51
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Abstract
Eukaryotic cells use a variety of strategies to inherit the Golgi apparatus. During vertebrate mitosis, the Golgi reorganizes dramatically in a process that seems to be driven by the reversible fragmentation of existing Golgi structures and the temporary redistribution of Golgi components to the endoplasmic reticulum. Several proteins that participate in vertebrate Golgi inheritance have been identified, but their detailed functions remain unknown. A comparison between vertebrates and other eukaryotes reveals common mechanisms of Golgi inheritance. In many cell types, Golgi stacks undergo fission early in mitosis. Some cells exhibit a further Golgi breakdown that is probably due to a mitotic inhibition of membrane traffic. In all eukaryotes examined, Golgi inheritance involves either the partitioning of pre-existing Golgi elements between the daughter cells or the emergence of new Golgi structures from the endoplasmic reticulum, or some combination of these two pathways.
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Affiliation(s)
- O W Rossanese
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA
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52
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Prescott AR, Farmaki T, Thomson C, James J, Paccaud JP, Tang BL, Hong W, Quinn M, Ponnambalam S, Lucocq J. Evidence for prebudding arrest of ER export in animal cell mitosis and its role in generating Golgi partitioning intermediates. Traffic 2001; 2:321-35. [PMID: 11350628 DOI: 10.1034/j.1600-0854.2001.002005321.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
During mitosis the interconnected Golgi complex of animal cells breaks down to produce both finely dispersed elements and discrete vesiculotubular structures. The endoplasmic reticulum (ER) plays a controversial role in generating these partitioning intermediates and here we highlight the importance of mitotic ER export arrest in this process. We show that experimental inhibition of ER export (by microinjecting dominant negative Sar1 mutant proteins) is sufficient to induce and maintain transformation of Golgi cisternae to vesiculotubular remnants during interphase and telophase, respectively. We also show that buds on the ER, ER exit sites and COPII vesicles are markedly depleted in mitotic cells and COPII components Sec23p, Sec24p, Sec13p and Sec31p redistribute into the cytosol, indicating ER export is inhibited at an early stage. Finally, we find a markedly uneven distribution of Golgi residents over residual exit sites of metaphase cells, consistent with tubulovesicular Golgi remnants arising by fragmentation rather than redistribution via the ER. Together, these results suggest selective recycling of Golgi residents, combined with prebudding cessation of ER export, induces transformation of Golgi cisternae to vesiculotubular remnants in mitotic cells. The vesiculotubular Golgi remnants, containing populations of slow or nonrecycling Golgi components, arise by fragmentation of a depleted Golgi ribbon independently from the ER.
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Affiliation(s)
- A R Prescott
- School of Life Sciences, WTB/MSI Complex, University of Dundee, Dundee DD1 5EH, UK
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53
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Jokitalo E, Cabrera-Poch N, Warren G, Shima DT. Golgi clusters and vesicles mediate mitotic inheritance independently of the endoplasmic reticulum. J Cell Biol 2001; 154:317-30. [PMID: 11470821 PMCID: PMC2150754 DOI: 10.1083/jcb.200104073] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
We have examined the fate of Golgi membranes during mitotic inheritance in animal cells using four-dimensional fluorescence microscopy, serial section reconstruction of electron micrographs, and peroxidase cytochemistry to track the fate of a Golgi enzyme fused to horseradish peroxidase. All three approaches show that partitioning of Golgi membranes is mediated by Golgi clusters that persist throughout mitosis, together with shed vesicles that are often found associated with spindle microtubules. We have been unable to find evidence that Golgi membranes fuse during the later phases of mitosis with the endoplasmic reticulum (ER) as a strategy for Golgi partitioning (Zaal, K.J., C.L. Smith, R.S. Polishchuk, N. Altan, N.B. Cole, J. Ellenberg, K. Hirschberg, J.F. Presley, T.H. Roberts, E. Siggia, et al. 1999. Cell. 99:589-601) and suggest that these results, in part, are the consequence of slow or abortive folding of GFP-Golgi chimeras in the ER. Furthermore, we show that accurate partitioning is accomplished early in mitosis, by a process of cytoplasmic redistribution of Golgi fragments and vesicles yielding a balance of Golgi membranes on either side of the metaphase plate before cell division.
