Direct determination of the sequence recognition requirements of the SH2 domains of SH-PTP2

SH-PTP2 is a widely-expressed protein tyrosine phosphatase with two tandem SH2 (src homology 2) domains and a C-terminal catalytic domain. Glutathione S-transferase fusions of the SH2 domains alone and of a catalytically inactive full-length mutant were made, and binding assays were developed using the purified fusion proteins to directly determine what residues are involved in the recognition of binding targets by the SH2 domains. The binding kinetics of the SH2 domains to a phosphotyrosyl-containing peptide of the sequence surrounding Tyr1009 of the platelet-derived growth factor receptor (PDGFR) beta subunit [DTSSVL(pY)TAVQPN] were determined by surface plasmon resonance, confirming that this is a high-affinity binding ligand. Using various N- and C-terminal truncations of this peptide as competitors in the binding assays, the minimum peptide that served as a high-affinity binding ligand was found to be VL(pY)TAV. Systematic Ala substitutions of this peptide indicated that in addition to the phosphotyrosine (pY), the critical residues for recognition and binding are at pY + 1 and pY + 3 as previously reported, and notably at pY-2 as well. Binding competition results with these and other PDGFR, IRP, and IRS-1 peptides suggested some general rules for sequence recognition by the SH2 domains of SH-PTP2. Peptides that bind to the SH2 domains in the binding assays were also found to stimulate the phosphatase activity of SH-PTP2.

Reactivity and the fate of some composite bioimplants based on collagen in connective tissue

Three composite materials based on collagen gel prepared with ISC40 and supplemented with the tripeptide glycine-histidine-lysine (GHK) mixed with bioglass (BAS O), pure hydroxyapatite (grain: 0.5-1.0 microns and 13-23 microns) and shredded beef bone were tested in the laboratory rat and guinea-pig. In the course of 49 d, no signs of infectious inflammation or incompatibility were observed around subcutaneously installed bioimplants. Particles of glass and hydroxyapatite became subject to phagocytosis. Bone fragments were completely resorbed, and no signs of osteogenic activity were detected in the neighbourhood.

[The effect of collagenous gel on endoprosthesis anchoring.]

Collagen supplemented with tripeptide (gly-his-lys) was tested for implantation of cervicocapital endoprostheses of the hip in adult minipigs. In anaesthesia bone marrow cavity was filled up with the collagenous gel and then one of the two endoprosthesis types, produced by BMT Poldi Kladno was implanted. The experimental animals were killed eight, nine and ten weeks after operation. The femors were removed and roentgenologically and histologically examined. When bone marrow cavity was filled up with collagenous gel, anchoring of endoprosthesis with newly formed tissue was accelerated in comparison with those without gel. In the presence of fatty bone marrow residues healing process was disturbed. It cannot be excluded that this fact might have an effect on long term effective endoprosthesis anchoring. Key words: non-cemented endoprosthesis, collagenous gel, tripeptide (gly-his-lys).

[The role of collagen implants containing the tripeptide gly-his-lys in bone healing process.]

The authors prepared 12,5% collagen gel, that they supplemented by tripeptide gly-his-lys. peflacin and hypersulfated glycosaminoglycan (HSGAG). By means of I125 marking they followed up its absorption from small polyurethan sponges placed under the skin of rats. They found out, that absorption of gel without HSGAG is faster. No collagen antibodies (type I., II., III.) against the gel were formed neither in the experiment with rabbits, nor later on with minipigs when gel was placed into bone defects. Further on presence of microorganisms in the gel was looked for with negative results on various bacteriological nutrient media. The gel was used in a model experiment for filling artifically created bone defects in femurs of minipigs. Healing was followed up both histologically and with help of RTG and NMR and compared with healing of defects either unfilled, or filled with gel containing peflacin and HSGAG, but not tripeptide. The authors found out that slowest healing was in case of unfilled defects, on the other hand defects filled with collagen gel and GHK were healing substantially faster than defects filled with gel without GHK, i.e. healing needs approximately half the time less. Key words: healing of bone defects, collagen, tripeptide GHK, peflacin.

