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Berlin Brandenburg

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  • Brenner, Birgit  (11)
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  • 1
    Language: English
    In: Cell, 1997, Vol.91(5), pp.605-615
    Description: Invasion of human mucosal cells by N. gonorrhoeae via the binding to heparansulfate proteoglycan receptors is considered a crucial event of the infection. Using different human epithelial cells and primary fibroblasts, we show here an activation of the phosphatidylcholine-specific phospholipase C (PC-PLC) and acidic sphingomyelinase (ASM) by N. gonorrhoeae, resulting in the release of diacylglycerol and ceramide. Genetic and/or pharmacological blockade of ASM and PC-PLC cause inhibition of cellular invasion by N. gonorrhoeae. Complementation of ASM-deficient fibroblasts from Niemann-Pick disease patients restored N. gonorrhoeae-induced signaling and entry processes. The activation of PC-PLC and ASM, therefore, is an essential requirement for the entry of N. gonorrhoeae into distinct nonphagocytic human cell types including several epithelial cells and primary fibroblasts.
    Keywords: Biology
    ISSN: 0092-8674
    E-ISSN: 1097-4172
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  • 2
    Language: English
    In: Journal of Biological Chemistry, 08/29/1997, Vol.272(35), pp.22173-22181
    Description: In the present study, we show that Fas receptor ligation or cellular treatment with synthetic C sub(6)-ceramide results in activation or phosphorylation, respectively, of the small G-protein Rac1, Jun N-terminal kinase (JNK)/p38 kinases (p38-K), and the transcription factor GADD153. A signaling cascade from the Fas receptor via ceramide, Ras, Rac1, and JNK/p38-K to GADD153 is demonstrated employing transfection of transdominant inhibitory N17Ras, N17Rac1, c-Jun, or treatment with a specific p38-K inhibitor. The critical function of this signaling cascade is indicated by prevention of Fas- or C sub(6)-ceramide-induced apoptosis after inhibition of Ras, Rac1, or JNK/p38-K.
    Keywords: Apoptosis ; Apoptosis ; Fas Antigen ; Ceramide ; Rac1 Protein ; Jnk Protein ; P38 Protein ; Gadd153 Protein ; Fas Antigen ; Gadd153 Protein ; Jnk Protein ; Rac1 Protein ; Ceramide ; P38 Protein;
    ISSN: 0021-9258
    E-ISSN: 1083-351X
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  • 3
    Language: English
    In: Journal of Biological Chemistry, 10/18/1996, Vol.271(42), pp.26389-26394
    Description: Fas induces apoptosis in lymphocytes via a poorly defined intracellular signaling mechanism. We and others have previously demonstrated the involvement and significance of a signaling cascade from the Fas receptor via sphingomyelinases and ceramide to Ras in apoptosis (Gulbins, E., Bissonette, R., Mahboubi, A., Nishioka, W., Brunner, T., Baier G., Baier-Bitterlich, G., Byrd, C., Lang, F., Kolesnick, R., Altman, A., and Green, D. (1995) Immunity 2, 341; Cifone, M. G., DeMaria, R., Roncali, P., Rippo, M. R., Azuma, M., Lanier, L. L., Santoni, A., and Testi, R. (1994) J. Exp. Med. 180, 1547-1552; Gill, B. M., Nishikata, H., Chan, G., Delovitch, T. L., and Ochi, A. (1994) Immunol. Rev. 142, 113-126). Here, we demonstrate an activation of the small G-proteins Rac 1 and Rac 2 after Fas receptor triggering. Expression of a transdominant inhibitory Ras mutant (N17Ras) prevents Rac 1 and Rac 2 stimulation, suggesting a signaling cascade from the Fas receptor via Ras to Rac 1 and Rac 2. Genetic and pharmacological inhibition of Ras or Rac 1 and Rac 2 stimulation blocks Fas-induced apoptosis, pointing to an important function of a Ras and Rac protein-regulated signaling pathway in Fas-mediated programmed cell death.
