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At least 649 records · Page 36Linked to original sources
PubMed1988

Identification, by a monoclonal antibody, of a 53-kD protein associated with a tubulo-vesicular compartment at the cis-side of the Golgi apparatus.

Purified Golgi membranes of the human intestinal adenocarcinoma cell line Caco-2 were used as an antigen to produce a monoclonal antibody, G1/93, which specifically labels a tubulovesicular compartment near the cis side of the Golgi apparatus, including the first cis-cisterna itself, as visualized by single and double immunoelectron microscopy with antibodies against galactosyltransferase. The antigen recognized by G1/93 was identified as a protein with a subunit size of 53 kD. Pulse-chase experiments revealed that the 53-kD protein dimerizes immediately after synthesis followed by formation of oligomers of approximately 310 kD, probably homohexamers. The protein has a transmembrane topology with only a short cytoplasmic segment as assessed by protease protection experiments. Glycosidase digestion studies indicated that the protein is probably not glycosylated. The unique subcellular distribution of the G1/93 antigen in close vicinity to the cis-Golgi is in line with the notion that this protein may delineate the biosynthetic transport pathway from the endoplasmic reticulum to the Golgi apparatus. Moreover, G1/93 is a useful marker to identify the cis side of the Golgi apparatus in a variety of human cells.

Antibodies, Monoclonal↗
PubMed1989

The GTP-binding protein Ypt1 is required for transport in vitro: the Golgi apparatus is defective in ypt1 mutants.

The YPT1 gene encodes a raslike, GTP-binding protein that is essential for growth of yeast cells. We show here that mutations in the ypt1 gene disrupt transport of carboxypeptidase Y to the vacuole in vivo and transport of pro-alpha-factor to a site of extensive glycosylation in the Golgi apparatus in vitro. Two different ypt1 mutations result in loss of function of the Golgi complex without affecting the activity of the endoplasmic reticulum or soluble components required for in vitro transport. The function of the mutant Golgi apparatus can be restored by preincubation with wild-type cytosol. The transport defect observed in vitro cannot be overcome by addition of Ca++ to the reaction mixture. We have also established genetic interactions between ypt1 and a subset of the other genes required for transport to and through the Golgi apparatus.

Alleles↗
PubMed1990

Spatial and temporal colocalization of the Golgi apparatus and microtubules rich in detyrosinated tubulin.

The integrity and intracellular distribution of the Golgi apparatus appear to depend upon microtubules. We have found that the microtubules rich in detyrosinated tubulin are located preferentially in the vicinity of the Golgi. Cells were double-stained with antibodies specific for either tyrosinated or detyrosinated tubulin and an antibody to prolactin or wheat germ agglutinin (Golgi markers). Microtubules rich in detyrosinated tubulin showed a close codistribution with the Golgi in three different cultured cell lines GH3, BS-C-1, and AtT20. Disruption of microtubules with nocodazole in GH3 cells resulted in fragmentation and dispersal of the Golgi apparatus as reported previously. During recovery of the microtubules and the Golgi complex after removal of the nocodazole, there was a spatial and temporal colocalization of the Golgi apparatus and microtubules rich in detyrosinated tubulin. Our results suggest that a functional relationship may exist between the structure and organization of the Golgi complex and the detyrosination of alpha-tubulin in microtubules.

Animals↗
PubMed1993

The actin-binding protein comitin (p24) is a component of the Golgi apparatus.

Comitin (p24) was first identified in Dictyostelium discoideum as a membrane-associated protein which binds in gel overlay assays to G and F actin. To analyze its actin-binding properties we used purified, bacterially expressed comitin and found that it binds to F actin in spin down experiments and increases the viscosity of F actin solutions even under high-salt conditions. Immunofluorescence studies, cell fractionation experiments and EM studies of vesicles precipitated with comitin-specific monoclonal antibodies showed that comitin was present in D. discoideum on: (a) a perinuclear structure with tubular or fibrillary extensions; and (b) on vesicles distributed throughout the cell. In immunofluorescence experiments using comitin antibodies NIH 3T3 fibroblasts showed a similar staining pattern as D. discoideum cells. Using bona fide Golgi markers the perinuclear structure was identified as the Golgi apparatus. The results were supported by an electron microscopic study using cryosections. Based on these data we propose that also in Dictyostelium the stained perinuclear structure is the Golgi apparatus. In vivo the perinuclear structure was found to be attached to the actin and the microtubule network. Alteration of the actin network or depolymerization of the microtubules led to its dispersal into vesicles distributed throughout the cell. These results suggest that the Golgi apparatus in D. discoideum is connected to the actin network by comitin. This protein seems also to be present in mammalian cells.

