scholarly journals Microtubule organization: A complex solution

2016 ◽  
Vol 213 (6) ◽  
pp. 609-612 ◽  
Author(s):  
Paul T. Conduit
Keyword(s):  
Complex Solution ◽  
Microtubule Nucleation ◽  
Microtubule Organization ◽  
Microtubule Organizing Centers ◽  
Cell Biol ◽  
Ring Complexes ◽  
And Function

Microtubule nucleation within cells is catalyzed by γ-tubulin ring complexes localized at specific microtubule-organizing centers. In this issue, Muroyama et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201601099) reveal heterogeneity in the composition and function of these complexes, with wide implications for how cells organize their microtubule arrays.

scholarly journals Can microtubule motors use every available track?

2018 ◽  
Vol 217 (12) ◽  
pp. 4055-4056
Author(s):  
Prachee Avasthi
Keyword(s):  
Cell Biol ◽  
Microtubule Motors ◽  
Flagellar Assembly ◽  
And Function

Flagellar assembly and function depend on cargo traveling via motors on microtubule doublets. Bertiaux, Mallet et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201805030) find that only a subset of available doublets are used for this transport in trypanosomes, leading to questions about how and why this is achieved.

Centrosome and microtubule dynamics during meiotic progression in the mouse oocyte

1991 ◽  
Vol 100 (2) ◽  
pp. 289-298 ◽  
Author(s):  
S.M. Messinger ◽  
D.F. Albertini
Keyword(s):  
Mouse Oocyte ◽  
Meiotic Maturation ◽  
Microtubule Nucleation ◽  
Microtubule Organization ◽  
Double Labeling ◽  
Meiotic Progression ◽  
Tubulin Antibodies ◽  
Discrete Populations ◽  
Meiosis I

The disposition, function and fate of centrosomes were analysed in mouse oocytes undergoing in vitro meiotic maturation, using multiple-label fluorescence microscopy. Oocytes fixed at various points during meiotic progression were double labeled with either human centrosome-specific antibody, 5051, and anti-tubulin antibodies or 5051 and MPM-2 antibodies in order to evaluate the microtubule nucleation capacity and phosphorylation status of centrosomes during this process. Double labeling with anti-tubulin antibodies revealed two populations of centrosomes that undergo stage-specific changes in number, location and microtubule nucleation capacity in relation to spindle assembly and cytoplasmic events. Specifically, one population was consistently associated with chromatin throughout meiotic maturation whereas a second population of cytoplasmic centrosomes exhibited maximal numbers and nucleation capacity at prometaphase and anaphase of meiosis-I. Quantitative evaluation of cytoplasmic centrosomes indicated increased numbers during the transition from diakinesis to prometaphase and metaphase to anaphase and total disappearance during telophase. Colocalization studies with MPM-2 revealed that centrosomes were always phosphorylated. However, at metaphase of meiosis I and II the microtubule nucleation capacity of centrosomes was diminished. These results suggest the existence of two discrete populations of centrosomes in the mouse oocyte that are coordinately regulated to subserve aspects of microtubule organization relative to both nuclear and cytoplasmic events.

scholarly journals Characterization and Reconstitution of Drosophila γ-Tubulin Ring Complex Subunits

2000 ◽  
Vol 151 (7) ◽  
pp. 1513-1524 ◽  
Author(s):  
Ruwanthi N. Gunawardane ◽  
Ona C. Martin ◽  
Kan Cao ◽  
Lijun Zhang ◽  
Kimberly Dej ◽  
...  
Keyword(s):  
Expression System ◽  
Baculovirus Expression System ◽  
Sequence Motifs ◽  
Microtubule Nucleation ◽  
Sequence Comparisons ◽  
Baculovirus Expression ◽  
Ring Complex ◽  
And Function ◽  
First Time ◽  
Centrosomal Proteins

