Showing papers on "Cellular compartment published in 2006"
TL;DR: Herpes virions are amongst the most complex virus particles: they comprise in excess of thirty virally encoded proteins, and also contain cellular components, which involves the interaction between viral and cellular proteins in order to locally alter nuclear architecture.
279 citations
TL;DR: It is shown that different ADAMs are involved in distinct cellular compartments and that ADAM10 is responsible for shedding in vesicles, opening up the possibility that exosomes serve as a platform for ectodomain shedding and as a vehicle for the cellular export of soluble molecules.
Abstract: Ectodomain shedding is a proteolytic mechanism by which transmembrane molecules are converted into a soluble form. Cleavage is mediated by metalloproteases and proceeds in a constitutive or inducible fashion. Although believed to be a cell-surface event, there is increasing evidence that cleavage can take place in intracellular compartments. However, it is unknown how cleaved soluble molecules get access to the extracellular space. By analysing L1 (CD171) and CD44 in ovarian carcinoma cells, we show in the present paper that the cleavage induced by ionomycin, APMA (4-aminophenylmercuric acetate) or MCD (methyl-β-cyclodextrin) is initiated in an endosomal compartment that is subsequently released in the form of exosomes. Calcium influx augmented the release of exosomes containing functionally active forms of ADAM10 (a disintegrin and metalloprotease 10) and ADAM17 [TACE (tumour necrosis factor α-converting enzyme)] as well as CD44 and L1 cytoplasmic cleavage fragments. Cleavage could also proceed in released exosomes, but only depletion of ADAM10 by small interfering RNA blocked cleavage under constitutive and induced conditions. In contrast, cleavage of L1 in response to PMA occurred at the cell surface and was mediated by ADAM17. We conclude that different ADAMs are involved in distinct cellular compartments and that ADAM10 is responsible for shedding in vesicles. Our findings open up the possibility that exosomes serve as a platform for ectodomain shedding and as a vehicle for the cellular export of soluble molecules.
257 citations
TL;DR: A protocol for purification of mitochondria from Saccharomyces cerevisiae cells devoid of contamination from other cellular compartments is described.
Abstract: Often preparations of isolated organelles contain other, unwanted, cellular components. For biochemical experiments to determine the localization of newly identified proteins, or to determine the whole set of proteins (or the proteome) from a desired organelle, these unwanted components often confuse the resulting data. For these types of studies, it is crucial to have highly pure fractions of the desired organelle. Here we describe a protocol for purification of mitochondria from Saccharomyces cerevisiae cells devoid of contamination from other cellular compartments.
255 citations
TL;DR: The findings reveal the functional diversity of the rice APx genes and suggest complementation and coordination of the antioxidant defenses in different cellular compartments during development and abiotic stress.
Abstract: Aerobic organisms evolved a complex antioxidant system, which protect the cells against oxidative damage caused by partially reduced oxygen intermediates, also known as reactive oxygen species. In plants, ascorbate peroxidases (EC, 1.11.1.11) catalyze the conversion of H(2)O(2) to H(2)O, using ascorbate as the specific electron donor in this enzymatic reaction. Previously, eight APx genes were identified in the rice (Oryza sativa L.) genome through in silico analysis: two cytosolic isoforms, two putative peroxisomal isoforms, and four putative chloroplastic ones. Using gene-specific probes, we confirmed the presence of the eight APx genes in the rice genome by Southern blot hybridization. Transcript accumulation analysis showed specific expression patterns for each member of the APx family according to developmental stage and in response to salt stress, revealing the complexity of the antioxidant system in plants. Finally, the subcellular localization of rice APx isoforms was determined using GFP-fusion proteins in BY-2 tobacco cells. In agreement with the initial prediction, OSAPX3 was localized in the peroxisomes. On the other hand, the OSAPX6-GFP fusion protein was found in mitochondria of the BY-2 cells, in contrast to the chloroplastic location predicted by sequence analysis. Our findings reveal the functional diversity of the rice APx genes and suggest complementation and coordination of the antioxidant defenses in different cellular compartments during development and abiotic stress.
