A novel structural component of the Dictyostelium centrosome

1996 ◽  
Vol 109 (13) ◽  
pp. 3103-3112 ◽  
Author(s):  
A. Kalt ◽  
M. Schliwa
Keyword(s):  
Mitotic Spindle ◽  
Structural Component ◽  
Myosin Ii ◽  
Live Cells ◽  
Microtubule Organizing Center ◽  
Direct Role ◽  
Cytoplasmic Microtubule ◽  
Interphase Cells ◽  
Organizing Center

The microtubule-organizing center of D. discoideum is a nucleus-associated body (NAB) that consists of a multilayered, box-shaped core embedded in an amorphous corona from which the microtubules emerge. The composition of the NAB is still largely unresolved. Here we have examined a high molecular mass component of the NAB which was identified by a monoclonal antibody raised against isolated nucleus/NAB complexes. This antibody recognized a 350 kDa component which is immunologically related to the D. discoideum heavy chain of myosin II. The 350 kDa antigen was localized only at the NAB in interphase cells, while in mitotic cells it may also be found in the vicinity of the NAB as well as in association with the mitotic spindle. Immunogold labeling experiments showed that the protein is part of the NAB corona. This association was not destroyed by treatment with 2 M urea or 0.6 M KCl. The 350 kDa antigen was part of the thiabendazole-induced cytoplasmic microtubule-organizing centers. A direct role in the polymerization of tubulin could not be determined in an in vitro microtubule nucleation assay, whereas antibody electroporation of live cells appeared to interfere with the generation of a normal microtubule system in a subset of cells. Our observations suggest that the 350 kDa antigen is a structural component of the NAB corona which could be involved in its stabilization.

The Role of the Centrosome in Development and Progression of Breast Cancer

2001 ◽  
Vol 7 (S2) ◽  
pp. 582-583
Author(s):  
W. Lingle ◽  
J. Salisbury ◽  
S. Barrett ◽  
V. Negron ◽  
C. Whitehead
Keyword(s):  
Mitotic Spindle ◽  
Mammalian Cells ◽  
Microtubule Organizing Center ◽  
Daughter Cells ◽  
Spindle Poles ◽  
Sister Chromatids ◽  
Close Proximity ◽  
Interphase Cells ◽  
Organizing Center

The centrosome is the major microtubule organizing center in most mammalian cells, and as such it determines the number, polarity, and spatial distribution of microtubules (MTs). Interphase MTs, together with actin and intermediate filaments, constitute the cell's cytoskeleton, which dynamically maintains cell polarity and tissue architecture. Interphase cells begin Gl of the cell cycle with one centrosome. During S phase, the centrosome duplicates concomitantly with DNA replication. Duplicated centrosomes usually remain in close proximity to one another until late G2, at which time they separate and then move during prophase to become the poles that organize the bipolar mitotic spindle. During the G2/M transition, interphase MTs depolymerize and a new population of highly dynamic mitotic MTs are nucleated at the spindle poles. The bipolar mitotic spindle apparatus constitutes the machinery that partitions and separates sister chromatids equally between two daughter cells.

scholarly journals A novel mitotic spindle pole component that originates from the cytoplasm during prophase.

1986 ◽  
Vol 103 (5) ◽  
pp. 1863-1872 ◽  
Author(s):  
P R Sager ◽  
N L Rothfield ◽  
J M Oliver ◽  
R D Berlin
Keyword(s):  
Mitotic Spindle ◽  
Spindle Pole ◽  
Early Prophase ◽  
Microtubule Organizing Center ◽  
Spindle Poles ◽  
Interphase Cells ◽  
Organizing Center ◽  
Mitotic Spindle Pole ◽  
Pole Component

Several unique aspects of mitotic spindle formation have been revealed by investigation of an autoantibody present in the serum of a patient with the CREST (calcinosis, Raynaud's phenomenon, esophageal dysmotility, schlerodacytyly, and telangiectasias) syndrome. This antibody was previously shown to label at the spindle poles of metaphase and anaphase cells and to be absent from interphase cells. We show here that the serum stained discrete cytoplasmic foci in early prophase cells and only later localized to the spindle poles. The cytoplasmic distribution of the antigen was also seen in nocodazole-arrested cells and prophase cells in populations treated with taxol. In normal and taxol-treated cells, the microtubules appeared to emanate from the cytoplasmic foci and polar stain, and in cells released from nocodazole block, microtubules regrew from antigen-containing centers. This characteristic distribution suggests that the antigen is part of a microtubule organizing center. Thus, we propose that a prophase originating polar antigen functions in spindle pole organization as a coalescing microtubule organizing center that is present only during mitosis. Characterization of the serum showed reactions with multiple proteins at 115, 110, 50, 36, 30, and 28 kD. However, affinity-eluted antibody from the 115/110-kD bands was shown to specifically label the spindle pole and cytosolic foci in prophase cells.

