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W Fiers

Publications and source records attributed to W Fiers.

At least 73 records · Page 4Linked to original sources
PubMed1997

Resistance to tumor necrosis factor (TNF) cytotoxicity by autocrine TNF production is independent of intracellular signaling pathways.

We previously showed that autocrine tumor necrosis factor (TNF) production in the TNF-sensitive L929sA fibrosarcoma cell line induced TNF resistance, which is correlated with downmodulation of both TNF receptors on the cell surface. We now analyzed whether autocrine TNF production also interfered with intracellular TNF signaling pathways. The L929sA-CAT-R55i cell line, in which cell death can be induced by controlled cytoplasmic expression of a trimeric fusion protein between chloramphenicol acetyltransferase and the intracellular domain of TNF-R55 (CAT-R55i), was supertransfected with the murine TNF gene. Expression of the latter conferred resistance to cell death induced by exogenous TNF, while cytotoxicity induced by CAT-R55i was not impaired. This demonstrates that autocrine TNF did not induce intracellular mechanisms that block TNF signaling leading to cell death. Thus the induction of TNF resistance via autocrine TNF production in L929sA cells is solely due to downmodulation of TNF receptors on the cell surface.

Animals↗
PubMed1997

Alpha 1-acid glycoprotein and alpha 1-antitrypsin inhibit TNF-induced but not anti-Fas-induced apoptosis of hepatocytes in mice.

The acute phase proteins alpha 1-acid glycoprotein (alpha 1-AGP) and alpha 1-antitrypsin (alpha 1-AT) were shown to inhibit, by a mechanism unidentified to date, the lethality induced by TNF both in normal mice and in mice sensitized with galactosamine. We found that both bovine alpha 1-AGP and human alpha 1-AT also inhibited specifically the induction of apoptosis of hepatocytes by TNF/ galactosamine in vivo. This inhibition is specific for TNF, since apoptosis induced by TNF and actinomycin D was also inhibited, while similar apoptosis of hepatocytes induced by anti-Fas remained unaffected. The observation that these acute phase proteins did not affect the induction by TNF of IL-6, nitric oxide, or serum amyloid P excludes a nonselective inhibition of the TNF-activated pathways. The protection conferred by alpha 1-AGP and alpha 1-AT is presumably indirect, since these proteins did not inhibit TNF/actinomycin D-induced apoptosis in the hepatoma cell lines HepG2 and BWTG3.

Animals↗
PubMed1997

A20 inhibits NF-kappaB activation independently of binding to 14-3-3 proteins.

The A20 protein, which belongs to a class of Cys2/Cys2 zinc finger proteins, has been characterized as an inhibitor of NF-kappaB activation. In order to clarify its molecular mechanism of action, the yeast two-hybrid system was used to screen for interacting proteins. We report that different isoforms of 14-3-3 proteins, viz. eta and zeta, are able to bind A20, involving the 14-3-3-binding motif RSKSDP located between zinc fingers 3 and 4. However, A20 mutants that no longer associated with 14-3-3 proteins could still fully inhibit NF-kappaB activation induced by tumor necrosis factor, interleukin-1beta or phorbol 12-myristate 13-acetate, thus excluding a crucial role for 14-3-3 interaction in this A20 function.

14-3-3 Proteins↗
PubMed1997

Protection of mice against a lethal influenza challenge by immunization with yeast-derived recombinant influenza neuraminidase.

The head domain of recombinant neuraminidase of A/Victoria/3/75 influenza virus was produced in a secreted form in the methylotrophic yeast Pichia pastoris using the P. pastoris alcohol oxidase 1 promoter and the Saccharomyces cerevisiae alpha-mating-factor signal sequence. Cultures in shake flasks provided expression levels of approximately 2.5-3 mg/l. Recombinant neuraminidase was purified from the culture medium to over 99% homogeneity. Although P. pastoris-secreted products are believed to carry shorter N-linked carbohydrate side chains than glycoproteins of S. cerevisiae, secreted neuraminidase was hyperglycosylated, with N-glycans of the high-mannose type containing up to 30-40 mannose residues. N-glycans were phosphorylated and only partially sensitive to alpha-mannosidase treatment. Balb/c mice immunized three times with 2 microg purified recombinant neuraminidase were 50% protected against a lethal challenge of mouse-adapted homologous virus; removal of glycosylation at the top of neuraminidase resulted in improved protection. The results provide a system for the production of an effective recombinant influenza vaccine that can easily be scaled up.

