Role of Endoplasmic Reticulum and Golgi Apparatus in the Biosynthesis of Plasma Glycoproteins

Molnár, J.

doi:10.1007/978-1-4684-2655-7_10

Cited by 15 publications

(11 citation statements)

References 178 publications

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“…The current view of the glycosylation stages in the maturation of an asparagine-linked glycoprotein is that N-acetylglucosamine, mannose, and glucose residues are initially added to the growing polypeptide at the site of its synthesis in the cisternae of rough endoplasmic reticulum (12,18,22,23) . Thereafter, the core region is processed in the Golgi apparatus : glucose and some mannose residues are removed, and all the terminal sugars are added to the glycopeptide, namely, N-acetylglucosamine, galactose, fucose, and sialic acids (cf.…”

Section: Resultsmentioning

confidence: 99%

Subcellular compartmentalization of saccharide moieties in cultured normal and malignant cells.

Virtanen¹,

Ekblom²,

Laurila³

1980

The Journal of Cell Biology

258

140

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We studied subcellular localization of saccharide moieties in cultured normal and malignant cells fixed in paraformaldehyde and treated with a nonionic detergent, using lectins specific for various sugar residues as probes in fluorescence microscopy. In normal cells, concanavalin A and Lens culinaris agglutinin, specific for mannose-rich carbohydrate cores in glycoproteins, labeled the endoplasmic reticulum as a wide perinuclear region . Other lectins, on the other hand, stained the Golgi apparatus as a juxtanuclear reticular structure . A similar compartmentalization was also seen in all malignant cells studied, although the Golgi apparatus in these cells was distinctly vesicular in appearance . Our results indicate that saccharide moieties in both normal and malignant cells are similarly compartmentalized, and thus speak in favor of a unidirectional subcellular flow for both membrane and secreted glycoconjugates .

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Section: Resultsmentioning

confidence: 99%

Subcellular compartmentalization of saccharide moieties in cultured normal and malignant cells.

Virtanen¹,

Ekblom²,

Laurila³

1980

The Journal of Cell Biology

258

140

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“…In other tissues, the enzymes involved in posttranslational processing of membrane and secretory proteins are located in specific organelles, such as the rough endoplasmic reticulum or the Golgi apparatus (6,7). If normal transport and processing occurs in AtT-20 cells, it should be possible to use ACTH processing activities to monitor transport between intracellular compartments or as biochemical markers for the corresponding organelles.…”

mentioning

confidence: 99%

Secretory granules of an anterior pituitary cell line, AtT-20, contain only mature forms of corticotropin and beta-lipotropin.

Gumbiner¹,

Kelly²

1981

Proc. Natl. Acad. Sci. U.S.A.

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The pituitary cell line, AtT-20, synthesizes the precursor to corticotropin (adrenocorticotropic hormone; ACTH) and 13-endorphin and correctly glycosylates and cleaves it to make the mature forms of the hormones before they are secreted. This cell line was used to study the intracellular transport, packaging, and secretion of these hormones. Secretory granules from the cells were isolated by homogenization and differential centrifugation and isopycnic sedimentation on a 2H20-Ficoll gradient to give a preparation having a specific activity of 90 ,.g ACTH per mg of protein, which is 30-to 90-fold greater than that of whole cells. The granules have density characteristics and a sedimentation coefficient that are appropriate for spheres of 1000 A radius. They contain all of the fragments of the initial ACTH/endorphin precursor but almost undetectable amounts of the intact precursor. The fragments constitute about 50% of the protein in the secretory granule fraction and, from density measurements, we estimate that they are present in -60,000 copies per vesicle. The cell line secretory granules appear, therefore, to be similar to mature secretory granules in normal differentiated tissues. ACTH first appears in the secretory granule at 30-45 min after synthesis. Cleavage of the precursor to mature ACTH occurs at about the same time in the whole cell. Therefore, proteolysis of the prohormone to ACTH and to P-lipotropin is a metabolic event that can be correlated with the packaging of the hormone into a mature secretory granule. Cleavage of f-lipotropin to (3-endorphin occurs later, probably in the secretory granule.Morphological studies of highly differentiated secretory tissues such as the pancreas and the parotid gland have delineated the intracellular route oftransport ofproteins destined for secretion (1). Secretory proteins are synthesized at the rough endoplasmic reticulum, transported to the Golgi apparatus or the condensing vacuole for packaging into mature secretory granules, and then discharged from the cell by exocytosis. The molecular events underlying this process are poorly understood. It is not known how the secretory proteins are segregated and packaged into secretory granules or how specific granule membrane components are acquired. The nature of the recognition event whereby appropriate membranes fuse during transport and secretion remains obscure.Highly structured tissues such as the pancreas are optimal for morphological studies, but the use of cell lines for the study of biochemical processes is advantageous-e.g., a cell line that retains normal secretory functions could be used to study the molecular events involved in packaging and secretion of proteins. We chose the mouse pituitary cell line AtT-20 as a model secretory system because these cells retain many important biochemical and physiological properties of pituitary corticotrophs. The biosynthetic pathways of the major secretory products-corticotropin (adrenocorticotropic hormone; ACTH), ,B-lipotropin (f3-LPH), and B-endorphin, in th...

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“…and fucose appear to the attached to thyroglobulin and many other glycoproteins only within the Golgi apparatus (5,8). and fucose appear to the attached to thyroglobulin and many other glycoproteins only within the Golgi apparatus (5,8).…”

mentioning

confidence: 99%

“…It then migrates via the smooth surface membrane to the Golgi apparatus where terminal sugars such as sialic acid are attached. Glycosylation may be essential for their migration within the cell (5). Various steps in melanosome formation in particular, the steps from tyrosinase biosynthesis to the formation of the Golgi vesicle, are not as yet clarified.…”

mentioning

confidence: 99%

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Electrophoretic Profile of Tyrosinase Treated With Neuraminidase in Various Subcellular Fractions From Mouse Melanoma*

Tomita

Moro

Seiji

1979

The Journal of Dermatology

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When various subcellular particles of Harding‐Passey mouse melanoma including rough and smooth surface membranes, the Golgi rich fraction and the melanosome fraction were subjected to polyacrylamide gel electrophoresis, the electrophoretic profiles of tyrosinase [EC 1. 14. 18. 1] in all these particles varied depending on the particles, but they became almost identical after the various cell particles were treated with neuraminidase [EC 3. 2. 1. 18]. This appears to suggest that tyrosinases which occur not only in melanosomes and the Golgi apparatus but also in rough and smooth surface membranes possess sugars containing sialic acid residues that can be removed by neuraminidase.

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Role of Endoplasmic Reticulum and Golgi Apparatus in the Biosynthesis of Plasma Glycoproteins

Cited by 15 publications

References 178 publications

Subcellular compartmentalization of saccharide moieties in cultured normal and malignant cells.

Subcellular compartmentalization of saccharide moieties in cultured normal and malignant cells.

Secretory granules of an anterior pituitary cell line, AtT-20, contain only mature forms of corticotropin and beta-lipotropin.

Electrophoretic Profile of Tyrosinase Treated With Neuraminidase in Various Subcellular Fractions From Mouse Melanoma*

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