Vaccination of pigs with replication-defective adenovirus vectored vaccines: the example of pseudorabies

The efficacy of a recombinant human adenovirus type 5 expressing gD, one of the immunogenic glycoprotein of pseudorabies virus, was tested in pigs. Due to the deletion of the E1a gene, the recombinant virus is unable to replicate in non transcomplementing cells but is capable of eliciting an immune response against gp50 after inoculation into animals. The virus was formulated in a water/oil/water emulsion, a strategy previously shown to enhance the immune response against the virus-induced gp50. Pigs of 18-25 kg were vaccinated twice and the recombinant virus was not isolated from nasal and rectal swabs taken after each injection of the vaccine. High levels of neutralizing antibodies were induced by the vaccination. Protection against a severe challenge was effective, as measured by growth performance (dG = 1.73), and reduction of the time of excretion of the challenge strain (mean time: 4.4 days for the vaccinated and 7.9 days for the control pigs). These results show that non replicating adenoviruses are able to induce a strong protective immune response against foreign genes in pigs, which may be of general interest for the design of pig vaccines.

Enhancement of the efficacy of a replication-defective adenovirus-vectored vaccine by the addition of oil adjuvants

We previously constructed a recombinant adenovirus with a defective E1A gene, which expresses high levels of the pseudorabies virus gp50 in non-transcomplementing cells. The virus is unable to replicate in mice. It elicited the production of anti-gp50 antibodies only when high concentrations (10(8) TCID50 per dose) of the virus were used and it gave mice little protection. The combination of the recombinant adenovirus at several concentrations (10(8), 10(7.4), 10(6.4) TCID50 per dose) with certain oil adjuvants in different galenic forms (water-in-oil, oil-in-water, water-in-oil-in-water) led to an increase in specific antibody responses and protection for the host when challenged with a virulent pseudorabies virus under very severe conditions, i.e. where 100% of unvaccinated mice died. A water-in-oil-in-water formulation induced a very high level of anti-gp50 antibodies even with a low concentration of adenovirus. These results could be correlated to the induction of cytokines, such as IL6, which is observed with this galenic form. The oil-adjuvanted emulsions induced IL2, suggesting that they were able to activate T-helper cells. Different oil formulations elicited the different IgG subclasses (IgG1, IgG2a, IgG2b, IgG3). These results can be extended to other live replication-defective vaccines expressing different proteins.

[The effect of aluminum on the structure and metabolism of collagen]

BACKGROUND

Aluminium is considered to be the etiopathogenetic factor in various pathological conditions. It was demonstrated already previously that metals even under conditions in vivo link with collagen structures and influence the protein metabolism. Therefore the authors investigated the effect of aluminium (Al) on collagen and its metabolism.

METHODS AND RESULTS

In the described trial aluminium was used as potassium alum, oxalate alum or aluminium chloride. The effect of aluminium was investigated in rats, chick embryos or fibroblast cultures. Using electron microscopy of collagen from the tail tendons, the development of transverse striation following 15 weeks of i.m. Al administration was revealed. At the same time also an increase of temperature of contraction of this collagen by 1.5 to 3.7 degrees C occurred, depending on the Al compound used. On fibroblast cultures an inhibitory effect of Al on their proliferation was found. In chick embryos Al caused a decline of the radioactive hydroxyproline concentration and thus also a reduced collagen synthesis practically in all investigated tissues. Similarly the negative effect of Al was manifested in the incorporation of radioactive glucosamine into proteoglycans of granulation tissue of rats. In cartilaginous collagen enhanced proline hydroxylation caused by Al was observed.

CONCLUSIONS

Although it is not possible, with regard to Al chemistry, to make an unequivocal statement on the nature of the compound which causes a particular reaction in biological systems, it may be said, based on the achieved results, that Al has an effect on biological systems due to its bond with collagen structures and by influencing their metabolism.

