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Studies of intracellular traffic in yeast and mammalian systems have implicated members of the Rab family of small GTP-binding proteins as regulators of membrane fusion. We have used the patch clamp technique to measure exocytotic fusion events directly and investigate the role of GTP-binding proteins in regulating exocytosis in mast cells. Intracellular perfusion of mast cells with GTP-gamma S is sufficient to trigger complete exocytotic degranulation in the absence of other intracellular messengers. Here we show that GTP is a potent inhibitor of GTP-gamma S-induced degranulation, indicating that sustained activation of a GTP-binding protein is sufficient for membrane fusion. We have found that synthetic oligopeptides, corresponding to part of the effector domain of Rab3a, stimulate complete exocytotic degranulation, similar to that induced by GTP-gamma S. The response is selective for Rab3a sequence and is strictly dependent on Mg2+ and ATP. This suggests that sustained activation of a Rab3 protein causes exocytotic fusion. The peptide response can be accelerated by GDP-beta S, suggesting that Rab3a peptides compete with endogenous Rab3 proteins for a binding site on a target effector protein, which causes fusion on activation. 相似文献
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The Amazon basin in transition 总被引:7,自引:0,他引:7
Davidson EA de Araújo AC Artaxo P Balch JK Brown IF C Bustamante MM Coe MT DeFries RS Keller M Longo M Munger JW Schroeder W Soares-Filho BS Souza CM Wofsy SC 《Nature》2012,481(7381):321-328
Agricultural expansion and climate variability have become important agents of disturbance in the Amazon basin. Recent studies have demonstrated considerable resilience of Amazonian forests to moderate annual drought, but they also show that interactions between deforestation, fire and drought potentially lead to losses of carbon storage and changes in regional precipitation patterns and river discharge. Although the basin-wide impacts of land use and drought may not yet surpass the magnitude of natural variability of hydrologic and biogeochemical cycles, there are some signs of a transition to a disturbance-dominated regime. These signs include changing energy and water cycles in the southern and eastern portions of the Amazon basin. 相似文献
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Stagg SM Gürkan C Fowler DM LaPointe P Foss TR Potter CS Carragher B Balch WE 《Nature》2006,439(7073):234-238
Endomembranes of eukaryotic cells are dynamic structures that are in continuous communication through the activity of specialized cellular machineries, such as the coat protein complex II (COPII), which mediates cargo export from the endoplasmic reticulum (ER). COPII consists of the Sar1 GTPase, Sec23 and Sec24 (Sec23/24), where Sec23 is a Sar1-specific GTPase-activating protein and Sec24 functions in cargo selection, and Sec13 and Sec31 (Sec13/31), which has a structural role. Whereas recent results have shown that Sec23/24 and Sec13/31 can self-assemble to form COPII cage-like particles, we now show that Sec13/31 can self-assemble to form minimal cages in the absence of Sec23/24. We present a three-dimensional reconstruction of these Sec13/31 cages at 30 A resolution using cryo-electron microscopy and single particle analysis. These results reveal a novel cuboctahedron geometry with the potential to form a flexible lattice and to generate a diverse range of containers. Our data are consistent with a model for COPII coat complex assembly in which Sec23/24 has a non-structural role as a multivalent ligand localizing the self-assembly of Sec13/31 to form a cage lattice driving ER cargo export. 相似文献
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Vesicular transport between the endoplasmic reticulum and the Golgi stack requires the NEM-sensitive fusion protein 总被引:55,自引:0,他引:55
An N-ethylmaleimide-sensitive fusion protein (NSF) has been purified on the basis of its ability to catalyse vesicular transport within the Golgi stack. We report here that this same protein is required for transport from the endoplasmic reticulum to the Golgi stack in semi-intact cells. This transport process is inhibited by a monoclonal antibody against NSF. Furthermore, pretreatment of semi-intact cells with N-ethylmaleimide, a sulphydryl alkylating reagent, inhibits transport. Addition of highly purified NSF largely restores transport from endoplasmic reticulum to Golgi. These results suggest that NSF is a general component of the transport machinery required for membrane fusion at multiple stages of the secretory pathway. 相似文献
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Zusammenfassung Die histochemische Fluoreszenzmethode wird zum Studium der Nervenzellen des Gehirnstammes der Ratte angewandt. Die erhebliche Zunahme des Dopamins, hervorgerufen durch die Injektion eines peripher wirkenden Dekarboxylase-Hemmstoffes zusammen mitl-DOPA, wird im Gehirn verfolgt und gefunden, dass serotonergische Neuronen imstande sind, Catecholamine aufzunehmen.
This work has been supported by the Clinical Research Center for Parkinson's and Allied Diseases, grant No. NS05184. 相似文献
This work has been supported by the Clinical Research Center for Parkinson's and Allied Diseases, grant No. NS05184. 相似文献
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