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At least 721 records · Page 40Linked to original sources
PubMed1966

A function of the Golgi apparatus in polysaccharide synthesis and transport in the root-cap cells of wheat.

1. A radioautographic study of the cells of the root tips of wheat incubated with d-[1- or 6-(3)H]glucose has shown that labelled material is formed in the golgi apparatus of the root-cap cells. This material passed to the vesicles associated with the golgi bodies and then moved through the cytoplasm across the plasmalemma and was incorporated into the cell wall and slime layer of the tissue. 2. Analysis of the labelled material extracted from the root tips showed that the bulk of the radioactive material was polysaccharide; there were relatively small amounts of labelled lipids and protein in the tissue. 3. Starch was formed from the exogenous labelled glucose and it was located in the plastids of the cell. The synthesis of starch depended on the metabolic activity of the cells, which varied with the position of the cell in the various tissues of the root tip and with the amount of the exogenous glucose. 4. Isolation of the radioactive polysaccharides from the root tip incubated in the radioactive glucose has shown that the glucose was very rapidly incorporated into the galactosyl residues of the polymers. 5. Analysis of the radioactive polysaccharides has indicated that the material transported in the golgi vesicles is probably pectic substance. 6. A scheme for the synthesis of the storage and wall polysaccharides by separate routes and their location within the cell has been put forward.

Autoradiography↗
PubMed1994

Ceramide synthesis enhances transport of GPI-anchored proteins to the Golgi apparatus in yeast.

Inhibition of ceramide synthesis by a fungal metabolite, myriocin, leads to a rapid and specific reduction in the rate of transport of glycosylphosphatidylinositol (GPI)-anchored proteins to the Golgi apparatus without affecting transport of soluble or transmembrane proteins. Inhibition of ceramide biosynthesis also quickly blocks remodelling of GPI anchors to their ceramide-containing, mild base-resistant forms. These results suggest that the pool of ceramide is rapidly depleted from early points of the secretory pathway and that its presence at these locations enhances transport of GPI-anchored proteins specifically. A mutant that is resistant to myriocin reverses its effect on GPI-anchored protein transport without reversing its effects on ceramide synthesis and remodelling. Two hypotheses are proposed to explain the role of ceramide in the transport of GPI-anchored proteins.

Acyltransferases↗
PubMed2001

Vesicular and nonvesicular transport of ceramide from ER to the Golgi apparatus in yeast.

Transport and sorting of lipids must occur with specific mechanisms because the membranes of intracellular organelles differ in lipid composition even though most lipid biosynthesis begins in the ER. In yeast, ceramide is synthesized in the ER and transferred to the Golgi apparatus where inositolphosphorylceramide (IPC) is formed. These two facts imply that ceramide can be transported to the Golgi independent of vesicular traffic because IPC synthesis still continues when vesicular transport is blocked in sec mutants. Nonvesicular IPC synthesis in intact cells is not affected by ATP depletion. Using an in vitro assay that reconstitutes the nonvesicular pathway for transport of ceramide, we found that transport is temperature and cytosol dependent but energy independent. Preincubation of ER and Golgi fractions together at 4 degrees C, where ceramide transport does not occur, rendered the transport reaction membrane concentration independent, providing biochemical evidence that ER-Golgi membrane contacts stimulate ceramide transport. A cytosolic protease-sensitive factor is required after establishment of ER-Golgi contacts.

Adenosine Triphosphatases↗
PubMed1975

Membrane-bound neuraminidases of rat liver. Neuraminidase activity in Golgi apparatus.

The bulk (60 to 65%) of the neuraminidase activity present in rat liver homogenates was found in the M + L (mitochondria plus lysosomes) fraction, The patterns of subcellular distribution were essentially identical whether disialogangliosides or neuramin-lactose (2 yields 3') were utilized as substrates. A new neuraminidase, which hydrolyzes sialyl trisaccharides but which does not act upon glycoproteins and gangliosides, was detected in Golgi apparatus. Unlike the other particulate neuraminidases of rat liver, the Golgi enzyme is stimulated by prior incubation and by the addition of Ca2+ or Zn2+ at 1 mM concentration. Although plasma membrane-rich fractions are often contaminated by Golgi membranes the marked differences in their enzymic properties allowed a clear distinction between the neuraminidases present in these two types of membranes.

Animals↗
PubMed2004

Expansion of the Golgi apparatus in rat cerebral cortex following intracerebroventricular injections of streptozotocin.

