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已知细胞间的信息交流不仅可以通过直接接触,或释放信号分子等方式,同时还存在另一种细胞通讯方式即释放外泌体。外泌体是由细胞分泌,直径为30~100 nm的囊泡结构。外泌体含有蛋白质、脂质、mRNAs和miRNAs等成分,并且能够靶向运输到其他细胞或组织中,从而在细胞间的信息交流、物质传递方面发挥重要作用。本文对外泌体的基本特征、形成过程、功能以及在疾病诊断与治疗中的应用等方面进行简要综述,重点介绍外泌体在免疫调控和肿瘤发生方面的功能。外泌体作为一种广泛存在的亚细胞成分,虽然体积小,组成成分简单,然而,其复杂功能具有重要的研究价值。对外泌体功能的深入了解将为肿瘤等疾病的预防和治疗提供更多的诊断标志物、疫苗以及治疗思路与手段。 相似文献
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In many non-excitable eukaryotic cells, including hepatocytes, Ca2+ oscillations play a key role in intra- and intercellular signalling, thus regulating many cellular processes from fertilisation to death. Therefore, understanding the mechanisms underlying these oscillations, and consequently understanding how they may be regulated, is of great interest. In this paper, we study the influence of reduced Ca2+ plasma membrane efflux on Ca2+ oscillations in hepatocytes. Our previous experiments with carboxyeosin show that a reduced plasma membrane Ca2+ efflux increases the frequency of Ca2+ oscillations, but does not affect the duration of individual transients. This phenomenon can be best explained by taking into account not only the temporal, but also the spatial dynamics underlying the generation of Ca2+ oscillations in the cell. Here we divide the cell into a grid of elements and treat the Ca2+ dynamics as a spatio-temporal phenomenon. By converting an existing temporal model into a spatio-temporal one, we obtain theoretical predictions that are in much better agreement with the experimental observations. 相似文献
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Administration of cortisol to an animal induces tyrosine aminotransferase (TAT) in the liver. A similar effect was observed after stimulation of resident liver macrophages (Kupffer cells) by dextran sulfate. Actinomycin D completely blocks enzyme induction both by cortisol and dextran sulfate, whereas their combined effect gives an additive result. In primary culture of hepatocytes, dextran sulfate inhibits TAT activity, but conditioned macrophage medium reliably increases enzyme activity in hepatocytes. However, incubation of isolated macrophages in the presence of dextran sulfate and such medium transfer into hepatocyte culture results in even more pronounced increase in TAT activity. In a combined culture of hepatocytes and non-parenchymal liver cells, reproducing intercellular interactions in vitro, cortisol and non-parenchymal cells exhibit an additive effect on TAT activity. These results show that liver macrophages release a factor of unknown nature launching the mechanism of TAT induction independently of cortisol, a classic TAT inducer. 相似文献
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Leaf metabolism produces H2O2 at high rates, but current conceptssuggest that the potent signalling effects of this oxidant requirethat concentrations be controlled by a battery of antioxidativeenzymes. The extent to which H2O2 is allowed to accumulate remainsunclear. There is little consensus on leaf H2O2 values in theliterature and measured concentrations in unstressed conditionsrange from 50–5000 nmol g–1 fresh weight, a differencethat probably reflects technical inaccuracies as much as biologicalvariability. This article uses new experimental and literaturedata to examine some of the difficulties in accurately measuringH2O2 in leaf extracts. Potential problems relate to sensitivity,interference from other redox-active compounds, and H2O2 stabilityduring sample preparation. Particular attention is drawn tothe influence of tissue mass/extraction volume in the quantitativeestimation of H2O2 contents, and the possibility that this factorcould contribute to the variability of literature data. Key words: Ascorbate, chemiluminescence, oxidative stress, redox signalling, xylenol orange
Received 4 June 2007; Revised 18 June 2007 Accepted 23 June 2007 相似文献
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Tomato ethylene receptor-CTR interactions: visualization of NEVER-RIPE interactions with multiple CTRs at the endoplasmic reticulum 总被引:3,自引:0,他引:3
In the model plant Arabidopsis, members of a family of two-componentsystem His kinase-like ethylene receptors have direct protein–proteininteractions with a single downstream Ser/Thr kinase CTR1. Thesecomponents of the ethylene signalling network found in Arabidopsisare conserved in the climacteric fruit tomato, but both theethylene receptors and CTR1-like proteins (LeCTRs) in tomatoare encoded by multigene families. Here, using a yeast two-hybridinteraction assay, it is shown that the tomato receptors LeETR1,LeETR2, and NEVER-RIPE (NR) can interact with multiple LeCTRs.In vivo protein localization studies with fluorescent taggedproteins revealed that the ethylene receptor NR was targetedto the endoplasmic reticulum (ER) when transiently expressedin onion epidermal cells, whereas the four LeCTR proteins werefound in the cytoplasm and nucleus. When co-expressed with NR,three LeCTRs (1, 3, and 4), but not LeCTR2, also adopted thesame ER localization pattern in an NR receptor-dependent mannerbut not in the absence of NR. The receptor–CTR interactionswere confirmed by biomolecular fluorescence complementation(BiFC) showing that NR could form a protein complex with LeCTR1,3, and 4. This suggested that ethylene receptors recruit theseLeCTR proteins to the ER membrane through direct protein–proteininteraction. The receptor–CTR interactions and localizationobserved in the study reinforce the idea that ethylene receptorstransmit the signal to the downstream CTRs and show that a singlereceptor can interact with multiple CTR proteins. It remainsunclear whether the different LeCTRs are functionally redundantor have unique roles in ethylene signalling. Key words: BiFC, endoplasmic reticulum, Ser/Thr kinase, tomato ethylene signalling, two-component system His kinase 相似文献