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Downstream Signalling (downstream + signalling)
Terms modified by Downstream Signalling Selected AbstractsActivation of PLA2 isoforms by cell swelling and ischaemia/hypoxiaACTA PHYSIOLOGICA, Issue 1-2 2006I. H. Lambert Abstract Phospholipase A2 (PLA2) activity is increased in mammalian cells in response to numerous stimuli such as osmotic challenge, oxidative stress and exposure to allergens. The increased PLA2 activity is seen as an increased release of free, polyunsaturated fatty acids, e.g. arachidonic acid and membrane-bound lysophospholipids. Even though arachidonic acid acts as a second messenger in its own most mammalian cells seem to rely on oxidation of the fatty acid into highly potent second messengers via, e.g. cytochrome P450, the cyclo-oxygenase, or the lipoxygenase systems for downstream signalling. Here, we review data that illustrates that stress-induced PLA2 activity involves various PLA2 subtypes and that the PLA2 in question is determined by the cell type and the physiological stress condition. [source] COX-2, but not COX-1, activity is necessary for the induction of perforant path long-term potentiation and spatial learning in vivoEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2008T. R. Cowley Abstract The objectives of this research were to investigate the role played by the enzyme cyclooxygenase (COX) in learning and memory, synaptic plasticity and synaptic transmission in the rat brain in vivo. Male Wistar rats were treated with isoform-selective inhibitors for COX-1 and COX-2, either chronically and tested in the watermaze or acutely before electrophysiological recordings were made. We found a significant impairment in acquisition of the watermaze with inhibition of COX-2. Furthermore, we found COX-2 but not COX-1 inhibition significantly blocked long-term potentiation (LTP) induction but had no effect on already established LTP. Moreover, exogenous replacement of the main metabolite of COX-2 activity, PGE2, was sufficient to restore LTP induction and for normal downstream signalling to ensue, namely extracellular signalling-regulated kinase (ERK)-phosphorylation and c-FOS expression. We conclude that endogenous basal levels of PGE2 resulting from COX-2 but not COX-1 activity are necessary for synaptic plasticity and memory acquisition. [source] The use of membrane translocating peptides to identify sites of interaction between the C5a receptor and downstream effector proteinsIMMUNOLOGY, Issue 4 2004Graham A. Auger Summary The complement fragment C5a is a potent leucocyte chemoattractant and activator, mediating its effects through a G-protein-coupled receptor. Whilst the C-terminal domain of this receptor has been shown to be essential for receptor desensitization and internalization, it is not known which domains couple to the receptor's heterotrimeric G proteins. In this report we have used a membrane translocating sequence (MTS) to examine the effects of the four intracellular domains of the human C5a receptor (C5aR) on the receptor's signalling via G,i family heterotrimeric G proteins in intact RBL-2H3 cells. The results indicate that all of the intracellular domains couple to downstream signalling, with the proximal region of the C terminus being a major binding site and intracellular loop 3 playing a role in G protein activation or receptor desensitization. [source] Prostaglandin F2, stimulates MEK-ERK signalling but decreases the expression of alkaline phosphatase in dental pulp cellsINTERNATIONAL ENDODONTIC JOURNAL, Issue 6 2010M. C. Chang Chang MC, Chen YJ, Lee MY, Lin LD, Wang TM, Chan CP, Tsai YL, Wang CY, Lin BR, Jeng JH. Prostaglandin F2, stimulates MEK-ERK signalling but decreases the expression of alkaline phosphatase in dental pulp cells. International Endodontic Journal, 43, 461,468, 2010. Abstract Aim, To study prostaglandin F2, (PGF2,) receptor expression and downstream signalling in cultured human dental pulp cells and the effect of PGF2, on the alkaline phosphatase (ALP) activity of dental pulp cells. Methodology, Human dental pulp cells were cultured and exposed to PGF2,. The expression of PGF2, (FP) receptors was analysed by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting. The activation of extracellular regulated kinase (ERK) and cAMP responsive element binding protein/activating transcription factor-1 (CREB/ATF-1) signalling was determined by Western blotting. The expression of ALP in pulp cells after exposure to PGF2, was evaluated by ALP staining and PCR. Results, Dental pulp cells expressed FP receptor mRNA and protein. Exposure to PGF2, revealed little cytotoxicity to pulp cells. PGF2, induced both ERK and CREB/ATF-1 phosphorylation in pulp cells. Exposure to PGF2, (>1 ,mol L,1) further decreased the ALP activity and mRNA expression. However, U0126 (an inhibitor of MEK1) showed little preventive effect on the decline of ALP activity in dental pulp cells by PGF2,. Conclusion, PGF2, may potentially activate FP receptors leading to ERK/CREB-ATF-1 activation during its production in inflamed dental pulp. PGF2, attenuated the ALP activity of pulp cells possibly via pathways not solely by MEK/ERK activation. PGF2, is a contributing factor of pulpal inflammation by regulating the activities of pulp cells. [source] Mutations in the signature motif in MutS affect ATP-induced clamp formation and mismatch repairMOLECULAR MICROBIOLOGY, Issue 6 