1
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Wijeratne SS, Subramanian R. Real-Time Visualization of Microtubule and Protofilament-Scale Dynamics in Multi-Microtubule Arrays by Atomic Force Microscopy. Curr Protoc 2023; 3:e779. [PMID: 37227098 PMCID: PMC10439732 DOI: 10.1002/cpz1.779] [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] [Indexed: 05/26/2023]
Abstract
Microtubules, polymers of α, β-tubulin heterodimers, are organized into multi-microtubule arrays for diverse cellular functions. The dynamic properties of microtubule arrays govern their structural and functional properties. While numerous insights into the biophysical mechanisms underlying microtubule organization have been gleaned from in vitro reconstitution studies, the assays are largely restricted to visualization of single or pairs of microtubules. Thus, the dynamic processes underlying the remodeling of multi-microtubule arrays remain poorly understood. Recent work shows that Atomic Force Microscopy (AFM) enables the visualization of nanoscale dynamics within multi-microtubule 2D arrays. In this assay, electrostatic interactions permit the non-specific adsorption of microtubule arrays to mica. AFM imaging in tapping mode, a gentle method of imaging, allows the visualization of microtubules and protofilaments without sample damage. The height information captured by AFM imaging enables the tracking of structural changes in microtubules and protofilaments within multi-microtubule arrays over time. The experimental data from the method described here reveal previously unseen modes of nanoscale dynamics in microtubule bundles formed by the microtubule-crosslinking protein PRC1 in the presence of the depolymerase MCAK. The observations demonstrate the potential of AFM imaging in transforming our understanding of the fundamental cellular process by which multi-microtubule arrays are dynamically assembled and disassembled. © 2023 Wiley Periodicals LLC. Basic Protocol: Sample preparation and real-time visualization of microtubule arrays by atomic force microscopy Alternate Protocol: Protocol for coating surface with poly-L-lysine and immobilizing microtubules.
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Affiliation(s)
- Sithara S. Wijeratne
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114
- Department of Genetics, Harvard Medical School, Boston, MA 02115
| | - Radhika Subramanian
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114
- Department of Genetics, Harvard Medical School, Boston, MA 02115
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2
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Quintanilla MA, Patel H, Wu H, Sochacki KA, Akamatsu M, Rotty JD, Korobova F, Bear JE, Taraska JW, Oakes PW, Beach JR. Local Monomer Levels and Established Filaments Potentiate Non-Muscle Myosin 2 Assembly. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.26.538303. [PMID: 37162845 PMCID: PMC10168331 DOI: 10.1101/2023.04.26.538303] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The ability to dynamically assemble contractile networks is required throughout cell physiology, yet the biophysical mechanisms regulating non-muscle myosin 2 filament assembly in living cells are lacking. Here we use a suite of dynamic, quantitative imaging approaches to identify deterministic factors that drive myosin filament appearance and amplification. We find that actin dynamics regulate myosin assembly, but that the actin architecture plays a minimal direct role. Instead, remodeling of actin networks modulates the local myosin monomer levels and facilitates assembly through myosin:myosin driven interactions. Using optogenetically controlled myosin, we demonstrate that locally concentrating myosin is sufficient to both form filaments and jump-start filament amplification and partitioning. By counting myosin monomers within filaments, we demonstrate a myosin-facilitated assembly process that establishes sub-resolution filament stacks prior to partitioning into clusters that feed higher-order networks. Together these findings establish the biophysical mechanisms regulating the assembly of non-muscle contractile structures that are ubiquitous throughout cell biology.
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Affiliation(s)
- Melissa A Quintanilla
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Hiral Patel
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Huini Wu
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Kem A Sochacki
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD, USA
| | | | - Jeremy D Rotty
- Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, MD
| | - Farida Korobova
- Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - James E Bear
- Department of Cell Biology and Physiology, University of North Carolina-Chapel Hill, Chapel Hill, NC
| | - Justin W Taraska
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD, USA
| | - Patrick W Oakes
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Jordan R Beach
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
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3
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van der Beek J, de Heus C, Liv N, Klumperman J. Quantitative correlative microscopy reveals the ultrastructural distribution of endogenous endosomal proteins. J Cell Biol 2022; 221:212877. [PMID: 34817533 PMCID: PMC8624803 DOI: 10.1083/jcb.202106044] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 10/22/2021] [Accepted: 11/01/2021] [Indexed: 02/07/2023] Open
Abstract
The key endosomal regulators Rab5, EEA1, and APPL1 are frequently applied in fluorescence microscopy to mark early endosomes, whereas Rab7 is used as a marker for late endosomes and lysosomes. However, endogenous levels of these proteins localize poorly in immuno-EM, and systematic studies on their native ultrastructural distributions are lacking. To address this gap, we here present a quantitative, on-section correlative light and electron microscopy (CLEM) approach. Using the sensitivity of fluorescence microscopy, we label hundreds of organelles that are subsequently visualized by EM and classified by ultrastructure. We show that Rab5 predominantly marks small, endocytic vesicles and early endosomes. EEA1 colocalizes with Rab5 on early endosomes, but unexpectedly also labels Rab5-negative late endosomes, which are positive for PI(3)P but lack Rab7. APPL1 is restricted to small Rab5-positive, tubulo-vesicular profiles. Rab7 primarily labels late endosomes and lysosomes. These data increase our understanding of the structural-functional organization of the endosomal system and introduce quantitative CLEM as a sensitive alternative for immuno-EM.
