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991.
992.
Molecular mechanism of mitotic Golgi disassembly and reassembly revealed by a defined reconstitution assay 总被引:1,自引:0,他引:1
In mammalian cells, flat Golgi cisternae closely arrange together to form stacks. During mitosis, the stacked structure undergoes a continuous fragmentation process. The generated mitotic Golgi fragments are distributed into the daughter cells, where they are reassembled into new Golgi stacks. In this study, an in vitro assay has been developed using purified proteins and Golgi membranes to reconstitute the Golgi disassembly and reassembly processes. This technique provides a useful tool to delineate the mechanisms underlying the morphological change. There are two processes during Golgi disassembly: unstacking and vesiculation. Unstacking is mediated by two mitotic kinases, cdc2 and plk, which phosphorylate the Golgi stacking protein GRASP65 and thus disrupt the oligomer of this protein. Vesiculation is mediated by the COPI budding machinery ARF1 and the coatomer complex. When treated with a combination of purified kinases, ARF1 and coatomer, the Golgi membranes were completely fragmented into vesicles. After mitosis, there are also two processes in Golgi reassembly: formation of single cisternae by membrane fusion, and restacking. Cisternal membrane fusion requires two AAA ATPases, p97 and NSF (N-ethylmaleimide-sensitive fusion protein), each of which functions together with specific adaptor proteins. Restacking of the newly formed Golgi cisternae requires dephosphorylation of Golgi stacking proteins by the protein phosphatase PP2A. This systematic study revealed the minimal machinery that controls the mitotic Golgi disassembly and reassembly processes. 相似文献
993.
Melcher M Unger B Schmidt U Rajantie IA Alitalo K Ellmeier W 《Journal of immunology (Baltimore, Md. : 1950)》2008,180(12):8048-8056
Tec family kinases have important roles in lymphocytes; however, little is known about their function in monocytes/macrophages. In this study we report that Tec family kinases are essential for M-CSF (M-CSF)-induced signaling pathways that regulate macrophage survival. Compared with wild-type bone marrow-derived macrophage (BMM) cultures, Tec(-/-)Btk(-/-) BMM cultures displayed increased cell death that correlated with a severe drop in macrophage numbers. In addition, macrophages deficient in either Tec or Btk showed expression and activation of caspase-11. Elucidation of M-CSF receptor (M-CSFR) signaling pathways revealed that the total tyrosine phosphorylation pattern upon M-CSF stimulation was altered in Tec(-/-)Btk(-/-) macrophages despite normal expression and phosphorylation of the M-CSFR. Further, Tec and Btk are required for proper expression of the GM-CSF receptor alpha (GM-CSFRalpha) chain in macrophages but not dendritic cells, implicating Tec family kinases in the lineage-specific regulation of GM-CSFRalpha expression. Taken together, our study shows that Tec and Btk regulate M-CSFR signaling-induced macrophage survival and provides a novel link between Tec family kinases and the regulation of caspase-11 and GM-CSFRalpha expression. 相似文献
994.
Cole LE Santiago A Barry E Kang TJ Shirey KA Roberts ZJ Elkins KL Cross AS Vogel SN 《Journal of immunology (Baltimore, Md. : 1950)》2008,180(10):6885-6891
The macrophage proinflammatory response to Francisella tularensis (Ft) live vaccine strain (LVS) was shown previously to be TLR2 dependent. The observation that intracellular Ft LVS colocalizes with TLR2 and MyD88 inside macrophages suggested that Ft LVS might signal from within the phagosome. Macrophages infected with LVSDeltaiglC, a Ft LVS mutant that fails to escape from the phagosome, displayed greatly increased expression of a subset of TLR2-dependent, proinflammatory genes (e.g., Tnf) but decreased expression of others (e.g., Ifnb1). This latter subset was similarly mitigated in IFN-beta(-/-) macrophages indicating that while Ft LVS-induced TLR2 signaling is necessary, cytosolic sensing of Ft to induce IFN-beta is required for full induction of the macrophage proinflammatory response. Although LVSDeltaiglC greatly increased IL-1beta mRNA in wild-type macrophages, protein secretion was not observed. IL-1beta secretion was also diminished in Ft LVS-infected IFN-beta(-/-) macrophages. rIFN-beta failed to restore IL-1beta secretion in LVSDeltaiglC-infected macrophages, suggesting that signals in addition to IFN-beta are required for assembly of the inflammasome and activation of caspase-1. IFN-beta plays a central role in controlling the macrophage bacterial burden: bacterial recovery was greater in IFN-beta(-/-) than in wild-type macrophages and treatment of Ft LVS-infected macrophages with rIFN-beta or 5,6-dimethylxanthenone-4-acetic acid, a potent IFN-beta inducer, greatly decreased the intracellular Ft LVS burden. In toto, these observations support the hypothesis that the host inflammatory response to Ft LVS is complex and requires engagement of multiple signaling pathways downstream of TLR2 including production of IFN-beta via an unknown cytosolic sensor and activation of the inflammasome. 相似文献
995.
996.
