scholarly journals A novel, dynein-independent mechanism focuses the endoplasmic reticulum around spindle poles in dividing Drosophila spermatocytes

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Darya Karabasheva ◽  
Jeremy T. Smyth
Keyword(s):  
Endoplasmic Reticulum ◽  
Spindle Poles ◽  
Independent Mechanism

scholarly journals A novel, dynein-independent mechanism focuses the endoplasmic reticulum around spindle poles in dividing Drosophila spermatocytes

2019 ◽  
Author(s):  
Darya Karabasheva ◽  
Jeremy T. Smyth
Keyword(s):  
Endoplasmic Reticulum ◽  
Sudden Onset ◽  
Animal Cells ◽  
Specific Mechanism ◽  
Spindle Poles ◽  
Spindle Apparatus ◽  
Independent Mechanism ◽  
M Phase ◽  
Dividing Cells

AbstractIn dividing animal cells the endoplasmic reticulum (ER) concentrates around the poles of the spindle apparatus by associating with astral microtubules (MTs), and this association is essential for proper ER partitioning to progeny cells. The mechanisms that associate the ER with astral MTs are unknown. Because astral MT minus-ends are anchored by centrosomes at spindle poles, we tested the hypothesis that the MT minus-end motor dynein mediates ER concentration around spindle poles. Live in vivo imaging of Drosophila spermatocytes undergoing the first meiotic division revealed that dynein is required for ER concentration around centrosomes during interphase. In marked contrast, however, dynein suppression had no effect on ER association with astral MTs and concentration around spindle poles in early M-phase. Importantly though, there was a sudden onset of ER-astral MT association in Dhc64C RNAi cells, revealing activation of an M-phase specific mechanism. ER redistribution to spindle poles also did not require non-claret disjunctional (ncd), the other known Drosophila MT minus-end motor, nor Klp61F, a MT plus-end motor that generates spindle poleward forces. Collectively, our results suggest that a novel, M-phase specific mechanism of ER-MT association that is independent of MT minus-end motors is required for proper ER partitioning in dividing cells.

Sterol trafficking between the endoplasmic reticulum and plasma membrane in yeast

2006 ◽  
Vol 34 (3) ◽  
pp. 356-358 ◽  
Author(s):  
D.P. Sullivan ◽  
H. Ohvo-Rekilä ◽  
N.A. Baumann ◽  
C.T. Beh ◽  
A.K. Menon
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Wild Type Strain ◽  
Binding Pocket ◽  
Oxysterol Binding Protein ◽  
Sterol Transport ◽  
Transport Cycle ◽  
Independent Mechanism

We recently showed that transport of ergosterol from the ER (endoplasmic reticulum) to the sterol-enriched PM (plasma membrane) in yeast occurs by a non-vesicular (Sec18p-independent) mechanism that results in the equilibration of sterol pools in the two organelles [Baumann, Sullivan, Ohvo-Rekilä, Simonot, Pottekat, Klaassen, Beh and Menon (2005) Biochemistry 44, 5816–5826]. To explore how this occurs, we tested the role of proteins that might act as sterol transporters. We chose to study oxysterol-binding protein homologues (Osh proteins), a family of seven proteins in yeast, all of which contain a putative sterol-binding pocket. Recent structural analyses of one of the Osh proteins [Im, Raychaudhuri, Prinz and Hurley (2005) Nature (London) 437, 154–158] suggested a possible transport cycle in which Osh proteins could act to equilibrate ER and PM pools of sterol. Our results indicate that the transport of newly synthesized ergosterol from the ER to the PM in an OSH deletion mutant lacking all seven Osh proteins is slowed only 5-fold relative to the isogenic wild-type strain. Our results suggest that the Osh proteins are not sterol transporters themselves, but affect sterol transport in vivo indirectly by affecting the ability of the PM to sequester sterols.

scholarly journals Endoplasmic Reticulum Stress Induces Apoptosis by an Apoptosome-dependent but Caspase 12-independent Mechanism

