1
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Cassidy A, Farmer V, Arpağ G, Zanic M. The GTP-tubulin cap is not the determinant of microtubule end stability in cells. Mol Biol Cell 2024; 35:br19. [PMID: 39259768 DOI: 10.1091/mbc.e24-07-0307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/13/2024] Open
Abstract
Microtubules are dynamic cytoskeletal polymers essential for cell division, motility, and intracellular transport. Microtubule dynamics are characterized by dynamic instability-the ability of individual microtubules to switch between phases of growth and shrinkage. Dynamic instability can be explained by the GTP-cap model, suggesting that a "cap" of GTP-tubulin subunits at the growing microtubule end has a stabilizing effect, protecting against microtubule catastrophe-the switch from growth to shrinkage. Although the GTP-cap is thought to protect the growing microtubule end, whether the GTP-cap size affects microtubule stability in cells is not known. Notably, microtubule end-binding proteins, EBs, recognize the nucleotide state of tubulin and display comet-like localization at growing microtubule ends, which can be used as a proxy for the GTP-cap. Here, we employ high spatiotemporal resolution imaging to compare the relationship between EB comet size and microtubule dynamics in interphase LLC-PK1 cells to that measured in vitro. Our data reveal that the GTP-cap size in cells scales with the microtubule growth rate in the same way as in vitro. However, we find that microtubule ends in cells can withstand transition to catastrophe even after the EB comet is lost. Thus, our findings suggest that the presence of the GTP-cap is not the determinant of microtubule end stability in cells.
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Affiliation(s)
- Anna Cassidy
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37205
| | - Veronica Farmer
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37205
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710
| | - Göker Arpağ
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37205
- Department of Molecular Biology and Genetics, Kadir Has University, Istanbul, Turkey 34083
| | - Marija Zanic
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37205
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37205
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2
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Di Gregorio E, Staelens M, Hosseinkhah N, Karimpoor M, Liburd J, Lim L, Shankar K, Tuszyński JA. Raman Spectroscopy Reveals Photobiomodulation-Induced α-Helix to β-Sheet Transition in Tubulins: Potential Implications for Alzheimer's and Other Neurodegenerative Diseases. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:1093. [PMID: 38998698 PMCID: PMC11243591 DOI: 10.3390/nano14131093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Revised: 06/03/2024] [Accepted: 06/12/2024] [Indexed: 07/14/2024]
Abstract
In small clinical studies, the application of transcranial photobiomodulation (PBM), which typically delivers low-intensity near-infrared (NIR) to treat the brain, has led to some remarkable results in the treatment of dementia and several neurodegenerative diseases. However, despite the extensive literature detailing the mechanisms of action underlying PBM outcomes, the specific mechanisms affecting neurodegenerative diseases are not entirely clear. While large clinical trials are warranted to validate these findings, evidence of the mechanisms can explain and thus provide credible support for PBM as a potential treatment for these diseases. Tubulin and its polymerized state of microtubules have been known to play important roles in the pathology of Alzheimer's and other neurodegenerative diseases. Thus, we investigated the effects of PBM on these cellular structures in the quest for insights into the underlying therapeutic mechanisms. In this study, we employed a Raman spectroscopic analysis of the amide I band of polymerized samples of tubulin exposed to pulsed low-intensity NIR radiation (810 nm, 10 Hz, 22.5 J/cm2 dose). Peaks in the Raman fingerprint region (300-1900 cm-1)-in particular, in the amide I band (1600-1700 cm-1)-were used to quantify the percentage of protein secondary structures. Under this band, hidden signals of C=O stretching, belonging to different structures, are superimposed, producing a complex signal as a result. An accurate decomposition of the amide I band is therefore required for the reliable analysis of the conformation of proteins, which we achieved through a straightforward method employing a Voigt profile. This approach was validated through secondary structure analyses of unexposed control samples, for which comparisons with other values available in the literature could be conducted. Subsequently, using this validated method, we present novel findings of statistically significant alterations in the secondary structures of polymerized NIR-exposed tubulin, characterized by a notable decrease in α-helix content and a concurrent increase in β-sheets compared to the control samples. This PBM-induced α-helix to β-sheet transition connects to reduced microtubule stability and the introduction of dynamism to allow for the remodeling and, consequently, refreshing of microtubule structures. This newly discovered mechanism could have implications for reducing the risks associated with brain aging, including neurodegenerative diseases like Alzheimer's disease, through the introduction of an intervention following this transition.
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Affiliation(s)
- Elisabetta Di Gregorio
- Department of Physics, Faculty of Science, University of Alberta, Edmonton, AB T6G 2E1, Canada
- Department of Mechanical and Aerospace Engineering (DIMEAS), Faculty of Biomedical Engineering, Polytechnic University of Turin, 10129 Turin, Italy
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Michael Staelens
- Department of Physics, Faculty of Science, University of Alberta, Edmonton, AB T6G 2E1, Canada
- Instituto de Física Corpuscular, CSIC–Universitat de València, Carrer Catedràtic José Beltrán 2, 46980 Paterna, Spain
| | | | | | | | - Lew Lim
- Vielight Inc., Toronto, ON M4Y 2G8, Canada
| | - Karthik Shankar
- Department of Electrical and Computer Engineering, Faculty of Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
| | - Jack A. Tuszyński
- Department of Physics, Faculty of Science, University of Alberta, Edmonton, AB T6G 2E1, Canada
- Department of Mechanical and Aerospace Engineering (DIMEAS), Faculty of Biomedical Engineering, Polytechnic University of Turin, 10129 Turin, Italy
- Department of Data Science and Engineering, Silesian University of Technology, 44-100 Gliwice, Poland
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3
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Avila J, Marco J, Plascencia-Villa G, Bajic VP, Perry G. Could there be an experimental way to link consciousness and quantum computations of brain microtubules? Front Neurosci 2024; 18:1430432. [PMID: 38979125 PMCID: PMC11228156 DOI: 10.3389/fnins.2024.1430432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Accepted: 05/29/2024] [Indexed: 07/10/2024] Open
Affiliation(s)
- Jesús Avila
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
| | - Jesús Marco
- Instituto de Física de Cantabria (CSIC-UC), Santander, Spain
| | - Germán Plascencia-Villa
- Department of Neuroscience, Developmental and Regenerative Biology, The University of Texas at San Antonio, San Antonio, TX, United States
| | - Vladan P. Bajic
- Laboratory for Radiobiology and Molecular Genetics, Department of Health and Environment, “VINČA” Institute of Nuclear Sciences-National Institute of the Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - George Perry
- Department of Neuroscience, Developmental and Regenerative Biology, The University of Texas at San Antonio, San Antonio, TX, United States
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4
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Deng X, Seguinot BO, Bradshaw G, Lee JS, Coy S, Kalocsay M, Santagata S, Mitchison T. STMND1 is a phylogenetically ancient stathmin which localizes to motile cilia and exhibits nuclear translocation that is inhibited when soluble tubulin concentration increases. Mol Biol Cell 2024; 35:ar82. [PMID: 38630521 PMCID: PMC11238091 DOI: 10.1091/mbc.e23-12-0514] [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: 01/02/2024] [Revised: 03/29/2024] [Accepted: 04/11/2024] [Indexed: 05/14/2024] Open
Abstract
Stathmins are small, unstructured proteins that bind tubulin dimers and are implicated in several human diseases, but whose function remains unknown. We characterized a new stathmin, STMND1 (Stathmin Domain Containing 1) as the human representative of an ancient subfamily. STMND1 features a N-terminal myristoylated and palmitoylated motif which directs it to membranes and a tubulin-binding stathmin-like domain (SLD) that contains an internal nuclear localization signal. Biochemistry and proximity labeling showed that STMND1 binds tubulin, and live imaging showed that tubulin binding inhibits translocation from cellular membranes to the nucleus. STMND1 is highly expressed in multiciliated epithelial cells, where it localizes to motile cilia. Overexpression in a model system increased the length of primary cilia. Our study suggests that the most ancient stathmins have cilium-related functions that involve sensing soluble tubulin.
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Affiliation(s)
- Xiang Deng
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Bryan O. Seguinot
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
| | - Gary Bradshaw
- Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Jong Suk Lee
- Ludwig Center at Harvard, Harvard Medical School, Boston, MA 02115
- Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA 02115
- Department of Pathology, Brigham and Women’s Hospital, Boston, MA 02115
| | - Shannon Coy
- Ludwig Center at Harvard, Harvard Medical School, Boston, MA 02115
- Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA 02115
- Department of Pathology, Brigham and Women’s Hospital, Boston, MA 02115
| | - Marian Kalocsay
- Department of Experimental Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX 77030
| | - Sandro Santagata
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
- Ludwig Center at Harvard, Harvard Medical School, Boston, MA 02115
- Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA 02115
- Department of Pathology, Brigham and Women’s Hospital, Boston, MA 02115
| | - Timothy Mitchison
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
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5
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Wethekam LC, Moore JK. Tubulin isotype regulation maintains asymmetric requirement for α-tubulin over β-tubulin. J Cell Biol 2023; 222:e202202102. [PMID: 36719400 PMCID: PMC9930134 DOI: 10.1083/jcb.202202102] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 07/19/2022] [Accepted: 11/14/2022] [Indexed: 02/01/2023] Open
Abstract
How cells regulate α- and β-tubulin to meet the demand for αβ-heterodimers and avoid consequences of monomer imbalance is not understood. We investigate the role of gene copy number and how shifting expression of α- or β-tubulin genes impacts tubulin proteostasis and microtubule function in Saccharomyces cerevisiae. We find that α-tubulin gene copy number is important for maintaining excess α-tubulin protein compared to β-tubulin protein. Excess α-tubulin prevents accumulation of super-stoichiometric β-tubulin, which leads to loss of microtubules, formation of non-microtubule assemblies of tubulin, and disrupts cell proliferation. In contrast, sub-stoichiometric β-tubulin or overexpression of α-tubulin has minor effects. We provide evidence that yeast cells equilibrate α-tubulin protein concentration when α-tubulin isotype expression is increased. We propose an asymmetric relationship between α- and β-tubulins, in which α-tubulins are maintained in excess to supply αβ-heterodimers and limit the accumulation of β-tubulin monomers.
