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T Decker

Publications and source records attributed to T Decker.

At least 37 records · Page 2Linked to original sources
PubMed1999

Stress-induced phosphorylation of STAT1 at Ser727 requires p38 mitogen-activated protein kinase whereas IFN-gamma uses a different signaling pathway.

STAT1 is an essential transcription factor for macrophage activation by IFN-gamma and requires phosphorylation of the C-terminal Ser727 for transcriptional activity. In macrophages, Ser727 phosphorylation in response to bacterial lipopolysaccharide (LPS), UV irradiation, or TNF-alpha occurred through a signaling path sensitive to the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580 whereas IFN-gamma-mediated Ser727 phosphorylation was not inhibited by the drug. Consistently, SB203580 did not affect IFN-gamma-mediated, Stat1-dependent transcription but inhibited its enhancement by LPS. Furthermore, LPS, UV irradiation, and TNF-alpha caused activation of p38 MAPK whereas IFN-gamma did not. An essential role for p38 MAPK activity in STAT1 Ser727 phosphorylation was confirmed by using cells expressing an SB203580-resistant p38 MAPK. In such cells, STAT1 Ser727 phosphorylation in response to UV irradiation was found to be SB203580 insensitive. Targeted disruption of the mapkap-k2 gene, encoding a kinase downstream of p38 MAPK with a key role in LPS-stimulated TNF-alpha production and stress-induced heat shock protein 25 phosphorylation, was without a significant effect on UV-mediated Ser727 phosphorylation. The recombinant Stat1 C terminus was phosphorylated in vitro by p38MAPKalpha and beta but not by MAPK-activated protein kinase 2. Janus kinase 2 activity, previously reported to be required for IFN-gamma-mediated Ser727 phosphorylation, was not needed for LPS-mediated Ser727 phosphorylation, and activation of Janus kinase 2 did not cause the appearance of STAT1 Ser727 kinase activity. Our data suggest that STAT1 is phosphorylated at Ser727 by a stress-activated signaling pathway either through p38 MAPK directly or through an unidentified kinase downstream of p38MAPK.

Animals↗
PubMed1999

Lipopolysaccharide induces in macrophages the synthesis of the suppressor of cytokine signaling 3 and suppresses signal transduction in response to the activating factor IFN-gamma.

The goal of this study was to investigate how bacterial LPS affects macrophage responsiveness to the activating factor IFN-gamma. Pretreatment of macrophages with LPS for <2 h increased the transcriptional response to IFN-gamma. In contrast, simultaneous stimulation with IFN-gamma and LPS, or pretreatment with LPS for >4 h, suppressed Stat1 tyrosine 701 phosphorylation, dimerization, and transcriptional activity in response to IFN-gamma. Consistently, the induction of MHCII protein by IFN-gamma was antagonized by LPS pretreatment. Neutralizing Abs to IL-10 were without effect on LPS-mediated suppression of Stat1 activation. Decreased IFN-gamma signal transduction after LPS treatment corresponded to a direct induction of suppressor of cytokine signaling3 (SOCS3) mRNA and protein. Under the same conditions socs1, socs2, and cis genes were not transcribed. In transfection assays, SOCS3 was found to suppress the transcriptional response of macrophages to IFN-gamma. A causal link of decreased IFN-gamma signaling to SOCS3 induction was also suggested by the LPS-dependent reduction of IFN-gamma-mediated Janus kinase 1 (JAK1) activation. Further consistent with inhibitory activity of SOCS3, LPS also inhibited the JAK2-dependent activation of Stat5 by GM-CSF. Our results thus link the deactivating effect of chronic LPS exposure on macrophages with its ability to induce SOCS3.

Animals↗
PubMed1999

Protein tyrosine kinase Pyk2 mediates the Jak-dependent activation of MAPK and Stat1 in IFN-gamma, but not IFN-alpha, signaling.