3T3 Cells↗
PubMed1994

Concentration of intracellular hepatic apolipoprotein E in Golgi apparatus saccular distensions and endosomes.

The intrahepatic distribution of apolipoprotein E has been assessed by immunogold labeling of cryosections as well as by Western blotting of organelles isolated from liver homogenates. Both techniques supported the prior analytical fractionation studies of Wong (1989) who concluded that intrahepatic apoE was largely endosomal. All endosomal components decorated by gold particles indicative of apoE antigenicity in cryosections appeared filled with lipoprotein-like particles thereby accounting for this prominent morphological feature of isolated liver endosomes. The distribution of gold particles about the hepatic Golgi apparatus revealed a high content of apoE in closely apposed endosomes, ca. 400 nm in diameter, double labeled for apoE and internalized HRP. Remarkably, apoE (but not internalized HRP) was also observed within saccular distensions of all saccules of stacked Golgi cisternae but absent from the flattened saccular components as was also observed for apoB. This contrasted with albumin, the major secretory protein, which was uniformly distributed throughout the hepatic Golgi apparatus. These observations support a growing body of evidence for intra-Golgi sorting of secretory material in hepatic Golgi apparatus. The lack of any immunoreactive apoE or albumin in small 70-90 nm vesicles about the Golgi cisternae suggests limits to current models of vesicle-mediated intra-Golgi transport.

Albumins↗
PubMed1998

Expression of mutant dynamin inhibits toxicity and transport of endocytosed ricin to the Golgi apparatus.

Endocytosis and intracellular transport of ricin were studied in stable transfected HeLa cells where overexpression of wild-type (WT) or mutant dynamin is regulated by tetracycline. Overexpression of the temperature-sensitive mutant dynG273D at the nonpermissive temperature or the dynK44A mutant inhibits clathrin-dependent endocytosis (Damke, H., T. Baba, A.M. van der Blieck, and S.L. Schmid. 1995. J. Cell Biol. 131: 69-80; Damke, H., T. Baba, D.E. Warnock, and S.L. Schmid. 1994. J. Cell Biol. 127:915-934). Under these conditions, ricin was endocytosed at a normal level. Surprisingly, overexpression of both mutants made the cells less sensitive to ricin. Butyric acid and trichostatin A treatment enhanced dynamin overexpression and increased the difference in toxin sensitivity between cells with normal and mutant dynamin. Intoxication with ricin seems to require toxin transport to the Golgi apparatus (Sandirg, K., and B. van Deurs. 1996. Physiol. Rev. 76:949-966), and this process was monitored by measuring the incorporation of radioactive sulfate into a modified ricin molecule containing a tyrosine sulfation site. The sulfation of ricin was much greater in cells expressing dynWT than in cells expressing dynK44A. Ultrastructural analysis using a ricin-HRP conjugate confirmed that transport to the Golgi apparatus was severely inhibited in cells expressing dynK44A. In contrast, ricin transport to lysosomes as measured by degradation of 125I-ricin was essentially unchanged in cells expressing dynK44A. These data demonstrate that although ricin is internalized by clathrin-independent endocytosis in cells expressing mutant dynamin, there is a strong and apparently selective inhibition of ricin transport to the Golgi apparatus. Also, in cells with mutant dynamin, there is a redistribution of the mannose-6-phosphate receptor.

Biological Transport↗
PubMed1964

CYTOCHEMICAL LOCALIZATION OF ADENOSINE TRIPHOSPHATASE IN THE MITOTIC APPARATUS OF HELA AND SARCOMA 180 TISSUE CULTURE CELLS.

