Showing papers on "Cellular compartment published in 1998"
TL;DR: In the brain, the principal compartment in which A beta resides is a detergent-insoluble glycolipid-enriched membrane domain (DIG) as mentioned in this paper.
Abstract: Ordered assembly of the amyloid-beta protein (A beta) into amyloid fibrils is a critical step in Alzheimer's disease (AD). To release the amyloidogenic peptide A beta from the Alzheimer amyloid precursor protein (APP), two secretases act sequentially: first, beta-secretase cleaves close to the membrane within the ectodomain and then gamma-secretase cuts within the transmembrane domain. The sites of gamma-secretase cleavage are after residues 40 or 42 of A beta. Except in those rare cases of AD caused by a mutation, levels of secreted A beta are not elevated; thus, the secretory pathway may be unaffected, and factors other than the extracellular concentration of A beta may contribute to the aggregation properties of the peptide. A beta is also present in intracellular compartments. The two gamma-secretase cleavage products, A beta42 and A beta40, were found in different compartments: A beta42 in the endoplasmic reticulum (ER)/intermediate compartment, and A beta40 in the trans-Golgi network (TGN). The cellular compartments that harbor A beta are target sites for therapeutic intervention. Here we report that in the brain, the principal compartment in which A beta resides is a detergent-insoluble glycolipid-enriched membrane domain (DIG). Also present in the DIG fractions are the endoproteolytic fragments of presenilin-1 (PS1) and APP. The presence of these proteins, which all contribute to the generation of A beta, indicates that the DIG fraction is probably where the intramembranous cleavage of APP occurs.
385 citations
TL;DR: It has been demonstrated that ER retention is essential for the accumulation of sufficient scFv to bind high concentrations of ABA in the transgenic seeds and seed-specific expression of high amounts of anti-ABA-scFv's at a defined time of seed-development induced a developmental switch from seed ripening to vegetative growth.
Abstract: Expression and stability of immunoglobulins in transgenic plants have been investigated and optimized by accumulation in different cellular compartments as cytosol, apoplastic space and endoplasmic reticulum (ER) as will be discussed in this review. In several cases described the highest accumulation of complete active antibodies was achieved by targeting into the apoplastic space. High-level expression of active recombinant single-chain Fv antibodies (scFv's) was obtained by retention of these proteins in the lumen of the endoplasmic reticulum. This has been shown for leaves and seeds of transgenic tobacco as well as for potato tubers. Transgenic tobacco seeds, potato tubers and tobacco leaves can facilitate stable storage of scFv's accumulated in the ER over an extended (seeds, tubers) or a short (leaves) period of time. The expression of specific scFv's in different plant species, plant organs and cellular compartments offers the possibility of blocking regulatory factors or pathogens specifically. Examples are scFv's expressed in the cytosol and the apoplastic space of transgenic plant cells modulating the infection process of plant viruses and a cytosolically expressed scFv that influenced the activity of phytochrome A protein. The immunomodulation approach has been shown to be also applicable for investigating the action of the phyto-hormone abscisic acid (ABA). High-level accumulation of specific anti-ABA scFv's in the ER of all leaf cells has been used to block the influence of ABA on the stomatal functions. Seed-specific expression of high amounts of anti-ABA-scFv's at a defined time of seed-development induced a developmental switch from seed ripening to vegetative growth. It has been demonstrated that ER retention is essential for the accumulation of sufficient scFv to bind high concentrations of ABA in the transgenic seeds.
356 citations
Journal Article•
TL;DR: The results suggest that although pharmacokinetic parameters vary as a function of hepatic cell type, significant intracellular delivery can be readily achieved in the liver after systemic administration.
Abstract: In the rat, the liver represents a major site of phosphorothioate oligodeoxynucleotide deposition after i.v. administration. For this reason, we examined the intracellular fate of ISIS 1082, a 21-base heterosequence phosphorothioate oligodeoxynucleotide, isolated from parenchymal and nonparenchymal cell types after systemic dosing using established perfusion and separation techniques followed by CGE. Isolated cells were further fractionated into nuclear, cytosolic and membrane constituents to assess the intracellular localization, distribution and metabolic profiles as a function of time and dose. After a 10-mg/kg i.v. bolus, intracellular drug levels where maximal after 8 hr and diminished significantly thereafter, suggesting an active efflux mechanism or metabolism. Nonparenchymal (i.e., Kupffer and endothelial) cells contained approximately 80% of the total organ cellular dose, and this was equivalently distributed between the two cell types, while the remaining 20% was associated with hepatocytes. Nonparenchymal cells contained abundant nuclear, cytosolic and membrane drug levels over a wide dose range. In contrast, at doses of less than 25 mg/kg, hepatocytes contained significantly less drug with no detectable nuclear-association. Doses at or above 25 mg/kg appeared to saturate nonparenchymal cell types, whereas hepatocytes continued to accumulate drug in all cellular compartments, including the nucleus. Our results suggest that although pharmacokinetic parameters vary as a function of hepatic cell type, significant intracellular delivery can be readily achieved in the liver after systemic administration.