Two distinct types of interferon, IFN-alpha/beta and IFN-gamma, commonly exhibit antiviral activities by transmitting signals to the interior of the cell via their homologous receptors. Receptor stimulation results in the activation of distinct combinations of Janus family protein tyrosine kinases (Jak PTKs); Jak1/Tyk2 and Jak1/Jak2 for IFN-alpha/beta and IFN-gamma, respectively. Jak PTK activation by these IFNs is commonly followed by tyrosine phosphorylation of the transcription factor Stat1 at Y701, which is essential for dimerization, translocation to the nucleus and DNA-binding activity. To gain full transcriptional activity, Stat1 also requires serine phosphorylation at S727. In this paper we demonstrate that Pyk2, which belongs to another PTK family, is critical for the Jak-mediated MAPK and Stat1 activation by IFN-gamma, but not IFN-alpha. Pyk2 is selectively associated with Jak2 and activated by IFN-gamma. Overexpression of PKM, a dominant interfering form of Pyk2, in NIH 3T3 cells results in a strong inhibition of the IFN-gamma-induced activation of Erk2, serine phosphorylation of Stat1 and Stat1-dependent gene transcription. Finally, the antiviral action of IFN-gamma, but not IFN-alpha, is severely impaired by PKM overexpression. Thus, the two types of IFN may utilize distinct Jak-mediated Erk2, and possibly other MAPK activation pathways for their antiviral action.

3T3 Cells↗
PubMed1999

Comparative genomic hybridization of ductal carcinoma in situ of the breast-evidence of multiple genetic pathways.

There is strong evidence that ductal carcinoma in situ (DCIS) represents a precursor lesion of invasive breast cancer. In order to analyse specific chromosomal alterations of DCIS, 38 paraffin-embedded specimens of DCIS and six associated invasive carcinomas were examined by means of comparative genomic hybridization (CGH). Losses of 16q material were seen almost exclusively in well- and intermediately-differentiated DCIS. These two subgroups differed in the average number of genetic imbalances, 2.5 and 5.5 respectively. Additionally, a higher frequency of gains of 1q and losses of 11q material was seen in intermediately-differentiated in contrast to well-differentiated DCIS. Poorly-differentiated DCIS displayed a higher frequency of amplifications (17q12, 11q13) and a higher average rate of genetic imbalances (7.1). Analysis of adjacent invasive breast carcinoma revealed a genetic pattern almost identical to the one seen in the DCIS counterpart. These data characterize DCIS as a genetically far-advanced, heterogeneous lesion and as a direct precursor of invasive breast cancer.

Breast Neoplasms↗
PubMed1999

Transcription factor activity of STAT proteins: structural requirements and regulation by phosphorylation and interacting proteins.

The seven mammalian members of the signal transducer and activator of transcription (STAT) family share a common core structure which reflects their shared mechanism of activation, dimerization, and DNA binding. By contrast, the STAT C termini containing the sequences required for transcriptional activation are much less homologous, suggesting different ways by which individual STATs activate their target genes. This paper describes several important discoveries linked to mechanistic aspects of STAT transcription factor function. These include regulated serine phosphorylation of the transactivating domain, promoter-dependent interactions of STATs with each other, or of STATs with other transcription factors, and with transcriptional co-activators. The basis, background, and implications of these molecular events will be summarized and discussed.

Amino Acid Sequence↗
PubMed1999

[Results of the Elmslie-Trillat procedure in cases of patella(sub)luxation related to chondral pathology].

