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At least 757 records · Page 42Linked to original sources
PubMed1999

Alpha(S1)-casein is required for the efficient transport of beta- and kappa-casein from the endoplasmic reticulum to the Golgi apparatus of mammary epithelial cells.

In lactating mammary epithelial cells, interaction between caseins is believed to occur after their transport out of the endoplasmic reticulum. We show here that, in alpha(S1)-casein-deficient goats, the rate of transport of the other caseins to the Golgi apparatus is highly reduced whereas secretion of whey proteins is not significantly affected. This leads to accumulation of immature caseins in distended rough endoplasmic reticulum cisternae. Casein micelles, nevertheless, were still observed in secretory vesicles. In contrast, no accumulation was found in mammary epithelial cells which lack beta-casein. In mammary epithelial cells secreting an intermediate amount of alpha(S1)-casein, less casein accumulated in the rough endoplasmic reticulum, and the transport of alpha(S1)-casein to the Golgi occurred with kinetics similar to that of control cells. In prolactin-treated mouse mammary epithelial HC11 cells, which do not express alpha(S)-caseins, endoplasmic reticulum accumulation of beta-casein was also observed. The amount of several endoplasmic reticulum-resident proteins increased in conjunction with casein accumulation. Finally, the permeabilization of rough endoplasmic reticulum vesicles allowed the recovery of the accumulated caseins in soluble form. We conclude that optimal export of the caseins out of the endoplasmic reticulum is dependent upon alpha(S1)-casein. Our data suggest that alpha(S1)-casein interacts with the other caseins in the rough endoplasmic reticulum and that the formation of this complex is required for their efficient export to the Golgi.

Acid Phosphatase↗
PubMed2002

Redistribution of membrane proteins between the Golgi apparatus and endoplasmic reticulum in plants is reversible and not dependent on cytoskeletal networks.

We have fused the signal anchor sequences of a rat sialyl transferase and a human galactosyl transferase along with the Arabidopsis homologue of the yeast HDEL receptor (AtERD2) to the jellyfish green fluorescent protein (GFP) and transiently expressed the chimeric genes in tobacco leaves. All constructs targeted the Golgi apparatus and co-expression with DsRed fusions along with immunolabelling of stably transformed BY2 cells indicated that the fusion proteins located all Golgi stacks. Exposure of tissue to brefeldin A (BFA) resulted in the reversible redistribution of ST-GFP into the endoplasmic reticulum. This effect occurred in the presence of a protein synthesis inhibitor and also in the absence of microtubules or actin filaments. Likewise, reformation of Golgi stacks on removal of BFA was not dependent on either protein synthesis or the cytoskeleton. These data suggest that ER to Golgi transport in the cell types observed does not require cytoskeletal-based mechanochemical motor systems. However, expression of an inhibitory mutant of Arabidopsis Rab 1b (AtRab1b(N121I) significantly slowed down the recovery of Golgi fluorescence in BFA treated cells indicating a role for Rab1 in regulating ER to Golgi anterograde transport.

Animals↗
PubMed1984

Reorientation of the microtubule-organizing center and the Golgi apparatus in cloned cytotoxic lymphocytes triggered by binding to lysable target cells.

By immunofluorescence observations with cell couples of cloned murine cytotoxic T lymphocytes (CTL) and target cells, evidence is presented for a rapid reorientation of the microtubule-organizing center (MTOC) and the Golgi apparatus (GA) in the effector cell (but not in the target cell) toward the contact area with the target. The reorientation of the MTOC/GA and the cytotoxic activity of the CTL were inhibited reversibly by nocodazole, a microtubule-disrupting agent. In lectin-formed cell couples of CTL and neuraminidase-treated target cells, the MTOC in essentially all of the CTL was oriented toward the effector-target contact area of a lysable target cell, but was left randomly oriented with a nonlysable target cell. A similar random orientation of the effector-MTOC was also observed in cell couples of cloned natural killer cells and nonlysable targets. These findings indicate that the repositioning of the MTOC and the GA, which is shared by CTL and natural killer cells, is an essential and early event in the onset of the cytolytic mechanism. It is suggested that this reorientation serves the purpose of directing to the bound target cell secretory vesicles derived from the GA that contain cytotoxic substances.

Animals↗
PubMed2006

Increased metabolic activity in nucleus basalis of Meynert neurons in elderly individuals with mild cognitive impairment as indicated by the size of the Golgi apparatus.