Animals↗
PubMed1997

Induced expression of trimerized intracellular domains of the human tumor necrosis factor (TNF) p55 receptor elicits TNF effects.

The various biological activities of tumor necrosis factor (TNF) are mediated by two receptors, one of 55 kD (TNF-R55) and one of 75 kD (TNF-R75). Although the phenotypic and molecular responses elicited by TNF in different cell types are fairly well characterized, the signaling pathways leading to them are so far only partly understood. To further unravel these processes, we focused on TNF-R55, which is responsible for mediating most of the known TNF effects. Since several studies have demonstrated the importance of receptor clustering and consequently of close association of the intracellular domains for signaling, we addressed the question of whether clustering of the intracellular domains of TNF-R55 (TNF-R55i) needs to occur in structural association with the inner side of the cell membrane, where many signaling mediators are known to reside. Therefore, we investigated whether induced intracellular clustering of only TNF-R55i would be sufficient to initiate and generate a full TNF response, without the need for a full-length receptor molecule or a transmembrane region. Our results provide clear evidence that inducible forced trimerization of either TNF-R55i or only the death domain elicits an efficient TNF response, comprising activation of the nuclear factor kappaB, induction of interleukin-6, and cell killing.

Dimerization↗
PubMed1997

Differential involvement of caspases in apoptosis of myeloid leukemic cells induced by chemotherapy versus growth factor withdrawal.

To assess the potential involvement of the caspase family in the IL-3-dependent murine myeloid leukemic cell line 32D, we studied the effect of bcl-2, crmA and three synthetic caspase inhibitors on apoptosis induced by chemotherapy or IL-3 withdrawal. Apoptosis induced by IL-3 deprivation or by ActD appears to be mediated by a crmA-insensitive pathway. Cell death by IL-3 withdrawal is inhibited by the caspase-inhibitor ZVAD-fmk, but not DEVD-fmk or YVAD-cmk. In contrast, DEVD-fmk as well as ZVAD-fmk protect 32D cells from ActD-induced apoptosis. These results indicate that different caspases are involved in apoptosis induced by growth factor withdrawal and by chemotherapy.

Animals↗
PubMed1997

Cleavage of PITSLRE kinases by ICE/CASP-1 and CPP32/CASP-3 during apoptosis induced by tumor necrosis factor.

Emerging evidence suggests that multiple aspartate-specific cysteine proteases (caspases (CASPs)) play a crucial role in programmed cell death. Many cellular proteins have been identified as their substrates and serve as markers to assay the activation of CASPs during the death process. However, no substrate has yet been unambiguously identified as an effector molecule in apoptosis. PITSLRE kinases are a superfamily of Cdc2-like kinases that have been implicated in apoptotic signaling and tumorigenesis. In this paper we report that tumor necrosis factor (TNF)-mediated apoptosis is associated with a CrmA- and Bcl-2-inhibitable cleavage of PITSLRE kinases, indicating a role for CASPs. Testing of seven murine CASPs for their ability to cleave p110 PITSLRE kinase alpha2-1 in vitro revealed that only CASP-1 (ICE (interleukin-1beta-converting enzyme)) and CASP-3 (CPP32) were able to produce the same 43-kDa cleavage product as observed in cells undergoing TNF-induced apoptosis. Mutational analysis revealed that cleavage of p110 PITSLRE kinase alpha2-1 occurred at Asp393 within the sequence YVPDS, which is similar to that involved in the CASP-1-mediated cleavage of prointerleukin-1beta. TNF-induced proteolysis of PITSLRE kinases was still observed in fibroblasts from CASP-1(0/0) mice. These data implicate CASP-3 as a potentially important CASP family protease responsible for the cleavage of PITSLRE kinases during TNF-induced apoptosis.

