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Dependent Activation (dependent + activation)
Selected AbstractsEffects of Alcohol on Performance on a Distraction Task During Simulated DrivingALCOHOLISM, Issue 4 2009Allyssa J. Allen Background:, Prior studies report that accidents involving intoxicated drivers are more likely to occur during performance of secondary tasks. We studied this phenomenon, using a dual-task paradigm, involving performance of a visual oddball (VO) task while driving in an alcohol challenge paradigm. Previous functional MRI (fMRI) studies of the VO task have shown activation in the anterior cingulate, hippocampus, and prefrontal cortex. Thus, we predicted dose-dependent decreases in activation of these areas during VO performance. Methods:, Forty healthy social drinkers were administered 3 different doses of alcohol, individually tailored to their gender and weight. Participants performed a VO task while operating a virtual reality driving simulator in a 3T fMRI scanner. Results:, Analysis showed a dose-dependent linear decrease in Blood Oxygen Level Dependent activation during task performance, primarily in hippocampus, anterior cingulate, and dorsolateral prefrontal areas, with the least activation occurring during the high dose. Behavioral analysis showed a dose-dependent linear increase in reaction time, with no effects associated with either correct hits or false alarms. In all dose conditions, driving speed decreased significantly after a VO stimulus. However, at the high dose this decrease was significantly less. Passenger-side line crossings significantly increased at the high dose. Conclusions:, These results suggest that driving impairment during secondary task performance may be associated with alcohol-related effects on the above brain regions, which are involved with attentional processing/decision-making. Drivers with high blood alcohol concentrations may be less able to orient or detect novel or sudden stimuli during driving. [source] Rho plays a central role in regulating local cell-matrix mechanical interactions in 3D cultureCYTOSKELETON, Issue 6 2007N. Lakshman Abstract The purpose of this study was to assess quantitatively the role of the small GTPase Rho on cell morphology, f-actin organization, and cell-induced matrix remodeling in 3D culture. Human corneal fibroblasts (HTK) were infected with adenoviruses that express green fluorescent protein (GFP) or GFP-N19Rho (dominant negative Rho). One day later cells were plated inside collagen matrices and allowed to spread for 24 h. Cells were fixed and stained for f-actin. Fluorescent (for f-actin) and reflected light (for collagen fibrils) images were acquired using confocal microscopy. Fourier transform analysis was used to assess local collagen fibril alignment, and changes in cell morphology and collagen density were measured using MetaMorph. The decrease in matrix height was used as an indicator of global matrix contraction. HTK and HTK-GFP cells induced significant global matrix contraction; this was inhibited by N19Rho. HTK and HTK-GFP fibroblasts generally had a bipolar morphology and occasional intracellular stress fibers. Collagen fibrils were compacted and aligned parallel to stress fibers and pseudopodia. In contrast, HTK-GFPN19 cells were elongated, and had a more cortical f-actin distribution. Numerous small extensions were also observed along the cell body. In addition, both local collagen fibril density and alignment were significantly reduced. Rho plays a key role in regulating both the morphology and mechanical behavior of corneal fibroblasts in 3D culture. Overall, the data suggest that Rho-kinase dependent cell contractility contributes to global and local matrix remodeling, whereas Rho dependent activation of mDia and/or other downstream effectors regulates the structure and number of cell processes. Cell Motil. Cytoskeleton 2007. © 2007 Wiley-Liss, Inc. [source] Identification of ERR, as a specific partner of PGC-1, for the activation of PDK4 gene expression in muscleFEBS JOURNAL, Issue 8 2006Makoto Araki Pyruvate dehydrogenase kinase 4 (PDK4) is a key regulatory enzyme involved in switching the energy source from glucose to fatty acids in response to physiological conditions. Transcription of the PDK4 gene