1
|
Hammarin G, Norder P, Harimoorthy R, Chen G, Berntsen P, Widlund PO, Stoij C, Rodilla H, Swenson J, Brändén G, Neutze R. No observable non-thermal effect of microwave radiation on the growth of microtubules. Sci Rep 2024; 14:18286. [PMID: 39112501 PMCID: PMC11306338 DOI: 10.1038/s41598-024-68852-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 07/29/2024] [Indexed: 08/10/2024] Open
Abstract
Despite widespread public interest in the health impact of exposure to microwave radiation, studies of the influence of microwave radiation on biological samples are often inconclusive or contradictory. Here we examine the influence of microwave radiation of frequencies 3.5 GHz, 20 GHz and 29 GHz on the growth of microtubules, which are biological nanotubes that perform diverse functions in eukaryotic cells. Since microtubules are highly polar and can extend several micrometres in length, they are predicted to be sensitive to non-ionizing radiation. Moreover, it has been speculated that tubulin dimers within microtubules might rapidly toggle between different conformations, potentially participating in computational or other cooperative processes. Our data show that exposure to microwave radiation yields a microtubule growth curve that is distorted relative to control studies utilizing a homogeneous temperature jump. However, this apparent effect of non-ionizing radiation is reproduced by control experiments using an infrared laser or hot air to heat the sample and thereby mimic the thermal history of samples exposed to microwaves. As such, no non-thermal effects of microwave radiation on microtubule growth can be assigned. Our results highlight the need for appropriate control experiments in biophysical studies that may impact on the sphere of public interest.
Collapse
Affiliation(s)
- Greger Hammarin
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
| | - Per Norder
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
| | - Rajiv Harimoorthy
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
| | - Guo Chen
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Peter Berntsen
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
- Monash Health Imaging, Monash Health, Clayton, VIC, Australia
| | - Per O Widlund
- Institution of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | | | - Helena Rodilla
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg, Sweden
| | - Jan Swenson
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Gisela Brändén
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
| | - Richard Neutze
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.
| |
Collapse
|
2
|
Gudimchuk NB, Alexandrova VV. Measuring and modeling forces generated by microtubules. Biophys Rev 2023; 15:1095-1110. [PMID: 37974983 PMCID: PMC10643784 DOI: 10.1007/s12551-023-01161-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 09/25/2023] [Indexed: 11/19/2023] Open
Abstract
Tubulins are essential proteins, which are conserved across all eukaryotic species. They polymerize to form microtubules, cytoskeletal components of paramount importance for cellular mechanics. The microtubules combine an extraordinarily high flexural rigidity and a non-equilibrium behavior, manifested in their intermittent assembly and disassembly. These chemically fueled dynamics allow microtubules to generate significant pushing and pulling forces at their ends to reposition intracellular organelles, remodel membranes, bear compressive forces, and transport chromosomes during cell division. In this article, we review classical and recent studies, which have allowed the quantification of microtubule-generated forces. The measurements, to which we owe most of the quantitative information about microtubule forces, were carried out in biochemically reconstituted systems in vitro. We also discuss how mathematical and computational modeling has contributed to the interpretations of these results and shaped our understanding of the mechanisms of force production by tubulin polymerization and depolymerization.
Collapse
Affiliation(s)
- Nikita B. Gudimchuk
- Department of Physics, Lomonosov Moscow State University, Moscow, Russia
- Department of Biology, Lomonosov Moscow State University, Moscow, Russia
- Center for Theoretical Problems of Physicochemical Pharmacology, Moscow, Russia
- Pskov State University, Pskov, Russia
| | - Veronika V. Alexandrova
- Department of Physics, Lomonosov Moscow State University, Moscow, Russia
- Department of Biology, Lomonosov Moscow State University, Moscow, Russia
- Center for Theoretical Problems of Physicochemical Pharmacology, Moscow, Russia
| |
Collapse
|
3
|
Miesch J, Wimbish RT, Velluz MC, Aumeier C. Phase separation of +TIP networks regulates microtubule dynamics. Proc Natl Acad Sci U S A 2023; 120:e2301457120. [PMID: 37603768 PMCID: PMC10469336 DOI: 10.1073/pnas.2301457120] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 06/12/2023] [Indexed: 08/23/2023] Open
Abstract
Regulation of microtubule dynamics is essential for diverse cellular functions, and proteins that bind to dynamic microtubule ends can regulate network dynamics. Here, we show that two conserved microtubule end-binding proteins, CLIP-170 and EB3, undergo phase separation and form dense liquid networks. When CLIP-170 and EB3 act together, the multivalency of the network increases, which synergistically increases the amount of protein in the dense phase. In vitro and in cells, these liquid networks can concentrate tubulin. In vitro, in the presence of microtubules, phase separation of EB3/CLIP-170 can enrich tubulin all along the microtubule. In this condition, microtubule growth speed increases up to twofold and the frequency of depolymerization events are strongly reduced compared to conditions in which there is no phase separation. Our data show that phase separation of EB3/CLIP-170 adds an additional layer of regulation to the control of microtubule growth dynamics.
Collapse
Affiliation(s)
- Julie Miesch
- Department of Biochemistry, University of Geneva, Geneva1211, Switzerland
| | - Robert T. Wimbish
- Department of Biochemistry, University of Geneva, Geneva1211, Switzerland
| | | | - Charlotte Aumeier
- Department of Biochemistry, University of Geneva, Geneva1211, Switzerland
| |
Collapse
|
4
|
Luchniak A, Kuo YW, McGuinness C, Sutradhar S, Orbach R, Mahamdeh M, Howard J. Dynamic microtubules slow down during their shrinkage phase. Biophys J 2023; 122:616-623. [PMID: 36659852 PMCID: PMC9989939 DOI: 10.1016/j.bpj.2023.01.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 11/25/2022] [Accepted: 01/17/2023] [Indexed: 01/21/2023] Open
Abstract
Microtubules are dynamic polymers that undergo stochastic transitions between growing and shrinking phases. The structural and chemical properties of these phases remain poorly understood. The transition from growth to shrinkage, termed catastrophe, is not a first-order reaction but rather a multistep process whose frequency increases with the growth time: the microtubule ages as the older microtubule tip becomes more unstable. Aging shows that the growing phase is not a single state but comprises several substates of increasing instability. To investigate whether the shrinking phase is also multistate, we characterized the kinetics of microtubule shrinkage following catastrophe using an in vitro reconstitution assay with purified tubulins. We found that the shrinkage speed is highly variable across microtubules and that the shrinkage speed of individual microtubules slows down over time by as much as several fold. The shrinkage slowdown was observed in both fluorescently labeled and unlabeled microtubules as well as in microtubules polymerized from tubulin purified from different species, suggesting that the shrinkage slowdown is a general property of microtubules. These results indicate that microtubule shrinkage, like catastrophe, is time dependent and that the shrinking microtubule tip passes through a succession of states of increasing stability. We hypothesize that the shrinkage slowdown is due to destabilizing events that took place during growth, which led to multistep catastrophe. This suggests that the aging associated with growth is also manifested during shrinkage, with the older, more unstable growing tip being associated with a faster depolymerizing shrinking tip.
Collapse
Affiliation(s)
- Anna Luchniak
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Yin-Wei Kuo
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Catherine McGuinness
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Sabyasachi Sutradhar
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Ron Orbach
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Mohammed Mahamdeh
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Jonathon Howard
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut.
| |
Collapse
|
5
|
Farmer VJ, Zanic M. Beyond the GTP-cap: Elucidating the molecular mechanisms of microtubule catastrophe. Bioessays 2023; 45:e2200081. [PMID: 36398561 PMCID: PMC10648283 DOI: 10.1002/bies.202200081] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 11/03/2022] [Accepted: 11/04/2022] [Indexed: 11/19/2022]
Abstract
Almost 40 years since the discovery of microtubule dynamic instability, the molecular mechanisms underlying microtubule dynamics remain an area of intense research interest. The "standard model" of microtubule dynamics implicates a "cap" of GTP-bound tubulin dimers at the growing microtubule end as the main determinant of microtubule stability. Loss of the GTP-cap leads to microtubule "catastrophe," a switch-like transition from microtubule growth to shrinkage. However, recent studies, using biochemical in vitro reconstitution, cryo-EM, and computational modeling approaches, challenge the simple GTP-cap model. Instead, a new perspective on the mechanisms of microtubule dynamics is emerging. In this view, highly dynamic transitions between different structural conformations of the growing microtubule end - which may or may not be directly linked to the nucleotide content at the microtubule end - ultimately drive microtubule catastrophe.
Collapse
Affiliation(s)
- Veronica J. Farmer
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Marija Zanic
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biomolecular and Chemical Engineering, Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
| |
Collapse
|
6
|
Tubulin Cytoskeleton in Neurodegenerative Diseases–not Only Primary Tubulinopathies. Cell Mol Neurobiol 2022:10.1007/s10571-022-01304-6. [DOI: 10.1007/s10571-022-01304-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Accepted: 11/01/2022] [Indexed: 11/11/2022]
Abstract
AbstractNeurodegenerative diseases represent a large group of disorders characterized by gradual loss of neurons and functions of the central nervous systems. Their course is usually severe, leading to high morbidity and subsequent inability of patients to independent functioning. Vast majority of neurodegenerative diseases is currently untreatable, and only some symptomatic drugs are available which efficacy is usually very limited. To develop novel therapies for this group of diseases, it is crucial to understand their pathogenesis and to recognize factors which can influence the disease course. One of cellular structures which dysfunction appears to be relatively poorly understood in the light of neurodegenerative diseases is tubulin cytoskeleton. On the other hand, its changes, both structural and functional, can considerably influence cell physiology, leading to pathological processes occurring also in neurons. In this review, we summarize and discuss dysfunctions of tubulin cytoskeleton in various neurodegenerative diseases different than primary tubulinopathies (caused by mutations in genes encoding the components of the tubulin cytoskeleton), especially Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, prion diseases, and neuronopathic mucopolysaccharidoses. It is also proposed that correction of these disorders might attenuate the progress of specific diseases, thus, finding newly recognized molecular targets for potential drugs might become possible.