2005 ◽  
Vol 281 (5) ◽  
pp. 2693-2700 ◽  
Author(s):  
Federica Di Sano ◽  
Elisabetta Ferraro ◽  
Roberta Tufi ◽  
Tilmann Achsel ◽  
Mauro Piacentini ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Caspase 12 ◽  
Independent Mechanism

scholarly journals Microtubules are necessary for proper Reticulon localization during mitosis

2019 ◽  
Author(s):  
Zane J. Bergman ◽  
Ulises Diaz ◽  
Amanda Sims ◽  
Blake Riggs
Keyword(s):  
Endoplasmic Reticulum ◽  
Neurodegenerative Disorders ◽  
Early Embryo ◽  
Drosophila Embryo ◽  
Microtubule Cytoskeleton ◽  
Spindle Poles ◽  
And Function ◽  
Insight Into

AbstractDuring mitosis, the structure of the Endoplasmic Reticulum (ER) displays a dramatic reorganization and remodeling event, however the mechanism driving these changes is poorly understood. Recently, the Reticulon family of ER shaping proteins has been identified as possible factors to promote these drastic changes in ER morphology. In addition, the Reticulons and other ER shaping proteins have been directly linked to several hereditary neurodegenerative disorders. Here, we provide key insight into the cytoskeletal factors involved in the Drosophila Reticulon, Reticulon-like 1 (Rtnl1) during mitosis in the early embryo. At prometaphase, Rtnl1 localizes at the spindle poles just prior to the bulk of ER localization suggesting a role in recruitment. Using precise temporal injections of cytoskeletal inhibitors in the early syncytial Drosophila embryo, we show that microtubules, not microfilaments are necessary for proper Rtnl1 localization and function during mitosis. Lastly, we show that astral microtubules are necessary for Rtnl1 localization at the spindle poles early in mitosis. This work highlights the role of the microtubule cytoskeleton in Rtnl1 localization and ER dynamics during mitosis and sheds light on a pathway towards inheritance of this major organelle.

Mitosis and septum formation in the basidiomycete Helicobasidium mompa

1986 ◽  
Vol 64 (1) ◽  
pp. 130-145 ◽  
Author(s):  
Timothy M. Bourett ◽  
David J. McLaughlin
Keyword(s):  
Endoplasmic Reticulum ◽  
Functional Significance ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Multivesicular Bodies ◽  
Spindle Poles ◽  
Astral Microtubule ◽  
Pole Body ◽  
Helicobasidium Mompa ◽  
Spindle Elongation

Mitosis in clampless, dikaryotic hyphae of Helicobasidium mompa (Basidiomycota, Auriculariales sensu lato) was studied in apical and penultimate cells by correlating light microscopic and ultrastructural observations. Mitosis lasts about 10.5 min. In penultimate cells, mitosis occurs in the base of a branch whose initiation involves rupture of the wall. The extranuclear interphase spindle pole body contains two three-layered discs. Prophase is discerned by the polarization of the nucleus into a karyokinetic and a nucleolar region. During prometaphase, the spindle pole body discs move into the plane of the nuclear envelope where they occupy gaps. The spindle pole is enclosed by a cap of endoplasmic reticulum. At metaphase, nuclei lie side by side, the nucleolus resides in a nuclear evagination, and the spindle pole body discs are five layered. At anaphase, both chromatin to pole movement and extensive spindle elongation occur, astral microtubule populations reach a maximum, and multivesicular bodies aggregate at the spindle poles. Septa contain simple pores and form at the site previously occupied by the dividing nuclei. The results are compared with mitotic cycles in higher fungi and their evolutionary, phylogenetic, and functional significance is discussed.

scholarly journals Ricin B Chain Targeted to the Endoplasmic Reticulum of Tobacco Protoplasts Is Degraded by a CDC48- and Vacuole-independent Mechanism

2008 ◽  
Vol 283 (48) ◽  
pp. 33276-33286 ◽  
Author(s):  
Kerry L. Chamberlain ◽  
Richard S. Marshall ◽  
Nicholas A. Jolliffe ◽  
Lorenzo Frigerio ◽  
Aldo Ceriotti ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Tobacco Protoplasts ◽  
Independent Mechanism