ATPase was localized in distinct regions of the mitotic apparatus of HeLa and Sarcoma 180 tissue culture cells. ATPase was demonstrated in the metaphase spindle of HeLa and Sarcoma 180 cells fixed in cold buffered 2 per cent formalin (pH 6.5 to 6.8) containing 2 x 10(-3)M CaCl(2). A high concentration of ATPase was frequently observed at the poles of the spindle. ATPase was also demonstrated in the interzonal region of both cell types during anaphase. The narrowing of the band of ATPase activity localized in the interzonal region during telophase indicates that ATPase activity is associated with the central spindle. In polar views of Sarcoma 180 cells fixed in cold, unbuffered, 2 per cent formalin, ATPase was frequently localized in granules in the region of the inner circumference of the ring of chromosomes formed at metaphase. ATPase in the mitotic apparatus of HeLa and Sarcoma 180 cells was shown not to be due to non-specific alkaline phosphatase. Mitotic apparatus ATPase in Sarcoma 180 cells was suppressed by an -SH inhibitor.

Adenosine Triphosphatases↗
PubMed1965

THE MITOTIC APPARATUS. PHYSICAL-CHEMICAL FACTORS CONTROLLING STABILITY.

Previous investigations have shown that the mitotic apparatus (MA) can be isolated from dividing sea urchin eggs in water buffered at pH 5.6 and that the addition of 1 M hexanediol to the solution raises the usable pH to 6.4. Long chain glycols appeared to be much more effective than related compounds in increasing the stability of the MA, and the aim of the investigations reported here was to determine the basis of this specificity. These experiments show that this impression of specificity is misleading and that under suitable experimental conditions a variety of compounds can be substituted for the glycols. A number of alcohols will duplicate the action of the glycols in stabilizing the MA at pH 6.4, but they must be used at a similar per cent concentration rather than at a similar molar concentration. Increases in the concentration of alcohol or glycol allow isolation at more alkaline pH values, and a pH-concentration relation for the stability of the MA, covering the range from pH 5.6-8, has been determined. These results indicate that the action of these compounds in stabilizing the mitotic apparatus is non-specific and is similar to their effects on the solubility of proteins. The isolation and stabilization of the mitotic apparatus can thus be viewed as a function of the solubility properties of its constituent proteins, opening a variety of new experimental approaches to this problem.

Animals↗
PubMed1965

FURTHER STUDIES ON CELL DIVISION WITHOUT MITOTIC APPARATUS IN SEA URCHIN EGGS.

A large quantity of paraffin oil, sucrose solution, or sea water was injected into the eggs of the heart urchin Clypeaster japonicus shortly before the onset of the first cleavage. The injected oil became spherical, pushing the mitotic apparatus aside. The sucrose solution mixed with the protoplasm and caused disintegration of the mitotic apparatus, and the sea water formed a vacuole at the center of the cell. In all these cases, cleavage may take place almost normally in spite of the absence of the mitotic apparatus or its displacement within the cell. In some eggs, furrowing may take place when more than fifty per cent of the endoplasm has been replaced with sea water before onset of cleavage.

Animals↗
PubMed1971

Golgi apparatus, GERL, and lysosomes of neurons in rat dorsal root ganglia, studied by thick section and thin section cytochemistry.

New insights into the ultrastructure and phosphatase localizations of Golgi apparatus and GERL, and into the probable origin of lysosomes in the neurons of fetal dorsal root ganglia and the small neurons of adult ganglia have come from studying thick (0.5-1.0 micro) as well as thin (up to 500 A) sections by conventional electron microscopy. Tilting the thick specimens, by a goniometer stage, has helped to increase our understanding of the three-dimensional aspects of the Golgi apparatus and GERL. One Golgi element, situated at the inner aspect of the Golgi stack, displays thiamine pyrophosphatase and nucleoside diphosphatase activities. This element exhibits regular geometric arrays (hexagons) of interconnected tubules without evidence of a flattened portion (saccule or cisterna). In contrast, GERL shows acid phosphatase activity and possesses small cisternal portions and anastomosing tubules. Lysosomes appear to bud from GERL. Osmium deposits, following prolonged osmication, are found in the outer Golgi element. Serial 0.5-micro and thin sections of thiamine pyrophosphatase-incubated material demonstrate that, in the neurons studied, the Golgi apparatus is a continuous network coursing through the cytoplasm. Serial thick sections of acid phosphatase-incubated tissue suggest that GERL is also a continuous structure throughout the cytoplasm. Tubules of smooth endoplasmic reticulum, possibly part of GERL, extend into the polygonal compartments of the inner Golgi element. The possible physiological significance of a polygonal arrangement of a phosphatase-rich Golgi element in proximity to smooth ER is considered. A tentative diagram of the Golgi stack and associated endoplasmic reticulum in these neurons has been drawn.