Collapse
|
7
|
Cleary JM, Kim T, Cook ASI, McCormick LA, Hancock WO, Rice LM. Measurements and simulations of microtubule growth imply strong longitudinal interactions and reveal a role for GDP on the elongating end. eLife 2022; 11:75931. [PMID: 35420545 PMCID: PMC9064298 DOI: 10.7554/elife.75931] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 04/13/2022] [Indexed: 11/13/2022] Open
Abstract
Microtubule polymerization dynamics result from the biochemical interactions of αβ-tubulin with the polymer end, but a quantitative understanding has been challenging to establish. We used interference reflection microscopy to make improved measurements of microtubule growth rates and growth fluctuations in the presence and absence of GTP hydrolysis. In the absence of GTP hydrolysis, microtubules grew steadily with very low fluctuations. These data were best described by a computational model implementing slow assembly kinetics, such that the rate of microtubule elongation is primarily limited by the rate of αβ-tubulin associations. With GTPase present, microtubules displayed substantially larger growth fluctuations than expected based on the no GTPase measurements. Our modeling showed that these larger fluctuations occurred because exposure of GDP-tubulin on the microtubule end transiently 'poisoned' growth, yielding a wider range of growth rates compared to GTP only conditions. Our experiments and modeling point to slow association kinetics (strong longitudinal interactions), such that drugs and regulatory proteins that alter microtubule dynamics could do so by modulating either the association or dissociation rate of tubulin from the microtubule tip. By causing slower growth, exposure of GDP tubulin at the growing microtubule end may be an important early event determining catastrophe.
Collapse
Affiliation(s)
- Joseph M Cleary
- Department of Biomedical Engineering, Pennsylvania State University, University Park, United States
| | - Tae Kim
- Departments of Biophysics and Biochemistry, The University of Texas Southwestern Medical Center, Dallas, United States
| | - Annan S I Cook
- Department of Biomedical Engineering, Pennsylvania State University, University Park, United States
| | - Lauren A McCormick
- Departments of Biophysics and Biochemistry, The University of Texas Southwestern Medical Center, Dallas, United States
| | - William O Hancock
- Department of Biomedical Engineering, Pennsylvania State University, University Park, United States
| | - Luke M Rice
- Departments of Biophysics and Biochemistry, The University of Texas Southwestern Medical Center, Dallas, United States
| |
Collapse
|
8
|
Kinesin-14 motors participate in a force balance at microtubule plus-ends to regulate dynamic instability. Proc Natl Acad Sci U S A 2022; 119:2108046119. [PMID: 35173049 PMCID: PMC8872730 DOI: 10.1073/pnas.2108046119] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/03/2022] [Indexed: 01/08/2023] Open
Abstract
Kinesin-14 motors represent an essential class of molecular motors that bind to microtubules and then walk toward the microtubule minus-end. However, whether these motors can interact with growing plus-ends of microtubules to impact the lengthening of microtubules remains unknown. We found that Kinesin-14 motors could bind to a protein that resides at growing microtubule plus-ends and then pull this protein away from the growing end. This interaction acted to disrupt microtubule growth and decrease microtubule lengths in cells, likely by exerting minus-end–directed forces at the microtubule tip to alter the configuration of the growing microtubule plus-end. This work demonstrates general principles for the diverse roles that force-generating molecular motors can play in regulating cellular processes. Kinesin-14 molecular motors represent an essential class of proteins that bind microtubules and walk toward their minus-ends. Previous studies have described important roles for Kinesin-14 motors at microtubule minus-ends, but their role in regulating plus-end dynamics remains controversial. Kinesin-14 motors have been shown to bind the EB family of microtubule plus-end binding proteins, suggesting that these minus-end–directed motors could interact with growing microtubule plus-ends. In this work, we explored the role of minus-end–directed Kinesin-14 motor forces in controlling plus-end microtubule dynamics. In cells, a Kinesin-14 mutant with reduced affinity to EB proteins led to increased microtubule lengths. Cell-free biophysical microscopy assays were performed using Kinesin-14 motors and an EB family marker of growing microtubule plus-ends, Mal3, which revealed that when Kinesin-14 motors bound to Mal3 at growing microtubule plus-ends, the motors subsequently walked toward the minus-end, and Mal3 was pulled away from the growing microtubule tip. Strikingly, these interactions resulted in an approximately twofold decrease in the expected postinteraction microtubule lifetime. Furthermore, generic minus-end–directed tension forces, generated by tethering growing plus-ends to the coverslip using λ-DNA, led to an approximately sevenfold decrease in the expected postinteraction microtubule growth length. In contrast, the inhibition of Kinesin-14 minus-end–directed motility led to extended tip interactions and to an increase in the expected postinteraction microtubule lifetime, indicating that plus-ends were stabilized by nonmotile Kinesin-14 motors. Together, we find that Kinesin-14 motors participate in a force balance at microtubule plus-ends to regulate microtubule lengths in cells.
Collapse
|
9
|
Mahserejian SM, Scripture JP, Mauro AJ, Lawrence EJ, Jonasson EM, Murray KS, Li J, Gardner M, Alber M, Zanic M, Goodson HV. Quantification of Microtubule Stutters: Dynamic Instability Behaviors that are Strongly Associated with Catastrophe. Mol Biol Cell 2022; 33:ar22. [PMID: 35108073 PMCID: PMC9250389 DOI: 10.1091/mbc.e20-06-0348] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Microtubules (MTs) are cytoskeletal fibers that undergo dynamic instability (DI), a remarkable process involving phases of growth and shortening separated by stochastic transitions called catastrophe and rescue. Dissecting DI mechanism(s) requires first characterizing and quantifying these dynamics, a subjective process that often ignores complexity in MT behavior. We present a Statistical Tool for Automated Dynamic Instability Analysis (STADIA) that identifies and quantifies not only growth and shortening, but also a category of intermediate behaviors that we term “stutters.” During stutters, the rate of MT length change tends to be smaller in magnitude than during typical growth or shortening phases. Quantifying stutters and other behaviors with STADIA demonstrates that stutters precede most catastrophes in our in vitro experiments and dimer-scale MT simulations, suggesting that stutters are mechanistically involved in catastrophes. Related to this idea, we show that the anticatastrophe factor CLASP2γ works by promoting the return of stuttering MTs to growth. STADIA enables more comprehensive and data-driven analysis of MT dynamics compared with previous methods. The treatment of stutters as distinct and quantifiable DI behaviors provides new opportunities for analyzing mechanisms of MT dynamics and their regulation by binding proteins.
Collapse
Affiliation(s)
- Shant M Mahserejian
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, IN 46556.,Pacific Northwest National Laboratory, Richland, WA 99352
| | - Jared P Scripture
- Department of Chemistry and Biochemistry, University of Notre Dame, IN 46556
| | - Ava J Mauro
- Department of Chemistry and Biochemistry, University of Notre Dame, IN 46556.,Department of Mathematics and Statistics, University of Massachusetts Amherst, Amherst MA, 01003
| | - Elizabeth J Lawrence
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240
| | - Erin M Jonasson
- Department of Chemistry and Biochemistry, University of Notre Dame, IN 46556.,Department of Natural Sciences, Saint Martin's University, Lacey, WA 98503
| | - Kristopher S Murray
- Department of Chemistry and Biochemistry, University of Notre Dame, IN 46556
| | - Jun Li
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, IN 46556
| | - Melissa Gardner
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455
| | - Mark Alber
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, IN 46556.,Department of Mathematics, University of California Riverside, Riverside, CA 92521
| | - Marija Zanic
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240.,Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235.,Department of Biochemistry, Vanderbilt University, Nashville, TN 37205
| | - Holly V Goodson
- Department of Chemistry and Biochemistry, University of Notre Dame, IN 46556
| |
Collapse
|
10
|
Hornak I, Rieger H. Stochastic model of T Cell repolarization during target elimination (II). Biophys J 2022; 121:1246-1265. [PMID: 35196513 PMCID: PMC9034251 DOI: 10.1016/j.bpj.2022.02.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/08/2021] [Accepted: 02/16/2022] [Indexed: 11/16/2022] Open
Abstract
Cytotoxic T lymphocytes (T cells) and natural killer cells form a tight contact, the immunological synapse (IS), with target cells, where they release their lytic granules containing perforin/granzyme and cytokine-containing vesicles. During this process the cell repolarizes and moves the microtubule organizing center (MTOC) toward the IS. In the first part of our work we developed a computational model for the molecular-motor-driven motion of the microtubule cytoskeleton during T cell polarization and analyzed the effects of cortical-sliding and capture-shrinkage mechanisms. Here we use this model to analyze the dynamics of the MTOC repositioning in situations in which 1) the IS is in an arbitrary position with respect to the initial position of the MTOC and 2) the T cell has two IS at two arbitrary positions. In the case of one IS, we found that the initial position determines which mechanism is dominant and that the time of repositioning does not rise monotonously with the MTOC-IS distance. In the case of two IS, we observe several scenarios that have also been reported experimentally: the MTOC alternates stochastically (but with a well-defined average transition time) between the two IS; it wiggles in between the two IS without transiting to one of the two; or it is at some point pulled to one of the two IS and stays there. Our model allows one to predict which scenario emerges in dependency of the mechanisms in action and the number of dyneins present. We report that the presence of capture-shrinkage mechanism in at least one IS is necessary to assure the transitions in every cell configuration. Moreover, the frequency of transitions does not decrease with the distance between the two IS and is the highest when both mechanisms are present in both IS.