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Affiliation(s)
- Jan van der Beek
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Cecilia de Heus
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Nalan Liv
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
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4
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Christensen JR, Kendrick AA, Truong JB, Aguilar-Maldonado A, Adani V, Dzieciatkowska M, Reck-Peterson SL. Cytoplasmic dynein-1 cargo diversity is mediated by the combinatorial assembly of FTS-Hook-FHIP complexes. eLife 2021; 10:74538. [PMID: 34882091 PMCID: PMC8730729 DOI: 10.7554/elife.74538] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 12/08/2021] [Indexed: 11/13/2022] Open
Abstract
In eukaryotic cells, intracellular components are organized by the microtubule motors cytoplasmic dynein-1 (dynein) and kinesins, which are linked to cargos via adaptor proteins. While ~40 kinesins transport cargo toward the plus end of microtubules, a single dynein moves cargo in the opposite direction. How dynein transports a wide variety of cargos remains an open question. The FTS–Hook–FHIP (‘FHF’) cargo adaptor complex links dynein to cargo in humans and fungi. As human cells have three Hooks and four FHIP proteins, we hypothesized that the combinatorial assembly of different Hook and FHIP proteins could underlie dynein cargo diversity. Using proteomic approaches, we determine the protein ‘interactome’ of each FHIP protein. Live-cell imaging and biochemical approaches show that different FHF complexes associate with distinct motile cargos. These complexes also move with dynein and its cofactor dynactin in single-molecule in vitro reconstitution assays. Complexes composed of FTS, FHIP1B, and Hook1/Hook3 colocalize with Rab5-tagged early endosomes via a direct interaction between FHIP1B and GTP-bound Rab5. In contrast, complexes composed of FTS, FHIP2A, and Hook2 colocalize with Rab1A-tagged ER-to-Golgi cargos and FHIP2A is involved in the motility of Rab1A tubules. Our findings suggest that combinatorial assembly of different FTS–Hook–FHIP complexes is one mechanism dynein uses to achieve cargo specificity.
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Affiliation(s)
- Jenna R Christensen
- Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, United States
| | - Agnieszka A Kendrick
- Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, United States
| | - Joey B Truong
- Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, United States
| | | | - Vinit Adani
- Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, United States
| | - Monika Dzieciatkowska
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver, Aurora, United States
| | - Samara L Reck-Peterson
- Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, United States
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5
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Zhang G, Dong Z, Gimple RC, Wolin A, Wu Q, Qiu Z, Wood LM, Shen JZ, Jiang L, Zhao L, Lv D, Prager BC, Kim LJY, Wang X, Zhang L, Anderson RL, Moore JK, Bao S, Keller TH, Lin G, Kang C, Hamerlik P, Zhao R, Ford HL, Rich JN. Targeting EYA2 tyrosine phosphatase activity in glioblastoma stem cells induces mitotic catastrophe. J Exp Med 2021; 218:212685. [PMID: 34617969 PMCID: PMC8504185 DOI: 10.1084/jem.20202669] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 07/11/2021] [Accepted: 08/19/2021] [Indexed: 12/13/2022] Open
Abstract
Glioblastoma ranks among the most lethal of primary brain malignancies, with glioblastoma stem cells (GSCs) at the apex of tumor cellular hierarchies. Here, to discover novel therapeutic GSC targets, we interrogated gene expression profiles from GSCs, differentiated glioblastoma cells (DGCs), and neural stem cells (NSCs), revealing EYA2 as preferentially expressed by GSCs. Targeting EYA2 impaired GSC maintenance and induced cell cycle arrest, apoptosis, and loss of self-renewal. EYA2 displayed novel localization to centrosomes in GSCs, and EYA2 tyrosine (Tyr) phosphatase activity was essential for proper mitotic spindle assembly and survival of GSCs. Inhibition of the EYA2 Tyr phosphatase activity, via genetic or pharmacological means, mimicked EYA2 loss in GSCs in vitro and extended the survival of tumor-bearing mice. Supporting the clinical relevance of these findings, EYA2 portends poor patient prognosis in glioblastoma. Collectively, our data indicate that EYA2 phosphatase function plays selective critical roles in the growth and survival of GSCs, potentially offering a high therapeutic index for EYA2 inhibitors.
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Affiliation(s)
- Guoxin Zhang
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Zhen Dong
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Ryan C Gimple
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA.,Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Arthur Wolin
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Qiulian Wu
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Zhixin Qiu
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Lisa M Wood
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO
| | - Jia Z Shen
- Tumor Initiation and Maintenance Program, National Cancer Institute-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA
| | - Li Jiang
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Linjie Zhao
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Deguan Lv
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Briana C Prager
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA.,Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Leo J Y Kim
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA.,Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Xiuxing Wang
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Lingdi Zhang
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Ryan L Anderson
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO
| | - Shideng Bao
- Department of Stem Cell Biology and Regenerative Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH
| | - Thomas H Keller
- Experimental Drug Development Centre, Agency for Science, Technology and Research, Singapore
| | - Grace Lin
- Experimental Drug Development Centre, Agency for Science, Technology and Research, Singapore
| | - Congbao Kang
- Experimental Drug Development Centre, Agency for Science, Technology and Research, Singapore
| | - Petra Hamerlik
- Danish Cancer Society Research Center, Copenhagen, Denmark.,Department of Drug Design and Pharmacology, Copenhagen University, Copenhagen, Denmark
| | - Rui Zhao
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Heide L Ford
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Jeremy N Rich
- Division of Regenerative Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA.,University of Pittsburgh Medical Center, Hillman Cancer Center, Pittsburgh, PA.,Department of Neurology, University of Pittsburgh, Pittsburgh, PA
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6
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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: 31] [Impact Index Per Article: 7.8] [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.