Streptozotocin (STZ) is a bacterial toxin which selectively damages both insulin-producing cells and insulin receptors. Injections of STZ into the cerebral ventricles of experimental animals are followed by sustained biochemical, metabolic and behavioral effects resembling those which are found in human brains afflicted by Alzheimer's disease. The aim of the present study was to assess the effects of double intracerebroventricular application of STZ on the ultrastructure of rat frontoparietal cortical neurons. The most prominent change, seen 3 weeks after STZ injection, was a significant enlargement of the Golgi apparatus caused by expansion of the trans-Golgi segment of the cellular protein secretory pathway. Morphometric analysis revealed that the area of the trans part of the Golgi complex in neuronal cells was increased more than two-fold (median values: 312 x 10(3) nm in 14 neurons from control animals, and 846 x 10(3) nm3 in 19 neurons from STZ-treated animals, P = 0.0012), whereas that of the cis part did not significantly change. The effects of STZ did not resemble Golgi atrophy and fragmentation described in neurons from disease-prone brain structures of patients with Alzheimer's disease, but were similar to that observed after intravenous application of a non-metabolizable glucose analog 2-deoxyglucose. Considering that proamyloidogenic processing of beta-amyloid precursor protein may occur preferentially in the trans-Golgi segment, the observed early response of neuronal ultrastructure to desensitization of insulin receptors may predispose cells to form beta-amyloid deposits.

Animals↗
PubMed1978

Oncornavirus modification of the Golgi apparatus.

Two virus system, The Friend leukaemia virus (FLV) and the Rous sarcoma virus (RSV), were introduced into tissue both in vitro and in vivo. Both brought about substantial modification of the activity of the Golgi apparatus detectable as such by specific radioautographic studies. This modification was accompanied by changes in the development and social behaviour of the cells with some differences being detectable between the in vivo and in vitro studies.

Animals↗
PubMed2006

The E5 protein of BPV-4 interacts with the heavy chain of MHC class I and irreversibly retains the MHC complex in the Golgi apparatus.

BPV-4 E5 inhibits transcription of the bovine MHC class I heavy chain (HC) gene, increases degradation of HC and downregulates surface expression of MHC class I by retaining the complex in the Golgi apparatus (GA). Here we report that transcription inhibition can be alleviated by interferon treatment and the degradation of HC can be reversed by treatment with inhibitors of proteasomes and lysosomes. However, the inhibition of transport of MHC class I to the cell surface is irreversible. We show that E5 is capable of physically interacting with HC. Together with the inhibition of the vacuolar ATPase (due to the interaction between E5 and 16k subunit c), the interaction between E5 and HC is likely to be responsible for retention of MHC class I in the GA. C-terminus deletion mutants of E5 are incapable of either downregulating surface MHC class I or interacting with HC, establishing that the C-terminus domain of E5 is important in the inhibition of MHC class I.

Animals↗
PubMed1991

Primaquine blocks transport by inhibiting the formation of functional transport vesicles. Studies in a cell-free assay of protein transport through the Golgi apparatus.

The lysosomotropic amine primaquine has previously been shown to inhibit both secretory and recycling processes of cells in culture. We have used a cell-free assay that reconstitutes glycoprotein transport through the Golgi apparatus to investigate the mechanism of action of primaquine. In this assay, primaquine inhibits protein transport at a half-maximal concentration of 50 microM, similar to the concentration previously reported to disrupt protein secretion in cultured cells. Kinetic analysis of primaquine inhibition indicates that its point of action is at an early step in the vesicular transport mechanism. Primaquine does not inhibit the fusion of vesicles already attached to their target membranes. Primaquine irreversibly inactivates the membranes that form transport vesicles (donor), but not the membranes that are the destination of those vesicles (acceptor). Morphological data indicate that primaquine inhibits the budding of vesicles from the donor membranes. Once formed, the vesicles are refractile to primaquine action, and their attachment to and fusion with acceptor membranes proceeds unimpeded. In addition to illuminating the mechanism of action of primaquine, this study suggests that the selective action of this agent will make it a useful tool in the study of the formation of transport vesicles.

Animals↗
PubMed1997

Selective translocation of different markers in the ante- and retrograde pathways between the Golgi apparatus and the rough endoplasmic reticulum in a hybridoma cell line.

We examined the effects of brefeldin A (BFA, 10 micrograms/ml), an inhibitor of protein transport, on the redistribution of different markers of the Golgi apparatus (GA) in hybridoma H35 cells to examine selective transport of marker molecules between the rough endoplasmic reticulum (RER) and the GA. In H35 cells, the GAs had several cisternae with cis and trans faces as deduced by morphology such as relationship with RER and secretory granules. Thiamin pyrophosphatase (TPPase) was distributed in the trans elements, mannosidase II (man II) was in the cis-medial elements, and deposits of Zinc-Iodide-Osmium (ZIO) staining were localized in the cis/intermediate compartment. Upon BFA treatment for 5 min, man II and TPPase were redistributed in all cisternae. After 10 min of BFA treatment, TPPase activity was observed only in the RER, while the cis/intermediate compartment as evidenced by ZIO staining and man II remained. Upon clearance of BFA from the medium, cisternal structures with man II and ZIO staining reappeared at 30 min. TPPase activity was detected in the GA only after 120 min. Thus, in the retrograde pathway, the trans marker, TPPase moves earlier than the cismedial markers, man II and ZIO staining, whereas in the antegrade pathway, the cis-medial markers move earlier than the trans marker. These results suggest that BFA first alters the characteristic enzyme localization before the GA vanishes into the RER, and that selective transport mechanisms may exist for components of different stacks of the GA.

