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Signal Transduction Pathways (signal + transduction_pathway)
Kinds of Signal Transduction Pathways Selected AbstractsSignal Transduction Pathways in Enhanced Microvascular PermeabilityMICROCIRCULATION, Issue 6 2000SARAH Y. YUAN ABSTRACT We have been investigating the molecular mechanisms underlying pathophysiological regulation of microvascular permeability on isolated venules and cultured venular endothelial monolayers. Physiological approaches have been employed in combination with molecular analyses to probe the signal transduction pathways leading to enhanced microvascular permeability. A newly developed technique of protein transfection into cells and intact microvessels enables the correlation of functional reactions and signaling events at the molecular level in a direct and specific fashion. The results indicate that inflammatory mediators increase microvascular permeability via intracellular signaling pathways involving the activation of phospholipase C, cytosolic calcium, protein kinase C, nitric oxide synthase, guanylate cyclase, and protein kinase G. In response to the signaling stimulation, complex biochemical and conformational reactions occur at the endothelial structural proteins. Specifically, myosin light-chain activation-mediated myosin light-chain phosphorylation can result in cell contraction. VE-cadherin and ,-catenin phosphorylation may induce dissociation of the junctional proteins and their connection to the cytoskeleton, leading to a loose or opened intercellular junction. Focal adhesion phosphorylation and redistribution further provide an anchorage support for the conformational changes in the cells and at the cell junction. The three processes may act in concert to facilitate the flux of fluid and macromolecules across the microvascular endothelium. [source] Signal Transduction Pathways Involved in Brain Death-Induced Renal InjuryAMERICAN JOURNAL OF TRANSPLANTATION, Issue 5 2009H. R. Bouma Kidneys derived from brain death organ donors show an inferior survival when compared to kidneys derived from living donors. Brain death is known to induce organ injury by evoking an inflammatory response in the donor. Neuronal injury triggers an inflammatory response in the brain, leading to endothelial dysfunction and the release of cytokines in the circulation. Serum levels of interleukin-6, -8, -10, and monocyte chemoattractant protein-1 (MCP-1) are increased after brain death. Binding with cytokine-receptors in kidneys stimulates activation of nuclear factor-kappa B (NF-,B), selectins, adhesion molecules and production of chemokines leading to cellular influx. Mitogen-activated protein kinases (MAP-kinases) mediate inflammatory responses and together with NF-,B they seem to play an important role in brain death induced renal injury. Altering the activation state of MAP-kinases could be a promising drug target for early intervention to reduce cerebral injury related donor kidney damage and improve outcome after transplantation. [source] Signal transduction pathways that function in both development and innate immunityDEVELOPMENTAL DYNAMICS, Issue 5 2010Frederick A. Partridge Abstract C. elegans is developing in importance as a model for innate immunity. Several signaling pathways are known to be required for immune responses to a diverse range of pathogens, including the insulin signaling, p38 MAP kinase and transforming growth factor-, pathways. These pathways also have roles during development, which can complicate the analysis of their functions in immunity. Recent studies have suggested that immunity in C. elegans is integrated across the organism by both paracrine and neuronal communication, showing the complexity of the immune system in this organism. Developmental Dynamics 239:1330,1336, 2010. © 2010 Wiley-Liss, Inc. [source] Two-component signal transduction in human fungal pathogensFEMS YEAST RESEARCH, Issue 2 2006Michael Kruppa Abstract Signal transduction pathways provide mechanisms for adaptation to stress conditions. One of the most studied of these pathways is the HOG1 MAP kinase pathway that in Saccharomyces cerevisiae is used to adapt cells to osmostress. The HOG1 MAPK has also been studied in Candida albicans, and more recently observations on the Hog1p functions have been described in two other human pathogens, Aspergillus fumigatus and Cryptococcus neoformans. The important, but not surprising, concept is that this pathway is used for different yet similar functions in each of these fungi, given their need to adapt to different environmental signals. Current studies of C. albicans focus upon the identification of two-component signal proteins that, in both C. albicans and S. cerevisiae, regulate the HOG1 MAPK. In C. albicans, these proteins regulate cell wall biosynthesis (and, therefore, adherence to host cells), osmotic and oxidant adaptation, white-opaque switching, morphogenesis, and virulence of the organism. [source] Signal transduction pathways involved in interaction of galactosylceramide/sulfatide-containing liposomes with cultured oligodendrocytes and requirement for myelin basic protein and glycosphingolipidsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 7 2008Joan M. Boggs Abstract We showed previously that the addition to cultured oligodendrocytes (OLs) of multivalent carbohydrate in the form of liposomes containing the two major glycosphingolipids (GSLs) of myelin, galactosylceramide (GalC) and cerebroside sulfate (Sulf), or galactose conjugated to bovine serum albumin caused clustering of GalC on the extracellular surface and myelin basic protein (MBP) on the cytosolic surface. Multivalent carbohydrate also caused depolymerization of actin microfilaments and microtubules, indicating that interaction of the carbohydrate with the OL surface transmits a transmembrane signal to the cytoskeleton. In the present study we show that inhibition of GSL synthesis with fumonisin B1 prevents clustering of MBP in GalC/Sulf-negative oligodendrocytes, suggesting that GSLs are required for the effect. Because the effects of multivalent carbohydrate resemble those caused by the addition of anti-GalC/Sulf antibodies to OLs and because GalC and Sulf can interact with each other by trans carbohydrate,carbohydrate interactions across apposed membranes, these results support the conclusion that the OL receptor for GalC/Sulf in liposomes is GalC/Sulf in the OL membrane. Inhibition of MBP