is activated by fasting or by the administration of a PPAR, ligand in a tissue-specific manner. Here, we show that the two mechanisms are independent, and that ERR, is directly involved in PPAR,-independent transcriptional activation of the PDK4 gene with PGC-1, as a specific partner. This conclusion is based on the following evidence. First, detailed mutation analyses of the cloned PDK4 gene promoter sequence identified a possible ERR,-binding motif as the PGC-1, responsive element. Second, overexpression of ERR, by cotransfection enhanced, and the knockout of it by shRNAs diminished, PGC-1,-dependent activation. Third, specific binding of ERR, to the identified PGC-1, responsive sequence was confirmed by the electrophoresis mobility shift assay. Finally, cell-type-specific responsiveness to PGC-1, was observed and this could be explained by differences in the expression levels of ERR,, however, ectopic expression of ERR, in poorly responsive cells did not restore PGC-1, responsiveness, indicating that ERR, is necessary, but not sufficient for the response. [source] Comparative studies on the functional roles of N- and C-terminal regions of molluskan and vertebrate troponin-IFEBS JOURNAL, Issue 17 2005Hiroyuki Tanaka Vertebrate troponin regulates muscle contraction through alternative binding of the C-terminal region of the inhibitory subunit, troponin-I (TnI), to actin or troponin-C (TnC) in a Ca2+ -dependent manner. To elucidate the molecular mechanisms of this regulation by molluskan troponin, we compared the functional properties of the recombinant fragments of Akazara scallop TnI and rabbit fast skeletal TnI. The C-terminal fragment of Akazara scallop TnI (ATnI232,292), which contains the inhibitory region (residues 104,115 of rabbit TnI) and the regulatory TnC-binding site (residues 116,131), bound actin-tropomyosin and inhibited actomyosin-tropomyosin Mg-ATPase. However, it did not interact with TnC, even in the presence of Ca2+. These results indicated that the mechanism involved in the alternative binding of this region was not observed in molluskan troponin. On the other hand, ATnI130,252, which contains the structural TnC-binding site (residues 1,30 of rabbit TnI) and the inhibitory region, bound strongly to both actin and TnC. Moreover, the ternary complex consisting of this fragment, troponin-T, and TnC activated the ATPase in a Ca2+ -dependent manner almost as effectively as intact Akazara scallop troponin. Therefore, Akazara scallop troponin regulates the contraction through the activating mechanisms that involve the region spanning from the structural TnC-binding site to the inhibitory region of TnI. Together with the observation that corresponding rabbit TnI-fragment (RTnI1,116) shows similar activating effects, these findings suggest the importance of the TnI N-terminal region not only for maintaining the structural integrity of troponin complex but also for Ca2+ -dependent activation. [source] Molecular cloning of the Matrix Gla Protein gene from Xenopus laevisFEBS JOURNAL, Issue 7 2002Functional analysis of the promoter identifies a calcium sensitive region required for basal activity To analyze the regulation of Matrix Gla Protein (MGP) gene expression in Xenopus laevis, we cloned the xMGP gene and its 5, region, determined their molecular organization, and characterized the transcriptional properties of the core promoter. The Xenopus MGP (xMGP) gene is organized into five exons, one more as its mammalian counterparts. The first two exons in the Xenopus gene encode the DNA sequence that corresponds to the first exon in mammals whereas the last three exons show homologous organization in the Xenopus MGP gene and in the mammalian orthologs. We characterized the transcriptional regulation of the xMGP gene in transient transfections using Xenopus A6 cells. In our assay system the identified promoter was shown to be transcriptionally active, resulting in a 12-fold induction of reporter gene expression. Deletional analysis of the 5, end of the xMGP promoter revealed a minimal activating element in the sequence from ,70 to ,36 bp. Synthetic reporter constructs containing three copies of the defined regulatory element delivered 400-fold superactivation, demonstrating its potential for the recruitment of transcriptional