204 citations
TL;DR: According to the microbe and its survival strategy, different mechanisms to impede access to nutrients may be constitutively present or may be induced by cytokines and other pathways, and membrane transporters may remove nutrients from vacuolar compartments, and enzymes may degrade some growth factors.
Abstract: In addition to oxidative and antibiotic mechanisms of antimicrobial activity, macrophages are able to deprive intracellular pathogens of required nutrients. Thus, microbial killing may not rely only in the toxic environment the microbe reaches but also may result from the scarcity of nutrients in the cellular compartment it occupies. Here, we analyze evidence for such nutriprive (from the latin privare, to deprive of nutrients), antimicrobial mechanisms. Although the direct analysis of nutrient availability is most often not feasible, indirect evidence of lack of nutrients in the microbial organelles has been inferred from the study of mutants, the analysis of gene expression, and the consequences of changing the intracellular location of the pathogen. We propose that according to the microbe and its survival strategy, different mechanisms to impede access to nutrients may be constitutively present or may be induced by cytokines and other pathways. Thus, membrane transporters may remove nutrients from vacuolar compartments, and enzymes may degrade some growth factors. A series of diverse compounds may sequester other molecules required for microbial growth, as exemplified by the action of iron chelators. Modulation of vesicular trafficking may prevent the fusion of certain vesicles containing nutrients with those containing the pathogen, counteracting the evasion strategies of the pathogen. The understanding of these mechanisms will certainly help in designing new therapeutic and prophylactic approaches to preventing infectious diseases.
137 citations
TL;DR: The experiments provide direct evidence for homodimerization/oligomerization of class A GPCR in the ER and Golgi of intact living cells, and suggest that dimer/olIGomer formation is a naturally occurring step in 5-HT2C receptor maturation and processing.
120 citations
TL;DR: This review discusses the current perception of Golgi structure and organization as well as the molecular mechanisms that direct traffic in and out of the Golgi.
84 citations
TL;DR: Experimental data are reviewed showing that mitochondria, chloroplasts as well as nuclei are equipped to generate calcium signal on their own and harbor calcium-dependent biological processes, which have a profound influence on the integrated functioning of the cell.
67 citations
TL;DR: The data suggest conservation of alternative splicing to regulate subcellular distribution of methionine sulfoxide reductases in Drosophila.
Abstract: Methionine sulfoxide reduction is an important protein repair pathway that protects against oxidative stress, controls protein function and has a role in regulation of aging. There are two enzymes that reduce stereospecifically oxidized methionine residues: MsrA (methionine-S-sulfoxide reductase) and MsrB (methionine-R-sulfoxide reductase). In many organisms, these enzymes are targeted to various cellular compartments. In mammals, a single MsrA gene is known, however, its product is present in cytosol, nucleus, and mitochondria. In contrast, three mammalian MsrB genes have been identified whose products are located in different cellular compartments. In the present study, we identified and characterized alternatively spliced forms of mammalian MsrA. In addition to the previously known variant containing an N-terminal mitochondrial signal peptide and distributed between mitochondria and cytosol, a second mouse and human form was detected in silico. This form, MsrA(S), was generated using an alternative first exon. MsrA(S) was enzymatically active and was present in cytosol and nucleus in transfected cells, but occurred below detection limits in tested mouse tissues. The third alternative form lacked the active site and could not be functional. In addition, we found that mitochondrial and cytosolic forms of both MsrA and MsrB in Drosophila could be generated by alternative first exon splicing. Our data suggest conservation of alternative splicing to regulate subcellular distribution of methionine sulfoxide reductases.
56 citations
TL;DR: Results indicate that plastids, either alone or together with the cytosol, are the main center of glutathione synthesis in leaves as well as in roots, and high and stable levels in mitochondria play an important role in cell survival strategies.