expression using MBP siRNA inhibited GalC clustering, suggesting that MBP is required for the effect. We also investigate the signal transduction pathways involved using a number of enzyme inhibitors. These indicated that the Akt and p42/p44 MAPK pathways, Rho GTPases, and GSK-3, are involved, consistent with their known involvement in regulation of the cytoskeleton. These interactions between GalC/Sulf-containing liposomes and the OL membrane may mimic interactions between GalC/Sulf-enriched signaling domains when OL cell membranes or the extracellular surfaces of compact myelin come into contact. © 2008 Wiley-Liss, Inc. [source] Signal transduction pathways involved in the stimulation of tissue type plasminogen activator by interleukin-1, and Porphyromonas gingivalis in human osteosarcoma cellsJOURNAL OF PERIODONTAL RESEARCH, Issue 5 2006Yu-Chao Chang Background:, Recently, evidences have shown that tissue type plasminogen activator (t-PA) may play an important role in the pathogenesis of periodontal diseases. However, the mechanisms and signal transduction pathways involved in the production of t-PA in human osteosarcoma cells are not fully understood. Objectives:, The purpose of this study was to investigate the caseinolytic activity in human osteosarcoma cell line U2OS cells stimulated with interleukin-1, (IL-1,) or Porphyromonas gingivalis in the absence or presence of p38 inhibitor SB203580, mitogen-activated protein kinase kinase (MEK) inhibitor U0126, and phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002. Methods:, IL-1, and the supernatants of P. gingivalis were used to evaluate the caseinolytic activity in U2OS cells by using casein zymography and enzyme-linked immunosorbent assay (ELISA). Furthermore, to search possible signal transduction pathways, SB203580, U0126, and LY294002 were added to test how they modulated the caseinolytic activity. Results:, Casein zymography exhibited a caseinolytic band with a molecular weight of approximately 70 kDa, suggestive of the presence of t-PA. Secretion of t-PA was found to be stimulated with IL-1, and P. gingivalis during a 2-day culture period (p < 0.05). From the results of casein zymography and ELISA, SB203580, U0126, and LY294002 significantly reduced the IL-1, or P. gingivalis -stimulated t-PA production, respectively (p < 0.05). Conclusions:, Our findings demonstrated that IL-1, and P. gingivalis enhance t-PA production in human osteosarcoma cells, and that the signal transduction pathways p38, MEK, and PI3K are involved in the inhibition of t-PA. SB203580, U0126, and LY294002 suppress t-PA production and/or activity and may therefore be valuable therapeutics in t-PA-mediated periodontal destruction, and might be proved clinically useful agents, in combination with standard treatment modalities, in the treatment of periodontitis. [source] An inversion in the wiring of an intercellular signal: evolution of Wnt signaling in the nematode vulvaBIOESSAYS, Issue 8 2005Marie-Anne Félix Signal transduction pathways are largely conserved throughout the animal kingdom. The repertoire of pathways is limited and each pathway is used in different intercellular signaling events during the development of a given animal. For example, Wnt signaling is recruited, sometimes redundantly with other molecular pathways, in four cell specification events during Caenorhabditis elegans vulva development, including the activation of vulval differentiation. Strikingly,a recent study finds that Wnts act to repress vulval differentiation in the nematode Pristionchus pacificus,1 demonstrating evolutionary flexibility in the use of intercellular signaling pathways. BioEssays 27:765,769, 2005. © 2005 Wiley Periodicals, Inc. [source] Differential sensitivity to apoptosis between the human small and large intestinal mucosae: Linkage with segment-specific regulation of Bcl-2 homologs and involvement of signaling pathways,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2001Rémy Gauthier Abstract The small and large intestines differ in their expression profiles of Bcl-2 homologs. Intestinal segment-specific Bcl-2 homolog expression profiles are acquired as early as by mid-gestation (18,20 weeks) in man. In the present study, we examined the question whether such distinctions underlie segment-specific control mechanisms of intestinal cell survival. Using mid-gestation human jejunum and colon organotypic cultures, we analyzed the impact of growth factors (namely insulin; 10 ,g/ml) and pharmacological compounds that inhibit signal transduction molecules/pathways (namely tyrosine kinases, Fak, PI3-K/Akt, and MEK/Erk) on cell survival and Bcl-2 homolog expression (anti-apoptotic: Bcl-2, Bcl-XL, Mcl-1; pro-apoptotic: Bax, Bak, Bad). The relative activation levels of p125Fak, p42Erk-2, and p57Akt were analyzed as well. Herein, we report that (1) the inhibition of signal transduction molecules/pathways revealed striking differences in their impact on cell survival in the jejunum and colon (e.g., the inhibition of p125Fak induced apoptosis with a significantly greater extent in the jejunum [,43%] than in the colon [,24%]); (2) sharp distinctions between the two segments were noted in the modulatory effects of the various treatments on Bcl-2 homolog steady-state levels (e.g., inhibition of tyrosine kinase activities in the jejunum down-regulated all anti-apoptotics analyzed while increasing Bax, whereas the same treatment in the colon down-regulated Bcl-XL only and increased all pro-apoptotics); and (3) in addition to their differential impact on cell survival and Bcl-2 homolog expression, the MEK/Erk and PI3-K/Akt pathways were found to be distinctively regulated in the jejunum and colon mucosae (e.g., insulin in the jejunum increased p42Erk-2 activation without affecting that of p57Akt, whereas the sa e treatment in the colon decreased p42Erk-2 activation while increasing that of p57Akt). Altogether, these data show that intestinal cell survival is characterized by segment-specific susceptibilities to apoptosis, which are in turn linked with segmental distinctions in the involvement of signaling pathways and the regulation of Bcl-2 homolog steady-state levels. Therefore, these indicate that cell survival is subject to segment-specific control mechanisms along the proximal-distal axis of the intestine. J. Cell. Biochem. 