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S A Cederholm-Williams

Publications and source records attributed to S A Cederholm-Williams.

At least 19 recordsLinked to original sources
PubMed1998

Evidence that the conformation of unliganded human plasminogen is maintained via an intramolecular interaction between the lysine-binding site of kringle 5 and the N-terminal peptide.

Human Glu-plasminogen adopts at least three conformations that provide a means for regulating the specificity of its activation in vivo. It has been proposed previously that the closed (alpha) conformation of human Glu-plasminogen is maintained through physical interaction of the kringle 5 domain and a lysine residue within the N-terminal peptide (NTP). To examine this hypothesis, site-directed mutagenesis was used to generate variant proteins containing substitutions either for aspartic acid residues within the anionic centre of the kringle 5 domain or for conserved lysine residues within the NTP. Size-exclusion HPLC and rates of plasminogen activation by urokinase-type plasminogen activator were used to determine the conformational states of these variants. Variants with substitutions within the kringle 5 lysine-binding site demonstrated extended conformations, as did variants with alanine substitutions for Lys50 and Lys62. In contrast, molecules in which NTP residues Lys20 or Lys33 were replaced were shown to adopt closed conformations. We conclude that the lysine-binding site of kringle 5 is involved in maintaining the closed conformation of human Glu-plasminogen via an interaction with the NTP, probably through Lys50 and/or Lys62. These conclusions advance the current model for the initial stages of fibrinolysis during which fibrin is thought to compete with the NTP for the kringle 5 lysine-binding site.

Amino Acid Substitution↗
PubMed1994

Fibrin glue.

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Consumer Product Safety↗
PubMed1993

Neutralizing antibodies to streptokinase four years after intravenous thrombolytic therapy.

Neutralization antibodies to streptokinase increase to high levels within several days of administration. It is not known how long these high levels persist. The time course of antibody levels needs to be further characterized owing to the increasing need to readminister thrombolytic therapy, and to the possibility that these antibodies may compromise the safety and efficacy of a further dose of streptokinase or streptokinase-containing compounds. In this study, paired streptokinase neutralization titers (in vitro functional assay) and specific antistreptokinase immunoglobulin G (IgG) antibody levels were measured in 145 patients who received streptokinase between 10 and 48 months previously. Serologic evidence of recent streptococcal infection was also sought. Neutralization titers sufficient to inactivate a conventional dose of 1,500,000 units of streptokinase were still present in 50% of patients (95% confidence interval 36-64) at 24 months, 48% (34-62) at 36 months, and 51% (37-71) at 48 months after streptokinase administration. Levels of specific antistreptokinase IgG antibodies also remained constant over the 1- to 4-year period. Neutralization titers were weakly correlated with specific IgG levels (r = 0.35). Antistreptolysin titers > or = 250 and > or = 333 IU/ml were present in 30% (24-38) and 12% (8-18) of these patients, respectively. Neutralization titers were not correlated with antistreptolysin titers. Neutralizing antibodies (assessed by an in vitro functional assay) remained high in 51% of patients 4 years after intravenous streptokinase administration. It is not known whether persisting high in vitro neutralization titers affect the efficacy and safety of repeat administration of streptokinase or streptokinase-containing compounds.

Aged↗
PubMed1992

The compact domain conformation of human Glu-plasminogen in solution.

A complete understanding of the accelerating mechanisms of plasminogen activation and fibrinolysis necessarily requires structural information on the conformational forms of plasminogen. Given the absence of high-resolution structural data on plasminogen the use of lower resolution approaches has been adopted. Two such approaches have previously indicated a compact conformation of Glu-plasminogen (Tranqui, L., Prandini, M., and Chapel, A. (1979) Biol. Cellulaire, 34, 39-42; Bányai, L. and Patthy, L. (1985) Biochim. Biophys. Acta, 832, 224-227) whereas a third has suggested a fairly extended conformation (Mangel, W., Lin, B. and Ramakrishnan, V. (1990) Science, 248, 69-73). Native Glu-plasminogen has been investigated using small-angle X-ray scattering (SAXS) experiments. It is concluded that this molecule in solution is compact (radius of gyration, RG 3.05 +/- 0.02 nm and maximum intramolecular distance, Im 9.1 +/- 0.3 nm) and that the data are consistent with the right-handed spiral structure observed using electron microscopy by Tranqui et al. (1979). A spiral structure of native plasminogen would have important implications for the conformational response of plasminogen to fibrin and concomitant stimulation of plasminogen activation.