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Affiliation(s)
- E Jokitalo
- Institute of Biotechnology, Electron Microscopy Unit, University of Helsinki, 00014 Helsinki, Finland
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54
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Jesch SA, Lewis TS, Ahn NG, Linstedt AD. Mitotic phosphorylation of Golgi reassembly stacking protein 55 by mitogen-activated protein kinase ERK2. Mol Biol Cell 2001; 12:1811-7. [PMID: 11408587 PMCID: PMC37343 DOI: 10.1091/mbc.12.6.1811] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The role of the mitogen-activated protein kinase kinase (MKK)/extracellular-activated protein kinase (ERK) pathway in mitotic Golgi disassembly is controversial, in part because Golgi-localized targets have not been identified. We observed that Golgi reassembly stacking protein 55 (GRASP55) was phosphorylated in mitotic cells and extracts, generating a mitosis-specific phospho-epitope recognized by the MPM2 mAb. This phosphorylation was prevented by mutation of ERK consensus sites in GRASP55. GRASP55 mitotic phosphorylation was significantly reduced, both in vitro and in vivo, by treatment with U0126, a potent and specific inhibitor of MKK and thus ERK activation. Furthermore, ERK2 directly phosphorylated GRASP55 on the same residues that generated the MPM2 phospho-epitope. These results are the first demonstration of GRASP55 mitotic phosphorylation and indicate that the MKK/ERK pathway directly phosphorylates the Golgi during mitosis.
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Affiliation(s)
- S A Jesch
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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55
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Abstract
Here we evaluate the idea that the Golgi is in dynamic equilibrium with the endoplasmic reticulum (ER). In cytoplasts that lack the Golgi apparatus, no regrowth of the Golgi is observed, nor is any transport from the ER to the cell surface detected. However, introduction of the smallest measurable amount of Golgi (equivalent to a few per cent per cell) yields significant exocytic transport. Our results indicate that the steady-state levels of Golgi in the ER are far smaller than the 30% that has been postulated, and that the Golgi may be an independent organelle and not simply an extension of the ER.
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Affiliation(s)
- L Pelletier
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8002, USA
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56
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Hammond AT, Glick BS. Dynamics of transitional endoplasmic reticulum sites in vertebrate cells. Mol Biol Cell 2000; 11:3013-30. [PMID: 10982397 PMCID: PMC14972 DOI: 10.1091/mbc.11.9.3013] [Citation(s) in RCA: 213] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A typical vertebrate cell contains several hundred sites of transitional ER (tER). Presumably, tER sites generate elements of the ER-Golgi intermediate compartment (ERGIC), and ERGIC elements then generate Golgi cisternae. Therefore, characterizing the mechanisms that influence tER distribution may shed light on the dynamic behavior of the Golgi. We explored the properties of tER sites using Sec13 as a marker protein. Fluorescence microscopy confirmed that tER sites are long-lived ER subdomains. tER sites proliferate during interphase but lose Sec13 during mitosis. Unlike ERGIC elements, tER sites move very little. Nevertheless, when microtubules are depolymerized with nocodazole, tER sites redistribute rapidly to form clusters next to Golgi structures. Hence, tER sites have the unusual property of being immobile, yet dynamic. These findings can be explained by a model in which new tER sites are created by retrograde membrane traffic from the Golgi. We propose that the tER-Golgi system is organized by mutual feedback between these two compartments.