Collapse
Affiliation(s)
- Ivan Hornak
- Department of Theoretical Physics, Center for Biophysics, Saarland University, Saarbrücken, Germany.
| | - Heiko Rieger
- Department of Theoretical Physics, Center for Biophysics, Saarland University, Saarbrücken, Germany
| |
Collapse
|
11
|
Viscoelastic parameterization of human skin cells characterize material behavior at multiple timescales. Commun Biol 2022; 5:17. [PMID: 35017622 PMCID: PMC8752830 DOI: 10.1038/s42003-021-02959-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 12/06/2021] [Indexed: 01/22/2023] Open
Abstract
Countless biophysical studies have sought distinct markers in the cellular mechanical response that could be linked to morphogenesis, homeostasis, and disease. Here, an iterative-fitting methodology visualizes the time-dependent viscoelastic behavior of human skin cells under physiologically relevant conditions. Past investigations often involved parameterizing elastic relationships and assuming purely Hertzian contact mechanics, which fails to properly account for the rich temporal information available. We demonstrate the performance superiority of the proposed iterative viscoelastic characterization method over standard open-search approaches. Our viscoelastic measurements revealed that 2D adherent metastatic melanoma cells exhibit reduced elasticity compared to their normal counterparts—melanocytes and fibroblasts, and are significantly less viscous than fibroblasts over timescales spanning three orders of magnitude. The measured loss angle indicates clear differential viscoelastic responses across multiple timescales between the measured cells. This method provides insight into the complex viscoelastic behavior of metastatic melanoma cells relevant to better understanding cancer metastasis and aggression. Parvini, Cartagena and Solares introduce an iterative viscoelastic approach based on the generalized Maxwell and Kelvin-Voigt models. The results showed that metastatic melanoma cells had lower elasticity than normal fibroblasts and melanoma cells were less viscous than the fibroblasts over a large frequency range, enhancing the understanding of cellular responses at different frequencies.
Collapse
|
12
|
Bennett ZT, Li S, Sumer BD, Gao J. Polyvalent design in the cGAS-STING pathway. Semin Immunol 2021; 56:101580. [PMID: 34920941 PMCID: PMC8792294 DOI: 10.1016/j.smim.2021.101580] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 12/06/2021] [Accepted: 12/09/2021] [Indexed: 01/02/2023]
Abstract
Polyvalent interactions mediate the formation of higher-order macromolecular assemblies to improve the sensitivity, specificity, and temporal response of biological signals. In host defense, innate immune pathways recognize danger signals to alert host of insult or foreign invasion, while limiting aberrant activation from auto-immunity and cellular senescence. Of recent attention are the unique higher-order assemblies in the cGAS-STING pathway. Natural stimulation of cGAS enzymes by dsDNA induces phase separation and enzymatic activation for switchlike production of cGAMP. Subsequent binding of cGAMP to STING induces oligomerization of STING molecules, offering a scaffold for kinase assembly and signaling transduction. Additionally, the discovery of PC7A, a synthetic polymer which activates STING through a non-canonical biomolecular condensation, illustrates the engineering design of agonists by polyvalency principles. Herein, we discuss a mechanistic and functional comparison of natural and synthetic agonists to advance our understanding in STING signaling and highlight the principles of polyvalency in innate immune activation. The combination of exogenous cGAMP along with synthetic PC7A stimulation of STING offers a synergistic strategy in spatiotemporal orchestration of the immune milieu for a safe and effective immunotherapy against cancer.
Collapse
Affiliation(s)
- Zachary T Bennett
- Department of Pharmacology, Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Suxin Li
- Department of Pharmacology, Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Baran D Sumer
- Department of Otolaryngology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jinming Gao
- Department of Pharmacology, Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, USA; Department of Otolaryngology, University of Texas Southwestern Medical Center, Dallas, TX, USA; Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| |
Collapse
|
13
|
Abstract
Microtubules are dynamic cytoskeletal filaments composed of αβ-tubulin heterodimers. Historically, the dynamics of single tubulin interactions at the growing microtubule tip have been inferred from steady-state growth kinetics. However, recent advances in the production of recombinant tubulin and in high-resolution optical and cryo-electron microscopies have opened new windows into understanding the impacts of specific intermolecular interactions during growth. The microtubule lattice is held together by lateral and longitudinal tubulin-tubulin interactions, and these interactions are in turn regulated by the GTP hydrolysis state of the tubulin heterodimer. Furthermore, tubulin can exist in either an extended or a compacted state in the lattice. Growing evidence has led to the suggestion that binding of microtubule-associated proteins (MAPs) or motors can induce changes in tubulin conformation and that this information can be communicated through the microtubule lattice. Progress in understanding how dynamic tubulin-tubulin interactions control dynamic instability has benefitted from visualizing structures of growing microtubule plus ends and through stochastic biochemical models constrained by experimental data. Here, we review recent insights into the molecular basis of microtubule growth and discuss how MAPs and regulatory proteins alter tubulin-tubulin interactions to exert their effects on microtubule growth and stability.
Collapse
Affiliation(s)
- Joseph M Cleary
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - William O Hancock
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA.
| |
Collapse
|
14
|
Castle BT, McKibben KM, Rhoades E, Odde DJ. Tau Avoids the GTP Cap at Growing Microtubule Plus-Ends. iScience 2020; 23:101782. [PMID: 33294790 PMCID: PMC7691178 DOI: 10.1016/j.isci.2020.101782] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 09/15/2020] [Accepted: 11/04/2020] [Indexed: 10/26/2022] Open
Abstract
Plus-end tracking proteins (+TIPs) associate with the growing end of microtubules and mediate important cellular functions. The majority of +TIPs are directed to the plus-end through a family of end-binding proteins (EBs), which preferentially bind the stabilizing cap of GTP-tubulin present during microtubule growth. One outstanding question is whether there may exist other microtubule-associated proteins (MAPs) that preferentially bind specific nucleotide states of tubulin. Here, we report that the neuronal MAP tau preferentially binds GDP-tubulin (K D = 0.26 μM) over GMPCPP-tubulin (K D = 1.1 μM) in vitro, as well as GTP-tubulin at the tips of growing microtubules, causing tau binding to lag behind the plus-end both in vitro and in live cells. Thus, tau is a microtubule tip avoiding protein, establishing the framework for a possible new class of tip avoiding MAPs. We speculate that disease-relevant tau mutations may exert their phenotype by their failure to properly recognize GDP-tubulin.
Collapse
Affiliation(s)
- Brian T. Castle
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Kristen M. McKibben
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Elizabeth Rhoades
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - David J. Odde
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| |
Collapse
|
15
|
Stewman SF, Tsui KK, Ma A. Dynamic Instability from Non-equilibrium Structural Transitions on the Energy Landscape of Microtubule. Cell Syst 2020; 11:608-624.e9. [PMID: 33086051 DOI: 10.1016/j.cels.2020.09.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 09/12/2019] [Accepted: 09/25/2020] [Indexed: 11/30/2022]
Abstract
Microtubules are the backbone of the cytoskeleton and vital to numerous cellular processes. The central dogma of microtubules is that all their functions are driven by dynamic instability, but its mechanism has remained unresolved for over 30 years because of conceptual difficulties inherent in the dominant GTP-cap framework. We present a physically rigorous structural mechanochemical model: dynamic instability is driven by non-equilibrium transitions between the bent (B), straight (S), and curved (C) forms of tubulin monomers and longitudinal interfaces in the two-dimensional lattice of microtubule. All the different phenomena (growth, shortening, catastrophe, rescue, and pausing) are controlled by the kinetic pathways for B↔S↔C transitions and corresponding energy landscapes. Different kinetics at minus end are due to different B↔S↔C pathways imposed by the polarity of microtubule lattice. This model enables us to reproduce all the observed phenomena of dynamic instability of purified tubulins in kinetic simulations.
Collapse
Affiliation(s)
- Shannon F Stewman
- Department of Bioengineering, the University of Illinois at Chicago, 851 South Morgan Street, Chicago, IL 60607, USA
| | - Kenneth K Tsui
- Department of Bioengineering, the University of Illinois at Chicago, 851 South Morgan Street, Chicago, IL 60607, USA
| | - Ao Ma
- Department of Bioengineering, the University of Illinois at Chicago, 851 South Morgan Street, Chicago, IL 60607, USA.
| |
Collapse
|
16
|
Gudimchuk NB, Ulyanov EV, O'Toole E, Page CL, Vinogradov DS, Morgan G, Li G, Moore JK, Szczesna E, Roll-Mecak A, Ataullakhanov FI, Richard McIntosh J. Mechanisms of microtubule dynamics and force generation examined with computational modeling and electron cryotomography. Nat Commun 2020; 11:3765. [PMID: 32724196 PMCID: PMC7387542 DOI: 10.1038/s41467-020-17553-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 07/08/2020] [Indexed: 01/15/2023] Open
Abstract
Microtubules are dynamic tubulin polymers responsible for many cellular processes, including the capture and segregation of chromosomes during mitosis. In contrast to textbook models of tubulin self-assembly, we have recently demonstrated that microtubules elongate by addition of bent guanosine triphosphate tubulin to the tips of curving protofilaments. Here we explore this mechanism of microtubule growth using Brownian dynamics modeling and electron cryotomography. The previously described flaring shapes of growing microtubule tips are remarkably consistent under various assembly conditions, including different tubulin concentrations, the presence or absence of a polymerization catalyst or tubulin-binding drugs. Simulations indicate that development of substantial forces during microtubule growth and shortening requires a high activation energy barrier in lateral tubulin-tubulin interactions. Modeling offers a mechanism to explain kinetochore coupling to growing microtubule tips under assisting force, and it predicts a load-dependent acceleration of microtubule assembly, providing a role for the flared morphology of growing microtubule ends.
Collapse
Affiliation(s)
- Nikita B Gudimchuk
- Department of Physics, Lomonosov Moscow State University, Moscow, Russia.
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, Moscow, Russia.
- Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia.
| | - Evgeni V Ulyanov
- Department of Physics, Lomonosov Moscow State University, Moscow, Russia
| | - Eileen O'Toole
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA
| | - Cynthia L Page
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA
| | - Dmitrii S Vinogradov
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, Moscow, Russia
| | - Garry Morgan
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA
| | - Gabriella Li
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Ewa Szczesna
- Cell Biology and Biophysics Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
| | - Antonina Roll-Mecak
- Cell Biology and Biophysics Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
| | - Fazoil I Ataullakhanov
- Department of Physics, Lomonosov Moscow State University, Moscow, Russia
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, Moscow, Russia
- Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - J Richard McIntosh
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA
| |
Collapse
|
17
|
Estévez-Gallego J, Josa-Prado F, Ku S, Buey RM, Balaguer FA, Prota AE, Lucena-Agell D, Kamma-Lorger C, Yagi T, Iwamoto H, Duchesne L, Barasoain I, Steinmetz MO, Chrétien D, Kamimura S, Díaz JF, Oliva MA. Structural model for differential cap maturation at growing microtubule ends. eLife 2020; 9:50155. [PMID: 32151315 PMCID: PMC7064335 DOI: 10.7554/elife.50155] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 01/25/2020] [Indexed: 11/13/2022] Open
Abstract
Microtubules (MTs) are hollow cylinders made of tubulin, a GTPase responsible for essential functions during cell growth and division, and thus, key target for anti-tumor drugs. In MTs, GTP hydrolysis triggers structural changes in the lattice, which are responsible for interaction with regulatory factors. The stabilizing GTP-cap is a hallmark of MTs and the mechanism of the chemical-structural link between the GTP hydrolysis site and the MT lattice is a matter of debate. We have analyzed the structure of tubulin and MTs assembled in the presence of fluoride salts that mimic the GTP-bound and GDP•Pi transition states. Our results challenge current models because tubulin does not change axial length upon GTP hydrolysis. Moreover, analysis of the structure of MTs assembled in the presence of several nucleotide analogues and of taxol allows us to propose that previously described lattice expansion could be a post-hydrolysis stage involved in Pi release.
