Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “compartmentalization”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources
PubMed2004

Caveolae compartmentalization of heme oxygenase-1 in endothelial cells.

The heme oxygenase (HO) and nitric oxide synthase (NOS) enzymes generate the gaseous signaling molecules carbon monoxide (CO) and nitric oxide, respectively. Constitutive NOSs localize to caveolae, and their activities are modulated by caveolin-1. Nothing is known of the localization of the inducible heme oxygenase-1 (HO-1) in plasma membrane caveolae. Thus, we examined the distribution and subcellular localization of HO-1, biliverdin reductase (BVR), and NADPH:cytochrome P450 reductase (NPR) in pulmonary artery endothelial cells. Each of these proteins localized in part to plasma membrane caveolae in endothelial cells. Inducers of HO-1 or overexpression of HO-1 increased the content of this protein in a detergent-resistant fraction containing caveolin-1. Inducible HO activity appeared in plasma membrane, cytosol, and isolated caveolae. In addition, caveolae contained endogenous BVR activity, supporting the same compartmentalization of both enzymes. Caveolin-1 physically interacted with HO-1, as shown by coimmunoprecipitation studies. HO activity dramatically increased in cells expressing caveolin-1 antisense transcripts, suggesting a negative regulatory role for caveolin-1. Conversely, caveolin-1 expression attenuated LPS-inducible HO activity. Since their initial characterization in 1969, HO enzymes have been described as endoplasmic reticulum-associated proteins. We demonstrate for the first time the localization of heme degradation enzymes to plasma membrane caveolae, and present novel evidence that caveolin-1 interacts with and modulates HO activity.

Animals↗
PubMed1997

ATP compartmentation in human erythrocytes.

This review covers not only the current status of the field but also the evidence on which the concept of ATP compartmentation is based. It is hoped that such a survey may help to stimulate work in this area and to broaden the appreciation of its reality and functions. Some may be surprised to learn that mature human erythrocytes, known to be devoid of intracellular organelles, can sequester ATP, but they may not have taken into account the possible roles of the complex cytoskeleton that is tethered to the cells' plasma membrane. The functional significance of the ATP pools springs from the likelihood that they serve as both an energy reserve, capable of sustaining ion pumping during periods of transient stress, as well as a putative transduction mechanism by which the cell's cytoskeleton may sense cellular energy stores.

Adenosine Triphosphate↗
PubMed1991

Evidence for a compartmentation of penicillin biosynthesis in a high- and a low-producing strain of Penicillium chrysogenum.

Pulse-chase experiments using [U14C]valine were done with P2 and Q176, high- and low-penicillin-producing strains of Penicillium chrysogenum. The metabolic flux of this amino acid into protein and penicillin was measured, and compartmentation of penicillin biosynthesis was assessed. Strain P2 took up 14C-valine more slowly than strain Q176, but their rates of incorporation into protein were comparable. Incorporation of 14C-valine into penicillin occurred immediately with the high-producer P2, but exhibited a lag with Q176. After 14C-valine had been removed from the medium, the specific radioactivity of penicillin continued to increase in Q176 but started to decrease immediately in P2. The specific radioactivities of 14C-valine in protein and in penicillin were significantly different in both strains: Q176 had a higher specific radioactivity of valine in penicillin than P2, whereas P2 had a higher specific radioactivity of valine in protein than Q176. Moreover, the specific radioactivity of 14C-valine in penicillin was 20-fold higher in strain Q176 than in P2. These results indicate that penicillin and protein biosynthesis use different pools of cellular valine, and that exchange of valine between the two compartments is slow in the low-producer, but rapid in the high-producer strain. Hence these results indicate a further control point of penicillin biosynthesis in P. chrysogenum.

2-Aminoadipic Acid↗
PubMed1999

Compartmentalized signaling by GPI-anchored ephrin-A5 requires the Fyn tyrosine kinase to regulate cellular adhesion.

Eph receptor tyrosine kinases and their corresponding surface-bound ligands, the ephrins, provide cues to the migration of cells and growth cones during embryonic development. Here we show that ephrin-A5, which is attached to the outer leaflet of the plasma membrane by a glycosyl-phosphatidylinositol-anchor, induces compartmentalized signaling within a caveolae-like membrane microdomain when bound to the extracellular domain of its cognate Eph receptor. The physiological response induced by this signaling event is concomitant with a change in the cellular architecture and adhesion of the ephrin-A5-expressing cells and requires the activity of the Fyn protein tyrosine kinase. This study stresses the relevance of bidirectional signaling involving the ephrins and Eph receptors during brain development.