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Affiliation(s)
- Linnea C. Wethekam
- 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
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6
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Xie P. A model for the catalytic activity of microtubule polymerases. Cytoskeleton (Hoboken) 2023; 80:7-20. [PMID: 36305831 DOI: 10.1002/cm.21734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 10/04/2022] [Accepted: 10/22/2022] [Indexed: 11/07/2022]
Abstract
A XMAP215/Stu2/Alp14 polymerase can catalyze processively the tubulin addition to the microtubule (MT) plus end. In this work, a model is proposed for the underlying molecular mechanism of the polymerase activity, where the polymerase can not only catalyze processively the tubulin addition to but also promote the tubulin removal from the MT plus end. Based on the model the dynamics of both the wild-type and mutant polymerases is studied theoretically, explaining consistently and well various available experimental data. To further test the model, predicted results are provided.
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Affiliation(s)
- Ping Xie
- Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing, China
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7
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Peng J, Zeng Y, Hu X, Huang S, Gao X, Tian D, Tian S, Qiu L, Liu J, Dong R, Zhan W, Qin C, Guang B, Yang T. KC-180-2 Exerts Anti-SCLC Effects via Dual Inhibition of Tubulin Polymerization and Src Signaling. ACS OMEGA 2022; 7:32164-32175. [PMID: 36120000 PMCID: PMC9476193 DOI: 10.1021/acsomega.2c03408] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 08/17/2022] [Indexed: 06/15/2023]
Abstract
In this study, a series of N-benzyl-2-(5-phenylpyridin-2-yl) acetamide-based derivatives were successfully designed and synthesized as anti-cancer agents. KC-180-2 was screened as a potentially leading compound with dual mechanisms of action: Src signaling and tubulin polymerization inhibition. It efficiently suppressed the proliferation of five cancer cell lines (MDA-MB-231, H446, SKOV-3, HepG2, and HT29), with IC50 values ranging from 5 to 188 nM, especially small-cell lung cancer (SCLC) cells (IC50, 5 nM). Correspondingly, it exerted a significant therapeutic effect on the H446 small-cell lung cancer xenograft model, significantly reducing the volume of tumors without obvious toxicity. Mechanistically, this compound significantly inhibited the polymerization of purified tubulin in vitro, inducing G2/M cell cycle arrest and binding to the kinase catalytic domain of the Src protein, which reduced the phosphorylation of Src. Thus, KC-180-2 is a potential lead compound for the further development of a new anti-tumor drug against SCLC.
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Affiliation(s)
- Jian Peng
- School
of Pharmacy, Chengdu Medical College, No. 783, Xindu Avenue, Xindu District, Chengdu, Sichuan Province 610500, China
| | - Yisheng Zeng
- School
of Pharmacy, Chengdu Medical College, No. 783, Xindu Avenue, Xindu District, Chengdu, Sichuan Province 610500, China
| | - Xiaojun Hu
- School
of Pharmacy, Chengdu Medical College, No. 783, Xindu Avenue, Xindu District, Chengdu, Sichuan Province 610500, China
| | - Sheng Huang
- Chengdu
Biobel Biotechnology Co., Ltd., No. 88, Keyuan South Road, New and High-Tech Zone, Chengdu, Sichuan Province 610094, China
| | - Xiaofang Gao
- School
of Pharmacy, Chengdu Medical College, No. 783, Xindu Avenue, Xindu District, Chengdu, Sichuan Province 610500, China
| | - Dong Tian
- School
of Pharmacy, Chengdu Medical College, No. 783, Xindu Avenue, Xindu District, Chengdu, Sichuan Province 610500, China
| | - Shuting Tian
- School
of Pharmacy, Chengdu Medical College, No. 783, Xindu Avenue, Xindu District, Chengdu, Sichuan Province 610500, China
| | - Lan Qiu
- School
of Pharmacy, Chengdu Medical College, No. 783, Xindu Avenue, Xindu District, Chengdu, Sichuan Province 610500, China
| | - Jin Liu
- School
of Pharmacy, Chengdu Medical College, No. 783, Xindu Avenue, Xindu District, Chengdu, Sichuan Province 610500, China
| | - Renhan Dong
- Chengdu
Biobel Biotechnology Co., Ltd., No. 88, Keyuan South Road, New and High-Tech Zone, Chengdu, Sichuan Province 610094, China
| | - Wei Zhan
- Chengdu
Biobel Biotechnology Co., Ltd., No. 88, Keyuan South Road, New and High-Tech Zone, Chengdu, Sichuan Province 610094, China
| | - Chuanjun Qin
- Chengdu
Biobel Biotechnology Co., Ltd., No. 88, Keyuan South Road, New and High-Tech Zone, Chengdu, Sichuan Province 610094, China
| | - Bing Guang
- Chengdu
Biobel Biotechnology Co., Ltd., No. 88, Keyuan South Road, New and High-Tech Zone, Chengdu, Sichuan Province 610094, China
| | - Tai Yang
- School
of Pharmacy, Chengdu Medical College, No. 783, Xindu Avenue, Xindu District, Chengdu, Sichuan Province 610500, China
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8
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Grignard J, Lamamy V, Vermersch E, Delagrange P, Stephan JP, Dorval T, Fages F. Mathematical modeling of the microtubule detyrosination/tyrosination cycle for cell-based drug screening design. PLoS Comput Biol 2022; 18:e1010236. [PMID: 35759459 PMCID: PMC9236252 DOI: 10.1371/journal.pcbi.1010236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 05/20/2022] [Indexed: 11/18/2022] Open
Abstract
Microtubules and their post-translational modifications are involved in major cellular processes. In severe diseases such as neurodegenerative disorders, tyrosinated tubulin and tyrosinated microtubules are in lower concentration. We present here a mechanistic mathematical model of the microtubule tyrosination cycle combining computational modeling and high-content image analyses to understand the key kinetic parameters governing the tyrosination status in different cellular models. That mathematical model is parameterized, firstly, for neuronal cells using kinetic values taken from the literature, and, secondly, for proliferative cells, by a change of two parameter values obtained, and shown minimal, by a continuous optimization procedure based on temporal logic constraints to formalize experimental high-content imaging data. In both cases, the mathematical models explain the inability to increase the tyrosination status by activating the Tubulin Tyrosine Ligase enzyme. The tyrosinated tubulin is indeed the product of a chain of two reactions in the cycle: the detyrosinated microtubule depolymerization followed by its tyrosination. The tyrosination status at equilibrium is thus limited by both reaction rates and activating the tyrosination reaction alone is not effective. Our computational model also predicts the effect of inhibiting the Tubulin Carboxy Peptidase enzyme which we have experimentally validated in MEF cellular model. Furthermore, the model predicts that the activation of two particular kinetic parameters, the tyrosination and detyrosinated microtubule depolymerization rate constants, in synergy, should suffice to enable an increase of the tyrosination status in living cells.
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Affiliation(s)
- Jeremy Grignard
- Pole of Activity Data Sciences and Data Management, Institut de Recherches Servier (IdRS), Croissy-sur-Seine, France
- * E-mail: (JG); (TD); (FF)
| | - Véronique Lamamy
- Pole of Activity Cellular Sciences, Institut de Recherches Servier (IdRS), Croissy-sur-Seine, France
| | - Eva Vermersch
- Pole of Activity Cellular Sciences, Institut de Recherches Servier (IdRS), Croissy-sur-Seine, France
| | - Philippe Delagrange
- Therapeutic Area Neuropsychiatry and Immunoinflammation, Institut de Recherches Servier (IdRS), Croissy-sur-Seine, France
| | - Jean-Philippe Stephan
- In Vitro Pharmacology Unit, Institut de Recherches Servier (IdRS), Croissy-sur-Seine, France
| | - Thierry Dorval
- Pole of Activity Data Sciences and Data Management, Institut de Recherches Servier (IdRS), Croissy-sur-Seine, France
- * E-mail: (JG); (TD); (FF)
| | - François Fages
- Team Project Lifeware, Institut National de Recherche en Informatique et Automatique, Inria Saclay, Palaiseau, France
- * E-mail: (JG); (TD); (FF)
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9
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Krajka V, Vulinovic F, Genova M, Tanzer K, Jijumon AS, Bodakuntla S, Tennstedt S, Mueller-Fielitz H, Meier B, Janke C, Klein C, Rakovic A. H-ABC- and dystonia-causing TUBB4A mutations show distinct pathogenic effects. SCIENCE ADVANCES 2022; 8:eabj9229. [PMID: 35275727 PMCID: PMC8916731 DOI: 10.1126/sciadv.abj9229] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 01/22/2022] [Indexed: 06/14/2023]
Abstract
Mutations in the brain-specific β-tubulin 4A (TUBB4A) gene cause a broad spectrum of diseases, ranging from dystonia (DYT-TUBB4A) to hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC). Currently, the mechanisms of how TUBB4A variants lead to this pleiotropic manifestation remain elusive. Here, we investigated whether TUBB4A mutations causing either DYT-TUBB4A (p.R2G and p.Q424H) or H-ABC (p.R2W and p.D249N) exhibit differential effects at the molecular and cellular levels. Using live-cell imaging of disease-relevant oligodendrocytes and total internal reflection fluorescence microscopy of whole-cell lysates, we observed divergent impact on microtubule polymerization and microtubule integration, partially reflecting the observed pleiotropy. Moreover, in silico simulations demonstrated that the mutants rarely adopted a straight heterodimer conformation in contrast to wild type. In conclusion, for most of the examined variants, we deciphered potential molecular disease mechanisms that may lead to the diverse clinical manifestations and phenotype severity across and within each TUBB4A-related disease.
