Mr approximately 22,500 contained up to three binding sites for antithrombin and that the binding constants for the interaction of these chains with antithrombin were higher than those reported for mammalian heparin of comparable size. Structural analysis of clam heparin fractions and subfractions of clam heparin with differing affinity for immobilized antithrombin revealed the presence of large amounts (up to 25-30% of the total disaccharide units) of the 3-O-sulfated saccharide sequences (-GlcNSO3)-GlcA-GlcNSO3(3-OSO3)- and (-GlcNSO3)-GlcA-GlcNSO3(3,6-di-OSO3)-, previously identified as unique markers for the antithrombin-binding region of heparin. The content of these saccharide sequences was found to increase with increasing affinity of the parent polysaccharide for antithrombin. Structural analysis of the clam heparins also demonstrated the occurrence of a novel saccharide sequence, tentatively identified as (-GlcNSO3)-IdA-GlcNSO3(3,6-di-OSO3)-, that has not previously been found in heparin or related polysaccharides. The contents of this latter sequence, at most 3-4% of the total disaccharide units, showed no correlation with the affinity for antithrombin.

Animals↗
PubMed1987

Structure and affinity for antithrombin of heparan sulfate chains derived from basement membrane proteoglycans.

Metabolically 35S- or 3H-labeled heparan sulfate was isolated from murine Reichert's membrane, an extraembryonic basement membrane produced by parietal endoderm cells, and from the basement membrane-producing Engelbreth-Holm-Swarm mouse tumor. The polysaccharides were subjected to structural analysis involving identification of products formed on deamination of the polysaccharides with nitrous acid. The polysaccharide from Reichert's membrane contained N- and O-sulfate groups in approximately equal proportions. It bound almost quantitatively and with high affinity to antithrombin. A high proportion of antithrombin-binding sequence was also indicated by the finding that 3-O-sulfated glucosamine residues accounted for about 10% of the total O-sulfate groups. In contrast, at least 80% of the sulfate residues in the heparan sulfate isolated from the mouse tumor were N-substituents. Only a minor proportion of this polysaccharide bound with high affinity to antithrombin, and no 3-O-sulfated glucosamine residues were detected. These results are discussed in relation to the possible functional role of heparan sulfate in basement membranes.

Animals↗
PubMed1986

Neutralization of heparin-related saccharides by histidine-rich glycoprotein and platelet factor 4.

Heparin and heparin oligosaccharides prepared by nitrous acid depolymerization were fractionated by affinity chromatography on immobilized antithrombin and by gel chromatography. The anticoagulant activities of high affinity heparin of Mr greater than or equal to 7,800 could be readily neutralized by the plasma protein histidine-rich glycoprotein (see also Lijnen, H.R., Hoylaerts, M., and Collen, D. (1983) J. Biol. Chem. 258, 3803-3808), whereas oligosaccharides falling below 18 saccharide units (Mr 5,400) became increasingly resistant to neutralization. An octasaccharide with characteristic marked ability to accelerate the inactivation of Factor Xa by antithrombin retained greater than 50% of its activity even at a histidine-rich glycoprotein/oligosaccharide molar ratio of 500:1. Histidine-rich glycoprotein, like the platelet-derived heparin neutralizing protein platelet factor 4 (Lane, D.A., Denton, J., Flynn, A.M., Thunberg, L. and Lindahl, U. (1984) Biochem J. 218, 725-732), therefore requires interaction with saccharide sequences in addition to the antithrombin-binding pentasaccharide of heparin in order to efficiently express its antiheparin activity. Heparan sulfate isolated from pig intestinal mucosa (HS I, Mr approximately 20,000) and from human aorta (HS II, Mr approximately 40,000) exhibited anti-Factor Xa activities of 180 and 20 units/micromol [corrected], respectively. A fraction corresponding to about 5% of HS I bound with high affinity to immobilized antithrombin and contained all of the anticoagulant activity of the starting material. While these heparan sulfates were readily neutralized by platelet factor 4, they were relatively resistant to neutralization by histidine-rich glycoprotein, although complete neutralization could be attained in the presence of molar excess of this protein. These findings may be of importance in relation (a) to the functional role of endogenous anticoagulant polysaccharides at the vascular wall and (b) to clinical situations in which heparin or heparin-related compounds are administered as exogenous anticoagulants.

Heparin↗
PubMed1986

Structure and function of basement membrane proteoglycans.

Basement membranes contain at least three different proteoglycans. These are a large, low buoyant density heparan sulphate proteoglycan and two smaller, high density proteoglycans with either heparan sulphate or chondroitin sulphate side-chains. The large (Mr 400K-600K and small (Mr 130K) heparan sulphate proteoglycans were purified from the mouse EHS tumour. These proteoglycans are immunologically related by sharing some protein core antigenic determinants (epitopes) but do not cross-react with cell-surface heparan sulphate proteoglycans or with proteoglycans from interstitial connective tissue. This indicates that they belong to a distinct family of proteoglycans. Structural models were developed, based on electron microscopy and analytical ultracentrifugation, demonstrating that the small proteoglycan contains on average four heparan sulphate chains of about 30 nm in length, while the large proteoglycan consists of three long (about 90 nm) heparan sulphate chains connected to one end of a large core protein. Single heparan sulphate chains were isolated from the EHS tumour proteoglycans and from the corresponding proteoglycans from Reichert's membrane of the mouse embryo. The heparan sulphate from Reichert's membrane bound to antithrombin with high affinity and was found to contain the unique 3-O-sulphated glucosamine residue previously identified in the antithrombin-binding region of heparin. The EHS tumour heparan sulphate showed a higher N-/O-sulphate ratio and a lower affinity for antithrombin.

Animals↗