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PubMed1984

The Golgi apparatus and lysosomes of rat pancreatic acinar cells following refeeding.

The short term effects of refeeding on the Golgi apparatus and lysosomes of the rat exocrine pancreas were evaluated by ultrastructural, morphometric and cytochemical methods. Ten minutes after refeeding, there was a significant enlargement of Golgi cisternae and a significant increase, compared with the controls, in the number of condensing vacuoles and lysosomes. These modifications were accompanied by the appearance of acid phosphatase activity in stacked Golgi cisternae (as well as GERL) of some cells. One hour after refeeding, there were about the same numbers of condensing vacuoles and lysosomes as in the controls; Golgi cisternae were still significantly enlarged, compared with the controls, but they were no longer reactive for acid phosphatase. In both fasting and refed animals, acid phosphatase activity was demonstrable in tubular lysosomes. The data are interpreted in terms both of membrane disposal and recycling, leading to enhanced formation of zymogen granules, during physiologically stimulated secretion.

Acid Phosphatase↗
PubMed2001

Architecture of the Golgi apparatus of a scale-forming alga: biogenesis and transport of scales.

Mechanisms of transport of secretory products across the Golgi apparatus (GA) as well as of scale formation in prymnesiophytes have remained controversial. We have used a quantitative morphological approach to study formation and transport of scales across the GA in haploid cells of Pleurochrysis sp. The GA of these cells differs from the GA of higher plants in at least six morphological characteristics. Our results show that scales form in the trans-Golgi network (TGN) and transit the TGN in heretofore unrecognized prosecretory vesicles. Prosecretory vesicles differentiate into secretory vesicles prior to exocytosis of scales to the cell surface. Because prosecretory vesicles are only fragments of TGN cisternae, the classical model of cisternal progression is not a valid mechanism of transport in this alga. TGN transport vesicles are also involved in scale formation; however, the role of tubular connections between cisternae of a single stack-TGN unit is not clear. The relationship of two morphological types of cisternal dilations to a membrane-associated, bottlebrush-shaped macromolecule of novel morphology suggests a new hypothesis for the biogenesis of scales.

Algal Proteins↗
PubMed2000

Kinetic characterization of calcium uptake by the rat liver Golgi apparatus.

We carried out a kinetic characterization of the Ca(2+)active transport in the rat liver Golgi Apparatus (GA) membrane. Calcium accumulation by vesicles of a GA enriched fraction was found to be a function of both Ca(2+)and ATP-Mg concentrations, it was inhibited by 2 microm thapsigargin but not stimulated by 3 microm calmodulin. The kinetic parameter values obtained for the GA Ca(2+)pump were: J(max)of 3.96 nmol/mg min, K(m)for Ca(2+)of 0.150 microm and two K(m)'s for ATP of 1.14 microm and 519 microm. These results were almost identical to those obtained for the endoplasmic reticulum (ER) fraction, indicating that the GA Ca(2+)pump is a sarco/endoplasmic reticulum (SERCA) P-type, analogous-if not identical-to that present in the ER.

Adenosine Triphosphate↗
PubMed1987

Isolation and characterization of chicken liver and hepatoma Mc-29 endoplasmic reticulum and Golgi apparatus membranes and biosynthesis of their glycoconjugates.

Rough and smooth endoplasmic reticulum (ER) membranes and trans-Golgi apparatus (GA) fraction, intermediate GA fraction, and cis-GA fraction from White Leghorn chicken liver and hepatoma Mc-29 were isolated. Their purity was checked by electron microscopy and by determination of the activity of the marker enzymes. Rough and smooth membranes were also identified by calculation of the ratio between the content of RNA and the total phospholipids. It was found that the membrane fractions were pure enough. The tumor exhibited a decreased amount of ER and a small GA when compared when the ER and GA in the liver. The biogenesis of membrane glycoconjugates was followed by in vivo experiments either with [14C]glucosamine or by double labeling with [14C]N-acetylmannosamine and [3H]leucine. The radioisotope studies indicated that the synthesis rate of protein in liver and hepatoma rough ER was nearly the same, but in the tumor cells the glycosylation of the nascent polypeptide chain and the formation of glycolipids were significantly decreased.

Animals↗
PubMed1979

Is thiamine pyrophosphatase a reliable marker of the neuronal Golgi apparatus? A critical analysis.

