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PubMed1983

[Golgi apparatus and T-tubules in cultured myocytes of rat hearts].

The cytochemical-ultrastructural study of rat ventricular cells grown in tissue culture supported the findings of Kasten (1971) on the existence of a special type of Golgi apparatus around the base of the nucleus of the myocardial cell. TPPase and ATPase activity are also found at the subsarcolemmal cisterns and the lateral vesicles of the sarcoplasmic reticulum. Therefore, well developed triads and diads are visible. These structures, however, require the existence of T-tubules in the cultured neonatal myocardial cells. Up to now the presence of T-tubules in early cultures of rat myocytes was still controversy. The demonstration of the T-tubules completes our knowledge of cultured cardiac myocytes and should be taken into consideration in further biochemical and physiological studies with this in vitro model.

Animals↗

PubMed1994

Intracellular dynamics of ricin followed by fluorescence microscopy on living cells reveals a rapid accumulation of the dimeric toxin in the Golgi apparatus.

The intracellular dynamics of fluorescent conjugates of the toxic lectin ricin was followed by video fluorescence microscopy on living CHO cells, demonstrating that the ricin heterodimer and its isolated B chain, after binding to the plasma membrane receptors, migrate to and accumulate in the Golgi apparatus following internalization. A ricin derivative labelled with fluorescein on the A chain and rhodamine on the B chain did not display significant splitting of the A-B heterodimer during translocation of the toxin to the Golgi; this novel finding provides support for the hypothesis that further processing of ricin takes place in this cellular compartment.

Animals↗

PubMed1978

Osmoregulation in the alga Vacuolaria virescens. Structure of the contractile vacuole and the nature of its association with the Golgi apparatus.

The contractile vacuole of the chloromonadophycean alga Vacuolaria virescens is a permanent structure that possesses a specialized membrane: subunits of this membrane have a diameter of 21-24 nm and in places are arranged in a regular hexagonal pattern. The lateral walls of these subunits form regularly spaced bristles or pegs which extend inwards from the trilaminar membrane for a distance of 13-15 nm. The contractile vacuole is situated immediately above an extensive Golgi apparatus that covers most of the anterior surface of the nucleus. Vesicles of Golgi origin give rise to subsidiary vacuoles which in turn empty into the contractile vacuole. Golgi vesicles, subsidiary vacuoles and the contractile vacuole contain similar electron-dense material. It is suggested that this material might be a highly hydrophilic substance which will attract water from the cytoplasm into the Golgi vesicles, subsidiary vacuoles and contractile vacuole from whence it is discharged from the cell. This method of osmoregulation is compared to that occurring in other algae and protozoa.

Chlorophyta↗

PubMedDate not supplied

Golgi apparatus: distinct structure of acid phosphatase localization in regenerating human skeletal muscle fiber.

The localization of acid phosphatase activity has been investigated ultrastructurally in regenerating human fetal skeletal muscle cells. The heavy reaction product was observed in the cisternae of Golgi apparatus and lysosomal vesicles, whereas the slight reaction product was also occasionally found in the nuclear envelope, endoplasmic reticulum and sarcoplasmic reticulum of the regenerating myocytes. The enzymatic basis for these deposits was confirmed by their absence in the incubation of the specimen in substrate-free medium and the enzyme inactivation of the specimen by exposure to NaF or heat.

Acid Phosphatase↗

PubMed1969

Detection of complex carbohydrates in the Golgi apparatus of rat cells.

Two methods used for the electron microscopic detection of glycoproteins were applied to a variety of cell types in the rat; one involved successive treatment of sections with periodic acid, chromic acid, and silver methenamine; and the other, a brief treatment with a chromic acid-phosphotungstic acid mixture. The results obtained with the two methods were identical and, whenever the comparison was possible, similar to those obtained with the periodic acid-Schiff technique of light microscopy. In secretory as well as in nonsecretory cells, parts of the Golgi apparatus are stained. The last saccule on one side of each Golgi stack is strongly reactive (mature face), and the last saccule on the other side shows little or no reactivity (immature face); a gradient of reactivity occurs in between these saccules. The more likely explanation of the increase in staining intensity is that carbohydrate is synthesized and accumulates in saccules as they migrate toward the mature face. In many secretory cells, the mature face is associated with strongly stained secretory granules. Other structures stained are: (1) small vesicles, dense and multivesicular bodies, at least some of which are presumed to be lysosomal in nature; (2) cell coat; and (3) basement membrane. The evidence suggests that the Golgi saccules provide glycoproteins not only for secretion, but also for the needs of the lysosomal system as well as for incorporation into the cell coat and perhaps basement membrane.

