scholarly journals Dynamic instability 30 years later: complexities in microtubule growth and catastrophe

2015 ◽  
Vol 26 (7) ◽  
pp. 1207-1210 ◽  
Author(s):  
Gary J. Brouhard
Keyword(s):  
Dynamic Instability ◽  
Gtp Hydrolysis ◽  
Microtubule Growth

Microtubules are not like other polymers. Whereas polymers such as F-actin will grow continuously as long as the subunit concentration is high enough, a steadily growing microtubule can suddenly shrink even when there is ample αβ-tubulin around. This remarkable behavior was discovered in 1984 when Tim Mitchison and Marc Kirschner deduced that microtubules switch from growth to shrinkage when they lose their GTP caps. Here, I review the canonical explanation of dynamic instability that was fleshed out in the years after its discovery. Many aspects of this explanation have been recently subverted, particularly those related to how GTP-tubulin forms polymers and why GTP hydrolysis disrupts them. I describe these developments and speculate on how our explanation of dynamic instability can be changed to accommodate them.

scholarly journals Dilution of individual microtubules observed in real time in vitro: evidence that cap size is small and independent of elongation rate.

1991 ◽  
Vol 114 (1) ◽  
pp. 73-81 ◽  
Author(s):  
R A Walker ◽  
N K Pryer ◽  
E D Salmon
Keyword(s):  
Dynamic Instability ◽  
Elongation Rate ◽  
Gtp Hydrolysis ◽  
Microtubule Stability ◽  
Assembly Mechanism ◽  
High Elongation ◽  
Microtubule Growth ◽  
Hydrolysis Of ◽  
Brain Tubulin

Although the mechanism of microtubule dynamic instability is thought to involve the hydrolysis of tubulin-bound GTP, the mechanism of GTP hydrolysis and the basis of microtubule stability are controversial. Video microscopy of individual microtubules and dilution protocols were used to examine the size and lifetime of the stabilizing cap. Purified porcine brain tubulin (7-23 microM) was assembled at 37 degrees C onto both ends of isolated sea urchin axoneme fragments in a miniature flow cell to give a 10-fold variation in elongation rate. The tubulin concentration in the region of microtubule growth could be diluted rapidly (by 84% within 3 s of the onset of dilution). Upon perfusion with buffer containing no tubulin, microtubules experienced a catastrophe (conversion from elongation to rapid shortening) within 4-6 s on average after dilution to 16% of the initial concentration, independent of the predilution rate of elongation and length. Based on extrapolation of catastrophe frequency to zero tubulin concentration, the estimated lifetime of the stable cap after infinite dilution was less than 3-4 s for plus and minus ends, much shorter than the approximately 200 s observed at steady state (Walker, R. A., E. T. O'Brien, N. K. Pryer, M. Soboeiro, W. A. Voter, H. P. Erickson, and E. D. Salmon. 1988. J. Cell Biol. 107:1437-1448.). We conclude that during elongation, both plus and minus ends are stabilized by a short region (approximately 200 dimers or less) and that the size of the stable cap is independent of 10-fold variation in elongation rate. These results eliminate models of dynamic instability which predict extensive "build-up" stabilizing caps and support models which constrain the cap to the elongating tip. We propose that the cell may take advantage of such an assembly mechanism by using "catastrophe factors" that can promote frequent catastrophe even at high elongation rates by transiently binding to microtubule ends and briefly inhibiting GTP-tubulin association.