activators. In gel mobility shift assays we demonstrate binding of X. laevis nuclear factors to an extended regulatory element from ,180 to ,36, the specificity of the interaction was proven in competition experiments using different fragments of the xMGP promoter. By this approach the major site of factor binding was demonstrated to be included in the minimal activating promoter fragment from ,70 to ,36 bp. In addition, in transient transfection experiments we could show that this element mediates calcium dependent transcription and increasing concentrations of extracellular calcium lead to a significant dose dependent activation of reporter gene expression. [source] Stimulatory Effect of Insulin-Like Growth Factor Binding Protein-5 on Mouse Osteoclast Formation and Osteoclastic Bone-Resorbing ActivityJOURNAL OF BONE AND MINERAL RESEARCH, Issue 5 2000Masanori Kanatani Abstract Insulin-like growth factor binding protein-5 (IGFBP-5) stimulates osteoblast proliferation directly or indirectly through IGF-I action, but its effects on osteoclast formation and osteoclastic activity are unknown. We tested the effects of IGFBP-5 on osteoclastic activity and osteoclast formation. IGFBP-5 significantly stimulated pit formation by pre-existent osteoclasts in mouse bone cell cultures and its stimulatory effect was completely blocked by IGF-I antibody (Ab). However, IGFBP-5 did not affect the bone-resorbing activity of isolated rabbit osteoclasts. When IGFBP-5 was added to unfractionated bone cells after degeneration of pre-existent osteoclasts, IGFBP-5 (77 pM,7.7 nM) dose-dependently stimulated osteoclast-like cell formation, irrespective of the presence of IGF-I Ab. Moreover, osteoclast-like cells newly formed by IGFBP-5 from unfractionated bone cells possessed the ability to form pits on dentine slices. We next examined the direct effect of IGFBP-5 on osteoclast precursors in the absence of stromal cells, using hemopoietic blast cells derived from spleen cells. IGFBP-5 dose-dependently stimulated osteoclast-like cell formation from osteoclast precursors, irrespective of the presence of IGF-I Ab. Growth hormone (GH) as well as IGF-I significantly stimulated bone resorption by pre-existent osteoclasts in mouse bone cell cultures and these stimulatory effects were completely blocked by IGF-I Ab. GH as well as IGF-I stimulated osteoclast-like cell formation from unfractionated bone cells and this stimulatory effect of GH was significantly but partially blocked by IGF-I Ab. The direct stimulatory effect of GH on osteoclast-like cell formation from hemopoietic blast cells was not affected by IGF-I Ab. The present data indicate that IGFBP-5 stimulates bone resorption both by stimulation of osteoclast formation in an IGF-I,independent fashion and by IGF-I,dependent activation of mature osteoclasts, possibly via osteoblasts, in vitro. (J Bone Miner Res 2000;15:902,910) [source] Two modes of ERK activation by TNF in keratinocytes: Different cellular outcomes and bi-directional modulation by vitamin D,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2008Ester Ziv Abstract Inflammation, elicited in the skin following tissue damage or pathogen invasion, may become chronic with deleterious consequences. Tumor necrosis factor (TNF) is a key mediator of cutaneous inflammation and the keratinocyte an important protagonist of skin immunity. Calcitriol, the hormonally active vitamin D metabolite, and its analogs attenuate epidermal inflammation and inhibit the hyperproliferation of keratinocytes associated with the inflammatory disorder, psoriasis. Since activation of extracellular signal-regulated kinase (ERK) promotes keratinocyte proliferation and mediates epidermal inflammation, we studied the effect of calcitriol on ERK activation in HaCaT keratinocytes exposed to the ubiquitous inflammatory cytokine TNF. By using the EGF receptor (EGFR) tyrosine kinase inhibitor, AG1487 and the Src family inhibitor, PP-1, we established that TNF activated ERK in an EGFR and Src dependent and an EGFR and Src independent modes. EGFR dependent activation resulted in the upregulation of the transcription factor, c-Fos, while the EGFR independent activation mode was of a shorter duration, did not affect c-Fos expression but induced IL-8 mRNA expression. Pretreatment with calcitriol, enhanced TNF-induced EGFR-Src dependent ERK activation and tyrosine phosphorylation of the EGFR, but abolished the EGFR-Src independent ERK activation. These effects were mirrored by enhancement of c-Fos and inhibition of IL-8 induction by TNF. Treatment with calcitriol increased the rate of the de-phosphorylation of activated ERK, accounting for the inhibition of EGFR-Src independent ERK activation by TNF. It is possible that effects on the ERK cascade contribute to the effects of calcitriol and its synthetic analogs on cutaneous inflammation and keratinocyte proliferation. J. Cell. Biochem. 