Animals↗

PubMed1995

Sorting and retrieval between the endoplasmic reticulum and Golgi apparatus.

The highlight of the past year was the demonstration that retrieval of endoplasmic reticulum membrane proteins containing the di-lysine motif involves COPI coat proteins. Other findings contributed to the debate about the nature of the 'intermediate compartment' between the endoplasmic reticulum and the Golgi apparatus, and the mechanism by which transported proteins are concentrated at this step.

Animals↗

PubMed1997

Confocal analysis of primary cilia structure and colocalization with the Golgi apparatus in chondrocytes and aortic smooth muscle cells.

Detyrosinated and acetylated alpha-tubulins represent a stable pool of tubulin typically associated with microtubules of the centrosome and primary cilium of eukaryotic cells. Although primary cilium-centrosome and centrosome-Golgi relationships have been identified independently, the precise structural relationship between the primary cilium and Golgi has yet to be specifically defined. Confocal immunohistochemistry was used to localize detyrosinated (ID5) and acetylated (6-11B-1) tubulin antibodies in primary cilia of chondrocytes and smooth muscle cells, and to demonstrate their relationship to the Golgi complex identified by complementary lectin staining with wheat germ agglutinin. The results demonstrate the distribution and inherent structural variation of primary cilia tubulins, and the anatomical interrelationship between the primary cilium, the Golgi apparatus and the nucleus. We suggest that these interrelationships may form part of a functional feedback mechanism which could facilitate the directed secretion of newly synthesized connective tissue macromolecules.

Acetylation↗

PubMed1985

Clathrin-immunoreactive sites in the Golgi apparatus are concentrated at the trans pole in polypeptide hormone-secreting cells.

By analogy with receptor-mediated endocytosis, clathrin-coated membrane segments at locations other than at the plasma membrane have been implicated in intracellular membrane transport/sorting. The crucial role of the Golgi apparatus in these processes prompted us to study the distribution at this level of clathrin-immunoreactive sites in various polypeptide hormone-secreting cells. With a polyclonal antibody recognizing the polymerized form of clathrin (structural coats or cages), we found that the Golgi area had the highest degree of specific labeling of various cytoplasmic regions, including the subplasmalemmal web. Moreover, the Golgi labeling was not homogeneously distributed, most of the immunoreactive sites being associated with membrane segments at the trans pole. The labeled membranes comprised regions of trans cisternae with and without condensing secretory material, newly formed (maturing) secretory granules freshly released from trans cisternae, and typical coated vesicles. The cis Golgi cisternae, as well as the cytoplasmic region containing transfer (shuttle) vesicles and transitional cisternae of the rough endoplasmic reticulum, were only weakly labeled. Clathrin concentration, degree of assembly of triskelions into coats, duration of clathrin association with membranes, or presence of a coat protein different from clathrin could account for the low immunoreactivity observed at the cis pole as compared to the trans pole.

Animals↗

PubMed2004

4Pi-microscopy of the Golgi apparatus in live mammalian cells.

We report the applicability of 4Pi-microscopy to live mammalian cells. Controlled interference of the counterpropagating wavefronts is possible despite the slight variations in cellular refractive index. Superresolved 3D-fluorescence imaging is exemplified with the first representation of the Golgi apparatus in a live cell at approximately 100 nm resolution.

Animals↗

PubMed1996

Molecular cloning of the Golgi apparatus uridine diphosphate-N-acetylglucosamine transporter from Kluyveromyces lactis.

