The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Paul Dupree - One of the best experts on this subject based on the ideXlab platform.
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targeting of active sialyltransferase to the plant Golgi Apparatus
The Plant Cell, 1998Co-Authors: D. Janine Sherrier, Tracy A Prime, Paul DupreeAbstract:Glycosyltransferases in the Golgi Apparatus synthesize cell wall polysaccharides and elaborate the complex glycans of glycoproteins. To investigate the targeting of this type of enzyme to plant Golgi compartments, we generated transgenic Arabidopsis plants expressing α-2,6-sialyltransferase, a glycosyltransferase of the mammalian trans -Golgi cisternae and the trans -Golgi network. Biochemical analysis as well as immunolight and immunoelectron microscopy of these plants indicate that the protein is targeted specifically to the Golgi Apparatus. Moreover, the protein is predominantly localized to the cisternae and membranes of the trans side of the organelle. When supplied with the appropriate substrates, the enzyme has significant α-2,6-sialyltransferase activity. These results indicate a conservation of glycosyltransferase targeting mechanisms between plant and mammalian cells and also demonstrate that glycosyltransferases can be subcompartmentalized to specific cisternae of the plant Golgi Apparatus.
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The plant Golgi Apparatus
Biochimica et Biophysica Acta, 1998Co-Authors: Paul Dupree, D. Janine SherrierAbstract:Abstract 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.
D. Janine Sherrier - One of the best experts on this subject based on the ideXlab platform.
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targeting of active sialyltransferase to the plant Golgi Apparatus
The Plant Cell, 1998Co-Authors: D. Janine Sherrier, Tracy A Prime, Paul DupreeAbstract:Glycosyltransferases in the Golgi Apparatus synthesize cell wall polysaccharides and elaborate the complex glycans of glycoproteins. To investigate the targeting of this type of enzyme to plant Golgi compartments, we generated transgenic Arabidopsis plants expressing α-2,6-sialyltransferase, a glycosyltransferase of the mammalian trans -Golgi cisternae and the trans -Golgi network. Biochemical analysis as well as immunolight and immunoelectron microscopy of these plants indicate that the protein is targeted specifically to the Golgi Apparatus. Moreover, the protein is predominantly localized to the cisternae and membranes of the trans side of the organelle. When supplied with the appropriate substrates, the enzyme has significant α-2,6-sialyltransferase activity. These results indicate a conservation of glycosyltransferase targeting mechanisms between plant and mammalian cells and also demonstrate that glycosyltransferases can be subcompartmentalized to specific cisternae of the plant Golgi Apparatus.
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The plant Golgi Apparatus
Biochimica et Biophysica Acta, 1998Co-Authors: Paul Dupree, D. Janine SherrierAbstract:Abstract 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.
Nicholas K. Gonatas - One of the best experts on this subject based on the ideXlab platform.
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Rous-Whipple Award Lecture. Contributions to the physiology and pathology of the Golgi Apparatus.
American Journal of Pathology, 1994Co-Authors: Nicholas K. GonatasAbstract:Abstract The importance of the Golgi Apparatus in the transport, processing, and targeting of proteins destined for secretion, plasma membranes, and lysosomes has emerged from numerous studies. In this paper we review studies from our laboratory dealing with 1) the Golgi Apparatus during mitosis and the role of microtubules in maintaining the structure of the organelle, 2) the endocytosis of antibodies, exogenous lectins, and toxins into the Golgi Apparatus of several cells including neurons in vivo and in vitro, 3) the traffic of MG-160, a membrane sialoglycoprotein of the medial cisternae of the Golgi Apparatus, from the trans-Golgi network to the Golgi cisternae, and 4) the involvement of the Golgi Apparatus of motor neurons in the pathogenesis of amyotrophic lateral sclerosis. We conclude with a summary of ongoing work on the primary structure of MG-160 and introduce evidence suggesting that this intrinsic membrane protein of the Golgi Apparatus may be involved in the regulation of endogenous, autocrine, basic fibroblast growth factor. We hope that this review will stimulate studies on the Golgi Apparatus of neurons, which may lead to the discovery of neuron-specific properties of this important organelle and its involvement in the pathogenesis of neurodegenerative disorders.