scholarly journals Mobility, Microtubule Nucleation and Structure of Microtubule-organizing Centers in Multinucleated Hyphae ofAshbya gossypii

2010 ◽  
Vol 21 (1) ◽  
pp. 18-28 ◽  
Author(s):  
Claudia Lang ◽  
Sandrine Grava ◽  
Tineke van den Hoorn ◽  
Rhonda Trimble ◽  
Peter Philippsen ◽  
...  
Keyword(s):  
Spindle Pole Body ◽  
Hyphal Growth ◽  
Spindle Pole ◽  
Microtubule Organizing Center ◽  
Microtubule Nucleation ◽  
Cytoplasmic Microtubule ◽  
Organizing Center ◽  
Cytoplasmic Side ◽  
Independent Mode

We investigated the migration of multiple nuclei in hyphae of the filamentous fungus Ashbya gossypii. Three types of cytoplasmic microtubule (cMT)-dependent nuclear movements were characterized using live cell imaging: short-range oscillations (up to 4.5 μm/min), rotations (up to 180° in 30 s), and long-range nuclear bypassing (up to 9 μm/min). These movements were superimposed on a cMT-independent mode of nuclear migration, cotransport with the cytoplasmic stream. This latter mode is sufficient to support wild-type-like hyphal growth speeds. cMT-dependent nuclear movements were led by a nuclear-associated microtubule-organizing center, the spindle pole body (SPB), which is the sole site of microtubule nucleation in A. gossypii. Analysis of A. gossypii SPBs by electron microscopy revealed an overall laminar structure similar to the budding yeast SPB but with distinct differences at the cytoplasmic side. Up to six perpendicular and tangential cMTs emanated from a more spherical outer plaque. The perpendicular and tangential cMTs most likely correspond to short, often cortex-associated cMTs and to long, hyphal growth-axis–oriented cMTs, respectively, seen by in vivo imaging. Each SPB nucleates its own array of cMTs, and the lack of overlapping cMT arrays between neighboring nuclei explains the autonomous nuclear oscillations and bypassing observed in A. gossypii hyphae.

Calmodulin and the contractile vacuole complex in mitotic cells of Dictyostelium discoideum

1993 ◽  
Vol 104 (4) ◽  
pp. 1119-1127 ◽  
Author(s):  
Q. Zhu ◽  
T. Liu ◽  
M. Clarke
Keyword(s):  
Dictyostelium Discoideum ◽  
Golgi Complex ◽  
Contractile Vacuole ◽  
Microtubule Organizing Center ◽  
Golgi Membranes ◽  
Golgi Staining ◽  
Interphase Cells ◽  
Organizing Center ◽  
Tubulin Antibodies ◽  
Mitotic Cells

In amoebae of the eukaryotic microorganism Dictyostelium discoideum, calmodulin is greatly enriched on membranes of the contractile vacuole complex, an osmoregulatory organelle. Antibodies specific for Dictyostelium calmodulin were used in the present study to immunolocalize the contractile vacuole complex in relation to the Golgi complex (detected with wheat germ agglutinin) and the microtubule organizing center (MTOC, detected with anti-tubulin antibodies). Cells were examined throughout the cell cycle. Double-staining experiments indicated that the contractile vacuole complex extended to the MTOC in interphase cells, usually, but not always, overlapping the Golgi complex. In metaphase and anaphase cells, the Golgi staining became diffuse, suggesting dispersal of Golgi membranes. In the same mitotic cells, anti-calmodulin antibodies labeled numerous small cortical vacuoles, indicating that the contractile vacuole complex had also become dispersed. When living mitotic cells were examined, the small cortical vacuoles were seen to be active, implying that all parts of the Dictyostelium contractile vacuole complex possess the ability to accumulate fluid and fuse with the plasma membrane. In contrast to observations reported for other types of cells, anti-calmodulin antibodies did not label the mitotic spindle in Dictyostelium. Despite this difference in localization, it is possible that vacuole-associated calmodulin in Dictyostelium cells and spindle-associated calmodulin in larger eukaryotic cells might perform a similar function, namely, regulating calcium levels.

scholarly journals Genetic strain variations in the metaphase-II phenotype of mouse oocytes matured in vivo or in vitro

Reproduction ◽  
2005 ◽  
Vol 130 (6) ◽  
pp. 845-855 ◽  
Author(s):  
Elena Ibáñez ◽  
Alexandra Sanfins ◽  
Catherine M H Combelles ◽  
Eric W Overström ◽  
David F Albertini
Keyword(s):  
Ex Vivo ◽  
Polar Body ◽  
Meiotic Spindle ◽  
Microtubule Organizing Center ◽  
Phenotypic Properties ◽  
Cytoplasmic Microtubule ◽  
Mammalian Embryo ◽  
Predictive Assessments