The mannan chains of Kluyveromyces lactis mannoproteins are similar to those of Saccharomyces cerevisiae except that they lack mannose phosphate and have terminal alpha1-->2-linked N-acetylglucosamine. The biosynthesis of these chains probably occurs in the lumen of the Golgi apparatus, by analogy to S. cerevisiae. The sugar donors, GDP-mannose and UDP-GlcNAc, must first be transported from the cytosol, their site of synthesis, via specific Golgi membrane transporters into the lumen where they are substrates in the biosynthesis of these mannoproteins. A mutant of K. lactis, mnn2-2, that lacks terminal N-acetylglucosamine in its mannan chains in vivo, has recently been characterized and shown to have a specific defect in transport of UDP-GlcNAc into the lumen of Golgi vesicles in vitro. We have now cloned the gene encoding the K. lactis Golgi membrane UDP-GlcNAc transporter by complementation of the mnn2-2 mutation. The mnn2-2 mutant was transformed with a genomic library from wild-type K. lactis in a pKD1-derived vector; transformants were isolated and phenotypic correction was monitored following cell surface labeling with fluorescein isothiocyanate conjugated to Griffonia simplicifolia II lectin, which binds terminal N-acetylglucosamine, and a fluorescent activated cell sorter. A 2.4-kb DNA fragment was found to restore the wild-type lectin binding phenotype. Upon loss of the plasmid containing this fragment, reversion to the mutant phenotype occurred. The above fragment contained an open reading frame for a multitransmembrane spanning protein of 328 amino acids. The protein contains a leucine zipper motif and has high homology to predicted proteins from S. cerevisiae and C. elegans. In an assay in vitro, Golgi vesicles isolated from the transformant had regained their ability to transport UDP-GlcNAc. Taken together, the above results strongly suggest that the cloned gene encodes the Golgi UDP-GlcNAc transporter of K. lactis.

Amino Acid Sequence↗

PubMed2000

Inositol phosphorylceramide synthase is located in the Golgi apparatus of Saccharomyces cerevisiae.

The plasma membrane of eukaryotic cells differs in lipid composition from most of the internal organelles, presumably reflecting differences in many of its functions. In particular, the plasma membrane is rich in sphingolipids and sterols, one property of which is to decrease the permeability and increase the thickness of lipid bilayers. In this paper, we examine the length of transmembrane domains throughout the yeast secretory pathway. Although the transmembrane domains of cis and medial Golgi residents are similar to those of endoplasmic reticulum proteins, these domains lengthen substantially beyond the medial Golgi, suggesting a thickening of the bilayer. Yeast sphingolipids have particularly long acyl chains, and Aur1p, the inositol phosphorylceramide synthase that initiates yeast sphingolipid synthesis, was found to be located in the Golgi apparatus by both immunofluorescence and membrane fractionation, with its active site apparently in the Golgi lumen. Thus, it appears that sphingolipid synthesis in yeast takes place in the Golgi, separated from glycerophospholipid synthesis in the endoplasmic reticulum. A similar separation has been found in mammalian cells, and this conservation suggests that such an arrangement of enzymes within the secretory pathway could be important for the creation of bilayers of different thickness within the cell.

Amino Acid Sequence↗

PubMed1985

Vesicular transport of newly synthesized opsin from the Golgi apparatus toward the rod outer segment. Ultrastructural immunocytochemical and autoradiographic evidence in Xenopus retinas.

Each day, rod photoreceptors of the vertebrate retina synthesize rhodopsin and insert it into new membranes of the rod outer segment (ROS). The authors determined which components of the rod cell transport opsin from the Golgi to the ROS by a combined EM autoradiographic and immunocytochemical study using radiolabeled amino acid precursors and antiopsin antibodies. Radiolabeled proteins in the ellipsoid region of Xenopus laevis retinal rods were localized by comparison of the distribution of silver grains with the predicted distribution generated by a hypothetical source: grain matrix. Sources of decay were not uniformly distributed. Small vesicles compressed between mitochondria and clustered beneath the connecting cilium that joins the inner to the outer segment contained more than 30% of the radiolabel and had a specific activity 17 times higher than the surrounding cytoplasm. Opsin was localized immunocytochemically on thin sections of retinas embedded in Lowicryl K4M (Polysciences; Warrington, PA) by reaction sequentially with biotinyl-rabbit antifrog opsin, biotinyl-sheep antirabbit F(ab')2, and avidin-ferritin. Golgi apparatus, intermitochondrial vesicles, and vesicles that clustered beneath the connecting cilium were prominently labeled. Subellipsoid smooth endoplasmic reticulum was labeled at background levels. These results demonstrate that intracellular vesicular membranes transport newly synthesized opsin from the Golgi to the base of the connecting cilium of X. laevis retinas. Antibody labeled the outer segment plasma membrane at a 10-fold greater density than the contiguous inner segment plasma membrane. The polarized distribution of opsin apparently involves not only vectorial transport of opsin in the inner segment but also restrictions to the randomization of opsin inserted into the inner and outer segment plasma membrane.