Collapse
Affiliation(s)
- Juan Estévez-Gallego
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Fernando Josa-Prado
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Siou Ku
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR 6290, Rennes, France
| | - Ruben M Buey
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain.,Departamento de Microbiología y Genética, Universidad de Salamanca-Campus Miguel de Unamuno, Salamanca, Spain
| | - Francisco A Balaguer
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Andrea E Prota
- Division of Biology and Chemistry, Laboratory of Biomolecular Research, Paul Scherrer Institut, Villigen, Switzerland
| | - Daniel Lucena-Agell
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | | | - Toshiki Yagi
- Department of Life Sciences, Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Hiroyuki Iwamoto
- Diffraction and Scattering Division, Japan Synchrotron Radiation Research Institute, Hyogo, Japan
| | - Laurence Duchesne
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR 6290, Rennes, France
| | - Isabel Barasoain
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Michel O Steinmetz
- Division of Biology and Chemistry, Laboratory of Biomolecular Research, Paul Scherrer Institut, Villigen, Switzerland.,University of Basel, Biozentrum, Basel, Switzerland
| | - Denis Chrétien
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR 6290, Rennes, France
| | - Shinji Kamimura
- Department of Biological Sciences, Faculty of Science and Engineering, Chuo University, Tokyo, Japan
| | - J Fernando Díaz
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Maria A Oliva
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| |
Collapse
|
18
|
Roostalu J, Thomas C, Cade NI, Kunzelmann S, Taylor IA, Surrey T. The speed of GTP hydrolysis determines GTP cap size and controls microtubule stability. eLife 2020; 9:e51992. [PMID: 32053491 PMCID: PMC7018511 DOI: 10.7554/elife.51992] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 01/25/2020] [Indexed: 11/30/2022] Open
Abstract
Microtubules are cytoskeletal polymers whose function depends on their property to switch between states of growth and shrinkage. Growing microtubules are thought to be stabilized by a GTP cap at their ends. The nature of this cap, however, is still poorly understood. End Binding proteins (EBs) recruit a diverse range of regulators of microtubule function to growing microtubule ends. Whether the EB binding region is identical to the GTP cap is unclear. Using mutated human tubulin with blocked GTP hydrolysis, we demonstrate that EBs bind with high affinity to the GTP conformation of microtubules. Slowing-down GTP hydrolysis leads to extended GTP caps. We find that cap length determines microtubule stability and that the microtubule conformation changes gradually in the cap as GTP is hydrolyzed. These results demonstrate the critical importance of the kinetics of GTP hydrolysis for microtubule stability and establish that the GTP cap coincides with the EB-binding region.
Collapse
Affiliation(s)
| | | | | | | | | | - Thomas Surrey
- The Francis Crick InstituteLondonUnited Kingdom
- Centre for Genomic RegulationBarcelona Institute of Science and TechnologyBarcelonaSpain
- ICREABarcelonaSpain
| |
Collapse
|
19
|
Lee CT, Terentjev EM. Structural effects of cap, crack, and intrinsic curvature on the microtubule catastrophe kinetics. J Chem Phys 2019; 151:135101. [PMID: 31594313 DOI: 10.1063/1.5122304] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Microtubules (MTs) experience an effect called "catastrophe," which is the transition from the MT growth to a sudden dramatic shrinkage in length. The straight guanosine triphosphate (GTP)-tubulin cap at the filament tip and the intrinsic curvature of guanosine diphosphate (GDP)-tubulins are known to be the key thermodynamic factors that determine MT catastrophe, while the hydrolysis of this GTP-cap acts as the kinetic control of the process. Although several theoretical models have been developed, assuming the catastrophe occurs when the GTP-cap shrinks to a minimal stabilizing size, the structural effect of the GTP-cap and GDP-curvature is not explicitly included; thus, their influence on catastrophe kinetics remains less understood. To investigate this structural effect, we apply a single-protofilament model with one GTP-cap while assuming a random hydrolysis mechanism and take the occurrence of a crack in the lateral bonds between neighboring protofilaments as the onset of the catastrophe. Therein, we find the effective potential of the tip along the peel-off direction and formulate the catastrophe kinetics as a mean first-passage time problem, subject to thermal fluctuations. We consider cases with and without a compressive force on the MT tip, both of which give a quadratic effective potential, making MT catastrophe an Ornstein-Uhlenbeck process in our formalism. In the free-standing case, the mean catastrophe time has a sensitive tubulin-concentration dependence, similar to a double-exponential function, and agrees well with the experiment. For a compressed MT, we find a modified exponential function of force that shortens the catastrophe time.
Collapse
Affiliation(s)
- Cheng-Tai Lee
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Eugene M Terentjev
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| |
Collapse
|
20
|
Best RL, LaPointe NE, Liang J, Ruan K, Shade MF, Wilson L, Feinstein SC. Tau isoform-specific stabilization of intermediate states during microtubule assembly and disassembly. J Biol Chem 2019; 294:12265-12280. [PMID: 31266806 DOI: 10.1074/jbc.ra119.009124] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/24/2019] [Indexed: 01/27/2023] Open
Abstract
The microtubule (MT)-associated protein tau regulates the critical growing and shortening behaviors of MTs, and its normal activity is essential for neuronal development and maintenance. Accordingly, aberrant tau action is tightly associated with Alzheimer's disease and is genetically linked to several additional neurodegenerative diseases known as tauopathies. Although tau is known to promote net MT growth and stability, the precise mechanistic details governing its regulation of MT dynamics remain unclear. Here, we have used the slowly-hydrolyzable GTP analog, guanylyl-(α,β)-methylene-diphosphonate (GMPCPP), to examine the structural effects of tau at MT ends that may otherwise be too transient to observe. The addition of both four-repeat (4R) and three-repeat (3R) tau isoforms to pre-formed GMPCPP MTs resulted in the formation of extended, multiprotofilament-wide projections at MT ends. Furthermore, at temperatures too low for assembly of bona fide MTs, both tau isoforms promoted the formation of long spiral ribbons from GMPCPP tubulin heterodimers. In addition, GMPCPP MTs undergoing cold-induced disassembly in the presence of 4R tau (and to a much lesser extent 3R tau) also formed spirals. Finally, three pathological tau mutations known to cause neurodegeneration and dementia were differentially compromised in their abilities to stabilize MT disassembly intermediates. Taken together, we propose that tau promotes the formation/stabilization of intermediate states in MT assembly and disassembly by promoting both longitudinal and lateral tubulin-tubulin contacts. We hypothesize that these activities represent fundamental aspects of tau action that normally occur at the GTP-rich ends of GTP/GDP MTs and that may be compromised in neurodegeneration-causing tau variants.
Collapse
Affiliation(s)
- Rebecca L Best
- Neuroscience Research Institute and Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California 93106
| | - Nichole E LaPointe
- Neuroscience Research Institute and Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California 93106
| | - Jiahao Liang
- Neuroscience Research Institute and Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California 93106
| | - Kevin Ruan
- Neuroscience Research Institute and Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California 93106
| | - Madeleine F Shade
- Neuroscience Research Institute and Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California 93106
| | - Leslie Wilson
- Neuroscience Research Institute and Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California 93106
| | - Stuart C Feinstein
- Neuroscience Research Institute and Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California 93106.
| |
Collapse
|
21
|
Brändén G, Hammarin G, Harimoorthy R, Johansson A, Arnlund D, Malmerberg E, Barty A, Tångefjord S, Berntsen P, DePonte DP, Seuring C, White TA, Stellato F, Bean R, Beyerlein KR, Chavas LMG, Fleckenstein H, Gati C, Ghoshdastider U, Gumprecht L, Oberthür D, Popp D, Seibert M, Tilp T, Messerschmidt M, Williams GJ, Loh ND, Chapman HN, Zwart P, Liang M, Boutet S, Robinson RC, Neutze R. Coherent diffractive imaging of microtubules using an X-ray laser. Nat Commun 2019; 10:2589. [PMID: 31197138 PMCID: PMC6565740 DOI: 10.1038/s41467-019-10448-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 05/02/2019] [Indexed: 01/09/2023] Open
Abstract
X-ray free electron lasers (XFELs) create new possibilities for structural studies of biological objects that extend beyond what is possible with synchrotron radiation. Serial femtosecond crystallography has allowed high-resolution structures to be determined from micro-meter sized crystals, whereas single particle coherent X-ray imaging requires development to extend the resolution beyond a few tens of nanometers. Here we describe an intermediate approach: the XFEL imaging of biological assemblies with helical symmetry. We collected X-ray scattering images from samples of microtubules injected across an XFEL beam using a liquid microjet, sorted these images into class averages, merged these data into a diffraction pattern extending to 2 nm resolution, and reconstructed these data into a projection image of the microtubule. Details such as the 4 nm tubulin monomer became visible in this reconstruction. These results illustrate the potential of single-molecule X-ray imaging of biological assembles with helical symmetry at room temperature.