Analysis of the Mechanism of Microtubule Dynamic Instability Using a UV Microbeam to Sever Elongating Microtubules

1988 ◽  
Vol 46 ◽  
pp. 122-123
Author(s):  
R.A Walker ◽  
S. Inoue ◽  
E.D. Salmon
Keyword(s):  
Dynamic Instability ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis ◽  
Abrupt Transition ◽  
Microtubule Associated Proteins ◽  
Asymmetrical Structure ◽  
Associated Proteins

Microtubules polymerized in vitro from tubulin purified free of microtubule-associated proteins exhibit dynamic instability (1,2,3). Free microtubule ends exist in persistent phases of elongation or rapid shortening with infrequent, but, abrupt transitions between these phases. The abrupt transition from elongation to rapid shortening is termed catastrophe and the abrupt transition from rapid shortening to elongation is termed rescue. A microtubule is an asymmetrical structure. The plus end grows faster than the minus end. The frequency of catastrophe of the plus end is somewhat greater than the minus end, while the frequency of rescue of the plus end in much lower than for the minus end (4).The mechanism of catastrophe is controversial, but for both the plus and minus microtubule ends, catastrophe is thought to be dependent on GTP hydrolysis. Microtubule elongation occurs by the association of tubulin-GTP subunits to the growing end. Sometime after incorporation into an elongating microtubule end, the GTP is hydrolyzed to GDP, yielding a core of tubulin-GDP capped by tubulin-GTP (“GTP-cap”).

Self-Organized Criticality and Dynamic Instability of Microtubule Growth

1995 ◽  
Vol 50 (9-10) ◽  
pp. 739-740 ◽  
Author(s):  
Peter Babinec ◽  
Melánia Babincová
Keyword(s):  
Power Law ◽  
Dynamic Instability ◽  
Relative Number ◽  
Self Organized ◽  
Self Organized Criticality ◽  
Microtubule Growth

Abstract We have shown that the distribution of lengths of site nucleated microtubules obey an algebraic power law relationship D(s) = As-τ, where D(s) is relative number of microtubules with length 5, A and τ are constants. This relationship indicates the possibility of a self-organized criticality in the dynamic instability of microtubule growth

Mathematical modeling of microtubule dynamic instability: new insight into the link between gtp-hydrolysis and microtubule aging

2018 ◽  
Vol 52 (6) ◽  
pp. 2433-2456 ◽  
Author(s):  
Ayuna Barlukova ◽  
Diana White ◽  
Gérard Henry ◽  
Stéphane Honoré ◽  
Florence Hubert
Keyword(s):  
Dynamic Instability ◽  
Dynamic Properties ◽  
Model Parameters ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis ◽  
Unique Type ◽  
Microtubule Targeting Agents ◽  
Age Dependent ◽  
Type Of Behavior ◽  
Insight Into

Microtubules (MTs) are protein polymers that exhibit a unique type of behavior referred to as dynamic instability. That is, they undergo periods of growth (through the addition of GTP-tubulin) and shortening (through the subtraction of GDP-tubulin). Shortening events are very fast, where this transition is referred to as a catastrophe. There are many processes that regulate MT dynamic instability, however, recent experiments show that MT dynamics may be highly regulated by a MTs age, where young MTs are less likely to undergo shortening events than older ones. In this paper, we develop a novel modeling approach to describe how the age of a MT affects its dynamic properties. In particular, we extend on a previously developed model that describes MT dynamics, by proposing a new concept for GTP-tubulin hydrolysis (the process by which newly incorporated GTP-tubulin is hydrolyzed to lower energy GDP-tubulin). In particular, we assume that hydrolysis is mainly vectorial, age-dependent and delayed according to the GTP-tubulin incorporation into the MT. Through numerical simulation, we are able to show how MT age affects certain properties that define MT dynamics. For example, simulations illustrate how the aging process leads to an increase in the rate of GTP-tubulin hydrolysis for older MTs, as well as increases in catastrophe frequency. Also, since it has been found that MT dynamic instability is affected by chemotherapy microtubule-targeting agents (MTAs), we highlight the fact that our model can be used to investigate the action of MTAs on MT dynamics by varying certain model parameters.

scholarly journals Microtubule dynamic instability: A new model with coupled GTP hydrolysis and multistep catastrophe