In this study, we examined the metabolic activity of nucleus basalis of Meynert (NBM) neurons in individuals clinically diagnosed with no cognitive impairment (NCI, n = 8), mild cognitive impairment (MCI, n = 9), and subjects with moderate Alzheimer disease (AD, n = 7). We used Golgi apparatus (GA) size as a measure of neuronal metabolic activity. Subjects with MCI showed increased NBM metabolic activity; they had significantly more neurons with larger GA size as compared with NCI and AD subjects. In contrast, more NBM neurons with extremely small GA sizes, indicating reduced metabolic activity, were seen in AD. When these cases were classified according to their AD pathology (Braak I-II, III-IV, or V-VI), Braak III-IV subjects showed significantly increased GA sizes, comparable with the increase in clinically diagnosed MCI, whereas in Braak V-VI, GA sizes were dramatically reduced. Of all MCI and NCI subjects with similar Braak III-IV pathology, the MCI subjects again had significantly larger GA sizes. The larger NBM neuronal GA size seen in MCI suggests increased metabolic activity, associated with both the clinical progression from NCI to MCI, and with the early stages of AD pathology.

Aged, 80 and over↗
PubMed1999

A role for Tlg1p in the transport of proteins within the Golgi apparatus of Saccharomyces cerevisiae.

Members of the syntaxin protein family participate in the docking-fusion step of several intracellular vesicular transport events. Tlg1p has been identified as a nonessential protein required for efficient endocytosis as well as the maintenance of normal levels of trans-Golgi network proteins. In this study we independently describe Tlg1p as an essential protein required for cell viability. Depletion of Tlg1p in vivo causes a defect in the transport of the vacuolar protein carboxypeptidase Y through the early Golgi. Temperature-sensitive (ts) mutants of Tlg1p also accumulate the endoplasmic reticulum/cis-Golgi form of carboxypeptidase Y at the nonpermissive temperature (38 degrees C) and exhibit underglycosylation of secreted invertase. Overexpression of Tlg1p complements the growth defect of vti1-11 at the nonpermissive temperature, whereas incomplete complementation was observed with vti1-1, further suggesting a role for Tlg1p in the Golgi apparatus. Overexpression of Sed5p decreases the viability of tlg1 ts mutants compared with wild-type cells, suggesting that tlg1 ts mutants are more susceptible to elevated levels of Sed5p. Tlg1p is able to bind His6-tagged Sec17p (yeast alpha-SNAP) in a dose-dependent manner and enters into a SNARE complex with Vti1p, Tlg2p, and Vps45p. Morphological analyses by electron microscopy reveal that cells depleted of Tlg1p or tlg1 ts mutants incubated at the restrictive temperature accumulate 40- to 50-nm vesicles and experience fragmentation of the vacuole.

Adenosine Triphosphatases↗
PubMed1997

Visualization of Golgi apparatus in methacrylate embedded conifer embryo tissue using the monoclonal antibody JIM 84.

Methacrylate embedding followed by resin removal has been used for the first time to visualize a membrane-associated antigen at the tissue level. Monoclonal antibody JIM 84 was used to stain the Golgi apparatus of gymnosperm (conifer) embryos by light microscope immunocytochemistry. Specificity of labelling was confirmed by electron microscope immunocytochemistry using LR-white resin. GA staining was evident in all stages of white spruce somatic embryo development from immature to mature. Some regions of the somatic embryos (e.g. root cap/suspensor region) stained more vigorously than other regions (hypocotyl/cotyledon end). GA also stained in roots of Monterey pine and Douglas fir. Unlike the situation in most angiosperms, JIM 84 antigen appears to be absent from the conifer plasma membrane. However, it appears to be present in representatives of both major classes of higher plants.