Collapse
Affiliation(s)
- Gisela Brändén
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden.
| | - Greger Hammarin
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - Rajiv Harimoorthy
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - Alexander Johansson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - David Arnlund
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - Erik Malmerberg
- Molecular Biophysics and Integrated Bio-Imaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, 94720, Berkeley, CA, USA
| | - Anton Barty
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Stefan Tångefjord
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - Peter Berntsen
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - Daniel P DePonte
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Carolin Seuring
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany.,The Hamburg Center for Ultrafast Imaging, 22761, Hamburg, Germany
| | - Thomas A White
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Francesco Stellato
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Richard Bean
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Kenneth R Beyerlein
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Leonard M G Chavas
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Holger Fleckenstein
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Cornelius Gati
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Umesh Ghoshdastider
- Institute of Molecular and Cell Biology, Biopolis, A*STAR (Agency for Science, Technology and Research), 138673, Singapore, Singapore
| | - Lars Gumprecht
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Dominik Oberthür
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - David Popp
- Institute of Molecular and Cell Biology, Biopolis, A*STAR (Agency for Science, Technology and Research), 138673, Singapore, Singapore
| | - Marvin Seibert
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Thomas Tilp
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Marc Messerschmidt
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Garth J Williams
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - N Duane Loh
- Department of Physics, National University of Singapore, 117551, Singapore, Singapore
| | - Henry N Chapman
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany.,The Hamburg Center for Ultrafast Imaging, 22761, Hamburg, Germany.,Department of Physics, University of Hamburg, 22761, Hamburg, Germany
| | - Peter Zwart
- Molecular Biophysics and Integrated Bio-Imaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, 94720, Berkeley, CA, USA
| | - Mengning Liang
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany.,Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Sébastien Boutet
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Robert C Robinson
- Institute of Molecular and Cell Biology, Biopolis, A*STAR (Agency for Science, Technology and Research), 138673, Singapore, Singapore.,Department of Biochemistry, National University of Singapore, 117597, Singapore, Singapore.,Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530, Japan
| | - Richard Neutze
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden.
| |
Collapse
|
22
|
Orbach R, Howard J. The dynamic and structural properties of axonemal tubulins support the high length stability of cilia. Nat Commun 2019; 10:1838. [PMID: 31015426 PMCID: PMC6479064 DOI: 10.1038/s41467-019-09779-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 03/25/2019] [Indexed: 12/31/2022] Open
Abstract
Cilia and flagella play essential roles in cell motility, sensing and development. These organelles have tightly controlled lengths, and the axoneme, which forms the core structure, has exceptionally high stability. This is despite being composed of microtubules that are often characterized as highly dynamic. To understand how ciliary tubulin contribute to stability, we develop a procedure to differentially extract tubulins from different components of axonemes purified from Chlamydomonas reinhardtii, and characterize their properties. We find that the microtubules support length stability by two distinct mechanisms: low dynamicity, and unusual stability of the protofilaments. The high stability of the protofilaments manifests itself in the formation of curved tip structures, up to a few microns long. These structures likely reflect intrinsic curvature of GTP or GDP·Pi tubulin and provide structural insights into the GTP-cap. Together, our study provides insights into growth, stability and the role of post-translational modifications of axonemal microtubules. The axoneme in cilia and flagella has exceptionally high stability despite being composed of microtubules that are known to be highly dynamic. Here authors extract tubulin from different components of Chlamydomonas reinhardtii axonemes and characterize their properties.
Collapse
Affiliation(s)
- Ron Orbach
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Jonathon Howard
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.
| |
Collapse
|
23
|
Yang LZ, Yang M. Modeling Biological Oscillations: Integration of Short Reaction Pauses into a Stationary Model of a Negative Feedback Loop Generates Sustained Long Oscillations. J Comput Biol 2019; 26:1050-1066. [PMID: 30990751 DOI: 10.1089/cmb.2019.0017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Sustained oscillations are frequently observed in biological systems consisting of a negative feedback loop, but a mathematical model with two ordinary differential equations (ODE) that has a negative feedback loop structure fails to produce sustained oscillations. Only when a time delay is introduced into the system by expanding to a three-ODE model, transforming to a two-delay differential equations (DDE) model, or introducing a bistable trigger do stable oscillations present themselves. In this study, we propose another mechanism for producing sustained oscillations based on periodic reaction pauses of chemical reactions in a negative feedback system. We model the oscillatory system behavior by allowing the coefficients in the two-ODE model to be periodic functions of time-called pulsate functions-to account for reactions with go-stop pulses. We find that replacing coefficients in the two-ODE system with pulsate functions with microscale (several seconds) pauses can produce stable system-wide oscillations that have periods of approximately 1 to several hours long. We also compare our two-ODE and three-ODE models with the two-DDE, three-ODE, and three-DDE models without the pulsate functions. Our numerical experiments suggest that sustained long oscillations in biological systems with a negative feedback loop may be an intrinsic property arising from the slow diffusion-based pulsate behavior of biochemical reactions.
Collapse
Affiliation(s)
- Louis Z Yang
- Department of Finance and Business Economics, University of Southern California, Los Angeles, California
| | - Ming Yang
- Department of Plant Biology, Ecology, and Evolution, Oklahoma State University, Stillwater, Oklahoma
| |
Collapse
|
24
|
|
25
|
Direct observation of individual tubulin dimers binding to growing microtubules. Proc Natl Acad Sci U S A 2019; 116:7314-7322. [PMID: 30804205 DOI: 10.1073/pnas.1815823116] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The biochemical basis of microtubule growth has remained elusive for over 30 years despite being fundamental for both cell division and associated chemotherapy strategies. Here, we combine interferometric scattering microscopy with recombinant tubulin to monitor individual tubulins binding to and dissociating from growing microtubule tips. We make direct, single-molecule measurements of tubulin association and dissociation rates. We detect two populations of transient dwell times and determine via binding-interface mutants that they are distinguished by the formation of one interprotofilament bond. Applying a computational model, we find that slow association kinetics with strong interactions along protofilaments best recapitulate our data and, furthermore, predicts plus-end tapering. Overall, we provide the most direct and complete experimental quantification of how microtubules grow to date.
Collapse
|
26
|
Lawrence EJ, Zanic M. Rescuing microtubules from the brink of catastrophe: CLASPs lead the way. Curr Opin Cell Biol 2019; 56:94-101. [PMID: 30453184 PMCID: PMC6370552 DOI: 10.1016/j.ceb.2018.10.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 10/12/2018] [Accepted: 10/31/2018] [Indexed: 01/11/2023]
Abstract
Microtubules are cytoskeletal polymers that dynamically remodel to perform essential cellular functions. Individual microtubules alternate between phases of growth and shrinkage via sudden transitions called catastrophe and rescue, driven by losing and regaining a stabilizing cap at the dynamic microtubule end. New in vitro studies now show that a conserved family of CLASP proteins specifically modulate microtubule catastrophe and rescue transitions. Further, recent cryo-electron microscopy approaches have elucidated new structural features of the stabilizing cap. Together, these new advances provide a clearer view on the complexity of the microtubule end and its regulation.
Collapse
Affiliation(s)
- E J Lawrence
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, United States
| | - M Zanic
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, United States; Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37240, United States; Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, United States.
| |
Collapse
|
27
|
Zwetsloot AJ, Tut G, Straube A. Measuring microtubule dynamics. Essays Biochem 2018; 62:725-735. [PMID: 30287587 PMCID: PMC6281472 DOI: 10.1042/ebc20180035] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 08/31/2018] [Accepted: 09/04/2018] [Indexed: 12/31/2022]
Abstract
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.
Collapse
Affiliation(s)
- Alexander James Zwetsloot
- Centre for Mechanochemical Cell Biology, University of Warwick, Coventry, CV4 7AL, U.K
- MRC Doctoral Training Partnership, University of Warwick, Coventry, CV4 7AL, U.K
| | - Gokhan Tut
- Centre for Mechanochemical Cell Biology, University of Warwick, Coventry, CV4 7AL, U.K
- MRC Doctoral Training Partnership, University of Warwick, Coventry, CV4 7AL, U.K
| | - Anne Straube
- Centre for Mechanochemical Cell Biology, University of Warwick, Coventry, CV4 7AL, U.K.
- Division of Biomedical Sciences, Warwick Medical School, Coventry, CV4 7AL, U.K
| |
Collapse
|
28
|
Wu YT, Adnan A. Damage and Failure of Axonal Microtubule under Extreme High Strain Rate: An In-Silico Molecular Dynamics Study. Sci Rep 2018; 8:12260. [PMID: 30115936 PMCID: PMC6095851 DOI: 10.1038/s41598-018-29804-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 06/06/2018] [Indexed: 02/01/2023] Open
Abstract
As a major cytoskeleton element of the axon, the breaking of microtubules (MTs) has been considered as a major cause of the axon degeneration. High strain rate loading is considered as one of the key factors in microtubule breaking. Due to the small size of microtubule, the real-time behavior of microtubule breaking is hard to capture. This study employs fully-atomistic molecular dynamics (MD) simulation to determine the failure modes of microtubule under different loadings conditions such as, unidirectional stretching, bending and hydrostatic expansion. For each loading conditions, MT is subjected to extreme high strain rate (108-109 s-1) loading. We argue that such level of high strain rate may be realized during cavitation bubble implosion. For each loading type, we have determined the critical energy for MT rupture. The associated rupture mechanisms are also discussed. We observed that the stretching has the lowest energy barrier to break the MT at the nanosecond time scale. Moreover, the breakage between the dimers starts at ~16% of total strain when stretched, which is much smaller compared to the reported strain-at-failure (50%) for lower strain rate loading. It suggests that MT fails at a significantly smaller strain states when loaded at higher strain rates.
Collapse
Affiliation(s)
- Yuan-Ting Wu
- Department of Mechanical and Aerospace Engineering, The University of Texas at Arlington, Arlington, TX, 76019, USA
| | - Ashfaq Adnan
- Department of Mechanical and Aerospace Engineering, The University of Texas at Arlington, Arlington, TX, 76019, USA.
| |
Collapse
|
29
|
Lawrence EJ, Arpag G, Norris SR, Zanic M. Human CLASP2 specifically regulates microtubule catastrophe and rescue. Mol Biol Cell 2018. [PMID: 29540526 PMCID: PMC5935067 DOI: 10.1091/mbc.e18-01-0016] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Cytoplasmic linker-associated proteins (CLASPs) are microtubule-associated proteins essential for microtubule regulation in many cellular processes. However, the molecular mechanisms underlying CLASP activity are not understood. Here, we use purified protein components and total internal reflection fluorescence microscopy to investigate the effects of human CLASP2 on microtubule dynamics in vitro. We demonstrate that CLASP2 suppresses microtubule catastrophe and promotes rescue without affecting the rates of microtubule growth or shrinkage. Strikingly, when CLASP2 is combined with EB1, a known binding partner, the effects on microtubule dynamics are strongly enhanced. We show that synergy between CLASP2 and EB1 is dependent on a direct interaction, since a truncated EB1 protein that lacks the CLASP2-binding domain does not enhance CLASP2 activity. Further, we find that EB1 targets CLASP2 to microtubules and increases the dwell time of CLASP2 at microtubule tips. Although the temporally averaged microtubule growth rates are unaffected by CLASP2, we find that microtubules grown with CLASP2 display greater variability in growth rates. Our results provide insight into the regulation of microtubule dynamics by CLASP proteins and highlight the importance of the functional interplay between regulatory proteins at dynamic microtubule ends.