The thiamine pyrophosphatase histochemical technique is believed to be a suitable approach to the selective staining of the Golgi vesicles of all animal cells, icluding the neuron. However, during the past decade a considerable number of data have been published, suggesting that the TPPase is in general a membrane-associated enzyme in the brain, which can be found in subcellular fractions other than Golgi lamellae. It has therefore become necessary to reconsider the view that thiamine pyrophosphatase is an exclusive marker enzyme of the Golgi apparatus.

Animals↗
PubMed2001

What can yeast tell us about N-linked glycosylation in the Golgi apparatus?

The N-glycans found on eukaryotic glycoproteins occur in a vast range of different structures. A universal N-glycan core is attached to proteins during synthesis in the endoplasmic reticulum, and then diversity is generated as the proteins pass through the Golgi apparatus. Many of the Golgi-localised glycosyltransferases have now been identified in both yeast and mammalian cells, but it is still unclear how these enzymes are integrated into the Golgi and the rest of the cell so as to ensure efficient and specific processing of passing substrates. This review discusses the potential of the yeast system to address these issues.

Glycosylation↗
PubMed1987

Quantitative ultrastructural, autoradiographic evidence for the magnitude and early involvement of the Golgi apparatus complex in the endocytosis of wheat germ agglutinin by cultured neuroblastoma.

Several ligands undergo endocytosis into the Golgi apparatus. We have examined with a quantitative ultrastructural, autoradiographic method the sequential endocytosis of tritiated wheat germ agglutinin (3H-WGA) by cultured murine neuroblastoma cells. Cells were incubated with 3H-WGA for 1 hour at 4 degrees C, washed, and incubated in complete medium without ligand at 37 degrees C for 5, 15, 30, and 120 minutes. At 5 minutes, the optimized sources/micron 2 of neuroblastoma cell area, which represented the grain density of each compartment, were as follows: smooth vesicles and tubules, 1.03 +/- 0.88; Golgi-associated vesicles, i.e., clusters of vesicles within a 1 micron radius of the Golgi cisterns, 1.03 +/- 0.31; Golgi cisterns, less than 0.01; and lysosomes, 0.26 +/- 0.16. At 15 minutes grain densities were: smooth vesicles and tubules, 0.9 +/- 0.34; Golgi-associated vesicles, 1.41 +/- 0.28; Golgi cisterns, 0.73 +/- 0.41; and lysosomes, 0.1 +/- 0.09. At 30 minutes grain densities were: smooth vesicles and tubules, 0.46 +/- 0.46; Golgi-associated vesicles, 1.78 +/- 0.34; Golgi cisterns, 0.89 +/- 0.78; and lysosomes, 0.39 +/- 0.14. At 2 hours, smooth vesicles, tubules, and Golgi cisterns were not labeled, Golgi-associated vesicles were still labeled (0.71 +/- 0.1), and lysosomes were heavily labeled (2.17 +/- 0.22). These results are consistent with the hypotheses that either the Golgi complex (cisterns and associated vesicles) is an early and intermediate step of the endocytosis of 3H-WGA into lysosomes or that it constitutes part of a separate and quantitatively significant pathway of endocytosis of this ligand.

Animals↗
PubMed2001

The Cdk5-p35 kinase associates with the Golgi apparatus and regulates membrane traffic.

We show here that an active Cdk5-p35 kinase is present in Golgi membranes, where it associates with a detergent-insoluble fraction containing actin. In addition, Cdk5-p35-dependent phosphorylation of alpha-PAK immunoreactive protein species was detected in Golgi membranes, as well as an interaction with the small GTPase, Cdc42. Moreover, antisense oligonucleotide suppression of Cdk5 or p35 in young cultured neurons, as well as inhibition of Cdk5 activity with olomoucine, blocks the formation of membrane vesicles from the Golgi apparatus. Taken together, these results show a novel subcellular localization of this kinase and suggest a role for Cdk5-p35 in membrane traffic during neuronal process outgrowth.

Animals↗
PubMed1978

Biochemical studies of rat liver Golgi apparatus. I. Isolation and preliminary characterization.