Between May 1981 and December 1993, 120 patients (126 knee joints) were operated using the Elsmlie-Trillat procedure because of patella(sub)luxation. 79 patients were reviewed at an average follow up of 4.1 (1-13.6) years. 46 women and 33 men were operated with an average age at operation of 26.9 (14-59) years. The examination included Bentley's Score, radiological parameters (e. g. grading of patella dislocation), grading of chondromalacia and patient characteristics (e. g. age, pre-operative time). 64 knee joints (70. 3 %) were evaluated 'very good' and 'good', using the score of Bentley. There were significantly worse results in cases with higher grading of chondromalacia (p <0.0036), longer pre-operative time (p < 0.012) and older patients (p < 0.0023). The worst and most highly significant results were in these patients with prior knee surgery (p < 0.0001). A good patella relocation correlated with improved results (p < 0.001). There was no difference in cases with patella dislocation and/or patellasubluxation. In conclusion, the Elmslie-Trillat procedure should be carried out 'in the correct manner and at an early stage'. To optimise the therapy in cases of patella dislocation the high number of operation techniques should be analysed and used regarding risk groups.

Adolescent↗
PubMed1999

The Epstein-Barr virus nuclear antigen 2 (EBNA2), a protein required for B lymphocyte immortalization, induces the synthesis of type I interferon in Burkitt's lymphoma cell lines.

Epstein-Barr virus nuclear antigen 2 (EBNA2), a protein involved in cell transformation, interferes with the cellular response to type I interferons (IFN-alpha/beta). We investigated the function of conditionally expressed EBNA2 in the context of the IFN response in Burkitt's lymphoma cell lines. Expression of EBNA2 led to the transcriptional activation of both endogenous or transfected IFN-stimulated genes (ISGs), genes which contain within their promoters either the interferon-stimulated response element (ISRE) or the gamma interferon activation site (GAS). In search of a molecular mechanism for the transcriptional induction of ISGs, we observed an EBNA2-dependent synthesis of IFN-beta mRNA at low levels and the secretion of low amounts of IFN. A transfected IFN-beta promoter responded to EBNA2 activation, and a sequence closely resembling a RBP-Jkappa binding site was pinpointed as a potential target of EBNA2 activity. EBNA2-dependent transcriptional induction of the IFN-beta promoter occurred in EBV-negative Burkitt's lymphoma cells, indicating that other EBV genes were not required for the induction of IFN-beta synthesis.

B-Lymphocytes↗
PubMed1998

Stat1 combines signals derived from IFN-gamma and LPS receptors during macrophage activation.

Complete activation of macrophages during immune responses results from stimulation with the activating cytokine interferon-gamma (IFN-gamma) and a second stimulus, usually a microbial product. Bacterial infection of macrophages, or treatment with bacterial lipopolysaccharide (LPS), resulted in rapid Stat1 phosphorylation on Ser727 (S727) independently of concomitant tyrosine phosphorylation. IFN-gamma also caused rapid phosphorylation of S727. In both situations, S727 phosphorylation was reduced by pre-treatment of cells with the serine kinase inhibitor H7. When macrophages were treated sequentially or simultaneously with LPS and IFN-gamma, the pool of molecules phosphorylated on both Tyr701 (Y701) and S727 was strongly increased. Consistently, Stat1-dependent transcription in response to IFN-gamma was significantly enhanced if the cells were pre-treated with bacterial LPS. The relative amount of S727-phosphorylated Stat1 in the non-tyrosine phosphorylated fraction was considerably smaller than that in the tyrosine-phosphorylated fraction. No evidence was found for an effect of S727 phosphorylation on the phosphorylation of Y701 by IFN-gamma. Thus, serine and tyrosine phosphorylation of Stat1 are caused independently of each other, but the serine kinase may recognize tyrosine-phosphorylated Stat1 preferentially in the course of an IFN-gamma response. The data suggest Stat1 to be a convergence point for immunological stimuli in a macrophage proinflammatory response.

Animals↗
PubMed1998

Jak2-Stat5 interactions analyzed in yeast.