Collapse
Affiliation(s)
- Elizabeth J Lawrence
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240
| | - Göker Arpag
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240
| | - Stephen R Norris
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240
| | - Marija Zanic
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240.,Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37240.,Department of Biochemistry, Vanderbilt University, Nashville, TN 37240
| |
Collapse
|
30
|
Aher A, Akhmanova A. Tipping microtubule dynamics, one protofilament at a time. Curr Opin Cell Biol 2018; 50:86-93. [PMID: 29573640 DOI: 10.1016/j.ceb.2018.02.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Revised: 02/19/2018] [Accepted: 02/28/2018] [Indexed: 01/10/2023]
Abstract
Microtubules are polymeric tubes that switch between phases of growth and shortening, and this property is essential to drive key cellular processes. Microtubules are composed of protofilaments formed by longitudinally arranged tubulin dimers. Microtubule dynamics can be affected by structural perturbations at the plus end, such as end tapering, and targeting only a small subset of protofilaments can alter the dynamics of the whole microtubule. Microtubule lattice plasticity, including compaction along the longitudinal axis upon GTP hydrolysis and tubulin dimer loss and reinsertion along microtubule shafts can also affect microtubule dynamics or mechanics. Microtubule behaviour can be fine-tuned by post-translational modifications and tubulin isotypes, which together support the diversity of microtubule functions within and across various cell types or cell cycle and developmental stages.
Collapse
Affiliation(s)
- Amol Aher
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Anna Akhmanova
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
| |
Collapse
|
31
|
Xu J, Zhou H, Yu Q, Manners I, Winnik MA. Competitive Self-Assembly Kinetics as a Route To Control the Morphology of Core-Crystalline Cylindrical Micelles. J Am Chem Soc 2018; 140:2619-2628. [DOI: 10.1021/jacs.7b12444] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jiangping Xu
- Department
of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 1H6, Canada
| | - Hang Zhou
- Department
of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 1H6, Canada
| | - Qing Yu
- Department
of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 1H6, Canada
| | - Ian Manners
- School
of Chemistry, University of Bristol, Bristol, BS8 1TS, U.K
| | - Mitchell A. Winnik
- Department
of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 1H6, Canada
| |
Collapse
|
32
|
Barsegov V, Ross JL, Dima RI. Dynamics of microtubules: highlights of recent computational and experimental investigations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:433003. [PMID: 28812545 DOI: 10.1088/1361-648x/aa8670] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Microtubules are found in most eukaryotic cells, with homologs in eubacteria and archea, and they have functional roles in mitosis, cell motility, intracellular transport, and the maintenance of cell shape. Numerous efforts have been expended over the last two decades to characterize the interactions between microtubules and the wide variety of microtubule associated proteins that control their dynamic behavior in cells resulting in microtubules being assembled and disassembled where and when they are required by the cell. We present the main findings regarding microtubule polymerization and depolymerization and review recent work about the molecular motors that modulate microtubule dynamics by inducing either microtubule depolymerization or severing. We also discuss the main experimental and computational approaches used to quantify the thermodynamics and mechanics of microtubule filaments.
Collapse
Affiliation(s)
- Valeri Barsegov
- Department of Chemistry, University of Massachusetts, Lowell, MA 01854, United States of America
| | | | | |
Collapse
|
33
|
Ayoub AT, Staelens M, Prunotto A, Deriu MA, Danani A, Klobukowski M, Tuszynski JA. Explaining the Microtubule Energy Balance: Contributions Due to Dipole Moments, Charges, van der Waals and Solvation Energy. Int J Mol Sci 2017; 18:ijms18102042. [PMID: 28937650 PMCID: PMC5666724 DOI: 10.3390/ijms18102042] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 09/12/2017] [Accepted: 09/13/2017] [Indexed: 12/14/2022] Open
Abstract
Microtubules are the main components of mitotic spindles, and are the pillars of the cellular cytoskeleton. They perform most of their cellular functions by virtue of their unique dynamic instability processes which alternate between polymerization and depolymerization phases. This in turn is driven by a precise balance between attraction and repulsion forces between the constituents of microtubules (MTs)—tubulin dimers. Therefore, it is critically important to know what contributions result in a balance of the interaction energy among tubulin dimers that make up microtubules and what interactions may tip this balance toward or away from a stable polymerized state of tubulin. In this paper, we calculate the dipole–dipole interaction energy between tubulin dimers in a microtubule as part of the various contributions to the energy balance. We also compare the remaining contributions to the interaction energies between tubulin dimers and establish a balance between stabilizing and destabilizing components, including the van der Waals, electrostatic, and solvent-accessible surface area energies. The energy balance shows that the GTP-capped tip of the seam at the plus end of microtubules is stabilized only by −9 kcal/mol, which can be completely reversed by the hydrolysis of a single GTP molecule, which releases +14 kcal/mol and destabilizes the seam by an excess of +5 kcal/mol. This triggers the breakdown of microtubules and initiates a disassembly phase which is aptly called a catastrophe.
Collapse
Affiliation(s)
- Ahmed Taha Ayoub
- Medicinal Chemistry Department, Heliopolis University, Cairo-Belbeis Desert Rd, El-Nahda, El-Salam, Cairo Governorate 11777, Egypt.
| | - Michael Staelens
- Department of Physics, University of Alberta, Edmonton, AB T6G 2E1, Canada.
| | - Alessio Prunotto
- Istituto Dalle Molle di Studi sull'Intelligenza Artificiale (IDSIA), Scuola Universitaria Professionale Della Svizzera Italiana (SUPSI), Università Della Svizzera Italiana (USI), Centro Galleria 2, Manno CH-6928, Switzerland.
| | - Marco A Deriu
- Istituto Dalle Molle di Studi sull'Intelligenza Artificiale (IDSIA), Scuola Universitaria Professionale Della Svizzera Italiana (SUPSI), Università Della Svizzera Italiana (USI), Centro Galleria 2, Manno CH-6928, Switzerland.
| | - Andrea Danani
- Istituto Dalle Molle di Studi sull'Intelligenza Artificiale (IDSIA), Scuola Universitaria Professionale Della Svizzera Italiana (SUPSI), Università Della Svizzera Italiana (USI), Centro Galleria 2, Manno CH-6928, Switzerland.
| | - Mariusz Klobukowski
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada.
| | | |
Collapse
|
34
|
Vleugel M, Kok M, Dogterom M. Understanding force-generating microtubule systems through in vitro reconstitution. Cell Adh Migr 2017; 10:475-494. [PMID: 27715396 PMCID: PMC5079405 DOI: 10.1080/19336918.2016.1241923] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Microtubules switch between growing and shrinking states, a feature known as dynamic instability. The biochemical parameters underlying dynamic instability are modulated by a wide variety of microtubule-associated proteins that enable the strict control of microtubule dynamics in cells. The forces generated by controlled growth and shrinkage of microtubules drive a large range of processes, including organelle positioning, mitotic spindle assembly, and chromosome segregation. In the past decade, our understanding of microtubule dynamics and microtubule force generation has progressed significantly. Here, we review the microtubule-intrinsic process of dynamic instability, the effect of external factors on this process, and how the resulting forces act on various biological systems. Recently, reconstitution-based approaches have strongly benefited from extensive biochemical and biophysical characterization of individual components that are involved in regulating or transmitting microtubule-driven forces. We will focus on the current state of reconstituting increasingly complex biological systems and provide new directions for future developments.
Collapse
Affiliation(s)
- Mathijs Vleugel
- a Department of Bionanoscience , Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft Institute of Technology , Delft , The Netherlands
| | - Maurits Kok
- a Department of Bionanoscience , Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft Institute of Technology , Delft , The Netherlands
| | - Marileen Dogterom
- a Department of Bionanoscience , Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft Institute of Technology , Delft , The Netherlands
| |
Collapse
|
35
|
Castle BT, McCubbin S, Prahl LS, Bernens JN, Sept D, Odde DJ. Mechanisms of kinetic stabilization by the drugs paclitaxel and vinblastine. Mol Biol Cell 2017; 28:1238-1257. [PMID: 28298489 PMCID: PMC5415019 DOI: 10.1091/mbc.e16-08-0567] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 02/21/2017] [Accepted: 02/28/2017] [Indexed: 12/20/2022] Open
Abstract
Chemotherapeutic agents that target microtubule dynamics promote a universal phenotype of kinetic stabilization. Integrated computational modeling and fluorescence microscopy identify the fundamental kinetic and thermodynamic mechanisms that result in kinetic stabilization, specifically by the drugs paclitaxel and vinblastine. Microtubule-targeting agents (MTAs), widely used as biological probes and chemotherapeutic drugs, bind directly to tubulin subunits and “kinetically stabilize” microtubules, suppressing the characteristic self-assembly process of dynamic instability. However, the molecular-level mechanisms of kinetic stabilization are unclear, and the fundamental thermodynamic and kinetic requirements for dynamic instability and its elimination by MTAs have yet to be defined. Here we integrate a computational model for microtubule assembly with nanometer-scale fluorescence microscopy measurements to identify the kinetic and thermodynamic basis of kinetic stabilization by the MTAs paclitaxel, an assembly promoter, and vinblastine, a disassembly promoter. We identify two distinct modes of kinetic stabilization in live cells, one that truly suppresses on-off kinetics, characteristic of vinblastine, and the other a “pseudo” kinetic stabilization, characteristic of paclitaxel, that nearly eliminates the energy difference between the GTP- and GDP-tubulin thermodynamic states. By either mechanism, the main effect of both MTAs is to effectively stabilize the microtubule against disassembly in the absence of a robust GTP cap.
