scholarly journals Class V β-tubulin alters dynamic instability and stimulates microtubule detachment from centrosomes

2011 ◽  
Vol 22 (7) ◽  
pp. 1025-1034 ◽  
Author(s):  
Rajat Bhattacharya ◽  
Hailing Yang ◽  
Fernando Cabral
Keyword(s):  
Cell Division ◽  
Dynamic Instability ◽  
Microtubule Assembly ◽  
Class V ◽  
Tubulin Isotypes ◽  
Specific Manner ◽  
Microtubule Growth ◽  
A Minor ◽  
And Function

A multigene family produces tubulin isotypes that are expressed in a tissue-specific manner, but the role of these isotypes in microtubule assembly and function is unclear. Recently we showed that overexpression or depletion of β5-tubulin, a minor isotype with wide tissue distribution, inhibits cell division. We now report that elevated β5-tubulin causes uninterrupted episodes of microtubule shortening and increased shortening rates. Conversely, depletion of β5-tubulin reduces shortening rates and causes very short excursions of growth and shortening. A tubulin conformation-sensitive antibody indicated that the uninterrupted shortening can be explained by a relative absence of stabilized patches along the microtubules that contain tubulin in an assembly-competent conformation and normally act to restore microtubule growth. In addition to these changes in dynamic instability, overexpression of β5-tubulin causes fragmentation that results from microtubule detachment from centrosomes, and it is this activity that best explains the effects of β5 on cell division. Paclitaxel inhibits microtubule detachment, increases the number of assembly-competent tubulin patches, and inhibits microtubule shortening, thus providing an explanation for why the drug can counteract the phenotypic effects of β5 overexpression. On the basis of these observations, we propose that cells can use β5-tubulin expression to adjust the behavior of the microtubule cytoskeleton.

The extended tubulin superfamily

2001 ◽  
Vol 114 (15) ◽  
pp. 2723-2733 ◽  
Author(s):  
Paul G. McKean ◽  
Sue Vaughan ◽  
Keith Gull
Keyword(s):  
Cell Biology ◽  
Structure And Function ◽  
Microtubule Assembly ◽  
Eukaryotic Cells ◽  
Current Evidence ◽  
Post Translational Modification ◽  
Tubulin Isotypes ◽  
The Past ◽  
And Function

Although most eukaryotic cells can express multiple isotypes of αβ-tubulin, the significance of this diversity has not always been apparent. Recent data indicate that particular αβ-tubulin isotypes, both genome encoded and those derived by post-translational modification, can directly influence microtubule structure and function — thus validating ideas originally proposed in the multitubulin hypothesis over 25 years ago.It has also become increasingly evident over the past year that some (but intriguingly not all) eukaryotes encode several other tubulin proteins, and to date five further members of the tubulin superfamily, γ, δ, ϵ, 𝛇 and η, have been identified. Although the role of γ-tubulin in the nucleation of microtubule assembly is now well established, far less is known about the functions of δ-, ϵ-, 𝛇- and η-tubulin. Recent work has expanded our knowledge of the functions and localisation of these newer members of the tubulin superfamily, and the emerging data suggesting a restricted evolutionary distribution of these `new' tubulin proteins, conforms to established knowledge of microtubule cell biology. On the basis of current evidence, we predict that δ-, ϵ-, 𝛇- and η-tubulin all have functions associated with the centriole or basal body of eukaryotic cells and organisms.

scholarly journals The mitotic spindle protein CKAP2 potently increases formation and stability of microtubules

eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Thomas S McAlear ◽  
Susanne Bechstedt
Keyword(s):  
Cell Division ◽  
Growth Factor ◽  
Mitotic Spindle ◽  
Apparent Rate Constant ◽  
Microtubule Dynamics ◽  
Proliferation Marker ◽  
Microtubule Growth ◽  
Large Rearrangements ◽  
And Function

Cells increase microtubule dynamics to make large rearrangements to their microtubule cytoskeleton during cell division. Changes in microtubule dynamics are essential for the formation and function of the mitotic spindle, and misregulation can lead to aneuploidy and cancer. Using in vitro reconstitution assays we show that the mitotic spindle protein Cytoskeleton-Associated Protein 2 (CKAP2) has a strong effect on nucleation of microtubules by lowering the critical tubulin concentration 100-fold. CKAP2 increases the apparent rate constant ka of microtubule growth by 50-fold and increases microtubule growth rates. In addition, CKAP2 strongly suppresses catastrophes. Our results identify CKAP2 as the most potent microtubule growth factor to date. These finding help explain CKAP2's role as an important spindle protein, proliferation marker, and oncogene.

scholarly journals Nucleotide-dependent stiffness suggests role of interprotofilament bonds in microtubule assembly

