[Further simplification of the silver impregnation method for detecting the Golgi apparatus].
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Golgi Apparatus↗
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Studies on cartilage. III. The occurrence of collagen within vacuoles of the golgi apparatus.
Electron microscopic observations on chondrocytes from rabbit ear cartilage 72 hours after papain has been given intravenously show that many vacuoles in the Golgi apparatus contain a material with a speckled appearance. Some Golgi vacuoles also contain a material with a banded pattern which can be identified as a collagen. The significance of this observation is discussed.
Animals↗
Rotenone induces disassembly of the Golgi apparatus in the rat dopaminergic neuroblastoma B65 cell line.
It has been reported that the Golgi apparatus (GA) is fragmented in some neurodegenerative diseases. However, the significance of the GA fragmentation or disassembly in neurodegeneration is still obscure. To clarify the involvement of this organelle in apoptosis of neuronal cells, we examined the morphological changes in the GA induced by rotenone, a pesticide that produces selective dopaminergic neurodegeneration. In dopaminergic neuroblastoma B65 cells, a 5-day rotenone treatment (50 nM) promoted cell damage. Rotenone-treated cells showed round nuclei, diffuse signals of the GA and cytosolic redistribution of cytochrome c. Nevertheless, these type of cells without nuclear fragmentation did not show any caspase-3 expression. These results indicate that rotenone induces disassembly of the GA in the early stages of the apoptotic process.
Animals↗
Stacks on tracks: the plant Golgi apparatus traffics on an actin/ER network.
We have visualized the relationship between the endoplasmic reticulum (ER) and Golgi in leaf cells of Nicotiana clevelandii by expression of two Golgi proteins fused to green fluorescent protein (GFP). A fusion of the transmembrane domain (signal anchor sequence) of a rat sialyl transferase to GFP was targeted to the Golgi stacks. A second construct that expressed the Arabidopsis H/KDEL receptor homologue aERD2, fused to GFP, was targeted to both the Golgi apparatus and ER, allowing the relationship between these two organelles to be studied in living cells for the first time. The Golgi stacks were shown to move rapidly and extensively along the polygonal cortical ER network of leaf epidermal cells, without departing from the ER tubules. Co-localization of F-actin in the GFP-expressing cells revealed an underlying actin cytoskeleton that matched precisely the architecture of the ER network, while treatment of cells with the inhibitors cytochalasin D and N-ethylmaleimide revealed the dependency of Golgi movement on actin cables. These observations suggest that the leaf Golgi complex functions as a motile system of actin-directed stacks whose function is to pick up products from a relatively stationary ER system. Also, we demonstrate for the first time in vivo brefeldin A-induced retrograde transport of Golgi membrane protein to the ER.
Actins↗
Studies on scale morphogenesis in the Golgi apparatus of Pyramimonas tetrarhynchus (Prasinophyceae).
Ultrastructural investigations of scale formation in the cisternae of the Golgi apparatus have been carried out on the prasinophycean flagellate Pyramimonas tetrarhynchus, whose cell surfaces are covered with 6 different scale types, 3 on the flagella and 3 on the cell body. Our results suggest that at least 4 and probably all 6 scale types can be formed together within the same cisterna and that there is some degree of intracisternal differentiation, since the formation of 2 scale types (the small underlayer scales on cell body and flagella) is restricted to the cisternal peripheries, whereas the remaining scale types are formed in the more central portions. Detailed studies of morphogenesis of the larger body scales reveal the earliest identifiable stages as 8-armed figures, with 8 thin arms in the intermediate body scales (IBS), and 4 thick and 4 thin arms in the outer body scales (OBS). From these incipients structures that bear little resemblance to the finished products, the complex, 3-dimensional mature body scales are elaborated in each of the cell's 4 distyosomes, and maintain throughout their different developmental sequences a close relationship to the inner surfaces of the cisternal membranes, as well as a particular orientation within the dictyosomes. Preliminary calculations of total numbers of scales that cover cell and flagellar surfaces are included. The small, underlayer scales, which on the flagella are shown to be arranged in 24 rows, number about 350000; larger scales of more complex construction number about 20 000.
Animals↗
INTERCISTERNAL ELEMENTS OF THE GOLGI APPARATUS.
In both vegetative and reproductive cells of various Nitella species, and in cells of other plant genera, there are fine, parallel, elongated elements lying between the cisternae of the Golgi apparatus but not in contact with the cisternal membranes.