Collapse
Affiliation(s)
- Brian T Castle
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455
| | - Seth McCubbin
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Louis S Prahl
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455
| | - Jordan N Bernens
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455
| | - David Sept
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - David J Odde
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455
| |
Collapse
|
36
|
Steady-state EB cap size fluctuations are determined by stochastic microtubule growth and maturation. Proc Natl Acad Sci U S A 2017; 114:3427-3432. [PMID: 28280102 DOI: 10.1073/pnas.1620274114] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Growing microtubules are protected from depolymerization by the presence of a GTP or GDP/Pi cap. End-binding proteins of the EB1 family bind to the stabilizing cap, allowing monitoring of its size in real time. The cap size has been shown to correlate with instantaneous microtubule stability. Here we have quantitatively characterized the properties of cap size fluctuations during steady-state growth and have developed a theory predicting their timescale and amplitude from the kinetics of microtubule growth and cap maturation. In contrast to growth speed fluctuations, cap size fluctuations show a characteristic timescale, which is defined by the lifetime of the cap sites. Growth fluctuations affect the amplitude of cap size fluctuations; however, cap size does not affect growth speed, indicating that microtubules are far from instability during most of their time of growth. Our theory provides the basis for a quantitative understanding of microtubule stability fluctuations during steady-state growth.
Collapse
|
37
|
Zakharov P, Gudimchuk N, Voevodin V, Tikhonravov A, Ataullakhanov FI, Grishchuk EL. Molecular and Mechanical Causes of Microtubule Catastrophe and Aging. Biophys J 2016; 109:2574-2591. [PMID: 26682815 DOI: 10.1016/j.bpj.2015.10.048] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 09/11/2015] [Accepted: 10/05/2015] [Indexed: 10/22/2022] Open
Abstract
Tubulin polymers, microtubules, can switch abruptly from the assembly to shortening. These infrequent transitions, termed "catastrophes", affect numerous cellular processes but the underlying mechanisms are elusive. We approached this complex stochastic system using advanced coarse-grained molecular dynamics modeling of tubulin-tubulin interactions. Unlike in previous simplified models of dynamic microtubules, the catastrophes in this model arise owing to fluctuations in the composition and conformation of a growing microtubule tip, most notably in the number of protofilament curls. In our model, dynamic evolution of the stochastic microtubule tip configurations over a long timescale, known as the system's "aging", gives rise to the nonexponential distribution of microtubule lifetimes, consistent with experiment. We show that aging takes place in the absence of visible changes in the microtubule wall or tip, as this complex molecular-mechanical system evolves slowly and asymptotically toward the steady-state level of the catastrophe-promoting configurations. This new, to our knowledge, theoretical basis will assist detailed mechanistic investigations of the mechanisms of action of different microtubule-binding proteins and drugs, thereby enabling accurate control over the microtubule dynamics to treat various pathologies.
Collapse
Affiliation(s)
- Pavel Zakharov
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Nikita Gudimchuk
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, Moscow, Russia; Moscow State University, Moscow, Russia; Federal Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | | | | | - Fazoil I Ataullakhanov
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, Moscow, Russia; Moscow State University, Moscow, Russia; Federal Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Ekaterina L Grishchuk
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
| |
Collapse
|
38
|
Abstract
α-Synuclein is a presynaptic protein associated to Parkinson’s disease, which is unstructured when free in the cytoplasm and adopts α helical conformation when bound to vesicles. After decades of intense studies, α-Synuclein physiology is still difficult to clear up due to its interaction with multiple partners and its involvement in a pletora of neuronal functions. Here, we looked at the remarkably neglected interplay between α-Synuclein and microtubules, which potentially impacts on synaptic functionality. In order to identify the mechanisms underlying these actions, we investigated the interaction between purified α-Synuclein and tubulin. We demonstrated that α-Synuclein binds to microtubules and tubulin α2β2 tetramer; the latter interaction inducing the formation of helical segment(s) in the α-Synuclein polypeptide. This structural change seems to enable α-Synuclein to promote microtubule nucleation and to enhance microtubule growth rate and catastrophe frequency, both in vitro and in cell. We also showed that Parkinson’s disease-linked α-Synuclein variants do not undergo tubulin-induced folding and cause tubulin aggregation rather than polymerization. Our data enable us to propose α-Synuclein as a novel, foldable, microtubule-dynamase, which influences microtubule organisation through its binding to tubulin and its regulating effects on microtubule nucleation and dynamics.
Collapse
|
39
|
Bowne-Anderson H, Hibbel A, Howard J. Regulation of Microtubule Growth and Catastrophe: Unifying Theory and Experiment. Trends Cell Biol 2016; 25:769-779. [PMID: 26616192 DOI: 10.1016/j.tcb.2015.08.009] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 08/27/2015] [Accepted: 08/27/2015] [Indexed: 10/22/2022]
Abstract
Recent studies have found that microtubule-associated proteins (MAPs) can regulate the dynamical properties of microtubules in unexpected ways. For most MAPs, there is an inverse relationship between their effects on the speed of growth and the frequency of catastrophe, the conversion of a growing microtubule to a shrinking one. Such a negative correlation is predicted by the standard GTP-cap model, which posits that catastrophe is due to loss of a stabilizing cap of GTP-tubulin at the end of a growing microtubule. However, many other MAPs, notably Kinesin-4 and combinations of EB1 with XMAP215, contradict this general rule. In this review, we show that a more nuanced, but still simple, GTP-cap model, can account for the diverse regulatory activities of MAPs.
Collapse
Affiliation(s)
| | - Anneke Hibbel
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany; ETH Zurich, Institute for Biochemistry, HPM E8.1, Otto-Stern-Weg 3, 8093 Zurich, Switzerland
| | | |
Collapse
|
40
|
Duellberg C, Cade NI, Surrey T. Microtubule aging probed by microfluidics-assisted tubulin washout. Mol Biol Cell 2016; 27:3563-3573. [PMID: 27489342 PMCID: PMC5221588 DOI: 10.1091/mbc.e16-07-0548] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 07/28/2016] [Indexed: 11/24/2022] Open
Abstract
Microtubule aging—the decrease of stability with age—is an interesting but mechanistically not understood property of microtubules. It constrains possible mechanisms of catastrophe induction and is believed to be crucial for length regulation. New in vitro experiments and model fits provide insight into the origin of microtubule aging. Microtubules switch stochastically between phases of growth and shrinkage. The molecular mechanism responsible for the end of a growth phase, an event called catastrophe, is still not understood. The probability for a catastrophe to occur increases with microtubule age, putting constraints on the possible molecular mechanism of catastrophe induction. Here we used microfluidics-assisted fast tubulin washout experiments to induce microtubule depolymerization in a controlled manner at different times after the start of growth. We found that aging can also be observed in this assay, providing valuable new constraints against which theoretical models of catastrophe induction can be tested. We found that the data can be quantitatively well explained by a simple kinetic threshold model that assumes an age-dependent broadening of the protective cap at the microtubule end as a result of an evolving tapered end structure; this leads to a decrease of the cap density and its stability. This analysis suggests an intuitive picture of the role of morphological changes of the protective cap for the age dependence of microtubule stability.
Collapse
Affiliation(s)
- Christian Duellberg
- Lincoln's Inn Fields Laboratory, Francis Crick Institute, London WC2A 3LY, United Kingdom
| | - Nicholas Ian Cade
- Lincoln's Inn Fields Laboratory, Francis Crick Institute, London WC2A 3LY, United Kingdom
| | - Thomas Surrey
- Lincoln's Inn Fields Laboratory, Francis Crick Institute, London WC2A 3LY, United Kingdom
| |
Collapse
|
41
|
Brouhard GJ. Dynamic instability 30 years later: complexities in microtubule growth and catastrophe. Mol Biol Cell 2016; 26:1207-10. [PMID: 25823928 PMCID: PMC4454169 DOI: 10.1091/mbc.e13-10-0594] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
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.
Collapse
Affiliation(s)
- Gary J Brouhard
- Department of Biology, McGill University, Montréal, QC H3A 1B1, Canada
| |
Collapse
|
42
|
Rymut SM, Ivy T, Corey DA, Cotton CU, Burgess JD, Kelley TJ. Role of Exchange Protein Activated by cAMP 1 in Regulating Rates of Microtubule Formation in Cystic Fibrosis Epithelial Cells. Am J Respir Cell Mol Biol 2016; 53:853-62. [PMID: 25955407 DOI: 10.1165/rcmb.2014-0462oc] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The regulation of microtubule dynamics in cystic fibrosis (CF) epithelial cells and the consequences of reduced rates of microtubule polymerization on downstream CF cellular events, such as cholesterol accumulation, a marker of impaired intracellular transport, are explored here. It is identified that microtubules in both CF cell models and in primary CF nasal epithelial cells repolymerize at a slower rate compared with respective controls. Previous studies suggest a role for cAMP in modulating organelle transport in CF cells, implicating a role for exchange protein activated by cAMP (EPAC) 1, a regulator of microtubule elongation, as a potential mechanism. EPAC1 activity is reduced in CF cell models and in Cftr(-/-) mouse lung compared with respective non-CF controls. Stimulation of EPAC1 activity with the selective EPAC1 agonist, 8-cpt-2-O-Me-cAMP, stimulates microtubule repolymerization to wild-type rates in CF cells. EPAC1 activation also alleviates cholesterol accumulation in CF cells, suggesting a direct link between microtubule regulation and intracellular transport. To verify the relationship between transport and microtubule regulation, expression of the protein, tubulin polymerization-promoting protein, was knocked down in non-CF human tracheal (9/HTEo(-)) cells to mimic the microtubule dysregulation in CF cells. Transduced cells with short hairpin RNA targeting tubulin polymerization-promoting protein exhibit CF-like perinuclear cholesterol accumulation and other cellular manifestations of CF cells, thus supporting a role for microtubule regulation as a mechanism linking CFTR function to downstream cellular manifestation.