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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
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7
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Comelles J, Fernández-Majada V, Berlanga-Navarro N, Acevedo V, Paszkowska K, Martínez E. Microfabrication of poly(acrylamide) hydrogels with independently controlled topography and stiffness. Biofabrication 2020; 12:025023. [PMID: 32050182 DOI: 10.1088/1758-5090/ab7552] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The stiffness and topography of a cell's extracellular matrix (ECM) are physical cues that play a key role in regulating processes that determine cellular fate and function. While substrate stiffness can dictate cell differentiation lineage, migration, and self-organization, topographical features can change the cell's differentiation profile or migration ability. Although both physical cues are present and intrinsic to the native tissues in vivo, in vitro studies have been hampered by the lack of technological set-ups that would be compatible with cell culture and characterization. In vitro studies therefore either focused on screening stiffness effects in cells cultured on flat substrates or on determining topography effects in cells cultured onto hard materials. Here, we present a reliable, microfabrication method to obtain well defined topographical structures of micrometer size (5-10 μm) on soft polyacrylamide hydrogels with tunable mechanical stiffness (3-145 kPa) that closely mimic the in vivo situation. Topographically microstructured polyacrylamide hydrogels are polymerized by capillary force lithography using flexible materials as molds. The topographical microstructures are resistant to swelling, can be conformally functionalized by ECM proteins and sustain the growth of cell lines (fibroblasts and myoblasts) and primary cells (mouse intestinal epithelial cells). Our method can independently control stiffness and topography, which allows to individually assess the contribution of each physical cue to cell response or to explore potential synergistic effects. We anticipate that our fabrication method will be of great utility in tissue engineering and biophysics, especially for applications where the use of complex in vivo-like environments is of paramount importance.
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Affiliation(s)
- Jordi Comelles
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), c/Baldiri Reixac 10-12, E-08028, Barcelona, Spain
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8
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Kendrick AA, Dickey AM, Redwine WB, Tran PT, Vaites LP, Dzieciatkowska M, Harper JW, Reck-Peterson SL. Hook3 is a scaffold for the opposite-polarity microtubule-based motors cytoplasmic dynein-1 and KIF1C. J Cell Biol 2019; 218:2982-3001. [PMID: 31320392 PMCID: PMC6719453 DOI: 10.1083/jcb.201812170] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Revised: 05/06/2019] [Accepted: 06/21/2019] [Indexed: 01/06/2023] Open
Abstract
The unidirectional and opposite-polarity microtubule-based motors, dynein and kinesin, drive long-distance intracellular cargo transport. Cellular observations suggest that opposite-polarity motors may be coupled. We recently identified an interaction between the cytoplasmic dynein-1 activating adaptor Hook3 and the kinesin-3 KIF1C. Here, using in vitro reconstitutions with purified components, we show that KIF1C and dynein/dynactin can exist in a complex scaffolded by Hook3. Full-length Hook3 binds to and activates dynein/dynactin motility. Hook3 also binds to a short region in the "tail" of KIF1C, but unlike dynein/dynactin, this interaction does not activate KIF1C. Hook3 scaffolding allows dynein to transport KIF1C toward the microtubule minus end, and KIF1C to transport dynein toward the microtubule plus end. In cells, KIF1C can recruit Hook3 to the cell periphery, although the cellular role of the complex containing both motors remains unknown. We propose that Hook3's ability to scaffold dynein/dynactin and KIF1C may regulate bidirectional motility, promote motor recycling, or sequester the pool of available dynein/dynactin activating adaptors.
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Affiliation(s)
- Agnieszka A Kendrick
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
| | - Andrea M Dickey
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
| | - William B Redwine
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
- Department of Cell Biology, Harvard Medical School, Boston, MA
| | - Phuoc Tien Tran
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
| | | | - Monika Dzieciatkowska
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver, Aurora, CO
| | - J Wade Harper
- Department of Cell Biology, Harvard Medical School, Boston, MA
| | - Samara L Reck-Peterson
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA
- Howard Hughes Medical Institute, Chevy Chase, MD
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9
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Fees CP, Moore JK. A unified model for microtubule rescue. Mol Biol Cell 2019; 30:753-765. [PMID: 30672721 PMCID: PMC6589779 DOI: 10.1091/mbc.e18-08-0541] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 12/06/2018] [Accepted: 01/17/2019] [Indexed: 11/23/2022] Open
Abstract
How microtubules transition from depolymerization to polymerization, known as rescue, is poorly understood. Here we examine two models for rescue: 1) an "end-driven" model in which the depolymerizing end stochastically switches to a stable state; and 2) a "lattice-driven" model in which rescue sites are integrated into the microtubule before depolymerization. We test these models using a combination of computational simulations and in vitro experiments with purified tubulin. Our findings support the "lattice-driven" model by identifying repeated rescue sites in microtubules. In addition, we discover an important role for divalent cations in determining the frequency and location of rescue sites. We use "wash-in" experiments to show that divalent cations inhibit rescue during depolymerization, but not during polymerization. We propose a unified model in which rescues are driven by embedded rescue sites in microtubules, but the activity of these sites is influenced by changes in the depolymerizing ends.
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Affiliation(s)
- Colby P. Fees
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045
| | - Jeffrey K. Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045
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10
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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: 40] [Impact Index Per Article: 6.7] [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.
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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
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11
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Geyer EA, Miller MP, Brautigam CA, Biggins S, Rice LM. Design principles of a microtubule polymerase. eLife 2018; 7:34574. [PMID: 29897335 PMCID: PMC5999394 DOI: 10.7554/elife.34574] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 05/10/2018] [Indexed: 11/16/2022] Open
Abstract
Stu2/XMAP215 microtubule polymerases use multiple tubulin-binding TOG domains and a lattice-binding basic region to processively promote faster elongation. How the domain composition and organization of these proteins dictate polymerase activity, end localization, and processivity is unknown. We show that polymerase activity does not require different kinds of TOGs, nor are there strict requirements for how the TOGs are linked. We identify an unexpected antagonism between the tubulin-binding TOGs and the lattice-binding basic region: lattice binding by the basic region is weak when at least two TOGs engage tubulins, strong when TOGs are empty. End-localization of Stu2 requires unpolymerized tubulin, at least two TOGs, and polymerase competence. We propose a ‘ratcheting’ model for processivity: transfer of tubulin from TOGs to the lattice activates the basic region, retaining the polymerase at the end for subsequent rounds of tubulin binding and incorporation. These results clarify design principles of the polymerase.