Electrons↗
The significance of lamellated structure of Golgi apparatus in parotid acinar cells.
By reviewing briefly our recent study, the functional significance of lamellated structure of the Golgi apparatus (GA) was discussed. We have examined the structural alterations and distribution of Golgi related proteins in GA disorganized by brefeldin A (BFA), okadaic acid (OA), monensin and nocodazole (NOC) by means of electron microscopy. BFA and OA induced rapid disruption of lamellated structure of GA into groups of small vesicles and tubules. The effect of these drugs was reversible, and lamellated structure recovered immediately after withdrawal of the drugs. Immunoelectron microscopy revealed that the localization of amylase, GF-1 antigen (a resident protein of trans membrane of GA) and cathepsin D was modified considerably in the cells whose lamellated structures were in the middle of disorganization or reconstruction. These modifications include appearance of cathepsin D and GF-1 immunoreactivity in the secretory granules. Furthermore, there was evidence that secretory products were discharged not only into the acinar lumen but also into the baso-lateral spaces. In contrast, the stacked configuration was preserved in GA after treatment with monensin or NOC. Localization of immunoreactivity of the Golgi related proteins was essentially not changed by these drugs. These findings suggested that the cisternal stack of GA was the structural background for the normal sorting of secretory proteins.
Animals↗
The Golgi apparatus in the acinar cells of the developing embryonic pancreas: I. Morphology and enzyme cytochemistry.
The Golgi apparatus of pancreatic acinar cells of rat embryos was studied during development from day 13 through day 20 of gestation. The morphological and enzyme cytochemical patterns varied characteristically in the course of cell differentiation. A pronounced system of "rigid lamellae" characterized the area near the trans face of the Golgi stacks in the protodifferentiated and early phases of the differentiated states; by contrast, "rigid lamellae" were sparse in the terminal period of gestation. Reaction product of acid phosphatase labeled the "rigid lamellae" in the protodifferentiated state, was extended across the majority of the stacked cisternae in the early differentiated state, but was restricted to the trans side again in the later periods of cell differentiation. The early phase of the differentiated state was characterized by the tight association of the endoplasmic reticulum and Golgi cisternae on the trans side; the close spatial relationship of the two compartments was lessened after production of secretion granules had started. The findings are in line with those of recent studies on the Golgi organization in some other types of cells in different functional states, and they present the embryonic pancreatic tissue as another model for demonstrating the high flexibility of the Golgi complex. In agreement with the patterns previously found in the absorptive cells of the small intestine, the present results show that the close associations of the endoplasmic reticulum and cisternae of the trans Golgi side predominate in the early stages of cell differentiation.
Animals↗
Synthesis of phosphorylated recognition marker in lysosomal enzymes is located in the cis part of Golgi apparatus.
Rat liver membranes were subjected to centrifugation in a sucrose density gradient in which the Golgi apparatus was separated into several subfractions. Two enzymes involved in the synthesis of the phosphorylated recognition marker in lysosomal enzymes, UDP-N-acetylglucosamine:lysosomal enzyme precursor N-acetylglucosamine-1-phosphotransferase and alpha-N-acetylglucosaminyl phosphodiesterase fractionated with alpha-1,2-mannosidase, a marker enzyme of cis Golgi membranes and differently from galactosyltransferase, a marker enzyme of trans Golgi membranes.
Animals↗
Ethanol-induced effects on expression level, activity, and distribution of protein kinase C isoforms in rat liver Golgi apparatus.
Acute ethanol administration induces significant modifications both in secretive and formative membranes of rat liver Golgi apparatus. The decrease in glycolipoprotein secretion and their retention into the hepatocyte contribute to the pathogenesis of alcohol-induced fatty liver. Molecular and cellular mechanisms behind the ethanol-induced injury of the liver secretory pathway are not yet completely defined. In this study on intact livers from ethanol-treated rats, the involvement of the Golgi compartment in the impairment of hepatic glycolipoprotein secretion has been correlated with changes in the expression level, subcellular distribution and enzymatic activity of protein kinase C (PKC) isoforms. Acute ethanol exposure determined a translocation of classic PKCs and delta isoform from the cytosol to cis and trans Golgi membranes, the site of glycolipoprotein retention in the hepatic cell. A marked stimulation of cytosolic epsilon PKC activity was observed throughout the period of treatment. The presence of activated PKC isozymes at the Golgi compartment of alcohol-treated rat livers may play a role in hepatic secretion and protein accumulation. Direct and indirect effects of ethanol consumption on PKC isozymes and Golgi function are discussed.