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Affiliation(s)
- Victor Krajka
- Institute of Neurogenetics, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
- Institute of Microtechnology (IMT), Technische Universität Braunschweig, Braunschweig 38124, Germany
| | - Franca Vulinovic
- Institute of Neurogenetics, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
| | - Mariya Genova
- Institut Curie, Université PSL, CNRS UMR3348, 91401 Orsay, France
- Université Paris-Saclay, CNRS UMR3348, 91401 Orsay, France
| | - Kerstin Tanzer
- Institute of Neurogenetics, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
| | - A. S. Jijumon
- Institut Curie, Université PSL, CNRS UMR3348, 91401 Orsay, France
- Université Paris-Saclay, CNRS UMR3348, 91401 Orsay, France
| | - Satish Bodakuntla
- Institut Curie, Université PSL, CNRS UMR3348, 91401 Orsay, France
- Université Paris-Saclay, CNRS UMR3348, 91401 Orsay, France
| | - Stephanie Tennstedt
- Institute for Cardiogenetics, University of Lübeck, 23562 Lübeck, Germany
- DZHK (German Research Centre for Cardiovascular Research), partner site Hamburg/Lübeck/Kiel, 23562 Lübeck, Germany
- University Heart Center Lübeck, 23562 Lübeck, Germany
| | - Helge Mueller-Fielitz
- Institute for Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Ratzeburger Allee 160, 23562 Lübeck, Germany
| | - Britta Meier
- Institute of Neurogenetics, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
| | - Carsten Janke
- Institut Curie, Université PSL, CNRS UMR3348, 91401 Orsay, France
- Université Paris-Saclay, CNRS UMR3348, 91401 Orsay, France
| | - Christine Klein
- Institute of Neurogenetics, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
| | - Aleksandar Rakovic
- Institute of Neurogenetics, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
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10
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Jijumon AS, Bodakuntla S, Genova M, Bangera M, Sackett V, Besse L, Maksut F, Henriot V, Magiera MM, Sirajuddin M, Janke C. Lysate-based pipeline to characterize microtubule-associated proteins uncovers unique microtubule behaviours. Nat Cell Biol 2022; 24:253-267. [PMID: 35102268 DOI: 10.1038/s41556-021-00825-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 11/23/2021] [Indexed: 12/22/2022]
Abstract
The microtubule cytoskeleton forms complex macromolecular assemblies with a range of microtubule-associated proteins (MAPs) that have fundamental roles in cell architecture, division and motility. Determining how an individual MAP modulates microtubule behaviour is an important step in understanding the physiological roles of various microtubule assemblies. To characterize how MAPs control microtubule properties and functions, we developed an approach allowing for medium-throughput analyses of MAPs in cell-free conditions using lysates of mammalian cells. Our pipeline allows for quantitative as well as ultrastructural analyses of microtubule-MAP assemblies. Analysing 45 bona fide and potential mammalian MAPs, we uncovered previously unknown activities that lead to distinct and unique microtubule behaviours such as microtubule coiling or hook formation, or liquid-liquid phase separation along the microtubule lattice that initiates microtubule branching. We have thus established a powerful tool for a thorough characterization of a wide range of MAPs and MAP variants, thus opening avenues for the determination of mechanisms underlying their physiological roles and pathological implications.
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Affiliation(s)
- A S Jijumon
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France
- Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Satish Bodakuntla
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France
- Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Mariya Genova
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France
- Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Mamata Bangera
- Institute for Stem Cell Science and Regenerative Medicine (inStem), Bangalore, India
| | - Violet Sackett
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France
- Université Paris-Saclay, CNRS UMR3348, Orsay, France
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA
| | - Laetitia Besse
- Institut Curie, Université Paris-Saclay, Centre d'Imagerie Multimodale INSERM US43, CNRS UMS2016, Orsay, France
| | - Fatlinda Maksut
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France
- Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Veronique Henriot
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France
- Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Maria M Magiera
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France
- Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | | | - Carsten Janke
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France.
- Université Paris-Saclay, CNRS UMR3348, Orsay, France.
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11
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Park K, Hoff KJ, Wethekam L, Stence N, Saenz M, Moore JK. Kinetically Stabilizing Mutations in Beta Tubulins Create Isotype-Specific Brain Malformations. Front Cell Dev Biol 2021; 9:765992. [PMID: 34869359 PMCID: PMC8637541 DOI: 10.3389/fcell.2021.765992] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 10/29/2021] [Indexed: 11/13/2022] Open
Abstract
Mutations in the family of genes encoding the tubulin subunits of microtubules are associated with a spectrum of human brain malformations known as tubulinopathies. How these mutations impact tubulin activity to give rise to distinct developmental consequences is poorly understood. Here we report two patients exhibiting brain malformations characteristic of tubulinopathies and heterozygous T178M missense mutations in different β-tubulin genes, TUBB2A or TUBB3. RNAseq analysis indicates that both TUBB2A and TUBB3 are expressed in the brain during development, but only TUBB2A maintains high expression in neurons into adulthood. The T178 residue is highly conserved in β-tubulins and located in the exchangeable GTP-binding pocket of β-tubulin. To determine the impact of T178M on β-tubulin function we created an analogous mutation in the β-tubulin of budding yeast and show that the substitution acts dominantly to produce kinetically stabilized microtubules that assemble and disassemble slowly, with fewer transitions between these states. In vitro experiments with purified mutant tubulin demonstrate that T178M decreases the intrinsic assembly activity of β-tubulin and forms microtubules that rarely transition to disassembly. We provide evidence that the T178M substitution disrupts GTPase-dependent conformational changes in tubulin, providing a mechanistic explanation for kinetic stabilization. Our findings demonstrate the importance of tubulin’s GTPase activity during brain development, and indicate that tubulin isotypes play different, important roles during brain development.
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Affiliation(s)
- Kristen Park
- Department of Pediatrics and Neurology, Children's Hospital Colorado, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Katelyn J Hoff
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Linnea Wethekam
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Nicholas Stence
- Section of Pediatric Radiology, Department of Radiology, Children's Hospital Colorado, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Margarita Saenz
- Section of Genetics, Department of Pediatrics, Children's Hospital Colorado, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
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12
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Urazbaev A, Serikbaeva A, Tvorogova A, Dusenbayev A, Kauanova S, Vorobjev I. On the Relationship Between EB-3 Profiles and Microtubules Growth in Cultured Cells. Front Mol Biosci 2021; 8:745089. [PMID: 34820422 PMCID: PMC8606533 DOI: 10.3389/fmolb.2021.745089] [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: 07/21/2021] [Accepted: 09/27/2021] [Indexed: 11/13/2022] Open
Abstract
Microtubules are dynamic structures undergoing rapid growth and shrinkage in living cells and in vitro. The growth of microtubules in vitro was analyzed with subpixel precision (Maurer et al., Current Biology, 2014, 24 (4), 372-384); however, to what extent these results could be applied for microtubules growing in vivo remains largely unknown. Particularly, the question is whether microtubule growth velocity in cells could be sufficiently approximated by a Gaussian distribution or its variability requires a more sophisticated description? Addressing this question, we used time-lapse microscopy and mathematical modeling, and we analyzed EB-3 comets forming on microtubules of cultured cells with subpixel precision. Parameters of comets (shape, form, and velocity) were used as topological characteristics of 3D voxel objects. Using regression analysis, we determined the real positions of the microtubule tips in time-lapse sequences. By exponential decay fitting of the restored comet intensity profile, we found that in vivo EB-3 rapidly exchanges on growing microtubule ends with a decoration time ∼ 2 s. We next developed the model showing that the best correlation between comet length and microtubule end growth velocity is at time intervals close to the decoration time. In the cells, EB comet length positively correlates with microtubule growth velocity in preceding time intervals, while demonstrating no correlation in subsequent time intervals. Correlation between comet length and instantaneous growth velocity of microtubules remains under nocodazole treatment when mean values of both parameters decrease. Our data show that the growth of microtubules in living cells is well-approximated by a constant velocity with large stochastic fluctuations.
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Affiliation(s)
- Arshat Urazbaev
- National Laboratory Astana, Nazarbayev University, Nur-Sultan, Kazakhstan
| | - Anara Serikbaeva
- Laboratory of Biophotonics and Imaging, National Laboratory Astana, Nazarbayev University, Nur-Sultan, Kazakhstan.,Department of Physiology and Biophysics (M/C 901), University of Illinois at Chicago, Chicago, IL, United States
| | - Anna Tvorogova
- A.N.Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Azamat Dusenbayev
- National Laboratory Astana, Nazarbayev University, Nur-Sultan, Kazakhstan
| | - Sholpan Kauanova
- Laboratory of Biophotonics and Imaging, National Laboratory Astana, Nazarbayev University, Nur-Sultan, Kazakhstan.,Department of Biology, School of Sciences and Humanities, Nazarbayev University, Nur-Sultan, Kazakhstan
| | - Ivan Vorobjev
- Laboratory of Biophotonics and Imaging, National Laboratory Astana, Nazarbayev University, Nur-Sultan, Kazakhstan.,A.N.Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Department of Biology, School of Sciences and Humanities, Nazarbayev University, Nur-Sultan, Kazakhstan
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13
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Lin Y, Fichou Y, Longhini AP, Llanes LC, Yin P, Bazan GC, Kosik KS, Han S. Liquid-Liquid Phase Separation of Tau Driven by Hydrophobic Interaction Facilitates Fibrillization of Tau. J Mol Biol 2021; 433:166731. [PMID: 33279579 PMCID: PMC7855949 DOI: 10.1016/j.jmb.2020.166731] [Citation(s) in RCA: 69] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/29/2020] [Accepted: 11/30/2020] [Indexed: 11/17/2022]
Abstract
Amyloid aggregation of tau protein is implicated in neurodegenerative diseases, yet its facilitating factors are poorly understood. Recently, tau has been shown to undergo liquid liquid phase separation (LLPS) both in vivo and in vitro. LLPS was shown to facilitate tau amyloid aggregation in certain cases, while being independent of aggregation in other cases. It is therefore important to understand the differentiating properties that resolve this apparent conflict. We report on a model system of hydrophobically driven LLPS induced by high salt concentration (LLPS-HS), and compare it to electrostatically driven LLPS represented by tau-RNA/heparin complex coacervation (LLPS-ED). We show that LLPS-HS promotes tau protein dehydration, undergoes maturation and directly leads to canonical tau fibrils, while LLPS-ED is reversible, remains hydrated and does not promote amyloid aggregation. We show that the nature of the interaction driving tau condensation is a differentiating factor between aggregation-prone and aggregation-independent LLPS.
