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PubMed1995

Nuclear matrix proteins as structural and functional components of the mitotic apparatus.

The eukaryotic nucleus is a membrane-enclosed compartment containing the genome and associated organelles supported by a complex matrix of nonhistone proteins. Identified as the nuclear matrix, this component maintains spatial order and provides the structural framework needed for DNA replication, RNA synthesis and processing, nuclear transport, and steroid hormone action. During mitosis, the nucleoskeleton and associated chromatin is efficiently dismantled, packaged, partitioned, and subsequently reassembled into daughter nuclei. The dramatic dissolution of the nucleus is accompanied by the assembly of a mitotic apparatus required to facilitate the complex events associated with nuclear division. Until recently, little was known about the fate or disposition of nuclear matrix proteins during mitosis. The availability of specific molecular probes and imaging techniques, including confocal microscopy and improved immunoelectron microscopy using resinless sections and related procedures, has enabled investigators to identify and map the distribution of nuclear matrix proteins throughout the cell cycle. This chapter will review the structure, function, and distribution of the protein NuMA (nuclear matrix mitotic apparatus) and other nuclear matrix proteins that depart the nucleus during the interphase/mitosis transition to become structural and functional components within specific domains of the mitotic apparatus.

Animals↗
PubMed2000

CPEB, maskin, and cyclin B1 mRNA at the mitotic apparatus: implications for local translational control of cell division.

In Xenopus development, the expression of several maternal mRNAs is regulated by cytoplasmic polyadenylation. CPEB and maskin, two factors that control polyadenylation-induced translation are present on the mitotic apparatus of animal pole blastomeres in embryos. Cyclin B1 protein and mRNA, whose translation is regulated by polyadenylation, are colocalized with CPEB and maskin. CPEB interacts with microtubules and is involved in the localization of cyclin B1 mRNA to the mitotic apparatus. Agents that disrupt polyadenylation-induced translation inhibit cell division and promote spindle and centrosome defects in injected embryos. Two of these agents inhibit the synthesis of cyclin B1 protein and one, which has little effect on this process, disrupts the localization of cyclin B1 mRNA and protein. These data suggest that CPEB-regulated mRNA translation is important for the integrity of the mitotic apparatus and for cell division.

Animals↗
PubMed1998

The plant Golgi apparatus.

The plant Golgi apparatus has an important role in protein glycosylation and sorting, but is also a major biosynthetic organelle that synthesises large quantities of cell wall polysaccharides. This is reflected in the organisation of the Golgi apparatus as numerous individual stacks of cisternae that are dispersed through the cell. Each stack is polarised: the shape of the cisternae and the staining of the membranes change in a cis to trans direction, and the cisternae on the trans side contain more polysaccharides. Numerous glycosyltransferases are required for the synthesis of the complex cell wall polysaccharides. Microscopy and biochemical fractionation studies suggest that these enzymes are compartmentalised within the stack. Although there is no obvious cis Golgi network, the trans-most cisterna or trans Golgi network often buds clathrin-coated and sometimes smooth dense vesicles as well. Here, vacuolar proteins are sorted from the secreted proteins and polysaccharides. This review highlights unique aspects of the organisation and function of the plant Golgi apparatus. Fundamentally similar processes probably underlie Golgi organisation in all organisms, and consideration of the plant Golgi specialisations can therefore be generally informative, as well as being of central importance to plant cell biology.

Animals↗
PubMed2002

Glyceraldehyde-3-phospate dehydrogenase is translocated into nuclei through Golgi apparatus during apoptosis induced by 6-hydroxydopamine in human dopaminergic SH-SY5Y cells.

6-Hydroxydopamine is a neurotoxin specific to dopamine neurons, and this neurotoxin at 20 muM was confirmed to induce mainly apoptosis in human dopaminergic neuroblastoma SH-SY5Y cells. During the apoptotic process, translocation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) into nuclei was observed, which is now proposed as an apoptogenic signal in various types of apoptosis. However, it remains to be clarified, how GAPDH is translocated into nuclei. In this paper, GAPDH translocation was followed by fluoro- and electron-microscopic observation using antibody against GAPDH. Before the nuclear translocation, a condensed mass of GAPDH protein was detected in the Golgi apparatus, which was identified by 6-([N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]hexanoyl)-sphingosine, a selective marker of Golgi apparatus. These results suggest that the Golgi apparatus may be involved in the compartmentalization of GAPDH from cytosol to nuclei.