The interplay between genetic and epigenetic factors plays a central role in mammalian embryo production strategies that superimposeex vivoorin vivomanipulations upon strain background characteristics. In this study, we examined the relationship between genetic background and the phenotypic properties of mouse metaphase-II (M-II) oocytes that were matured underin vivo(IVO) orin vitroconditions, either in a basal (IVM) or a supplemented (IVM + ) medium. Differences existed amongst inbred (C57BL/6), outbred (CF-1, Black Swiss, NU/NU) and hybrid lines (B6D2F1) induced to superovulate with regard to cytoplasmic microtubule organizing center (MTOC) number but not spindle size or shape, except for larger and asymmetrical spindles in Black Swiss oocytes. When oocytes were matured in culture, meiotic spindle and cytoplasmic phenotypic properties of M-II oocytes were affected relative toin vivoconditions and between strains. Specifically, measures of meiotic spindle size, shape, polar pericentrin distribution and cytoplasmic MTOC number all revealed characteristic variations. Interestingly, the overall reduction in cytoplasmic MTOC number noted upon IVM was concomitant with an overall increase in spindle and polar body size. Maturation under IVM + conditions resulted in a further decrease in cytoplasmic MTOC number, but spindle and polar body characteristics were intermediate between IVO and IVM. How these oocyte phenotypic properties of maternal origin may be linked to predictive assessments of fecundity remains to be established.

scholarly journals Ultrastructural immunocytochemical localization of calmodulin in cultured cells.

1983 ◽  
Vol 31 (4) ◽  
pp. 445-461 ◽  
Author(s):  
M C Willingham ◽  
J Wehland ◽  
C B Klee ◽  
N D Richert ◽  
A V Rutherford ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Performic Acid ◽  
Microtubule Organizing Center ◽  
Interphase Cells ◽  
Organizing Center ◽  
Late Telophase ◽  
Cytoplasmic Microtubules ◽  
Spindle Microtubules ◽  
And Function ◽  
Fibroblastic Cells

Using an antibody prepared against performic acid-treated calmodulin, we have localized calmodulin in cultured fibroblastic cells by immunofluorescence and immunoelectron microscopy. In interphase cells, calmodulin was found to be diffusely distributed throughout the cytosol. An increased amount of calmodulin was found in the pericentriolar region of interphase cells. No significant aggregation of calmodulin was found in association with microfilaments, peripheral cytoplasmic microtubules or clathrin-coated structures. Calmodulin was present in moderate amounts in microvilli, ruffles, and zeiotic blebs of the cell surface. In motitic cells, calmodulin was found concentrated in the pericentriolar region, and appeared to concentrate along radiating spindle microtubules proximal to the centrioles. Redistribution of calmodulin was seen between early and late telophase, in which the pericentriolar pattern of calmodulin in early telophase shifted to an aggregation on the intercellular bridge, with a large part of the midbody portion of the bridge being devoid of calmodulin. These results show that calmodulin is distributed throughout the cytosol, but is markedly concentrated in the region of the microtubule organizing center in interphase cells, as well as in elements of the mitotic spindle apparatus. This distribution suggests that calmodulin has a regulatory role in the organization and function of microtubules during interphase, as well as during mitosis.

In vitro nucleation of microtubules from microtubule-organizing center prepared from cellular slime mold

Cell Motility ◽  
1982 ◽  
Vol 2 (3) ◽  
pp. 257-272 ◽  
Author(s):  
Ryoko Kuriyama ◽  
Chikako Sato ◽  
Yoshio Fukui ◽  
Soryu Nishibayashi
Keyword(s):  
Slime Mold ◽  
Cellular Slime Mold ◽  
Microtubule Organizing Center ◽  
Organizing Center ◽  
Cellular Slime

scholarly journals Dictyostelium discoideum CenB Is a Bona Fide Centrin Essential for Nuclear Architecture and Centrosome Stability

2009 ◽  
Vol 8 (8) ◽  
pp. 1106-1117 ◽  
Author(s):  
Sebastian Mana-Capelli ◽  
Ralph Gräf ◽  
Denis A. Larochelle
Keyword(s):  
Dictyostelium Discoideum ◽  
Calcium Binding ◽  
Amino Acid Level ◽  
Nuclear Architecture ◽  
Microtubule Organizing Center ◽  
Whole Cells ◽  
Ef Hand ◽  
Interphase Cells ◽  
Organizing Center ◽  
Bona Fide