2008Samir Acharya Summary MutS protein dimer recognizes and co-ordinates repair of DNA mismatches. Mismatch recognition by the N-terminal mismatch recognition domain and subsequent downstream signalling by MutS appear coupled to the C-terminal ATP catalytic site, Walker box, through nucleotide-mediated conformational transitions. Details of this co-ordination are not understood. The focus of this study is a conserved loop in Escherichia coli MutS that is predicted to mediate cross-talk between the two ATP catalytic sites in MutS homodimer. Mutagenesis was employed to assess the role of this loop in regulating MutS function. All mutants displayed mismatch repair defects in vivo. Biochemical characterization further revealed defects in ATP binding, ATP hydrolysis as well as effective mismatch recognition. The kinetics of initial burst of ATP hydrolysis was similar to wild type but the magnitude of the burst was reduced for the mutants. Given its proximity to the ATP bound in the opposing monomer in the crystal and its potential analogy with signature motif of ABC transporters, the results strongly suggest that the loop co-ordinates ATP binding/hydrolysis in trans by the two catalytic sites. Importantly, our data reveal that the loop plays a direct role in co-ordinating conformational changes involved in long-range communication between Walker box and mismatch recognition domains. [source] Dimer-induced signal propagation in Spo0AMOLECULAR MICROBIOLOGY, Issue 3 2004K. Muchová Summary Spo0A, the response regulator protein controlling the initiation of sporulation in Bacillus, has two distinct domains, an N-terminal phosphoacceptor (or receiver) domain and a C-terminal DNA-binding (or effector) domain. The phosphoacceptor domain mediates dimerization of Spo0A on phosphorylation. A comparison of the crystal structures of phosphorylated and unphosphorylated response regulators suggests a mechanism of activation in which structural changes originating at the phosphorylatable aspartate extend to the ,4,5,5 surface of the protein. In particular, the data show an important role in downstream signalling for a conserved aromatic residue (Phe-105 in Spo0A), the conformation of which alters upon phosphorylation. In this study, we have prepared a Phe-105 to Ala mutant to probe the contribution of this residue to Spo0A function. We have also made an alanine substitution of the neighbouring residue Tyr-104 that is absolutely conserved in the Spo0As of spore-forming Bacilli. The spo0A(Y104A) and spo0A(F105A) alleles severely impair sporulation in vivo. In vitro phosphorylation of the purified proteins by phosphoramidate is unaffected, but dimerization and DNA binding are abolished by the mutations. We have identified intragenic suppressor mutations of spo0A(F105A) and shown that these second-site mutations in the purified proteins restore phosphorylation-dependent dimer formation. Our data support a model in which dimerization and signal transduction between the two domains of Spo0A are mediated principally by the ,4,5,5 signalling surface in the receiver domain. [source] Post-translational modification of host proteins in pathogen-triggered defence signalling in plantsMOLECULAR PLANT PATHOLOGY, Issue 4 2008IRIS J. E. STULEMEIJER SUMMARY Microbial plant pathogens impose a continuous threat to global food production. Similar to animals, an innate immune system allows plants to recognize pathogens and swiftly activate defence. To activate a rapid response, receptor-mediated pathogen perception and subsequent downstream signalling depends on post-translational modification (PTM) of components essential for defence signalling. We discuss different types of PTMs that play a role in mounting plant immunity, which include phosphorylation, glycosylation, ubiquitination, sumoylation, nitrosylation, myristoylation, palmitoylation and glycosylphosphatidylinositol (GPI)-anchoring. PTMs are rapid, reversible, controlled and highly specific, and provide a tool to regulate protein stability, activity and localization. Here, we give an overview of PTMs that modify components essential for defence signalling at the site of signal perception, during secondary messenger production and during signalling in the cytoplasm. In addition, we discuss effectors from pathogens that suppress plant defence responses by interfering with host PTMs. [source] Oncogenic and ligand-dependent activation of KIT/PDGFRA in surgical samples of imatinib-treated gastrointestinal stromal tumours (GISTs),THE JOURNAL OF PATHOLOGY, Issue 1 2009T Negri Abstract As the range of receptor tyrosine kinase (RTK) inhibitors widens, a detailed understanding of the activating mechanisms of KIT/platelet-derived growth factor receptor (PDGFR)A and the related downstream pathways involved in the development and maintenance of GISTs is becoming increasingly important. We analysed areas with different histological response ratios in surgical specimens taken from imatinib-treated and untreated GIST patients in order to investigate KIT and PDGFRA expression/activation, the presence of their cognate ligands and the activation of downstream signalling, by means of biochemistry, immunohistochemistry and flow cytometry. All of the cases showed KIT and PDGFRA co-expression. In addition to the oncogenic activation of mutated receptors, activation of wild-type KIT and wild-type PDGFRA, sustained by heterodimerization and an autocrine,paracrine loop, was demonstrated by the presence of their specific ligands, stem cell factor (SCF) and PDGFA. To confirm RTK activation further, all of the samples (including those with the highest regression ratios) were investigated for downstream effectors, and all proved to have activated downstream signalling. The results show that after the mutated receptors are switched off, heterologous wild-type receptors become important in imatinib-treated GISTs as a means of maintaining signalling activation. Taken together, our findings suggest that drugs targeting wild-type receptors should be tested in imatinib-treated GIST patients. