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Regulatory Step (regulatory + step)
Selected AbstractsCD1d and CD1d-restricted iNKT-cells play a pivotal role in contact hypersensitivityEXPERIMENTAL DERMATOLOGY, Issue 4 2005Edward E. S. Nieuwenhuis Abstract:, CD1d-restricted T-cells are activated by glycolipids presented by the major histocompatibility complex class-Ib molecule CD1d, found on the surface of antigen-presenting cells (APC). This interaction between APC, most notably dendritic cells (DC), and CD1d-restricted T-cells is an important regulatory step in the initiation of adaptive immune responses. It is well known that DC play a crucial role in the induction of contact hypersensitivity (CHS), a frequently studied form of in vivo T-cell-mediated immunity. In this study, we show that CD1d-restricted T-cells are also necessary for CHS, because both wild-type mice treated systemically or topically with CD1d glycolipid antagonists and CD1d-restricted T-cell-null mice have markedly diminished CHS responses. Thus, pharmacologic antagonists of CD1d can be used as effective inhibitors of CHS, a prototype for a variety of delayed-type tissue hypersensitivity responses. [source] Evidence for a role of the N-terminal domain in subcellular localization of the neuronal connexin36 (Cx36)JOURNAL OF NEUROSCIENCE RESEARCH, Issue 4 2002G. Zoidl Abstract The expression and functional properties of connexin36 (Cx36) have been investigated in two neuroblastoma cell lines (Neuro2A, RT4-AC) and primary hippocampal neurons transfected with a Cx36-enhanced green fluorescent protein (EGFP) expression vector. Transfected cells express Cx36-EGFP mRNA, and Cx36-EGFP protein is localized in the perinuclear area and cell membrane. Upon differentiation of cell lines, Cx36-EGFP protein was detectable in processes with both axonal and dendritic characteristics. Small gap junction plaques were found between adjacent cells, and electrophysiological recordings demonstrated that the electrical properties of these gap junctions were virtually indistinguishable from those reported for native Cx36. Mutagenesis of Cx36 led to the identification of a structural element that interferes with normal protein localization. In contrast, site directed mutagenesis of putative protein phosphorylation motifs did not alter subcellular localization. This excludes phosphorylation/dephosphorylation as a major regulatory step in Cx36 protein transport. © 2002 Wiley-Liss, Inc. [source] Regulation of virulence gene expression in Vibrio cholerae by quorum sensing: HapR functions at the aphA promoterMOLECULAR MICROBIOLOGY, Issue 4 2002Gabriela Kovacikova Summary Quorum sensing negatively influences virulence gene expression in certain toxigenic Vibrio cholerae strains. At high cell densities, the response regulator LuxO fails to reduce the expression of HapR, which, in turn, represses the expression of the virulence cascade. A critical regulatory step in the cascade is activation of tcpPH expression by AphA and AphB. We show here that HapR influences the virulence cascade by directly repressing aphA expression. In strain C6706, aphA expression was increased in a ,hapR mutant and decreased in a ,luxO mutant, indicating a negative and positive influence, respectively, of these gene products on the promoter. Overexpression of HapR also reduced aphA expression in both C6706 and Escherichia coli. DNase I footprinting showed that purified HapR binds to the aphA promoter between ,85 and ,58. Although it appears that quorum sensing does not influence virulence gene expression in strain O395 solely because of a frameshift in hapR, overproduced HapR did not repress expression from the O395 aphA promoter in either Vibrio or E. coli, nor did the protein bind to the promoter. Two basepair differences from C6706 are present in the O395 HapR binding site at ,85 and ,77. Introducing the ,77 change into C6706 prevented HapR binding and repression of aphA expression. This mutation also eliminated the repression of toxin-co-regulated pilus (TCP) and cholera toxin (CT) that occurs in a ,luxO mutant, indicating that HapR function at aphA is critical for density-dependent regulation of virulence genes. [source] Modulation of Ca2+ signalling in rat atrial myocytes: possible role of the ,1c carboxyl terminalTHE JOURNAL OF PHYSIOLOGY, Issue 2 2003Sun-Hee Woo Ca2+ influx through L-type Cav1.2 (,1c) Ca2+ channels is a critical step in the activation of cardiac ryanodine receptors (RyRs) and release of Ca2+ via