The γ-tubulin ring complex (γTuRC) is important for microtubule nucleation from the centrosome. In addition to γ-tubulin, the Drosophila γTuRC contains at least six subunits, three of which [Drosophila gamma ring proteins (Dgrips) 75/d75p, 84, and 91] have been characterized previously. Dgrips84 and 91 are present in both the small γ-tubulin complex (γTuSC) and the γTuRC, while the remaining subunits are found only in the γTuRC. To study γTuRC assembly and function, we first reconstituted γTuSC using the baculovirus expression system. Using the reconstituted γTuSC, we showed for the first time that this subcomplex of the γTuRC has microtubule binding and capping activities. Next, we characterized two new γTuRC subunits, Dgrips128 and 163, and showed that they are centrosomal proteins. Sequence comparisons among all known γTuRC subunits revealed two novel sequence motifs, which we named grip motifs 1 and 2. We found that Dgrips128 and 163 can each interact with γTuSC. However, this interaction is insufficient for γTuRC assembly.

scholarly journals Alp7-Mto1 and Alp14 synergize to promote interphase microtubule regrowth from the nuclear envelope

2019 ◽  
Vol 11 (11) ◽  
pp. 944-955 ◽  
Author(s):  
Wenyue Liu ◽  
Fan Zheng ◽  
Yucai Wang ◽  
Chuanhai Fu
Keyword(s):  
Nuclear Envelope ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Microtubule Assembly ◽  
Dependent Manner ◽  
Microtubule Nucleation ◽  
Microtubule Organizing Centers ◽  
Evolutionarily Conserved ◽  
Microtubule Growth ◽  
In Cells

Abstract Microtubules grow not only from the centrosome but also from various noncentrosomal microtubule-organizing centers (MTOCs), including the nuclear envelope (NE) and pre-existing microtubules. The evolutionarily conserved proteins Mto1/CDK5RAP2 and Alp14/TOG/XMAP215 have been shown to be involved in promoting microtubule nucleation. However, it has remained elusive as to how the microtubule nucleation promoting factors are specified to various noncentrosomal MTOCs, particularly the NE, and how these proteins coordinate to organize microtubule assembly. Here, we demonstrate that in the fission yeast Schizosaccharomyces pombe, efficient interphase microtubule growth from the NE requires Alp7/TACC, Alp14/TOG/XMAP215, and Mto1/CDK5RAP2. The absence of Alp7, Alp14, or Mto1 compromises microtubule regrowth on the NE in cells undergoing microtubule repolymerization. We further demonstrate that Alp7 and Mto1 interdependently localize to the NE in cells without microtubules and that Alp14 localizes to the NE in an Alp7 and Mto1-dependent manner. Tethering Mto1 to the NE in cells lacking Alp7 partially restores microtubule number and the efficiency of microtubule generation from the NE. Hence, our study delineates that Alp7, Alp14, and Mto1 work in concert to regulate interphase microtubule regrowth on the NE.

scholarly journals A role for Gle1, a regulator of DEAD-box RNA helicases, at centrosomes and basal bodies

2017 ◽  
Vol 28 (1) ◽  
pp. 120-127 ◽  
Author(s):  
Li-En Jao ◽  
Abdalla Akef ◽  
Susan R. Wente
Keyword(s):  
Mrna Export ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Rna Helicases ◽  
Microtubule Organization ◽  
Developmental Defects ◽  
Dead Box ◽  
Pericentriolar Material ◽  
Pore Complexes ◽  
And Function

Control of organellar assembly and function is critical to eukaryotic homeostasis and survival. Gle1 is a highly conserved regulator of RNA-dependent DEAD-box ATPase proteins, with critical roles in both mRNA export and translation. In addition to its well-defined interaction with nuclear pore complexes, here we find that Gle1 is enriched at the centrosome and basal body. Gle1 assembles into the toroid-shaped pericentriolar material around the mother centriole. Reduced Gle1 levels are correlated with decreased pericentrin localization at the centrosome and microtubule organization defects. Of importance, these alterations in centrosome integrity do not result from loss of mRNA export. Examination of the Kupffer’s vesicle in Gle1-depleted zebrafish revealed compromised ciliary beating and developmental defects. We propose that Gle1 assembly into the pericentriolar material positions the DEAD-box protein regulator to function in localized mRNA metabolism required for proper centrosome function.