Antibodies, Monoclonal↗
PubMed1998

The golgi apparatus in honeybee photoreceptor cells: structural organization and spatial relationship to microtubules and actin filaments

The architecture of the Golgi complex in honeybee photoreceptors has been analyzed by electron-microscopic techniques. The Golgi apparatus consists of several hundred individual stacks of cisternae dispersed throughout the soma of the photoreceptor cell. Two distinct subpopulations of Golgi stacks are distinguishable by their topographic features: (1) a dense row of Golgi stacks is aligned along the palisade-like cisternae of smooth endoplasmic reticulum backing the photoreceptive microvilli; (2) other Golgi stacks are scattered in the remainder of the cell body. The spatial relationship of Golgi stacks to microtubules and actin filaments has also been determined. Electron-microscopic examination of high-pressure-frozen freeze-substituted retinae reveals that Golgi stacks backing the submicrovillar endoplasmic reticulum reside in a cell area without microtubules, whereas the second subpopulation of Golgi stacks is embedded amidst microtubules. Labeling studies with several actin-specific probes, viz., rhodamine phalloidin, monoclonal anti-actin antibodies, and myosin fragments, provide evidence for a juxtaposition of the submicrovillar Golgi stacks to actin filaments. The Golgi membranes are thus ideally positioned to facilitate the transport of Golgi-derived material toward the microvilli along actin filaments.

Journal Article↗
PubMed1992

Translocation of oxysterol binding protein to Golgi apparatus triggered by ligand binding.

A cDNA encoding a cytoplasmic oxysterol binding protein was expressed at high levels by transfection in animal cells. This protein binds oxysterols such as 25-hydroxycholesterol that regulate sterol metabolism by transcriptional and posttranscriptional effects. In the transfected cells, some of the oxysterol binding protein (OSBP) was distributed diffusely in the cytoplasm, and some was bound to small vesicles near the nucleus, as revealed by indirect immunofluorescence. Upon addition of 25-hydroxycholesterol, most of the OSBP became concentrated in large perinuclear structures that stained with lentil lectin, a protein that stains the Golgi apparatus. The structures that contained OSBP were disrupted by brefeldin A, confirming their identification as Golgi. A mutant OSBP lacking the COOH-terminal oxysterol binding domain localized to the Golgi spontaneously, suggesting that this domain normally occludes the domain that binds to the Golgi and that sterols relieve this occlusion. The previously noted potential leucine zipper sequence in OSBP was not required for Golgi localization, nor was it essential for homodimer formation. We conclude that OSBP is triggered to bind extrinsically to Golgi membranes when it binds oxysterols and speculate that this translocation may play a role in the transport, metabolism, or regulatory actions of oxysterols.

Animals↗
PubMed1999

Ultrastructural pathology of Golgi apparatus of nerve cells in human brain edema associated to brain congenital malformations, tumours and trauma.

The alterations induced by ischemia and anoxia upon smooth endoplasmic membranes are studied in 38 patients with congenital malformations, brain tumours and brain trauma. The effects of vasogenic and cytotoxic brain edema are examined in the Golgi apparatus of nerve and endothelial cells. Samples of cortical biopsies were conventionally processed for transmission electron microscopy. Cortical biopsies were performed according to the basic principles of Helsinki declaration. Slices of 2 to 5 mm were immediately fixed in the surgical room in 4% glutaraldehyde-0.1 M sodium phosphate buffer, pH 7.4 at 4 degrees C, and postfixed in 1% osmium tetroxide in similar buffer. The pathological alterations of the Golgi complex were studied in samples with moderate and severe brain edema. Moderate edema was mainly found in congenital malformations and severe edema in brain trauma and tumours. In some severely edematous neurons, observed in hydrocephalus associated to Arnold-Chiari malformation, small vesicular type Golgi complexes and atrophic ones were observed, characterized mainly by partial or total disappearance of stacked Golgi cisternae and presence of congregated vesicular profiles. In brain trauma and tumours the Golgi complex showed enlargement and fragmentation of the stacked cis- medial- and trans-Golgi cisternae and vacuolization of trans-Golgi network. In addition, an increased formation of Golgi and coated vesicles was observed in the cis- and trans-Golgi regions. Most Golgi and clathrin coated vesicles were observed throughout the cytoplasm suggesting an increased vesicular transport. In severe edema the nerve cell plasma membranes appeared fragmented, presumably due to an interference of the protein insertion process into the plasma membrane. In brain trauma, a hypertrophic Golgi complex was observed in some nerve cells and endothelial cells of cortical capillaries, with increased formation of Golgi and coated vesicles. The ischemia and anoxia associated to the vasogenic and cytotoxic brain edema induced enlargement, fragmentation and disappearance of stacked Golgi cisternae.

Adolescent↗
PubMed1991

A recycling pathway between the endoplasmic reticulum and the Golgi apparatus for retention of unassembled MHC class I molecules.