    Keywords: Chemistry ; Anatomy & Physiology;
    ISSN: 0021-9258
    E-ISSN: 1083-351X
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  • 4
    Language: English
    In: FEBS Letters, 1997, Vol.417(3), pp.301-306
    Description: The interaction of the CD40 receptor with its ligand has been shown to be crucial for the activation of B-lymphocytes. Here, we provide evidence that the pg39 molecule/CD40 ligand (gp39/CD40L) also functions as a stimulatory molecule for T-lymphocytes. Activation of T-lymphocytes via gp39/CD40L induced a strong activation of Jun-N-terminal kinase (JNK) and p38-K. Activation of these kinases correlates with a stimulation of Rac1 and inhibition of Rac1 prevents gp39/CD40L triggered JNK/p38-K activation. Further, cellular stimulation via the CD40 ligand results in tyrosine phosphorylation of cellular proteins and the activation of p56(lck). Inhibition of src-like kinases inhibits Rac1 as well as JNK/p38-K stimulation suggesting a signalling cascade from the gp39/CD40L via p56(lck) and Rac1 to JNK/p38-K.
    Keywords: Cd40 Ligand ; Gp39 ; T-Lymphocytes ; Tyrosine Kinase ; Jun-N-Terminal Kinase ; Biology ; Chemistry ; Anatomy & Physiology
    ISSN: 0014-5793
    E-ISSN: 1873-3468
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  • 5
    In: Pediatric Research, 1998, Vol.44(6), p.946
    Description: Obstruction of narrow vessels by rigid neutrophils may contribute to ischemic organ injury. In septicemia, a substantial portion of the neutrophils may become activated and the number of circulating immature neutrophils may rise sharply. Volume and deformability of mature (PMN) and immature neutrophils in healthy preterm and full-term infants and in septicemic neonates were studied by means of a micropipette system. Membrane cytoplasm tongues were aspirated into 2.5-microm (diameter) pipettes over a period of 60 s. Volume and tongue growth of mature resting PMN were similar in healthy preterm and full-term neonates and adults. Compared with mature PMN (about 360 fl), the volumes of band cells (415 fl), metamyelocytes (470 fl), and less mature cells (myeloblasts, promyelocytes, and myelocytes; 490 fl) were significantly increased (p 〈 0.005). Final tongue lengths of band cells, metamyelocytes, and less mature cells were decreased by about 50, 60, and 70%, respectively, when compared with passive mature cells. In septic neonates, the percentage of immature neutrophils was increased, but the deformability and volume of the cell subpopulations were not affected by septicemia. Active PMN were characterized by pseudopod formation. More active PMN were found in group B streptococcal (14% of total PMN), gram-negative (12%), and Staphylococcus epidermidis septicemia (8%) than in healthy neonates and adults (4%). The main bodies of active PMN were less deformable than passive PMN, and the pseudopods showed very little membrane deformation. The increased number of rigid active and immature neutrophils may contribute to impaired microcirculation and the high risk for organ injury in septic patients.
    Keywords: Hemorheology ; Infant, Newborn -- Blood ; Neutrophils -- Physiology ; Sepsis -- Blood;
    ISSN: 0031-3998
    E-ISSN: 15300447
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  • 6
    In: Journal of Leukocyte Biology, February 1998, Vol.63(2), pp.253-263
    Description: We demonstrate a rapid and transient activation of phosphoinositide-3-kinase (PI-3-K) by Fas receptor triggering or cellular treatment with synthetic C6-ceramide. The stimulation of PI-3-K is critical for Fas or C6-ceramide-induced programmed cell death because transfection with a transdominant inhibitory PI-3-K construct or pre-treatment with the PI-3-K inhibitor wortmannin almost completely prevented Fas or C6-ceramide-mediated apoptosis. Treatment with the caspase inhibitor Ac-YVAD-cmk or cellular transfection with transdominant inhibitory N17Ras prevented PI-3-K stimulation by Fas, suggesting that Fas activates PI-3-K via caspases and Ras. N17Ras expression also prevented C6-ceramide-initiated PI-3-K stimulation. The notion of a PI-3-K regulation by Ras upon Fas receptor ligation or ceramide treatment is supported by co-immunoprecipitation experiments revealing an activation-dependent association of PI-3-K and Ras.