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] Regulation of bone morphogenetic protein signalling in human pulmonary vascular development,THE JOURNAL OF PATHOLOGY, Issue 1 2008M Southwood Abstract The bone morphogenetic protein (BMP) type II receptor (BMPR-II) is predominantly expressed on the vascular endothelium in the adult lung. Although mutations in BMPR-II are known to underlie many cases of familial pulmonary arterial hypertension (FPAH), little is known regarding the expression of BMPs and their signalling pathways during normal lung development or the impact of BMPR-II mutations on endothelial cell function. We determined the cellular localization and expression levels of BMP4, BMP receptors, and activation of downstream signalling via phospho-Smad1 in a developmental series of human embryonic and fetal lungs by immunohistochemistry. The expression of BMP4 and BMP receptors was temporally and spatially regulated during lung development. BMPR-II expression correlated with phosphorylation of tissue Smad1 and was highest during the late pseudoglandular and early canalicular stage of lung development, when vasculogenesis is intense. Phospho-Smad1 expression was associated with markers of proliferation in endothelial cells. In vitro studies confirmed that BMPs 2 and 4 induced phosphorylation of Smad1/5 and pulmonary artery endothelial cell (PAEC) migration and proliferation. Adenoviral transfection of PAECs with mutant kinase-deficient BMPR-II, or siRNA knockdown of BMPR-II, inhibited Smad signalling and the proliferative response to BMP4. Our findings support a critical role for BMPs in lung vasculogenesis. Dysfunctional BMP signalling in PAECs during development may lead to abnormal pulmonary vascular development and contribute to the pathogenesis of FPAH. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] Crystallization and preliminary crystallographic studies of human RIG-I in complex with double-stranded RNAACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2009Hyunjin Moon Retinoic acid inducible gene-I (RIG-I) is an essential component of the innate immune system that is responsible for the detection and elimination of invading viruses. RIG-I recognizes viral RNAs inside the cell and then initiates downstream signalling to activate the IRF-3 and NF-,B genes, which results in the production of type I interferons. RIG-I is composed of an N-terminal CARD domain for signalling and C-terminal helicase and repressor domains for RNA recognition. A RIG-I,RNA binding assay was performed to investigate the in vitro RIG-I,RNA binding properties. Selenomethionine-incorporated RIG-I was expressed using Escherichia coli and purified for crystallization. X-ray data were collected from RIG-I,dsRNA complex crystals to 2.8,Ĺ resolution using synchrotron radiation. [source] CLINICAL QUESTION: What is the best management strategy for patients with severe insulin resistance?CLINICAL ENDOCRINOLOGY, Issue 3 2010Robert K. Semple Summary Management of severe insulin resistance (IR) is a major clinical challenge in many patients with obesity or lipodystrophy, and also in rarer patients with proven or suspected genetic defects in the insulin receptor or downstream signalling. The latter group can present at any time between birth and early adult life, with a variable clinical course broadly correlated with the severity of IR. Primary insulin signalling defects are usually associated with poor weight gain rather than obesity. Initially, extreme hyperinsulinaemia produces ovarian enlargement and hyperandrogenism in women, and often fasting or postprandial hypoglycaemia. However, any hypoglycaemia gradually evolves into insulin-resistant hyperglycaemia when beta cell function declines. Optimal management of these complex disorders depends on early diagnosis and appropriate targeting of both high and low glucose levels. In newborns, continuous nasogastric feeding may reduce harmful glycaemic fluctuations, and in older patients, acarbose may mitigate postprandial hypoglycaemia. Insulin sensitization, initially with metformin but later with trials of additional agents such as thiazolidinediones, is the mainstay of early therapy, but insulin replacement, eventually with very high doses, is required once diabetes has supervened. Preliminary data suggest that rhIGF-1 can improve survival in infants with the most severe insulin receptor defects and also improve beta cell function in older patients with milder receptoropathies. The utility of newer therapies such as glucagon-like peptide-1 agonists and dipeptidyl peptidase-IV inhibitors remains untested in this condition. Thus, management of these patients remains largely empirical, and there is a pressing need to collate data centrally to optimize treatment algorithms. [source] | |||||||||||||