Yeast protein glycation in vivo by methylglyoxal. Molecular modification of glycolytic enzymes and heat shock proteins

Protein glycation by methylglyoxal is a nonenzymatic post-translational modification whereby arginine and lysine side chains form a chemically heterogeneous group of advanced glycation end-products. Methylglyoxal-derived advanced glycation end-products are involved in pathologies such as diabetes and neurodegenerative diseases of the amyloid type. As methylglyoxal is produced nonenzymatically from dihydroxyacetone phosphate and d-glyceraldehyde 3-phosphate during glycolysis, its formation occurs in all living cells. Understanding methylglyoxal glycation in model systems will provide important clues regarding glycation prevention in higher organisms in the context of widespread human diseases. Using Saccharomyces cerevisiae cells with different glycation phenotypes and MALDI-TOF peptide mass fingerprints, we identified enolase 2 as the primary methylglyoxal glycation target in yeast. Two other glycolytic enzymes are also glycated, aldolase and phosphoglycerate mutase. Despite enolase's activity loss, in a glycation-dependent way, glycolytic flux and glycerol production remained unchanged. None of these enzymes has any effect on glycolytic flux, as evaluated by sensitivity analysis, showing that yeast glycolysis is a very robust metabolic pathway. Three heat shock proteins are also glycated, Hsp71/72 and Hsp26. For all glycated proteins, the nature and molecular location of some advanced glycation end-products were determined by MALDI-TOF. Yeast cells experienced selective pressure towards efficient use of d-glucose, with high methylglyoxal formation as a side effect. Glycation is a fact of life for these cells, and some glycolytic enzymes could be deployed to contain methylglyoxal that evades its enzymatic catabolism. Heat shock proteins may be involved in proteolytic processing (Hsp71/72) or protein salvaging (Hsp26).     

Isolation and functional characterization of the heavy and light chains of human tissue-type plasminogen activator

Two-chain tissue-type plasminogen activator (t-PA), which consists of a heavy chain (Mr congruent to 38,000) and a light chain (Mr congruent to 31,000) connected by a disulfide bridge, was reduced with 2-mercaptoethanol and then air-reoxidized at a low protein concentration and carboxamidomethylated. The two chains were separated by means of zinc chelate-agarose, which was found to bind the light chain selectively. The light chain was fully active on the tripeptide substrate H-D-isoleucyl-L-prolyl-L-arginine p-nitroanilide (S-2288) and partially active on plasminogen. The plasminogen activator activity of the light chain was, in contrast to that of two-chain t-PA, not stimulated by fibrin or fibrinogen fragments. Fibrin-agarose chromatography of radiolabeled chains showed that only the heavy chain bound to fibrin. These results indicate that the active site-containing light chain in t-PA needs the heavy chain for fibrin stimulation of its plasminogen activator activity.     

Induction of Urokinase-Type Plasminogen Activator in Rat Facial Nucleus by Axotomy of the Facial Nerve

Abstract: The response of plasminogen activator activity in the CNS to peripheral nerve axotomy was examined in vivo. After transection of the rat facial nerve, a transient increase in plasminogen activator activity was observed in the facial nucleus on the operated side with maximal activity 3–5 days after lesion. This activity was inhibited by the urokinase-specific inhibitor amiloride but not by antibodies against tissue plasminogen activator. The molecular mass of the induced form of plasminogen activator was estimated to be ∼48 kDa. An in vitro assay of plasminogen hydrolysis also demonstrated an increase in amiloride-sensitive plasminogen activator activity in facial nerve extracts following facial nerve axotomy. These data indicate that the plasminogen activator activity induced in the facial nucleus following axotomy of facial motoneurons is of the urokinase type. It is suggested that the urokinase-type plasminogen activator might play a role in the events accompanying injury and regeneration in the facial nucleus following motoneuron lesion.     

Plasminogen activation in diabetes mellitus. Kinetic analysis of plasmin formation using components isolated from the plasma of diabetic donors

