Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038362 (stomatitis)
 8,852 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A key role in the regulation of membrane traffic is played by the rab proteins, members of a family of ras-related small GTP-binding proteins. This family comprises at least 25 identified members, the intracellular localization of only a few of which has been investigated. rab6p has been shown to be distributed along the exocytic pathway in association with the medial and trans regions of the Golgi apparatus. A confocal laser scanning microscopic (CLSM) approach coupled with image analysis was used to compare the localization of rab6p with selected reference Golgi markers by double immunofluorescence on culture cell lines. CLSM analysis shows that, under a set of well-defined conditions, one can investigate the possible colocalization of known markers of Golgi compartments and orientate a couple of labeled Golgi antigens with regard to the polarity of the Golgi apparatus. Thus, having validated the CLSM analysis, the localization of rab6p was studied and compared with some of these markers and the VSV-G protein in VSV (vesicular stomatitis virus)-infected cells blocked at 20 degrees C. rab6p is shown to be associated in all the cell lines used with the last cisternae of the Golgi apparatus and particularly with the trans-Golgi network (TGN), the site of protein sorting at the exit of the Golgi apparatus. These results were supported by an electron microscopic study using double-immunolabeled cryosections: rab6p was found in some flat cisternae of the Golgi stack and colocalized with the VSV-G protein in the TGN. Our results show that the small GTP-binding protein rab6p is distributed from medial Golgi to TGN along the exocytic pathway.
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PMID:The small GTP-binding protein rab6p is distributed from medial Golgi to the trans-Golgi network as determined by a confocal microscopic approach. 147 71

We describe an in vitro system in which post-Golgi vesicles containing metabolically labeled, sialylated, vesicular stomatitis virus (VSV) G protein molecules (VSV-G) are produced from the trans-Golgi network (TGN) of an isolated Golgi membrane fraction. This fraction is prepared from VSV-infected Madin-Darby canine kidney (MDCK) cells in which the (35)S-labeled viral envelope glycoprotein was allowed to accumulate in the trans-Golgi network during a prolonged incubation at 20 degrees C. The vesicles produced in this system are separated from the remnant Golgi membranes by differential centrifugation or by velocity sedimentation in a sucrose gradient. Vesicle production, quantified as the percentage of labeled VSV-G released from the Golgi membranes, is optimal at 37 degrees C and does not occur below 20 degrees C. It requires GTP and the small GTP-binding protein Arf (ADP-ribosylation factor), as well as coat protein type I (COPI) coat components (coatomer) and vesicle scission factors-one of which corresponds to the phosphatidylinositol transfer protein (PITP). Formation of the vesicles does not require GTP hydrolysis which, however, is necessary for their uncoating. Thus, vesicles generated in the presence of the nonhydrolyzable GTP analogs, GTPgammaS or GMP-PNP, retain a coatomer coat visible in the electron microscope, sediment more rapidly in sucrose density gradients than those generated with ATP or GTP, and can be captured with anticoatomerantibodies. The process of coatomer-coated vesicle formation from the TGN can be dissected into two distinct sequential phases, corresponding to coat assembly/bud formation and vesicle scission. The first phase is completed when Golgi fractions are incubated with cytosolic proteins and nonhydrolyzable GTP analogs at 20 degrees C. The scission phase, which leads to vesicle release, takes place when coated Golgi membranes, recovered after phase I, are incubated at higher temperatures in the presence of cytosolic proteins. The scission phase does not take place if protein kinase C inhibitors are added during the first phase, even though these inhibitors do not prevent membrane coating and bud formation. The phosphorylating activity of a protein kinase C, however, plays no role in vesicle formation, since this process does not require ATP.
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PMID:In vitro generation from the trans-Golgi network of coatomer-coated vesicles containing sialylated vesicular stomatitis virus-G protein. 1072 Apr 65