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Dominant Negative I (dominant + negative_i)
Selected AbstractsIdentification of a novel nuclear factor-kappaB sequence involved in expression of urokinase-type plasminogen activator receptorFEBS JOURNAL, Issue 11 2000Yao Wang We have previously defined the promoter of human urokinase-type plasminogen activator receptor (uPAR) gene in a 188-bp fragment between bases ,141 and +47 relative to the translation start site. Here, we report that a novel nuclear factor-kappaB (NF-,B)-like sequence (5,-GGGAGGAGTC-3,) at ,45 is located in the uPAR promoter and one of the two DNase I-protected regions, region I between bases ,51 and ,30. This NF-,B-like motif differs at positions 7,9 from the decameric consensus sequences of NF-,B (5,-GGGRNNYYCC-3, where R indicates A or G, Y indicates C or T, and N indicates any nucleotide) and at positions 1 and 7,9 from the ,B-like motifs (5,-HGGARNYYCC-3, where H indicates A, C, or T, R indicates A or G, Y indicates C or T, and N indicates any nucleotide). Nuclear extracts from HCT116 cells contain proteins that specifically bind to the NF-,B-like site at position ,45. Mutation of the NF-,B-like motif decreased the binding of transcription factor NF-,B and reduced the uPAR promoter activity in comparison with the wild-type sequences. Co-transfection with a dominant negative I-,B kinase-2 expression vector reduced uPAR promoter activity by 65,75%. These results demonstrate that a previously uncharacterized NF-,B motif is required for uPAR promoter activity. [source] Nuclear factor-,B contributes to interleukin-4- and interferon-dependent polymeric immunoglobulin receptor expression in human intestinal epithelial cellsIMMUNOLOGY, Issue 1 2004Laynez W. Ackermann Summary Polymeric immunoglobulins (pIgs) that are present at mucosal surfaces play key roles in both the innate and adaptive immune responses. These pIgs are delivered to the mucosal surface via transcytosis across the epithelium, a process mediated by the polymeric immunoglobulin receptor (pIgR). Previous studies demonstrate that expression of the pIgR is regulated by multiple immunomodulatory factors including interleukin-4 (IL-4) and interferon-, (IFN-,). In studies using human intestinal epithelial cells (HT29), multiple inhibitors of the transcription factor nuclear factor-,B (NF-,B), including a dominant negative I,B,-serine mutant, inhibited both IL-4- and IFN-dependent increases in pIgR expression. Under identical conditions, NF-,B inhibitors had no effect on cytokine-dependent increases in expression of the transcription factor interferon regulatory factor-1. Over-expression of the I,B,-serine mutant also inhibited reporter gene expression in response to IL-4, TNF-,, IL-1,, and in some cases IFN-, using constructs with sequences from the pIgR promoter. Reduced levels of pIgR were observed even when inhibitors were added ,24 hr after cytokines suggesting that prolonged activation of NF-,B is required. Finally, reporter gene studies with NF-,B enhancer elements indicated that IFN-, alone and IL-4 in combination with other cytokines activated NF-,B in HT29 cells. Together, these studies provide additional insight into the signalling pathways that contribute to expression of the pIgR, a critical player in mucosal immunity. [source] Possible Involvement of I,B Kinase 2 and MKK7 in Osteoclastogenesis Induced by Receptor Activator of Nuclear Factor ,B Ligand,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2002Aiichiro Yamamoto Abstract Recent studies have revealed the essential role of the receptor activator of nuclear factor ,B (NF-,B) ligand (RANKL) in osteoclast differentiation and activation. Adenovirus vector could efficiently transduce genes into RAW264.7 cells, which differentiate into osteoclast-like multinucleated cells in the presence of RANKL. The role of NF-,B and c- jun N-terminal kinase (JNK) activation in RANKL-induced osteoclast differentiation was