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Affiliation(s)
- A T Hammond
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
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57
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Kano F, Nagayama K, Murata M. Reconstitution of the Golgi reassembly process in semi-intact MDCK cells. Biophys Chem 2000; 84:261-8. [PMID: 10852313 DOI: 10.1016/s0301-4622(00)00133-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The Golgi apparatus, which consists of stacks of cisternae during interphase, is fragmented or dispersed throughout the cytoplasm at the onset of mitosis. A sea sponge metabolite, ilimaquinone (IQ), causes Golgi membranes to vesiculate. And after its removal, the vesiculated membranes reassemble into stacks of cisternae in the perinuclear region. To study the mechanism of Golgi membrane dynamics during mitosis, we have reconstituted the reassembly process of IQ-induced vesiculated Golgi membranes in streptolysin O-permeabilized Mardin-Darby canine kidney (MDCK) cells. Monitoring the dynamics of Golgi membranes labeled with a green fluorescence protein (GFP)-tagged protein, we dissected the process into two elementary components: the reassembly of vesiculated Golgi membranes into punctate structures; and the subsequent reformation of these structures into stacks of cisternae near the nucleus. Using morphometric analysis, we studied the kinetics and biochemical requirements for the process, and revealed that an NEM-sensitive factor, cytoplasmic dynein, and GTP binding protein were involved in the Golgi reassembly.
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Affiliation(s)
- F Kano
- Department of Biophysics, Graduate School of Science, Kyoto University, Japan
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58
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Affiliation(s)
- W. James Nelson
- Department of Molecular and Cellular Physiology, Beckman Center for Molecular and Genetic Medicine, Stanford University School of Medicine, Stanford, California 94305-5345
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59
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Abstract
The cis-Golgi matrix protein GM130 is phosphorylated in mitosis on serine 25. Phosphorylation inhibits binding to p115, a vesicle-tethering protein, and has been implicated as an important step in the mitotic Golgi fragmentation process. We have generated an antibody that specifically recognizes GM130 phosphorylated on serine 25, and used this antibody to study the temporal regulation of phosphorylation in vivo. GM130 is phosphorylated in prophase as the Golgi complex starts to break down, and remains phosphorylated during further breakdown and partitioning of the Golgi fragments in metaphase and anaphase. In telophase, GM130 is dephosphorylated as the Golgi fragments start to reassemble. The timing of phosphorylation and dephosphorylation correlates with the dissociation and reassociation of p115 with Golgi membranes. GM130 phosphorylation and p115 dissociation appear specific to mitosis, since they are not induced by several drugs that trigger nonmitotic Golgi fragmentation. The phosphatase responsible for dephosphorylation of mitotic GM130 was identified as PP2A. The active species was identified as heterotrimeric phosphatase containing the Balpha regulatory subunit, suggesting a role for this isoform in the reassembly of mitotic Golgi membranes at the end of mitosis.
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Affiliation(s)
- M Lowe
- Cell Biology Laboratory, Imperial Cancer Research Fund, London WC2A 3PX, United Kingdom.
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60
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Colanzi A, Deerinck TJ, Ellisman MH, Malhotra V. A specific activation of the mitogen-activated protein kinase kinase 1 (MEK1) is required for Golgi fragmentation during mitosis. J Cell Biol 2000; 149:331-9. [PMID: 10769026 PMCID: PMC2175149 DOI: 10.1083/jcb.149.2.331] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/1999] [Accepted: 02/07/2000] [Indexed: 11/22/2022] Open
Abstract
Incubation of permeabilized cells with mitotic extracts results in extensive fragmentation of the pericentriolarly organized stacks of cisternae. The fragmented Golgi membranes are subsequently dispersed from the pericentriolar region. We have shown previously that this process requires the cytosolic protein mitogen-activated protein kinase kinase 1 (MEK1). Extracellular signal-regulated kinase (ERK) 1 and ERK2, the known downstream targets of MEK1, are not required for this fragmentation (Acharya et al. 1998). We now provide evidence that MEK1 is specifically phosphorylated during mitosis. The mitotically phosphorylated MEK1, upon partial proteolysis with trypsin, generates a different peptide population compared with interphase MEK1. MEK1 cleaved with the lethal factor of the anthrax toxin can still be activated by its upstream mitotic kinases, and this form is fully active in the Golgi fragmentation process. We believe that the mitotic phosphorylation induces a change in the conformation of MEK1 and that this form of MEK1 recognizes Golgi membranes as a target compartment. Immunoelectron microscopy analysis reveals that treatment of permeabilized normal rat kidney (NRK) cells with mitotic extracts, treated with or without lethal factor, converts stacks of pericentriolar Golgi membranes into smaller fragments composed predominantly of tubuloreticular elements. These fragments are similar in distribution, morphology, and size to the fragments observed in the prometaphase/metaphase stage of the cell cycle in vivo.