Animals↗
Factors controlling the glycosylation potential of the Golgi apparatus.
Most of the biosynthetic reactions that generate the oligosaccharide structures of eukaryotic cells occur in compartments of the Golgi apparatus. This article provides a brief outline of the major glycosylation pathways of the Golgi, and discusses current understanding of the many factors that can control the glycosylation potential of this organelle. Old and new approaches towards elucidating the organization of glycosylation machinery in the Golgi are also considered.
Animals↗
Modulation of the Golgi apparatus in Saccharomyces cerevisiae sec7 mutants as seen by three-dimensional electron microscopy.
The three-dimensional configuration of the Golgi apparatus has been examined with the electron microscope in thick Golgi sections of Saccharomyces cerevisiae prepared from a wild-type strain and from sec7 mutants maintained for various periods of time at the nonpermissive temperature of 37 degrees C and then returned to the permissive temperature of 24 degrees C. Reduced osmium postfixation of glutaraldehyde fixed specimens stained intensely the content of Golgi elements and thus facilitated their three-dimensional characterization. In wild-type S. cerevisiae, the Golgi elements usually appeared as isolated networks of membranous tubules dispersed throughout the cytoplasm. Along such networks, distensions filled with stained material were similar in size to nearby secretory granules, suggesting that the latter formed by fragmentation of the Golgi elements. In sec7 mutants maintained at 37 degrees C in low (0.1%) glucose medium, secretion granules progressively decreased in number and soon disappeared. Concomitantly the networks of Golgi tubules increased in size and complexity, lost their distensions, and then transformed into flattened saccules forming stacks of up to seven or eight saccules that were similar to the Golgi stacks seen in mammalian cells. However in contrast to the latter, connections between the saccules were evident and Golgi-associated small vesicles were generally absent. Following return to the permissive temperature (24 degrees C), secretion granules reappeared, the Golgi stacks progressively decreased in size, and resumed their initial state of separated small tubular networks. Thus in sec7 mutant, grown at 37 degrees C in low glucose medium, segregation of secretory granules is blocked. As a result, Golgi membranes accumulate to form a continuous system of stacked and interconnected saccules.
Cytoplasmic Granules↗
Association of cytoskeletons with the Golgi apparatus: three-dimensional observation and computer-graphic reconstruction.
The association of cytoskeletons with the Golgi apparatus (GA) in cultured 3Y1 cells was investigated by stereo electron microscopy of thick sections and computer-graphic reconstruction of serial thin sections. The 3-dimensional analysis has demonstrated that: 1) both microtubules (MT) and vimentin intermediate filaments (IF) were abundantly present in close vicinity to GA, and some of them were closely associated with GA; and 2) such GA-associated cytoskeletons were attached to GA either at their termini or at their lateral side. The present observations suggest that both MT and vimentin IF are responsible for maintaining the structural integrity of GA.
Animals↗
[Development of Golgi apparatus ultrastructure during meiosis and spermiogenesis in the hamster (Mesocricetus auratus)].
During meiosis and espermiogenesis the Golgi apparatus shows the greatest morphological and physiological changes. During the second meiotic division it appears as a very large organelle, formed by prominent dictyosomes and by two types of vesicles: one in the external part of the body with diameters that range from 40--100 nm, and the other in the central part of the organelle, larger in size, from 200 to 500 nm. The acrosome, once formed, is spheric (1600 nm in diameter) with the glucoproteins forming a round and dense body occupying its central zone. Later the acrosome moves against the nuclear membrane. These morphological changes occur within a very short time, while the spermatid practically continues occupying the same position in the cellular association of the seminiferous tubule.
Animals↗
Selective localization of a Golgi apparatus acid phosphatase isoenzyme in bone using pyridoxal-5'-phosphate.