scholarly journals Interaction of Aurora-A and centrosomin at the microtubule-nucleating site in Drosophila and mammalian cells

2003 ◽  
Vol 162 (5) ◽  
pp. 757-764 ◽  
Author(s):  
Yasuhiko Terada ◽  
Yumi Uetake ◽  
Ryoko Kuriyama
Keyword(s):  
Mammalian Cells ◽  
Aurora A Kinase ◽  
Aurora A ◽  
Mitotic Spindles ◽  
Microtubule Nucleation ◽  
Microtubule Organization ◽  
Centrosomal Protein ◽  
Spindle Poles

A mitosis-specific Aurora-A kinase has been implicated in microtubule organization and spindle assembly in diverse organisms. However, exactly how Aurora-A controls the microtubule nucleation onto centrosomes is unknown. Here, we show that Aurora-A specifically binds to the COOH-terminal domain of a Drosophila centrosomal protein, centrosomin (CNN), which has been shown to be important for assembly of mitotic spindles and spindle poles. Aurora-A and CNN are mutually dependent for localization at spindle poles, which is required for proper targeting of γ-tubulin and other centrosomal components to the centrosome. The NH2-terminal half of CNN interacts with γ-tubulin, and induces cytoplasmic foci that can initiate microtubule nucleation in vivo and in vitro in both Drosophila and mammalian cells. These results suggest that Aurora-A regulates centrosome assembly by controlling the CNN's ability to targeting and/or anchoring γ-tubulin to the centrosome and organizing microtubule-nucleating sites via its interaction with the COOH-terminal sequence of CNN.

scholarly journals GCP5 and GCP6: Two New Members of the Human γ-Tubulin Complex

2001 ◽  
Vol 12 (11) ◽  
pp. 3340-3352 ◽  
Author(s):  
Steven M. Murphy ◽  
Andrea M. Preble ◽  
Urvashi K. Patel ◽  
Kathy L. O'Connell ◽  
D. Prabha Dias ◽  
...  
Keyword(s):  
Sequence Similarity ◽  
Single Copy ◽  
Mass Spectrometry Analysis ◽  
Subunit Structure ◽  
Microtubule Nucleation ◽  
New Members ◽  
Spectrometry Analysis ◽  
Multiple Copies ◽  
And Function

The γ-tubulin complex is a large multiprotein complex that is required for microtubule nucleation at the centrosome. Here we report the purification and characterization of the human γ-tubulin complex and the identification of its subunits. The human γ-tubulin complex is a ring of ∼25 nm, has a subunit structure similar to that reported for γ-tubulin complexes from other species, and is able to nucleate microtubule polymerization in vitro. Mass spectrometry analysis of the human γ-tubulin complex components confirmed the presence of four previously identified components (γ-tubulin and γ-tubulin complex proteins [GCPs] 2, 3, and 4) and led to the identification of two new components, GCP5 and GCP6. Sequence analysis revealed that the GCPs share five regions of sequence similarity and define a novel protein superfamily that is conserved in metazoans. GCP5 and GCP6, like other components of the γ-tubulin complex, localize to the centrosome and associate with microtubules, suggesting that the entire γ-tubulin complex takes part in both of these interactions. Stoichiometry experiments revealed that there is a single copy of GCP5 and multiple copies of γ-tubulin, GCP2, GCP3, and GCP4 within the γ-tubulin complex. Thus, the γ-tubulin complex is conserved in structure and function, suggesting that the mechanism of microtubule nucleation is conserved.

scholarly journals Phospho-regulated auto-inhibition of Cnn controls microtubule nucleation during cell division

2020 ◽  
Author(s):  
Corinne A. Tovey ◽  
Chisato Tsuji ◽  
Alice Egerton ◽  
Fred Bernard ◽  
Antoine Guichet ◽  
...  
Keyword(s):  
Cell Division ◽  
Microtubule Nucleation ◽  
Dividing Cells ◽  
Ring Complexes