3T3 Cells↗
PubMed2004

Reconstruction and validation of Saccharomyces cerevisiae iND750, a fully compartmentalized genome-scale metabolic model.

A fully compartmentalized genome-scale metabolic model of Saccharomyces cerevisiae that accounts for 750 genes and their associated transcripts, proteins, and reactions has been reconstructed and validated. All of the 1149 reactions included in this in silico model are both elementally and charge balanced and have been assigned to one of eight cellular locations (extracellular space, cytosol, mitochondrion, peroxisome, nucleus, endoplasmic reticulum, Golgi apparatus, or vacuole). When in silico predictions of 4154 growth phenotypes were compared to two published large-scale gene deletion studies, an 83% agreement was found between iND750's predictions and the experimental studies. Analysis of the failure modes showed that false predictions were primarily caused by iND750's limited inclusion of cellular processes outside of metabolism. This study systematically identified inconsistencies in our knowledge of yeast metabolism that require specific further experimental investigation.

Cell Compartmentation↗
PubMed2001

Analysis of the compartmentation of glycolytic intermediates, nucleotides, sugars, organic acids, amino acids, and sugar alcohols in potato tubers using a nonaqueous fractionation method.

The compartmentation of metabolism in heterotrophic plant tissues is poorly understood due to the lack of data on metabolite distributions and fluxes between subcellular organelles. The main reason for this is the lack of suitable experimental methods with which intracellular metabolism can be measured. Here, we describe a nonaqueous fractionation method that allows the subcellular distributions of metabolites in developing potato (Solanum tuberosum L. cv Desiree) tubers to be calculated. In addition, we have coupled this fractionation method to a recently described gas chromatography-mass spectrometry procedure that allows the measurement of a wide range of small metabolites. To calculate the subcellular metabolite concentrations, we have analyzed organelle volumes in growing potato tubers using electron microscopy. The relative volume distributions in tubers are very similar to the ones for source leaves. More than 60% of most sugars, sugar alcohols, organic acids, and amino acids were found in the vacuole, although the concentrations of these metabolites is often higher in the cytosol. Significant amounts of the substrates for starch biosynthesis, hexose phosphates, and ATP were found in the plastid. However, pyrophosphate was located almost exclusively in the cytosol. Calculation of the mass action ratios of sucrose synthase, UDP-glucose pyrophosphorylase, phosphoglucosisomerase, and phosphoglucomutase indicate that these enzymes are close to equilibrium in developing potato tubers. However, due to the low plastidic pyrophosphate concentration, the reaction catalyzed by ADP-glucose pyrophosphorylase was estimated to be far removed from equilibrium.

Amino Acids↗
PubMed2005

Contributions of protein structure and gene position to the compartmentalization of the regulatory proteins sigma(E) and SpoIIE in sporulating Bacillus subtilis.

At an early stage in endospore formation Bacillus subtilis partitions itself into two dissimilar compartments with unique developmental fates. Transcription appropriate to each compartment is initiated by the activation of compartment-specific RNA polymerase sigma subunits, sigma(E) in the mother cell and sigma(F) in the forespore. Among the possible factors contributing to the compartment specificity of sigma(E) and sigma(F) is the selective accumulation of the sigma(E) protein in the mother cell and that of SpoIIE, a regulatory phosphatase essential to the activation of sigma(F), in the forespore. In the current work, fluorescent microscopy is used to investigate the contributions of sigma(E) and SpoIIE's protein structures, expression and the genetic asymmetry that develops during chromosome translocation into the forespore on their abundance in each compartment. Time of entry of the spoIIE and sigE genes into the forespore was found to have a significant effect on the enrichment of their products in one or the other compartment. In contrast, the structures of the proteins themselves do not appear to promote their transfer to a particular compartment, but nonetheless contribute to compartmentalization by facilitating degradation in the compartment where each protein's activity would be inappropriate.

Bacillus subtilis↗
PubMed2005

Differential targeting of GSH1 and GSH2 is achieved by multiple transcription initiation: implications for the compartmentation of glutathione biosynthesis in the Brassicaceae.

