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991.
BACKGROUND: Tumor cells can move in a three-dimensional (3D) environment in either mesenchymal-type or amoeboid modes. In mesenchymal-type movement, cells have an elongated morphology with Rac-induced protrusions at the leading edge. Amoeboid cells have high levels of actomyosin contractility, and movement is associated with deformation of the cell body through the matrix without proteolysis. Because signaling pathways that control the activation of GTPases for amoeboid movement are poorly understood, we sought to identify regulators of amoeboid movement by screening an siRNA library targeting guanine nucleotide exchange factors (GEFs) for Rho-family GTPases. RESULTS: We identified DOCK10, a Cdc42 GEF, as a key player in amoeboid migration; accordingly, we find that expression of activated Cdc42 induces a mesenchymal-amoeboid transition and increases cell invasion. Silencing DOCK10 expression promotes conversion to mesenchymal migration and is associated with decreased MLC2 phosphorylation and increased Rac1 activation. Consequently, abrogating DOCK10 and Rac1 expression suppresses both amoeboid and mesenchymal migration and results in decreased invasion. We show that the Cdc42 effectors N-WASP and Pak2 are required for the maintenance of the rounded-amoeboid phenotype. Blocking Cdc42 results in loss of mesenchymal morphology, arguing that Cdc42 is also involved in mesenchymal morphology through different activation and effector pathways. CONCLUSIONS: Previous work has identified roles of Rho and Rac signaling in tumor cell movement, and we now elucidate novel roles of Cdc42 signaling in amoeboid and mesenchymal movement and tumor cell invasion. 相似文献
992.
Katy Vaillancourt Nathalie Bdard Christian Bart Mlanie Tessier Gilles Robitaille Nathalie Turgeon Michel Frenette Sylvain Moineau Christian Vadeboncoeur 《Applied microbiology》2008,74(4):1264-1267
Streptococcus thermophilus is unable to metabolize the galactose moiety of lactose. In this paper, we show that a transformant of S. thermophilus SMQ-301 expressing Streptococcus salivarius galK and galM was able to grow on galactose and expelled at least twofold less galactose into the medium during growth on lactose. 相似文献
993.
The many faces of aspartate kinases 总被引:1,自引:0,他引:1
Dumas R Cobessi D Robin AY Ferrer JL Curien G 《Archives of biochemistry and biophysics》2012,519(2):186-193
Based on recent X-ray structures and biochemical characterizations of aspartate kinases from different species, we show in this review how various organizations of a regulatory domain have contributed to the different mechanisms of control observed in aspartate kinases allowing simple to complex allosteric controls in branched pathways. The aim of this review is to show the relationships between domain organization, effector binding sites, mechanism of inhibition and regulatory function of an allosteric enzyme in a biosynthetic pathway. 相似文献
994.
M Culcasi L Benameur A Mercier C Lucchesi H Rahmouni A Asteian G Casano A Botta H Kovacic S Pietri 《Chemico-biological interactions》2012,199(3):161-176
To better understand the antioxidant (enzyme mimetic, free radical scavenger) versus oxidant and cytotoxic properties of the industrially used cerium oxide nanoparticles (nano-CeO(2)), we investigated their effects on reactive oxygen species formation and changes in the antioxidant pool of human dermal and murine 3T3 fibroblasts at doses relevant to chronic inhalation or contact with skin. Electron paramagnetic resonance (EPR) spin trapping with the nitrone DEPMPO showed that pretreatment of the cells with the nanoparticles dose-dependently triggered the release in the culture medium of superoxide dismutase- and catalase-inhibitable DEPMPO/hydroxyl radical adducts (DEPMPO-OH) and ascorbyl radical, a marker of ascorbate depletion. This DEPMPO-OH formation occurred 2 to 24h following removal of the particles from the medium and paralleled with an increase of cell lipid peroxidation. These effects of internalized nano-CeO(2) on spin adduct formation were then investigated at the cellular level by using specific NADPH oxidase inhibitors, transfection techniques and a mitochondria-targeted antioxidant. When micromolar doses of nano-CeO(2) were used, weak DEPMPO-OH levels but no loss of cell viability were observed, suggesting that cell signaling mechanisms through protein synthesis and membrane NADPH oxidase activation occurred. Incubation of the cells with higher millimolar doses provoked a 25-60-fold higher DEPMPO-OH formation together with a decrease in cell viability, early apoptosis induction and antioxidant depletion. These cytotoxic effects could be due to activation of both the mitochondrial source and Nox2 and Nox4 dependent NADPH oxidase complex. Regarding possible mechanisms of nano-CeO(2)-induced free radical formation in cells, in vitro EPR and spectrophotometric studies suggest that, contrary to Fe(2+) ions, the Ce(3+) redox state at the surface of the particles is probably not an efficient catalyst of hydroxyl radical formation by a Fenton-like reaction in vivo. 相似文献
995.
