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91.
92.
Pierce KL Tohgo A Ahn S Field ME Luttrell LM Lefkowitz RJ 《The Journal of biological chemistry》2001,276(25):23155-23160
"Transactivation" of epidermal growth factor receptors (EGFRs) in response to activation of many G protein-coupled receptors (GPCRs) involves autocrine/paracrine shedding of heparin-binding EGF (HB-EGF). HB-EGF shedding involves proteolytic cleavage of a membrane-anchored precursor by incompletely characterized matrix metalloproteases. In COS-7 cells, alpha(2A)-adrenergic receptors (ARs) stimulate ERK phosphorylation via two distinct pathways, a transactivation pathway that involves the release of HB-EGF and the EGFR and an alternate pathway that is independent of both HB-EGF and the EGFR. We have developed a mixed culture system to study the mechanism of GPCR-mediated HB-EGF shedding in COS-7 cells. In this system, alpha(2A)AR expressing "donor" cells are co-cultured with "acceptor" cells lacking the alpha(2A)AR. Each population expresses a uniquely epitope-tagged ERK2 protein, allowing the selective measurement of ERK activation in the donor and acceptor cells. Stimulation with the alpha(2)AR selective agonist UK14304 rapidly increases ERK2 phosphorylation in both the donor and the acceptor cells. The acceptor cell response is sensitive to inhibitors of both the EGFR and HB-EGF, indicating that it results from the release of HB-EGF from the alpha(2A)AR-expressing donor cells. Experiments with various chemical inhibitors and dominant inhibitory mutants demonstrate that EGFR-dependent activation of the ERK cascade after alpha(2A)AR stimulation requires Gbetagamma subunits upstream and dynamin-dependent endocytosis downstream of HB-EGF shedding and EGFR activation, whereas Src kinase activity is required both for the release of HB-EGF and for HB-EGF-mediated ERK2 phosphorylation. 相似文献
93.
94.
La Linn M Gardner J Warrilow D Darnell GA McMahon CR Field I Hyatt AD Slade RW Suhrbier A 《Journal of virology》2001,75(9):4103-4109
A novel alphavirus was isolated from the louse Lepidophthirus macrorhini, collected from southern elephant seals, Mirounga leonina, on Macquarie Island, Australia. The virus displayed classic alphavirus ultrastructure and appeared to be serologically different from known Australasian alphaviruses. Nearly all Macquarie Island elephant seals tested had neutralizing antibodies against the virus, but no virus-associated pathology has been identified. Antarctic Division personnel who have worked extensively with elephant seals showed no serological evidence of exposure to the virus. Sequence analysis illustrated that the southern elephant seal (SES) virus segregates with the Semliki Forest group of Australasian alphaviruses. Phylogenetic analysis of known alphaviruses suggests that alphaviruses might be grouped according to their enzootic vertebrate host class. The SES virus represents the first arbovirus of marine mammals and illustrates that alphaviruses can inhabit Antarctica and that alphaviruses can be transmitted by lice. 相似文献
95.
Fouling by biofilms significantly increases frictional drag on ships' hulls. A device, the friction disk machine, designed to measure torque on rotating disks, was used to examine differences among experimental fouling-release coatings in the drag penalty due to accumulated biofilms. Penalties were measured as the percentage change in the frictional resistance coefficient Cf. Drag penalties due to microfouling ranged from 9% to 29%, comparable to previously reported values. An antifouling control coating showed a smaller drag penalty than the fouling-release coatings. There were also significant differences among the fouling-release coatings in drag due to biofilm formation. These results indicate that the friction disk machine may serve as a valuable tool for investigating the effects of experimental coatings, both antifouling and fouling-release, on microfouling and associated drag penalties. 相似文献
96.
Field JA Sierra-Alvarez R Cortinas I Feijoo G Moreira MT Kopplin M Gandolfi AJ 《Biodegradation》2004,15(3):185-196
Due to the recent enactment of a stricter drinking water standard for arsenate, large quantities of arsenate-laden drinking water residuals will be disposed in municipal landfills. The objective of this study was to determine the role of methanogenic consortia on the conversion of arsenate. Methanogenic conditions commonly occur in mature municipal solid waste landfills. The results indicate the rapid and facile reduction of arsenate to arsenite in methanogenic sludge. Endogenous substrates in the sludge were sufficient to support the reductive biotransformation. However the rates of arsenate reduction were stimulated by the addition of exogenous electron donating substrates, such as H2, lactate or a mixture of volatile fatty acids. A selective methanogenic inhibitor stimulated arsenate reduction in microcosms supplied with H2, suggesting that methanogens competed with arsenate reducers for the electron donor. Rates of arsenate reduction increased with arsenate concentration up to 2 mM, higher concentrations were inhibitory. The electron shuttle, anthraquinone-2,6-disulfonate, used as a model of humic quinone moieties, was shown to significantly increase rates of arsenate reduction at substoichiometric concentrations. The presence of sulfur compounds, sulfate and sulfide, did not affect the rate of arsenate transformation but lowered the yield of soluble arsenite, due to the precipitation of arsenite with sulfides. The results taken as a whole suggest that arsenate disposed into anaerobic environments may readily be converted to arsenite increasing the mobility of arsenic. The extent of the increased mobility will depend on the concentration of sulfides generated from sulfate reduction. 相似文献
97.