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Affiliation(s)
- Elisabeth A Geyer
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, United States
| | - Matthew P Miller
- Howard Hughes Medical Institute, Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Chad A Brautigam
- Departments of Biophysics and Microbiology, UT Southwestern Medical Center, Dallas, United States
| | - Sue Biggins
- Howard Hughes Medical Institute, Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Luke M Rice
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, United States
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12
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Driver JW, Geyer EA, Bailey ME, Rice LM, Asbury CL. Direct measurement of conformational strain energy in protofilaments curling outward from disassembling microtubule tips. eLife 2017. [PMID: 28628007 PMCID: PMC5515574 DOI: 10.7554/elife.28433] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Disassembling microtubules can generate movement independently of motor enzymes, especially at kinetochores where they drive chromosome motility. A popular explanation is the 'conformational wave' model, in which protofilaments pull on the kinetochore as they curl outward from a disassembling tip. But whether protofilaments can work efficiently via this spring-like mechanism has been unclear. By modifying a previous assay to use recombinant tubulin and feedback-controlled laser trapping, we directly demonstrate the spring-like elasticity of curling protofilaments. Measuring their mechanical work output suggests they carry ~25% of the energy of GTP hydrolysis as bending strain, enabling them to drive movement with efficiency similar to conventional motors. Surprisingly, a β-tubulin mutant that dramatically slows disassembly has no effect on work output, indicating an uncoupling of disassembly speed from protofilament strain. These results show the wave mechanism can make a major contribution to kinetochore motility and establish a direct approach for measuring tubulin mechano-chemistry.
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Affiliation(s)
- Jonathan W Driver
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Elisabeth A Geyer
- Department of Biophysics, UT Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, UT Southwestern Medical Center, Dallas, United States
| | - Megan E Bailey
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Luke M Rice
- Department of Biophysics, UT Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, UT Southwestern Medical Center, Dallas, United States
| | - Charles L Asbury
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
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13
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Mooney P, Sulerud T, Pelletier J, Dilsaver M, Tomschik M, Geisler C, Gatlin JC. Tau-based fluorescent protein fusions to visualize microtubules. Cytoskeleton (Hoboken) 2017; 74:221-232. [PMID: 28407416 PMCID: PMC5592782 DOI: 10.1002/cm.21368] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 04/03/2017] [Accepted: 04/10/2017] [Indexed: 01/10/2023]
Abstract
The ability to visualize cytoskeletal proteins and their dynamics in living cells has been critically important in advancing our understanding of numerous cellular processes, including actin- and microtubule (MT)-dependent phenomena such as cell motility, cell division, and mitosis. Here, we describe a novel set of fluorescent protein (FP) fusions designed specifically to visualize MTs in living systems using fluorescence microscopy. Each fusion contains a FP module linked in frame to a modified phospho-deficient version of the MT-binding domain of Tau (mTMBD). We found that expressed and purified constructs containing a single mTMBD decorated Xenopus egg extract spindles more homogenously than similar constructs containing the MT-binding domain of Ensconsin, suggesting that the binding affinity of mTMBD is minimally affected by localized signaling gradients generated during mitosis. Furthermore, MT dynamics were not grossly perturbed by the presence of Tau-based FP fusions. Interestingly, the addition of a second mTMBD to the opposite terminus of our construct caused dramatic changes to the spatial localization of probes within spindles. These results support the use of Tau-based FP fusions as minimally perturbing tools to accurately visualize MTs in living systems.
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Affiliation(s)
- Paul Mooney
- Department of Molecular Biology, University of Wyoming, Laramie, WY,
82071, USA
- Molecular & Cellular Life Sciences Program, University of
Wyoming, Laramie, WY, 82071, USA
- Cell Organization and Division Group, Marine Biological
Laboratories, Woods Hole, MA, 02543, USA
| | - Taylor Sulerud
- Department of Molecular Biology, University of Wyoming, Laramie, WY,
82071, USA
- Molecular & Cellular Life Sciences Program, University of
Wyoming, Laramie, WY, 82071, USA
- Cell Organization and Division Group, Marine Biological
Laboratories, Woods Hole, MA, 02543, USA
| | - James Pelletier
- Cell Organization and Division Group, Marine Biological
Laboratories, Woods Hole, MA, 02543, USA
- Department of Systems Biology, Harvard Medical School, Boston, MA,
02115, USA
| | - Matthew Dilsaver
- Department of Molecular Biology, University of Wyoming, Laramie, WY,
82071, USA
| | - Miroslav Tomschik
- Department of Molecular Biology, University of Wyoming, Laramie, WY,
82071, USA
| | | | - Jesse C. Gatlin
- Department of Molecular Biology, University of Wyoming, Laramie, WY,
82071, USA
- Molecular & Cellular Life Sciences Program, University of
Wyoming, Laramie, WY, 82071, USA
- Cell Organization and Division Group, Marine Biological
Laboratories, Woods Hole, MA, 02543, USA
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14
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Wang J, Schneider IC. Myosin phosphorylation on stress fibers predicts contact guidance behavior across diverse breast cancer cells. Biomaterials 2017; 120:81-93. [PMID: 28039755 PMCID: PMC5291342 DOI: 10.1016/j.biomaterials.2016.11.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 11/22/2016] [Accepted: 11/24/2016] [Indexed: 11/24/2022]
Abstract
During cancer progression the extracellular matrix is remodeled, forming aligned collagen fibers that proceed radially from the tumor, resulting in invasion. We have recently shown that different invasive breast cancer cells respond to epitaxially grown, aligned collagen fibrils differently. This article develops insight into why these cells differ in their contact guidance fidelity. Small changes in contractility or adhesion dramatically alter directional persistence on aligned collagen fibrils, while migration speed remains constant. The directionality of highly contractile and adhesive MDA-MB-231 cells can be diminished by inhibiting Rho kinase or β1 integrin binding. Inversely, the directionality of less contractile and adhesive MTLn3 cells can be enhanced by activating contractility or integrins. Subtle, but quantifiable alterations in myosin II regulatory light chain phosphorylation on stress fibers explain the tuning of contact guidance fidelity, separate from migration per se indicating that the contractile and adhesive state of the cell in combination with collagen organization in the tumor microenvironment determine the efficiency of migration. Understanding how distinct cells respond to contact guidance cues will not only illuminate mechanisms for cancer invasion, but will also allow for the design of environments to separate specific subpopulations of cells from patient-derived tissues by leveraging differences in responses to directional migration cues.