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The Golgi Apparatus of motor neurons in amyotrophic lateral sclerosis.
Annals of Neurology, 1993Co-Authors: Zissims Mourelatos, Anthony T. Yachnis, Lucy B. Rorke, Jacqueline Mikol, Nicholas K. GonatasAbstract:Abstract The Golgi Apparatus plays a key role in the posttranslational processing of polypeptides destined for secretion, incorporation into plasma membranes, and fast axoplasmic transport. Dispersion or fragmentation of the Golgi Apparatus, experimentally induced by microtubule-disrupting agents, is associated with decreased secretion of immunoglobulins and insulin. The Golgi Apparatus is also involved in targeting of lysosomal enzymes and in the endocytosis of certain hormones, receptors, and toxins. There is a paucity of information on this important organelle in human neuropathological conditions. Using an organelle-specific antiserum we have examined by immunocytochemistry the Golgi Apparatus of motor neurons in the spinal cord in 4 patients with amyotrophic lateral sclerosis and 1 patient with Werdnig Hoffmann's disease, 1 with infantile neuronal degeneration, 1 with adult-type familial bulbospinal atrophy, 1 with mitochondrial myopathy with cytochrome c oxidase deficiency, 1 with centronuclear myopathy, and 1 with Duchenne's muscular dystrophy, and in 9 age-matched control subjects. In all motor neuronopathies examined and in the patient with mitochondrial myopathy, 20 to 85% of neurons counted had "fragmented" Golgi Apparatus. In age-matched control subjects and the other 2 patients with myopathies, 0 to 1.65% of motor neurons had fragmented Golgi Apparatus. These findings suggest that the Golgi Apparatus of motor neurons is involved in patients with amyotrophic lateral sclerosis and related motor neuron diseases, and perhaps in patients with certain fatal primary myopathies.
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Fragmentation of the Golgi Apparatus of motor neurons in amyotrophic lateral sclerosis.
American Journal of Pathology, 1992Co-Authors: Nicholas K. Gonatas, Zissims Mourelatos, Anna Stieber, Youhai H. Chen, Jacqueline O. Gonatas, Stanley H. Appel, A. P. Hays, W. F. Hickey, J. J. HauwAbstract:Abstract The Golgi Apparatus (complex) is at the center stage of important functions of processing and transport of plasma membrane, lysosomal, and secreted proteins. The involvement of the Golgi Apparatus in the pathogenesis of chronic degenerative diseases of neurons is virtually unknown. In the present study, fragmentation and atrophy of the Golgi Apparatus of motor neurons in amyotrophic lateral sclerosis (ALS), has been detected with organelle specific antibodies. Approximately 30% of motor neurons in five ALS patients showed a fragmented Golgi Apparatus whereas only about 1% of motor neurons from seven controls with neurologic or systemic disease showed a similar change. Morphometric studies are consistent with the hypothesis that the alteration of the Golgi Apparatus is an early event in the pathogenesis of the neuronal degeneration in ALS. Immunocytochemical studies with antibodies against alpha tubulin, tau, and phosphorylated subunits of neurofilament polypeptides did not disclose differences in the staining of neurons with fragmented or normal Golgi Apparatus, suggesting that the alteration of the organelle is not secondary to a gross lesion of the cytoskeleton. However, these observations do not rule out the hypothesis that the fragmentation of the Golgi Apparatus is secondary to subtle changes of the polypeptides involved in the attachment of membranes of the organelle to the cytoskeleton.
Akihiko Nakano - One of the best experts on this subject based on the ideXlab platform.