Collapse
Affiliation(s)
| | | | | | | | - James D Burgess
- 3 Chemistry, Case Western Reserve University, Cleveland, Ohio
| | - Thomas J Kelley
- Departments of 1 Pharmacology.,2 Pediatrics, and.,3 Chemistry, Case Western Reserve University, Cleveland, Ohio
| |
Collapse
|
43
|
Duellberg C, Cade NI, Holmes D, Surrey T. The size of the EB cap determines instantaneous microtubule stability. eLife 2016; 5. [PMID: 27050486 PMCID: PMC4829430 DOI: 10.7554/elife.13470] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 02/23/2016] [Indexed: 12/24/2022] Open
Abstract
The function of microtubules relies on their ability to switch between phases of growth and shrinkage. A nucleotide-dependent stabilising cap at microtubule ends is thought to be lost before this switch can occur; however, the nature and size of this protective cap are unknown. Using a microfluidics-assisted multi-colour TIRF microscopy assay with close-to-nm and sub-second precision, we measured the sizes of the stabilizing cap of individual microtubules. We find that the protective caps are formed by the extended binding regions of EB proteins. Cap lengths vary considerably and longer caps are more stable. Nevertheless, the trigger of instability lies in a short region at the end of the cap, as a quantitative model of cap stability demonstrates. Our study establishes the spatial and kinetic characteristics of the protective cap and provides an insight into the molecular mechanism by which its loss leads to the switch from microtubule growth to shrinkage. DOI:http://dx.doi.org/10.7554/eLife.13470.001 Much like the skeleton supports the human body, a structure called the cytoskeleton provides support and structure to cells. Part of this cytoskeleton is made up of small tubes called microtubules that – unlike bones – can shrink and grow very quickly. This allows the cell to change shape, move and split into two new cells. Exactly how the microtubules switch between growing and shrinking was not clear. One suggestion is that a protective cap at the end of microtubule allows it to keep growing and prevents it from shrinking. However, the nature and size of this cap have been debated. Now, Duellberg et al. have measured the caps of microtubules with high precision by combining the techniques of microfluidics, TIRF microscopy and recently developed image analysis tools. This revealed that the cap sizes change, with longer caps being more stable. In addition, proteins called end-binding proteins can destabilize the cap by binding to it. This allows microtubules to switch from a growing to a shrinking state more often. Future work could now investigate how changes in cap length cause the microtubules to switch from growing to shrinking. It also remains to be seen whether other proteins also influence the cap to control this switching behaviour. DOI:http://dx.doi.org/10.7554/eLife.13470.002
Collapse
Affiliation(s)
- Christian Duellberg
- Lincoln's Inn Fields Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Nicholas I Cade
- Lincoln's Inn Fields Laboratory, The Francis Crick Institute, London, United Kingdom
| | - David Holmes
- London Centre of Nanotechnology, London, United Kingdom
| | - Thomas Surrey
- Lincoln's Inn Fields Laboratory, The Francis Crick Institute, London, United Kingdom
| |
Collapse
|
44
|
Geyer EA, Majumdar S, Rice LM. May I check your cap? eLife 2016; 5:e15570. [PMID: 27050617 PMCID: PMC4829414 DOI: 10.7554/elife.15570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 04/01/2016] [Indexed: 11/21/2022] Open
Abstract
Modernizing a classic technique to study microtubules has revealed that the stability of a microtubule is related to its growth rate.
Collapse
Affiliation(s)
- Elisabeth A Geyer
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, United States
| | - Shreoshi Majumdar
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, United States
| | - Luke M Rice
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, United States
| |
Collapse
|
45
|
Lacroix B, Ryan J, Dumont J, Maddox PS, Maddox AS. Identification of microtubule growth deceleration and its regulation by conserved and novel proteins. Mol Biol Cell 2016; 27:1479-87. [PMID: 26985017 PMCID: PMC4850035 DOI: 10.1091/mbc.e16-01-0056] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 03/09/2016] [Indexed: 11/29/2022] Open
Abstract
Live imaging of microtubule dynamics in Caenorhabditis elegans muscle cells reveals a novel microtubule behavior characterized by an abrupt change in growth rate, named “microtubule growth deceleration.” The conserved protein ZYG-9TOGp and two novel ORFs, cylc-1 and cylc-2, are involved in the regulation of this novel microtubule behavior. Microtubules (MTs) are cytoskeletal polymers that participate in diverse cellular functions, including cell division, intracellular trafficking, and templating of cilia and flagella. MTs undergo dynamic instability, alternating between growth and shortening via catastrophe and rescue events. The rates and frequencies of MT dynamic parameters appear to be characteristic for a given cell type. We recently reported that all MT dynamic parameters vary throughout differentiation of a smooth muscle cell type in intact Caenorhabditis elegans. Here we describe local differences in MT dynamics and a novel MT behavior: an abrupt change in growth rate (deceleration) of single MTs occurring in the cell periphery of these cells. MT deceleration occurs where there is a decrease in local soluble tubulin concentration at the cell periphery. This local regulation of tubulin concentration and MT deceleration are dependent on two novel homologues of human cylicin. These novel ORFs, which we name cylc-1 and -2, share sequence homology with stathmins and encode small, very basic proteins containing several KKD/E repeats. The TOG domain–containing protein ZYG-9TOGp is responsible for the faster polymerization rate within the cell body. Thus we have defined two contributors to the molecular regulation for this novel MT behavior.
Collapse
Affiliation(s)
- Benjamin Lacroix
- Institut Jacques Monod, CNRS, UMR 7592, University Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France
| | - Joël Ryan
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC H3C 3J7, Canada
| | - Julien Dumont
- Institut Jacques Monod, CNRS, UMR 7592, University Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France
| | - Paul S Maddox
- Institut Jacques Monod, CNRS, UMR 7592, University Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France
| | - Amy S Maddox
- Institut Jacques Monod, CNRS, UMR 7592, University Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France
| |
Collapse
|
46
|
Abstract
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.
Collapse
Affiliation(s)
- Ryoma Ohi
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Marija Zanic
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee, USA
| |
Collapse
|
47
|
Reid TA, Schuster BM, Mann BJ, Balchand SK, Plooster M, McClellan M, Coombes CE, Wadsworth P, Gardner MK. Suppression of microtubule assembly kinetics by the mitotic protein TPX2. J Cell Sci 2016; 129:1319-28. [PMID: 26869224 DOI: 10.1242/jcs.178806] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Accepted: 02/05/2016] [Indexed: 01/01/2023] Open
Abstract
TPX2 is a widely conserved microtubule-associated protein that is required for mitotic spindle formation and function. Previous studies have demonstrated that TPX2 is required for the nucleation of microtubules around chromosomes; however, the molecular mechanism by which TPX2 promotes microtubule nucleation remains a mystery. In this study, we found that TPX2 acts to suppress tubulin subunit off-rates during microtubule assembly and disassembly, thus allowing for the support of unprecedentedly slow rates of plus-end microtubule growth, and also leading to a dramatically reduced microtubule shortening rate. These changes in microtubule dynamics can be explained in computational simulations by a moderate increase in tubulin-tubulin bond strength upon TPX2 association with the microtubule lattice, which in turn acts to reduce the departure rate of tubulin subunits from the microtubule ends. Thus, the direct suppression of tubulin subunit off-rates by TPX2 during microtubule growth and shortening could provide a molecular mechanism to explain the nucleation of new microtubules in the presence of TPX2.
Collapse
Affiliation(s)
- Taylor A Reid
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Breanna M Schuster
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Barbara J Mann
- Department of Biology, University of Massachusetts, Amherst, MA 01003, USA
| | | | - Melissa Plooster
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Mark McClellan
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Courtney E Coombes
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Pat Wadsworth
- Department of Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - Melissa K Gardner
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| |
Collapse
|
48
|
Lopez BJ, Valentine MT. The +TIP coordinating protein EB1 is highly dynamic and diffusive on microtubules, sensitive to GTP analog, ionic strength, and EB1 concentration. Cytoskeleton (Hoboken) 2016; 73:23-34. [PMID: 26663881 DOI: 10.1002/cm.21267] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 12/04/2015] [Accepted: 12/04/2015] [Indexed: 01/06/2023]
Abstract
Using single-molecule fluorescence microscopy, we investigated the dynamics of dye-labeled EB1, a +TIP microtubule binding protein. To promote EB1 binding along the entire microtubule length, we formed microtubules using the nonhydrolyzable GTP analogs GMPCPP and GTPγS. Through precise tracking of the motions of individual dye-labeled proteins, we found EB1 to be highly dynamic and continuously diffusive while bound to a microtubule, with a diffusion coefficient and characteristic binding lifetime that were sensitive to both the choice of GTP analog and the buffer ionic strength. Using fluorescence-based equilibrium binding measurements, we found EB1 binding to be cooperative and also sensitive to GTP analog and ionic strength. By tracking the motion of a small number of individually-labeled EB1 proteins within a bath of unlabeled EB1 proteins, we determined the effects of increasing the total EB1 concentration on binding and dynamics. We found that the diffusion coefficient decreased with increasing EB1 concentration, which may be due at least in part, to the cooperativity of EB1 binding. Our results may have important consequences for the assembly and organization of the growing microtubule plus-end.
Collapse
Affiliation(s)
- Benjamin J Lopez
- Department of Mechanical Engineering and the Neuroscience Research Institute, University of California, Santa Barbara, California
| | - Megan T Valentine
- Department of Mechanical Engineering and the Neuroscience Research Institute, University of California, Santa Barbara, California
| |
Collapse
|
49
|
Abstract
Microtubule dynamic instability, the process by which individual microtubules switch between phases of growth and shrinkage, is essential for establishing the architecture of cellular microtubule structures, such as the mitotic spindle. This switching process is regulated by a complex network of microtubule-associated proteins (MAPs), which modulate different aspects of microtubule dynamic behavior. To elucidate the effects of MAPs and their molecular mechanisms of action, in vitro reconstitution approaches with purified components are used. Here, I present methods for measuring individual and combined effects of MAPs on microtubule dynamics, using purified protein components and total-internal-reflection fluorescence (TIRF) microscopy. Particular focus is given to the experimental design, proper parameterization, and data analysis.
Collapse
|
50
|
Aging Gracefully: A New Model of Microtubule Growth and Catastrophe. Biophys J 2015; 109:2449-2451. [PMID: 26682802 DOI: 10.1016/j.bpj.2015.10.049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 10/23/2015] [Accepted: 10/26/2015] [Indexed: 01/22/2023] Open
|