Abstract: The intracellular effects of GSH (reduced glutathione) and BSO (buthionine sulfoximine) treatment on glutathione content were investigated with immunogold labeling in individual cellular compartments of Cucurbita pepo L. seedlings. Generally, GSH treatment led to increased levels of glutathione in roots and leaves (up to 3.5-fold in nuclei), whereas BSO treatment significantly decreased glutathione content in all organs. Transmission electron microscopy revealed that glutathione levels in mitochondria, which showed the highest glutathione labeling density of all compartments, remained generally unaffected by both treatments. Since glutathione within mitochondria is involved in the regulation of cell death, these results indicate that high and stable levels of glutathione in mitochondria play an important role in cell survival strategies. BSO treatment significantly decreased glutathione levels (1) in roots by about 78% in plastids and 60.8% in the cytosol and (2) in cotyledons by about 55% in the cytosol and 38.6% in plastids. After a short recovery period, glutathione levels were significantly increased in plastids and the cytosol of root tip cells (up to 3.7-fold) and back to control values in cotyledons. These results indicate that plastids, either alone or together with the cytosol, are the main center of glutathione synthesis in leaves as well as in roots. After GSH treatment for 24 h, severe ultrastructural damage related to increased levels of glutathione was found in roots, in all organelles except mitochondria. Possible negative effects of GSH treatment leading to the observed ultrastructural damage are discussed.
39 citations
TL;DR: It is shown that the level of Pfpmt protein in the infected erythrocyte is regulated in a stage-specific fashion, with high levels detected during the trophozoite stage at the peak of parasite membrane biogenesis.
TL;DR: Current knowledge regarding the role of ABCA1 in vesicular lipid transport mechanisms required for HDL particle formation, and the relationship between ABCA 1 and NPC1 in this process are reviewed.
Abstract: The membrane transporter ATP-binding cassette transporter A1 (ABCA1) has been shown to be the rate-limiting step in the initial formation of plasma high-density lipoprotein (HDL) particles. The mechanisms of action of ABCA1, including its role in the vesicular transport of lipids to the cell surface for the lipidation of HDL apolipoproteins, are not fully understood. Niemann–Pick type C (NPC) disease is most often caused by mutations in the NPC1 gene, whose protein product is believed to facilitate the egress of cholesterol and other lipids from late endosomes and lysosomes to other cellular compartments. This report reviews current knowledge regarding the role of ABCA1 in vesicular lipid transport mechanisms required for HDL particle formation, and the relationship between ABCA1 and NPC1 in this process.
TL;DR: In this article, the authors investigated the effect of TNF-α on the malignant B-cell line Raji, derived from Burkitt lymphoma patients, at different intracellular levels.
Abstract: Tumor necrosis factor (TNF)-alpha, a pleiotropic cytokine, has been shown to induce diverse and opposite effects on lymphoid malignancy depending on TNF receptor system expression. Based on this, we investigated its in vitro dose- and time-related effect on the malignant B-cell line Raji, derived from Burkitt lymphoma patients, at different intracellular levels. The membrane alteration was estimated by lactate dehydrogenase (LDH) release and by flow cytometry; intracellular metabolic energy by determination of the total intracellular LDH activity; total cytosole protein mass by sulforhodamine B assay; and cell growth by incorporation of [3H]thymidine into DNA. Significant increase of LDH through cell membrane alteration was accompanied by decrease of intracellular metabolized energy and total protein mass. TNF-alpha at lower concentrations (125 and 250 pg/ml) significantly induced cell proliferation in comparison with 1,000 pg/ml of TNF-alpha, which induced more cell death. TNF-alpha induced maximal apoptosis rate up to 30% after 24 h, showing more effects for a necrotic form of cell death. Here we reported opposite and diverse effects of TNF-alpha at different intracellular levels in Raji cells, when applied in different assays, showing characteristics for every cellular compartment.
TL;DR: It is shown that aggregation of a protein containing a polyglutamine stretch of pathological length is abolished when its expression is targeted to the endoplasmic reticulum, suggesting the existence of compartment-specific cofactors promoting or preventing aggregation of pathological proteins.