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Affiliation(s)
- Yanxian Lin
- Biomolecular Science and Engineering, University of California, Santa Barbara, CA 93106, United States
| | - Yann Fichou
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, United States
| | - Andrew P Longhini
- Molecular, Cell and Developmental Biology, University of California, Santa Barbara, CA 93106, United States
| | - Luana C Llanes
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, United States; Center for Polymers and Organic Solids, University of California, Santa Barbara, CA 93106, United States
| | - Pengyi Yin
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, United States
| | - Guillermo C Bazan
- Departments of Chemistry and Chemical Engineering, National University of Singapore, 117543, Singapore
| | - Kenneth S Kosik
- Molecular, Cell and Developmental Biology, University of California, Santa Barbara, CA 93106, United States; Neuroscience Research Institute, University of California, Santa Barbara, CA 93106, United States
| | - Songi Han
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, United States; Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, United States.
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14
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Orbach R, Howard J. Purification of Ciliary Tubulin from Chlamydomonas reinhardtii. CURRENT PROTOCOLS IN PROTEIN SCIENCE 2020; 100:e107. [PMID: 32568459 PMCID: PMC7400761 DOI: 10.1002/cpps.107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Cilia and flagella play essential roles in environmental sensing, cell locomotion, and development. These organelles possess a central microtubule-based structure known as the axoneme, which serves as a scaffold and is crucial for the function of cilia. Despite their key roles, the biochemical and biophysical properties of the ciliary proteins are poorly understood. To address this issue, we have developed a novel method to purify functional tubulins from different parts of the axoneme, namely the central pair and B-tubule. We use the biflagellate green alga Chlamydomonas reinhardtii, a model organism for studying cilia due to the conserved structure of this organelle, availability of genetic tools and a large collection of mutant strains. Our method yields highly purified functional axonemal tubulins in sufficient quantities to be used for in vitro biochemical and biophysical studies, such as microtubule dynamic assays. It takes 7 to 8 days to grow enough cells; the isolation of the flagella and the purification of the axonemal tubulins require an additional two full days.© 2020 Wiley Periodicals LLC. Basic Protocol 1: Growth and harvest of large volume of cell culture Support Protocol: Assembly of homemade concentration apparatus Basic Protocol 2: Isolation of flagella Basic Protocol 3: Tubulin extraction and purification.
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Affiliation(s)
- Ron Orbach
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Jonathon Howard
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
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15
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Tuszynski JA, Friesen D, Freedman H, Sbitnev VI, Kim H, Santelices I, Kalra AP, Patel SD, Shankar K, Chua LO. Microtubules as Sub-Cellular Memristors. Sci Rep 2020; 10:2108. [PMID: 32034179 PMCID: PMC7005844 DOI: 10.1038/s41598-020-58820-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 01/13/2020] [Indexed: 12/26/2022] Open
Abstract
Memristors represent the fourth electrical circuit element complementing resistors, capacitors and inductors. Hallmarks of memristive behavior include pinched and frequency-dependent I–V hysteresis loops and most importantly a functional dependence of the magnetic flux passing through an ideal memristor on its electrical charge. Microtubules (MTs), cylindrical protein polymers composed of tubulin dimers are key components of the cytoskeleton. They have been shown to increase solution’s ionic conductance and re-orient in the presence of electric fields. It has been hypothesized that MTs also possess intrinsic capacitive and inductive properties, leading to transistor-like behavior. Here, we show a theoretical basis and experimental support for the assertion that MTs under specific circumstances behave consistently with the definition of a memristor. Their biophysical properties lead to pinched hysteretic current–voltage dependence as well a classic dependence of magnetic flux on electric charge. Based on the information about the structure of MTs we provide an estimate of their memristance. We discuss its significance for biology, especially neuroscience, and potential for nanotechnology applications.
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Affiliation(s)
- Jack A Tuszynski
- Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, AB, Canada, T6G 1Z2. .,Department of Physics, University of Alberta, Edmonton, AB, Canada, T6G 2E1. .,DIMEAS, Politecnico di Torino, 10129, Turin, Italy.
| | - Douglas Friesen
- Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, AB, Canada, T6G 1Z2
| | - Holly Freedman
- Li Ka Shing Institute of Applied Virology, University of Alberta, Edmonton, AB, Canada, T6G 2E1
| | - Valery I Sbitnev
- St. Petersburg B. P. Konstantinov Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina, Leningrad district, 188350, Russian Federation.,Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
| | - Hyongsuk Kim
- Division of Electronics Engineering, Chonbuk National University, Jeonju, Jeonbuk, 561-756, South Korea
| | - Iara Santelices
- Department of Electrical & Computer Engineering, University of Alberta, Edmonton, AB, Canada, T6G 1H9
| | - Aarat P Kalra
- Department of Physics, University of Alberta, Edmonton, AB, Canada, T6G 2E1
| | - Sahil D Patel
- Department of Electrical & Computer Engineering, University of Alberta, Edmonton, AB, Canada, T6G 1H9
| | - Karthik Shankar
- Department of Electrical & Computer Engineering, University of Alberta, Edmonton, AB, Canada, T6G 1H9
| | - Leon O Chua
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
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16
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Wang X, Chang L, Zhao T, Liu L, Zhang M, Li C, Xie F, Jiang J, Zhu W. Metabolic switch in energy metabolism mediates the sublethal effects induced by glyphosate-based herbicide on tadpoles of a farmland frog Microhyla fissipes. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019; 186:109794. [PMID: 31629188 DOI: 10.1016/j.ecoenv.2019.109794] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 10/08/2019] [Accepted: 10/10/2019] [Indexed: 06/10/2023]
Abstract
Glyphosate-based herbicides (GBHs) are widely-used agricultural chemicals, bringing potential detriments to aquatic organisms. Currently, our understanding of sublethal effects and underlying toxicologic mechanisms of GBHs are still limited, especially in amphibians. Here, the sublethal effects of a commercial GBH (KISSUN®) on tadpoles of a farmland dwelling frog, Microhyla fissipes, were investigated. The 10-d LC50 of "KISSUN®" GBH was 77.5 mg/L. Tadpoles exposed to 60-120 mg/L showed increased preference to higher temperature. After 10 days exposure, obvious growth suppression was observed in survived GBH-stressed tadpoles, characterized by dosage depended decrement in body mass, body width, total length, etc. GBH-stressed tadpoles also showed decreased tail length/snout-vent length ratio and smaller tail muscle fiber diameter. Comparative transcriptomics (control, 60 mg/L and 90 mg/L groups) was conducted to analyze the underlying molecular processes. GBH-stressed tadpoles showed downregulated transcription of ribosomal proteins and cytoskeleton proteins, which could explain their suppressed whole body and tail muscle growth. Moreover, GBH-stressed tadpoles showed transcriptional downregulation of carbohydrate and lipid catabolism, but upregulation of amino acid catabolism. It suggested a metabolic switch from carbohydrate and lipid to amino acid in these tadpoles. Accordingly, there was a trade-off between protein synthesis and energy production in respect to amino acid allocation, and it provided a metabolic explanation for why protein synthesis was downregulated and growth was suppressed in GBH-stressed tadpoles. In combination with existing literatures, we speculated that GBH might directly target the enzymes in carbohydrate and lipid catabolism, and this metabolic effect of GBH might be common to fish and amphibians. In conclusion, our study provided a systematic insight into the sublethal symptoms of GBH-stressed tadpoles, and a metabolic switch from carbohydrate and lipid to amino acid likely underlay some common toxic symptoms of GBHs on both fish and tadpoles.
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Affiliation(s)
- Xungang Wang
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Liming Chang
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Tian Zhao
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China.
| | - Lusha Liu
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
| | - Mengjie Zhang
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
| | - Cheng Li
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
| | - Feng Xie
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
| | - Jianping Jiang
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China.
| | - Wei Zhu
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China.
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17
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Mustyatsa VV, Kostarev AV, Tvorogova AV, Ataullakhanov FI, Gudimchuk NB, Vorobjev IA. Fine structure and dynamics of EB3 binding zones on microtubules in fibroblast cells. Mol Biol Cell 2019; 30:2105-2114. [PMID: 31141458 PMCID: PMC6743451 DOI: 10.1091/mbc.e18-11-0723] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 05/14/2019] [Accepted: 05/21/2019] [Indexed: 11/26/2022] Open
Abstract
End-binding (EB) proteins associate with the growing tips of microtubules (MTs)and modulate their dynamics directly and indirectly, by recruiting essential factors to fine-tune MTs for their many essential roles in cells. Previously EB proteins have been shown to recognize a stabilizing GTP/GDP-Pi cap at the tip of growing MTs, but information about additional EB-binding zones on MTs has been limited. In this work, we studied fluorescence intensity profiles of one of the three mammalian EB-proteins, EB3, fused with red fluorescent protein (RFP). The distribution of EB3 on MTs in mouse fibroblasts frequently deviated from single exponential decay and exhibited secondary peaks. Those secondary peaks, which we refer to as EB3-islands, were detected on 56% comets of growing MTs and were encountered once per 44 s of EB3-RFP comet growth time with about 5 s half-lifetime. The majority of EB3-islands in the vicinity of MT tips was stationary and originated from EB3 comets moving with the growing MT tips. Computational modeling of the decoration of dynamic MT tips by EB3 suggested that the EB3-islands could not be explained simply by a stochastic first-order GTP hydrolysis/phosphate release. We speculate that additional protein factors contribute to EB3 residence time on MTs in cells, likely affecting MT dynamics.