Animals↗

PubMed1980

[Cilia-centriole-Golgi apparatus relationships in the glandular cells of the anterior pituitary of the hedgehog (Erinaceus europaeus L)].

Antehypophysial somatotropic and prolactinic cells of the Hedgehog have isolated cilia composed by a ring of 9 or 8 double tubules with or without a central tubule; this single cilia is in relation with a basal corpuscule. A granulo-filamentous neck joins the basal corpuscule to the subjacent centriole; from this granulo-filamentous neck accompanying the complex basal corpuscule-centriole, microtubules and striated filaments extend towards the Golgi apparatus. The single cilia, probably of chemoreceptor significance, appears in relation with the Golgi complex, a zone of granule formation.

Animals↗

PubMed2000

SNAP-25 is present on the Golgi apparatus of retinal neurons.

SNAP-25 is a neuronal SNARE protein required for synaptic vesicle exocytosis and neurite outgrowth. Here we show that in addition to synaptic staining, SNAP-25 immunoreactivity is also localized to an intracellular, perinuclear compartment of retinal neurons. Double-labeling with an antibody against the 58 kD resident protein of the trans-golgi network indicates that the intracellular SNAP-25 is localized to the Golgi complex. Immuno-electron microscopic localization of SNAP-25 confirmed its presence on the Golgi apparatus of photoreceptors, bipolar cells, amacrine cells and ganglion cells in the retina. These data implicate SNAP-25 in the trafficking of Golgi-derived vesicles in neurons in addition to the synaptic vesicle cycle.

Animals↗

PubMed1977

Relationship between the Golgi apparatus, GERL, and secretory granules in acinar cells of the rat exorbital lacrimal gland.

The method of secretory granuleformation in the acinar cells of the rat exorbital lacrimal gland was studied by electron microscope morphological and cytochemical techniques. Immature secretory granules at the inner face of the Golgi apparatus were frequently attached to a narrow cisternal structure similar to GERL as described in neurons by Novikoff et al. (Novikoff, P. M., A. B. Novikoff, N. Quintana, and J.-J. Hauw. 1971. J. Cell Bio. 50:859-886). In the lacrimal gland. GERL was located adjacent to the inner Golgi saccule, or separated from it by a variable distance. Portions of GERL were often closely paralleled by modified cisternae of rough endoplasmic reticulum (RER), which lacked ribosomes on the surface adjacent to GERL. Diaminobenzidine reaction product of the secretory enzyme peroxidase was localized in the cisternae of the nuclear envelope, RER, peripheral Golgi vesicles, Golgi saccules, and immature and mature secretory granules. GERL was usually free of peroxidase reaction product or contained only a small amount. Thiamine pyrophosphatase reaction product was present in two to four inner Golgi saccules; occasionally, the innermost saccule was dilated and fenestrated, and contained less reaction product than the next adjacent saccule. Acid phosphatase (AcPase) reaction product was present in GERL, immature granules, and, rarely, in the innermost saccule, but not in the rest of the Golgi saccules. Thick sections of AcPase preparations viewed at 100 kV revealed that GERL consisted of cisternal, and fenestrated or tublular portions. The immature granules were attached to GERL by multiple connections to the tublular portions. These results suggest that, in the rat exorbital lacrimal gland, the Golgi saccules participate in the transport of secretory proteins, and that GERL is involved in the formation of secretory granules.

Acid Phosphatase↗

PubMed1992

Formation of secretory granules in the Golgi apparatus of prolactin cells in the rat pituitary gland: a stereoscopic study.