A method is described for the isolation of morphologically well-preserved Golgi apparatus from rat liver. The method is essentially the same as that of Morré et al. (Morré, D.J., Hamilton, R.L., Mollenhauser, H.H., Mahley, R.W., Cunningham, W.P., Cheetham, R.D., & Lequire, V.S. (1970) J. Cell Biol. 44, 484-491) except that mild cell disruption is achieved by means of a stainless-steel sieve. The average recoveries of protein and galactosyltransferase in the isolated fraction are about 6 mg from 10 g of perfused liver and about 35% from the homogenate, respectively. The preparation is virtually free from succinate-cytochrome c reductase, glucose-6-phosphatase, acid phosphatase, and 5'-nucleotidase. The Golgi fraction as well as its vesicular fragments is homogeneous upon isopycnic centrifugation in both sucrose and dextran density gradients. Their buoyant densities in sucrose are significantly higher than those in dextran, indicating that both forms of the organelle are closed systems which are impermeable to macromolecules. The galactosyltransferase activity of a freshly prepared Golgi fraction, measured with ovalbumin as galactosyl acceptor, is activated 26-fold by the addition of Triton X-100, whereas those of homogenized, sonicated, and aged preparations are only activated 2- to 4-fold.

Animals↗
PubMed2003

Retinoic acid-induced Golgi apparatus disruption in F2000 fibroblasts: a model for enhanced intracellular retrograde transport.

Retinoic acid (RA) can transform the Golgi apparatus (GA) into a diffuse vacuolar aggregate and increase the toxicity of some immunotoxins that enter into cells by receptor-mediated endocytosis. An ultramorphological study of the RA-induced GA disruption was performed on F2000 fibroblasts. Cultures were treated with 0.11 to 30 microM RA for 7-180 min. The endocytosis of Limax flavus agglutinin-peroxidase conjugate (LFA), and the interactions between a phorbol ester (PMA) and RA concerning GA disruption, were examined. Exposure to 0.33 microM RA for 20 min transformed the GA into vacuolar aggregate. These vacuoles were not involved in endocytosis since they remained unstained after endocytosis of LFA. However, the lysosomes were involved in endocytosis, as they were strongly stained. Therefore, a RA-induced shift towards lysosomal routing of the entered LFA was presumed. Exposure to PMA made cells resistant to the Golgi-disturbing effects of RA, indicating that protein kinase C plays an important role in this process.

Biological Transport↗
PubMed1970

In vivo incorporation of radioactive metabolites by Golgi apparatus and other cell fractions of onion stem.

Incorporation in vivo of various (14)C-labeled substrates into dictyosomes of onion (Allium cepa) stem was determined, and comparisons were made with other cell fractions on a nitrogen basis. Tissue explants were incubated for varying times in the presence of the radioactive metabolites supplied in the external medium. Fractions were then obtained from homogenates stabilized with glutaraldehyde. Purified fractions containing dictyosomes (individual stacks of cisternae) of the Golgi apparatus were obtained by centrifugation in a sucrose gradient also yielding a smooth membrane fraction free of dictyosomes. Dictyosomes were preferentially labeled with choline-1,2-(14)C and acetate-2-(14)C, suggesting that plant Golgi apparatus participate in the synthesis or modification of membrane lipids. Dictyosomes were also labeled with glucose-U-(14)C and leucine-U-(14)C, but on a molar basis incorporation was less than with choline or acetate.

Journal Article↗
PubMed1984

Phospholipids, vitamin A and ubiquinone of the Golgi apparatus subfractions from rat liver after acute ethanol intoxication.

Previous investigations from our laboratory have shown that during acute ethanol intoxication the Golgi apparatus seems involved in impaired dismission of lipoproteins. In the present paper the phospholipid distributions of Golgi subfractions have been analyzed in livers of normal and ethanol intoxicated rats. No significant differences in the phospholipid classes have been observed in this study. On the contrary, a decrease of vitamin A and ubiquinone in Golgi subfractions is evident. The results are briefly discussed in view of the role played by these endogenous antioxidants in the Golgi membranes and in the pathogenesis of ethanol induced fatty liver.

Alcoholic Intoxication↗
PubMed2003

Reduction of the size of the Golgi apparatus of spinal anterior horn cells in patients with X-linked spinal and bulbar muscular atrophy.

The Golgi apparatus (GA) of spinal anterior horn cells was examined immunohistochemically in five patients with X-linked spinal and bulbar muscular atrophy (SBMA), in five patients with sporadic amyotrophic lateral sclerosis (ALS) and in five patients without neurodegenerative diseases. In SBMA cases, reduction of the size of the GA was observed in numerous anterior horn cells; however, fragmentation of the GA, previously described in sporadic and familial ALS with SOD1 mutations, was observed only in a few neurons. In addition, motor neurons bearing an intranuclear inclusion showed a normal network of elements of the GA. The frequencies of fragmented GA in counted motor neurons were 0-2.4 % in SBMA cases, 0-3.0 % in normal control cases and 15.7-55.3 % in ALS cases. The different frequency of fragmented GA between SBMA and ALS adds another finding of pathogenetic difference of neurodegeneration in these two motor neuron diseases.