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Formation and maintenance of the Golgi Apparatus in plant cells.
International Review of Cell and Molecular Biology, 2014Co-Authors: Tomohiro Uemura, Akihiko NakanoAbstract:Abstract The Golgi Apparatus plays essential roles in intracellular trafficking, protein and lipid modification, and polysaccharide synthesis in eukaryotic cells. It is well known for its unique stacked structure, which is conserved among most eukaryotes. However, the mechanisms of biogenesis and maintenance of the structure, which are deeply related to ER–Golgi and intra-Golgi transport systems, have long been mysterious. Now having extremely powerful microscopic technologies developed for live-cell imaging, the plant Golgi Apparatus provides an ideal system to resolve the question. The plant Golgi Apparatus has unique features that are not conserved in other kingdoms, which will also give new insights into the Golgi functions in plant life. In this review, we will summarize the features of the plant Golgi Apparatus and transport mechanisms around it, with a focus on recent advances in Golgi biogenesis by live imaging of plants cells.
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The Yeast Golgi Apparatus
Traffic, 2011Co-Authors: Yasuyuki Suda, Akihiko NakanoAbstract:The Golgi Apparatus is an organelle that has been extensively studied in the model eukaryote, yeast. Its morphology varies among yeast species; the Golgi exists as a system of dispersed cisternae in the case of the budding yeast Saccharomyces cerevisiae, whereas the Golgi cisternae in Pichia pastoris and Schizosaccharomyces pombe are organized into stacks. In spite of the different organization, the mechanism of trafficking through the Golgi Apparatus is believed to be similar, involving cisternal maturation, in which the resident Golgi proteins are transported backwards while secretory cargo proteins can stay in the cisternae. Questions remain regarding the organization of the yeast Golgi, the regulatory mechanisms that underlie cisternal maturation of the Golgi and transport machinery of cargo proteins through this organelle. Studies using different yeast species have provided hints to these mechanisms.
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Yeast Golgi Apparatus
The Golgi Apparatus, 2008Co-Authors: Akihiko NakanoAbstract:There is no doubt that the budding yeast Saccharomycescerevisiae has played leading roles in elucidating many problems of protein secretion and membrane traffic. The problem of the Golgi Apparatus is not an exception; the yeast system has contributed much, but in a little unique way.
D. J. Morré - One of the best experts on this subject based on the ideXlab platform.
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Golgi Apparatus buds — vesicles or coated ends of tubules?
Protoplasma, 1994Co-Authors: D. J. Morré, T. W. KeenanAbstract:Based on cell-free processing whereby membrane glycoproteins from one cell type were processed by enzymes located in Golgi Apparatus from another cell type, J. Rothman and colleagues postulated that vesicles budding from one Golgi Apparatus stack migrated to and fused with cisternal membranes of other Golgi Apparatus stacks in the cell-free milieu. An extension of this hypothesis was that these same or similar vesicles were involved in the trafficking of membrane material from one cisterna to the next even in the same Golgi Apparatus stack [W. G. Dunphy, J. E. Rothman: Compartmental organization of the Golgi stack. Cell 42: 13–21 (1985)]. A coated bud revealed by tannic acid-containing fixatives was the morphological entity associated with this intercompartment Golgi Apparatus transfer. This report summarizes information from the author's laboratories that suggests that perhaps the majority of these coated buds, while associated with the Golgi Apparatus, are not vesicles per se but rather coated ends of tubules. Golgi Apparatus tubules have been postulated to permit interconnections among adjacent Golgi Apparatus stacks but not to function in transport between contiguous cisternae of the same Golgi Apparatus stack.