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Affiliation(s)
- Antonino Colanzi
- Department of Biology, Department of Neurosciences, University of California San Diego, La Jolla, California 92093-0347
| | - Thomas J. Deerinck
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, La Jolla, California 92093-0347
| | - Mark H. Ellisman
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, La Jolla, California 92093-0347
| | - Vivek Malhotra
- Department of Biology, Department of Neurosciences, University of California San Diego, La Jolla, California 92093-0347
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61
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Terasaki M. Dynamics of the endoplasmic reticulum and golgi apparatus during early sea urchin development. Mol Biol Cell 2000; 11:897-914. [PMID: 10712508 PMCID: PMC14819 DOI: 10.1091/mbc.11.3.897] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/1999] [Revised: 11/18/1999] [Accepted: 12/29/1999] [Indexed: 11/11/2022] Open
Abstract
The endoplasmic reticulum (ER) and Golgi were labeled by green fluorescent protein chimeras and observed by time-lapse confocal microscopy during the rapid cell cycles of sea urchin embryos. The ER undergoes a cyclical microtubule-dependent accumulation at the mitotic poles and by photobleaching experiments remains continuous through the cell cycle. Finger-like indentations of the nuclear envelope near the mitotic poles appear 2-3 min before the permeability barrier of the nuclear envelope begins to change. This permeability change in turn is approximately 30 s before nuclear envelope breakdown. During interphase, there are many scattered, disconnected Golgi stacks throughout the cytoplasm, which appear as 1- to 2-microm fluorescent spots. The number of Golgi spots begins to decline soon after nuclear envelope breakdown, reaches a minimum soon after cytokinesis, and then rapidly increases. At higher magnification, smaller spots are seen, along with increased fluorescence in the ER. Quantitative measurements, along with nocodazole and photobleaching experiments, are consistent with a redistribution of some of the Golgi to the ER during mitosis. The scattered Golgi coalesce into a single large aggregate during the interphase after the ninth embryonic cleavage; this is likely to be preparatory for secretion of the hatching enzyme during the following cleavage cycle.
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Affiliation(s)
- M Terasaki
- Department of Physiology, University of Connecticut Health Center, Farmington, Connecticut 06032, USA.
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62
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Hauri HP, Kappeler F, Andersson H, Appenzeller C. ERGIC-53 and traffic in the secretory pathway. J Cell Sci 2000; 113 ( Pt 4):587-96. [PMID: 10652252 DOI: 10.1242/jcs.113.4.587] [Citation(s) in RCA: 241] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ER-Golgi intermediate compartment (ERGIC) marker ERGIC-53 is a mannose-specific membrane lectin operating as a cargo receptor for the transport of glycoproteins from the ER to the ERGIC. Lack of functional ERGIC-53 leads to a selective defect in secretion of glycoproteins in cultured cells and to hemophilia in humans. Beyond its interest as a transport receptor, ERGIC-53 is an attractive probe for studying numerous aspects of protein trafficking in the secretory pathway, including traffic routes, mechanisms of anterograde and retrograde traffic, retention of proteins in the ER, and the function of the ERGIC. Understanding these fundamental processes of cell biology will be crucial for the elucidation and treatment of many inherited and acquired diseases, such as cystic fibrosis, Alzheimer's disease and viral infections.
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Affiliation(s)
- H P Hauri
- Department of Pharmacology, Biozentrum, University of Basel, CH-4056 Basel, Switzerland.