Two components of the fibrinolytic system, plasminogen and the vascular plasminogen activator, have been isolated to apparent homogeneity from the post-venous occlusion plasma of three diabetic patients (hemoglobin A1C greater than 7%) and of one nondiabetic control person. Plasminogen activation was studied for each person separately in the absence and presence of CNBr fragments of fibrinogen. Activation of diabetic plasminogen by urokinase was not significantly altered as compared to the activation of control plasminogen. The same was found when diabetic plasminogen was activated by control vascular plasminogen activator in the presence of fibrinogen fragments but only at plasminogen concentrations below 10-30 nM; at higher substrate concentrations, however, plasminogen activation was impaired in a pattern resembling substrate inhibition. Activation of control plasminogen by diabetic vascular plasminogen activator was completely impaired in the absence of fibrinogen fragments. Addition of fibrinogen fragments stimulated plasmin formation by diabetic vascular plasminogen activator resulting in kinetic constants which were similar to the activation of control plasminogen by control vascular plasminogen activator in the absence of fibrinogen fragments (Km = 7.5 microM, kcat = 0.05 S-1). Addition of fibrinogen fragments in controls decreased Km values to less than 0.1 microM. Despite addition of fibrinogen fragments the rate of plasmin formation from diabetic plasminogen by diabetic vascular plasminogen activator isolated from the same diabetic donor was so small that kinetic constants could not be calculated.     

Extracellular matrix produced by cultured corneal and aortic endothelial cells contains active tissue-type and urokinase-type plasminogen activators

Incubation of plasminogen with the subendothelial extracellular matrix (ECM) synthesized by cultured bovine corneal and aortic endothelial cells resulted in generation of fibrinolytic activity, indicated by proteolysis of ¹²⁵I-fibrin in a time-and dose-dependent manner. Both tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA) were identified in the ECM by fibrin zymography, immunoblotting, and inhibition of plasminogen activation by anti-u-and anti-t-antibodies. Most of the ECM-resident plasminogen activator (PA) activity did not originate from intracellular PA release occurring when the endothelial cells were lyzed and the ECM exposed, since a comparable amount of PA was associated with the ECM when the cells were lyzed with Triton X-100 or removed intact by treatment with 2 M urea. Active u-PA and t-PA were released from ECM by treatment with heparanase (endo-β-D-), indicating that some of the ECM-resident PA activity is sequestered by heparan sulfate side chains. These results indicate that both u-PA and t-PA produced by endothelial cells are firmly sequestered in an active form by the subendothelial ECM. It is suggested that ECM-resident plasminogen activators participate in sequential matrix degradation during cell invasion and tumor metastasis. PA activity may also function in release of ECM-bound growth factors (i.e., basic fibroblast growth factor) and activation of proenzymes (i.e., prothrombin), resulting in modulation of the ECM growth-promoting and thrombogenic properties. © 1993 Wiley-Liss, Inc.     

Plasminogen-activator of the arterial wall in occluded arteries

The plasminogen activator in 117 specimen of 20 coronary and 29 pulmonary arteries occluded completely by thrombi or emboli within the adventitia and intima was studied using TODD's histochemical method. 39 cadavers were used, 1--18 hours post mortem from subjects aged from 45 to 88 years. In occluded arteries both coronary and pulmonary the plasminogen activator activity was decreased in comparison with normal and atherosclerotic patients. In coronary and pulmonary arterial thrombi a low grade focal activity of plasminogen activator was detected. It is assumed that the decrease of plasminogen activator in the occluded human arterial wall is due to the impaired oxygen supply of the vessel wall and to the consumption of the plasminogen activator for thrombus lysis. These mechanisms are likely to influence the plasminogen activator for a certain and prolonged time, since there were no changes of fibrinolysis within the vessel wall of arteria carotis in rats where an acute thrombosis was elicited by means of an electric current.     

Role of polyamines in the stimulation of synthesis and secretion of plasminogen activator from bovine aortic endothelial cells

The effects of the polyamines putrescine (PUT), spermidine (SPD), and spermidine (SPM) on the secretion of plasminogen activator (PA) and plasminogen activator inhibitor (PAI) were evaluated using cultured bovine aortic endothelial cells. All three polyamines enhanced PA secretion in a time- and dose-dependent manner, with a potency rank order of SPM greater than SPD greater than PUT. The PA stimulation required both RNA and protein synthesis, as evidenced by inhibition of polyamine-induced PA secretion by actinomycin D and cycloheximide. The inhibitors of polyamine biosynthesis methylglyoxal bis-(guanylhydrazone) (MGBG) and dl-(difluoromethyl) ornithine (DFMO) alone did not affect basal or polyamine-induced PA secretion, with the exception that MGBG reduced the effect of PUT. Polyamine-treated cells enhanced secretions of both tissue-type and urokinase-type PA. The results of the present study suggest that polyamines may play a role in the regulation of PA synthesis and secretion and that this function can be modified under pathophysiological conditions affecting cellular and tissue levels of polyamines.     

Inhibition of human MDA-MB-231 breast cancer cell invasion by matrix metalloproteinase 3 involves degradation of plasminogen.