82: 339,355, 2001. © 2001 Wiley-Liss, Inc. [source] Gonadotropin-releasing hormone-1 (GnRH-1) is involved in tooth maturation and biomineralization,DEVELOPMENTAL DYNAMICS, Issue 11 2007Jean Tiong Abstract Gonadotropin releasing-hormone-1 (GnRH-1) is expressed in mouse incisors during development. In this report, we identify (1) cell type(s) that express GnRH-1 throughout tooth development, (2) the GnRH-1 receptor, and (3) the role of GnRH-1/GnRH-1 receptor signaling in tooth maturation. Results show that GnRH-1-positive cells in dental epithelium differentiate and populate multiple tooth structures including ameloblast and papillary layers that are involved in enamel formation and mineralization. The GnRH-1 receptor was present, and in vitro a GnRH-1 antagonist attenuated incisor GnRH-1 cell expression. In vivo, in mice lacking GnRH-1 (,/,), the incisors were discolored, longer, and more curved compared to wildtype. Elemental analysis of calcium, phosphorus, and iron revealed changes in ,/, incisors consistent with GnRH-1 affecting movement of minerals into the dental matrix. In sum, in tooth development a signal transduction pathway exists for GnRH-1 via the GnRH-1 receptor and disruption of such signaling affects incisor growth and biomineralization. Developmental Dynamics 236:2980,2992, 2007. Published 2007 Wiley-Liss, Inc. [source] MAPK signal transduction pathway mediates agrin effects on neurite elongation in cultured hippocampal neuronsDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2003Lisa Karasewski Abstract We have previously shown that agrin regulates the rates of axonal and dendritic elongation by modulating the expression of microtubule-associated proteins in cultured hippocampal neurons. However, the mechanisms by which agrin-induced signals are propagated to the nucleus where they can lead to the phosphorylation, and hence the activation, of transcription factors, are not known. In the present study, we identified downstream elements that play essential roles in the agrin-signaling pathway in developing central neurons. Our results indicate that agrin induces the combined activation of the extracellular signal-regulated kinases (ERK1/ERK2) and p38 in central neurons. In addition, they showed that PD98059 and SB202190, synthetic inhibitors of ERK1/ERK2 and p38 respectively, prevented the changes in the rate of neurite elongation induced by agrin in cultured hippocampal neurons. Collectively, these results suggest that agrin might modulate the expression of neuron-specific genes involved in neurite elongation by inducing CREB phosphorylation through the activation of the MAPK signal transduction pathway in cultured hippocampal neurons. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 14,24, 2003 [source] Preconditioning and postconditioning: new strategies for cardioprotectionDIABETES OBESITY & METABOLISM, Issue 6 2008D. J. Hausenloy Despite optimal therapy, the morbidity and mortality of coronary heart disease (CHD) remains significant, particularly in patients with diabetes or the metabolic syndrome. New strategies for cardioprotection are therefore required to improve the clinical outcomes in patients with CHD. Ischaemic preconditioning (IPC) as a cardioprotective strategy has not fulfilled it clinical potential, primarily because of the need to intervene before the index ischaemic event, which is impossible to predict in patients presenting with an acute myocardial infarction (AMI). However, emerging studies suggest that IPC-induced protection is mediated in part by signalling transduction pathways recruited at time of myocardial reperfusion, creating the possibility of harnessing its cardioprotective potential by intervening at time of reperfusion. In this regard, the recently described phenomenon of ischaemic postconditioning (IPost) has attracted great interest, particularly as it represents an intervention, which can be applied at time of myocardial reperfusion for patients presenting with an AMI. Interestingly, the signal transduction pathways, which underlie its protection, are similar to those recruited by IPC, creating a potential common cardioprotective pathway, which can be recruited at time of myocardial reperfusion, through the use of appropriate pharmacological agents given as adjuvant therapy to current myocardial reperfusion strategies such as thrombolysis and primary percutaneous coronary intervention for patients presenting with an AMI. This article provides a brief overview of IPC and IPost and describes the common signal transduction pathway they both appear to recruit at time of myocardial reperfusion, the pharmacological manipulation of which has the potential to generate new strategies for cardioprotection. [source] Insulino-mimetic and anti-diabetic effects of vanadium compoundsDIABETIC MEDICINE, Issue 1 2005A. K. Srivastava Abstract Compounds of the trace element vanadium exert various insulin-like effects in in vitro and in vivo systems. These include their ability to improve glucose homeostasis and insulin resistance in animal models of Type 1 and Type 2 diabetes mellitus. In addition to animal studies, several reports have documented improvements in liver and muscle insulin sensitivity in a limited number of patients with Type 2 diabetes. These effects are, however, not as dramatic as those observed in animal experiments, probably because lower doses of vanadium were used and the duration of therapy was short in human studies as compared with animal work. The ability of these compounds to stimulate glucose uptake, glycogen and lipid synthesis in muscle, adipose and hepatic tissues and to inhibit gluconeogenesis, and the activities of the gluconeogenic enzymes: phosphoenol pyruvate carboxykinase and glucose-6-phosphatase in the liver and kidney as well as lipolysis in fat cells contributes as potential mechanisms to their anti-diabetic insulin-like effects. At the cellular level, vanadium activates several key elements of the insulin signal transduction pathway, such as the tyrosine phosphorylation of insulin receptor substrate-1, and extracellular signal-regulated kinase 1 and 2, phosphatidylinositol 3-kinase and protein kinase B activation. These pathways are believed to mediate the metabolic actions of insulin. Because protein tyrosine phosphatases (PTPases) are considered to be negative regulators of the insulin-signalling pathway, it is suggested that vanadium can enhance insulin signalling and action by virtue of its capacity to inhibit PTPase activity and increase tyrosine phosphorylation of substrate proteins. There are some concerns about the