104: 606,619, 2008. © 2007 Wiley-Liss, Inc. [source] Condition-adapted stress and longevity gene regulation by Caenorhabditis elegans SKN-1/NrfAGING CELL, Issue 5 2009Riva P. Oliveira Summary Studies in model organisms have identified regulatory processes that profoundly influence aging, many of which modulate resistance against environmental or metabolic stresses. In Caenorhabditis elegans, the transcription regulator SKN-1 is important for oxidative stress resistance and acts in multiple longevity pathways. SKN-1 is the ortholog of mammalian Nrf proteins, which induce Phase 2 detoxification genes in response to stress. Phase 2 enzymes defend against oxygen radicals and conjugate electrophiles that are produced by Phase 1 detoxification enzymes, which metabolize lipophilic compounds. Here, we have used expression profiling to identify genes and processes that are regulated by SKN-1 under normal and stress,response conditions. Under nonstressed conditions SKN-1 upregulates numerous genes involved in detoxification, cellular repair, and other functions, and downregulates a set of genes that reduce stress resistance and lifespan. Many of these genes appear to be direct SKN-1 targets, based upon presence of predicted SKN-binding sites in their promoters. The metalloid sodium arsenite induces skn-1- dependent activation of certain detoxification gene groups, including some that were not SKN-1-upregulated under normal conditions. An organic peroxide also triggers induction of a discrete Phase 2 gene set, but additionally stimulates a broad SKN-1-independent response. We conclude that under normal conditions SKN-1 has a wide range of functions in detoxification and other processes, including modulating mechanisms that reduce lifespan. In response to stress, SKN-1 and other regulators tailor transcription programs to meet the challenge at hand. Our findings reveal striking complexity in SKN-1 functions and the regulation of systemic detoxification defenses. [source] Modulation of calcium entry and glutamate release in cultured cerebellar granule cells by palytoxinJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2006Carmen Vale Abstract A channel open on the membrane can be formed by palytoxin (PTX). Ten nanomolar PTX caused an irreversible increase in the cytosolic calcium concentration ([Ca2+]c), which was abolished in the absence of external calcium. The increase was eliminated by saxitoxin (STX) and nifedipine (NIF). Calcium rise is secondary to the membrane depolarization. PTX effect on calcium was dependent on extracellular Na+. Li+ decreased the PTX-evoked rise in [Ca2+]c; replacement of Na+ by N-methyl-D-glucamine (NMDG) abolished PTX-induced calcium increase. [Ca2+]c increase by PTX was strongly reduced after inhibition of the reverse operation of the Na+/Ca2+ exchanger, in the presence of antagonists of excitatory amino acid (EAA) receptors, and by inhibition of neurotransmitter release. PTX did not modify calcium extrusion by the plasma membrane Ca2+ -ATPase (PMCA), because blockade of the calcium pump increased rather than decreased the PTX-induced calcium influx. Extracellular levels of glutamate and aspartate were measured by HPLC and exocytotic neurotransmitter release by determination of synaptic vesicle exocytosis using total internal reflection fluorescence microscopy (TIRFM). PTX caused a concentration-dependent increase in EAA release to the culture medium. Ten nanomolar PTX decreased cell viability by 30% within 5 min. PTX-induced calcium influx involves three pathways: Na+ -dependent activation of voltage-dependent sodium channels (VDSC) and voltage-dependent calcium channels (VDCC), reverse