Active Transport, Cell Nucleus↗
PubMed1998

Environmental factors modulate the size and the secretory activity of the notochord. A study of the Golgi apparatus in avian embryos.

In this study we examined the Golgi apparatus of avian notochord transplants excised from 2-day-old (E2) chick embryos and grafted isochronically into a chick host either in a medial-ventral position, next to the host notochord, or in a superficial position under the ectoderm laterally or dorsally to the neural tube. The operated embryos were examined from E2 to E8. The diameters, the cytoplasmic vacuolization and the immunostained Golgi apparatus were identical between the endogenous and ventrally grafted notochords, as well as between host and superficially transplanted notochords when observed at E2. In contrast, from E4 to E8, the size of the notochords grafted dorsally or laterally to the neural tube significantly smaller than the host, while the cytoplasmic vacuolization and the degree of fragmentation of the Golgi apparatus were significantly less than in the host notochords. These results show that environmental and position-specific factors influence the developmental program and the secretory activity of the notochordal cells.

Animals↗
PubMed2003

Cytokinesis: relative alignment of the cell division apparatus and the mitotic spindle.

The cell division apparatus is assembled at different stages of the cell cycle in different eukaryotic organisms. Mechanisms exist in all organisms, however, to ensure that the cell division apparatus and the mitotic spindle are aligned perpendicular to each other. Such an alignment ensures that each daughter cell receives a nucleus and that the cell division apparatus does not cleave and destroy the genetic material. The interaction(s) of astral microtubules with the cell cortex appears to play an important role in establishing perpendicularity between chromosome segregation and cell division machinery.

Animals↗
PubMed1998

The Golgi apparatus: 100 years of progress and controversy.

Research on the Golgi apparatus has resulted in major advances in understanding its structure and functions, but many important questions remain unanswered. The history of the Golgi apparatus has been marked by arguments and controversies, some of which have been resolved, whereas others are still ongoing. This article charts progress in understanding the role of the Golgi apparatus during the 100 years since it was discovered, highlighting major milestones and discoveries that have led to the concepts of the organization and functions of this organelle that we have today.

Animals↗
PubMed1991

Localization in the Golgi apparatus of rat liver UDP-Gal:glucosylceramide beta 1----4galactosyltransferase.

The presence and subcellular localization of UDP-Gal:glucosylceramide beta 1----4galactosyltransferase (GalT-2) was investigated in rat liver. For this purpose, purified Golgi apparatus, endoplasmic reticulum, and plasma membrane fractions were prepared from the liver and used as the enzyme source for detecting GalT-2. A pure Golgi apparatus, highly enriched in many glycosyltransferases, was the only fraction where GalT-2 was measurable. The reaction product formation rate under appropriate assay conditions, which requires high detergent concentration and Mn2+, was low but comparable with that of other glycosyltransferases. The product formation was stimulated by exogenously added acceptor GlcCer, donor UDP-Gal, and Golgi protein. The reaction product was a single spot that was identified by chromatographic behavior, sensitivity to beta-galactosidase, and permethylation studies as Gal beta 1----4Glc beta 1----1'Cer (lactosylceramide). A metabolic experiment, performed by determining the glycosphingolipids which became radioactive in the above subcellular fractions prepared from the liver of animals treated with glucose-labeled glucosylceramide, further indicated that the in vivo glycosylation of glucosylceramide takes place in the Golgi apparatus.

Animals↗
PubMed2002

The overexpression of GMAP-210 blocks anterograde and retrograde transport between the ER and the Golgi apparatus.

Golgi Microtubule-Associated Protein (GMAP)-210 is a peripheral coiled-coil protein associated with the cis-Golgi network that interacts with microtubule minus ends. GMAP-210 overexpression has previously been shown to perturb the microtubule network and to induce a dramatic enlargement and fragmentation of the Golgi apparatus (Infante C, Ramos-Morales F, Fedriani C, Bornens M, Rios RM. J Cell Biol 1999; 145: 83-98). We now report that overexpressing GMAP-210 blocks the anterograde transport of both a soluble form of alkaline phosphatase and the hemagglutinin protein of influenza virus, an integral membrane protein, between the endoplasmic reticulum and the cis/medial (mannosidase II-positive) Golgi compartment. Retrograde transport of the Shiga toxin B-subunit is also blocked between the Golgi apparatus and the endoplasmic reticulum. As a consequence, the B-subunit accumulates in compartments positive for GMAP-210. Ultrastructural analysis revealed that, under these conditions, the Golgi complex is totally disassembled and Golgi proteins as well as proteins of the intermediate compartment are found in vesicle clusters distributed throughout the cell. The role of GMAP-210 on membrane processes at the interface between the endoplasmic reticulum and the Golgi apparatus is discussed in the light of the property of this protein to bind CGN membranes and microtubules.