BioEssays ◽  
2013 ◽  
Vol 35 (5) ◽  
pp. 452-461 ◽  
Author(s):  
Hugo Bowne‐Anderson ◽  
Marija Zanic ◽  
Monika Kauer ◽  
Jonathon Howard
Keyword(s):  
Dynamic Instability ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis ◽  
New Model

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.

scholarly journals Dominant-Lethal α-Tubulin Mutants Defective in Microtubule Depolymerization in Yeast

2001 ◽  
Vol 12 (12) ◽  
pp. 3973-3986 ◽  
Author(s):  
Kirk R. Anders ◽  
David Botstein
Keyword(s):  
Dynamic Instability ◽  
Time Lapse ◽  
Inducible Promoter ◽  
Spindle Pole ◽  
Yeast Cells ◽  
Microtubule Depolymerization ◽  
Gtp Hydrolysis ◽  
Mutant Proteins ◽  
Gtpase Activation ◽  
Β Tubulin

The dynamic instability of microtubules has long been understood to depend on the hydrolysis of GTP bound to β-tubulin, an event stimulated by polymerization and necessary for depolymerization. Crystallographic studies of tubulin show that GTP is bound by β-tubulin at the longitudinal dimer-dimer interface and contacts particular α-tubulin residues in the next dimer along the protofilament. This structural arrangement suggests that these contacts could account for assembly-stimulated GTP hydrolysis. As a test of this hypothesis, we examined, in yeast cells, the effect of mutating the α-tubulin residues predicted, on structural grounds, to be involved in GTPase activation. Mutation of these residues to alanine (i.e., D252A and E255A) created poisonous α-tubulins that caused lethality even as minor components of the α-tubulin pool. When the mutant α-tubulins were expressed from the galactose-inducible promoter ofGAL1, cells rapidly acquired aberrant microtubule structures. Cytoplasmic microtubules were largely bundled, spindle assembly was inhibited, preexisting spindles failed to completely elongate, and occasional, stable microtubules were observed unattached to spindle pole bodies. Time-lapse microscopy showed that microtubule dynamics had ceased. Microtubules containing the mutant proteins did not depolymerize, even in the presence of nocodazole. These data support the view that α-tubulin is a GTPase-activating protein that acts, during microtubule polymerization, to stimulate GTP hydrolysis in β-tubulin and thereby account for the dynamic instability of microtubules.

scholarly journals Ahead of the Curve: New Insights into Microtubule Dynamics

F1000Research ◽  
2016 ◽  
Vol 5 ◽  
pp. 314 ◽  
Author(s):  
Ryoma Ohi ◽  
Marija Zanic
Keyword(s):  
Structural Biology ◽  
Dynamic Instability ◽  
Microtubule Dynamics ◽  
Cell Physiology ◽  
Gtp Hydrolysis ◽  
Key Features ◽  
To Come ◽  
Induced Changes ◽  
Tubulin Structure ◽  
Intense Research

Microtubule dynamics are fundamental for many aspects of cell physiology, but their mechanistic underpinnings remain unclear despite 40 years of intense research. In recent years, the continued union of reconstitution biochemistry, structural biology, and modeling has yielded important discoveries that deepen our understanding of microtubule dynamics. These studies, which we review here, underscore the importance of GTP hydrolysis-induced changes in tubulin structure as microtubules assemble, and highlight the fact that each aspect of microtubule behavior is the output of complex, multi-step processes. Although this body of work moves us closer to appreciating the key features of microtubule biochemistry that drive dynamic instability, the divide between our understanding of microtubules in isolation versus within the cellular milieu remains vast. Bridging this gap will serve as fertile grounds of cytoskeleton-focused research for many years to come.

scholarly journals Abstract P-33: Structural Basis for the Growing Microtubule End Recognition by End Binding Proteins