operation of the Na+/Ca2+ exchanger, and indirect activation of EAA receptors through glutamate release. The neuronal injury produced by the toxin could be partially mediated by the PTX-induced overactivation of EAA receptors, VDSC, VDCC and the glutamate efflux into the extracellular space. © 2006 Wiley-Liss, Inc. [source] Divergent regulation of GIRK1 and GIRK2 subunits of the neuronal G protein gated K+ channel by G,iGDP and G,,THE JOURNAL OF PHYSIOLOGY, Issue 14 2009Moran Rubinstein G protein activated K+ channels (GIRK, Kir3) are switched on by direct binding of G,, following activation of Gi/o proteins via G protein-coupled receptors (GPCRs). Although G,i subunits do not activate GIRKs, they interact with the channels and regulate the gating pattern of the neuronal heterotetrameric GIRK1/2 channel (composed of GIRK1 and GIRK2 subunits) expressed in Xenopus oocytes. Coexpressed G,i3 decreases the basal activity (Ibasal) and increases the extent of activation by purified or coexpressed G,,. Here we show that this regulation is exerted by the ,inactive' GDP-bound G,i3GDP and involves the formation of G,i3,, heterotrimers, by a mechanism distinct from mere sequestration of G,,,away' from the channel. The regulation of basal and G,,-evoked current was produced by the ,constitutively inactive' mutant of G,i3, G,i3G203A, which strongly binds G,,, but not by the ,constitutively active' mutant, G,i3Q204L, or by G,,-scavenging proteins. Furthermore, regulation by G,i3G203A was unique to the GIRK1 subunit; it was not observed in homomeric GIRK2 channels. In vitro protein interaction experiments showed that purified G,, enhanced the binding of G,i3GDP to the cytosolic domain of GIRK1, but not GIRK2. Homomeric GIRK2 channels behaved as a ,classical' G,, effector, showing low Ibasal and strong G,,-dependent activation. Expression of G,i3G203A did not affect either Ibasal or G,,-induced activation. In contrast, homomeric GIRK1* (a pore mutant able to form functional homomeric channels) exhibited large Ibasal and was poorly activated by G,,. Expression of G,i3GDP reduced Ibasal and restored the ability of G,, to activate GIRK1*, like in GIRK1/2. Transferring the unique distal segment of the C terminus of GIRK1 to GIRK2 rendered the latter functionally similar to GIRK1*. These results demonstrate that GIRK1 containing channels are regulated by both G,i3GDP and G,,, while GIRK2 is a G,,-effector insensitive to G,i3GDP. [source] Interferon-,,dependent inhibition of B cell activation by bone marrow,derived mesenchymal stem cells in a murine model of systemic lupus erythematosusARTHRITIS & RHEUMATISM, Issue 9 2010Francesca Schena Objective Bone marrow,derived mesenchymal stem cells (BM-MSCs) are multipotent cells characterized by immunomodulatory properties and are therefore considered a promising tool for the treatment of immune-mediated diseases. This study was undertaken to assess the influence of murine BM-MSCs on the activation of B cells in (NZB × NZW)F1 mice as an animal model of systemic lupus erythematosus (SLE). Methods We evaluated the in vitro effects of BM-MSCs on the proliferation and differentiation to plasma cells of splenic mature B cell subsets, namely follicular and marginal zone B cells isolated from (NZB × NZW)F1 mice. Lupus mice were also treated with BM-MSCs, and serum autoantibodies, proteinuria, histologic changes in the kidney, and survival rates were monitored. Results BM-MSCs inhibited antigen-dependent proliferation and differentiation to plasma cells of follicular and marginal zone B cells in vitro. This inhibitory effect was dependent on interferon-, (IFN,) and was mediated by cell-to-cell contact, involving the programmed death 1 (PD-1)/PD ligand pathway. In vivo treatment with BM-MSCs did not affect the levels of anti,double-stranded DNA antibodies or proteinuria. However, a reduction in glomerular immune complex deposition, lymphocytic infiltration, and glomerular proliferation was observed. Conclusion Our findings indicate that BM-MSCs affect B cell receptor,dependent activation of both follicular and marginal zone B cells from lupus mice. This inhibitory effect is IFN,-dependent and cell contact,dependent. MSCs in vivo do not affect the production of autoantibodies, the level of proteinuria, or the mortality