Matrix metalloproteinase (MMP)-3 inhibited human MDA-MB-231 breast cancer cell invasion through reconstituted basement membrane in vitro. Inhibition of invasion was dependent upon plasminogen and MMP-3 activation, was impaired by the peptide MMP-3 inhibitor Ac-Arg-Cys-Gly-Val-Pro-Asp-NH2 and was associated with: rapid MMP-3-mediated plasminogen degradation to microplasminogen and angiostatin-like fragments; the removal of single-chain urokinase plasminogen activator from MDA-MB-231 cell membranes; impaired membrane plasminogen association; reduced rate of tissue plasminogen activator (t-PA) and membrane-mediated plasminogen activation; and reduced laminin-degrading capacity. Purified human plasminogen lysine binding site-1 (kringles 1-3) exhibited a similar capacity to inhibit MDA-MB-231 invasion, impair t-PA and cell membrane-mediated plasminogen activation and impair laminin degradation by plasmin. Our data provide evidence that MMP-3 can inhibit breast tumour cell invasion in vitro by a mechanism involving plasminogen degradation to fragments that limit plasminogen activation and the degradation of laminin. This supports the hypothesis that MMP-3, under certain conditions, may protect against tumour invasion, which would help to explain why MMP-3 expression, associated with benign and early stage breast tumours, is frequently lost in advanced stage, aggressive, breast disease.     

Fibrin autography of plasminogen activator by electrophoretic transfer into fibrin agar gels

An electrophoretic modification of the conventional fibrin autography that can be used for the detection of plasminogen activators (urokinase type and tissue type) and fibrin-degrading enzymes in complex biological fluids is described. After separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the proteins and the substrate plasminogen are transferred electrophoretically into the fibrin indicator gel, resulting in an efficient transfer of proteinases as well as high resolution and contrast of fibrinolytic zones caused by plasminogen activator activity. Picogram amounts of human urokinase type plasminogen activator (about 0.002 International Unit) are still detectable. The technique is also applicable to reversed fibrin autography for plasminogen activator inhibitors.     

Purification and partial characterization of plasminogen activator from human uterine tissue.

A procedure was developed for the purification of a plasminogen activator from human uterine tissue. It involves six consecutive steps: (1) extraction of the plasminogen activator from delipidated uterine tissue with 0.3 M potassium acetate buffer, pH 4.2; (2) ammonium sulphate precipitation; (3) zinc chelate-agarose chromatography; (4) n-butyl-agarose chromatography; (5) concanavalin A-agarose chromatography; and (6) gel filtration on Sephadex G-150. The specific activity of the final plasminogen activator preparation was increased by a factor 4500 as compared with the crude extract. The purified plasminogen activator showed a strong tendency to adsorb to surfaces. This could be effectively prevented by Tween-80. The molecular weight of the plasminogen activator was 64 000 as estimated by gel filtration in 1.0 M NaCl and 69 000 as estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The plasminogen activator consisted of two chains (molecular weights 31 000 and 38 000) connected by disulphide bridges. The smallest chain contained the serine residue of the active site as deduced from the incorporation of the tritium label of [3H]diisopropylphosphofluoridate.     

Sialylated carbohydrate chains of recombinant human glycoproteins expressed in Chinese hamster ovary cells contain traces of N-glycolylneuraminic acid

HPLC analysis of sialic acids released from recombinant variants of human tissue plasminogen activator, human chimeric plasminogen activator, human erythropoietin, and human follitropin, expressed in Chinese hamster ovary cells, demonstrates for each glycoprotein the presence of N-acetylneuraminic acid and N-glycolylneuraminic acid in a ratio of 97:3. Structural analysis by 500 MHz1H-NMR spectroscopy, of the enzymatically released N-linked carbohydrate chains of chimeric plasminogen activator and of erythropoietin, showed that alpha 2-3 linked N-glycolylneuraminic acid can occur in different N-acetyllactosamine type antennary structures.     

Stimulation of tPA-dependent provisional extracellular fibrin matrix degradation by human recombinant soluble melanotransferrin

Tissue-type plasminogen activator (tPA) and its substrate plasminogen (Plg) are key components in the fibrinolytic system. We have recently demonstrated, that truncated human recombinant soluble melanotransferrin (sMTf) could stimulate the activation of Plg by urokinase plasminogen activator and inhibit angiogenesis. Since various angiogenesis inhibitors were shown to stimulate tPA-mediated plasminogen activation, we examined the effects of sMTf on tPA-dependent fibrinolysis. This study demonstrated that sMTf enhanced tPA-activation of Plg by 6-fold. sMTf also increased the release of [125I]-fibrin fragments by tPA-activated plasmin. Moreover, we observed that the interaction of sMTf with Plg provoked a change in the fibrin clot structure by cleaving the fibrin alpha and beta chains. Overall, the present study shows that sMTf modulates tPA-dependent fibrinolysis by modifying the clot structure. These results also suggest that sMTf properties could involve enhanced dissolution of the provisional extracellular fibrin matrix.     