Acid Phosphatase↗
PubMed2002

GS15 forms a SNARE complex with syntaxin 5, GS28, and Ykt6 and is implicated in traffic in the early cisternae of the Golgi apparatus.

The subcellular localization, interacting partners, and function of GS15, a Golgi SNARE, remain to be established. In our present study, it is revealed that unlike proteins (Bet1 and the KDEL receptor) cycling between the Golgi and the intermediate compartment (IC, inclusive of the ER exit sites), GS15 is not redistributed into the IC upon incubation at 15 degrees C or when cells are treated with brefeldin A. Immuno-electron microscopy (immuno-EM) reveals that GS15 is mainly found in the medial-cisternae of the Golgi apparatus and adjacent tubulo-vesicular elements. Coimmunoprecipitation experiments suggest that GS15 exists in a distinct SNARE complex that contains SNAREs (syntaxin5, GS28, and Ykt6) that are implicated in both ER-to-Golgi and intra-Golgi transport but not with SNAREs involved exclusively in ER-to-Golgi traffic. Furthermore, components of COPI coat can be selectively coimmunoprecipitated with GS15 from Golgi extracts. Overexpression of mutant forms of GS15 affects the normal distribution of cis- and medial-Golgi proteins (GS28, syntaxin 5, and Golgi mannosidase II), whereas proteins of the trans-Golgi and TGN (Vti1-rp2/Vti1a and syntaxin 6) and Golgi matrix/scaffold (GM130 and p115) are less affected. When the level of GS15 is reduced by duplex 21-nt small interfering RNA (siRNA)-mediated knockdown approach, diverse markers of the Golgi apparatus are redistributed into small dotty and diffuse labeling, suggesting an essential role of GS15 in the Golgi apparatus.

Animals↗
PubMed2002

Interorganellar regulation of lysosome positioning by the Golgi apparatus through Rab34 interaction with Rab-interacting lysosomal protein.

We present evidence to suggest the existence of a regulatory pathway for the Golgi apparatus to modulate the spatial positioning of otherwise distantly located lysosomes. Rab34, a new member of the Rab GTPase family, is associated primarily with the Golgi apparatus. Expression of wild-type or GTP-restricted but not GDP-restricted versions of Rab34 causes spatial redistribution of lysosomes from the periphery to the peri-Golgi region. The regulation of lysosomal positioning by Rab34 depends on its association with the membrane mediated by prenylation and its direct interaction with Rab-interacting lysosomal protein (RILP). This biological activity, mediated by Rab34-RILP interaction, is dependent on Lys82 in the switch I region. Our results have uncovered a novel mechanism for the Golgi apparatus to regulate the spatial distribution of another organelle.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Cytosolic phospholipase A2-alpha mediates endothelial cell proliferation and is inactivated by association with the Golgi apparatus.

Arachidonic acid and its metabolites are implicated in regulating endothelial cell proliferation. Cytosolic phospholipase A2-alpha (cPLA2alpha) is responsible for receptor-mediated arachidonic acid evolution. We tested the hypothesis that cPLA2alpha activity is linked to endothelial cell proliferation. The specific cPLA2alpha inhibitor, pyrrolidine-1, inhibited umbilical vein endothelial cell (HUVEC) proliferation in a dose-dependent manner. Exogenous arachidonic acid addition reversed this inhibitory effect. Inhibition of sPLA2 did not affect HUVEC proliferation. The levels of cPLA2alpha did not differ between subconfluent and confluent cultures of cells. However, using fluorescence microscopy we observed a novel, confluence-dependent redistribution of cPLA2alpha to the distal Golgi apparatus in HUVECs. Association of cPLA2alpha with the Golgi was linked to the proliferative status of HUVECs. When associated with the Golgi apparatus, cPLA2alpha activity was seen to be 87% inhibited. Relocation of cPLA2alpha to the cytoplasm and nucleus, and cPLA2alpha enzyme activity were required for cell cycle entry upon mechanical wounding of confluent monolayers. Thus, cPLA2alpha activity and function in controlling endothelial cell proliferation is regulated by reversible association with the Golgi apparatus.