Ca2+ -induced Ca2+ release(CICR). The released Ca2+, in turn, is the dominant determinant of inactivation of the Ca2+ current (ICa) and termination of release. Although Ca2+ cross-signalling is mediated by high Ca2+ fluxes in the microdomains of ,1c -RyR complexes, ICa -gated Ca2+ cross-signalling is surprisingly resistant to intracellular Ca2+ buffering and has steeply voltage-dependent gain, inconsistent with a strict CICR mechanism, suggesting the existence of additional regulatory step(s). To explore the possible regulatory role of the carboxyl (C)-terminal tail of ,1c in modulating Ca2+ signalling, we tested the effects of introducing two ,1c C-terminal peptides, LA (1571,1599) and K (1617,1636) on the central ,1c -unassociated Ca2+ -release sites of atrial myocytes, using rapid (240 Hz) two-dimensional confocal Ca2+ imaging. The frequency of spontaneously activating central sparks increased by approximately fourfold on dialysing LA- but not K-peptide into myocytes voltage-clamped at -80 mV. The rate but not the magnitude of caffeine (10 mM)-triggered central Ca2+ release was significantly accelerated by LA- but not K-peptide. Individual Ca2+ spark size and flux were larger in LA- but not in K-peptide-dialysed myocytes. Although LA-peptide did not change the amplitude or inactivation kinetics of ICa, LA-peptide did strongly enhance the central Ca2+ transients triggered by ICa at -30 mV (small ICa) but not at +20 mV (large ICa). In contrast, K-peptide had no effect on either ICa or the local Ca2+ transients. LA-peptide with a deleted calmodulin-binding region (LM1-peptide) had no significant effects on the central spark frequency but suppressed spontaneous spark frequency in the periphery. Our results indicate that the calmodulin-binding LA motif of the ,1c C-terminal tail may sensitize the RyRs, thereby increasing their open probability and providing for both the voltage-dependence of CICR and the higher frequency of spark occurrence in the periphery of atrial myocytes where the native ,1c -RyR complexes are intact. [source] RFI2, a RING-domain zinc finger protein, negatively regulates CONSTANS expression and photoperiodic floweringTHE PLANT JOURNAL, Issue 5 2006Mingjie Chen Summary The red and far-red light-absorbing phytochromes interact with the circadian clock, a central oscillator that sustains a 24-h period, to measure accurately seasonal changes in day-length and regulate the expression of several key flowering genes. The interactions and subsequent signalling steps upstream of the flowering genes such as CONSTANS (CO) and FLOWERING LOCUS T (FT) remain largely unknown. We report here that a photomorphogenic mutant, red and far-red insensitive 2-1 ( rfi2-1), flowered early particularly under long days. The rfi2-1 mutation also enhanced the expression of CO and FT under day/night cycles or constant light. Both co-2 and gigantea-2 (gi-2) were epistatic to rfi2-1 in their flowering responses. The gi-2 mutation was also epistatic to the rfi2-1 mutation in the expression of CO and hypocotyl elongation. However, the rfi2-1 mutation did not affect the expression of GI, a gene that mediates between the circadian clock and the expression of CO. Like many other flowering genes, the expression of RFI2 oscillated under day/night cycles and was rhythmic under constant light. The amplitude of the rhythmic expression of RFI2 was significantly reduced in phyB-9 or lhy-20 plants, and was also affected by the gi-2 mutation. As previously reported, the gi-2 mutation affects the period length and amplitude of CCA1 and LHY expression, and GI may act through a feedback loop to maintain a proper circadian function. We propose a regulatory step in which RFI2 represses the expression of CO, whereas GI may maintain the proper expression of RFI2 through its positive action on the circadian clock. The regulatory step serves to tune the circadian outputs that control the expression of CO and photoperiodic flowering. [source] Localization and targeting of the VP14 epoxy-carotenoid dioxygenase to chloroplast membranesTHE PLANT JOURNAL, Issue 5 2001Bao-Cai Tan Summary Abscisic acid (ABA) is a key regulator of seed dormancy and plant responses to environmental challenges. ABA is synthesized via an oxidative cleavage of 9- cis epoxy-carotenoids, the first committed and key regulatory step in the ABA biosynthetic pathway. Vp14 of maize encodes an epoxy-carotenoid dioxygenase that is soluble when expressed in E. coli. An important goal has been to determine