Assembly of class I major histocompatibility complex (MHC) molecules involves the interaction of two distinct polypeptides (the heavy and light chains) with peptide antigen. Cell lines synthesizing both chains but expressing low levels of MHC class I molecules on their surface as a result of a failure in assembly and transport have been identified. We now report that although the apparent steady-state distribution in these cells of class I molecules is in the endoplasmic reticulum (ER), the molecules in fact are recycled between the ER and Golgi, rather than retained in the ER. This explains the failure of class I molecules to negotiate the secretory pathway. Class I molecules do not seem to be modified by Golgi enzymes, suggesting that the proteins do not reach the Golgi apparatus during recycling. But morphological and subcellular fractionation evidence indicates that they pass through the cis Golgi or a Golgi-associated organelle, which we postulate to be the recycling organelle. This compartment, which we call the 'cis-Golgi network', would thereby be a sorting organelle that selects proteins for return to the ER.

Animals↗
PubMed1996

The human cytomegalovirus UL37 immediate-early regulatory protein is an integral membrane N-glycoprotein which traffics through the endoplasmic reticulum and Golgi apparatus.

The human cytomegalovirus (HCMV) UL37 immediate-early gene is predicted to encode a type I membrane-bound glycoprotein, gpUL37. Following expression of the UL37 open reading frame in vitro, its signals for translocation and N-glycosylation were recognized by microsomal enzymes. Its orientation in the microsomes is that of a type I protein. gpUL37 produced in HCMV-infected human cells was selectively immunoprecipitated by rabbit polyvalent antiserum generated against the predicted unique domains of the UL37 open reading frame and migrated as an 83- to 85-kDa protein. Tunicamycin treatment, which inhibits N-glycosylation, increased the rate of migration of the UL37 protein to 68 kDa, verifying its modification by N-glycosylation in HCMV-infected cells. Consistent with this observation, gpUL37 was found to be resistant to digestion with either endoglycosidase F or H but sensitive to peptide N-glycosidase F digestion. These results suggested that gpUL37 is N-glycosylated and processed in both the endoplasmic reticulum (ER) and the Golgi apparatus. Direct demonstration of passage of gpUL37 through the ER and the Golgi was obtained by confocal microscopy. gpUL37 colocalized with protein disulfide isomerase, a protein resident in the ER, and with a Golgi protein. Subcellular fractionation of HCMV-infected cells demonstrated that gpUL37 is an integral membrane protein. Taken together, our results demonstrate that the HCMV gpUL37 immediate-early regulatory protein is a type I integral membrane N-glycoprotein which traffics through the ER and the Golgi network.

Animals↗
PubMed1990

Cell type-specific post-Golgi apparatus localization of a "resident" endoplasmic reticulum glycoprotein, glucosidase II.

Glucosidase II, an asparagine-linked oligosaccharide processing enzyme, is a resident glycoprotein of the endoplasmic reticulum. In kidney tubular cells, in contrast to previous findings on hepatocytes, we found by light and electron microscopy immunoreactivity for glucosidase II predominantly in post-Golgi apparatus structures. The majority of immunolabel was in endocytotic structures beneath the plasma membrane. Immunoprecipitation confirmed presence of the glucosidase II subunit in purified brush border preparations. Kidney glucosidase II contained species carrying endo H-sensitive, high mannose as well as endo H-resistant oligosaccharide chains. Some species of glucosidase II contained sialic acid. The sialylated species were enzymatically active. This study demonstrates than an enzyme presumed to be a resident of the endoplasmic reticulum may show alternative localizations in some cell types.

Animals↗
PubMed1995

Lowe syndrome, a deficiency of phosphatidylinositol 4,5-bisphosphate 5-phosphatase in the Golgi apparatus.

The oculocerebrorenal syndrome of Lowe (OCRL) is an X-linked disorder characterized by congenital cataracts, renal tubular dysfunction and neurological deficits. The gene responsible for this disorder, OCRL-1, has been cloned and mutations identified in patients. The gene product (ocrl-1) has extensive sequence homology to a 75 kDa inositol polyphosphate 5-phosphatase. We report here that OCRL patients' fibroblasts show no abnormality in inositol polyphosphate 5-phosphatase activity, but are deficient in a phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] 5-phosphatase activity localized to the Golgi apparatus. Direct biochemical diagnosis of this human disease should now be possible. PtdIns(4,5)P2 has been implicated in Golgi vesicular transport through its role in the regulation of ADP-ribosylation factor, phospholipase D and actin assembly in the cytoskeleton. The regulation of PtdIns(4,5)P2 levels by PtdIns(4,5)P2 5-phosphatase may, therefore, be important in the modulation of Golgi vesicular transport. Given that the primary defect in OCRL is a deficiency of a Golgi PtdIns(4,5)P2 phosphatase, we hypothesize that the disorder results from dysregulation of Golgi function and in this way causes developmental defects in the lens and abnormal renal and neurological function.