The genome of Arabidopsis thaliana reveals that in this species the enzymes of glutathione biosynthesis, GSH1 and GSH2, are encoded by single genes. In silico analysis predicts proteins with putative plastidic transit peptides (TP) for both genes, but this has not been experimentally verified. Here we report a detailed analysis of the 5'ends of GSH1 and GSH2 mRNAs and demonstrate the subcellular targeting of the proteins encoded by different transcript types. GSH1 transcript analysis revealed two mRNA populations with short and long 5'-UTRs, respectively, both including the entire TP sequence. The ratio of long/total GSH1 transcripts was subject to developmental regulation. Transient transformation experiments with reporter gene fusions, bearing long or short 5'-UTRs, indicated an exclusive targeting of GSH1 to the plastids. Corroborating these results, endogenous and ectopically expressed GSH1 proteins were always present as a single polypeptide species with the size expected for correctly processed GSH1. Finally, the plastidic GSH1 localization was confirmed by immunocytochemistry. Similar to GSH1, multiple transcript populations were found for GSH2. However, here the prevalent shorter transcripts lacked a complete TP sequence. As expected, the large (but less abundant) transcript encoded a plastidic GSH2 protein, whereas GSH2 synthesized from the shorter transcript was targeted to the cytosol. The implications of the results for the compartmentation and regulation of GSH synthesis are discussed.

5' Flanking Region↗
PubMed1980

Regulation of compartmentation of amino acid pools in Saccharomyces cerevisiae and its effects on metabolic control.

Compartmentation of intracellular amino acid pools has been studied under various growth conditions in wild-type strains as well as in mutants. Aspartate, glutamate, leucine and isoleucine pools are present in high concentrations in the cytoplasm, while all the other amino acids are more vacuolar. The nature of the nitrogen source for growth, the effectiveness of nitrogen assimilation, the rate of protein synthesis and the presence of high internal basic amino acid pools are important factors in the repartition of amino acid pools between the cytoplasm and the vacuole.

Amino Acids↗
PubMed1995

Spatial compartmentation and time resolution of photooxidation of a cell membrane probe in electropermeabilized Chinese hamster ovary cells.

When electropulsed by short strong electric field pulses, cells can be permeabilized transiently (electropermeabilization). The transient electroinduced membrane restructuration which supports enhanced membrane permeability is topologically well defined on the surface of the cell. Exchange of polar species only takes place on the part of the cell surface which is controlled by the field intensity. Electropermeabilization is a stress for the cell and metabolic responses associated with this stress must be studied. A key point is to discover whether this stress affects the whole cell surface or especially the permeabilized part. This was investigated by photochemical time-dependent methodology. Analysis of the photooxidation reaction of 5-(N-hexadecanoyl)-aminofluorescein, an interfacial light-sensitive fluorescent probe, inserted into the Chinese hamster ovary cell membrane showed that the rate of reaction was accelerated when the cell population was electropermeabilized. This increase in the rate constant depended on the field strength. A theoretical approach suggested that modulation of the photooxidation reaction was restricted to the electropermeabilized part of the cell surface. The difference of reactivity could be correlated with an activator effect of oxygen-reactive species generated by an electro-induced oxidative jump and suggested that these species were localized in the permeabilized part of the plasma membrane. Using fluorescence digitized videomicroscopy imaging on a single cell, such spatial heterogeneity of the photooxidation reaction was indeed directly observed when the cell was electropermeabilized. There was heterogeneous compartmentation of the membrane reaction into two independent domains with specific reactivity. The direct observation is that long-lived electropermeabilization only affects a restricted part of the pulsed cell surface, from both a structural and a metabolic point of view.

Animals↗
PubMed1989

Does mitochondrial compartmentation of CO2 exist in man?

A comparison was made between the specific radioactivity of urea, and that of CO2 in breath, in urine and in arterialized blood, during a 36-h continuous infusion of 0.5 mCi and 100 mmol of sodium bicarbonate (NaH14CO3) into six normal male volunteers. After a period of equilibration, the mean specific radioactivity of urea was found to be only 16% below that of end expiratory CO2 and a similar amount below that of CO2 both in arterialized blood and in urine. This difference may be explained by isotopic dilution of 14CO2 by metabolic CO2 produced in the splanchnic tissues. It is concluded that, in these normal subjects, there is little or no compartmentation between cytosolic CO2 and the mitochondrial CO2 used for urea synthesis.