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Affiliation(s)
- V. V. Mustyatsa
- Lomonosov Moscow State University, 119991 Moscow, Russia
- Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology, 117198 Moscow, Russia
| | - A. V. Kostarev
- Lomonosov Moscow State University, 119991 Moscow, Russia
| | | | - F. I. Ataullakhanov
- Lomonosov Moscow State University, 119991 Moscow, Russia
- Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology, 117198 Moscow, Russia
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, 119334 Moscow, Russia
| | - N. B. Gudimchuk
- Lomonosov Moscow State University, 119991 Moscow, Russia
- Dmitry Rogachev National Research Center of Pediatric Hematology, Oncology and Immunology, 117198 Moscow, Russia
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, 119334 Moscow, Russia
| | - I. A. Vorobjev
- Lomonosov Moscow State University, 119991 Moscow, Russia
- Nazarbayev University, 010000 Nur-Sultan, Kazakhstan
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18
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Purification of tubulin with controlled post-translational modifications by polymerization–depolymerization cycles. Nat Protoc 2019; 14:1634-1660. [DOI: 10.1038/s41596-019-0153-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 02/22/2019] [Indexed: 12/27/2022]
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19
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Noell CR, Loftus KM, Cui H, Grewer C, Kizer M, Debler EW, Solmaz SR. A Quantitative Model for BicD2/Cargo Interactions. Biochemistry 2018; 57:6538-6550. [PMID: 30345745 DOI: 10.1021/acs.biochem.8b00987] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Dynein adaptor proteins such as Bicaudal D2 (BicD2) are integral components of the dynein transport machinery, as they recognize cargoes for cell cycle-specific transport and link them to the motor complex. Human BicD2 switches from selecting secretory and Golgi-derived vesicles for transport in G1 and S phase (by recognizing Rab6GTP), to selecting the nucleus for transport in G2 phase (by recognizing nuclear pore protein Nup358), but the molecular mechanisms governing this switch are elusive. Here, we have developed a quantitative model for BicD2/cargo interactions that integrates affinities, oligomeric states, and cellular concentrations of the reactants. BicD2 and cargo form predominantly 2:2 complexes. Furthermore, the affinity of BicD2 toward its cargo Nup358 is higher than that toward Rab6GTP. Based on our calculations, an estimated 1000 BicD2 molecules per cell would be recruited to the nucleus through Nup358 in the absence of regulation. Notably, RanGTP is a negative regulator of the Nup358/BicD2 interaction that weakens the affinity by a factor of 10 and may play a role in averting dynein recruitment to the nucleus outside of the G2 phase. However, our quantitative model predicts that an additional negative regulator remains to be identified. In the absence of negative regulation, the affinity of Nup358 would likely be sufficient to recruit BicD2 to the nucleus in G2 phase. Our quantitative model makes testable predictions of how cellular transport events are orchestrated. These transport processes are important for brain development, cell cycle control, signaling, and neurotransmission at synapses.
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Affiliation(s)
- Crystal R Noell
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , United States
| | - Kyle M Loftus
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , United States
| | - Heying Cui
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , United States
| | - Christof Grewer
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , United States
| | - Megan Kizer
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , United States
| | - Erik W Debler
- Department of Biochemistry & Molecular Biology , Thomas Jefferson University , Philadelphia , Pennsylvania 19107 , United States
| | - Sozanne R Solmaz
- Department of Chemistry , State University of New York at Binghamton , Binghamton , New York 13902 , United States
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20
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Vemu A, Szczesna E, Zehr EA, Spector JO, Grigorieff N, Deaconescu AM, Roll-Mecak A. Severing enzymes amplify microtubule arrays through lattice GTP-tubulin incorporation. Science 2018; 361:eaau1504. [PMID: 30139843 PMCID: PMC6510489 DOI: 10.1126/science.aau1504] [Citation(s) in RCA: 133] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 07/18/2018] [Indexed: 12/16/2022]
Abstract
Spastin and katanin sever and destabilize microtubules. Paradoxically, despite their destructive activity they increase microtubule mass in vivo. We combined single-molecule total internal reflection fluorescence microscopy and electron microscopy to show that the elemental step in microtubule severing is the generation of nanoscale damage throughout the microtubule by active extraction of tubulin heterodimers. These damage sites are repaired spontaneously by guanosine triphosphate (GTP)-tubulin incorporation, which rejuvenates and stabilizes the microtubule shaft. Consequently, spastin and katanin increase microtubule rescue rates. Furthermore, newly severed ends emerge with a high density of GTP-tubulin that protects them against depolymerization. The stabilization of the newly severed plus ends and the higher rescue frequency synergize to amplify microtubule number and mass. Thus, severing enzymes regulate microtubule architecture and dynamics by promoting GTP-tubulin incorporation within the microtubule shaft.
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Affiliation(s)
- Annapurna Vemu
- Cell Biology and Biophysics Unit, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Ewa Szczesna
- Cell Biology and Biophysics Unit, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Elena A Zehr
- Cell Biology and Biophysics Unit, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Jeffrey O Spector
- Cell Biology and Biophysics Unit, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Nikolaus Grigorieff
- Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02454, USA
| | - Alexandra M Deaconescu
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02903, USA
| | - Antonina Roll-Mecak
- Cell Biology and Biophysics Unit, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA.
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, Bethesda, MD 20892, USA
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21
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Yoo TY, Choi JM, Conway W, Yu CH, Pappu RV, Needleman DJ. Measuring NDC80 binding reveals the molecular basis of tension-dependent kinetochore-microtubule attachments. eLife 2018; 7:36392. [PMID: 30044223 PMCID: PMC6089600 DOI: 10.7554/elife.36392] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 07/24/2018] [Indexed: 01/08/2023] Open
Abstract
Proper kinetochore-microtubule attachments, mediated by the NDC80 complex, are required for error-free chromosome segregation. Erroneous attachments are corrected by the tension dependence of kinetochore-microtubule interactions. Here, we present a method, based on fluorescence lifetime imaging microscopy and Förster resonance energy transfer, to quantitatively measure the fraction of NDC80 complexes bound to microtubules at individual kinetochores in living human cells. We found that NDC80 binding is modulated in a chromosome autonomous fashion over prometaphase and metaphase, and is predominantly regulated by centromere tension. We show that this tension dependency requires phosphorylation of the N-terminal tail of Hec1, a component of the NDC80 complex, and the proper localization of Aurora B kinase, which modulates NDC80 binding. Our results lead to a mathematical model of the molecular basis of tension-dependent NDC80 binding to kinetochore microtubules in vivo. When a cell divides, each new cell that forms needs to contain a complete set of DNA, which is stored in structures called chromosomes. So first, the chromosomes duplicate, and the two copies are held together. A protein structure known as a kinetochore then forms on each copy of the chromosome. The kinetochores act as a pair of hands that pull the chromosome copies apart and toward opposite sides of the dividing cell. They do this by grabbing protein ‘ropes’ called microtubules that extend toward the chromosomes from each side of the cell. Kinetochores grip the microtubule ropes more tightly when the connection is under greater tension. This helps the kinetochores to remain attached to the microtubules that will separate the chromosome copies while releasing the microtubules that would pull both copies to the same side. Previous research has shown that hundreds of finger-like structures made out of a protein group called NDC80 extend from each kinetochore ‘hand’ and attach to the microtubules. What remains a mystery is whether and how the NDC80 fingers grip the microtubules more tightly when tension is greater in cells. Yoo et al. developed a technique for counting how many of the available NDC80 fingers of a single kinetochore are attached to microtubules within a living human cell. The new technique combines genetic engineering, fluorescence imaging and statistical methods to quantify the attachment of NDC80 to microtubules over time and space. Yoo et al. found that more NDC80 bound to microtubules when there was greater tension. This relationship between binding and tension depends on an enzyme called Aurora B, which modifies the tip of each NDC80 finger and consequently changes the binding of NDC80 to microtubules. Yoo et al. further showed that Aurora B needs to be properly placed between two kinetochore hands to make NDC80-microtubule binding dependent on tension. Without this tension dependency, chromosomes could segregate unevenly into the newly formed cells – a problem that can lead to cancer, infertility and birth defects. The results presented by Yoo et al. therefore expand our understanding of how these diseases originate and may eventually help researchers to develop new treatments for them.
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Affiliation(s)
- Tae Yeon Yoo
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States.,Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, United States
| | - Jeong-Mo Choi
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, United States.,Center for Biological Systems Engineering, Washington University in St Louis, St Louis, United States
| | - William Conway
- Department of Physics, Harvard University, Cambridge, United States
| | - Che-Hang Yu
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, United States
| | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, United States.,Center for Biological Systems Engineering, Washington University in St Louis, St Louis, United States
| | - Daniel J Needleman
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States.,Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, United States.,John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, United States
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22
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Cassimeris L, Leung JC, Odde DJ. Monte Carlo simulations of microtubule arrays: The critical roles of rescue transitions, the cell boundary, and tubulin concentration in shaping microtubule distributions. PLoS One 2018; 13:e0197538. [PMID: 29782540 PMCID: PMC5962052 DOI: 10.1371/journal.pone.0197538] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 05/03/2018] [Indexed: 01/12/2023] Open
Abstract
Microtubules are dynamic polymers required for a number of processes, including chromosome movement in mitosis. While regulators of microtubule dynamics have been well characterized, we lack a convenient way to predict how the measured dynamic parameters shape the entire microtubule system within a cell, or how the system responds when specific parameters change in response to internal or external signals. Here we describe a Monte Carlo model to simulate an array of dynamic microtubules from parameters including the cell radius, total tubulin concentration, microtubule nucleation rate from the centrosome, and plus end dynamic instability. The algorithm also allows dynamic instability or position of the cell edge to vary during the simulation. Outputs from simulations include free tubulin concentration, average microtubule lengths, length distributions, and individual length changes over time. Using this platform and reported parameters measured in interphase LLCPK1 epithelial cells, we predict that sequestering ~ 15-20% of total tubulin results in fewer microtubules, but promotes dynamic instability of those remaining. Simulations also predict that lowering nucleation rate will increase the stability and average length of the remaining microtubules. Allowing the position of the cell's edge to vary over time changed the average length but not the number of microtubules and generated length distributions consistent with experimental measurements. Simulating the switch from interphase to prophase demonstrated that decreased rescue frequency at prophase is the critical factor needed to rapidly clear the cell of interphase microtubules prior to mitotic spindle assembly. Finally, consistent with several previous simulations, our results demonstrate that microtubule nucleation and dynamic instability in a confined space determines the partitioning of tubulin between monomer and polymer pools. The model and simulations will be useful for predicting changes to the entire microtubule array after modification to one or more parameters, including predicting the effects of tubulin-targeted chemotherapies.