Abstractγ-tubulin-ring-complexes (γ-TuRCs) nucleate microtubules. They are recruited to centrosomes in dividing cells via binding to N-terminal CM1 domains within γ-TuRC-tethering proteins, including Drosophila Cnn. Binding promotes microtubule nucleation and is restricted to centrosomes, but the mechanism regulating binding remains unknown. Here we identify an extreme N-terminal “CM1 auto-inhibition” (CAI) domain within the centrosomal isoform of Cnn (Cnn-C) that inhibits γ-TuRC binding. Cnn-C is phosphorylated at centrosomes and we find that phospho-mimicking sites within the CAI domain helps relieve auto-inhibition. In contrast, the testes-specific mitochondrial Cnn-T isoform lacks the CAI domain and can bind strongly to cytosolic γ-TuRCs. Ubiquitously expressing a version of Cnn-C lacking the CAI domain leads to major cell division defects, which appears to be due to ectopic cytosolic microtubule nucleation. We propose that the CAI domain folds back to sterically inhibit the CM1 domain, and that this auto-inhibition is relieved by phosphorylation that occurs specifically at centrosomes.

scholarly journals Autoinhibition of Cnn binding to γ-TuRCs prevents ectopic microtubule nucleation and cell division defects

2021 ◽  
Vol 220 (8) ◽  
Author(s):  
Corinne A. Tovey ◽  
Chisato Tsuji ◽  
Alice Egerton ◽  
Fred Bernard ◽  
Antoine Guichet ◽  
...  
Keyword(s):  
Cell Division ◽  
Microtubule Nucleation ◽  
Dividing Cells ◽  
Ring Complexes ◽  
Shed Light

γ-Tubulin ring complexes (γ-TuRCs) nucleate microtubules. They are recruited to centrosomes in dividing cells via binding to N-terminal CM1 domains within γ-TuRC–tethering proteins, including Drosophila Centrosomin (Cnn). Binding promotes microtubule nucleation and is restricted to centrosomes in dividing cells, but the mechanism regulating binding remains unknown. Here, we identify an extreme N-terminal CM1 autoinhibition (CAI) domain found specifically within the centrosomal isoform of Cnn (Cnn-C) that inhibits γ-TuRC binding. Robust binding occurs after removal of the CAI domain or with the addition of phosphomimetic mutations, suggesting that phosphorylation helps relieve inhibition. We show that regulation of Cnn binding to γ-TuRCs is isoform specific and that misregulation of binding can result in ectopic cytosolic microtubules and major defects during cell division. We also find that human CDK5RAP2 is autoinhibited from binding γ-TuRCs, suggesting conservation across species. Overall, our results shed light on how and why CM1 domain binding to γ-TuRCs is regulated.

From tip to toe – dressing centrioles in γTuRC

2021 ◽  
Vol 134 (14) ◽  
Author(s):  
Nina Schweizer ◽  
Jens Lüders
Keyword(s):  
Cell Proliferation ◽  
Proximal Part ◽  
Supporting Cell ◽  
Canonical Function ◽  
Microtubule Organization ◽  
Classical View ◽  
Cylindrical Structures ◽  
Ring Complex ◽  
Pericentriolar Material ◽  
And Function

ABSTRACT Centrioles are microtubule-based cylindrical structures that assemble the centrosome and template the formation of cilia. The proximal part of centrioles is associated with the pericentriolar material, a protein scaffold from which microtubules are nucleated. This activity is mediated by the γ-tubulin ring complex (γTuRC) whose central role in centrosomal microtubule organization has been recognized for decades. However, accumulating evidence suggests that γTuRC activity at this organelle is neither restricted to the pericentriolar material nor limited to microtubule nucleation. Instead, γTuRC is found along the entire centriole cylinder, at subdistal appendages, and inside the centriole lumen, where its canonical function as a microtubule nucleator might be supplemented or replaced by a function in microtubule anchoring and centriole stabilization, respectively. In this Opinion, we discuss recent insights into the expanded repertoire of γTuRC activities at centrioles and how distinct subpopulations of γTuRC might act in concert to ensure centrosome and cilia biogenesis and function, ultimately supporting cell proliferation, differentiation and homeostasis. We propose that the classical view of centrosomal γTuRC as a pericentriolar material-associated microtubule nucleator needs to be revised.

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