Design and validation of a new immunoassay for soluble forms of thrombomodulin and studies on plasma

Thrombomodulin (TM), purified from human placental homogeneate by affinity chromatography on DIP-Thrombin agarose, was used to develop monoclonal antibodies (MAbs). Two of them, 3E2 and 24FM (both IgG1, K), which were not calcium-dependent, were found convenient for developing a two-site enzyme immunoassay. Testing of recombinant and truncated forms of TM26 demonstrated that the species containing the amino terminus including the lectin-like domain and the epidermal growth factor (EGF)-like domains 1-4 were fully measured. The working range was from 2 to 100 ng/ml with a detection threshold of 2 ng/ml. Intraassay and interassay reproducibilities were, respectively, below 7.4% and 8.6%, whereas recovery of purified TM was between 88 and 114% in plasma. Mean plasma concentration was 42.1 (+/- 11.3) ng/ml (males 51.8 +/- 7.9 ng/ml, females 34.8 +/- 7.8 ng/ml) and it was established on 62 normal individuals between the ages of 21 and 55 (28 males and 34 females). This new assay is a convenient tool for measuring plasma TM and establishing its diagnostic and predictive value in diseases associated to endothelial damage.

Anaplastic Wilms' tumour, a subtype displaying poor prognosis, harbours p53 gene mutations

The genetics of Wilms' tumour (WT), a paediatric malignancy of the kidney, is complex. Inactivation of the tumour suppressor gene, WT1, is associated with tumour aetiology in approximately 10-15% of WTs. Chromosome 17p changes have been noted in cytogenetic studies of WTs, prompting us to screen 140 WTs for p53 mutations. When histopathology reports were available, p53 mutations were present in eight of eleven anaplastic WTs, a tumour subtype associated with poor prognosis. Amplification of MDM2, a gene whose product binds and sequesters p53, was excluded. Our results indicate that p53 alterations provide a molecular marker for anaplastic WTs.

Standardization of immunoassays for antiphospholipid antibodies with beta 2GPI and role of other phospholipid cofactors

Presence of beta 2 Glycoprotein I (beta 2GPI), in addition to phospholipids, is an absolute requirement for binding APA. This binding is frequently observed with beta 2GPI coated alone, however many APA react only with beta 2GPI complexed to phospholipids, but not with phospholipids alone. We demonstrate that a subgroup of rabbit polyclonal antibodies to human beta 2GPI binds to this protein only when it is coated on a solid surface, but not if it is in solution. In addition, beta 2GPI present in goat serum is strongly fixed by the coated phospholipids and the complexes formed bind as well APA as the rabbit antibodies to beta 2GPI. The diluent used for testing APA, has a strong incidence on APA's reactivity as it can be a source of beta 2GPI. Antibody binding to beta 2GPI, Prothrombin, Protein S, and Annexin V, coated in the presence or in the absence of phospholipids, was tested in 55 patients with the antiphospholipid syndrome. The strongest binding of antibodies was observed in 39 plasma to a mixture of phospholipids and purified human beta 2GPI, however 17 samples also presented a significant reactivity to beta 2GPI alone. Nine plasmas contained antibodies to Prothrombin, 4 to Protein S, 3 to Annexin V, and 1 to Protein C. We conclude that most of the APA are directed to a complex of beta 2GPI and phospholipids although in some patients antibodies to beta 2GPI alone or to other phospholipid binding proteins are present.

Cloning, functional expression, and characterization of the human prostaglandin E2 receptor EP2 subtype

A cDNA clone encoding the human prostaglandin (PG) E2 receptor EP2 subtype has been isolated from a human lung cDNA library. The 1.9-kilobase pair cDNA, hEP2, encodes for a 488-amino acid protein with a predicted molecular mass of 53,115 and has the seven putative transmembrane domains characteristic of G protein-coupled receptors. The specific binding of [3H]PGE2 to COS cell membranes transfected with the hEP2 cDNA was of high affinity with an equilibrium dissociation constant (Kd) of 1 nM and the rank order of potency for prostaglandins in competition for [3H]PGE2 specific binding was PGE1 = PGE2 >> iloprost > PGF2 alpha > PGD2. In competition studies using more selective prostanoid-receptor agonist and antagonists, the [3H]PGE2 specific binding was competed by MB28767, an EP3 agonist, but not by the EP1-preferring antagonists AH6809 and SC19220, or by the EP2 agonist butaprost. Electrophysiological studies of Xenopus oocytes co-injected with hEP2 and cystic fibrosis transmembrane conductance regulator (cAMP-activated Cl- channel) cDNAs detected PGE2-specific inward Cl- currents, demonstrating that the hEP2 cDNA encoded a functional receptor which produced an increase in cAMP levels. Thus, we have cloned the human EP2 receptor subtype which is functionally coupled to increase in cAMP. Northern blot analysis showed that hEP2 is expressed as a 3.8-kilobase mRNA in a number of human tissues with the highest expression levels present in the small intestine.