Alkaline Phosphatase↗
PubMed2003

Phospholipase Cgamma activates Ras on the Golgi apparatus by means of RasGRP1.

Ras proteins regulate cellular growth and differentiation, and are mutated in 30% of cancers. We have shown recently that Ras is activated on and transmits signals from the Golgi apparatus as well as the plasma membrane but the mechanism of compartmentalized signalling was not determined. Here we show that, in response to Src-dependent activation of phospholipase Cgamma1, the Ras guanine nucleotide exchange factor RasGRP1 translocated to the Golgi where it activated Ras. Whereas Ca(2+) positively regulated Ras on the Golgi apparatus through RasGRP1, the same second messenger negatively regulated Ras on the plasma membrane by means of the Ras GTPase-activating protein CAPRI. Ras activation after T-cell receptor stimulation in Jurkat cells, rich in RasGRP1, was limited to the Golgi apparatus through the action of CAPRI, demonstrating unambiguously a physiological role for Ras on Golgi. Activation of Ras on Golgi also induced differentiation of PC12 cells, transformed fibroblasts and mediated radioresistance. Thus, activation of Ras on Golgi has important biological consequences and proceeds through a pathway distinct from the one that activates Ras on the plasma membrane.

Animals↗
PubMed2003

Endoplasmic reticulum and Golgi apparatus are the preferential sites of Foscan localisation in cultured tumour cells.

Intracellular photosensitiser localisation significantly influences the mechanism of response to photodynamic therapy (PDT), since the primary sites of damage are closely related to the specific sensitiser distribution. Foscan subcellular localisation in the MCF-7 human adenocarcinoma cell line has been studied by means of confocal microscopy and microspectrofluorometry. The fluorescence topographic profiles recorded after cells costained with Foscan and organelle-specific fluorescent probes revealed that Foscan presents low localisation in lysosomes and a weak accumulation in mitochondria. Alternatively, the Foscan fluorescence topographic profile turned out to colocalise perfectly with that obtained for the endoplasmic reticulum (ER) and the Golgi apparatus. The patterns of fluorescence derived from confocal microscopy studies were consistent with predominant localisation of Foscan in these organelles. Furthermore, evaluation of enzymatic activity of selected organelles immediately after laser light irradiation (650 nm) indicated the Golgi apparatus and ER as the primary damaged sites resulting from Foscan-mediated PDT in the MCF-7 cell line. To our knowledge, this is the first study to demonstrate unambiguously that the ER and the Golgi apparatus are preferential sites of Foscan accumulation.

Antineoplastic Agents↗
PubMed2002

The bovine papillomavirus oncoprotein E5 retains MHC class I molecules in the Golgi apparatus and prevents their transport to the cell surface.

During papillomavirus infection, the E5 protein localizes in the cell Golgi apparatus and other endomembrane compartments. Cells transformed by E5 do not express major histocompatibility class I complex (MHC I) on the cell surface, while cells transformed by the other transforming proteins E6 and E7 do. In addition, the total amount of both MHC I protein and mRNA is reduced in E5-transformed cells. Here we show that expression of bovine papillomavirus E5 causes the retention of MHC I in the Golgi apparatus, thus preventing its transport to the cell surface. We ascribe this effect to a failure of acidification of the Golgi apparatus, as similar effects are observed in control cells treated with the ionophore monensin. Treatment of E5-transformed cells with either beta- or gamma-interferon increases the synthesis of MHC I, showing that inhibition of MHC I expression by E5 is not irreversible. However, even after interferon treatment, MHC I, although increased in quantity, is not transported to the cell surface. E5 therefore affects MHC I at several levels, but prevention of MHC I transport to the cell surface appears to be the dominant effect. Lack of surface MHC I would have profound consequences for presentation of viral peptides to the immune system.

Animals↗
PubMed1972

Lipoprotein particles from the Golgi apparatus of guinea-pig liver.