Binet V Duthey B Lecaillon J Vol C Quoyer J Labesse G Pin JP Prézeau L 《The Journal of biological chemistry》2007,282(16):12154-12163
G protein-coupled receptors (GPCRs) are key players in cell communication. Several classes of such receptors have been identified. Although all GPCRs possess a heptahelical domain directly activating G proteins, important structural and sequence differences within receptors from different classes suggested distinct activation mechanisms. Here we show that highly conserved charged residues likely involved in an interaction network between transmembrane domains (TM) 3 and 6 at the cytoplasmic side of class C GPCRs are critical for activation of the gamma-aminobutyric acid type B receptor. Indeed, the loss of function resulting from the mutation of the conserved lysine residue into aspartate or glutamate in the TM3 of gamma-aminobutyric acid type B(2) can be partly rescued by mutating the conserved acidic residue of TM6 into either lysine or arginine. In addition, mutation of the conserved lysine into an acidic residue leads to a nonfunctional receptor that displays a high agonist affinity. This is reminiscent of a similar ionic network that constitutes a lock stabilizing the inactive state of many class A rhodopsin-like GPCRs. These data reveal that despite their original structure, class C GPCRs share with class A receptors at least some common structural feature controlling G protein activation. 相似文献
996.
997.
Juan Manuel Chao de la Barca Nuan-Ting Huang Haihan Jiao Lydie Tessier Cédric Gadras Gilles Simard Riccardo Natoli Guillaume Tcherkez Pascal Reynier Krisztina Valter 《Metabolomics : Official journal of the Metabolomic Society》2017,13(3):22
Introduction
Light is the primary stimulus for vision, but may also cause damage to the retina. Pre-exposing the retina to sub-lethal amount of light (or preconditioning) improves chances for retinal cells to survive acute damaging light stress.Objectives
This study aims at exploring the changes in retinal metabolome after mild light stress and identifying mechanisms that may be involved in preconditioning.Methods
Retinas from 12 rats exposed to mild light stress (1000 lux?×?for 12 h) and 12 controls were collected one and seven days after light stress (LS). One retina was used for targeted metabolomics analysis using the Biocrates p180 kit while the fellow retina was used for histological and immunohistochemistry analysis.Results
Immunohistochemistry confirmed that in this experiment, a mild LS with retinal immune response and minimal photoreceptor loss occurred. Compared to controls, LS induced an increased concentration in phosphatidylcholines. The concentration in some amino acids and biogenic amines, particularly those related to the nitric oxide pathway (like asymmetric dimethylarginine (ADMA), arginine and citrulline) also increased 1 day after LS. 7 days after LS, the concentration in two sphingomyelins and phenylethylamine was found to be higher. We further found that in controls, retina metabolome was different between males and females: male retinas had an increased concentration in tyrosine, acetyl-ornithine, phosphatidylcholines and (acyl)-carnitines.Conclusions
Besides retinal sexual metabolic dimorphism, this study shows that preconditioning is mostly associated with re-organisation of lipid metabolism and changes in amino acid composition, likely reflecting the involvement of arginine-dependent NO signalling.998.
Yuka Torii Yoshihiko Kawano Hajime Sato Tamaki Fujimori Kazunori Sasaki Jun-ichi Kawada Osamu Takikawa Chai K. Lim Gilles J. Guillemin Yoshiaki Ohashi Yoshinori Ito 《Metabolomics : Official journal of the Metabolomic Society》2017,13(11):126
Introduction
Human herpesvirus 6 (HHV-6) is the second most common causative pathogen of acute encephalopathy in immunocompetent children in Japan. Identification of biomarkers associated the pathophysiology is desirable to monitor disease severity, progression, and prognosis.Objectives
To investigate potential biomarkers for HHV-6 encephalopathy, serum metabolome profiling was analyzed and candidate metabolites were investigated the function in the diseases.Methods
Pediatric patients with HHV-6 encephalopathy (n?=?8), febrile seizure (n?=?20), and febrile infection without febrile seizure (n?=?7) were enrolled in this study, and serum metabolites were identified and quantified. For further analysis, serum samples of HHV-6 infected patients were analyzed by absolute quantification assay for kynurenine (KYN) and quinolinic acid (QUIN) in a total of 38 patients with or without encephalopathy. An in vitro blood–brain barrier (BBB) model was used to evaluate the effect of KYN and QUIN on BBB integrity because BBB damage induces brain edema.Results
Metabolome profiling identified 159 metabolites in serum samples. The levels of KYN and QUIN, which belong to the tryptophan-KYN pathway, were significantly higher in the HHV-6 encephalopathy group than the other two groups. When quantified in the larger patient group, remarkably high levels of KYN and QUIN were observed exclusively in the encephalopathy group. Trans-endothelial electrical resistance of the BBB model was significantly decreased after QUIN treatment in culture.Conclusion
Metabolome analysis revealed that KYN and QUIN may be associated with the pathophysiology of HHV-6 encephalopathy. In particular, QUIN may damage BBB integrity.999.