Computer Simulation↗
PubMed1992

A hybrid protein of urokinase growth-factor domain and plasminogen-activator inhibitor type 2 inhibits urokinase activity and binds to the urokinase receptor.

The binding of urokinase-type plasminogen activator (uPA) to its specific cell-surface receptor (uPAR) localises the proteolytic cascade initiated by uPA to the pericellular environment. Inhibition of uPA activity or prevention of uPA binding to uPAR might have a beneficial effect on disease states wherein this activity is deregulated, e.g. cancer and some inflammatory diseases. To this end, a bifunctional hybrid molecule consisting of the uPAR-binding growth-factor domain of uPA (amino acids 1-47; GFuPA) at the N-terminus of plasminogen-activator inhibitor type 2 (PAI-2) was produced in Saccharomyces cerevisiae. The purified protein inhibited uPA with kinetics similar to placental or recombinant PAI-2 and was also found to bind to U937 cells and to FL amnion cells. GFuPA-PAI-2 competed with uPA, the N-terminal fragment of uPA and a proteolytic fragment of uPA (amino acids 4-43) in cell binding experiments, indicating that the molecule bound to the cells via uPAR. Hence, both the uPA-inhibitory and uPAR-binding domains of the hybrid molecule were functional, demonstrating the feasibility of the novel concept of introducing an unrelated, functional domain onto a member of the serine-protease-inhibitor superfamily.

Amino Acid Sequence↗
PubMed1992

Plasminogen activator in human tears.

Measurements were made of the nature and levels of plasminogen activator in human tears using, as a model of inflammation, patients undergoing cataract surgery. Tissue plasminogen activator (t-PA) but not urokinase plasminogen activator (u-PA) was found in tears. A wide variation in the range of t-PA in pre-operative tears was found. In those patients not receiving per-operative subconjunctival betamethasone a significant rise in t-PA was found in tears on the first post-operative day over pre-operative levels. A significant fall was noted in those receiving per-operative subconjunctival betamethasone.

Betamethasone↗
PubMed1992

Plasminogen binding sites in normal human skin.

Plasminogen is detected in the basal cell layer of the epidermis, keratinocytes can generate plasminogen activators and it is suggested that the generation of plasmin may facilitate keratinocyte division, migration and differentiation. In this study we have investigated the characteristics of plasminogen binding sites in normal human epidermis. It was found that 6-aminohexanoic acid and benzamidine displaced endogenous epidermal plasminogen from the basal layer suggesting that endogenous plasminogen binds initially via the kringle 5 aminohexyl (AH) site. Plasminogen binding sites in epidermis were further investigated by displacing endogenous plasminogen and incubating sections with exogenously added glu-plasminogen, lys-plasminogen and plasmin or the isolated plasminogen fragments kringles 1-3, kringle 4 and kringle 5L. The results suggest that the uptake of plasminogen involves primary interaction with the kringle 5AH site and a secondary interaction with lysine binding sites of kringles 1-3. Cell binding is not dependent upon additional reactions of the plasmin active centre.

Aminocaproic Acid↗
PubMed1992

Secretion of urokinase and tissue-plasminogen activator by epidermal cells in the presence of psoriatic fibroblast-conditioned medium.

The present study examined secretion of urokinase and tissue-plasminogen activator by epidermal cells in the presence of psoriatic or uninvolved skin fibroblast-conditioned medium. Using zymographic analyses, a 54kD lysis band and a small 110kD band derived from urokinase could be detected in the harvest fluid from keratinocytes treated with both psoriatic and uninvolved fibroblast-conditioned medium, as well as very weak lysis bands of 63kD and 120kD derived from tissue-plasminogen activator in the harvest fluid treated with psoriatic fibroblast-conditioned medium, but not with uninvolved fibroblast-conditioned medium.

Adult↗
PubMed1992

Plasminogen: a structural review.

Plasminogen is the zymogen form of plasmin, a broad specificity serine protease whose activity contributes to a variety of normal and pathological conditions, including intravascular thrombolysis and extracellular proteolysis. Plasminogen contains seven structural units or 'domains', each of which confer specific properties on the molecule. The kringle domains possess fibrin-binding functions and, together with the N-terminal peptide, regulate the ability of plasminogen to adopt at least three dissimilar conformations. These conformational forms influence the rate of formation, following activation by plasminogen activators, of the plasmin active site within its C-terminal serine protease domain. Structural and functional analogies are postulated between these plasminogen structures and the conformations of other proteins related by sequence homology.