[Intracavernous auto-injection of prostaglandin E1 for diagnosis and treatment of erectile dysfunction]

34 impotent patients were offered auto-injection therapy and all except 2 began treatment. Prostaglandin E1 (PGE) was used regularly for a mean of 8.6 months (range 1-17). The onset of erection was 5-30 min (mean 11.4) after injection and it lasted at least 30 min (mean 106.2 min). An erection of more than 6 hrs was observed in only 2 patients. There have been no instances of cavernous fibrosis, chemical priapism or systemic reactions. The most common adverse effect was penile pain after injection. It was mild to moderate in 4 patients (11.7%), and in only 1 was it severe enough to require stopping treatment. Overall, intracavernous injection of PGE appears to be safe, effective treatment for impotence without side-effects other than pain after injection in a few.

Characterization of protein tyrosine phosphatase SH-PTP2. Study of phosphopeptide substrates and possible regulatory role of SH2 domains

The src homology 2 (SH2) domain containing protein-tyrosine-phosphatase SH-PTP2, was over-expressed in Escherichia coli for a kinetic study employing a set of synthetic 13- to 14-mer phosphopeptide substrates. The full-length SH-PTP2 protein, as well as a truncated form, lacking the two amino terminus SH2 domains (SH-PTP2(delta SH2)), exhibited Michaelis-Menten kinetics, and demonstrated striking substrate preferences on phosphopeptides having sequences based on sites of intracellular protein tyrosine phosphorylation. For example, while a KM of 59 microM and kcat/KM of 1.1 x 10(5) were obtained using SH-PTP2(delta SH2) and PDGFRY1021, a phosphorylation site within the platelet-derived growth factor receptor, other peptides revealed no detectable phosphate release. PDGFRY1009, modeled after a sequence identified as an in vivo binding site for SH-PTP2, was also a good substrate for this enzyme. The truncated form, lacking the SH2 domains demonstrated higher catalytic efficiency than the full-length enzyme. Interestingly, soluble SH2 domains were found to inhibit the catalytic activity of SH-PTP2 in a concentration-dependent manner. There was also evidence of a non-phosphotyrosine-mediated association between the two domains. These observations suggested that the SH2 domains have a direct role in regulating the catalytic activity of SH-PTP2.

Engineering and overexpression of periplasmic forms of the penicillin-binding protein 3 of Escherichia coli

Replacement of the 36 and 56 N-terminal amino acid residues of the 588-amino-acid-residue membrane-bound penicillin-binding protein 3 (PBP3) of Escherichia coli by the OmpA signal peptide allows export of F37-V577 PBP3 and G57-V577 PBP3 respectively into the periplasm. The modified ftsI genes were placed under the control of the fused lpp promoter and lac promoter/operator; expression of the truncated PBP3s was optimized by varying the copy number of the recombinant plasmids and the amount of LacI repressor, and export was facilitated by increasing the SecB content of the producing strain. The periplasmic PBP3s (yield 8 mg/l of culture) were purified to 70% protein homogeneity. They require the presence of 0.25 M NaCl to remain soluble. Like the membrane-bound PBP3, they undergo processing by elimination of the C-terminal decapeptide I578-S588, they bind penicillin in a 1:1 molar ratio and they catalyse hydrolysis and aminolysis of acyclic thioesters that are analogues of penicillin. The membrane-anchor-free PBP3s have ragged N-termini. The G57-V577 PBP3, however, is less prone to proteolytic degradation than the F37-V577 PBP3.