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Affiliation(s)
- Juan Wang
- Department of Chemical and Biological Engineering, Iowa State University, USA
| | - Ian C Schneider
- Department of Chemical and Biological Engineering, Iowa State University, USA; Department of Genetics, Development and Cell Biology, Iowa State University, USA.
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15
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Braun A, Caesar NM, Dang K, Myers KA. High-resolution Time-lapse Imaging and Automated Analysis of Microtubule Dynamics in Living Human Umbilical Vein Endothelial Cells. J Vis Exp 2016. [PMID: 27584860 PMCID: PMC5091855 DOI: 10.3791/54265] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The physiological process by which new vasculature forms from existing vasculature requires specific signaling events that trigger morphological changes within individual endothelial cells (ECs). These processes are critical for homeostatic maintenance such as wound healing, and are also crucial in promoting tumor growth and metastasis. EC morphology is defined by the organization of the cytoskeleton, a tightly regulated system of actin and microtubule (MT) dynamics that is known to control EC branching, polarity and directional migration, essential components of angiogenesis. To study MT dynamics, we used high-resolution fluorescence microscopy coupled with computational image analysis of fluorescently-labeled MT plus-ends to investigate MT growth dynamics and the regulation of EC branching morphology and directional migration. Time-lapse imaging of living Human Umbilical Vein Endothelial Cells (HUVECs) was performed following transfection with fluorescently-labeled MT End Binding protein 3 (EB3) and Mitotic Centromere Associated Kinesin (MCAK)-specific cDNA constructs to evaluate effects on MT dynamics. PlusTipTracker software was used to track EB3-labeled MT plus ends in order to measure MT growth speeds and MT growth lifetimes in time-lapse images. This methodology allows for the study of MT dynamics and the identification of how localized regulation of MT dynamics within sub-cellular regions contributes to the angiogenic processes of EC branching and migration.
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Affiliation(s)
- Alexander Braun
- Department of Biological Sciences, University of the Sciences in Philadelphia
| | - Nicole M Caesar
- Department of Biological Sciences, University of the Sciences in Philadelphia
| | - Kyvan Dang
- Department of Biological Sciences, University of the Sciences in Philadelphia
| | - Kenneth A Myers
- Department of Biological Sciences, University of the Sciences in Philadelphia;
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16
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Piedra FA, Kim T, Garza ES, Geyer EA, Burns A, Ye X, Rice LM. GDP-to-GTP exchange on the microtubule end can contribute to the frequency of catastrophe. Mol Biol Cell 2016; 27:3515-3525. [PMID: 27146111 PMCID: PMC5221584 DOI: 10.1091/mbc.e16-03-0199] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Accepted: 04/26/2016] [Indexed: 11/11/2022] Open
Abstract
Microtubules are dynamic polymers of αβ-tubulin that have essential roles in chromosome segregation and organization of the cytoplasm. Catastrophe-the switch from growing to shrinking-occurs when a microtubule loses its stabilizing GTP cap. Recent evidence indicates that the nucleotide on the microtubule end controls how tightly an incoming subunit will be bound (trans-acting GTP), but most current models do not incorporate this information. We implemented trans-acting GTP into a computational model for microtubule dynamics. In simulations, growing microtubules often exposed terminal GDP-bound subunits without undergoing catastrophe. Transient GDP exposure on the growing plus end slowed elongation by reducing the number of favorable binding sites on the microtubule end. Slower elongation led to erosion of the GTP cap and an increase in the frequency of catastrophe. Allowing GDP-to-GTP exchange on terminal subunits in simulations mitigated these effects. Using mutant αβ-tubulin or modified GTP, we showed experimentally that a more readily exchangeable nucleotide led to less frequent catastrophe. Current models for microtubule dynamics do not account for GDP-to-GTP exchange on the growing microtubule end, so our findings provide a new way of thinking about the molecular events that initiate catastrophe.