Kari Pietilä 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,677(2):318-325
This study sought to elucidate the optimal cell culture conditions for studies concerned with the incorporation of [3H]glucosamine into glycosaminoglycans by rabbit aortic smooth muscle cells. The incorporation of radioactivity into extracellular sulphated glycosaminoglycans was linear for at least 72 h and that into pericellular sulphated glycosaminoglycans for up to 24 h. The incorporation of radiolabel into hyaluronic acid was linear only up to 12 h. In the exponential growth phase the incorporation of [3H]glucosamine into sulphated glycosaminoglycans and hyaluronic acid proved to be less marked than in the stationary growth phase, but the highest values were nevertheless obtained immediately after trypsinisation. When studied in the stationary growth phase, cell density and incorporation of [3H]glucosamine were positively correlated in the case of hyaluronic acid, but in the case of sulphated glycosaminoglycans there was a negative correlation. The serum concentration of the incubation medium and the incorporation of radioactivity into hyaluronic acid were positively related. With sulphated glycosaminoglycans this was the case only after a 7-day preincubation in the different serum concentrations. when incorporation was studied without preincubation, the incorporation of radioactivity into sulphated glycosaminoglycans proved to be negatively associated with the serum concentration of the medium. The environmental pH of the cells was associated with the incorporation of radioactivity into hyaluronic acid and sulphated glycosaminoglycans in that between pH values 6.8 and 7.9 the incorporation of radioactivity increased when the pH of the medium was raised. 相似文献
997.
Kristina Sundqvist Yun Liu Kristina Arvidson Kari Ormstad Lennart Nilsson Rune Toftgård Roland C. Grafström 《In vitro cellular & developmental biology. Animal》1991,27(7):562-568
Summary Human buccal epithelial cells have been reared from explants maintained in supplemented MCDB 153 medium. Primary epithelial
outgrowths show typical structural features and uniformly express keratins; subunit analyses demonstrate expression of keratins
5, 6, 14, 16/17, and 19. The cells exhibit up to 6% colony forming efficiency and divide at about 0.8 population doublings
per day on fibronectin/collagen-coated dishes at clonal density. Studies of markers of proliferation and differentiation in
buccal epithelial cells indicate that epidermal growth factor, cholera toxin, retinoic acid, and pituitary extract each exhibit
a distinctive ability to enhance growth and variably affect cell migration and cell surface area. Transforming growth factorβ-1 inhibits growth and increases surface area without affecting migration, involucrin expression, and cross-linked envelope
formation. Moreover, exposure of cells to fetal bovine serum, the tumor promoting agent 12-O-tetradecanoylphorbol-13-acetate or an elevated Ca2+ concentration (from 0.1 to 1 mM) inhibits growth and induces squamous differentiation as indicated by inhibition of migration, increases in surface area,
involucrin expression, or formation of cross-linked envelopes. The results show that epithelial cells can be reproducibly
derived from explant cultures of human buccal mucosa specimens and the cells transferred under serum-free conditions. Buccal
epithelial cells in culture undergo a pattern of growth and differentiation that mimics parakeratinization in vivo and variably
respond to several agents shown to modulate growth of cells that originate from other types of epithelia.
This work was supported in part by grants from the Swedish National Board of Laboratory Animals, the Swedish Medical Research
Council, the Swedish Natural Science Research Council, the Swedish Fund for Scientific Research Without Animal Experiments,
the Swedish Cancer Society, the Swedish Tobacco Company, and Lions Club International, Djurg?rden, Stockholm, Sweden. 相似文献
998.
In Escherichia coli, amino acid starvation triggers the rapid synthesis of two guanosine polyphosphates, pppGpp and ppGpp (the 3'-pyrophosphates of GTP and GDP, respectively). Determination of the turnover rate of the ppGpp pool indicated that during serine deprivation, as opposed to other amino acid starvations, the rate of ppGpp degradation is dramatically decreased. This results in a slow but significant accumulation of this regulatory nucleotide in a relA mutant during serine starvation. Similar ppGpp accumulation can be seen during serine starvation in different serine auxotrophic mutants carrying different relA alleles. On the other hand, no ppGpp accumulation is induced in various relaxed strains by serine hydroxamate treatment. 相似文献
999.
1000.
Grace K. Charles Corinna Riginos Kari E. Veblen Duncan M. Kimuyu Truman P. Young 《Ecology and evolution》2021,11(12):7226
Both termites and large mammalian herbivores (LMH) are savanna ecosystem engineers that have profound impacts on ecosystem structure and function. Both of these savanna engineers modulate many common and shared dietary resources such as woody and herbaceous plant biomass, yet few studies have addressed how they impact one another. In particular, it is unclear how herbivores may influence the abundance of long‐lived termite mounds via changes in termite dietary resources such as woody and herbaceous biomass. While it has long been assumed that abundance and areal cover of termite mounds in the landscape remain relatively stable, most data are observational, and few experiments have tested how termite mound patterns may respond to biotic factors such as changes in large herbivore communities. Here, we use a broad tree density gradient and two landscape‐scale experimental manipulations—the first a multi‐guild large herbivore exclosure experiment (20 years after establishment) and the second a tree removal experiment (8 years after establishment)—to demonstrate that patterns in Odontotermes termite mound abundance and cover are unexpectedly dynamic. Termite mound abundance, but areal cover not significantly, is positively associated with experimentally controlled presence of cattle, but not wild mesoherbivores (15–1,000 kg) or megaherbivores (elephants and giraffes). Herbaceous productivity and tree density, termite dietary resources that are significantly affected by different LMH treatments, are both positive predictors of termite mound abundance. Experimental reductions of tree densities are associated with lower abundances of termite mounds. These results reveal a richly interacting web of relationships among multiple savanna ecosystem engineers and suggest that termite mound abundance and areal cover are intimately tied to herbivore‐driven resource availability. 相似文献