2017 ◽  
Author(s):  
Katja M. Taute ◽  
Ernst-Ludwig Florin
Keyword(s):  
Dynamic Instability ◽  
Eukaryotic Cell ◽  
Microtubule Assembly ◽  
Precision Measurements ◽  
Structural Studies ◽  
Lateral Interactions ◽  
Cell Functions ◽  
Subsequent Hydrolysis ◽  
Structural Mechanisms

ABSTRACTMany eukaryotic cell functions depend on dynamic instability, meaning the nucleotide-driven assembly and disassembly of microtubules. Assembly requires the constituent tubulin dimers to bind the nucleotide GTP, and its subsequent hydrolysis to GDP induces disassembly. The underlying structural mechanisms, however, are not well understood. Here, we determine the strength of contacts in the microtubule lattice by combining high precision measurements of the bending stiffness of analogues of GTP and GDP microtubules with a recent theoretical model. While previous structural studies have focussed on how the curvature of the tubulin dimer is affected by nucleotide binding, we present evidence of a dramatic regulation of the lateral interactions between the parallel protofilaments that dimers form in the microtubule. We conclude that the shear coupling between neighboring protofilaments is at least two orders of magnitude stronger in the GTP state than in the GDP state, and discuss the implications for the microtubule assembly.

scholarly journals Measuring microtubule dynamics

2018 ◽  
Vol 62 (6) ◽  
pp. 725-735 ◽  
Author(s):  
Alexander James Zwetsloot ◽  
Gokhan Tut ◽  
Anne Straube
Keyword(s):  
Small Molecules ◽  
Dynamic Instability ◽  
Microtubule Dynamics ◽  
Regulatory Proteins ◽  
Microtubule Assembly ◽  
Cancer Chemotherapeutics ◽  
Pulling Forces ◽  
Inflammatory Drugs ◽  
And Function ◽  
Pushing And Pulling

Microtubules are key players in cellular self-organization, acting as structural scaffolds, cellular highways, force generators and signalling platforms. Microtubules are polar filaments that undergo dynamic instability, i.e. transition between phases of growth and shrinkage. This allows microtubules to explore the inner space of the cell, generate pushing and pulling forces and remodel themselves into arrays with different geometry and function such as the mitotic spindle. To do this, eukaryotic cells employ an arsenal of regulatory proteins to control microtubule dynamics spatially and temporally. Plants and microorganisms have developed secondary metabolites that perturb microtubule dynamics, many of which are in active use as cancer chemotherapeutics and anti-inflammatory drugs. Here, we summarize the methods used to visualize microtubules and to measure the parameters of dynamic instability to study both microtubule regulatory proteins and the action of small molecules interfering with microtubule assembly and/or disassembly.

scholarly journals The pseudo GTPase CENP-M drives human kinetochore assembly

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Federica Basilico ◽  
Stefano Maffini ◽  
John R Weir ◽  
Daniel Prumbaum ◽  
Ana M Rojas ◽  
...  
Keyword(s):  
Cell Division ◽  
Small Gtpases ◽  
Conformational Switching ◽  
Point Mutant ◽  
Kinetochore Assembly ◽  
Gtp Binding ◽  
Chromosome Alignment ◽  
Spindle Microtubules ◽  
And Function

Kinetochores, multi-subunit complexes that assemble at the interface with centromeres, bind spindle microtubules to ensure faithful delivery of chromosomes during cell division. The configuration and function of the kinetochore–centromere interface is poorly understood. We report that a protein at this interface, CENP-M, is structurally and evolutionarily related to small GTPases but is incapable of GTP-binding and conformational switching. We show that CENP-M is crucially required for the assembly and stability of a tetramer also comprising CENP-I, CENP-H, and CENP-K, the HIKM complex, which we extensively characterize through a combination of structural, biochemical, and cell biological approaches. A point mutant affecting the CENP-M/CENP-I interaction hampers kinetochore assembly and chromosome alignment and prevents kinetochore recruitment of the CENP-T/W complex, questioning a role of CENP-T/W as founder of an independent axis of kinetochore assembly. Our studies identify a single pathway having CENP-C as founder, and CENP-H/I/K/M and CENP-T/W as CENP-C-dependent followers.

Mitotic spindle morphogenesis: Ran on the microtubule cytoskeleton and beyond

2006 ◽  
Vol 34 (5) ◽  
pp. 716-721 ◽  
Author(s):  
B. Goodman ◽  
Y. Zheng
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Microtubule Assembly ◽  
Microtubule Organization ◽  
Spindle Matrix ◽  
Small G Protein ◽  
Important Regulator

Assembly and disassembly of the mitotic spindle are essential for both chromosome segregation and cell division. The small G-protein Ran has emerged as an important regulator of spindle assembly. In this review, we look at the role of Ran in different aspects of spindle assembly, including its effects on microtubule assembly dynamics and microtubule organization. In addition, we examine the possibility of a spindle matrix and the role Ran might play in such a structure.

scholarly journals A Ubiquitous β-tubulin Disrupts Microtubule Assembly and Inhibits Cell Proliferation