Aged↗
PubMed1997

Dispersal of Golgi apparatus in nocodazole-treated fibroblasts is a kinesin-driven process.

The morphology and location of the Golgi apparatus (GA) has been shown to change upon microtubule (Mt) depolymerization. The GA in different cell types undergoes fragmentation and dispersal throughout the cytoplasm upon treatment with nocodazole. In this study experiments were performed on human skin fibroblasts (HSFs) and rat fibroblasts (REF 52) to determine whether the dispersal of GA in HSFs treated with nocodazole is dependent on Mts that show the higher resistance to this Mt-depolymerizing drug. It is shown here that nocodazole at concentrations as low as 100 nM caused the GA to disperse in treated fibro-blasts that still contained a fairly high amount of Mts. Antibody-blocking analysis of Mts after injection of biotin-tubulin into the HSFs was used to show that nocodazole at low concentrations induced the stabilization of the remaining Mts. The complete disruption of Mts by the incubation of HSFs at 0 degrees C prevented the dispersal of GA from the perinuclear area when the cells were subsequently warmed to 37 degrees C in the presence of nocodazole. Micro-injection of the well-characterized HD antibody against kinesin but not the preimmune IgG caused inhibition of GA dispersal in HSFs by nocodazole. These data demonstrate that the dispersal of GA in the cytoplasm of nocodazole-treated HSFs is a kinesin-driven process with stable Mts serving as tracks.

Animals↗
PubMed1988

Lectin-gold cytochemistry of mucin oligosaccharide biosynthesis in Golgi apparatus of airway secretory cells of the hamster.

To elucidate the mechanism for the biosynthesis of O-linked mucin oligosaccharides, airway secretory cells of the hamster trachea were embedded in Lowicryl K4M resin, and sections were examined by lectin-gold cytochemistry with special attention focused on the Golgi apparatus. The interrelations between the Golgi cisternae stained with five different lectins were determined by double-staining procedures using various combinations of lectins conjugated with 14-nm and 8-nm colloidal gold. Several cis cisternae were stained only with HPA (Helix pomatia agglutinin specific for terminal alpha-N-acetylgalactosamine). The next medial cisternae were not stained with HPA, but reacted positively with two lectins, GSII (Griffonia simplicifolia agglutinin II specific for terminal alpha- or beta-N-acetylglucosamine) and RCAI (Ricinus communis agglutinin I specific for beta-galactose). The trans cisternae as well as condensing and mature secretory granules were labeled with four lectins, UEAI (Ulex europaeus agglutinin I specific for terminal alpha-L-fucose) and LFA (Limax flavus agglutinin specific for terminal N-acetyl or N-glycolyl neuraminic acid) in addition to HPA and RCAI. The same number of trans cisternae were positive to HPA and UEAI, whereas LFA bound to a few transmost cisternae but fewer than were stained with HPA or UEAI. The observed sequential appearance of different sugar residues in different levels of Golgi cisternae (from cis to trans cisternae) coincides quite well with the sugar sequence of airway mucin oligosaccharide (from reducing to nonreducing ends) proposed by biochemical analysis. It is suggested that airway mucin oligosaccharides elongate during a vectorial movement through the Golgi stack from cis toward trans and that the stack consists of at least three functionally distinct segments, cis, medial, and trans; in these three segments there take place, respectively, the initial O-glycosylation of mucin core peptide, the formation of a core region of oligosaccharide chain, and the completion of chain growth by addition of terminal sugar moieties.

Animals↗
PubMed2006

Transport of ricin from endosomes to the Golgi apparatus is regulated by Rab6A and Rab6A'.

Ricin is transported from early endosomes and/or the recycling compartment to the trans-Golgi network (TGN) and subsequently to the endoplasmic recticulum (ER) before it enters the cytosol and intoxicates cells. We have investigated the role of the Rab6 isoforms in retrograde transport of ricin using both oligo- and vector-based RNAi assays. Ricin transport to the TGN was inhibited by the depletion of Rab6A when the Rab6A messenger RNA (mRNA) levels were reduced by more than 40% and less than 75%. However, when Rab6A mRNA was reduced by more than 75% and Rab6A' mRNA was simultaneously up-regulated, the inhibition of ricin sulfation was abolished, indicating that the up-regulation of Rab6A' may compensate for the loss of Rab6A function. In addition, we found that a near complete depletion of Rab6A' gave approximately 40% reduction in ricin sulfation. The up-regulation of Rab6A mRNA levels did not seem to compensate for the loss of Rab6A' function. The depletion of both Rab6A and Rab6A' gave a stronger inhibition of ricin sulfation than what was observed knocking down the two isoforms separately. In conclusion, both Rab6A and Rab6A' seem to be involved in the transport of ricin from endosomes to the Golgi apparatus.