Cloning and expression of three isoforms of the human EP3 prostanoid receptor

Functional cDNA clones coding for three isoforms of the human prostaglandin E receptor EP3 subtype have been isolated from kidney and uterus cDNA libraries. The three isoforms, designated hEP3-I, hEP3-II and hEP3-III, have open reading frames corresponding to 390, 388 and 365 amino acids, respectively. They differ only in the length and amino acid composition of their carboxy-terminal regions, beginning at position 360. The human EP3 receptor has seven predicted transmembrane spanning domains and therefore belongs to the G-protein-coupled receptor family. The rank order of potency for prostaglandins and related analogs in competition for [3H]PGE2 specific binding to membranes prepared from transfected COS cells was comparable for all three isoforms, and as predicted for the EP3 receptor, with PGE2 = PGE1 >> PGF2 alpha = iloprost > PGD2 >> U46619. In addition, the EP3-selective agonist MB28767 was a potent competing ligand with an IC50 value of 0.3 nM, whereas the EP1-selective antagonist AH6909 gave IC50 values of 2-7 microM and the EP2-selective agonist butaprost was inactive. In summary, we have cloned three isoforms of the human EP3 receptor having comparable ligand binding properties.

The effect of different collagens and of proteoglycan on the retraction of collagen lattice

The effect of various collagens and proteoglycan on the formation and retraction of collagen lattices was tested. The most rapid aggregation of collagen molecules was observed by the use of the least cross-linked collagen fractions (ie pepsin-digested calf skin collagen type I). Lattices formed with more cross-linked collagens (acid soluble collagen-ASC, type III) contracted slowly and less intensively. Unpurified pepsinized cartilage extract containing collagen types II, IX and XI, some glycoproteins and proteoglycans formed lattices rather well. On the contrary, purified collagen type II as well as polymeric collagen (solubilized by denaturing conditions) did not form lattices at all. The lattice formation and retraction was intensified by addition of proteoglycan into the culture medium. The authors suggest that the kinetics of the lattice formation and retraction depends on the amount of collagen cross-links and the concentration of proteoglycan in the culture medium.

Cloning and expression of a cDNA for the human prostaglandin E receptor EP1 subtype

A functional cDNA clone coding for the human prostaglandin E receptor EP1 subtype has been isolated from a human erythroleukemia cell cDNA library probed by low-stringency hybridization using a polymerase chain reaction fragment of the human thromboxane receptor. The human EP1 receptor is comprised of 402 amino acids with a predicted molecular mass of 41,858 and has the topography common to all G-protein-coupled receptors with seven predicted transmembrane spanning domains. Prostaglandin (PG) E2 challenge of Xenopus oocytes injected with EP1 cDNA resulted in an increase in intracellular Ca2+. In addition, the rank order of potency for prostaglandins in competition for [3H]PGE2 specific binding to membranes prepared from EP1 cDNA transfected COS cells was PGE2 > PGE1 > PGF2 alpha > PGD2. Furthermore, the EP1 receptor-selective antagonists AH 6809 and SC19220 were more potent than the EP2 receptor-selective agonist butaprost in these competition binding assays. In summary, therefore, we have cloned the human EP1 receptor subtype which is functionally coupled to an increase in intracellular Ca2+.

[Morphological studies of Babesia divergens during continuous transfer in Meriones unguiculatus]

A strain of Babesia divergens was propagated by inoculation of 1.5 x 10(7) parasitized erythrocytes in 30 passages under same conditions on altogether 150 jirds. The developmental stages of Babesia divergens revealed pleomorphism in the erythrocytes of the jird. Single parasites were observed as being pyriform, globular, budding, ring-like or amoebid. The shape of dividing parasites varied between the spherical and the pyriform. The stages in the erythrocytes were localized predominantly intermedia. The reduction of the number of dividing forms and the increase of single forms occurred with increasing numbers of passages. Length and breadth of double pyriforms increased by approximately 20%.