investigated using an adenovirus vector carrying the dominant negative I,B kinase 2 gene (AxIKK2DN) or dominant negative MKK7 gene (AxMKK7DN). IKK2DN and MKK7DN overexpression in RAW cells specifically suppressed the NF-,B activation and JNK activation in response to RANKL, respectively, without affecting other signaling pathways. Either inhibition of NF-,B or JNK pathways dose-dependently inhibited osteoclast formation induced by RANKL. These results suggest that both NF-,B and JNK activation are independently required for osteoclast differentiation. [source] Neuroprotection by stem cell factor in rat cortical neurons involves AKT and NF,BJOURNAL OF NEUROCHEMISTRY, Issue 1 2005Krishnan M. Dhandapani Abstract Stem cell factor (SCF) is a highly expressed cytokine in the central nervous system. In the present study, we demonstrate a neuroprotective role for SCF and its tyrosine kinase receptor, c-kit, against camptothecin-induced apoptosis and glutamate excitotoxicity in rat cortical neurons. This protection was blocked by pharmacological or molecular inhibition of either the MEK/ERK or PI3K/Akt signaling pathways. The importance of these pathways was further confirmed by the activation of both ERK, in a MEK-dependent manner, and Akt, via PI3K. Activation of Akt increased the binding of the p50 and p65 subunits of NF,B, which was also important for neuroprotection. Akt inhibition prevented NF,B binding, suggesting a role for Akt in SCF-induced NF,B. Pharmacological inhibition of NF,B or dominant negative I,B also prevented neuroprotection by SCF. SCF up-regulated the anti-apoptotic genes, bcl-2 and bcl-xL in an NF,B-dependent manner. Together, these findings demonstrate a neuroprotective role for SCF in cortical neurons, an effect that was mediated by Akt and ERK, as well as NF,B-mediated gene transcription. SCF represents a novel therapeutic target in the treatment of neurodegenerative disease. [source] Manganese potentiates nuclear factor-,B-dependent expression of nitric oxide synthase 2 in astrocytes by activating soluble guanylate cyclase and extracellular responsive kinase signaling pathwaysJOURNAL OF NEUROSCIENCE RESEARCH, Issue 9 2008Julie A. Moreno Abstract Inflammatory activation of glial cells is associated with neuronal injury in several degenerative movement disorders of the basal ganglia, including manganese neurotoxicity. Manganese (Mn) potentiates the effects of inflammatory cytokines on nuclear factor-,B (NF-,B)-dependent expression of nitric oxide synthase 2 (NOS2) in astrocytes, but the signaling mechanisms underlying this effect have remained elusive. It was postulated in the present studies that direct stimulation of cGMP synthesis and activation of mitogen-activated protein (MAP) kinase signaling pathways underlies the capacity of Mn to augment NF-,B-dependent gene expression in astrocytes. Exposure of primary cortical astrocytes to a low concentration of Mn (10 ,M) potentiated expression of NOS2 mRNA and protein along with production of NO in response to interferon-, (IFN,) and tumor necrosis factor-, (TNF,), which was prevented by overexpression of dominant negative I,B,. Mn also potentiated IFN,- and TNF,-induced phosphorylation of extracellular response kinase (ERK), p38, and JNK, as well as cytokine-induced activation of a fluorescent NF-,B reporter construct in transgenic astrocytes. Activation of ERK preceded that of NF-,B and was required for maximal activation of NO synthesis. Independently of IFN,/TNF,, Mn-stimulated synthesis of cGMP in astrocytes and inhibition of soluble guanylate cyclase (sGC) abolished the potentiating effect of Mn on MAP kinase phosphorylation, NF-,B activation, and production of NO. These data indicate that near-physiological concentrations of Mn potentiate cytokine-induced expression of NOS2 and production of NO in astrocytes via activation of sGC, which promotes ERK-dependent enhancement of NF-,B signaling. © 2008 Wiley-Liss, Inc. [source] | |||||||||||||