2004 ◽  
Vol 15 (7) ◽  
pp. 3123-3131 ◽  
Author(s):  
Rajat Bhattacharya ◽  
Fernando Cabral
Keyword(s):  
Cell Proliferation ◽  
Mammalian Cells ◽  
Microtubule Assembly ◽  
Microtubule Organization ◽  
Class V ◽  
Tubulin Isotypes ◽  
Concomitant Reduction ◽  
Mitotic Spindle Assembly ◽  
Dose Dependent ◽  
Β Tubulin

Vertebrate tubulin is encoded by a multigene family that produces distinct gene products, or isotypes, of both the α- and β-tubulin subunits. The isotype sequences are conserved across species supporting the hypothesis that different isotypes subserve different functions. To date, however, most studies have demonstrated that tubulin isotypes are freely interchangeable and coassemble into all classes of microtubules. We now report that, in contrast to other isotypes, overexpression of a mouse class V β-tubulin cDNA in mammalian cells produces a strong, dose-dependent disruption of microtubule organization, increased microtubule fragmentation, and a concomitant reduction in cellular microtubule polymer levels. These changes also disrupt mitotic spindle assembly and block cell proliferation. Consistent with diminished microtubule assembly, there is an increased tolerance for the microtubule stabilizing drug, paclitaxel, which is able to reverse many of the effects of class V β-tubulin overexpression. Moreover, transfected cells selected in paclitaxel exhibit increased expression of class V β-tubulin, indicating that this isotype is responsible for the drug resistance. The results show that class V β-tubulin is functionally distinct from other tubulin isotypes and imparts unique properties on the microtubules into which it incorporates.

scholarly journals The Role of Tissue-resident γδ T Cells in Stress Surveillance and Tissue Maintenance

Cells ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 686 ◽  
Author(s):  
Margarete D. Johnson ◽  
Deborah A. Witherden ◽  
Wendy L. Havran
Keyword(s):  
T Cells ◽  
Adipose Tissue ◽  
Intestinal Epithelium ◽  
Γδ T Cells ◽  
Minor Population ◽  
A Minor ◽  
And Function ◽  
Protection Against Infection ◽  
Barrier Tissues

While forming a minor population in the blood and lymphoid compartments, γδ T cells are significantly enriched within barrier tissues. In addition to providing protection against infection, these tissue-resident γδ T cells play critical roles in tissue homeostasis and repair. γδ T cells in the epidermis and intestinal epithelium produce growth factors and cytokines that are important for the normal turnover and maintenance of surrounding epithelial cells and are additionally required for the efficient recognition of, and response to, tissue damage. A role for tissue-resident γδ T cells is emerging outside of the traditional barrier tissues as well, with recent research indicating that adipose tissue-resident γδ T cells are required for the normal maintenance and function of the adipose tissue compartment. Here we review the functions of tissue-resident γδ T cells in the epidermis, intestinal epithelium, and adipose tissue, and compare the mechanisms of their activation between these sites.

scholarly journals Lipoprotein lipase in mouse kidney: effects of nutritional status and high-fat diet

2019 ◽  
Vol 316 (3) ◽  
pp. F558-F571
Author(s):  
Rakel Nyrén ◽  
Elena Makoveichuk ◽  
Sandhya Malla ◽  
Sander Kersten ◽  
Stefan K. Nilsson ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
High Fat Diet ◽  
Mouse Kidney ◽  
Minor Role ◽  
Lipid Uptake ◽  
High Fat ◽  
A Minor ◽  
And Function

Activity of lipoprotein lipase (LPL) is high in mouse kidney, but the reason is poorly understood. The aim was to characterize localization, regulation, and function of LPL in kidney of C57BL/6J mice. We found LPL mainly in proximal tubules, localized inside the tubular epithelial cells, under all conditions studied. In fed mice, some LPL colocalized with the endothelial markers CD31 and GPIHBP1 and could be removed by perfusion with heparin, indicating a vascular location. The role of angiopoietin-like protein 4 (ANGPTL4) for nutritional modulation of LPL activity was studied in wild-type and Angptl4−/− mice. In Angptl4−/− mice, kidney LPL activity remained high in fasted animals, indicating that ANGPTL4 is involved in suppression of LPL activity on fasting, like in adipose tissue. The amount of ANGPTL4 protein in kidney was low, and the protein appeared smaller in size, compared with ANGPTL4 in heart and adipose tissue. To study the influence of obesity, mice were challenged with high-fat diet for 22 wk, and LPL was studied after an overnight fast compared with fasted mice given food for 3 h. High-fat diet caused blunting of the normal adaptation of LPL activity to feeding/fasting in adipose tissue, but in kidneys this adaptation was lost only in male mice. LPL activity increases to high levels in mouse kidney after feeding, but as no difference in uptake of chylomicron triglycerides in kidneys is found between fasted and fed states, our data confirm that LPL appears to have a minor role for lipid uptake in this organ.

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