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Affiliation(s)
- Felipe-Andrés Piedra
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390
| | - Tae Kim
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390
| | - Emily S Garza
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390
| | - Elisabeth A Geyer
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390
| | - Alexander Burns
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390
| | - Xuecheng Ye
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390
| | - Luke M Rice
- Departments of Biophysics and Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390
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17
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Geyer EA, Burns A, Lalonde BA, Ye X, Piedra FA, Huffaker TC, Rice LM. A mutation uncouples the tubulin conformational and GTPase cycles, revealing allosteric control of microtubule dynamics. eLife 2015; 4:e10113. [PMID: 26439009 PMCID: PMC4728127 DOI: 10.7554/elife.10113] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 10/06/2015] [Indexed: 11/18/2022] Open
Abstract
Microtubule dynamic instability depends on the GTPase activity of the polymerizing αβ-tubulin subunits, which cycle through at least three distinct conformations as they move into and out of microtubules. How this conformational cycle contributes to microtubule growing, shrinking, and switching remains unknown. Here, we report that a buried mutation in αβ-tubulin yields microtubules with dramatically reduced shrinking rate and catastrophe frequency. The mutation causes these effects by suppressing a conformational change that normally occurs in response to GTP hydrolysis in the lattice, without detectably changing the conformation of unpolymerized αβ-tubulin. Thus, the mutation weakens the coupling between the conformational and GTPase cycles of αβ-tubulin. By showing that the mutation predominantly affects post-GTPase conformational and dynamic properties of microtubules, our data reveal that the strength of the allosteric response to GDP in the lattice dictates the frequency of catastrophe and the severity of rapid shrinking. DOI:http://dx.doi.org/10.7554/eLife.10113.001 Protein filaments called microtubules help move cargo around inside cells. Chromosomes, which contain the cell’s genetic blueprints, are the microtubule’s most precious cargo. Before a cell divides, microtubules grow from the ends of the dividing cell towards the middle, where they attach to the chromosomes that are lined up along the centerline. Then the microtubules shrink and drag the chromosomes back to the opposite ends of the cell. This allows each of the new cells to get one copy of each chromosome. When the microtubules are growing, a molecule called guanosine triphosphate (or GTP) is attached to the proteins at the end of the filament. This acts like a cap and protects the microtubule from shrinking. Later a chemical reaction converts GTP into GDP (short for guanosine diphosphate). Without the protective GTP cap, the microtubule quickly shrinks. At the same time, the proteins that make up the microtubule also change shape. In the microtubule, the proteins adopt a straight shape when GTP is attached. The proteins favor a different shape in the microtubule when GDP is attached. However, it is unclear if or how these shape changes contribute to how a microtubule grows or shrinks. Geyer et al. now show how this shape shifting can influence microtubule shrinking, by first identifying a mutation in yeast microtubule proteins that cause the proteins to remain straight even when GDP is attached. Next, powerful microscopes were used to make time-lapse videos of the mutated microtubules. This allowed Geyer et al. to observe how the mutated microtubules behaved and compare this to the behavior of normal microtubules. The experiments revealed that the mutated microtubules were less likely to begin shrinking than typical microtubules. The mutated microtubules also shrunk more slowly. These findings indicate that the shape changes control the speed of shrinking and frequency of entering the shrinking phase. These new details about the control of microtubule growth and shrinkage may help scientists studying how cell division happens in both healthy and cancerous cells. DOI:http://dx.doi.org/10.7554/eLife.10113.002
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Affiliation(s)
- Elisabeth A Geyer
- Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
| | - Alexander Burns
- Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
| | - Beth A Lalonde
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Xuecheng Ye
- Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
| | - Felipe-Andres Piedra
- Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
| | - Tim C Huffaker
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Luke M Rice
- Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
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18
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Microtubule-associated proteins control the kinetics of microtubule nucleation. Nat Cell Biol 2015; 17:907-16. [PMID: 26098575 DOI: 10.1038/ncb3188] [Citation(s) in RCA: 141] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 05/14/2015] [Indexed: 02/07/2023]
Abstract
Microtubules are born and reborn continuously, even during quiescence. These polymers are nucleated from templates, namely γ-tubulin ring complexes (γ-TuRCs) and severed microtubule ends. Using single-molecule biophysics, we show that nucleation from γ-TuRCs, axonemes and seed microtubules requires tubulin concentrations that lie well above the critical concentration. We measured considerable time lags between the arrival of tubulin and the onset of steady-state elongation. Microtubule-associated proteins (MAPs) alter these time lags. Catastrophe factors (MCAK and EB1) inhibited nucleation, whereas a polymerase (XMAP215) and an anti-catastrophe factor (TPX2) promoted nucleation. We observed similar phenomena in cells. We conclude that GTP hydrolysis inhibits microtubule nucleation by destabilizing the nascent plus ends required for persistent elongation. Our results explain how MAPs establish the spatial and temporal profile of microtubule nucleation.
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19
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Gokhin DS, Nowak RB, Khoory JA, Piedra ADL, Ghiran IC, Fowler VM. Dynamic actin filaments control the mechanical behavior of the human red blood cell membrane. Mol Biol Cell 2015; 26:1699-710. [PMID: 25717184 PMCID: PMC4436781 DOI: 10.1091/mbc.e14-12-1583] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 02/17/2015] [Indexed: 11/11/2022] Open
Abstract
The short actin filaments in the spectrin-actin membrane skeleton of human red blood cells (RBCs) are capable of dynamic subunit exchange and mobility. Actin dynamics in RBCs regulates the biomechanical properties of the RBC membrane. Short, uniform-length actin filaments function as structural nodes in the spectrin-actin membrane skeleton to optimize the biomechanical properties of red blood cells (RBCs). Despite the widespread assumption that RBC actin filaments are not dynamic (i.e., do not exchange subunits with G-actin in the cytosol), this assumption has never been rigorously tested. Here we show that a subpopulation of human RBC actin filaments is indeed dynamic, based on rhodamine-actin incorporation into filaments in resealed ghosts and fluorescence recovery after photobleaching (FRAP) analysis of actin filament mobility in intact RBCs (∼25–30% of total filaments). Cytochalasin-D inhibition of barbed-end exchange reduces rhodamine-actin incorporation and partially attenuates FRAP recovery, indicating functional interaction between actin subunit turnover at the single-filament level and mobility at the membrane-skeleton level. Moreover, perturbation of RBC actin filament assembly/disassembly with latrunculin-A or jasplakinolide induces an approximately twofold increase or ∼60% decrease, respectively, in soluble actin, resulting in altered membrane deformability, as determined by alterations in RBC transit time in a microfluidic channel assay, as well as by abnormalities in spontaneous membrane oscillations (flickering). These experiments identify a heretofore-unrecognized but functionally important subpopulation of RBC actin filaments, whose properties and architecture directly control the biomechanical properties of the RBC membrane.