135 citations
TL;DR: These observations suggest that trophozoites of G. lamblia present an endosomal-lysosomal system concentrated in a single system, the peripheral vesicles, which may represent an ancient organellar system that later on subdivided into compartments such as early and late endosomes and lysosomes.
80 citations
TL;DR: In this review, it is clear that two-way traffic occurs, involving not only movement of molecules from the cytosol into the lumen of the ER but also out of theLumen into the cytOSol.
78 citations
TL;DR: It is suggested that the 45-kDa glycoprotein migrates from ER to mitochondria by the previously observed contact sites between the two organelles and would be consistent with a role in mitochondrial translocations.
70 citations
TL;DR: Observations suggest a subset of peroxisomal membrane proteins might be targeted first to the endoplasmic reticulum, and from there toperoxisomes by vesicle-mediated transport.
60 citations
TL;DR: Loligomers are multitasking, peptide-based shuttles that are able to penetrate cells and self-localize into distinct cellular compartments and provide a simple synthetic platform for the design of guided intracellular agents.
Abstract: Loligomers are multitasking, peptide-based shuttles that are able to penetrate cells and self-localize into distinct cellular compartments. In particular, loligomer 4 incorporates internalization and nuclear import sequences as well as reporter groups. The intracellular routing of loligomer 4 was analyzed by microscopy and flow cytometry, to define and demonstrate localization events. Electron micrographs of CHO cells exposed to a biotinylated derivative of loligomer 4 as well as confocal images of CHO cells treated with rhodamine-labeled loligomer 4 indicate their presence in the cytosol, endocytic vesicles, and the nucleus of CHO cells. Loligomer 4 accumulates irreversibly inside cells. Uptake of loligomer 4 by six mammalian cell lines (Daudi, EL4, CHO, COS-7, VERO, and HeLa) was proven by flow cytometry, establishing the generality of the principle. Cells presented as monolayers typically were less able to endocytose the construct than cells grown in suspension. Cellular accumulation of loligomer 4 varied between cell lines with COS-7 and VERO cells showing the highest level of uptake. Plasmids harboring reporter genes could be transported efficiently inside CHO cells, suggesting that loligomer 4 either alone or noncovalently associated with large macromolecules can effectively reach the nucleus of cells. In summary, loligomer 4 constructs provide a simple synthetic platform for the design of guided intracellular agents.
41 citations
TL;DR: In the marine snail Aplysia californica as mentioned in this paper, the ink-release vesicles were found to be cholinergic, and 70% of isolated vesicle cells were induced to squeeze ink from their valved end by solutions of acetylcholine at concentrations of 0.5 mmol l-1 or below.