potential toxicity of available inorganic vanadium salts at higher doses and during long-term therapy. Therefore, new organo-vanadium compounds with higher potency and less toxicity need to be evaluated for their efficacy as potential treatment of human diabetes. [source] Protein kinase C and the development of diabetic vascular complicationsDIABETIC MEDICINE, Issue 12 2001K. J. Way Abstract Hyperglycemic control in diabetes is key to preventing the development and progression of vascular complications such as retinopathy, nephropathy and neuropathy. Increased activation of the diacylglycerol (DAG)-protein kinase C (PKC) signal transduction pathway has been identified in vascular tissues from diabetic animals, and in vascular cells exposed to elevated glucose. Vascular abnormalities associated with glucose-induced PKC activation leading to increased synthesis of DAG include altered vascular blood flow, extracellular matrix deposition, basement membrane thickening, increased permeability and neovascularization. Preferential activation of the PKC, isoform by elevated glucose is reported to occur in a variety of vascular tissues. This has lead to the development of LY333531, a PKC, isoform specific inhibitor, which has shown potential in animal models to be an orally effective and nontoxic therapy able to produce significant improvements in diabetic retinopathy, nephropathy, neuropathy and cardiac dysfunction. Additionally, the antioxidant vitamin E has been identified as an inhibitor of the DAG-PKC pathway, and shows promise in reducing vascular complications in animal models of diabetes. Given the overwhelming evidence indicating a role for PKC activation in contributing to the development of diabetic vascular complications, pharmacological therapies that can modulate this pathway, particularly with PKC isoform selectivity, show great promise for treatment of vascular complications, even in the presence of hyperglycemia. Diabet. Med. 18, 945,959 (2001) [source] The natural furanone (5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone disrupts quorum sensing-regulated gene expression in Vibrio harveyi by decreasing the DNA-binding activity of the transcriptional regulator protein luxRENVIRONMENTAL MICROBIOLOGY, Issue 10 2007Tom Defoirdt Summary This study aimed at getting a deeper insight in the molecular mechanism by which the natural furanone (5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone disrupts quorum sensing in Vibrio harveyi. Bioluminescence experiments with signal molecule receptor double mutants revealed that the furanone blocks all three channels of the V. harveyi quorum sensing system. In further experiments using mutants with mutations in the quorum sensing signal transduction pathway, the compound was found to block quorum sensing-regulated bioluminescence by interacting with a component located downstream of the Hfq protein. Furthermore, reverse transcriptase real-time polymerase chain reaction with specific primers showed that there was no effect of the furanone on luxRVh mRNA levels in wild-type V. harveyi cells. In contrast, mobility shift assays showed that in the presence of the furanone, significantly lower levels of the LuxRVh response regulator protein were able to bind to its target promoter sequences in wild-type V. harveyi. Finally, tests with purified LuxRVh protein also showed less shifts with furanone-treated LuxRVh, whereas the LuxRVh concentration was found not to be altered by the furanone (as determined by SDS-PAGE). Therefore, our data indicate that the furanone blocks quorum sensing in V. harveyi by rendering the quorum sensing master regulator protein LuxRVh unable to bind to the promoter sequences of quorum sensing-regulated genes. [source] Interaction between halogenated aromatic compounds in the Ah receptor signal transduction pathwayENVIRONMENTAL TOXICOLOGY, Issue 5 2004Guosheng Chen Abstract Many toxic and biochemical responses to halogenated aromatic compounds (HACs) such as polychlorinated biphenyls (PCBs) and polychlorinated dibenzo- p -dioxins (PCDDs) are mediated through the aryl hydrocarbon receptor (AhR), which is an intracellular cytosolic target for HACs. Environmental exposure to HACs almost always involves complex mixtures of congeners, some of which can antagonize the action of potent HACs such as 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD). In this work we studied TCDD and representative PCB congeners, alone and in mixture, for their effect on CYP1A gene transcription and protein levels in primary rat hepatocytes. Together with our previous work, our results suggest that formation of the Ah receptor-ligand-DRE (dioxin response element) complex is the principal point of divergence in the mechanism between an AhR agonist and an AhR antagonist. The coplanar PCBs 77 and 126 and the mono- ortho PCB 156 were full agonists toward CYP1A1 gene transcription and CYP1A protein levels, showing typical additive behavior with TCDD to the target molecule AhR. In contrast, the nonplanar PCB 153 antagonized the action of TCDD, even at concentrations that occupied a significant fraction of AhR molecules. Competitive inhibition explains the commonly reported decrease of ethoxyresorufin- O -deethylase (EROD) activity when PCBs are present in high concentrations and the antagonism of PCBs to the EROD activity of TCDD. The result is that Western blotting offers a much more reliable measure of CYP1A protein concentration than does the EROD assay, despite the greater convenience of the latter. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 480,489, 2004. [source] Context-specific modulation of cocaine-induced locomotor sensitization and ERK and CREB phosphorylation in the rat nucleus accumbensEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2009Marcelo T. Marin Abstract Learned associations are hypothesized to develop between drug effects and contextual stimuli during repeated drug administration to produce context-specific sensitization that is expressed only in the drug-associated environment and not in a non-drug-paired environment. The neuroadaptations that mediate such context-specific behavior are largely unknown. We investigated context-specific modulation of cAMP-response element-binding protein (CREB) phosphorylation and that of four upstream kinases in the nucleus accumbens that phosphorylate CREB, including extracellular signal-regulated kinase (ERK), cAMP-dependent protein kinase, calcium/calmodulin-dependent kinase (CaMK) II and CaMKIV. Rats received seven once-daily injections of cocaine or saline in one of two distinct environments outside their home cages. Seven days later, test injections of cocaine or saline were administered in either the paired or the non-paired environment. CREB and ERK phosphorylation were assessed with immunohistochemistry, and phosphorylation of the remaining kinases, as well as of CREB and ERK, was assessed by western blotting. Repeated cocaine administration produced context-specific sensitized locomotor responses accompanied by context-specific enhancement of the number of cocaine-induced phosphoCREB-immunoreactive and phosphoERK-immunoreactive nuclei in a minority of neurons. In contrast, CREB and CaMKIV phosphorylation in nucleus accumbens homogenates were decreased by cocaine test injections. We have recently shown that a small number of cocaine-activated accumbens neurons mediate the learned association between cocaine effects and the drug administration environment to produce context-specific sensitization. Context-specific phosphorylation of ERK and CREB in the present study suggests that this signal transduction pathway is selectively activated in the same set of cocaine-activated accumbens neurons that mediate this learned association. [source] Phosphorylation of voltage-gated ion channels in rat olfactory receptor neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2001Christian H. Wetzel Abstract In olfactory receptor neurons (ORNs), ligand,odorant receptor interactions cause G protein-mediated activation of adenylate cyclase and a subsequent increase in concentration of the intracellular messenger cAMP. Odorant-evoked elevation in cAMP is thought to directly activate a cation-selective cyclic nucleotide-gated channel, which causes external Ca2+ influx, leading to membrane depolarization and the generation of action potentials. Our data show that in freshly dissociated rat ORNs, odorant-induced elevation in cAMP also activates cAMP-dependent protein kinase (PKA), which is then able to phosphorylate various protein targets in the olfactory signal transduction pathway, specifically voltage-gated sodium and calcium channels. The presence of PKI (PKA inhibitor peptide) blocked the modulatory action of cAMP on voltage-gated ion channels. By modulating the input/output properties of the sensory neurons, this mechanism could take part in the complex adaptation process in odorant perception. In addition, we found modulation of voltage-gated sodium and calcium channel currents by 5-hydroxytryptamine and the dopamine D1 receptor agonist SKF 38393. These findings suggest that in situ ORNs might also be a target for efferent modulation. [source] Human lactoferrin activates NF-,B through the Toll-like receptor 4 pathway while it interferes with the lipopolysaccharide-stimulated TLR4 signalingFEBS JOURNAL, Issue 9 2010Ken Ando Lactoferrin (LF) has been implicated in innate immunity. Here we reveal the signal transduction pathway responsible for human LF (hLF)-triggered nuclear factor-,B (NF-,B) activation. Endotoxin-depleted hLF induces NF-,B activation at physiologically relevant concentrations in the human monocytic leukemia cell line, THP-1, and in mouse embryonic fibroblasts (MEFs). In MEFs, in which both tumor necrosis factor receptor-associated factor 2 (TRAF2) and TRAF5 are deficient, hLF causes NF-,B activation at a level comparable to that seen in wild-type MEFs, whereas TRAF6-deficient MEFs show significantly impaired NF-,B activation in response to hLF. TRAF6 is known to be indispensable in leading to NF-,B activation in myeloid differentiating factor 88 (MyD88)-dependent signaling pathways, while the role of TRAF6 in the MyD88-independent signaling pathway has not been clarified extensively. When we examined the hLF-dependent NF-,B activation in MyD88-deficient MEFs, delayed, but remarkable, NF-,B activation occurred as a result of the treatment of cells with hLF, indicating that both MyD88-dependent and MyD88-independent pathways are involved. Indeed, hLF fails to activate NF-,B in MEFs lacking Toll-like receptor 4 (TLR4), a unique TLR group member that triggers both MyD88-depependent and MyD88-independent signalings. Importantly, the carbohydrate chains from hLF are shown to be responsible for TLR4 activation. Furthermore, we show that lipopolysaccharide-induced cytokine and chemokine production is attenuated by intact hLF but not by the carbohydrate chains from hLF. Thus, we present a novel model concerning the biological function of hLF: hLF induces moderate activation of TLR4-mediated innate immunity through its carbohydrate chains; however, hLF suppresses endotoxemia by interfering with lipopolysaccharide-dependent TLR4 activation, probably through its polypeptide moiety. [source] Hypoxia-inducible factor-1, blocks differentiation of malignant gliomasFEBS JOURNAL, Issue 24 2009Huimin Lu Aberrant differentiation is a characteristic feature of neoplastic transformation, while hypoxia in solid tumors is believed to be linked to aggressive behavior and poor prognosis. However, the possible relationship between hypoxia and differentiation in malignancies remains poorly defined. Here we show that rat C6 and primary human malignant glioma cells can be induced to differentiate into astrocytes by the well-known adenylate cyclase activator forskolin. However, hypoxia-inducible factor-1, expression stimulated by the hypoxia mimetics cobalt chloride or deferoxamine blocks this differentiation and this effectiveness is reversible upon withdrawal of the hypoxia mimetics. Importantly, knockdown of hypoxia inducible factor-1, by RNA interference restores the differentiation capabilities of the cells, even in the presence of cobalt chloride, whereas stabilization of hypoxia-inducible factor-1, through retarded ubiquitination by von Hippel-Lindau tumor suppressor gene silence abrogates the induced differentiation. Moreover, targeting of HIF-1 using chetomin, a disrupter of HIF-1 binding to its transcriptional co-activator CREB-binding protein (CBP)/p300, abolishes the differentiation-inhibitory effect of hypoxia-inducible factor-1,. Administration of chetomin in combination with forskolin significantly suppresses malignant glioma growth in an in vivo xenograft model. Analysis of 95 human glioma tissues revealed an increase of hypoxia-inducible factor-1, protein expression with progressing tumor grade. Taken together, these findings suggest a