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63
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Lippincott-Schwartz J, Roberts TH, Hirschberg K. Secretory protein trafficking and organelle dynamics in living cells. Annu Rev Cell Dev Biol 2000; 16:557-89. [PMID: 11031247 PMCID: PMC4781643 DOI: 10.1146/annurev.cellbio.16.1.557] [Citation(s) in RCA: 349] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Green fluorescent protein chimerae acting as reporters for protein localization and trafficking within the secretory membrane system of living cells have been used in a wide variety of applications, including time-lapse imaging, double-labeling, energy transfer, quantitation, and photobleaching experiments. Results from this work are clarifying the steps involved in the formation, translocation, and fusion of transport intermediates; the organization and biogenesis of organelles; and the mechanisms of protein retention, sorting, and recycling in the secretory pathway. In so doing, they are broadening our thinking about the temporal and spatial relationships among secretory organelles and the membrane trafficking pathways that operate between them.
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Affiliation(s)
- J Lippincott-Schwartz
- Cell Biology and Metabolism Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA.
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64
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Affiliation(s)
- M G Roth
- Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, 75235, USA
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65
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Zaal KJ, Smith CL, Polishchuk RS, Altan N, Cole NB, Ellenberg J, Hirschberg K, Presley JF, Roberts TH, Siggia E, Phair RD, Lippincott-Schwartz J. Golgi membranes are absorbed into and reemerge from the ER during mitosis. Cell 1999; 99:589-601. [PMID: 10612395 DOI: 10.1016/s0092-8674(00)81548-2] [Citation(s) in RCA: 259] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Quantitative imaging and photobleaching were used to measure ER/Golgi recycling of GFP-tagged Golgi proteins in interphase cells and to monitor the dissolution and reformation of the Golgi during mitosis. In interphase, recycling occurred every 1.5 hr, and blocking ER egress trapped cycling Golgi enzymes in the ER with loss of Golgi structure. In mitosis, when ER export stops, Golgi proteins redistributed into the ER as shown by quantitative imaging in vivo and immuno-EM. Comparison of the mobilities of Golgi proteins and lipids ruled out the persistence of a separate mitotic Golgi vesicle population and supported the idea that all Golgi components are absorbed into the ER. Moreover, reassembly of the Golgi complex after mitosis failed to occur when ER export was blocked. These results demonstrate that in mitosis the Golgi disperses and reforms through the intermediary of the ER, exploiting constitutive recycling pathways. They thus define a novel paradigm for Golgi genesis and inheritance.
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Affiliation(s)
- K J Zaal
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Istitutes of Health, Bethesda, Maryland 20892-5430, USA
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66
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Boland MV, Murphy RF. After sequencing: quantitative analysis of protein localization. IEEE ENGINEERING IN MEDICINE AND BIOLOGY MAGAZINE : THE QUARTERLY MAGAZINE OF THE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY 1999; 18:115-9. [PMID: 10497746 DOI: 10.1109/51.790995] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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67
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Abstract
Addition of lipopolysaccharide (LPS) to cells in the form of LPS-soluble (s)CD14 complexes induces strong cellular responses. During this process, LPS is delivered from sCD14 to the plasma membrane, and the cell-associated LPS is then rapidly transported to an intracellular site. This transport appears to be important for certain cellular responses to LPS, as drugs that block transport also inhibit signaling and cells from LPS-hyporesponsive C3H/HeJ mice fail to exhibit this transport. To identify the intracellular destination of fluorescently labeled LPS after its delivery from sCD14 into cells, we have made simultaneous observations of different organelles using fluorescent vital dyes or probes. Endosomes, lysosomes, the endoplasmic reticulum, and the Golgi apparatus were labeled using Texas red (TR)-dextran, LysoTrackertrade mark Red DND-99, DiOC6(3), and boron dipyrromethane (BODIPY)-ceramide, respectively. After 30 min, LPS did not colocalize with endosomes, lysosomes, or endoplasmic reticulum in polymorphonuclear leukocytes, although some LPS-positive vesicles overlapped with the endosomal marker, fluorescent dextran. On the other hand, LPS did appear to colocalize with two markers of the Golgi apparatus, BODIPY-ceramide and TRITC (tetramethylrhodamine isothiocyanate)-labeled cholera toxin B subunit. We further confirmed the localization of LPS in the Golgi apparatus using an epithelial cell line, HeLa, which responds to LPS-sCD14 complexes in a CD14-dependent fashion: BODIPY-LPS was internalized and colocalized with fluorescently labeled Golgi apparatus probes in live HeLa cells. Morphological disruption of the Golgi apparatus in brefeldin A-treated HeLa cells caused intracellular redistribution of fluorescent LPS. These results are consistent with the Golgi apparatus being the primary delivery site of monomeric LPS.