Many cytokine receptors employ Janus protein tyrosine kinases (Jaks) and signal transducers and activators of transcription (Stats) for nuclear signaling. Here, we have established yeast strains in which an autoactivated Jak2 kinase induces tyrosine phosphorylation, dimerization, nuclear translocation, and DNA binding of a concomitantly expressed Stat5 protein. Transcriptional activity of Stat5 on a stably integrated, Stat-dependent reporter gene required the C-terminal fusion of the VP16 transactivation domain. In such yeast strains, the interaction between Jak2 and Stat5 was analyzed without interference by other mammalian proteins involved in regulating Jak-Stat signaling, and mutant versions of both proteins were analyzed for their ability to productively interact. Complexes between Jak2 and Stat5 were found to be stable under stringent co-immunoprecipitation conditions. Deletion of the Jak homology regions 2-7 (JH2-JH7) of Jak2, leaving only the kinase domain (JH1) intact, reduced the ability of the kinase to phosphorylate Stat5, whereas deletion of the JH2 domain caused an increased enzymatic activity. A site-directed R618K mutation in the Stat5 SH2 domain abolished the phosphorylation by Jak2, while deletion of the C terminus led to Stat5 hyperphosphorylation. A single phosphotyrosine-SH2 domain interaction was sufficient for the dimerization of Stat5, but such dimers bound to DNA very inefficiently. Together, our data show that yeast cells are appropriate tools for studying Jak-Stat or Stat-Stat interactions. Our mutational analysis suggests that the Stat5 SH2 domain is essential for the interaction with Jak2 and that the kinase domain of Jak2 is sufficient for Jak2-Stat5 interaction. Therefore, the Jak kinase domain may be all that is needed to cause Stat phosphorylation in situations where receptor docking is dispensable.

Animals↗
PubMed1997

Impaired granulopoiesis, myelodysplasia, and early lethality in CCAAT/enhancer binding protein epsilon-deficient mice.

Polymorphonuclear leukocytes are essential for host defense to infectious diseases. CCAAT/enhancer binding protein epsilon (C/EBP epsilon) is preferentially expressed in granulocytes and lymphoid cells. Mice with a null mutation in C/EBP epsilon develop normally and are fertile but fail to generate functional neutrophils and eosinophils. Opportunistic infections and tissue destruction lead to death by 3-5 months of age. Furthermore, end-stage mice develop myelodysplasia, characterized by proliferation of atypical granulocytes that efface the bone marrow and result in severe tissue destruction. Thus, C/EBP epsilon is essential for terminal differentiation and functional maturation of committed granulocyte progenitor cells.

Animals↗
PubMed1997

STAT5 involvement in the differentiation response of primary chicken myeloid progenitor cells to chicken myelomonocytic growth factor.

We have investigated the activation of the STAT5 protein during the differentiation of myelomonocytic cells. In the human U937 promonocytic cell line, STAT5 activation occurred in response to several inducers of monocytic differentiation (phorbol ester, 1alpha,25-dihydroxyvitamin D3, and retinoic acid). In the promyelocytic HL60 cell line, STAT5 was activated in the course of either phorbol ester-induced monocytic differentiation or DMSO-induced granulocytic differentiation. To test for involvement of STAT5 in the differentiation of primary nonimmortalized cells, chicken myeloid progenitor cells transfected with the ts21-E26 avian retrovirus were studied. At 37 degrees C the temperature-sensitive oncoprotein of the ts21-E26 virus (p135(gag-myb-ets)) installs a differentiation block that is released by a shift to the nonpermissive temperature (42 degrees C). Both proliferation and differentiation of ts21-E26-transfected myeloblasts require the continuous presence of chicken myelomonocytic growth factor (cMGF). Addition of cMGF to growth factor-starved cells rapidly caused STAT5 tyrosine phosphorylation, DNA binding, and transcriptional activity at both permissive and nonpermissive temperatures. Moreover, the temperature shift-induced onset of myelomonocytic differentiation strictly correlated with the appearance of activated STAT5 in ts21-E26-infected myeloblasts, but not in cells infected with wtE26 retrovirus. These data position STAT5 in a nuclear signaling cascade induced by the cMGF receptor and suggest a contribution of STAT5 to the process of myelomonocytic differentiation or to the functional changes that accompany the maturation of myeloid progenitor cells to a terminally differentiated stage.