Methanogenic inhibition by arsenic compounds 总被引:2,自引:0,他引:2
Sierra-Alvarez R Cortinas I Yenal U Field JA 《Applied and environmental microbiology》2004,70(9):5688-5691
The acute acetoclastic methanogenic inhibition of several inorganic and organic arsenicals was assayed. Trivalent species, i.e., methylarsonous acid and arsenite, were highly inhibitory, with 50% inhibitory concentrations of 9.1 and 15.0 microM, respectively, whereas pentavalent species were generally nontoxic. The nitrophenylarsonate derivate, roxarsone, displayed moderate toxicity. 相似文献
98.
Intracellular membrane transport systems in Trypanosoma brucei 总被引:1,自引:1,他引:0
Trypanosomes belong to the order kinetoplastida, an early diverging group of organisms in the eukaryotic lineage. The principal reasons for interest in these organisms are twofold; they provide a superb distant triangulation point from which to assess global features of eukaryotic biology and, more importantly, they are representative of a number of pathogenic parasitic protozoa with a huge public health impact --Trypanosoma brucei, T. cruzi and Leishmania spp. Recent advances in the study of intracellular transport in T. brucei have been considerable, and a fuller picture of the complexity, function and role that the endomembrane system plays in trypanosomes is finally emerging. 相似文献
99.
Parallel chemical genetic and genome-wide RNAi screens identify cytokinesis inhibitors and targets
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Eggert US Kiger AA Richter C Perlman ZE Perrimon N Mitchison TJ Field CM 《PLoS biology》2004,2(12):e379
Cytokinesis involves temporally and spatially coordinated action of the cell cycle and cytoskeletal and membrane systems to achieve separation of daughter cells. To dissect cytokinesis mechanisms it would be useful to have a complete catalog of the proteins involved, and small molecule tools for specifically inhibiting them with tight temporal control. Finding active small molecules by cell-based screening entails the difficult step of identifying their targets. We performed parallel chemical genetic and genome-wide RNA interference screens in Drosophila cells, identifying 50 small molecule inhibitors of cytokinesis and 214 genes important for cytokinesis, including a new protein in the Aurora B pathway (Borr). By comparing small molecule and RNAi phenotypes, we identified a small molecule that inhibits the Aurora B kinase pathway. Our protein list provides a starting point for systematic dissection of cytokinesis, a direction that will be greatly facilitated by also having diverse small molecule inhibitors, which we have identified. Dissection of the Aurora B pathway, where we found a new gene and a specific small molecule inhibitor, should benefit particularly. Our study shows that parallel RNA interference and small molecule screening is a generally useful approach to identifying active small molecules and their target pathways. 相似文献
100.
Rogers MB Archibald JM Field MA Li C Striepen B Keeling PJ 《The Journal of eukaryotic microbiology》2004,51(5):529-535
Chlorarachniophytes are marine amoeboflagellate protists that have acquired their plastid (chloroplast) through secondary endosymbiosis with a green alga. Like other algae, most of the proteins necessary for plastid function are encoded in the nuclear genome of the secondary host. These proteins are targeted to the organelle using a bipartite leader sequence consisting of a signal peptide (allowing entry in to the endomembrane system) and a chloroplast transit peptide (for transport across the chloroplast envelope membranes). We have examined the leader sequences from 45 full-length predicted plastid-targeted proteins from the chlorarachniophyte Bigelowiella natans with the goal of understanding important features of these sequences and possible conserved motifs. The chemical characteristics of these sequences were compared with a set of 10 B. natans endomembrane-targeted proteins and 38 cytosolic or nuclear proteins, which show that the signal peptides are similar to those of most other eukaryotes, while the transit peptides differ from those of other algae in some characteristics. Consistent with this, the leader sequence from one B. natans protein was tested for function in the apicomplexan parasite, Toxoplasma gondii, and shown to direct the secretion of the protein. 相似文献