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68
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Shorter J, Warren G. A role for the vesicle tethering protein, p115, in the post-mitotic stacking of reassembling Golgi cisternae in a cell-free system. J Cell Biol 1999; 146:57-70. [PMID: 10402460 PMCID: PMC2199741 DOI: 10.1083/jcb.146.1.57] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During telophase, Golgi cisternae are regenerated and stacked from a heterogeneous population of tubulovesicular clusters. A cell-free system that reconstructs these events has revealed that cisternal regrowth requires interplay between soluble factors and soluble N-ethylmaleimide (NEM)-sensitive fusion protein (NSF) attachment protein receptors (SNAREs) via two intersecting pathways controlled by the ATPases, p97 and NSF. Golgi reassembly stacking protein 65 (GRASP65), an NEM-sensitive membrane-bound component, is required for the stacking process. NSF-mediated cisternal regrowth requires a vesicle tethering protein, p115, which we now show operates through its two Golgi receptors, GM130 and giantin. p97-mediated cisternal regrowth is p115-independent, but we now demonstrate a role for p115, in conjunction with its receptors, in stacking p97 generated cisternae. Temporal analysis suggests that p115 plays a transient role in stacking that may be upstream of GRASP65-mediated stacking. These results implicate p115 and its receptors in the initial alignment and docking of single cisternae that may be an important prerequisite for stack formation.
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Affiliation(s)
- J Shorter
- Cell Biology Laboratory, Imperial Cancer Research Fund, London WC2A 3PX, United Kingdom.
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69
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Lee TH, Linstedt AD. Osmotically induced cell volume changes alter anterograde and retrograde transport, Golgi structure, and COPI dissociation. Mol Biol Cell 1999; 10:1445-62. [PMID: 10233155 PMCID: PMC25298 DOI: 10.1091/mbc.10.5.1445] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Physiological conditions that impinge on constitutive traffic and affect organelle structure are not known. We report that osmotically induced cell volume changes, which are known to occur under a variety of conditions, rapidly inhibited endoplasmic reticulum (ER)-to-Golgi transport in mammalian cells. Both ER export and ER Golgi intermediate compartment (ERGIC)-to-Golgi trafficking steps were blocked, but retrograde transport was active, and it mediated ERGIC and Golgi collapse into the ER. Extensive tubulation and relatively rapid Golgi resident redistribution were observed under hypo-osmotic conditions, whereas a slower redistribution of the same markers, without apparent tubulation, was observed under hyperosmotic conditions. The osmotic stress response correlated with the perturbation of COPI function, because both hypo- and hyperosmotic conditions slowed brefeldin A-induced dissociation of betaCOP from Golgi membranes. Remarkably, Golgi residents reemerged after several hours of sustained incubation in hypotonic or hypertonic medium. Reemergence was independent of new protein synthesis but required PKC, an activity known to mediate cell volume recovery. Taken together these results indicate the existence of a coupling between cell volume and constitutive traffic that impacts organelle structure through independent effects on anterograde and retrograde flow and that involves, in part, modulation of COPI function.