Cell Proliferation↗
PubMed1999

alpha1,3Fucosyltransferase VI is expressed in HepG2 cells and codistributed with beta1,4galactosyltransferase I in the golgi apparatus and monensin-induced swollen vesicles.

The major alpha1,3fucosyltransferase activity in plasma, liver, and kidney is related to fucosyltransferase VI which is encoded by the FUT6 gene. Here we demonstrate the presence of alpha1, 3fucosyltransferase VI (alpha3-FucT VI) in the human HepG2 hepatoma cell line by specific activity assays, detection of transcripts, and the use of specific antibodies. First, FucT activity in HepG2 cell lysates was shown to prefer sialyl-N-acetyllactosamine as acceptor substrate indicating expression of alpha3-FucT VI. RT-PCR analysis further confirmed the exclusive presence of the alpha3-FucT VI transcripts among the five human alpha3-FucTs cloned to date. alpha3-FucT VI was colocalized with beta1,4galactosyltransferase I (beta4-GalT I) to the Golgi apparatus by dual confocal immunostaining. Pulse/chase analysis of metabolically labeled alpha3-FucT VI showed maturation of alpha3-FucT VI from the early 43 kDa form to the mature, endoglycosidase H-resistant form of 47 kDa which was detected after 2 h of chase. alpha3-FucT VI was released to the medium and accounted for 50% of overall cell-associated and released enzyme activity. Release occurred by proteolytical cleavage which produced a soluble form of 43 kDa. Monensin treatment segregated alpha3-FucT VI from the Golgi apparatus to swollen peripheral vesicles where it was colocalized with beta4-GalT I while alpha2,6(N)sialyltransferase remained associated with the Golgi apparatus. Both constitutive secretion of alpha3-FucT VI and its monensin-induced relocation to vesicles analogous to beta4-GalT I suggest a similar post-Golgi pathway of both alpha3-FucT VI and beta4-GalT I.

Animals↗
PubMed1996

Effect of chronic ethanol consumption on glycosylation processes in rat liver microsomes and Golgi apparatus.

Previous studies have demonstrated that acute ethanol intoxication affects various steps of protein glycosylation at the level of rat liver endoplasmic reticulum and Golgi apparatus. The aim of this investigation was to demonstrate whether chronic ethanol intake can induce definitive changes of liver glycoprotein processing. Rats were given ethanol by liquid diet for 8 weeks. At the end of this period the triglyceride levels in liver homogenate and microsomes were significantly higher than in controls. Isolated hepatocytes prelabelled with [3H]Na palmitate and [14C]glucosamine showed a significant storage of the lipid and carbohydrate radioactivity in microsomes and Golgi apparatus and a significant impairment of labelled glycolipoprotein secretion. Changes of the glycosylation steps were observed both in endoplasmic reticulum and in Golgi apparatus: in the former the levels of dolichyl phosphate, which is rate-limiting for the synthesis of glycoprotein, showed a significant reduction; in the latter the activity of the main enzymes responsible for the terminal glycosylation process was significantly decreased. These data suggest that an impairment of glycoprotein maturation may be involved in the pathogenesis of liver injury induced by chronic ethanol intake.

Alcoholism↗
PubMed1978

Biochemical studies on rat liver Golgi apparatus. II. Further characterization of isolated Golgi fraction.

Although the preparation of rat liver Golgi apparatus isolated by our method contains appreciable activities of NADH- and NADPH-cytochrome c reductases and glucose-6-phosphatase, these enzymes as well as thiamine pyrophosphatase of the extensively fragmented Golgi fraction are partitioned in aqueous polymer two-phase systems quite differently from those associated with microsomes. Similarly, the partition patterns of acid phosphatase and 5'-nucleotidase of the Golgi fragments differ from those of homogenized lysosomes and plasma membrane, respectively. It is concluded that most, if not all, of these marker enzymes in the Golgi fraction cannot be ascribed to contamination by the non-Golgi organelles. In sucrose density gradient centrifugation the NADH- and NADPH-cytochrome c reductase activities of the Golgi fraction behave identically with galactosyltransferase but differently from the reductase activities of microsomes, again indicating that the reductases are inherently associated with the Golgi apparatus. NADPH-cytochrome c reductase of the Golgi preparation is immunologically identical with that of microsomes. The marker enzymes mentioned above and galactosyltransferase behave differently from one another when the Golgi fragments are subjected to partitioning in aqueous polymer two-phase systems, suggesting that these enzymes are not uniformly distributed in the Golgi apparatus structure.