1. A cell fraction has been isolated from guinea-pig liver and shown to be rich in Golgi apparatus by electron microscopy. The activity of UDP-d-galactose-N-acetylglucosamine galactosyltransferase was over 100-fold greater in this cell fraction than in the liver homogenate. These data support the conclusion that the fraction was enriched in Golgi apparatus. 2. The Golgi cisternae and secretory vesicles contained electron-dense particles of 10-80nm diameter. Disruption of the Golgi apparatus cell fraction released these particles, which were separated into VLD (very-low-density) and LD (low-density) species on the basis of their density. 3. The Golgi VLD particles possessed morphological, flotational, chemical and immunochemical properties which closely resembled those of the serum VLD lipoproteins from the same animals. 4. The Golgi LD particles were rich in phospholipid, containing 48.1% by weight. The chemical composition of these particles was quite distinct from that of the serum LD lipoproteins, but did, however, show some similarity to that of the serum VLD lipoproteins. A marked resemblance was noted in the chemical characteristics of the Golgi LD and VLD particles (with the exception of triglyceride content). In addition, these two species of Golgi particles possessed the same antigenic determinant. 5. The results suggest that the Golgi VLD particles are the precursors of the serum VLD lipoproteins. On the basis of similarities in gross chemical composition and in the antigenic determinant of the Golgi LD and VLD particles, we conclude that the LD particles are probably the precursors of the VLD particles. In view of the marked differences in gross chemical composition of the Golgi LD particles and serum LD lipoproteins, it appears unlikely that the LD particles are directly secreted into the serum pool.

Animals↗
PubMed1973

The effect of a lipid-rich diet on the properties and composition of lipoprotein particles from the Golgi apparatus of guinea-pig liver.

1. A cell fraction rich in Golgi apparatus was isolated from the livers of guinea pigs fed on a lipid-rich diet (1.6% cholesterol, 15% corn oil). 2. The Golgi cisternae and secretory vesicles contained electron-dense particles which were tentatively identified as VLD (very-low-density) and LD (low-density) lipoproteins. Particles of moderate electron density, 150-500nm in diameter, were seen associated with membranous elements of the Golgi-apparatus cell fraction. Disruption of this cell fraction permitted the release of these three species of particles, which were separated into particulate lipid, and VLD and LD lipoproteins. 3. The large particles of moderate electron density, isolated as particulate lipid, were distinct from both species of Golgi particles in their chemical composition and in possessing an immunochemically unreactive apolipoprotein(s). Morphological observations suggest that the particulate lipid arose from cytoplasmic lipid droplets which were present as contaminants of the Golgi-rich fraction. 4. The chemical and immunochemical results are consistent with the suggestion that the Golgi LD particles are precursors of the VLD particles, into which they may be transformed by the addition of both triglyceride and cholesteryl ester. The present results provide further support for the proposal that the Golgi VLD particles are precursors of the serum VLD lipoproteins in the guinea pig. 5. Hepatic Golgi VLD particles isolated from guinea pigs fed on the lipid-rich diet contained significantly higher molar amounts (relative to protein) of both cholesteryl ester and triglyceride than similar particles from animals fed on a normal diet. These results suggest that the type of Golgi VLD particle produced from the LD particle is a direct consequence of the amount and composition of the dietary lipid. 6. Hepatic Golgi LD particles isolated from guinea pigs fed on different diets were similar in chemical composition and contained approx. 50% by weight of phospholipid. We conclude that the Golgi LD particle is normally present in the Golgi-apparatus cell fraction from guinea-pig liver, and may represent the end product of lipoprotein biosynthesis in the smooth endoplasmic reticulum. 7. The serum LD lipoproteins and Golgi LD particles were quite distinct in chemical composition. However, these two lipoprotein species were immunochemically identical and exhibited a similar range of flotation rate. It appears unlikely that the Golgi LD particles are secreted as the precursors of the serum LD lipoproteins.

Animals↗
PubMed1976

Isolation of a Golgi-apparatus-enriched fraction from leukaemic cells.

1. A Golgi-apparatus-enriched fraction was isolated from acute leukaemic lymphoblasts of AKR mice by using an homogenate stabilized with 1 mM-glutaraldehyde. 2. The isolated fraction, which was shown morphologically to be enriched in dictyosomes, possessed between 44- and 76-fold increase in specific activity, compared with the tumour homogenate, of UDP-galactose-glycoprotein galactosyltransferase and between 3- and10.5-fold increase in relative specific activity of UDP-N-acetygalactosamine-polypeptide N-acetylgalactosaminyltransferase. 3. Plasma membranes isolated from the leukaemic lymphoblasts also possessed glycoprotein galactosyltransferase activity, though in contrast with Golgi-apparatus-enriched material had no detectable polypeptide N-acetygalactosaminyltransferase. 4. The difficulties associated with maintaining the morphological integrity of the Golgi apparatus in subcellular fractionation are discussed.