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Affiliation(s)
- Lynne Cassimeris
- Dept. of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - Jessica C Leung
- Dept. of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - David J Odde
- Dept. of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America
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23
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Wegmann S, Eftekharzadeh B, Tepper K, Zoltowska KM, Bennett RE, Dujardin S, Laskowski PR, MacKenzie D, Kamath T, Commins C, Vanderburg C, Roe AD, Fan Z, Molliex AM, Hernandez-Vega A, Muller D, Hyman AA, Mandelkow E, Taylor JP, Hyman BT. Tau protein liquid-liquid phase separation can initiate tau aggregation. EMBO J 2018; 37:e98049. [PMID: 29472250 PMCID: PMC5881631 DOI: 10.15252/embj.201798049] [Citation(s) in RCA: 631] [Impact Index Per Article: 105.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 01/17/2018] [Accepted: 01/19/2018] [Indexed: 11/13/2022] Open
Abstract
The transition between soluble intrinsically disordered tau protein and aggregated tau in neurofibrillary tangles in Alzheimer's disease is unknown. Here, we propose that soluble tau species can undergo liquid-liquid phase separation (LLPS) under cellular conditions and that phase-separated tau droplets can serve as an intermediate toward tau aggregate formation. We demonstrate that phosphorylated or mutant aggregation prone recombinant tau undergoes LLPS, as does high molecular weight soluble phospho-tau isolated from human Alzheimer brain. Droplet-like tau can also be observed in neurons and other cells. We found that tau droplets become gel-like in minutes, and over days start to spontaneously form thioflavin-S-positive tau aggregates that are competent of seeding cellular tau aggregation. Since analogous LLPS observations have been made for FUS, hnRNPA1, and TDP43, which aggregate in the context of amyotrophic lateral sclerosis, we suggest that LLPS represents a biophysical process with a role in multiple different neurodegenerative diseases.
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Affiliation(s)
- Susanne Wegmann
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Bahareh Eftekharzadeh
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Katharina Tepper
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Katarzyna M Zoltowska
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Rachel E Bennett
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Simon Dujardin
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Pawel R Laskowski
- Department for Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland
| | - Danny MacKenzie
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Tarun Kamath
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Caitlin Commins
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Charles Vanderburg
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Allyson D Roe
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Zhanyun Fan
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Amandine M Molliex
- Department of Cell & Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | | | - Daniel Muller
- Department for Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland
| | - Anthony A Hyman
- Department for Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland
| | - Eckhard Mandelkow
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
- Max-Planck Institute for Metabolism Research, Hamburg Outstation c/o DESY, Hamburg, Germany
- CAESAR Research Center, Bonn, Germany
| | - J Paul Taylor
- Department of Cell & Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Bradley T Hyman
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
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24
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Munguía B, Teixeira R, Veroli V, Melian E, Saldaña J, Minteguiaga M, Señorale M, Marín M, Domínguez L. Purification of native M. vogae and H. contortus tubulin by TOG affinity chromatography. Exp Parasitol 2017; 182:37-44. [DOI: 10.1016/j.exppara.2017.09.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 07/26/2017] [Accepted: 09/19/2017] [Indexed: 01/28/2023]
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25
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Howes SC, Geyer EA, LaFrance B, Zhang R, Kellogg EH, Westermann S, Rice LM, Nogales E. Structural differences between yeast and mammalian microtubules revealed by cryo-EM. J Cell Biol 2017; 216:2669-2677. [PMID: 28652389 PMCID: PMC5584162 DOI: 10.1083/jcb.201612195] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 03/31/2017] [Accepted: 05/30/2017] [Indexed: 01/03/2023] Open
Abstract
Yeast MTs do not appear to undergo the lattice compaction seen in mammalian MTs upon GTP hydrolysis. Binding of the +TIP Bim1, both between and within αβ-tubulin dimers, causes compaction of yeast MTs and their rapid disassembly. Microtubules are polymers of αβ-tubulin heterodimers essential for all eukaryotes. Despite sequence conservation, there are significant structural differences between microtubules assembled in vitro from mammalian or budding yeast tubulin. Yeast MTs were not observed to undergo compaction at the interdimer interface as seen for mammalian microtubules upon GTP hydrolysis. Lack of compaction might reflect slower GTP hydrolysis or a different degree of allosteric coupling in the lattice. The microtubule plus end–tracking protein Bim1 binds yeast microtubules both between αβ-tubulin heterodimers, as seen for other organisms, and within tubulin dimers, but binds mammalian tubulin only at interdimer contacts. At the concentrations used in cryo-electron microscopy, Bim1 causes the compaction of yeast microtubules and induces their rapid disassembly. Our studies demonstrate structural differences between yeast and mammalian microtubules that likely underlie their differing polymerization dynamics. These differences may reflect adaptations to the demands of different cell size or range of physiological growth temperatures.
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Affiliation(s)
- Stuart C Howes
- Biophysics Graduate Group, University of California, Berkeley, Berkeley, CA
| | - Elisabeth A Geyer
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX
| | - Benjamin LaFrance
- Molecular and Cell Biology Graduate Program, University of California, Berkeley, Berkeley, CA
| | - Rui Zhang
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA
| | - Elizabeth H Kellogg
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA
| | - Stefan Westermann
- Department of Molecular Genetics, Center for Medical Biotechnology, University of Duisburg-Essen, Essen, Germany
| | - Luke M Rice
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX
| | - Eva Nogales
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA .,Department of Molecular Biology and California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA
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26
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Kaye B, Yoo TY, Foster PJ, Yu CH, Needleman DJ. Bridging length scales to measure polymer assembly. Mol Biol Cell 2017; 28:1379-1388. [PMID: 28356424 PMCID: PMC5426851 DOI: 10.1091/mbc.e16-05-0344] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 03/10/2017] [Accepted: 03/20/2017] [Indexed: 11/11/2022] Open
Abstract
Time-resolvable quantitative measurements of polymer concentration are very useful to elucidate protein polymerization pathways. There are numerous techniques to measure polymer concentrations in purified protein solutions, but few are applicable in vivo. Here we develop a methodology combining microscopy and spectroscopy to overcome the limitations of both approaches for measuring polymer concentration in cells and cell extracts. This technique is based on quantifying the relationship between microscopy and spectroscopy measurements at many locations. We apply this methodology to measure microtubule assembly in tissue culture cells and Xenopus egg extracts using two-photon microscopy with FLIM measurements of FRET. We find that the relationship between FRET and two-photon intensity quantitatively agrees with predictions. Furthermore, FRET and intensity measurements change as expected with changes in acquisition time, labeling ratios, and polymer concentration. Taken together, these results demonstrate that this approach can quantitatively measure microtubule assembly in complex environments. This methodology should be broadly useful for studying microtubule nucleation and assembly pathways of other polymers.
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Affiliation(s)
- Bryan Kaye
- John A. Paulson School of Engineering and Applied Science, Harvard University, Cambridge, MA 02138 .,FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138
| | - Tae Yeon Yoo
- John A. Paulson School of Engineering and Applied Science, Harvard University, Cambridge, MA 02138.,FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138
| | - Peter J Foster
- John A. Paulson School of Engineering and Applied Science, Harvard University, Cambridge, MA 02138.,FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138
| | - Che-Hang Yu
- John A. Paulson School of Engineering and Applied Science, Harvard University, Cambridge, MA 02138.,FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138
| | - Daniel J Needleman
- John A. Paulson School of Engineering and Applied Science, Harvard University, Cambridge, MA 02138.,FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138
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27
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Crépieux P, Poupon A, Langonné-Gallay N, Reiter E, Delgado J, Schaefer MH, Bourquard T, Serrano L, Kiel C. A Comprehensive View of the β-Arrestinome. Front Endocrinol (Lausanne) 2017; 8:32. [PMID: 28321204 PMCID: PMC5337525 DOI: 10.3389/fendo.2017.00032] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 02/07/2017] [Indexed: 01/14/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are membrane receptors critically involved in sensing the environment and orchestrating physiological processes. As such, they transduce extracellular signals such as hormone, neurotransmitters, ions, and light into an integrated cell response. The intracellular trafficking, internalization, and signaling ability of ligand-activated GPCRs are controlled by arrestins, adaptor proteins that they interact with upon ligand binding. β-arrestins 1 and 2 in particular are now considered as hub proteins assembling multiprotein complexes to regulate receptor fate and transduce diversified cell responses. While more than 400 β-arrestin interaction partners have been identified so far, much remains to be learnt on how discrimination between so many binding partners is accomplished. Here, we gathered the interacting partners of β-arrestins through database mining and manual curation of the literature to map the β-arrestin interactome (β-arrestinome). We discussed several parameters that determine compatible (AND) or mutually exclusive (XOR) binding of β-arrestin interactors, such as structural constraints, intracellular abundance, or binding affinity.
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Affiliation(s)
- Pascale Crépieux
- INRA, UMR85, Unité Physiologie de la Reproduction et des Comportements, Nouzilly, France
- «Biology and Bioinformatics of Signaling Systems (BIOS)» Group, CNRS, UMR7247, Nouzilly, France
- Université François Rabelais, Tours, France
- IFCE, Nouzilly, France
- *Correspondence: Pascale Crépieux,
| | - Anne Poupon
- INRA, UMR85, Unité Physiologie de la Reproduction et des Comportements, Nouzilly, France
- «Biology and Bioinformatics of Signaling Systems (BIOS)» Group, CNRS, UMR7247, Nouzilly, France
- Université François Rabelais, Tours, France
- IFCE, Nouzilly, France
| | - Nathalie Langonné-Gallay
- INRA, UMR85, Unité Physiologie de la Reproduction et des Comportements, Nouzilly, France
- «Biology and Bioinformatics of Signaling Systems (BIOS)» Group, CNRS, UMR7247, Nouzilly, France
- Université François Rabelais, Tours, France
- IFCE, Nouzilly, France
| | - Eric Reiter
- INRA, UMR85, Unité Physiologie de la Reproduction et des Comportements, Nouzilly, France
- «Biology and Bioinformatics of Signaling Systems (BIOS)» Group, CNRS, UMR7247, Nouzilly, France
- Université François Rabelais, Tours, France
- IFCE, Nouzilly, France
| | - Javier Delgado
- EMBL/CRG Systems Biology Research Unit, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Martin H. Schaefer
- EMBL/CRG Systems Biology Research Unit, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Thomas Bourquard
- INRA, UMR85, Unité Physiologie de la Reproduction et des Comportements, Nouzilly, France
- «Biology and Bioinformatics of Signaling Systems (BIOS)» Group, CNRS, UMR7247, Nouzilly, France
- Université François Rabelais, Tours, France
- IFCE, Nouzilly, France
| | - Luis Serrano
- EMBL/CRG Systems Biology Research Unit, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain
| | - Christina Kiel
- EMBL/CRG Systems Biology Research Unit, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
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28
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Abstract
Tau is an intrinsically disordered protein with an important role in maintaining the dynamic instability of neuronal microtubules. Despite intensive study, a detailed understanding of the functional mechanism of tau is lacking. Here, we address this deficiency by using intramolecular single-molecule Förster Resonance Energy Transfer (smFRET) to characterize the conformational ensemble of tau bound to soluble tubulin heterodimers. Tau adopts an open conformation on binding tubulin, in which the long-range contacts between both termini and the microtubule binding region that characterize its compact solution structure are diminished. Moreover, the individual repeats within the microtubule binding region that directly interface with tubulin expand to accommodate tubulin binding, despite a lack of extension in the overall dimensions of this region. These results suggest that the disordered nature of tau provides the significant flexibility required to allow for local changes in conformation while preserving global features. The tubulin-associated conformational ensemble is distinct from its aggregation-prone one, highlighting differences between functional and dysfunctional states of tau. Using constraints derived from our measurements, we construct a model of tubulin-bound tau, which draws attention to the importance of the role of tau's conformational plasticity in function.