Cell Line↗
PubMed2003

The human papillomavirus HPV2a E5 protein localizes to the Golgi apparatus and modulates signal transduction.

The low-risk human papillomavirus type 2a (HPV2a) has been found associated with benign skin epithelial tumors and has only been very rarely identified in malignized epithelia. Here we report the identification of the E5 gene of HPV2a and demonstrate that the protein is mainly expressed in the Golgi apparatus of transfected cells, similar to the known high-risk types E5 proteins. Further, we present experimental evidence demonstrating that HPV2a E5, similar to HPV16 E5, is able to modulate EGF-mediated erk1/2 MAP kinase activation and to down-regulate the expression of MHC class I molecules at the plasma membrane. Thus, the E5 gene of at least one cutaneous low-risk HPV type displays similar biological characteristics to those described for the high-risk type HPV16.

Amino Acid Sequence↗
PubMed1995

Global brain ischemia and reperfusion: Golgi apparatus ultrastructure in neurons selectively vulnerable to death.

The neocortex and the hippocampus were examined for lipid peroxidation products and ultrastructural alterations by fluorescence and electron microscopy, respectively, in rats subjected to 10 min of cardiac arrest or 10 min cardiac arrest and either 90 or 360 min reperfusion. Lipid peroxidation products were observed after 90 min reperfusion in the perikarya and proximal dendrites of neocortical pyramidal neurons and in the hippocampal hilar cells and CA1, region; the fluorescence was most intense at the base of the apical dendrite, the region of the Golgi apparatus. After 90 min of reperfusion, the CA1, showed considerable stretches of rough endoplasmic reticulum devoid of ribosomes and the Golgi cisternae were shorter and widely dilated. The neocortex showed similar endoplasmic reticulum changes, but no significant alterations to the Golgi were noted. In addition there were areas where strings of ribosomes appear to be detaching from the endoplasmic reticulum. After 360 min reperfusion in both the neocortex and the hippocampus, the damage appeared more severe. The Golgi was fragmented into vacuoles, membranous whorls had appeared, and dense aggregates of smooth vesicles were seen coalescing with each other and the vacuoles. These observations suggest that early Golgi involvement is a more important marker of lethal injury than ribosome release from the endoplasmic reticulum. The areas of disturbed Golgi ultrastructure correspond to those areas that show evidence of lipid peroxidation and imply that lipid peroxidation may be causally related to the disturbance in Golgi ultrastructure.

Animals↗
PubMed2004

An internal motor kinesin is associated with the Golgi apparatus and plays a role in trichome morphogenesis in Arabidopsis.

Members of the kinesin superfamily are microtubule-based motor proteins that transport molecules/organelles along microtubules. We have identified similar internal motor kinesins, Kinesin-13A, from the cotton Gossypium hirsutum and Arabidopsis thaliana. Their motor domains share high degree of similarity with those of internal motor kinesins of animals and protists in the MCAK/Kinesin13 subfamily. However, no significant sequence similarities were detected in sequences outside the motor domain. In Arabidopsis plants carrying the T-DNA knockout kinesin-13a-1 and kinesin-13a-2 mutations at the Kinesin-13A locus, >70% leaf trichomes had four branches, whereas wild-type trichomes had three. Immunofluorescent results showed that AtKinesin-13A and GhKinesin-13A localized to entire Golgi stacks. In both wild-type and kinesin-13a mutant cells, the Golgi stacks were frequently associated with microtubules and with actin microfilaments. Aggregation/clustering of Golgi stacks was often observed in the kinesin-13a mutant trichomes and other epidermal cells. This suggested that the distribution of the Golgi apparatus in cell cortex might require microtubules and Kinesin-13A, and the organization of Golgi stacks could play a regulatory role in trichome morphogenesis. Our results also indicate that plant kinesins in the MCAK/Kinesin-13 subfamily have evolved to take on different tasks than their animal counterparts.

Actins↗