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Affiliation(s)
- David S Gokhin
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Roberta B Nowak
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Joseph A Khoory
- Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02115
| | | | - Ionita C Ghiran
- Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02115
| | - Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037
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20
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Hazel J, Krutkramelis K, Mooney P, Tomschik M, Gerow K, Oakey J, Gatlin JC. Changes in cytoplasmic volume are sufficient to drive spindle scaling. Science 2013; 342:853-6. [PMID: 24233723 PMCID: PMC4004590 DOI: 10.1126/science.1243110] [Citation(s) in RCA: 160] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The mitotic spindle must function in cell types that vary greatly in size, and its dimensions scale with the rapid, reductive cell divisions that accompany early stages of development. The mechanism responsible for this scaling is unclear, because uncoupling cell size from a developmental or cellular context has proven experimentally challenging. We combined microfluidic technology with Xenopus egg extracts to characterize spindle assembly within discrete, geometrically defined volumes of cytoplasm. Reductions in cytoplasmic volume, rather than developmental cues or changes in cell shape, were sufficient to recapitulate spindle scaling observed in Xenopus embryos. Thus, mechanisms extrinsic to the spindle, specifically a limiting pool of cytoplasmic component(s), play a major role in determining spindle size.
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Affiliation(s)
- James Hazel
- Dept. of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
| | - Kaspars Krutkramelis
- Dept. of Chemical and Petroleum Engineering, University of Wyoming, Laramie, WY 82071, USA
| | - Paul Mooney
- Dept. of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
| | - Miroslav Tomschik
- Dept. of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
| | - Ken Gerow
- Dept. of Statistics, University of Wyoming, Laramie, WY 82071, USA
| | - John Oakey
- Dept. of Chemical and Petroleum Engineering, University of Wyoming, Laramie, WY 82071, USA
| | - J. C. Gatlin
- Dept. of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
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21
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Erent M, Drummond DR, Cross RA. S. pombe kinesins-8 promote both nucleation and catastrophe of microtubules. PLoS One 2012; 7:e30738. [PMID: 22363481 PMCID: PMC3282699 DOI: 10.1371/journal.pone.0030738] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Accepted: 12/23/2011] [Indexed: 11/18/2022] Open
Abstract
The kinesins-8 were originally thought to be microtubule depolymerases, but are now emerging as more versatile catalysts of microtubule dynamics. We show here that S. pombe Klp5-436 and Klp6-440 are non-processive plus-end-directed motors whose in vitro velocities on S. pombe microtubules at 7 and 23 nm s(-1) are too slow to keep pace with the growing tips of dynamic interphase microtubules in living S. pombe. In vitro, Klp5 and 6 dimers exhibit a hitherto-undescribed combination of strong enhancement of microtubule nucleation with no effect on growth rate or catastrophe frequency. By contrast in vivo, both Klp5 and Klp6 promote microtubule catastrophe at cell ends whilst Klp6 also increases the number of interphase microtubule arrays (IMAs). Our data support a model in which Klp5/6 bind tightly to free tubulin heterodimers, strongly promoting the nucleation of new microtubules, and then continue to land as a tubulin-motor complex on the tips of growing microtubules, with the motors then dissociating after a few seconds residence on the lattice. In vivo, we predict that only at cell ends, when growing microtubule tips become lodged and their growth slows down, will Klp5/6 motor activity succeed in tracking growing microtubule tips. This mechanism would allow Klp5/6 to detect the arrival of microtubule tips at cells ends and to amplify the intrinsic tendency for microtubules to catastrophise in compression at cell ends. Our evidence identifies Klp5 and 6 as spatial regulators of microtubule dynamics that enhance both microtubule nucleation at the cell centre and microtubule catastrophe at the cell ends.