Purification and characterization of a stimulator of plasmin generation from the antiangiogenic agent Neovastat: identification as immunoglobulin kappa light chain

We have recently shown that Neovastat, an antiangiogenic extract from shark cartilage, stimulates the in vitro activation of plasminogen by facilitating the tissue-type plasminogen activator (tPA)-dependent conversion of plasminogen to plasmin. In this report, we describe the purification and characterization of the stimulatory molecules. Neovastat was subjected to a three-step purification procedure including gel filtration, preparative isoelectric focusing, and preparative SDS-PAGE. Two 28-kDa proteins with pIs of approximately 4.5 and 6.5 were purified to apparent homogeneity and identified as immunoglobulin (Ig) kappa light chains by N-terminal microsequencing. Ig light chains do not directly stimulate the activity of tPA or plasmin, suggesting a mechanism of action involving an interaction with plasminogen. Kinetic analysis showed that both Ig light chains accelerate the in vitro tPA-dependent conversion of plasminogen in plasmin by increasing the affinity of tPA for plasminogen by 32- and 38-fold (Km decrease from 456 nM to 12-14 nM). Shark Ig light chains also stimulated the degradation of fibrin by the tPA/plasminogen system in an in vitro assay. A direct interaction between Ig light chains and plasminogen (KA=4.0-5.5 x 10(7) M(-1); KD=18-25 nM) and with tPA (KA=2.8 x 10(7) M(-1); KD=36 nM) was demonstrated using real time binding measured by surface plasmon resonance. Ig light chain is the first molecule associated with the antiangiogenic activity of Neovastat to be purified and identified.     

A covalent molecular weight approximately 92,000 hybrid plasminogen activator derived from human plasmin fibrin-binding and tissue plasminogen activator catalytic domains

A covalent hybrid plasminogen activator was prepared from the sulfhydryl forms of the NH2-terminal heavy (A) chain of human plasmin (PlnA) containing the fibrin-binding domain and the COOH-terminal B chain of tissue plasminogen activator (t-PAB) containing the catalytic domain. The sulfhydryl form of PlnA [PlnA(SH)2] was isolated from reduced Lys-2-plasmin on an L-lysine-substituted Sepharose column, and the sulfhydryl form of t-PAB [t-PAB(SH)] was prepared from reduced two-chain tissue plasminogen activator (t-PA) by removing the tissue plasminogen activator NH2-terminal A chain (t-PAA) on an L-lysine-substituted Sepharose column from the chain mixture. The specific plasminogen activator activity, with soluble fibrin, of the isolated t-PAB(SH) chain was determined to be 62,700 international units (IU)/mg of protein, about 13% of the specific plasminogen activator activity of the parent t-PA. The PlnA(SH)2 and the t-PAB(SH) chains were mixed in a 1:1 molar ratio, and hybridization (reoxidation) was allowed to proceed by first dialyzing out the reducing agent at 4 degrees C and then concentrating the mixture. The time for maximum hybridization, or formation of the covalent hybrid activator, was 6 days, as determined by both specific plasminogen activator activity, with soluble fibrin, and specific amidolytic activity; sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed the continual formation of an Mr approximately 92,000 hybrid. The covalent PlnA-t-PAB hybrid activator was isolated from the 6-day hybridization mixture by a two-step affinity chromatography method.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interaction of urokinase with specific receptors stimulates mobilization of bovine adrenal capillary endothelial cells

On the basis of 125I-labeled plasminogen activator binding analysis we have found that bovine adrenal capillary endothelial cells have specific receptors for human urinary-type plasminogen activator on the cell membrane. Each cell exposes about 37,000 free receptors with a Kd of 0.8958 x 10(-9) M [corrected]. A monoclonal antibody against the 17,500 proteolytic fragment of the A chain of the plasminogen activator, not containing the catalytic site of the enzyme, impaired the specific binding, thus suggesting the involvement of a sequence present on the A chain in the interaction with the receptor, as previously shown in other cell model systems. Both the native molecule and the A chain are able to stimulate endothelial cell motility in the Boyden chamber, when used at nanomolar concentrations. The use of the same monoclonal antibody that can inhibit ligand-receptor interaction can impair the plasminogen activator and A-chain-induced endothelial cell motility, suggesting that under the conditions used in this in vitro model system, the motility of bovine adrenal capillary endothelial cells depends on the specific interaction of the ligand with free receptors on the surface of endothelial cells.     