Cloning, expression and mutational analysis of SH-PTP2, human protein-tyrosine phosphatase

A human cDNA clone encoding a nonreceptor protein-tyrosine-phosphatase (PTP) has been isolated and sequenced. The 2.1 kilobase pair cDNA encodes for a 593 amino acid protein that contains a single tyrosine phosphatase catalytic domain at the C-terminus. At the N-terminus the protein has two adjacent copies of Src homology region (SH2 domain) which show 61% and 73% identity at the amino acid level to the SH2 domains of the human PTP1C and Drosophila corkscrew protein, respectively. The overall homology between SH-PTP2 and PTP1C or to corkscrew protein is 58%. When this protein (or its catalytic domain) was expressed in E. coli as a glutathione-S-transferase fusion protein tyrosine-phosphatase activity was detected in bacterial cell extracts. Site-directed mutation made at the conserved cysteine (459) residue to serine within the highly conserved VHCXAGXXR sequence in the PTP catalytic domain resulted in complete loss of enzymatic activity demonstrating the importance of this cysteine residue in catalysis. Northern blot analysis showed that SH-PTP2 is expressed as a 6.5 kilobase mRNA in a number of fetal and adult human tissues and cell lines. The highest levels of its mRNA were detected in fetal brain and in adult heart tissue. The identification of SH-PTP2 along with PTP1C and corkscrew protein suggest that there exist a family of nonreceptor PTP containing SH2-domain which will participate in specific signal transduction pathways involving tyrosine phosphorylation-dephosphorylation.

A novel genetic thrombocytopenia (Paris-Trousseau) associated with platelet inclusions, dysmegakaryopoiesis and chromosome deletion AT 11q23

We report a novel case of hereditary thrombocytopenia. A chronic thrombocytopenia was noted in a woman with mild hemorrhagic complications as well as in her very young son. A platelet fraction contained giant granules stained in red on blood smears. The number of bone marrow megakaryocytes was increased with many micromegakaryocytes. Since the platelet life span was normal, these results indicated an ineffective platelet production. A constitutional cytogenetic abnormality was detected in the two patients: a deletion of the long arm of chromosome 11. The association of these abnormalities constitute a new disorder: this never described cytological entity is a valuable model for exploring the role of some genes involved in the regulation of thrombopoiesis.

Enantioselective activation of the peroxisome proliferator-activated receptor

A cell-based transactivation assay was established using the mouse full-length peroxisome proliferator-activated receptor (PPAR) cDNA sequence and the positive peroxisome proliferator-responsive regulatory element (-578 to -553) of the rat acyl-CoA oxidase gene promoter. Activation of the reporter plasmid was dependent on co-transfection of the full-length PPAR cDNA, and the response was greatly stimulated, up to 100-fold, by peroxisome proliferators such as Wy-14,643 ([4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio] acetic acid), nafenopin (2-methyl-2[p-(1,2,3,4-tetrahydro-1-naphthyl)phenoxy]-propionic acid), and clofibric acid (2-([p]-chlorophenoxy)-2-methylpropionic acid). Activation of the reporter plasmid promoter by the full-length PPAR cDNA also occurred at peroxisomal proliferator concentrations 40 times lower than that required for similar stimulation by a glucocorticoid-PPAR chimeric receptor. By using the stereoisomers of MK-571 ((+-)-3-(((3-(2-(7-chloro-2-quinolinyl)ethenyl)-phenyl)((3- (dimethylamino)-3-oxopropyl)-thio)methyl)-thio)propanoic acid), a potent leukotriene D4 receptor antagonist, we could show enantioselective activation of PPAR. The use of this compound in mice results in peroxisome proliferation; however, nearly all of the peroxisome proliferating activity can be attributed to the S enantiomer. Our results show a similar enantiomeric discrimination in PPAR activation of the reporter plasmid promoter, where again most of the activity can be attributed to the S enantiomer. The equivalent activities of these stereoisomers both in vivo and in the PPAR transactivation assay strongly implicate PPAR as a major component of the peroxisome proliferating mechanism in rodents.