key signal transduction pathway involving hypoxia-inducible factor-1, that contributes to a differentiation defect in malignant gliomas and sheds new light on the differentiation therapy of solid tumors by targeting hypoxia-inducible factor-1,. Structured digital abstract ,,MINT-7292117: CBP (uniprotkb:Q6JHU9) physically interacts (MI:0915) with Hif1a (uniprotkb:O35800) by anti bait coimmunoprecipitation (MI:0006) [source] Phosphorylation of NF-,B proteins by cyclic GMP-dependent kinaseFEBS JOURNAL, Issue 10 2003A noncanonical pathway to NF-, B activation The transcription factor NF-,B is activated in cellular stress responses. This requires rapid regulation of its function, which is accomplished, in part, by various modes of phosphorylation. Even though diverse DNA binding subunits of NF-,B proteins may transactivate from distinct recognition sequences, the differential regulation of transcription from the large number of NF-,B responsive sites in various gene promoters and enhancers has been incompletely understood. The cyclic GMP-dependent kinase (PKG) is an important mediator of signal transduction that may induce gene expression through cAMP response element binding protein (CREB) and through other, yet undefined, mechanisms. We have previously characterized a signal transduction pathway that leads to activation-induced cell death in T-lymphocytes and involves the activation of PKG. Here we demonstrate that the NF-,B proteins p65, p49 (also called p52), and p50 are specific substrates for this kinase. PKG dose-dependently increases the transactivating activity of p65 from the NF-,B consensus sequence. It also mediates dose-dependently an increase in transcriptional activity by p49 or p50 from a unique CCAAT/enhance binding protein (C/EBP)-associated NF-,B site, but not from the consensus site. Phosphorylation of p65, p50, or p49 does not alter their subcellular distribution. Because the release of cytosolic p65/p50 heterodimers into the nucleus is by itself insufficient to differentiate all the numerous NF-,B promoter sequences, phosphorylation of the DNA-binding subunits reveals a form of differential regulation of NF-,B activity and it implies a novel pathway for PKG-induced gene transcription. These observations may bear on mechanisms of programmed cell death in T-lymphocytes. They may also be relevant to ongoing efforts to induce cancer cell apoptosis through activation of PKG. [source] Transmitting the signal of excess nitrogen in Saccharomyces cerevisiae from the Tor proteins to the GATA factors: connecting the dotsFEMS MICROBIOLOGY REVIEWS, Issue 3 2002Terrance G. Cooper Abstract Major advances have recently occurred in our understanding of GATA factor-mediated, nitrogen catabolite repression (NCR)-sensitive gene expression in Saccharomyces cerevisiae. Under nitrogen-rich conditions, the GATA family transcriptional activators, Gln3 and Gat1, form complexes with Ure2, and are localized to the cytoplasm, which decreases NCR-sensitive expression. Under nitrogen-limiting conditions, Gln3 and Gat1 are dephosphorylated, move from the cytoplasm to the nucleus, in wild-type but not rna1 and srp1 mutants, and increase expression of NCR-sensitive genes. ,Induction' of NCR-sensitive gene expression and dephosphorylation of Gln3 (and Ure2 in some laboratories) when cells are treated with rapamycin implicates the Tor1/2 signal transduction pathway in this regulation. Mks1 is posited to be a negative regulator of Ure2, positive regulator of retrograde gene expression and to be itself negatively regulated by Tap42. In addition to Tap42, phosphatases Sit4 and Pph3 are also argued by some to participate in the regulatory pathway. Although a treasure trove of information has recently become available, much remains unknown (and sometimes controversial) with respect to the precise biochemical functions and regulatory pathway connections of Tap42, Sit4, Pph3, Mks1 and Ure2, and how precisely Gln3 and Gat1 are prevented from entering the nucleus. The purpose of this review is to provide background information needed by students and investigators outside of the field to follow and evaluate the rapidly evolving literature in this exciting field. [source] Chronic exposure to increasing background ozone impairs stomatal functioning in grassland speciesGLOBAL CHANGE BIOLOGY, Issue 6 2009GINA MILLS Abstract Two species found in temperate calcareous and mesotrophic grasslands (Dactylis glomerata and Leontodon hispidus) were exposed to eight ozone treatments spanning preindustrial to post-2100 regimes, and late-season effects on stomatal functioning were investigated. The plants were grown as a mixed community in 14 L containers and were exposed to ozone in ventilated solardomes (dome-shaped greenhouses) for 20 weeks from early May to late September 2007. Ozone exposures were based on O3 concentrations from a nearby upland area, and provided the following seasonal 24 h means: 21.4, 39.9 (simulated ambient), 50.2, 59.4, 74.9, 83.3, 101.3 and 102.5 ppb. In both species, stomatal conductance of undamaged inner canopy leaves developing since a midseason cutback increased linearly with increasing background ozone concentration. Imposition of severe water stress by leaf excision indicated that increasing background ozone concentration decreased the ability of leaves to limit water loss, implying impaired stomatal control. The threshold ozone concentrations for these effects were 15,40 ppb above current ambient in upland UK, and were within the range of ozone concentrations anticipated for much of Europe by the latter part of this century. The potential mechanism behind the impaired stomatal functioning was investigated using a transpiration assay. Unlike for lower ozone treatments, apparently healthy green leaves of L. hispidus that had developed in the 101.3 ppb treatment did not close their stomata in response to 1.5 ,m abscisic acid (ABA); indeed stomatal opening initially occurred in this treatment. Thus, ozone appears to be disrupting the ABA-induced signal transduction pathway for stomatal control thereby reducing the ability of plants to respond to drought. These results have potentially wide-reaching implications for the functioning of communities under global warming where periods of soil drying and episodes of high vapour pressure deficit are likely to be more severe. [source] Activation of eNOS in rat portal hypertensive gastric mucosa is mediated by TNF-, via the PI 3-kinase,Akt signaling