Amino Acid Sequence↗
PubMed1997

Physical association between STAT1 and the interferon-inducible protein kinase PKR and implications for interferon and double-stranded RNA signaling pathways.

The interferon-inducible double-stranded RNA protein kinase PKR controls protein synthesis through the phosphorylation of eukaryotic translation initiation factor (eIF)-2. In addition to its demonstrated role in translational control, several reports have suggested a transcriptional role for PKR. Here we report that PKR is involved in IFN- and dsRNA-signaling pathways by modulating the function of the signal transducer and activator of transcription STAT1. We also show that PKR associates with STAT1 in mouse and human cells. The association is not a kinase-substrate interaction since STAT1 phosphorylation is not modified by PKR in vitro or in vivo. In addition, the formation of the PKR-STAT1 complex is not dependent upon the enzymatic activity of PKR but does require the dsRNA-binding domain of PKR. Moreover, there is a concomitant decrease in PKR-STAT1 interaction and increase in STAT1 DNA binding in response to IFNs or dsRNA. These findings suggest that PKR plays an important role in IFN and dsRNA-signaling pathways by modulating the transcriptional function of STAT1.

3T3 Cells↗
PubMed1997

[Ductal hyperplasia and ductal carcinoma in situ. Definition--classification--differential diagnosis].

This review emphasizes the pathology of premalignant ductal breast diseases and its practical relevance to the patients management. The histological criteria for recognizing Ductal Hyperplasia (DH) are now well established. These include an intraluminal heterogeneous proliferation of glandular cells positive for keratins 8/18/19 and epithelial cells with expression of keratins 5/6/14. As a hyperplastic process the epithelial cells disclose an haphazard irregular growth with slit like irregular lumina (fenestrated growth pattern). The florid DH indicates a slight subsequent increased risk for cancer development. Our knowledge of the nature of noninvasive ductal neoplasia continues to evolve. Recent molecular genetic and immunohistochemical efforts have disclosed that atypical ductal hyperplasia (ADH) constituted a clonal neoplastic proliferation of an epithelial cell. Histological hallmarks of ADH are their cytologic features of uniformity and monotony of proliferation of cells and its micropapillary, cibriform or solid growth pattern. So from histology ADH simulates the highly differentiated DCIS, but can be distinguished from the latter quantitatively by the aggregate cross sectional diameter or the number of ducts that are completely involved by the atypical proliferation. ADH indicates a few fold subsequent increased risk for developing carcinoma. So this lesion requires a close follow up with 3 to 4 examinations per year and annual mammograms. Ductal carcinoma in situ (DCIS) consists of cytologically malignant cells in the parenchyma that have not invaded into the stroma. Recent studies have shown that DCIS is a heterogeneous group of tumors. Attempts have been made to classify it into histologic patterns, nuclear grades, tumors with or without comedo-necroses etc. We can draw the conclusion from several studies that the most important histologic feature is the nuclear grade. Holland et al. have suggested a very useful classification scheme that includes nuclear grade and histological features. The modifiers of treatment are as follows: 1. nuclear grade or differentiation of the DCIS 2. extension of the lesion 3. excision with clear margins So efforts to classify DCIS underscore the central role of pathology in determining the grade of the DCIS, its size and the adequacy of the surgical excision in terms of free margins. All three parameters are included in a score system of the Van Nuys Prognostic Index.

Breast↗
PubMed1997

[Standardized pathologic examination of breast excision specimen. Relevance within an interdisciplinary practice protocol for quality management of breast saving therapy].