Amino Acid Sequence↗
PubMed1991

Cell adhesion in Hailey-Hailey disease and Darier's disease: immunocytological and explant-tissue-culture studies.

The pathogenesis of Hailey-Hailey disease and Darier's disease was investigated using immunocytological and explant-tissue-culture techniques. There was breakdown of the intercellular adhesions between keratinocytes in explants from clinically uninvolved skin of patients with Hailey-Hailey disease or Darier's disease. The major desmosomal components were present in the cultures and were expressed in a punctate peripheral pattern at cell-cell contact sites, but there was diffuse staining of acantholytic cells. Plasminogen, which is expressed by basal keratinocytes in normal skin, was detected in association with suprabasal acantholytic cells in skin biopsies from these diseases. Plasminogen was reversibly displaced from the cells by 6-aminohexanoic acid, suggesting that binding is mediated by a reaction with the lysine receptor on the plasminogen molecule. Plasminogen was also detected in separating cells in explant cultures and there was cytoplasmic expression of the plasminogen activator urokinase by these cells. These abnormalities are not unique to either disease and do not account for the phenotypic differences between Darier's disease and Hailey-Hailey disease, but plasmin generation may have a role in perpetuating cell separation.

Adult↗
PubMed1989

Darier's disease: an immunohistochemical study using antibodies to proteases.

The expression of plasminogen activators, plasminogen and fibrinogen was investigated in 10 specimens of normal skin and in the involved skin of seven males with Darier's disease, using immunohistochemical techniques. Changes in the localization of proteases were found in the involved skin of Darier's disease, plasminogen being expressed by suprabasal cells and fibrinogen being detected in the keratotic plug.

Darier Disease↗
PubMed1987

Tissue plasminogen activators in breast cancer.

Increased levels of tissue fibrinolytic activity have been detected in some malignant tumours and they have been implicated in metastatic spread. We have investigated tissue plasminogen activator (tPA) and urokinase (UK) in 26 breast carcinomas and 13 benign breast biopsies. Tissue extracts were analysed for overall fibrinolytic activity on fibrin plates and by fibrin-overlay zymography after electrophoresis on SDS-PAG. Supernatants of the extracts were analysed by an antigenic immunoassay (ELISA) and a functional bioimmunoassay (BIA) using polyclonal antibodies. Total ELISA and BIA results correlated (P less than 0.001) and all the tissues contained similar tPA levels. Malignant extracts contained significantly increased UK compared with benign extracts (1.60 +/- 0.37 iu, 0.36 +/- 0.16 iu; P less than 0.002). Zymography showed no high molecular weight inhibitor complexes and UK was almost exclusively confined to the malignant tissues (P much less than 0.02). The results suggest that malignant transformation of breast tissue is associated with the significantly increased production of UK. This may be responsible for the characteristics of malignancy or it may be a growth factor.

Breast Neoplasms↗
PubMed1987

An in vitro model for the study of acute release of von Willebrand factor from human endothelial cells.

An in vitro model is described which utilizes human umbilical vein endothelial cells cultured on plastic microcarrier spheres and perfused with serum-free medium. This model was used to study the acute release of von Willebrand factor following stimulation of the cells with putative agonists. Thrombin, plasmin and interleukin-1 were found to release von Willebrand factor. Adrenaline and bradykinin also stimulated release but only at high dosage. 1-desamino-8-D-arginine vasopressin (DDAVP) was inactive.

Bradykinin↗
PubMed1987

Indications of vascular endothelial cell dysfunction in systemic lupus erythematosus.

Fibrinolytic and other factors have been measured in 73 patients with systemic lupus erythematosus or related conditions to determine whether clinical thrombosis, a common feature of these disorders, is associated with defective fibrinolysis. Twenty five of 72 (35%) patients, compared with two of 22 (9%) controls, showed a low level of plasminogen activator activity in response to venous occlusion, suggesting decreased fibrinolytic potential. In addition, mean plasma levels of von Willebrand factor antigen and fibronectin were markedly raised in the patients (mean (SD) 384.5 (277)% and 727 (436) mg/l respectively) compared with healthy controls (100 (50)% and 306 (65) mg/l). These data suggest a degree of endothelial cell dysfunction. No clear correlation was found between a history of thrombosis and any plasma factor measured, except for prolongation of clotting tests suggestive of the 'lupus anticoagulant'.

Adult↗