The mode of secretory granule formation in prolactin cells was analyzed in thin or thick sections of pituitary glands from non-lactating or lactating female as well as from male rats. In all these animals, the Golgi apparatus of prolacting cells consists of a continuous twisted ribbon-like structure that branches and anastomoses to form a hollow sphere located in the juxtanuclear area. The early signs of secretory granule formation are observed along the trans-aspect of the Golgi ribbon where progranules appear as focal distensions simultaneously occurring anywhere in the last trans thiamine pyrophosphatase (TPPase)-containing Golgi element. In the transmost Golgi saccule, such dilatations usually contain several nodular masses of electron opaque material which are separated from each other and from the saccular membrane by a less intensely stained material. While this transmost saccule becomes more fenestrated, its focal polynodular distensions seemingly yield polynodular tubular progranules which are initially closely apposed and usually parallel to the trans face of the Golgi ribbon. Subsequently, these progranules, which frequently show small membranous tubules or tubular networks attached to them, are seen some distance from the Golgi stacks and progressively transform into the more compact polymorphous granules characteristic of prolactin cells. These observations suggest that the polynodular tubular progranules arise by fragmentation of portions of the trans-Golgi elements rather than by fusion of small uninodular granules budding from the edges of a trans-Golgi saccule. Once the progranules have been liberated, the rest of the transmost Golgi element appears to break down into small residual networks, tubules, and vesicles. Thus, in prolactin cells as in other glandular cells, the whole transmost Golgi element would fragment during formation of prosecretory granules.

Animals↗

PubMed1993

Glycosylation in Golgi apparatus of early spermatids of rat. A high resolution lectin cytochemical study.

In the present study, lectin cytochemistry in combination with enzyme and chemical treatments and ultrastructural immunocytochemistry were applied to investigate the formation of acrosomal glycoproteins in endoplasmic reticulum (ER) and Golgi apparatus (GA) of early rat spermatids. In addition, the vesicles involved in glycoprotein traffic were investigated using a monoclonal antibody against clathrin. The results obtained suggest the occurrence of high mannose and complex type N-linked oligosaccharides and mucin type O-linked oligosaccharides. In N-linked glycoproteins, Man residues are incorporated into the nascent oligosaccharide in the ER, Fuc residues of the inner core of the oligosaccharide in the cis region of GA, GlcNAc in medial cisternae of GA and Gal residues in the transmost cisternae of GA. In O-linked glycoproteins, the addition of GalNAc occurs in cis and trans cisternae of GA. Gal beta 1,3GalNAc sequence was detected in medial and trans cisternae of GA. Sialic acid was detected in both N- and O-linked oligosaccharides in medial and trans cisternae of GA but not in acrosomes. Immunoreactivity to clathrin was observed in the intermediate zone between ER and GA and in vesicles of the trans side of GA.

Animals↗

PubMed1994

Polarity of processes with Golgi apparatus in a subpopulation of type I astrocytes.

The Golgi apparatus-complex (GA), is a key organelle involved in several posttranslational modifications of polypeptides destined for lysosomes, plasma membranes and secretion. As reported from this laboratory, certain astrocytes in rat brain contain cisternae of the GA not only in perikarya, but also in processes. In order to further investigate which type of astrocytes contain GA in processes we conducted the present study using primary cultures of rat astrocytes and organelle specific antibodies against the GA and the rough endoplasmic reticulum (RER). While the perikarya of all cells contained elements of the GA, only a single process of a subset of type I astrocytes, negative to antibodies A2B5 and HNK-1, contained GA. In contrast, elements of the RER were found within perikarya and all processes. In order to confirm that the immunostained structures in processes indeed represent the GA, we exposed cultures to Brefeldin A (BFA), a secretion blocker which disperses the GA and redistributes it to the RER. We observed that BFA disrupted the GA of both perikarya and processes. However, astrocytes were resistant to prolonged incubations with BFA, while a similar treatment killed cultured fibroblasts and PC-12 cells. Furthermore, in astrocytes exposed to BFA for several days, the delicate network of glial fibrillary acidic protein (GFAP), was replaced by large perinuclear masses of the protein. These observations demonstrate that a subset of type I astrocytes have a single process with elements of the GA. We suggest that this specialization of the GA may be related to yet unrecognized secretory or protein processing functions of these cells. The resistance of astrocytes to BFA and the striking changes in their cytoskeleton induced by the drug, may contribute to studies on the mechanism(s) of action of BFA.

Animals↗