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Affiliation(s)
- Muriel Erent
- Centre for Mechanochemical Cell Biology, Warwick Medical School, The University of Warwick, Coventry, United Kingdom
| | - Douglas R. Drummond
- Centre for Mechanochemical Cell Biology, Warwick Medical School, The University of Warwick, Coventry, United Kingdom
| | - Robert A. Cross
- Centre for Mechanochemical Cell Biology, Warwick Medical School, The University of Warwick, Coventry, United Kingdom
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22
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Gibbs-Flournoy EA, Bromberg PA, Hofer TPJ, Samet JM, Zucker RM. Darkfield-confocal microscopy detection of nanoscale particle internalization by human lung cells. Part Fibre Toxicol 2011; 8:2. [PMID: 21247485 PMCID: PMC3033333 DOI: 10.1186/1743-8977-8-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 01/19/2011] [Indexed: 11/10/2022] Open
Abstract
Background Concerns over the health effects of nanomaterials in the environment have created a need for microscopy methods capable of examining the biological interactions of nanoparticles (NP). Unfortunately, NP are beyond the diffraction limit of resolution for conventional light microscopy (~200 nm). Fluorescence and electron microscopy techniques commonly used to examine NP interactions with biological substrates have drawbacks that limit their usefulness in toxicological investigation of NP. EM is labor intensive and slow, while fluorescence carries the risk of photobleaching the sample and has size resolution limits. In addition, many relevant particles lack intrinsic fluorescence and therefore can not be detected in this manner. To surmount these limitations, we evaluated the potential of a novel combination of darkfield and confocal laser scanning microscopy (DF-CLSM) for the efficient 3D detection of NP in human lung cells. The DF-CLSM approach utilizes the contrast enhancements of darkfield microscopy to detect objects below the diffraction limit of 200 nm based on their light scattering properties and interfaces it with the power of confocal microscopy to resolve objects in the z-plane. Results Validation of the DF-CLSM method using fluorescent polystyrene beads demonstrated spatial colocalization of particle fluorescence (Confocal) and scattered transmitted light (Darkfield) along the X, Y, and Z axes. DF-CLSM imaging was able to detect and provide reasonable spatial locations of 27 nm TiO2 particles in relation to the stained nuclei of exposed BEAS 2B cells. Statistical analysis of particle proximity to cellular nuclei determined a significant difference between 5 min and 2 hr particle exposures suggesting a time-dependant internalization process. Conclusions DF-CLSM microscopy is an alternative to current conventional light and electron microscopy methods that does not rely on particle fluorescence or contrast in electron density. DF-CLSM is especially well suited to the task of establishing the spatial localization of nanoparticles within cells, a critical topic in nanotoxicology. This technique has advantages to 2D darkfield microscopy as it visualizes nanoparticles in 3D using confocal microscopy. Use of this technique should aid toxicological studies related to observation of NP interactions with biological endpoints at cellular and subcellular levels.
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Affiliation(s)
- Eugene A Gibbs-Flournoy
- Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Chapel Hill, NC, USA
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23
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Hsp 70/Hsp 90 organizing protein as a nitrosylation target in cystic fibrosis therapy. Proc Natl Acad Sci U S A 2010; 107:11393-8. [PMID: 20534503 DOI: 10.1073/pnas.0909128107] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The endogenous signaling molecule S-nitrosoglutathione (GSNO) and other S-nitrosylating agents can cause full maturation of the abnormal gene product DeltaF508 cystic fibrosis (CF) transmembrane conductance regulator (CFTR). However, the molecular mechanism of action is not known. Here we show that Hsp70/Hsp90 organizing protein (Hop) is a critical target of GSNO, and its S-nitrosylation results in DeltaF508 CFTR maturation and cell surface expression. S-nitrosylation by GSNO inhibited the association of Hop with CFTR in the endoplasmic reticulum. This effect was necessary and sufficient to mediate GSNO-induced cell-surface expression of DeltaF508 CFTR. Hop knockdown using siRNA recapitulated the effect of GSNO on DeltaF508 CFTR maturation and expression. Moreover, GSNO acted additively with decreased temperature, which promoted mutant CFTR maturation through a Hop-independent mechanism. We conclude that GSNO corrects DeltaF508 CFTR trafficking by inhibiting Hop expression, and that combination therapies--using differing mechanisms of action--may have additive benefits in treating CF.
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24
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Bee C, Moshnikova A, Mellor CD, Molloy JE, Koryakina Y, Stieglitz B, Khokhlatchev A, Herrmann C. Growth and tumor suppressor NORE1A is a regulatory node between Ras signaling and microtubule nucleation. J Biol Chem 2010; 285:16258-66. [PMID: 20339001 PMCID: PMC2871493 DOI: 10.1074/jbc.m109.081562] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 03/23/2010] [Indexed: 12/31/2022] Open
Abstract
NORE1A is a Ras-binding protein that belongs to a group of tumor suppressors known as the Ras association domain family. Their growth- and tumor-suppressive function is assumed to be dependent on association with the microtubule cytoskeleton. However, a detailed understanding of this interplay is still missing. Here, we show that NORE1A directly interacts with tubulin and is capable of nucleating microtubules. Strikingly, the ability to stimulate nucleation is regulated in a dual specific way either via phosphorylation of NORE1A within the Ras-binding domain by Aurora A kinase or via binding to activated Ras. We also demonstrate that NORE1A mediates a negative effect of activated Ras on microtubule nucleation. On the basis of our results, we propose a novel regulatory network composed of the tumor suppressor NORE1A, the mitotic kinase Aurora A, the small GTPase Ras, and the microtubule cytoskeleton.
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Affiliation(s)
- Christine Bee
- From the Department of Chemistry, Physical Chemistry 1, Ruhr-University Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | | | - Christopher D. Mellor
- the Medical Research Council National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
| | - Justin E. Molloy
- the Medical Research Council National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
| | - Yulia Koryakina
- Microbiology, University of Virginia Health Science Center, Charlottesville, Virginia 22908, and
| | - Benjamin Stieglitz
- the Medical Research Council National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
| | | | - Christian Herrmann
- From the Department of Chemistry, Physical Chemistry 1, Ruhr-University Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
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Skommer J, McGuinness D, Wlodkowic D. Self-adhesive microculture system for extended live cell imaging. Biotech Histochem 2010; 86:174-80. [DOI: 10.3109/10520290903547075] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Silicone-urethane adhesive for improved coverslip mounting and leak-free preparation of living cell observation chambers. Biotechniques 2009; 46:225-7. [DOI: 10.2144/000113071] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Using a combination of silicone and urethane resin, we established a rapid technique for preparing living specimens for microscopy. One major advantage of this technique is that the coverslip is rigidly attached and does not detach during handling. As a result, it is possible to continuously observe living cells at high magnification and resolution using an oil immersion objective. Another advantage is that living cells are quickly confined to the space between the glass slide and coverslip, protecting them from environmental changes, which can cause serious effects on cell function and morphology. Moreover, high-resolution observations of real-time responses of cells are possible, using the combination of the mounting technique and a simple flow chamber.
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