Abstract: Aggregation of misfolded proteins is a characteristic of several neurodegenerative diseases. The huntingtin amino-terminal fragment with extended polyglutamine repeat forms aggregates closely associated with chaperones both in the cytoplasm and the nucleus. Because each cellular compartment contains distinct chaperones and because the molecular mechanisms controlling polyglutamine aggregation are largely unknown, we decided to investigate the influence of different cellular environments on the aggregation of this pathological protein. Here, we show that aggregation of a protein containing a polyglutamine stretch of pathological length is abolished when its expression is targeted to the endoplasmic reticulum. Once retrogradely transported outside the endoplasmic reticulum, the aggregation-prone polyglutamine-containing protein recovers its ability to aggregate. When expressed in the mitochondria, a protein containing 73 glutamines is entirely soluble, whereas the nucleocytosolic equivalent has an extremely high tendency to aggregate. Our data imply that polyglutamine aggregation is a property restricted to the nucleocytosolic compartment and suggest the existence of compartment-specific cofactors promoting or preventing aggregation of pathological proteins.
TL;DR: This new model provides a gradual Darwinistic evolutionary model of the origins of the eukaryotic cell and suggests an inherent ability of an ancestral, primitive genome to induce its own inclusion in a membrane.
Abstract: Current theories about the origin of the eukaryotic cell all assume that during evolution a prokaryotic cell acquired a nucleus. Here, it is shown that a scenario in which the nucleus acquired a plasma membrane is inherently less complex because existing interfaces remain intact during evolution. Using this scenario, the evolution to the first eukaryotic cell can be modeled in three steps, based on the self-assembly of cellular membranes by lipid-protein interactions. First, the inclusion of chromosomes in a nuclear membrane is mediated by interactions between laminar proteins and lipid vesicles. Second, the formation of a primitive endoplasmic reticulum, or exomembrane, is induced by the expression of intrinsic membrane proteins. Third, a plasma membrane is formed by fusion of exomembrane vesicles on the cytoskeletal protein scaffold. All three self-assembly processes occur both in vivo and in vitro. This new model provides a gradual Darwinistic evolutionary model of the origins of the eukaryotic cell and suggests an inherent ability of an ancestral, primitive genome to induce its own inclusion in a membrane.
TL;DR: The results of the present study indicate that glutathione degradation occurs within vacuoles or at the tonoplast, rather than at the plasmalemma or in the apoplast.
Abstract: In plant cells, the antioxidant glutathione is synthesized out of its constituents cysteine, glutamate and glycine. As information about their subcellular and cellular distribution was not available in the past, the aim of the present study was to develop a technique that would allow visualization of their distribution in plant cells. With selective antibodies against cysteine, glutamate and glycine, it was possible, for the first time, to study the relative distribution of these components in meristematic root tip cells and mesophyll cells from older and younger leaves of Cucurbita pepo plants with the transmission electron microscope. These investigations revealed that high levels of cysteine accumulated in younger leaves. However, glutamate and glycine accumulated in the older ones, where cysteine levels were found to be significantly lower. On the subcellular level, glutamate was found in similar content in all investigated cellular compartments except for the cytosol, which showed up to 49% lower glutamate content (in younger leaves) than the other cell compartments. Levels of glycine were similar in all investigated cell compartments of one organ except vacuoles, which contained the lowest amounts of glycine. Cysteine was highest in plastids, the cytosol and in nuclei. When compared with younger leaves, glutamate and glycine were found to be accumulated in plastids (180 and 83%) and the cytosol (142 and 130%) of older leaves, whereas cysteine contents were found to be very low in the glutathione producing cell compartments of the leaves. These results indicate that low levels of cysteine might be a limitation for glutathione synthesis in older leaves. Cysteine and glycine were also detected in vacuoles where glutamate was absent. None of these components were detected in the apoplast. Therefore, these results indicate that glutathione degradation occurs within vacuoles or at the tonoplast, rather than at the plasmalemma or in the apoplast. Summing up, with the methods presented in this and a previous work, it is now possible to study the subcellular distribution of glutathione and its precursors in one plant sample simultaneously. The application of these methods on plant samples during abiotic and biotic stress situations should help us reveal possible limitations of glutathione synthesis during oxidative stress.