Celecoxib Inhibits Interleukin-12 αβ and β2 Folding and Secretion by a Novel COX2-Independent Mechanism Involving Chaperones of the Endoplasmic Reticulum

2006 ◽  
Vol 69 (5) ◽  
pp. 1579-1587 ◽  
Author(s):  
Iraide Alloza ◽  
Andy Baxter ◽  
Qian Chen ◽  
Rune Matthiesen ◽  
Koen Vandenbroeck
Keyword(s):  
Endoplasmic Reticulum ◽  
Interleukin 12 ◽  
Independent Mechanism

Structural relations between nucleus and cytoplasm during mitosis in Nicotiana tabacum mesophyll

1969 ◽  
Vol 47 (4) ◽  
pp. 581-591 ◽  
Author(s):  
Katherine Esau ◽  
Robert H. Gill
Keyword(s):  
Endoplasmic Reticulum ◽  
Nicotiana Tabacum ◽  
Nuclear Envelope ◽  
Osmium Tetroxide ◽  
Ultrastructural Level ◽  
Early Prophase ◽  
Nuclear Region ◽  
Spindle Poles ◽  
Nicotiana Tabacum L ◽  
Cytoplasmic Ribosomes

The changes in relation between the nucleus and the cytoplasm associated with mitosis were explored at the ultrastructural level in the mesophyll of Nicotiana tabacum L. The material was fixed in glutaraldehyde – formaldehyde – osmium tetroxide. During interphase and early prophase the nucleoplasm can be distinguished from the cytoplasm by its lack of granules comparable to those interpreted as ribosomes in the cytoplasm. After the nuclear envelope is disrupted the nuclear region shows a population of ribosomes identical with that in the cytoplasm, that is, the nucleoplasm and the cytoplasm become indistinguishable. The nuclear envelope differs from the endoplasmic reticulum located in the cytoplasm by the presence of pores. Pieces of the disrupted nuclear envelope assume the same appearance as the endoplasmic reticulum although they remain localized around the nuclear region until metaphase. Eventually the remnants of the envelope are carried to the spindle poles and serve as a source of envelopes for the daughter nuclei. The larger organelles are excluded from the nuclei during development of their envelopes but units of endoplasmic reticulum and apparently some cytoplasmic ribosomes become trapped among the chromosomes. Later, the extranuclear components disappear, probably by being disassembled.

scholarly journals On the Mechanisms Underlying the Secretion and Export of Translationally Controlled Tumor Protein/Histamine Releasing Factor (TCTP/HRF)

2012 ◽  
Vol 5 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Jeehye Maeng ◽  
Miyoung Kim ◽  
Kyunglim Lee
Keyword(s):  
Endoplasmic Reticulum ◽  
Inflammatory Mediators ◽  
Transmembrane Protein ◽  
Cell Types ◽  
Current Understanding ◽  
Secreted Protein ◽  
Translationally Controlled Tumor Protein ◽  
Extracellular Milieu ◽  
Independent Mechanism ◽  
Available Information

Numerous studies have demonstrated that TCTP/HRF is a unique cytokine, modulating the release of inflammatory mediators from various cell types including cells involved in allergic phenomena. Despite the absence of a leader sequence in its NH2-terminus, TCTP/HRF is regarded as a secreted protein found outside of cells as well as in fluids from allergic patients and parasitic organisms. Recent studies clarified several potential mechanisms leading to its secretion. For example, these studies showed that TCTP/HRF is exported from cells via a non-classical, endoplasmic reticulum (ER)/Golgi-independent mechanism associated with exosomal transport. TSAP6, a p53-inducible transmembrane protein, has been shown to enhance exosome production, and facilitate the secretion of TCTP/HRF into extracellular milieu. Additionally, H,K-ATPase also appears to play a role in the transport of TCTP/HRF, since inhibitors of H,K-ATPase also inhibit TCTP/HRF exit. The exact mechanisms involved in TCTP/HRF secretion has not yet emerged. Here we attempted to collate the available information in the current understanding of the mechanisms underlying the release of TCTP/HRF and of the factors that seem to influence these mechanisms.

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