Abstract: The marine snail Aplysia californica obtains its defensive ink exclusively from a diet of red seaweed. It stores the pigment (phycoerythrobilin, the red algal photosynthetic pigment, r-phycoerythrin, minus its protein) in muscular ink-release vesicles within the ink gland. Snails fed a diet of green seaweed or romaine lettuce do not secrete ink and their ink-release vesicles are largely devoid of ink. Successive activation of individual ink-release vesicles by ink motor neurons causes them to secrete approximately 55 % of their remaining ink (similar to the percentage of ink reserves released from the intact gland). The peripheral activation of vesicles appears to be cholinergic: 70 % of isolated vesicles were induced to squeeze ink from their valved end by solutions of acetylcholine at concentrations of 0.5 mmol l-1 or below. Ultrastructural analysis commonly found three cell types in the ink gland. The RER cells, the most numerous, were characterized by an extensive rough endoplasmic reticulum with greatly distended cisternae. This cell type is probably the site for synthesis of the high molecular mass protein of secreted ink. The granulate cells, less common than RER cells, had nuclear and cell areas significantly larger than those of RER cells. In addition, granulate cells of red-algal-fed snails had 4-14 vacuoles that contained electron-dense material with staining characteristics similar to that of ink in mature ink-release vesicles. The granulate cell's plasma membrane was regularly modified into grated areas, which both localized and expanded the surface area for coated vesicle formation and provided a sieve structure that prevented large particles in the hemolymph either from being taken up by, or from occluding, the coated vesicles. Electron-dense particles within coated vesicles were similar in size to those in granulate vacuoles but larger (on average by approximately 1 nm) than those that make up the ink. In green-seaweed-fed snails, granulate cells and their vacuoles were present but the vacuoles were empty. The third cell type, the vesicle cell, expands markedly, with its nucleus enlarging concurrent with cell growth until it is on average 50 times larger in cross-sectional area than the nuclei of either RER or granulate cells; the cytoplasm eventually becomes filled with ink, which obscures the mitochondria, vacuoles and nucleus. Continued cell expansion ceases with the appearance of an encircling layer of muscle and 1-3 layers of cells of unknown origin, thereby becoming the ink-release vesicle itself. The absorption spectra of the soluble contents of mature ink-release vesicles from snails fed red algae had peaks characteristic of the red algal pigment r-phycoerythrin or/and phycoerythrobilin. Immunogold localization of r-phycoerythrin showed no statistical difference in the amount of label within the ink-release vesicles, RER or granulate cell types. Furthermore, there was no localization of phycoerythrin immunoreactivity within the various cellular compartments of either the RER or granulate cells (nucleus, endoplasmic reticulum, mitochondria, vacuoles). Immunogold labeling in the ink gland ranged from 11 to 16 % of that for the digestive vacuoles of the rhodoplast digestive cells lining the tubules of the digestive gland. Our observations suggest (a) that the main form of the ink pigment in the gland is phycoerythrobilin or/and a non-antigenic form of phycoerythrin, and (b) that separation of the bilin from phycoerythrin (or its modification so that it is no longer antigenic) occurs before it reaches the ink gland, probably within the vacuoles of the rhodoplast digestive cells of the digestive gland. We propose the following model. The ink pigment, phycoerythrobilin, is cleaved from its protein in rhodoplast digestive vacuoles in the digestive gland. (ABSTRACT TRUNCATED)
39 citations
TL;DR: β1a and β2a are differentially distributed in tsA201 cells and upon coexpression with α1S, formα1S·β complexes in different cellular compartments, which requires the intact β interaction domain in the I-II cytoplasmic loop of β1S.
37 citations
TL;DR: The communication between spatially distant cellular compartments is envisioned as a bidirectional flow of information based on subtle multilevel structural and biochemical equilibria that is mediated by the interaction between structural signal transducers and their binding partners.
Abstract: Understanding how the information is conveyed from outside to inside the cell is a critical challenge for all biologists involved in signal transduction. The flow of information initiated by cell-cell and cell-extracellular matrix contacts is mediated by the formation of adhesion complexes involving multiple proteins. Inside adhesion complexes, connective membrane skeleton (CMS) proteins are signal transducers that bind to adhesion molecules, organize the cytoskeleton, and initiate biochemical cascades. Adhesion complex-mediated signal transduction ultimately directs the formation of supramolecular structures in the cell nucleus, as illustrated by the establishment of multi complexes of DNA-bound transcription factors, and the redistribution of nuclear structural proteins to form nuclear subdomains. Recently, several CMS proteins have been observed to travel to the cell nucleus, suggesting a distinctive role for these proteins in signal transduction. This review focuses on the nuclear translocation of structural signal transducers of the membrane skeleton and also extends our analysis to possible translocation of resident nuclear proteins to the membrane skeleton. This leads us to envision the communication between spatially distant cellular compartments (i.e., membrane skeleton and cell nucleus) as a bidirectional flow of information (a dynamic reciprocity) based on subtle multilevel structural and biochemical equilibria. At one level, it is mediated by the interaction between structural signal transducers and their binding partners, at another level it may be mediated by the balance and integration of signal transducers in different cellular compartments.
TL;DR: Certain protein toxins act by catalytically modifying substrates in the cytosol of mammalian cells to reach this compartment, and undergo retrograde transport from the cell surface, via the Golgi complex, to the endoplasmic reticulum.
01 Jan 1998
TL;DR: The ER, normally low in intracellular cholesterol, has the capacity to act as a sink for endocytosed cholesterol when esterification is blocked and appears to enhance the induction of cellular homeostatic responses.