Animals↗
PubMed1997

Crystallization and preliminary X-ray studies of mouse tumor necrosis factor.

Well diffracting crystals of recombinant mouse tumor necrosis factor (mTNF) have been obtained. The sitting-drop vapor-diffusion method was used to grow crystals suitable for X-ray studies from solutions containing methoxypolyethylene glycol 2000 and isopropanol as precipitants. The crystals belong to the space group P1 with unit-cell dimensions a = 49.40, b = 48.24, c = 51.13 A, alpha = 115.06, beta = 103.32, gamma = 91.27 degrees and one trimer in the asymmetric unit. Crystals are stable to X-rays and diffract beyond 2.0 A. Cooling the crystal during data collection is necessary since crystals dissolve at room temperature.

Journal Article↗
PubMed1997

Structural characterization of N-linked oligosaccharides from cellobiohydrolase I secreted by the filamentous fungus Trichoderma reesei RUTC 30.

We have characterized the primary structures of the predominant N-linked oligosaccharides on cellobiohydrolase I from the filamentous fungus Trichoderma reesei RUTC30. Different enzymatic and chromatographic techniques were used to analyze six oligosaccharides. The combined data showed that the fungal carbohydrates have a core structure that is identical to the mammalian N-linked core. In the bulk of the N-glycans, the alpha-1,3 arm is extended with two mannoses and a glucose, suggesting incomplete processing of the oligosaccharides in the endoplasmic reticulum. The alpha-1,6 arm shows a remarkable heterogeneity: in addition to alpha-1,2-Man and alpha-1,6-Man, the presence of a terminal mannose alpha-1,6-phosphodiester was observed. This latter substituent has not been characterized before on mannosidase-processed N-glycan and its function and synthesis pathway are entirely unknown. The predominant N-glycans on cellobiohydrolase I can be represented as follows: GlcMan8GlcNAc2, GlcMan7GlcNAc2, Man7GlcNAc2, ManPGlcMan7GlcNAc2, GlcMan5GlcNAc2 and Man5GlcNAc2.

Carbohydrate Sequence↗
PubMed1997

Characterization of seven murine caspase family members.

Seven members of the murine caspase (mCASP) family were cloned and functionally characterized by transient overexpression: mCASP-1 (mICE), mCASP-2 (Ich1), mCASP-3 (CPP32), mCASP-6 (Mch2), mCASP-7 (Mch3), mCASP-11 (TX) and mCASP-12. mCASP-11 is presumably the murine homolog of human CASP-4. Although mCASP-12 is related to human CASP-5 (ICErel-III), it is most probably a new CASP-1 family member. On the basis of sequence homology, the caspases can be divided into three subfamilies: first, mCASP-1, mCASP-11 and mCASP-12; second, mCASP-2; third, mCASP-3, mCASP-6 and mCASP-7. The tissue distribution of the CASP-1 subfamily transcripts is more restricted than that of the CASP-3 subfamily transcripts, suggesting that the transcriptional regulation of the CASP members within one subfamily is related, but is quite different between the CASP-1 and the CASP-3 subfamilies. Transient overexpression of each of the seven CASPs induced apoptosis in mammalian cells. Only two, mCASP-1 as well as mCASP-3, were able to process precursor interleukin (IL)-1beta to biologically active IL-1beta. In addition, mCASP-3 is the predominant PARP-cleaving enzyme in vivo.

Amino Acid Sequence↗
PubMed1997

Cleavage of caspase family members by granzyme B: a comparative study in vitro.