The long-term disease free survival in patients treated by breast conserving therapy is similar to that of patients treated by mastectomy. In breast conserving therapy there is a significant risk of local recurrence. Although local recurrence does not appear to effect survival, there is certainly associated morbidity and attendant emotional trauma. Microscopic evaluation of the margins of lumpectomy specimens is the only way to define the extent of the tumour and the adequacy of resection. We intended to check the influence of standardized handling instructions for pathological examination on the results of histological margin assessment. These instructions are part of a practice protocol for all branches involved in BCT. We compared the results of our standardized margin investigation of 100 cases with the analysis of the margin status of 100 Lumpectomy specimens each from two other periods of time with different handling. Before 1989 only margins where tumor tissue was suspected when checked with the naked eye were investigated microscopically. From 1990 till 1991, margins were evaluated more intensively, but the evaluations were not standardized and did not consider the orientation of the ductal system, which was the base of examination after 1992. In 28% of cases, tumour tissue was found upon the investigation under the microscope, in the margins of lumpectomies where the margins looked clear to the naked eye. In the other periods tumour could be found in the margins in only 2% respectively 12%. Our results verify a strong influence of our practice protocol on the results of the examination of LE specimens: At first there is a higher sensitivity for tumor bearing margins compared with random sampling of margin tissue. Moreover, based on the consideration of the ductal orientation our protocol offers a better chance to detect in situ components of tumor in the margins. Finally with our method we are able to design exactly the tumor bearing margin and therefore we could take part in quality assurance of BCT.

Breast↗
PubMed1997

Jaks, Stats and the immune system.

Changes in gene expression are necessary for an adaptive response of cells to immunological stimuli and thus for their proper function in the context of the immune system. Regulatory inputs usually originate from cell surface receptors and in many cases affect the transcription rates of specific genes by modulating the activity of transcription factors. The Jak-Stat signalling paradigm has received large attention by molecular immunologists because it applies to nuclear signalling by all cytokine receptors. In its simplest form it requires only two protein components downstream of the receptor: Janus family protein tyrosine kinases (Jaks) which are usually receptor-associated, and signal transducer and activator of transcription (Stat) family transcription factors which carry the receptor-generated signal to the nucleus and stimulate gene expression. Here we give a brief overview of both recent progress and open questions concerning the Jak and Stat molecules, their regulation, and the biological implications of their activity.

Animals↗
PubMed1997

GAS elements: a few nucleotides with a major impact on cytokine-induced gene expression.

Gamma interferon activation site (GAS) elements are short stretches of DNA, originally defined as a requirement for the rapid transcriptional induction of genes in response to interferon-gamma (IFN-gamma). The protein complex binding to GAS sequences in IFN-gamma-treated cells, the gamma interferon activation factor (GAF), is a dimer of Stat1, the prototype of a family of cytokine-responsive transcription factors, the signal transducers and activators of transcription. To date, seven different Stats are known (excluding alternatively spliced or processed forms), six of which recognize the same small palindromic consensus sequence TTCN2-4 GAA that defines a GAS element. Because one or several Stats take part in nuclear signaling in response to most cytokines or growth factors, the GAS sequence has changed from being viewed as a specific site for IFN-activated GAF to becoming the general nuclear end of the Jak-Stat signaling pathways. This review focuses on the identification and definition of GAS elements, their interaction with Stat transcription factors, and their contribution to the specificity of cytokine-induced gene expression.

Animals↗
PubMed1996

Activation of Stat 5b in erythroid progenitors correlates with the ability of ErbB to induce sustained cell proliferation.

Self renewal of normal erythroid progenitors is induced by the receptor tyrosine kinase c-ErbB, whereas other receptors (c-Kit/Epo-R) regulate erythroid differentiation. To address possible mechanisms that could explain this selective activity of c-ErbB, we analyzed the ability of these receptors to activate the different members of the Stat transcription factor family. Ligand activation of c-ErbB induced the tyrosine phosphorylation, DNA-binding, and reporter gene transcription of Stat 5b in erythroblasts. In contrast, ligand activation of c-Kit was unable to induce any of these effects in the same cells. Activation of the erythropoietin receptor caused specific DNA-binding of Stat 5b, but failed to induce reporter gene transcription. These biochemical findings correlate perfectly with the selective ability of c-ErbB to cause sustained self renewal in erythroid progenitors.

Base Sequence↗