ABSTRACT Centrins are a family of proteins within the calcium-binding EF-hand superfamily. In addition to their archetypical role at the microtubule organizing center (MTOC), centrins have acquired multiple functionalities throughout the course of evolution. For example, centrins have been linked to different nuclear activities, including mRNA export and DNA repair. Dictyostelium discoideum centrin B is a divergent member of the centrin family. At the amino acid level, DdCenB shows 51% identity with its closest relative and only paralog, DdCenA. Phylogenetic analysis revealed that DdCenB and DdCenA form a well-supported monophyletic and divergent group within the centrin family of proteins. Interestingly, fluorescently tagged versions of DdCenB were not found at the centrosome (in whole cells or in isolated centrosomes). Instead, DdCenB localized to the nuclei of interphase cells. This localization disappeared as the cells entered mitosis, although Dictyostelium cells undergo a closed mitosis in which the nuclear envelope (NE) does not break down. DdCenB knockout cells exhibited aberrant nuclear architecture, characterized by enlarged and deformed nuclei and loss of proper centrosome-nucleus anchoring (observed as NE protrusions). At the centrosome, loss of DdCenB resulted in defects in the organization and morphology of the MTOC and supernumerary centrosomes and centrosome-related bodies. The multiple defects that the loss of DdCenB generated at the centrosome can be explained by its atypical division cycle, transitioning into the NE as it divides at mitosis. On the basis of these findings, we propose that DdCenB is required at interphase to maintain proper nuclear architecture, and before delocalizing from the nucleus, DdCenB is part of the centrosome duplication machinery.

scholarly journals Radial F-actin Organization During Early Neuronal Development

2018 ◽  
Author(s):  
Durga Praveen Meka ◽  
Robin Scharrenberg ◽  
Bing Zhao ◽  
Theresa König ◽  
Irina Schaefer ◽  
...  
Keyword(s):  
Neuronal Development ◽  
Super Resolution ◽  
Actin Dynamics ◽  
Cell Periphery ◽  
Microtubule Organizing Center ◽  
Actin Organization ◽  
Organizing Center ◽  
Super Resolution Microscopy ◽  
Radial Organization

AbstractThe centrosome is thought to be the major neuronal microtubule-organizing center (MTOC) in early neuronal development, producing microtubules with a radial organization. In addition, albeit in vitro, recent work showed that isolated centrosomes could serve as an actin-organizing center (Farina et al., 2016), raising the possibility that neuronal development may, in addition, require a centrosome-based actin radial organization. Here we report, using super-resolution microscopy and live-cell imaging, F-actin organization around the centrosome with dynamic F-actin aster-like structures with F-actin fibers extending and retracting actively. Photoconversion/photoactivation experiments and molecular manipulations of F-actin stability reveal a robust flux of somatic F-actin towards the cell periphery. Finally, we show that somatic F-actin intermingles with centrosomal PCM-1 satellites. Knockdown of PCM-1 and disruption of centrosomal activity not only affect F-actin dynamics near the centrosome but also in distal growth cones. Collectively the data show a radial F-actin organization during early neuronal development, which might be a cellular mechanism for providing peripheral regions with a fast and continuous source of actin polymers; hence sustaining initial neuronal development.

scholarly journals HDAC6 mediates an aggresome-like mechanism for NLRP3 and pyrin inflammasome activation

Science ◽  
2020 ◽  
Vol 369 (6510) ◽  
pp. eaas8995 ◽  
Author(s):  
Venkat Giri Magupalli ◽  
Roberto Negro ◽  
Yuzi Tian ◽  
Arthur V. Hauenstein ◽  
Giuseppe Di Caprio ◽  
...  
Keyword(s):  
Immune Surveillance ◽  
Inflammasome Activation ◽  
Histone Deacetylase 6 ◽  
Microtubule Organizing Center ◽  
Pyrin Domain ◽  
Microtubule Transport ◽  
Organizing Center ◽  
Aggresome Formation ◽  
Inflammatory Caspases

Inflammasomes are supramolecular complexes that play key roles in immune surveillance. This is accomplished by the activation of inflammatory caspases, which leads to the proteolytic maturation of interleukin 1β (IL-1β) and pyroptosis. Here, we show that nucleotide-binding domain, leucine-rich repeat, and pyrin domain–containing protein 3 (NLRP3)- and pyrin-mediated inflammasome assembly, caspase activation, and IL-1β conversion occur at the microtubule-organizing center (MTOC). Furthermore, the dynein adapter histone deacetylase 6 (HDAC6) is indispensable for the microtubule transport and assembly of these inflammasomes both in vitro and in mice. Because HDAC6 can transport ubiquitinated pathological aggregates to the MTOC for aggresome formation and autophagosomal degradation, its role in NLRP3 and pyrin inflammasome activation also provides an inherent mechanism for the down-regulation of these inflammasomes by autophagy. This work suggests an unexpected parallel between the formation of physiological and pathological aggregates.

Sign in / Sign up

Export Citation Format

Share Document