TL;DR: The mechanisms of nuclear translocation of endogenous signaling components, like p53, NFkappaB and various heat shock proteins (HSPs), may serve as targets for pharmacological intervention, without excluding the possible role of uptake and active transport into the nucleus of extracellular proteins.
Abstract: The function of many endogenous molecules in all eukaryotic cells depends on their subcellular localisation, being active when localized in one cellular compartment and inactive in another. Translocation or re-localization of mislocalized components in the optimal subcellular site may contribute to the development of novel cancer therapies and to the re-evaluation of conventional treatment. For instance, various agents are able to entrap cytoplasmic anti-apoptotic pathways to the nucleus, thus activating apoptosis. Moreover, amongst the factors identified so far, the optimal location of the tumor suppressor p53 for promoting cell arrest and apoptosis seems to be the nucleus, while the nuclear factor kappa B (NFkappaB) is desirable to stay in the cytoplasm. Thus, the mechanisms of nuclear translocation of endogenous signaling components, like p53, NFkappaB and various heat shock proteins (HSPs), may serve as targets for pharmacological intervention, without excluding the possible role of uptake and active transport into the nucleus of extracellular proteins.
TL;DR: It is suggested that chain length of dolichols synthesized in yeast cell may depend on the carbon and energy source supply which mobilizes metabolic pathways localized to different cellular compartments.
01 Jan 2006
TL;DR: The techniques used for subcellular localization of plants protein include fusion reporter gene localization, immunohistochemical localization, 2D combined with mass spectrometry, marker enzyme-assisted localization and bioinformatics prediction.
Abstract: Cell is the fundamental unit of living organism,proteins with different functions distributed in cellular compartments,including plasmolemma,nucleus,cytoplasm and organelles like mitochondria,chloroplast,Golgi,and endoplasmic reticulum etc.Protein subcellular localization is one of the key questions for functional genomics.The techniques used for subcellular localization of plants protein include fusion reporter gene localization,immunohistochemical localization,2D combined with mass spectrometry,marker enzyme-assisted localization and bioinformatics prediction.The development and application of high-throughtput protein subcellular localization technology stimulated the establishment of protein subcellular localization database.In model plant Arabidopsis thaliana,the number of proteins with localization data is over 4000.
01 Jan 2006
TL;DR: The objective of the present review is to bring the attention about Carnitine and its role in lipid metabolism.
Abstract: Carnitine(3-hydroxy-4-N-trimethylaminobutyrate) is a water-soluble molecule, which is most likely present in all animal species and in numerous micro organisms and plants. It is also involved in transporting activated fatty acids between different cellular compartments. The objective of the present review is to bring the attention about this molecule and its role in lipid metabolism.
TL;DR: Possible involvement of AAT isozymes in the coordination of carbon and nitrogen metabolism through the regulation of 2-oxoglutarate synthesis and utilization in different cellular compartments is discussed.
Abstract: Intracellular distribution of aspartate aminotransferase (AAT) in Spirodela polyrhiza (Lemnaceae), strain SJ, has been studied by differential centrifugation. The bulk of the enzyme (73% of total cellular content) was localized in the cytoplasm and 24% activity was localized in chloroplasts. Purified cytoplasmic and chloroplastic isozymes differed by their affinity for substrates. The reaction balance was shifted towards direct and reverse transamination in the cytoplasm and chloroplast, respectively. Competitive inhibition of AAT by excessive substrates and enzyme affinity modulation by certain intermediates of the tricarboxylic acid cycle (isocitrate, succinate, and citrate) were observed. Possible involvement of AAT isozymes in the coordination of carbon and nitrogen metabolism through the regulation of 2-oxoglutarate synthesis and utilization in different cellular compartments is discussed.