The aspartase granzyme B is one of the major components of the granules involved in cell killing by cytotoxic T lymphocytes. Granzyme B has been shown to activate the apoptotic death pathway in the target cell, and this involves activation of members of the caspase (CASP) protein family. Therefore, activational cleavage of mouse (m) CASP proforms by granzyme B was examined in vitro. CASP can be subdivided in the CASP-1 (interleukin-1 beta-converting enzyme; ICE) subfamily, the CASP-2 (Ich1) subfamily, and the CASP-3 (CPP32) subfamily. Our results reveal that the proforms of the CASP-3 subfamily members mCASP-3 and mCASP-7 are hydrolyzed by granzyme B, while proforms of CASP-2 and CASP-1 subfamily members are not directly cleaved. Only one CASP-3 subfamily member, pro-mCASP-6, was not proteolytically cleaved by granzyme B. These results indicate that two members of the CASP-3 subfamily, but no others, become activated by granzyme B.

Animals↗
PubMed1997

Crucial role of tumor necrosis factor (TNF) receptor 2 and membrane-bound TNF in experimental cerebral malaria.

Tumor necrosis factor (TNF) has been implicated in the pathogenesis of experimental cerebral malaria (CM), but the respective role of its two types of receptors has not been established. A significant increase in the expression of TNF-receptor 2 (TNFR2, p75), but not of TNFR1 (p55), was found on brain microvessels at the time of CM in susceptible animals. Moreover, mice genetically deficient for TNFR2 (Tnfr2null) were significantly protected from experimental CM, in contrast to TNFR1-deficient (Tnfr1null) mice, which were as susceptible as wild-type mice. To identify the factors involved in the protection from CM conferred by the lack of TNFR2, we assessed in both knockout and control mice the serum concentrations of mediators that are critical for the development of CM, as well as the up-regulation of intercellular adhesion molecule-1 (ICAM-1) in the brain microvessels. No significant difference in serum levels of TNF and interferon-gamma was found between infected wild-type and Tnfr1null or Tnfr2null mice. Interestingly, the pronounced ICAM-1 up-regulation and leukocyte sequestration, typically occurring in brain microvessels of CM-susceptible animals, was detected in infected control and Tnfr1null mice-both of which developed CM-whereas no such ICAM-1 up-regulation or leukocyte sequestration was observed in Tnfr2null mice, which were protected from CM. Making use of microvascular endothelium cells (MVEC) isolated from wild-type, Tnfr1null or Tnfr2null mice, we show that soluble TNF requires the presence of both TNF receptors, whereas membrane-bound TNF only needs TNFR2 for TNF-mediated ICAM-1 up-regulation in brain MVEC. Thus, only in MVEC lacking TNFR2, neither membrane-bound nor soluble TNF cause the up-regulation of ICAM-1 in vitro. In conclusion, these results indicate that the interaction between membrane TNF and TNFR2 is crucial in the development of this neurological syndrome.

Animals↗
PubMed1997

Differential role of calcium in tumour necrosis factor-mediated apoptosis and secretion of granulocyte-macrophage colony-stimulating factor in a T cell hybridoma.

The authors investigated the dependence on extracellular and intracellular free Ca2+ in the induction of apoptosis and secretion of granulocyte-macrophage colony-stimulating factor (GM-CSF) by tumour necrosis factor (TNF) in a rat/mouse T cell hybridoma PC60 R55/R75, using the Ca2+ chelators EGTA and BAPTA/AM, respectively. TNF-induced apoptosis still occurred in the absence of free Ca2+, while GM-CSF production required the continuous presence of Ca2+. The latter was also true for GM-CSF production driven by interleukin 1 (IL-1). The dependence on Ca2+ in the induction of GM-CSF, but not of apoptosis, was further confirmed by the inhibition of TNF- or IL-1-induced cytokine production by cyclosporin A or FK506, drugs that block the Ca2+/calmodulin-dependent protein Ser/Thr phosphatase calcineurin. This differential requirement for Ca2+ illustrates the partial functional redundancy between TNF and IL-1, showing the activation of cytokine gene expression through a Ca(2+)-dependent activation of calcineurin, and a Ca(2+)-independent activation of apoptosis, exerted solely by TNF.

Animals↗
PubMed1997

Tumour necrosis factor-induced necrosis versus anti-Fas-induced apoptosis in L929 cells.