2021 ◽  
Vol 11 (Suppl_1) ◽  
pp. S26-S26
Author(s):  
Alena Korshunova
Keyword(s):  
Amino Acids ◽  
Phylogenetic Analysis ◽  
Amino Acid ◽  
Molecular Mechanism ◽  
Binding Proteins ◽  
Dynamic Instability ◽  
3D Structure ◽  
Structural Basis ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis

Background: Eukaryotic end binding proteins (EBs) can follow the growing microtubule end. EBs play a crucial role in microtubule dynamic instability and promote simultaneously growth rate and catastrophe frequency. It makes EB-like proteins perspective drag targets for a wide number of diseases. But the molecular mechanism of tip tracking by EB-like proteins remains unknown. Studies of mutants have revealed that the conservative amino acid Q102 (numbering relative to the human EB1 protein) plays a key role in the recognition of the growing microtubule end. However, the 3D structure studies revealed that this amino acid has no bonds with tubulin. In this work, we performed structural and phylogenetic analysis of EBs proteins to identify a possible molecular mechanism behind the plus end tracking. Methods: UCSF Chimera10 was used for structural analysis. Phylogenetic analysis was performed with MEGA X software. 3D structures of EBs and microtubules with different states of GTP hydrolysis were used (pdb 3JAK, 3JAS, 3JAT, 3JAW, 3JAL, 3JAR, 6DPU, 6DPV, 6DPW). Results: We have shown that two conservative amino acids (K100, E106) should play an important role in the recognition of the microtubule plus end in addition to Q102. It was concluded that these amino acids together form the plus-end «navigation site» of EBs. Analysis of possible interaction of the «navigation site» amino acids with microtubules in different conformational states suggested that the main mechanism of growing microtubule end recognition is not due to an affinity increase for a certain state of tubulin in microtubules at their end, but it due to a significant affinity decrease in other parts of the microtubule as a result of steric clashes. Conclusion: Thus, the results of the analysis suggested the possible molecular mechanism that provides the tip tracking by EB-like proteins and allowed us to identify the key amino acids of this mechanism.

scholarly journals Structural transitions in the GTP cap visualized by cryo-EM of catalytically inactive microtubules

2021 ◽  
Author(s):  
Benjamin J LaFrance ◽  
Johanna Roostalu ◽  
Gil Henkin ◽  
Basil J Greber ◽  
Rui Zhang ◽  
...  
Keyword(s):  
Amino Acids ◽  
High Resolution ◽  
Conformational Changes ◽  
Binding Proteins ◽  
Dynamic Instability ◽  
Structural Transitions ◽  
Gtp Hydrolysis ◽  
Tirf Microscopy ◽  
Mechanistic Insight ◽  
Catalytically Active

Microtubules (MTs) are polymers of alphabeta-tubulin heterodimers that stochastically switch between growth and shrinkage phases. This dynamic instability is critically important for MT function. It is believed that GTP hydrolysis within the MT lattice is accompanied by destabilizing conformational changes, and that MT stability depends on a transiently existing GTP cap at the growing MT end. Here we use cryo-EM and TIRF microscopy of GTP hydrolysis-deficient MTs assembled from mutant recombinant human tubulin to investigate the structure of a GTP-bound MT lattice. We find that the GTP-MT lattice of two mutants in which the catalytically active glutamate in α-tubulin was substituted by inactive amino acids (E254A and E254N) is remarkably plastic. Undecorated E254A and E254N MTs with 13 protofilaments both have an expanded lattice, but display opposite protofilament twists, making these lattices distinct from the compacted lattice of wildtype GDP-MTs. End binding proteins of the EB family have the ability to compact both mutant GTP-lattices and to stabilize a negative twist, suggesting that they promote this transition also in the GTP cap of wildtype MTs, thereby contributing to the maturation of the MT structure. We also find that the MT seam appears to be stabilized in mutant GTP-MTs and destabilized in GDP-MTs, supporting the proposal that the seam plays an important role in MT stability. Together, these first high-resolution structures of truly GTP-bound MTs add mechanistic insight to our understanding of MT dynamic instability.

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