how the soluble VP14 protein is targeted to epoxy-carotenoid substrates that are located in the thylakoid and envelope membranes of chloroplasts and other plastids. Using an in vitro chloroplast import assay, we have shown that VP14 is imported into chloroplasts with cleavage of a short stroma-targeting domain. The mature VP14 exists in two forms, one which is soluble in stroma and the other bound to thylakoid membranes. Analysis of a series of truncated VP14 mutants mapped the membrane targeting signal to the 160 amino acid N-terminal sequence. A putative amphipathic ,-helix within this region is essential, but not sufficient, for the membrane targeting. Either deletion of or insertion of helix breaking residues into this region abolished the membrane binding, whereas a chimeric protein carrying just the amphipathic region fused with bacterial glutathione S -transferase failed to associate with the thylakoid membrane. The membrane-bound VP14 was partially resistant to chaotropic washes such as 0.1 m Na2CO3 (pH 11.5) and 6 m urea. Unlabelled recombinant VP14 inhibited the tight binding of imported VP14, suggesting that VP14 is associated with specific components of the thylakoid membrane. [source] The Institutional Trap in the Czech Rental Sector: Nested Circuits of Power, Space, and InequalityECONOMIC GEOGRAPHY, Issue 4 2005Stefan Buzar Abstract: An "institutional trap" is a sequence of misplaced regulatory steps that have increased the costs of institutional transformation to the level at which inefficient structures can remain stable, despite changes in the external economic environment. This is a common occurrence in Central and Eastern Europe because of the path-dependent nature of the postsocialist transformation process. This article examines the organizational and territorial transformations of housing, utility, and social welfare policies in the Czech Republic through a comparative analysis of institutional power geometries and household expenditures at the national scale. The results indicate that the Czech Republic is facing an institutional trap in the restructuring of its rent control and social welfare policies. The trap operates within three nested circuits: the power geometries of postsocialist reforms, the geographies of housing prices and social welfare, and the consumption patterns of disadvantaged households. The lock-in created by the trap can be resolved only through carefully targeted and synchronized social support and housing investment programs, parallel to rent liberalization. This article argues for comprehensive, rather than partial, solutions to the institutional trap and emphasizes the need for a deeper understanding of the relationships among institutions, space, and inequality. [source] N -methyl- d -aspartate receptor-mediated increase of neurogenesis in adult rat dentate gyrus following strokeEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2001Andreas Arvidsson Abstract Neurogenesis in the adult rat dentate gyrus was studied following focal ischemic insults produced by middle cerebral artery occlusion (MCAO). Animals were subjected to either 30 min of MCAO, which causes damage confined to the striatum, or 2 h of MCAO, which leads to both striatal and cortical infarction. When compared to sham-operated rats, MCAO-rats showed a marked increase of the number of cells double-labelled for 5-bromo-2,-deoxyuridine-5,-monophosphate (BrdU; injected during 4,6 days postischemia) and neuronal-specific antigen (NeuN; a marker of postmitotic neurons) in the ipsilateral dentate granule cell layer and subgranular zone at 5 weeks following the 2 h insult. Only a modest and variable increase of BrdU-labelled cells was found after 30 min of MCAO. The enhanced neurogenesis was not dependent on cell death in the hippocampus, and its magnitude was not correlated to the degree of cortical damage. Systemic administration of the N -methyl- d -aspartate (NMDA) receptor blocker dizocilpine maleate (MK-801) completely suppressed the elevated neurogenesis following 2 h of MCAO. Our findings indicate that stroke leads to increased neurogenesis in the adult rat dentate gyrus through glutamatergic mechanisms acting on NMDA receptors. This modulatory effect may be mediated through changes in the levels of several growth factors, which occur after stroke, and could influence various regulatory steps of neurogenesis. [source] p38 mitogen-activated protein kinase is required for central nervous system myelinationGLIA, Issue 15 