Adult↗
PubMedDate not supplied

Hydrolase compartmentalization limits rate of digestion in Acanthamoeba.

The kinetics of lysosomal enzyme acquisition by newly formed phagosomes was studied by following the rate of digestion of radiolabeled yeast fed to Acanthamoeba. The distribution of hydrolases among phagosomes was assessed by electron microscopic acid phosphatase cytochemistry and by measurement of three glycosidases in isolated early and late phagosomes. The results show that compartmentalization of hydrolases limit the digestion of large phagocytic loads. The hydrolases appear to be sequestered into the early phagosomes and not to be distributed either by small vesicle transport or phagosome-phagosome fusion to those formed later. We infer from these results that newly internalized surface membrane in phagosomes is not rapidly randomized with internal pools, but is recycled to the surface as a function of the digestive process.

Acanthamoeba↗
PubMed1993

Accumulation and intracellular compartmentation of lithium ions in Saccharomyces cerevisiae.

Accumulation of Li+ in Saccharomyces cerevisiae X2180-1B occurred via an apparent stoichiometric relationship of 1:1 (K+/Li+) when S. cerevisiae was incubated in the presence of 5 and 10 mM LiCl for 3 h. Other cellular cations (Mg2+, Ca2+ and Na+) did not vary on Li+ accumulation, although lithium chemistry dictates a degree of similarity to Group I and II metal cations. Compartmentation of Li+ was mainly in the vacuole which accounted for 85% of the Li+ accumulated after a 6-h incubation period. The remainder was located in the cytosol with negligible amounts being bound to cell fragments including the cell wall. Transmission electron microscopy of Li(+)-loaded cells revealed enlarged vacuoles compared with control cells. This asymmetric cellular distribution may therefore enhance tolerance of S. cerevisiae to Li+ and ensure that essential metabolic processes in the cytosol are not disrupted.

Cell Compartmentation↗
PubMed2003

Listeria monocytogenes mutants that fail to compartmentalize listerolysin O activity are cytotoxic, avirulent, and unable to evade host extracellular defenses.

Listeria monocytogenes is a facultative intracellular bacterial pathogen that escapes from a phagosome and grows in the host cell cytosol. Escape of the bacterium from the phagosome to the cytosol is mediated by the bacterial pore-forming protein listeriolysin O (LLO). LLO has multiple mechanisms that optimize activity in the phagosome and minimize activity in the host cytosol. Mutants that fail to compartmentalize LLO activity are cytotoxic and have reduced virulence. We sought to determine why cytotoxic bacteria have attenuated virulence in the mouse model of listeriosis. In this study, we constructed a series of strains with mutations in LLO and with various degrees of cytotoxicity. We found that the more cytotoxic the strain in cell culture, the less virulent it was in mice. Induction of neutropenia increased the relative virulence of the cytotoxic strains 100-fold in the spleen and 10-fold in the liver. The virulence defect was partially restored in neutropenic mice by adding gentamicin, an antibiotic that kills extracellular bacteria. Additionally, L. monocytogenes grew more slowly in extracellular fluid (mouse serum) than within tissue culture cells. We concluded that L. monocytogenes controls the cytolytic activity of LLO to maintain its nutritionally rich intracellular niche and avoid extracellular defenses of the host.

Animals↗
PubMed1979

Alterations of deoxyribonucleoside triphosphate pools in Escherichia coli: effects on deoxyribonucleic acid replication and evidence for compartmentation.

Inhibition of ribonucleic acid synthesis in Escherichia coli 15 TAU bar with rifampin or streptolydigin leads to large increases in the sizes of cellular ribonucleoside and deoxyribonucleoside triphosphate pools. Inhibition of protein synthesis leads to increases in the sizes of all nucleoside triphosphate pools except the guanosine triphosphate and deoxyguanosine triphosphate pools; a decrease in the size of the latter pool may be responsible for the slowing of deoxyribonucleic acid replication fork movement observed in this strain in the absence of protein synthesis. Analysis of the kinetics of incorporation of labeled precursors into deoxyribonucleic acid and into cellular pools suggests that functional compartmentation of nucleotide pools exists, allowing the incorporation of exogenously supplied precursors into deoxyribonucleic acid without prior equilibration with the cellular pools.