Murine fibrosarcoma L929 cells were transfected with human Fas cDNA. The mode of cell death was analysed following treatment either with tumour necrosis factor (TNF) or with agonistic antibodies to Fas. While triggering of the TNF receptors led to necrosis, clustering of the Fas antigen resulted in apoptotic cell death. N-tosyl-l-phenylalanine chloromethyl ketone and Nalpha-p-tosyl-l-lysine chloromethyl ketone, two serine protease inhibitors, has a protective effect on TNF-induced killing, while Fas-mediated cell death was rather enhanced. Lithium chloride, which had a synergistic effect on TNF cytotoxicity, did not affect Fas-mediated death, whereas staurosporine had an enhancing effect on both types of cell death. Aphidicolin and hydroxyurea, inhibitors of DNA synthesis, were able to sensitize cells to Fas-induced killing, but had no effect on TNF cytotoxicity. Finally, we demonstrate that the effect of increasing concentrations of actinomycin D or cycloheximide is very different for the two types of cell killing. We conclude that either necrosis or apoptosis can occur in the same cell type, depending on the trigger, and that, although both pathways perhaps may share some cellular components, signal transduction is different for the two types of cell death.

Adjuvants, Immunologic↗
PubMed1997

Recombination signal sequence binding protein Jkappa is constitutively bound to the NF-kappaB site of the interleukin-6 promoter and acts as a negative regulatory factor.

Analysis by electrophoretic mobility shift assays (EMSA) of the different proteins associated with the kappaB sequence of the interleukin-6 (IL-6) promoter (IL6-kappaB) allowed us to detect a specific complex formed with the recombination signal sequence binding protein Jkappa (RBP-Jkappa). Single-base exchanges within the oligonucleotide sequence defined the critical base pairs involved in the interaction between RBP-Jkappa and the IL6-kappaB motif. Binding analysis suggests that the amount of RBP-Jkappa protein present in the nucleus is severalfold higher than the total amount of inducible NF-kappaB complexes but that the latter bind DNA with a 10-fold-higher affinity. A reporter gene study was performed to determine the functional implication of this binding; we found that the constitutive occupancy of the IL6-kappaB site by the RBP-Jkappa protein was responsible for the low basal levels of IL-6 promoter activity in L929sA fibrosarcoma cells and that RBP-Jkappa partially blocked access of NF-kappaB complexes to the IL-6 promoter. We propose that such a mechanism could be involved in the constitutive repression of the IL-6 gene under normal physiological conditions.

Animals↗
PubMed1996

TNF receptor p55 plays a major role in centrally mediated increases of serum IL-6 and corticosterone after intracerebroventricular injection of TNF.

The aim of this work was to study the relative role of the two TNF receptors (p55 and p75) in the central actions of TNF, studying the elevation of serum corticosterone (CS) and IL-6 levels after injection of recombinant murine (rm)TNF (intracerebroventricularly (i.c.v.)) in normal or p55-deficient (p55 -/-) mice. rmTNF induced high serum IL-6 levels and doubled serum CS in normal mice, whereas no elevation of serum IL-6 or CS was induced in p55 -/- mice. However, a normal CS response was observed in p55 -/- mice after LPS (2.5 microg, i.c.v.). p55 -/- mice also responded, although to a lesser extent than p55 +/+, in terms of LPS-induced IL-6 production. We also injected two agonist Abs specific for the two receptors, alpha p55 and alpha p75. While alpha p55 injected i.c.v. induced a marked elevation in CS and IL-6, alpha p75 induced CS (although less than alpha p55) but no IL-6. rmTNF, which binds both receptors, was more potent in inducing IL-6 and CS than injection of rhTNF, which in mice binds only p55. Finally, we investigated the role of p55 and p75 in IL-6 induction by TNF in a murine brain endothelioma. The results resembled closely those obtained in vivo: rmTNF was more potent than rhTNF and only alpha p55, and not alpha p75, induced IL-6 production. These data indicate that p55 plays a major role in TNF activation of the hypothalamus-pituitary-adrenal axis and in the centrally mediated induction of peripheral IL-6 by TNF, but p75, despite having little IL-6 inductive properties by itself, seems to potentiate p55 induction of IL-6.

Animals↗