2007Gabriela Fragoso Abstract The p38 MAPKs are a family of kinases that regulate a number of cellular functions including cell migration, proliferation, and differentiation. Here, we report that p38 regulates oligodendrocyte differentiation. Inhibition of p38 with PD169316 and SB203580 prevented accumulation of protein and mRNA of cell-stage specific markers characteristic of differentiated oligodendrocytes, including myelin basic protein, myelin-associated glycoprotein, and the glycosphingolipids, galactosylceramide and sulfatide. In addition, the cell cycle regulator p27kip1 and the transcription factor Sox10 were also significantly reduced. Most significantly, p38 inhibitors completely and irreversibly blocked myelination of dorsal root ganglion neurons by oligodendrocytes and prevented the axolemmal organization of the axo-glial adhesion molecule Caspr. Our results suggest a role(s) for this kinase in key regulatory steps in the maturation of OLGs and initiation of myelination. © 2007 Wiley-Liss, Inc. [source] Centrosome function in normal and tumor cellsJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2006Satish Sankaran Abstract Centrosomes nucleate microtubules that form the mitotic spindle and regulate the equal division of chromosomes during cell division. In cancer, centrosomes are often found amplified to greater than two per cell, and these tumor cells frequently have aneuploid genomes. In this review, we will discuss the cellular factors that regulate the proper duplication of the centrosome and how these regulatory steps can lead to abnormal centrosome numbers and abnormal mitoses. In particular, we highlight the newly emerging role of the Breast Cancer 1 (BRCA1) ubiquitin ligase in this process. J. Cell. Biochem. 99: 1240,1250, 2006. © 2006 Wiley-Liss, Inc. [source] Inhibition of Caspases In Vivo Protects the Rat Liver Against Alcohol-Induced Sensitization to Bacterial LipopolysaccharideALCOHOLISM, Issue 6 2001Ion V. Deaciuc Background: The mechanisms of liver sensitization by alcohol to Gram-negative bacterial lipopolysaccharide (LPS) remain elusive. The purpose of this study was two-fold: (1) to test the hypothesis that alcohol-enhanced liver apoptosis may be a sensitizing mechanism for LPS and (2) to further characterize the liver apoptotic response to alcohol. Methods: Rats were fed a high-fat, alcohol-containing liquid diet for 14 weeks, treated with LPS (1.0 mg/kg of body weight, intravenously) or saline, followed by injection of a pan-caspase inhibitor {IDN1965;N -[(1,3-dimethylindole-2-carbonyl)-valinyl]-3-amino-4-oxo-5-fluoropentanoic acid; 10 mg/kg of body weight, intraperitoneally} or vehicle, and killed. The following parameters were assessed: plasma aspartate: 2-oxoglutarate aminotransferase activity (AST); liver histology and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) response; caspase-3, ,8, and ,9 activity; and mRNA and protein expression for two apoptosis-signaling molecules: Fas receptor and Fas ligand; and three apoptosis adaptors: Bax, Bcl-XL, and Bcl-2. Results: Alcohol-feeding-induced liver steatosis, slightly increased caspases' activity, the number of TUNEL-positive nuclei, and facilitated the LPS necrotic effect without affecting mRNA expression of apoptosis signals and adaptors. LPS induced a significant increase in AST and the number of TUNEL-positive nuclei, both effects being more pronounced in alcohol-treated rats. LPS produced hepatic necrosis only in alcohol-treated rats. LPS effects were associated with up-regulation of mRNA expression for both apoptosis adaptors and signaling molecules. IDN1965 administration 3 hr after LPS injection strongly inhibited caspases' activity, particularly that of caspase-3. IDN1965 also abolished the increase in TUNEL-positive nuclei, reversed the effect of LPS on plasma AST in alcohol-treated rats, and prevented LPS-induced necrosis. Conclusions: (1) Alcohol-enhanced liver apoptosis may not involve regulatory steps at the transcriptional level. LPS-induced liver apoptosis seems to involve transcriptional regulation of several apoptosis adaptors. Therefore, alcohol and LPS may enhance liver apoptosis through different mechanisms. (2) Alcohol-enhanced liver apoptosis precedes and may facilitate the hepatic effects of LPS. LPS superimposed on alcohol further elevates the rate of apoptosis in the liver. This may exceed the phagocytosing capacity of the liver so that all the apoptotic cells are not phagocytosed, but rather die of necrosis. [source] |