Animals↗
PubMed1984

Coated vesicles of liver Golgi apparatus increased by ascorbate.

Cultured hepatocytes and hepatoma cells when treated for 10-30 min with 30 mM ascorbate (vitamin C) responded by a 2- to 3- fold increase in the numbers of coated vesicles of the Golgi apparatus zone as determined by quantitation from electron micrographs. At a near optimal concentration of 30 mM ascorbate, the effect was reproduced under a variety of conditions of fixation and methods of specimen preparation.

Animals↗
PubMed2000

GDP-fucose uptake into the Golgi apparatus during xyloglucan biosynthesis requires the activity of a transporter-like protein other than the UDP-glucose transporter.

The molecular mechanisms regulating hemicelluloses and pectin biosynthesis are poorly understood. An important question in this regard is how glycosyltransferases are oriented in the Golgi cisternae, and how nucleotide sugars are made available for the synthesis of the polymers. Here we show that the branching enzyme xyloglucan alpha,1-2 fucosyltransferase (XG-FucTase) from growing pea (Pisum sativum) epicotyls was latent and protected against proteolytic inactivation on intact, right-side-in pea stem Golgi vesicles. Moreover, much of the XG-FucTase activity was membrane associated. These data indicate that XG-FucTase is a membrane-bound luminal enzyme. GDP-Fuc uptake studies demonstrated that GDP-Fuc was taken up into Golgi vesicles in a protein-mediated process, and that this uptake was not competed by UDP-Glc, suggesting that a specific GDP-Fuc transporter is involved in xyloglucan biosynthesis. Once in the lumen, Fuc was transferred onto endogenous acceptors, including xyloglucan. GDPase activity was detected in the lumen of the vesicles, suggesting than the GDP produced upon transfer of Fuc was hydrolyzed to GMP and inorganic phosphate. We suggest than the GDP-Fuc transporter and GDPase may be regulators of xyloglucan fucosylation in the Golgi apparatus from pea epicotyls.

Biological Transport, Active↗
PubMed1997

Novel membrane protein complexes for protein glycosylation in the yeast Golgi apparatus.

Three type II membrane proteins Anp1, Van1 and Mnn9 of Saccharomyces cerevisiae share significant sequence homology. Their precise biochemical activity has long been unknown though the mutant phenotype indicates their participation in protein glycosylation in the Golgi apparatus. To shed light on their molecular characteristics, interactions of these proteins were studied by immunoprecipitation after solubilizing the membrane by nonionic detergent. Our results indicated that there are at least two submembrane complexes containing these proteins: one contains Van1 and Mnn9 proteins and the other contains Anp1 and Mnn9 proteins. In addition, Hoc1 protein which has significant homology to Och1 protein colocalized with Anp1 and Mnn9 proteins. These complexes with similar but partially different constituents may represent essential parts of glycosylation machinery in the yeast Golgi compartments.

Alleles↗
PubMed1998

Characterization of KIF1C, a new kinesin-like protein involved in vesicle transport from the Golgi apparatus to the endoplasmic reticulum.

Kinesins comprise a large family of microtubule-based motor proteins, of which individual members mediate specific types of motile processes. Using the ezrin domain of the protein-tyrosine phosphatase PTPD1 as a bait in a yeast two-hybrid screen, we identified a new kinesin-like protein, KIF1C. KIF1C represents a member of the Unc104 subfamily of kinesin-like proteins that are involved in the transport of mitochondria or synaptic vesicles in axons. Like its homologues, the 1103-amino acid protein KIF1C consists of an amino-terminal motor domain followed by a U104 domain and probably binds to target membranes through carboxyl-terminal sequences. Interestingly, KIF1C was tyrosine-phosphorylated after peroxovanadate stimulation when overexpressed in 293 or NIH3T3 fibroblasts or in native C2C12 cells. Using immunofluorescence, we found that KIF1C is localized primarily at the Golgi apparatus. In brefeldin A-treated cells, the Golgi membranes and KIF1C redistributed to the endoplasmic reticulum (ER). This brefeldin A-induced flow of Golgi membranes into the ER was inhibited in cells transiently overexpressing catalytically inactive KIF1C. In conclusion, our data suggest an involvement of tyrosine phosphorylation in the regulation of the Golgi to ER membrane flow and describe a new kinesin-like motor protein responsible for this transport.