pathwayHEPATOLOGY, Issue 2 2002Hirofumi Kawanaka Activation of endothelial nitric oxide synthase (eNOS) in portal hypertensive (PHT) gastric mucosa leads to hyperdynamic circulation and increased susceptibility to injury. However, the signaling mechanisms for eNOS activation in PHT gastric mucosa and the role of TNF-, in this signaling remain unknown. In PHT gastric mucosa we studied (1) eNOS phosphorylation (at serine 1177) required for its activation; (2) association of the phosphatidylinositol 3-kinase (PI 3-kinase), and its downstream effector Akt, with eNOS; and, (3) whether TNF-, neutralization affects eNOS phosphorylation and PI 3-kinase,Akt activation. To determine human relevance, we used human microvascular endothelial cells to examine directly whether TNF-, stimulates eNOS phosphorylation via PI 3-kinase. PHT gastric mucosa has significantly increased (1) eNOS phosphorylation at serine 1177 by 90% (P < .01); (2) membrane translocation (P < .05) and phosphorylation (P < .05) of p85 (regulatory subunit of PI 3-kinase) by 61% and 85%, respectively; (3) phosphorylation (P < .01) and activity (P < .01) of Akt by 40% and 52%, respectively; and (4) binding of Akt to eNOS by as much as 410% (P < .001). Neutralizing anti,TNF-, antibody significantly reduced p85 phosphorylation, phosphorylation and activity of Akt, and eNOS phosphorylation in PHT gastric mucosa to normal levels. Furthermore, TNF-, stimulated eNOS phosphorylation in human microvascular endothelial cells. In conclusion, these findings show that in PHT gastric mucosa, TNF-, stimulates eNOS phosphorylation at serine 1177 (required for its activation) via the PI 3-kinase,Akt signal transduction pathway. [source] ,-Interferons and the single nucleotide polymorphisms: A milestone to tailor-made therapy for chronic hepatitis CHEPATOLOGY RESEARCH, Issue 5 2010Yasuhito Tanaka Type III interferons (IFN) (IFN-,1, -,2, -,3/interleukin [IL]-29, -28A, -28B) are cytokines with type I IFN-like antiviral activities. Most cells have expressed both type I and III IFN following Toll-like receptor (TLR) stimulation or viral infection, whereas the ability of cells to respond to IFN-, was restricted to a specific subset of cells. It was reported that signal transduction pathway of IFN-, was similar to that of IFN-,/, although a receptor adapted by IFN-, were distinct from that of IFN-,/,. However, the clinical significance and the role of each IFN-, were unclear. Recent genome-wide association studies (GWAS) of the human whole genome revealed several single nucleotide polymorphism sites (SNP) strongly associated with the response to pegylated IFN-, (PEG-IFN) plus ribavirin (RBV) treatment in chronic hepatitis C patients. The SNP, which are located near the IL-28B gene of chromosome 19, were discovered simultaneously by three independent studies opening a new prospective in hepatitis C research. The present review highlights significant insights that can be derived from the GWAS approach, and summarizes current knowledge of in vitro and in vivo study on the role of IFN-, in antiviral effect. [source] Hereditary Degenerative Retinopathies: Optimism for Somatic Gene TherapyIUBMB LIFE, Issue 6 2000Barkur S. Shastry Abstract Retinitis pigmentosa comprises a large and exceptionally heterogeneous group of hereditary disorders of the retina. As a result of an extensive investigation around the world, primary genetic lesions have been described in many genes. Some of these genes encode enzymes that are involved in the signal transduction pathway. On the basis of in vitro functional assays and standard transgenic and knock-out experiments, it has been proposed that normal cell functions are disrupted because of an abnormal protein-folding and metabolic errors or structural defects in the membrane. This ultimately leads to a gene-mediated cell death known as apoptosis. Various gene transfer approaches using mouse models further suggest that the degeneration can be rescued to some extent. Although many questions remain to be answered, investigations during the last 10 years have enormously increased our understanding of this exceptionally heterogeneous disorder and give hope for an effective gene therapy and a possible cure. [source] Ochratoxin A impairs Nrf2-dependent gene expression in porcine kidney tubulus cellsJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 5 2009C. Boesch-Saadatmandi Summary The mycotoxin, ochratoxin A (OTA), which is produced by Aspergillus and Penicillium subspecies, is frequently present in feedstuffs. Ochratoxin A exhibits a wide range of toxic activities including nephrotoxicity. However, the underlying molecular mechanisms of OTA-induced cellular nephrotoxicity have yet not been fully elucidated. Nrf2 is a basic leucine zipper transcriptional activator essential for the coordinated transcriptional induction of antioxidant and xenobiotic metabolizing enzymes in the kidney. Therefore, in the present study, the effects of OTA on the nuclear translocation and transactivation of the transcription factor Nrf2 as well as mRNA levels of Nrf2 target genes including glutathione- S -transferase and ,-glutamylcysteinyl synthetase have been studied in cultured porcine kidney tubulus cells (LLC-PK1). Nrf2 was induced by sulforaphane, a well-known activator of this transcription factor. Ochratoxin A significantly decreased ,-glutamylcysteinyl synthetase and glutathione- S -transferase mRNA levels in LLC-PK1 cells. Decreased mRNA levels of ,-glutamylcysteinyl synthetase and glutathione- S -transferase were accompanied by a lowered nuclear translocation and transactivation of Nrf2. Furthermore, OTA also lowered Nrf2 mRNA levels. Current data indicate that OTA nephrotoxicity may be, at least partly, mediated by an Nrf2-dependent signal transduction pathway. [source] Inactivation of Pten in Osteo-Chondroprogenitor Cells Leads to Epiphyseal Growth Plate Abnormalities and Skeletal Overgrowth,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2007Alice Fiona Ford-Hutchinson Abstract To study the role of the Pten tumor suppressor in skeletogenesis, we generated mice lacking this key phosphatidylinositol 3,-kinase pathway regulator in their osteo-chondroprogenitors. A phenotype of growth plate dysfunction and skeletal overgrowth was observed. Introduction: Skeletogenesis is a complex process relying on a variety of ligands that activate a range of intracellular signal transduction pathways. Although many of these stimuli are known