Involvement of both heparanase and plasminogen activator in lymphoma cell-mediated degradation of heparan sulfate in the subendothelial extracellular matrix

The effect of plasminogen on the ability of highly metastatic ESb mouse lymphoma cells to degrade heparan sulfate (HS) in the subendothelial extracellular matrix (ECM) was studied. A metabolically sulfate-labeled ECM was incubated with the lymphoma cells, and labeled degradation products were analyzed by gel filtration on Sepharose 6B. Heparanase-mediated release of low-Mr (0.5 less than Kav less than 0.85) HS cleavage products was stimulated fourfold in the presence of plasminogen. Incubation of plasminogen alone with the ECM resulted in its conversion into plasmin, which released high-Mr (Kav less than 0.33) labeled proteoglycans from the ECM. Heating the ECM (80 degrees C, 1 hr) abolished its ability to convert plasminogen into plasmin, yet plasminogen stimulated, through its activation by the ESb plasminogen activator, heparanase-mediated release of low-Mr HS fragments. Heparin inhibited both the basal and plasminogen-stimulated degradation of HS side chains but not the total amount of labeled material released from the ECM. In contrast, aprotinin inhibited the plasminogen-stimulated release of high- as well as low-Mr material. In the absence of plasminogen, degradation of heated ECM by ESb cells was completely inhibited by aprotinin, but there was only a partial inhibition of the degradation of native ECM and no effect on the degradation of soluble HS proteoglycan. These results demonstrate that proteolytic activity and heparanase participate synergistically in the sequential degradation of ECM HS and that the ESb proteolytic activity is crucial for this degradation when the ECM-associated protease is inactivated. Plasminogen may serve as a source for the proteolytic activity that produces a more accessible substrate to the heparanase.     

Differences between uterine and melanoma forms of tissue plasminogen activator

Tissue plasminogen activator purified from human uterine tissue exhibits differences in N-terminal starting positions in relation to the melanoma cell plasminogen activator usually studied. A new starting position is compatible with an additional N-terminal processing apart from those already known. Like the melanoma activator, the uterine activator was found to yield protein chains starting at either of two positions. One of these was identical between uterine and melanoma activators, whereas the other was unique in each case. The most abundant starting position for the uterine preparation was at a valine residue, apparently from cleavage of a Gln-Val bond, and corresponding to Val-7 of the longest form of the melanoma activator chain.     

Role of plasminogen activators in peritoneal adhesion formation

Intra-abdominal adhesion formation is a major complication of serosal repair following surgery, ischaemia or infection, leading to conditions such as intestinal obstruction and infertility. It has been proposed that the persistence of fibrin, due to impaired plasminogen activator activity, results in the formation of adhesions between damaged serosal surfaces. This study aimed to assess the role of fibrinolysis in adhesion formation using mice deficient in either of the plasminogen activator proteases, tissue-type plasminogen activator (tPA) or urokinase-type plasminogen activator (uPA). We hypothesize that, following serosal injury, mice with decreased peritoneal fibrinolytic activity will be more susceptible to adhesion formation. Adhesion formation was induced in tPA- and uPA-deficient and wild-type mice following either surgical trauma to the serosa with haemorrhage and acute or chronic intraperitoneal inflammation. Adhesion formation was assessed from 1 to 4 weeks post-injury. Mice deficient in tPA were more susceptible to adhesion formation following both a surgical insult and a chronic inflammatory episode compared with uPA-deficient and wild-type mice. In addition, the time of maximal adhesion formation varied depending on the nature of the initial insult. It is proposed that the persistence of fibrin due to decreased tPA activity following surgery or chronic inflammation plays a major role in peritoneal adhesion formation.     

Isolation and characteristics of urokinase-type plasminogen activator from a culture of human embryo lung fibroblasts

Plasminogen activator from conditioned medium of human embryonal lung fibroblasts was purified by phosphocellulose P11 chromatography, followed by p-aminobenzamidine-agarose chromatography. Two forms of plasminogen activators were separated by chromatography on the heparin-sepharose. The high molecular weight form (53 kDa) with specific activity 130 000 IU/mg consists of two polypeptide chains (31 kDa and 20 kDa) and exhibits strong affinity for fibrin-celite, lysine-sepharose and heparin-sepharose. The low molecular weight form (32 kDa, 190 000 IU/mg) also binds to these sorbents, but more weakly, and its properties are very similar to those of low molecular weight urokinase. Activity of both forms of plasminogen activators are inhibited by monoclonal antibodies against urokinase. A number of enzymological chromatographic and immunological properties indicates, that the plasminogen activator from lung fibroblasts is of urokinase type.