Cell wall peptidolipids of Mycobacterium avium: from genetic prediction to exact structure of a nonribosomal peptide 下载免费PDF全文
John P. Bannantine Gilles Etienne Françoise Laval Judith R. Stabel Anne Lemassu Mamadou Daffé Darrell O. Bayles Christelle Ganneau Frédéric Bonhomme Maxime Branger Thierry Cochard Sylvie Bay Franck Biet 《Molecular microbiology》2017,105(4):525-539
Mycobacteria have a complex cell wall structure that includes many lipids; however, even within a single subspecies of Mycobacterium avium these lipids can differ. Total lipids from an M. avium subsp. paratuberculosis (Map) ovine strain (S‐type) contained no identifiable glycopeptidolipids or lipopentapeptide (L5P), yet both lipids are present in other M. avium subspecies. We determined the genetic and phenotypic basis for this difference using sequence analysis as well as biochemical and physico‐chemical approaches. This strategy showed that a nonribosomal peptide synthase, encoded by mps1, contains three amino acid specifying modules in ovine strains, compared to five modules in bovine strains (C‐type). Sequence analysis predicted these modules would produce the tripeptide Phe‐N‐Methyl‐Val‐Ala with a lipid moiety, termed lipotripeptide (L3P). Comprehensive physico‐chemical analysis of Map S397 extracts confirmed the structural formula of the native L3P as D‐Phe‐N‐Methyl‐L‐Val‐L‐Ala‐OMe attached in N‐ter to a 20‐carbon fatty acid chain. These data demonstrate that S‐type strains, which are more adapted in sheep, produce a unique lipid. There is a dose‐dependent effect observed for L3P on upregulation of CD25+ CD8 T cells from infected cows, while L5P effects were static. In contrast, L5P demonstrated a significantly stronger induction of CD25+ B cells from infected animals compared to L3P. 相似文献
1000.
A novel lignin in poplar trees with a reduced caffeic acid/5-hydroxyferulic acid O-methyltransferase activity 总被引:9,自引:1,他引:9
Jan Van Doorsselaere Marie Baucher Emmanuelle Chognot Brigitte Chabbert Marie-Thérèse Tollier Michel Petit-Conil Jean-Charles Leplé Gilles Pilate Daniel Cornu Bernard Monties Marc Van Montagu Dirk Inzé Wout Boerjan Lise Jouanin 《The Plant journal : for cell and molecular biology》1995,8(6):855-864
Lignin is a polymeric constituent of the cell wall that needs to be removed during the paper making process. Bi-specific caffeic acid/5-hydroxyferulic acid O-methyltransferase (COMT) catalyses the O-methylation of caffeic acid and 5-hydroxyferulic acid to ferulic acid and sinapic acid, respectively. These compounds are intermediates in the biosynthesis of the lignin precursors. Therefore, COMTs are potential target enzymes for reducing the amount, or modifying the composition, of lignin in plants. Different antisense and sense constructs have been expressed of a gene encoding a COMT from poplar (Populus trichocarpa x P. deltoides) in a P. tremula x P. alba clone under the control of the cauliflower mosaic virus 35S promoter. From all analysed transformants, four lines transformed with an antisense construct had a reduced COMT activity. Two showed a 50% reduction of COMT activity, which altered only slightly the monomeric composition. In the two other transformants, the COMT activity was reduced by 95%. In the latter case, the syringyl/ guaiacyl ratio (S/G) was reduced by sixfold (due to a decrease of S and an increase of G), as analysed by thioacidolysis. A new component of lignin, the 5-hydroxyguaiacyl residue, was detected among the thioacidolysis products. Moreover, in contrast to the white/yellow colour of wild-type wood, the xylem of the transgenic lines with a 95% reduction of COMT activity was pale rose. A similar phenotype was observed in brown-midrib mutants of maize and sorghum, known for their altered lignification. Although the lignin composition was consistently modified, the lignin content of the transgenic poplars was similar to that of the controls. 相似文献