    Keywords: Apoptosis ; Cd95/Fas/Apo‐1 ; T Lymphocytes
    ISSN: 0741-5400
    E-ISSN: 1938-3673
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  • 7
    Language: English
    In: Biochemical and Biophysical Research Communications, 09 October 1997, Vol.239(1), pp.68-73
    Description: The lymphocyte integrin alpha4beta7 is a cell surface adhesion receptor involved in initiating lymphocyte homing to gut-associated/mucosal lymphoid tissues by binding the mucosal addressin cell adhesion molecule-1 (MAdCAM-1). Other known ligands are vascular cell adhesion molecule-1, fibronectin, and the alpha4 integrin chain itself. Here, we demonstrate that stimulation of the alpha4beta7 integrin through its alpha4 subunit (mAb R1-2), beta7 subunit (mAb M293), or the combinatory epitope (mAb DATK32) enhances tyrosine phosphorylation of several cellular proteins in the murine TK1 lymphoma cell line. The two src-kinases p56lck and p59fyn were identified as possible mediators and substrates of the detected tyrosine phosphorylation. Furthermore, we observed activation of the MAP-kinases ERK1/2. Copyright 1997 Academic Press.
    Keywords: Biology ; Chemistry ; Anatomy & Physiology
    ISSN: 0006-291X
    E-ISSN: 1090-2104
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  • 8
    Language: English
    In: Biochemical and Biophysical Research Communications, 24 February 1997, Vol.231(3), pp.802-807
    Description: L-selectin mediated adhesion to endothelial cells is a crucial step in the immune response to pathogens (1, 2) and in lymphocyte homing (3, 4). Selectin molecules mediate leukocyte rolling on endothelial cells, the initial step of adhesion (5, 6). We have previously shown that stimulation of Jurkat T-lymphocytes via L-selectin results in activation of the p21Ras pathway and synthesis of reactive oxygen intermediates (7). Here, we show that cellular stimulation via L-selectin induces a change of cytoskeleton organisation demonstrated by a tenfold increase of actin filament polymerisation. This actin polymerisation is mediated by a Ras and Rac2 regulated pathway, since inhibition of Ras by transient transfection of transdominant inhibitory N17Ras or suppression of Rac2 protein expression by antisense oligonucleotides prevents L-selectin triggered actin polymerisation. Our results point to a signaling cascade from L-selectin via Ras and Rac2 to actin filaments, which might be important for leukocyte adhesion.
    Keywords: Biology ; Chemistry ; Anatomy & Physiology
    ISSN: 0006-291X
    E-ISSN: 1090-2104
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  • 9
    Language: English
    In: Cellular Signalling, 1999, Vol.11(4), pp.301-308
    Description: Leucocyte adhesion to endothelial cells is a tightly regulated process involving selectins, integrins and immunoglobulin-like proteins. Cell adhesion and communication are controlled by membrane dynamics like receptor capping. Capping of surface receptors is an ubiquitous mechanism but still not well understood. Employing immunofluorescence techniques, we demonstrate that l -selectin triggering results in receptor capping of the l -selectin molecules in lymphocytes. Using pharmacological inhibitors and genetic deficient cell lines we show that this process involves intracellular signalling molecules. l -Selectin capping seems to be independent on activation of p56 lck -kinase, but requires the neutral sphingomyelinase, small G proteins and the cytoskeleton. Therefore, capping of l -selectin upon stimulation might play an important role in the very early phase of lymphocyte trafficking.
    Keywords: L-Selectin ; Adhesion ; Capping ; Signal Transduction ; Lymphocytes ; Neutral Sphingomyelinase ; Biology
    ISSN: 0898-6568
    E-ISSN: 1873-3913
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  • 10
    Language: English
    In: Biochemical and Biophysical Research Communications, 09 October 1997, Vol.239(1), pp.11-17
    Description: The activation of B-lymphocytes depends critically on the interaction of the CD40 receptor with its ligand. Here, we provide evidence that the CD40 ligand (CD40L) also functions as a direct stimulatory molecule for T-lymphocytes. Activation of T-lymphocytes via CD40L induces tyrosine phosphorylation of cellular proteins including PLCgamma. Tyrosine phosphorylation of PLCgamma correlates with an IP3- and Ca2+-release and an activation of PKC. Inhibition of src-like tyrosine kinases by Herbimycin A prevents these activation events suggesting a crucial role of tyrosine phosphorylation in T-lymphocyte activation via CD40L. Copyright 1997 Academic Press.
    Keywords: Cd40 Ligand ; Gp39 ; T-Lymphocytes ; Tyrosine Kinases ; Pkc ; Biology ; Chemistry ; Anatomy & Physiology
    ISSN: 0006-291X
    E-ISSN: 1090-2104
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