Substrates commonly used for localizing bone Golgi apparatus (GA) acid phosphatase (AcPase), e.g., beta-glycerophosphate, p-nitrophenylphosphate, cytidine-5'-monophosphate, and di(dicyclohexylammonium)-2-napthylthiolphosphate, give strong staining not only of GA but also of lysosomes. Thiamine pyrophosphate and inosine-5'-monophosphate--substrates that give good GA staining in some soft tissues--give only lysosomal staining in bone. No previously used substrate or substrate-effector combination has selectively localized the GA acid phosphatase in bone. This article describes results using a new AcPase medium having pyridoxal-5'-phosphate (PLP) as substrate. In bone this medium produced strong staining of the osteoblast GA, but relatively little staining of lysosomes, including lysosomes in osteoclasts. The weak lysosomal staining was almost totally eliminated, without affecting the GA reaction, by pretreating the tissue in 0.3% NH3 solution. Conversely, elevated ionic strength of the substrate medium eliminated the GA reaction, while having little effect on lysosomal staining. The GA enzyme was very sensitive to 1 mM tartrate whereas the lysosomal enzyme was not. These differences suggest the presence of distinct isoenzymes in the two locations. The distribution of osteoblasts with stained GA coincided with the distribution of strongest alkaline phosphatase activity and rapid bone mineralization, supporting previous suggestions that osteoblast GA AcPase is involved in the processing of one or more newly synthesized bone matrix components.
Acid Phosphatase↗
Ultrastructural identification of sulphated glycoconjugates in the Golgi apparatus in human colonic absorptive cells.
The subcellular localization of sulphated glycoconjugates was determined at the ultrastructural level by using the high iron diamine (HID) technique for sulphate groups in the absorptive cells of human colonic mucosa. Stained material was observed on the apical plasma membrane, in intracytoplasmic vesicles and in the Golgi complex. In this organelle, the last two or three cisternae of the trans side and the trans-Golgi network (TGN) were labelled, as well as a variable number of coated and noncoated vesicles facing the trans side and surrounding trans-Golgi network. These findings point to the trans side of the Golgi apparatus and trans-Golgi network as the subcompartments functionally involved in the sulphation of glycoconjugates.
Chlorides↗
Syncytia formation induced by coronavirus infection is associated with fragmentation and rearrangement of the Golgi apparatus.
Coronavirus mouse hepatitis virus (MHV) possesses a membrane glycoprotein (M) which is targeted to the Golgi apparatus (GA). We used immunocytochemistry with an organelle-specific antiserum to investigate the morphologic changes of the GA during infection of L2 murine fibroblasts with MHV-A59. Twenty-four hours after infection the GA was fragmented and translocated in the center of syncytia, while the microtubular network was also rearranged displaying radiating elements toward the center of syncytia. Two fusion-defective mutants, which contain an identical amino acid substitution in the cleavage signal sequence of the spike glycoprotein (S), induced fragmentation of the GA. However, the GA migrated only partially to the centers of syncytia during infection with these mutants. Revertant viruses, in which the above mutation was corrected, had fusion properties and GA staining similar to wtMHV-A59. Experiments with brefeldin A (BFA), which induces redistribution of the GA into the rough endoplasmic reticulum (RER), revealed that an intact GA for a period of 4-16 hr postinfection, is required for coronavirus replication and syncytia formation. Thus, during MHV infection, syncytia formation is associated with fragmentation of the GA, followed by a previously undescribed phenomenon of migration of the organelle into the centers of syncytia. The fragmentation of the GA, however, may occur without the formation of syncytia. Therefore, two distinct mechanisms may be responsible for the fragmentation of the GA and its subsequent migration to the center of syncytia.
Animals↗
Vesicular transport and the Golgi apparatus in yeast.
Eukaryotic cells have developed a complex intracellular membrane system to divide the cell into various compartments where specific biochemical reactions are efficiently conducted locally. They also have developed systems to deliver appropriate materials to each specific compartment. Vesicular transport is a delivery system that also links most of the main organelles in the cell. The Golgi apparatus occupies the central position of the traffic between the endoplasmic reticulum and the endosome/vacuole/plasma membrane by maturating and sorting delivery of materials. Every important feature of vesicular transport has been identified by studying the Golgi apparatus, and the unicellular microorganism Saccharomyces cerevisiae has been an extremely excellent material for this study. Cycles of production and consumption of the transport vesicles by sorting the cargo, budding from the donor, tethering, docking and fusion to the target can now be explained to a large extent at the molecular level. The functional and structural aspects of the Golgi have also been well studied in the last decade.
Journal Article↗