Animals↗
PubMed1976

The effect of intralysosomal sucrose storage on the turnover of hamster fibroblast lysosomal and Golgi-apparatus enzymes.

1. The effect of overloading of hamster fibroblast lysosomes with sucrose on the turnover of lysosomal and Golgi-apparatus enzymes was studied. Arylsulphatase B and UDP-galactose-N-acetylglucosamine galactosyltransferase were chosen as appropriate marker enzymes. The relative contributions of changes in the rates of synthesis and degradation to the increased activities of these enzymes after uptake of sucrose were examined by isotopic-labelling experiments. The effects of sucrose uptake on the degradation of total cellular protein and of the cytoplasmic enzyme, alkaline ribonuclease, were determined for comparative purposes. 2. The rates of enzyme synthesis in the presence and absence of sucrose were compared by pulse-labelling the cells with 14C-labelled amino acids, followed by isolation of purified enzymes and determination of their radioactivity. Sucrose uptake produced increases of 270% and 90% respectively in the rates of synthesis of arylsulphatase B and galactosyltransferase, whereas the rate of synthesis of alkaline ribonuclease was not affected. 3. The rates of degration of the enzymes were estimated by measuring the decay with time of the radioactivity of purified enzymes from prelabelled cells. In the absence of sucrose, the apparent half-lives of arylsulphatase B and galactosyltransferase were about 30 days and 40h respectively. After uptake of sucrose, the half-life of arylsulphatase B decreased to about 10 days and that of galactosyltransferase to 10h. Neither the half-life of alkaline ribonuclease (4 days) nor the rate of degradation of total cellular protein was affected by the uptake of sucrose. 4. These results indicate that the hyperactivity of lysosmal and Golgi-apparatus enzymes after the uptake of sucrose is accompanied by increases in the rates of both synthesis and degradation, and that the increased rates of degradation are insufficient to prevent accumulation of the excess of enzymes synthesized; also that the effects of sucrose uptake are restricted to the vacuolar apparatus.

Amino Acids↗
PubMed1980

Biosynthesis of chondroitin sulphate by a Golgi-apparatus-enriched preparation from cultures of mouse mastocytoma cells.

Mouse mastocytoma cells grown in suspension culture produce chondroitin 4-sulphate. A Golgi-apparatus-enriched fraction from these cells was prepared and examined for chondroitin-synthesizing activity. When Golgi-apparatus-enriched fractions were incubated with UDP-[14C]glucuronic acid and UDP-N-acetylgalactosamine, they demonstrated a greater than 13-fold increase in chondroitin-synthesizing activity over cell homogenates. Similar incubations with the addition of a pentasaccharide from chondroitin sulphate resulted in a greater than 40-fold increase in [14C]glucuronic acid-incorporating activity over cell homogenates. Other membrane fractions had much less activity, suggesting that the Golgi apparatus is the most active location for chondroitin biosynthesis. Products of the incubations indicated the formation of [14C]chondroitin glycosaminoglycan on endogenous primers and formation of [14C]-hexasaccharide and somewhat larger [14C]oligosaccharides on exogenous pentasaccharide acceptors. There was, however, a significant amount of large [14C]-chondroitin glycosaminoglycan formed on pentasaccharide, indicating that some pentasaccharide did serve as a true primer for polysaccharide synthesis.

Animals↗
PubMed1981

Newly biosynthesized cytochrome P-450 associated with the golgi apparatus from livers of rats induced with phenobarbital.

1. Cytochrome P-450 has been detected in preparations of golgi apparatus from the livers of phenobarbital-induced rats. 2. Newly biosynthesized cytochrome P-450 is also present in preparations of golgi apparatus. By using three different techniques to fractionate the golgi into vesicle contents and membrane components it was found that newly biosynthesized cytochrome P-450 is associated solely with the membrane fraction. 3. By investigating the susceptibility of cytochrome P-450, present in the golgi apparatus, to the action of trypsin it was found that the majority was oriented on the cytosolic face of the membrane.

Animals↗