rates. Nonetheless, the significant improvement in histologic findings in the kidney supports the potential role of MSCs in the prevention of glomerular damage. [source] Rho kinase,dependent activation of SOX9 in chondrocytesARTHRITIS & RHEUMATISM, Issue 1 2010Dominik R. Haudenschild Objective The transcription factor SOX9 directly regulates the expression of the major proteoglycans and collagens comprising the cartilage extracellular matrix. The DNA binding activity and cellular localization of SOX9 is controlled through posttranslational modifications, including phosphorylation. The activity of Rho kinase (ROCK) has profound effects on the actin cytoskeleton, and these effects are instrumental in determining the phenotype and differentiation of chondrocytes. However, the mechanisms linking ROCK to altered chondrocyte gene expression remain unknown. The purpose of the present study was to test for a direct interaction between ROCK and SOX9. Methods Human SW1353 chondrosarcoma cells were transfected with constructs coding for RhoA, ROCK, Lim kinase, and SOX9. The interaction between ROCK and SOX9 was tested on purified proteins, and was verified within a cellular context using induced overexpression and activation of the Rho pathway. The effects of SOX9 transcriptional activation were quantified with a luciferase reporter plasmid containing SOX9 binding sites from the COL2A1 enhancer element. Results SOX9 was found to contain a consensus phosphorylation site for ROCK. In vitro, ROCK directly phosphorylated SOX9 at Ser181, and the overexpression of ROCK or the activation of the RhoA pathway in SW1353 chondrosarcoma cells increased SOX9Ser181 phosphorylation. ROCK caused a dose-dependent increase in the transcription of a SOX9-luciferase reporter construct, and increased phosphorylation and nuclear accumulation of SOX9 protein in response to transforming growth factor , treatment and mechanical compression. Conclusion These results demonstrate a new interaction that directly links ROCK to increased cartilage matrix production via activation of SOX9 in response to mechanical and growth factor stimulation. [source] Intermolecular cross-talk between the prostaglandin E2 receptor (EP)3 subtype and thromboxane A2 receptor signalling in human erythroleukaemic cellsBRITISH JOURNAL OF PHARMACOLOGY, Issue 3 2009Helen M Reid Background and purpose:, In previous studies investigating cross-talk of signalling between prostaglandin (PG)E2 receptor (EP) and the TP, and TP, isoforms of the human thromboxane (TX)A2 receptor (TP), 17-phenyl trinor PGE2 -induced desensitization of TP receptor signalling through activation of the AH6809 and SC19220-sensitive EP1 subtype of the EP receptor family, in a cell-specific manner. Here, we sought to further investigate that cross-talk in human erythroleukaemic (HEL) 92.1.7 cells. Experimental approach:, Specificity of 17-phenyl trinor PGE2 signalling and its possible cross-talk with signalling by TP,/TP, receptors endogenously expressed in HEL cells was examined through assessment of agonist-induced inositol 1,4,5-trisphosphate (IP)3 generation and intracellular calcium ([Ca2+]i) mobilization. Key results:, While 17-Phenyl trinor PGE2 led to activation of phospholipase (PL)C, to yield increases in IP3 generation and [Ca2+]i, it did not desensitize but rather augmented that signalling in response to subsequent stimulation with the TXA2 mimetic U46619. Furthermore, the augmentation was reciprocal. Signalling by 17-phenyl trinor PGE2 was found to occur through AH6809- and SC19920-insensitive, Pertussis toxin-sensitive, Gi/G,, -dependent activation of PLC,. Further pharmacological investigation using selective EP receptor subtype agonists and antagonists confirmed that 17-phenyl trinor PGE2 -mediated signalling and reciprocal cross-talk with the TP receptors occurred through the EP3, rather than the EP1, EP2 or EP4 receptor subtype in HEL cells. Conclusions and Implications:, The EP1 and EP3 subtypes of the EP receptor family mediated intermolecular cross-talk to differentially regulate TP receptor-mediated signalling whereby activation of EP1 receptors impaired or desensitized, while that of EP3 receptors augmented signalling through TP,/TP, receptors, in a cell type-specific manner. [source] | |||||||||||||