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29
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Méphon-Gaspard A, Boca M, Pioche-Durieu C, Desforges B, Burgo A, Hamon L, Piétrement O, Pastré D. Role of tau in the spatial organization of axonal microtubules: keeping parallel microtubules evenly distributed despite macromolecular crowding. Cell Mol Life Sci 2016; 73:3745-60. [PMID: 27076215 PMCID: PMC5002045 DOI: 10.1007/s00018-016-2216-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 03/24/2016] [Accepted: 04/01/2016] [Indexed: 02/07/2023]
Abstract
Opposing views have been proposed regarding the role of tau, the principal microtubule-associated protein in axons. On the one hand, tau forms cross-bridges at the interface between microtubules and induces microtubule bundling in neurons. On the other hand, tau is also considered a polymer brush which efficiently separates microtubules. In mature axons, microtubules are indeed arranged in parallel arrays and are well separated from each other. To reconcile these views, we developed a mechanistic model based on in vitro and cellular approaches combined to analytical and numerical analyses. The results indicate that tau forms long-range cross-bridges between microtubules under macromolecular crowding conditions. Tau cross-bridges prevent the redistribution of tau away from the interface between microtubules, which would have occurred in the polymer brush model. Consequently, the short-range attractive force between microtubules induced by macromolecular crowding is avoided and thus microtubules remain well separated from each other. Interestingly, in this unified model, tau diffusion on microtubules enables to keep microtubules evenly distributed in axonal sections at low tau levels.
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Affiliation(s)
- Alix Méphon-Gaspard
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR1204, Université Evry-Val d'Essonne, Evry, 91025, France
| | - Mirela Boca
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR1204, Université Evry-Val d'Essonne, Evry, 91025, France
| | - Catherine Pioche-Durieu
- UMR 8126, CNRS, Gustave Roussy Université Paris Sud, Université Paris-Saclay, Villejuif, 94805, France
| | - Bénédicte Desforges
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR1204, Université Evry-Val d'Essonne, Evry, 91025, France
| | - Andrea Burgo
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR1204, Université Evry-Val d'Essonne, Evry, 91025, France
| | - Loic Hamon
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR1204, Université Evry-Val d'Essonne, Evry, 91025, France
| | - Olivier Piétrement
- UMR 8126, CNRS, Gustave Roussy Université Paris Sud, Université Paris-Saclay, Villejuif, 94805, France
| | - David Pastré
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR1204, Université Evry-Val d'Essonne, Evry, 91025, France.
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30
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Bailey ME, Sackett DL, Ross JL. Katanin Severing and Binding Microtubules Are Inhibited by Tubulin Carboxy Tails. Biophys J 2016; 109:2546-2561. [PMID: 26682813 DOI: 10.1016/j.bpj.2015.11.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 10/30/2015] [Accepted: 11/04/2015] [Indexed: 10/22/2022] Open
Abstract
Microtubule dynamics in cells are regulated by associated proteins that can be either stabilizers or destabilizers. A class of destabilizers that is important in a large number of cellular activities is the microtubule-severing enzymes, yet little is known about how they function. Katanin p60 was the first ATPase associated with microtubule severing. Here, we investigate the activity of katanin severing using a GFP-labeled human version. We quantify the effect of katanin concentration on katanin binding and severing activity. We find that free tubulin can inhibit severing activity by interfering with katanin binding to microtubules. The inhibition is mediated by the sequence of the tubulin and specifically depends on the carboxy-terminal tails. We directly investigate the inhibition effect of tubulin carboxy-terminal tails using peptide sequences of α-, β-, or detyrosinated α-tubulin tails that have been covalently linked to bovine serum albumin. Our results show that β-tubulin tails are the most effective at inhibiting severing, and that detyrosinated α-tubulin tails are the least effective. These results are distinct from those for other severing enzymes and suggest a scheme for regulation of katanin activity in cells dependent on free tubulin concentration and the modification state of the tubulin.
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Affiliation(s)
- Megan E Bailey
- Molecular and Cellular Biology Graduate Program, University of Massachusetts-Amherst, Amherst, Massachusetts; Department of Physics, University of Massachusetts-Amherst, Amherst, Massachusetts
| | - Dan L Sackett
- Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Jennifer L Ross
- Department of Physics, University of Massachusetts-Amherst, Amherst, Massachusetts.
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31
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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.
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32
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Racca JD, Chen YS, Yang Y, Phillips NB, Weiss MA. Human Sex Determination at the Edge of Ambiguity: INHERITED XY SEX REVERSAL DUE TO ENHANCED UBIQUITINATION AND PROTEASOMAL DEGRADATION OF A MASTER TRANSCRIPTION FACTOR. J Biol Chem 2016; 291:22173-22195. [PMID: 27576690 DOI: 10.1074/jbc.m116.741959] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Indexed: 12/15/2022] Open
Abstract
A general problem is posed by analysis of transcriptional thresholds governing cell fate decisions in metazoan development. A model is provided by testis determination in therian mammals. Its key step, Sertoli cell differentiation in the embryonic gonadal ridge, is initiated by SRY, a Y-encoded architectural transcription factor. Mutations in human SRY cause gonadal dysgenesis leading to XY female development (Swyer syndrome). Here, we have characterized an inherited mutation compatible with either male or female somatic phenotypes as observed in an XY father and XY daughter, respectively. The mutation (a crevice-forming substitution at a conserved back surface of the SRY high mobility group box) markedly destabilizes the domain but preserves specific DNA affinity and induced DNA bend angle. On transient transfection of diverse human and rodent cell lines, the variant SRY exhibited accelerated proteasomal degradation (relative to wild type) associated with increased ubiquitination; in vitro susceptibility to ubiquitin-independent ("default") cleavage by the 20S core proteasome was unchanged. The variant's gene regulatory activity (as assessed in a cellular model of the rat embryonic XY gonadal ridge) was reduced by 2-fold relative to wild-type SRY at similar levels of mRNA expression. Chemical proteasome inhibition restored native-like SRY expression and transcriptional activity in association with restored occupancy of a sex-specific enhancer element in principal downstream gene Sox9, demonstrating that the variant SRY exhibits essentially native activity on a per molecule basis. Our findings define a novel mechanism of impaired organogenesis, accelerated ubiquitin-directed proteasomal degradation of a master transcription factor leading to a developmental decision poised at the edge of ambiguity.
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Affiliation(s)
- Joseph D Racca
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Yen-Shan Chen
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Yanwu Yang
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Nelson B Phillips
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Michael A Weiss
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
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Hayashi M, Nishiyama M, Kazayama Y, Toyota T, Harada Y, Takiguchi K. Reversible Morphological Control of Tubulin-Encapsulating Giant Liposomes by Hydrostatic Pressure. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:3794-3802. [PMID: 27023063 DOI: 10.1021/acs.langmuir.6b00799] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Liposomes encapsulating cytoskeletons have drawn much recent attention to develop an artificial cell-like chemical-machinery; however, as far as we know, there has been no report showing isothermally reversible morphological changes of liposomes containing cytoskeletons because the sets of various regulatory factors, that is, their interacting proteins, are required to control the state of every reaction system of cytoskeletons. Here we focused on hydrostatic pressure to control the polymerization state of microtubules (MTs) within cell-sized giant liposomes (diameters ∼10 μm). MT is the cytoskeleton formed by the polymerization of tubulin, and cytoskeletal systems consisting of MTs are very dynamic and play many important roles in living cells, such as the morphogenesis of nerve cells and formation of the spindle apparatus during mitosis. Using real-time imaging with a high-pressure microscope, we examined the effects of hydrostatic pressure on the morphology of tubulin-encapsulating giant liposomes. At ambient pressure (0.1 MPa), many liposomes formed protrusions due to tubulin polymerization within them. When high pressure (60 MPa) was applied, the protrusions shrank within several tens of seconds. This process was repeatedly inducible (around three times), and after the pressure was released, the protrusions regenerated within several minutes. These deformation rates of the liposomes are close to the velocities of migrating or shape-changing living cells rather than the shortening and elongation rates of the single MTs, which have been previously measured. These results demonstrate that the elongation and shortening of protrusions of giant liposomes is repeatedly controllable by regulating the polymerization state of MTs within them by applying and releasing hydrostatic pressure.