Acid Phosphatase↗
PubMedDate not supplied

Clinical features and management of tumors affecting the lacrimal drainage apparatus.

PURPOSE: To report the clinical features of a series of patients with lacrimal drainage apparatus tumors and present guidelines for management based on histopathology. METHODS: A non-comparative retrospective chart review of the clinical, imaging, and pathologic findings of 37 patients presenting to four regional orbital surgery departments with tumors affecting the lacrimal drainage apparatus between 1990 and 2004. RESULTS: There were 37 patients, of whom 62% were male. The mean age at referral was 54 years. Epiphora, a palpable mass, and dacryocystitis were the most common presentations. Two thirds of the tumors were epithelial, with carcinomas being the most frequent (38%), followed by papillomas (27%). Lymphomas were the most common nonepithelial malignancy (30%). Epithelial tumors were more common in men (87%), whereas lymphomas were more common in women (57%). Treatment modalities included surgery, in addition to radiotherapy and/or chemotherapy and immunotherapy. Mean follow-up was 38 months. Thirty-three patients (89%) remain alive without evidence of disease and 4 patients died of recurrence and/or metastases. CONCLUSIONS: Lacrimal drainage apparatus tumors require careful initial management to ensure adequate local and systemic disease control. Atypical mucosa encountered during dacryocystorhinostomy should be biopsied and small papillomas or pedunculated tumors excised and analyzed with frozen sections. If a diffuse or infiltrative mass is encountered, it should be biopsied and managed on the basis of histopathology and extent of disease. Lymphomas should be treated according to protocols, whereas noninvasive carcinoma and extensive papillomas require complete excision of the system. Invasive disease requires en bloc excision. Long-term follow-up is essential for early detection of recurrence.

Adult↗
PubMed2002

A thapsigargin-sensitive Ca(2+) pump is present in the pea Golgi apparatus membrane.

The Golgi apparatus behaves as a bona fide Ca(2+) store in animal cells and yeast (Saccharomyces cerevisiae); however, it is not known whether this organelle plays a similar role in plant cells. In this work, we investigated the presence of an active Ca(2+) accumulation mechanism in the plant cell Golgi apparatus. Toward this end, we measured Ca(2+) uptake in subcellular fractions isolated from the elongating zone of etiolated pea (Pisum sativum) epicotyls. Separation of organelles using sucrose gradients showed a strong correlation between the distribution of an ATP-dependent Ca(2+) uptake activity and the Golgi apparatus marker enzyme, xyloglucan-fucosyltransferase. The kinetic parameters obtained for this activity were: the rate of maximum Ca(2+) uptake of 2.5 nmol mg min(-1) and an apparent K(m) for Ca(2+) of 209 nM. The ATP-dependent Ca(2+) uptake was strongly inhibited by vanadate (inhibitor concentration causing 50% inhibition [I(50)] = 126 microM) and cyclopiazonic acid (I(50) = 0.36 nmol mg protein(-1)) and was not stimulated by calmodulin (1 microM). Addition of Cd(2+) and Cu(2+) at nanomolar concentration inhibited the Ca(2+) uptake, whereas Mn(2+), Fe(2+), and Co(2+) had no significant effect. Interestingly, the active calcium uptake was inhibited by thapsigargin (apparent I(50) = 88 nM), a well-known inhibitor of the endoplasmic reticulum and Golgi sarco-endoplasmic reticulum Ca(2+) ATPase from mammalian cells. A thapsigargin-sensitive Ca(2+) uptake activity was also detected in a cauliflower (Brassica oleracea) Golgi-enriched fraction, suggesting that other plants may also possess thapsigargin-sensitive Golgi Ca(2+) pumps. To our knowledge, this is the first report of a plant Ca(2+) pump activity that shows sensitivity to low concentrations of thapsigargin.

Adenosine Triphosphate↗