Amino Acid Sequence↗
PubMed1989

Golgi apparatus in chick skeletal muscle: changes in its distribution during end plate development and after denervation.

In the course of studies about the cellular and molecular mechanisms of motor end plate formation, the distribution of the Golgi apparatus (GA) has been investigated by immunofluorescence methods in chick skeletal muscle in primary culture and in innervated muscles of 15-day-old chicks. By using a monoclonal antibody directed against the GA, we confirmed the known distribution of the GA in myogenic cells: a juxtanuclear polarized organization in myoblasts and a perinuclear nonpolarized distribution in myotubes. In contrast, the innervated anterior latissimus dorsi muscle of "young adult" chicks displayed a focal distribution of GA that appeared restricted to areas located underneath the motor end plates identified by alpha-bungarotoxin fluorescent labeling of the acetylcholine receptor. Five days after denervation of anterior latissimus dorsi muscle, a striking reorganization and expansion of the GA was observed. The GA now showed a perinuclear distribution in close association with every nucleus of the muscle fibers as observed in myotubes. The focal distribution of the GA in innervated muscle fibers and its remodeling upon denervation are interpreted in terms of a model of local synthesis, processing, and routing of acetylcholine receptor to the end plate and of regulation of these processes by functional motor innervation.

Animals↗
PubMed2000

Localization and targeting of SCG10 to the trans-Golgi apparatus and growth cone vesicles.

SCG10 is a membrane-associated, microtubule-destabilizing protein of neuronal growth cones. Using immunoelectron microscopy, we show that in the developing cortex of mice, SCG10 is specifically localized to the trans face Golgi complex and apparently associated with vesicular structures in putative growth cones. Consistent with this, subcellular fractionation of rat forebrain extracts demonstrates that the protein is enriched in the fractions containing the Golgi apparatus and growth cone particles. In isolated growth cone particles, SCG10 was found to be particularly concentrated in the growth cone vesicle fraction. To evaluate the molecular determinants of the specific targeting of SCG10 to growth cones, we have transfected PC12 cells and primary neurons in culture with mutant and fusion cDNA constructs. Deletion of the amino-terminal domain or mutations within this domain that prevented palmitoylation at cysteines 22 and 24 abolished Golgi localization as well as growth cone targeting, suggesting that palmitoylation of the amino-terminal domain is a necessary signal for Golgi sorting and possibly transport of SCG10 to growth cones. Fusion proteins consisting of the amino-terminal domain of SCG10 and the cytosolic proteins stathmin or glutathione-S-transferase colocalized with a Golgi marker, alpha-mannosidase II, and accumulated in growth cones of both axons and dendrites. These results reveal a novel axonal/dendritic growth cone targeting sequence that involves palmitoylation.

Animals↗
PubMed2003

Alpha-synuclein expression localizes to the Golgi apparatus in bovine adrenal medullary chromaffin cells.

Alpha-synuclein (alphaS) is a protein of unknown function linked to Parkinson's disease. We examined alphaS expression in adrenal medullary chromaffin cells. Immunocytochemistry showed expression of alphaS in the Golgi apparatus and vesicles, consistent with its putative role in vesicular function within synapses, and with O-linked glycosylation of alphaS in autosomal-recessive Parkinson's disease. The chromaffin cell culture system offers advantages in studying the role of alphaS in vesicular trafficking and secretion.

Adrenal Medulla↗
PubMed2000

The role of the tethering proteins p115 and GM130 in transport through the Golgi apparatus in vivo.

Biochemical data have shown that COPI-coated vesicles are tethered to Golgi membranes by a complex of at least three proteins: p115, giantin, and GM130. p115 binds to giantin on the vesicles and to GM130 on the membrane. We now examine the function of this tethering complex in vivo. Microinjection of an N-terminal peptide of GM130 or overexpression of GM130 lacking this N-terminal peptide inhibits the binding of p115 to Golgi membranes. Electron microscopic analysis of single microinjected cells shows that the number of COP-sized transport vesicles in the Golgi region increases substantially, suggesting that transport vesicles continue to bud but are less able to fuse. This was corroborated by quantitative immunofluorescence analysis, which showed that the intracellular transport of the VSV-G protein was significantly inhibited. Together, these data suggest that this tethering complex increases the efficiency with which transport vesicles fuse with their target membrane. They also provide support for a model of mitotic Golgi fragmentation in which the tethering complex is disrupted by mitotic phosphorylation of GM130.

Animals↗