to activate phosphatidylinositol 3,-kinase (PI3K), the function of this pathway during cartilage development remains nebulous. To study the role of PI3K during skeletogenesis, we used mice deficient in a negative regulator of PI3K signaling, the tumor suppressor, Pten. Materials and Methods:Pten gene deletion in osteo-chondrodroprogenitors was obtained by interbreeding mice with loxP-flanked Pten exons with mice expressing the Cre recombinase under the control of the type II collagen gene promoter (Ptenflox/flox:Col2a1Cre mice). Phenotypic analyses included microcomputed tomography and immunohistochemistry techniques. Results: ,CT revealed that Ptenflox/flox:Col2a1Cre mice exhibited both increased skeletal size, particularly of vertebrae, and massive trabeculation accompanied by increased cortical thickness. Primary spongiosa development and perichondrial bone collar formation were prominent in Ptenflox/flox:Col2a1Cre mice, and long bone growth plates were disorganized and showed both matrix overproduction and evidence of accelerated hypertrophic differentiation (indicated by an altered pattern of type X collagen and alkaline phosphatase expression). Consistent with increased PI3K signaling, Pten-deficient chondrocytes showed increased phospho-PKB/Akt and phospho-S6 immunostaining, reflective of increased mTOR and PDK1 activity. Interestingly, no significant change in growth plate proliferation was seen in Pten-deficient mice, and growth plate fusion was found at 6 months. Conclusions: By virtue of its ability to modulate a key signal transduction pathway responsible for integrating multiple stimuli, Pten represents an important regulator of both skeletal size and bone architecture. [source] TNF-,-mediated signal transduction pathway is a major determinant of apoptosis in dilated cardiomyopathyJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 7 2010Samarjit Das Abstract Although J2N-k strain of cardiomyopathic hamsters is an excellent model of dilated cardiomyopathy, the presence and mechanisms of apoptosis in the hearts of these genetically modified animals have not been investigated. This study examined the hypothesis that cardiac dysfunction and apoptosis in the cardiomyopathic hamsters were associated with tumour necrosis factor-alpha (TNF-,)-mediated signalling pathway involving the activation of some pro-apoptotic proteins and/or deactivation of some antiapoptotic proteins. Echocardiographic assessment of 31-week-old hamsters indicated an increase in the internal dimension of the left ventricle as well as decreases in the ejection fraction, fractional shortening and cardiac output without any evidence of cardiac hypertrophy. Increased level of TNF-, and apoptosis in cardiomyopathic hearts were accompanied by increased protein content for protein kinase C (PKC) -, and -, isozymes as well as caspases 3 and 9. Phosphorylated protein content for p38 MAPK and NF,B was increased whereas that for Erk1/2, BAD and Bcl-2 was decreased in cardiomyopathic hearts. These results support the view that TNF-, and PKC isozymes may promote apoptosis due to the activation of p38 MAPK and deactivation of Erk1/2 pathways, and these changes may contribute toward the development of cardiac dysfunction in dilated cardiomyopathy. [source] BCCIP associates with the receptor protein tyrosine phosphatase PTPµJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 4 2008Polly J. Phillips-Mason Abstract The receptor protein tyrosine phosphatase PTPµ belongs to a family of adhesion molecules that contain cell,cell adhesion motifs in their extracellular segments and catalytic domains within their intracellular segments. The ability of PTPµ both to mediate adhesion and exhibit enzymatic activity makes PTPµ an excellent candidate to transduce signals in response to cell,cell adhesion. In an effort to identify downstream signaling partners of PTPµ, we performed a modified yeast two-hybrid screen using the first tyrosine phosphatase domain of PTPµ as bait. We isolated an interacting clone encoding BRCA2 and CDKN1A interacting protein (BCCIP) from a HeLa cell library. BCCIP is a p21 and BRCA2 interacting protein that has been shown to play roles in both cell cycle arrest and DNA repair. In this manuscript, we confirm the interaction between BCCIP and PTPµ identified in yeast using in vitro biochemical studies and characterize BCCIP as a PTPµ binding protein. We demonstrate that BCCIP is phosphorylated by the Src tyrosine kinase and dephosphorylated by the PTPµ tyrosine phosphatase in vitro. Furthermore, we show that BCCIP is required for both the permissive and repulsive functions of PTPµ in neurite outgrowth assays, suggesting BCCIP and PTPµ are in a common signal transduction pathway. J. Cell. Biochem. 105: 1059,1072, 2008. © 2008 Wiley-Liss, Inc. [source] Effects of tyroserleutide on gene expression of calmodulin and PI3K in hepatocellular carcinoma,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2008Lan Zhao Abstract Tyroserleutide (YSL) is a tripeptide compound that has exhibited inhibitory effects on hepatocellular carcinoma in our previous research. The mechanism of this antitumor activity involves the second messenger, Ca2+. Ca2+ influences cell function through the Ca2+/calmodulin (CaM) pathway, and abnormality of the Ca2+/CaM system correlates closely with the occurrence of tumors. In addition, CaM associates with phosphatidylinositol 3 kinase (PI3K), thereby enhancing the activity of PI3K, which promotes cell proliferation. In order to investigate its anti-tumor mechanism, we studied the effects of YSL on CaM protein expression and mRNA level, PI3K activity, PI3K regulatory subunit p85 protein expression and mRNA level, and the mRNA level of PI3K catalytic subunits p110, and p110, in human hepatocellular carcinoma BEL-7402 xenograft tumors in nude mice. Our results showed that YSL decreased the mRNA level and protein expression of CaM, inhibited the activity of PI3K, and reduced the mRNA level and protein expression of the PI3K regulatory subunit p85 and mRNA level of PI3K catalytic subunits p110, and p110,. Accordingly, it is suggestive that the anti-tumor effects of YSL may be mediated by down regulation of CaM and PI3K subunits p85 and p110, influencing the signal transduction pathway in the tumor cells and perhaps overcoming the dysfunctional PI3K activity in tumors. J. Cell. Biochem. 103: 471,478, 2008. © 2007 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||||||||||||||||||||