Abstract: Insight into the effect of exogeneously derived lipoprotein cholesterol on distribution of intracellular membrane cholesterol has been gained from structural studies on normal and Niemann Pick Type C human fibroblasts. Endocytic uptake of LDL enriches Golgi cholesterol in both normal and NPC cells. However, the NPC mutation and treatment of normal cells with progesterone during LDL uptake produces abnormal accumulation of cholesterol in lysosomes and trans Golgi cisternae. This lysosomal/Golgi block in cholesterol trafficking results in the inability of endocytosed cholesterol to induce cellular homestatic responses. In addition to lysosomes and Golgi the endoplasmic reticulum can also be a site along the intracellular cholesterol transport pathway that becomes a temporary depot for cholesterol. Specific inhibition of acyl CoA: cholesterol acyltransferase with S-58035 during endocytic uptake results in a reversable accumulation of cholesterol in membranes of ER. Thus the ER, normally low in intracellular cholesterol, has the capacity to act as a sink for endocytosed cholesterol when esterification is blocked. In contrast to the lysosomal/Golgi cholesterol sequestration, ER accumulation of cholesterol does not compromise but appears to enhance the induction of cellular homeostatic responses.
TL;DR: It has been suggested that this mechanism drives both the cell enlargement and the vesicle budding that may be associated with the dynamic flow of membranes along the endoplasmic reticulum-vesicle-Golgi apparatus-plasma membrane pathway.
Abstract: Cell-free systems for the analysis of Golgi apparatus membrane traffic rely either on highly purified cell fractions or analysis by specific trafficking markers or both. Our work has employed a cell-free transfer system from rat liver based on purified fractions. Transfer of any constituent present in the donor fraction that can be labeled (protein, phospholipid, neutral lipid, sterol, or glycoconjugate) may be investigated in a manner not requiring a processing assay. Transition vesicles were purified and Golgi apparatus cisternae were subfractionated by means of preparative free-flow electrophoresis. Using these transition vesicles and Golgi apparatus subfractions, transfer between transitional endoplasmic reticulum and cis Golgi apparatus was investigated and the process subdivided into vesicle formation and vesicle fusion steps. In liver, vesicle formation exhibited both ATP-independent and ATP-dependent components whereas vesicle fusion was ATP-independent. The ATP-dependent component of transfer was donor and acceptor specific and appeared to be largely unidirectional, i.e., ATP-dependent retrograde (cis Golgi apparatus to transitional endoplasmic reticulum) traffic was not observed. ATP-dependent transfer in the liver system and coatomer-driven ATP-independent transfer in more refined yeast and cultured cell systems are compared and discussed in regard to the liver system. A model mechanism developed for ATP-dependent budding is proposed where a retinol-stimulated and brefeldin A-inhibited NADH protein disulfide oxidoreductase (NADH oxidase) with protein disulfide-thiol interchange activity and an ATP-requiring protein capable of driving physical membrane displacement are involved. It has been suggested that this mechanism drives both the cell enlargement and the vesicle budding that may be associated with the dynamic flow of membranes along the endoplasmic reticulum-vesicle-Golgi apparatus-plasma membrane pathway.
01 Jan 1998
TL;DR: These experiments showed clearly that a specific antibody/antigen interaction was possible in eukaryotic cells.
Abstract: Antibodies are heterodimers that specifically bind to a target molecule (anti-gen). Their ability to interfere with antigen function or synthesis make them useful tools for the in situ analysis of intracellular molecules. Antibodies can be directly introduced into the cell or they can be expressed from their genes in a specific cellular compartment where they will bind their target. The introduction of antibodies intracellularly was first successfully achieved by micro injection (in the cytoplasm or in the nucleus)1 or more recently, by electroporation.2 The specific (but transient) effects that were obtained by these methods opened the way to a large number of applications. Expression was also obtained by injection of poly A+ mRNA purified from a hybridoma secreting an antibody of interest in xenopus oocytes.3 For example, an anti-golgi protein antibody mRNA was able to inhibit the intracellular trafficking of a viral protein.4 These experiments showed clearly that a specific antibody/antigen interaction was possible in eukaryotic cells.
TL;DR: By means of confocal laser scanning microscopy, the glucocorticod receptor (GR) and thyroid hormone receptor (TR) are localized both in the nucleus and cytoplasm of two human cells lines (Hela, Hep-2).