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Structure of Golgi Apparatus
Protoplasma, 1994Co-Authors: H.h. Mollenhauer, D. J. MorréAbstract:Golgi Apparatus (GA) of eukaryotic cells consist of one or more stacks of flattened saccules (cisternae) and an array of fenestrae and tubules continuous with the peripheral edges of the saccules. Golgi Apparatus also are characterized by zones of exclusion that surround each stack and by an assortment of vesicles (or vesicle buds) associated with both the stacks and the peripheral tubules of the stack cisternae. Each stack (sometimes referred to as Golgi Apparatus, Golgi complex, or dictyosome) is structurally and functionally polarized, reflecting its role as an intermediate between the endoplasmic reticulum, the cell surface, and the lysosomal system of the cell. There is probably only one GA per cell, and all stacks of the GA appear to function synchronously. All Golgi Apparatus are involved in the generation and movement of product and membrane within the cell or to the cell exterior, and these functions are often reflected as structural changes across the stacks. For example, in plants, both product and membrane appear to maturate from the cis to the trans poles of the stacks in a sequential, or serial, manner. However, there is also strong ultrastructural evidence in plants for a parallel input to the stack saccules, probably through the peripheral tubules. The same modes of functioning probably also occur in animal GA; although here, the parallel mode of functioning almost surely predominates. In some cells at least, GA stacks give rise to tubular-vesicular structures that resemble the trans Golgi network. Rudimentary GA, consisting of tubular-vesicular networks, have been identified in fungi and may represent an early stage of GA evolution.
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Golgi Apparatus isolation and use in cell-free systems
Protoplasma, 1993Co-Authors: D. J. Morré, T. W. Keenan, Dorothy M. MorréAbstract:Recent advances in understanding the molecular mechanisms of membrane traffic to and through the Golgi Apparatus have been predicated in large measure on the use of permeabilized animal cells, and on completely cell-free systems. These systems have included those addressing inter-Golgi Apparatus membrane traffic, endoplasmic reticulum to Golgi Apparatus traffic, and endocytotic events. Development of cell-free systems depends on the use of isolated fractions. Specificity is often achieved by using a compartment-specific assay so that the fractions employed can be very crude. More recently cell-free systems also have evolved which employ highly purified and well-characterized cell fractions. The latter may be utilized in the absence of a compartment-specific assay but may require employment of compartment-specific assays for validation. Central to development of cell-free systems for membrane analysis has been the availability of isolated Golgi Apparatus, first from plants and later from animal tissues and cells. A major advantage of cell-free systems is that they are most clearly amenable to the investigation of molecular mechanisms of membrane trafficking.
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Post Golgi Apparatus structures and membrane removal in plants
Protoplasma, 1991Co-Authors: Hilton H. Mollenhauer, D. J. Morré, Lawrence R. GriffingAbstract:In nongrowing secretory cells of plants, large quantities of membrane are transferred from the Golgi Apparatus to the plasma membrane without a corresponding increase in cell surface area or accumulation of internal membranes. Movement and/or redistribution of membrane occurs also in trans Golgi Apparatus cisternae which disappear after being sloughed from the dictyosome, and in secretory vesicles which lose much of their membrane in transit to the cell surface. These processes have been visualized in freeze-substituted corn rootcap cells and a structural basis for membrane loss during trafficking is seen. It involves three forms of coated membranes associated with the trans parts of the Golgi Apparatus, with cisternae and secretory vesicles, and with plasma membranes. The coated regions of the plasma membrane were predominantly located at sites of recent fusion of secretory vesicles suggesting a vesicular mechanism of membrane removal. The two other forms of coated vesicles were associated with the trans cisternae, with secretory vesicles, and with a post Golgi Apparatus tubular/vesicular network not unlike the TGN of animal cells. However, the trans Golgi network in plants, unlike that in animals, appears to derive directly from the trans cisternae and then vesiculate. The magnitude of the coated membrane-mediated contribution of the endocytic pathway to the formation of the TGN in rootcap cells is unknown. Continued formation of new Golgi Apparatus cisternae would be required to maintain the relatively constant form of the Golgi Apparatus and TGN, as is observed during periods of active secretion.