Bacterial Proteins↗
PubMed1981

Subcellular compartmentation in control of converging pathways for proline and arginine metabolism in Saccharomyces cerevisiae.

Enzymes of proline biosynthesis and proline degradation which act on the same compound, delta 1-pyrroline-5-carboxylate, are physically separated in yeast cells. The enzyme responsible for the final step in proline biosynthesis, pyrroline-5-carboxylate reductase, converts pyrroline-5-carboxylate to proline and is located in the cytoplasm. The last enzyme in the proline degradative pathway, pyrroline-5-carboxylate dehydrogenase, converts pyrroline-5-carboxylate to glutamate and is found in the particulate fraction of the cell, presumably in the mitochondrion. By subcellular compartmentation, yeast cells avoid futile cycling between proline and pyrroline-5-carboxylate.

1-Pyrroline-5-Carboxylate Dehydrogenase↗
PubMed2001

Hydrogen peroxide fluxes and compartmentalization inside growing Escherichia coli.

Escherichia coli generates about 14 microM hydrogen peroxide (H(2)O(2)) per s when it grows exponentially in glucose medium. The steady-state intracellular concentration of H(2)O(2) depends on the rates at which this H(2)O(2) is dissipated by scavenging enzymes and by efflux from the cell. The rates of H(2)O(2) degradation by the two major scavenging enzymes, alkyl hydroperoxide reductase and catalase, were quantified. In order to estimate the rate of efflux, the permeability coefficient of membranes for H(2)O(2) was determined. The coefficient is 1.6 x 10(-3) cm/s, indicating that permeability is substantial but not unlimited. These data allowed internal H(2)O(2) fluxes and concentrations to be calculated. Under these growth conditions, Ahp scavenges the majority of the endogenous H(2)O(2), with a small fraction degraded by catalase and virtually none persisting long enough to penetrate the membrane and exit the cell. The robust scavenging activity maintains the H(2)O(2) concentration inside glucose-grown cells at <10(-7) M, substantially below the level (10(-6) M) at which toxicity is evident. When extracellular H(2)O(2) is present, its flux into the cell can be rapid, but the internal concentration may still be an order of magnitude lower than that outside. The presence of such gradients was confirmed in experiments that revealed different degrees of oxidative stress in cocultured scavenger-deficient mutants. The limited permeability of membranes to H(2)O(2) rationalizes the compartmentalization of scavenging systems and predicts that bacteria that excrete redox-cycling drugs do not experience the same H(2)O(2) dose that they impose on their competitors.

Bacterial Proteins↗
PubMed2004

Compartmentalization of VP16 in cells infected with recombinant herpes simplex virus expressing VP16-green fluorescent protein fusion proteins.

VP16 is an essential structural protein of herpes simplex virus. It plays important roles in immediate-early transcriptional regulation, in the modulation of the activities of other viral components, and in the pathway of assembly and egress of infectious virions. To gain further insight into the compartmentalization of this multifunctional protein we constructed and characterized recombinant viruses expressing VP16 linked to the green fluorescent protein (GFP). These viruses replicate with virtually normal kinetics and yields and incorporate the fusion protein into the virion, resulting in autofluorescent particles. De novo-synthesized VP16-GFP was first detected in a diffuse pattern within the nucleus. Nuclear VP16-GFP was progressively recruited to replication compartments, which coalesced into large globular domains. By 10 to 12 h after infection additional distinct foci containing VP16-GFP could be seen, almost exclusively located at the periphery of the replication compartments. At the same time pronounced accumulation was observed in the cytoplasm, first in a diffuse pattern and then accumulating in vesicle-like compartments which were concentrated in an asymmetric fashion reminiscent of the Golgi. Inhibition of DNA replication resulted in prolonged diffuse nuclear distribution with minimal cytoplasmic accumulation. Treatment with brefeldin disrupted the cytoplasm vesicular pattern, resulting in redistributed large foci. Time-lapse microscopy demonstrated various dynamic features of infection, including the active induction of very long cellular projections (up to 100 microM). Vesicular clusters containing VP16 were transported within projections to the termini, which developed bulbous ends and appeared to embed into the membranes of adjacent uninfected cells.

Active Transport, Cell Nucleus↗