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Affiliation(s)
- T H Lee
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
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70
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Farmaki T, Ponnambalam S, Prescott AR, Clausen H, Tang BL, Hong W, Lucocq JM. Forward and retrograde trafficking in mitotic animal cells. ER-Golgi transport arrest restricts protein export from the ER into COPII-coated structures. J Cell Sci 1999; 112 ( Pt 5):589-600. [PMID: 9973594 DOI: 10.1242/jcs.112.5.589] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protein transport arrest occurs between the ER and Golgi stack of mitotic animal cells, but the location of this block is unknown. In this report we use the recycling intermediate compartment protein ERGIC 53/p58 and the plasma membrane protein CD8 to establish the site of transport arrest. Recycled ERGIC 53/p58 and newly synthesised CD8 accumulate in ER cisternae but not in COPII-coated export structures or more distal sites. During mitosis the tubulovesicular ER-related export sites were depleted of the COPII component Sec13p, as shown by immunoelectron microscopy, indicating that COPII budding structures are the target for mitotic inhibition. The extent of recycling of Golgi stack residents was also investigated. In this study we used oligosaccharide modifications on CD8 trapped in the ER of mitotic cells as a sensitive assay for recycling of Golgi stack enzymes. We find that modifications conferred by the Golgi stack-resident GalNac transferase do occur on newly synthesised CD8, but these modifications are entirely due to newly synthesised transferase rather than to enzyme recycled from the Golgi stack. Taken together our findings establish for the first time that the site of ER-Golgi transport arrest of mitotic cells is COPII budding structures, and they clearly speak against a role for recycling in partitioning of Golgi stack proteins via translocation to the ER.
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Affiliation(s)
- T Farmaki
- Department of Anatomy and Physiology, and Department of Biochemistry, MSI/WTB Complex, Dow Street, University of Dundee, Dundee DD1 4HN, UK
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71
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Abstract
The Golgi complex of mammalian cells is composed of cisternal stacks that function in processing and sorting of membrane and luminal proteins during transport from the site of synthesis in the endoplasmic reticulum to lysosomes, secretory vacuoles, and the cell surface. Even though exceptions are found, the Golgi stacks are usually arranged as an interconnected network in the region around the centrosome, the major organizing center for cytoplasmic microtubules. A close relation thus exists between Golgi elements and microtubules (especially the stable subpopulation enriched in detyrosinated and acetylated tubulin). After drug-induced disruption of microtubules, the Golgi stacks are disconnected from each other, partly broken up, dispersed in the cytoplasm, and redistributed to endoplasmic reticulum exit sites. Despite this, intracellular protein traffic is only moderately disturbed. Following removal of the drugs, scattered Golgi elements move along reassembling microtubules back to the centrosomal region and reunite into a continuous system. The microtubule-dependent motor proteins cytoplasmic dynein and kinesin bind to Golgi membranes and have been implicated in vesicular transport to and from the Golgi complex. Microinjection of dynein heavy chain antibodies causes dispersal of the Golgi complex, and the Golgi complex of cells lacking cytoplasmic dynein is likewise spread throughout the cytoplasm. In a similar manner, kinesin antibodies have been found to inhibit Golgi-to-endoplasmic reticulum transport in brefeldin A-treated cells and scattering of Golgi elements along remaining microtubules in cells exposed to a low concentration of nocodazole. The molecular mechanisms in the interaction between microtubules and membranes are, however, incompletely understood. During mitosis, the Golgi complex is extensively reorganized in order to ensure an equal partitioning of this single-copy organelle between the daughter cells. Mitosis-promoting factor, a complex of cdc2 kinase and cyclin B, is a key regulator of this and other events in the induction of cell division. Cytoplasmic microtubules depolymerize in prophase and as a result thereof, the Golgi stacks become smaller, disengage from each other, and take up a perinuclear distribution. The mitotic spindle is thereafter put together, aligns the chromosomes in the metaphase plate, and eventually pulls the sister chromatids apart in anaphase. In parallel, the Golgi stacks are broken down into clusters of vesicles and tubules and movement of protein along the exocytic and endocytic pathways is inhibited. Using a cell-free system, it has been established that the fragmentation of the Golgi stacks is due to a continued budding of transport vesicles and a concomitant inhibition of the fusion of the vesicles with their target membranes. In telophase and after cytokinesis, a Golgi complex made up of interconnected cisternal stacks is recreated in each daughter cell and intracellular protein traffic is resumed. This restoration of a normal interphase morphology and function is dependent on reassembly of a radiating array of cytoplasmic microtubules along which vesicles can be carried and on reactivation of the machinery for membrane fusion.
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Affiliation(s)
- J Thyberg
- Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institutet, Stockholm, S-171 77, Sweden.
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Affiliation(s)
- B S Glick
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Illinois 60637, USA
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