Endosomes↗
PubMed2006

Capacity of the Golgi apparatus for cargo transport prior to complete assembly.

In yeast, particular emphasis has been given to endoplasmic reticulum (ER)-derived, cisternal maturation models of Golgi assembly while in mammalian cells more emphasis has been given to golgins as a potentially stable assembly framework. In the case of de novo Golgi formation from the ER after brefeldin A/H89 washout in HeLa cells, we found that scattered, golgin-enriched, structures formed early and contained golgins including giantin, ranging across the entire cis to trans spectrum of the Golgi apparatus. These structures were incompetent in VSV-G cargo transport. Second, we compared Golgi competence in cargo transport to the kinetics of addition of various glycosyltransferases and glycosidases into nascent, golgin-enriched structures after drug washout. Enzyme accumulation was sequential with trans and then medial glycosyltransferases/glycosidases found in the scattered, nascent Golgi. Involvement in cargo transport preceded full accumulation of enzymes or GPP130 into nascent Golgi. Third, during mitosis, we found that the formation of a golgin-positive acceptor compartment in early telophase preceded the accumulation of a Golgi glycosyltransferase in nascent Golgi structures. We conclude that during mammalian Golgi assembly components fit into a dynamic, first-formed, multigolgin-enriched framework that is initially cargo transport incompetent. Resumption of cargo transport precedes full Golgi assembly.

Biological Transport↗
PubMed1993

Effect of monensin on plant Golgi: re-examination of the monensin-induced changes in cisternal architecture and functional activities of the Golgi apparatus of sycamore suspension-cultured cells.

We have re-examined the effects of the ionophore monensin on the Golgi apparatus of sycamore maple suspension-cultured cells using a combination of high pressure freezing, immunocytochemical and biochemical techniques. Exposure of the cells to 10 microM monensin, which reduces protein secretion by approximately 90%, resulted first in the swelling of the trans-Golgi network, then of the trans-most trans-cisterna, the remaining trans-cisternae, and finally of the cis and medial cisternae. We postulate that these different rates of swelling reflect an underlying hierarchy of compartmental acidification with the trans-Golgi network being the most acidic compartment. Recovery occurred in the reverse sequence. Previous studies have suggested that the large swollen vesicles that accumulate in the cytoplasm of monensin-treated cells arise from the swelling and detachment of entire trans-cisternae. However, based on the many membrane blebbing configurations seen in association with the trans-Golgi network and the trans-Golgi cisternae of monensin-treated cells, and the fact that the surface area of the trans-Golgi cisternae is about five times greater than the surface area of the swollen vesicles, it appears that the swollen vesicles are produced by a budding mechanism. After 35-40 min of monensin treatment, cells with smaller, non-swollen, compact Golgi stacks began to appear and rapidly increased in number, contributing > 60% of the cell population after 60 min and > 80% after 100 min. In contrast, large numbers of swollen vesicles persisted in the cytoplasm of all cells for over 100 min. Since azide treatment of monensin-treated cells can prematurely induce the unswelling response and cellular ATP levels drop substantially after 45 min of monensin treatment, we propose that un-swelling of the Golgi stacks is due to a monensin-induced decline in ATP levels in the cells. Immunocytochemical labeling of the high pressure frozen cells with anti-xyloglucan antibodies demonstrated that the concentration of xyloglucan, a hemicellulose, in the swollen vesicles increased with time. This increase in vesicle contents may explain why these swollen vesicles do not contract in parallel with the Golgi stacks. In vivo labeling experiments with [3H]fucose, [3H]UDP-glucose and [3H]leucine demonstrated that monensin-treatment not only inhibited protein secretion, but also cellulose synthesis. Protein synthesis, on the other hand, was reduced only slightly during the first 30 min of treatment, but quite strongly between 30 and 60 min, consistent with the observed drop in ATP levels after > 40 min of exposure to monensin.(ABSTRACT TRUNCATED AT 400 WORDS)

Cells, Cultured↗