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Affiliation(s)
- Masahito Hayashi
- Division of Biological Science, Graduate School of Science, Nagoya University , Nagoya 464-8602, Japan
| | | | | | | | | | - Kingo Takiguchi
- Division of Biological Science, Graduate School of Science, Nagoya University , Nagoya 464-8602, Japan
- Structural Biology Research Center, Nagoya University , Nagoya 464-8601, Japan
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Kubo T, Brown JM, Bellve K, Craige B, Craft JM, Fogarty K, Lechtreck KF, Witman GB. Together, the IFT81 and IFT74 N-termini form the main module for intraflagellar transport of tubulin. J Cell Sci 2016; 129:2106-19. [PMID: 27068536 DOI: 10.1242/jcs.187120] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 04/03/2016] [Indexed: 11/20/2022] Open
Abstract
The assembly and maintenance of most cilia and flagella rely on intraflagellar transport (IFT). Recent in vitro studies have suggested that, together, the calponin-homology domain within the IFT81 N-terminus and the highly basic N-terminus of IFT74 form a module for IFT of tubulin. By using Chlamydomonas mutants for IFT81 and IFT74, we tested this hypothesis in vivo. Modification of the predicted tubulin-binding residues in IFT81 did not significantly affect basic anterograde IFT and length of steady-state flagella but slowed down flagellar regeneration, a phenotype similar to that seen in a strain that lacks the IFT74 N-terminus. In both mutants, the frequency of tubulin transport by IFT was greatly reduced. A double mutant that combined the modifications to IFT81 and IFT74 was able to form only very short flagella. These results indicate that, together, the IFT81 and IFT74 N-termini are crucial for flagellar assembly, and are likely to function as the main module for IFT of tubulin.
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Affiliation(s)
- Tomohiro Kubo
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Jason M Brown
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA Biology Department, Salem State University, Salem, MA 01970, USA
| | - Karl Bellve
- Biomedical Imaging Group, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Branch Craige
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Julie M Craft
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Kevin Fogarty
- Biomedical Imaging Group, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Karl F Lechtreck
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - George B Witman
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
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Gurel PS, Hatch AL, Higgs HN. Connecting the cytoskeleton to the endoplasmic reticulum and Golgi. Curr Biol 2015; 24:R660-R672. [PMID: 25050967 DOI: 10.1016/j.cub.2014.05.033] [Citation(s) in RCA: 121] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A tendency in cell biology is to divide and conquer. For example, decades of painstaking work have led to an understanding of endoplasmic reticulum (ER) and Golgi structure, dynamics, and transport. In parallel, cytoskeletal researchers have revealed a fantastic diversity of structure and cellular function in both actin and microtubules. Increasingly, these areas overlap, necessitating an understanding of both organelle and cytoskeletal biology. This review addresses connections between the actin/microtubule cytoskeletons and organelles in animal cells, focusing on three key areas: ER structure and function; ER-to-Golgi transport; and Golgi structure and function. Making these connections has been challenging for several reasons: the small sizes and dynamic characteristics of some components; the fact that organelle-specific cytoskeletal elements can easily be obscured by more abundant cytoskeletal structures; and the difficulties in imaging membranes and cytoskeleton simultaneously, especially at the ultrastructural level. One major concept is that the cytoskeleton is frequently used to generate force for membrane movement, with two potential consequences: translocation of the organelle, or deformation of the organelle membrane. While initially discussing issues common to metazoan cells in general, we subsequently highlight specific features of neurons, since these highly polarized cells present unique challenges for organellar distribution and dynamics.
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Affiliation(s)
- Pinar S Gurel
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover NH 03755, USA
| | - Anna L Hatch
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover NH 03755, USA
| | - Henry N Higgs
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover NH 03755, USA.
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Tepper K, Biernat J, Kumar S, Wegmann S, Timm T, Hübschmann S, Redecke L, Mandelkow EM, Müller DJ, Mandelkow E. Oligomer formation of tau protein hyperphosphorylated in cells. J Biol Chem 2014; 289:34389-407. [PMID: 25339173 PMCID: PMC4256367 DOI: 10.1074/jbc.m114.611368] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Abnormal phosphorylation (“hyperphosphorylation”) and aggregation of Tau protein are hallmarks of Alzheimer disease and other tauopathies, but their causative connection is still a matter of debate. Tau with Alzheimer-like phosphorylation is also present in hibernating animals, mitosis, or during embryonic development, without leading to pathophysiology or neurodegeneration. Thus, the role of phosphorylation and the distinction between physiological and pathological phosphorylation needs to be further refined. So far, the systematic investigation of highly phosphorylated Tau was difficult because a reliable method of preparing reproducible quantities was not available. Here, we generated full-length Tau (2N4R) in Sf9 cells in a well defined phosphorylation state containing up to ∼20 phosphates as judged by mass spectrometry and Western blotting with phospho-specific antibodies. Despite the high concentration in living Sf9 cells (estimated ∼230 μm) and high phosphorylation, the protein was not aggregated. However, after purification, the highly phosphorylated protein readily formed oligomers, whereas fibrils were observed only rarely. Exposure of mature primary neuronal cultures to oligomeric phospho-Tau caused reduction of spine density on dendrites but did not change the overall cell viability.
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Affiliation(s)
- Katharina Tepper
- From the DZNE, German Center for Neurodegenerative Diseases, 53175 Bonn, Germany, the CAESAR Research Center, 53175 Bonn, Germany
| | - Jacek Biernat
- From the DZNE, German Center for Neurodegenerative Diseases, 53175 Bonn, Germany, the CAESAR Research Center, 53175 Bonn, Germany
| | - Satish Kumar
- From the DZNE, German Center for Neurodegenerative Diseases, 53175 Bonn, Germany, the CAESAR Research Center, 53175 Bonn, Germany
| | - Susanne Wegmann
- the Department of Biosystems Science and Engineering, ETHZ, 4058 Basel, Switzerland
| | - Thomas Timm
- the Institute of Biochemistry, Faculty of Medicine, Justus-Liebig-University, 35390 Giessen, Germany, and
| | - Sabrina Hübschmann
- From the DZNE, German Center for Neurodegenerative Diseases, 53175 Bonn, Germany, the CAESAR Research Center, 53175 Bonn, Germany
| | - Lars Redecke
- the Joint Laboratory for Structural Biology of Infection and Inflammation, University of Hamburg and University of Lübeck, ℅DESY, 22603 Hamburg, Germany
| | - Eva-Maria Mandelkow
- From the DZNE, German Center for Neurodegenerative Diseases, 53175 Bonn, Germany, the CAESAR Research Center, 53175 Bonn, Germany
| | - Daniel J Müller
- the Department of Biosystems Science and Engineering, ETHZ, 4058 Basel, Switzerland
| | - Eckhard Mandelkow
- From the DZNE, German Center for Neurodegenerative Diseases, 53175 Bonn, Germany, the CAESAR Research Center, 53175 Bonn, Germany,
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Racca JD, Chen YS, Maloy JD, Wickramasinghe N, Phillips NB, Weiss MA. Structure-function relationships in human testis-determining factor SRY: an aromatic buttress underlies the specific DNA-bending surface of a high mobility group (HMG) box. J Biol Chem 2014; 289:32410-29. [PMID: 25258310 DOI: 10.1074/jbc.m114.597526] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human testis determination is initiated by SRY, a Y-encoded architectural transcription factor. Mutations in SRY cause 46 XY gonadal dysgenesis with female somatic phenotype (Swyer syndrome) and confer a high risk of malignancy (gonadoblastoma). Such mutations cluster in the SRY high mobility group (HMG) box, a conserved motif of specific DNA binding and bending. To explore structure-function relationships, we constructed all possible substitutions at a site of clinical mutation (W70L). Our studies thus focused on a core aromatic residue (position 15 of the consensus HMG box) that is invariant among SRY-related HMG box transcription factors (the SOX family) and conserved as aromatic (Phe or Tyr) among other sequence-specific boxes. In a yeast one-hybrid system sensitive to specific SRY-DNA binding, the variant domains exhibited reduced (Phe and Tyr) or absent activity (the remaining 17 substitutions). Representative nonpolar variants with partial or absent activity (Tyr, Phe, Leu, and Ala in order of decreasing side-chain volume) were chosen for study in vitro and in mammalian cell culture. The clinical mutation (Leu) was found to markedly impair multiple biochemical and cellular activities as respectively probed through the following: (i) in vitro assays of specific DNA binding and protein stability, and (ii) cell culture-based assays of proteosomal degradation, nuclear import, enhancer DNA occupancy, and SRY-dependent transcriptional activation. Surprisingly, however, DNA bending is robust to this or the related Ala substitution that profoundly impairs box stability. Together, our findings demonstrate that the folding, trafficking, and gene-regulatory function of SRY requires an invariant aromatic "buttress" beneath its specific DNA-bending surface.
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Affiliation(s)
- Joseph D Racca
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Yen-Shan Chen
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - James D Maloy
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Nalinda Wickramasinghe
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Nelson B Phillips
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Michael A Weiss
- From the Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106
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38
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Laflamme G, Tremblay-Boudreault T, Roy MA, Andersen P, Bonneil É, Atchia K, Thibault P, D'Amours D, Kwok BH. Structural maintenance of chromosome (SMC) proteins link microtubule stability to genome integrity. J Biol Chem 2014; 289:27418-31. [PMID: 25135640 DOI: 10.1074/jbc.m114.569608] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Structural maintenance of chromosome (SMC) proteins are key organizers of chromosome architecture and are essential for genome integrity. They act by binding to chromatin and connecting distinct parts of chromosomes together. Interestingly, their potential role in providing connections between chromatin and the mitotic spindle has not been explored. Here, we show that yeast SMC proteins bind directly to microtubules and can provide a functional link between microtubules and DNA. We mapped the microtubule-binding region of Smc5 and generated a mutant with impaired microtubule binding activity. This mutant is viable in yeast but exhibited a cold-specific conditional lethality associated with mitotic arrest, aberrant spindle structures, and chromosome segregation defects. In an in vitro reconstitution assay, this Smc5 mutant also showed a compromised ability to protect microtubules from cold-induced depolymerization. Collectively, these findings demonstrate that SMC proteins can bind to and stabilize microtubules and that SMC-microtubule interactions are essential to establish a robust system to maintain genome integrity.
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Affiliation(s)
- Guillaume Laflamme
- From the Chemical Biology of Cell Division Laboratory, the Laboratory of Cell Cycle Regulation and Chromosome Structure, and
| | | | - Marc-André Roy
- the Laboratory of Cell Cycle Regulation and Chromosome Structure, and
| | | | - Éric Bonneil
- the Laboratory of Proteomics and Bioanalytical Mass Spectrometry, Institute for Research in Immunology and Cancer, and
| | - Kaleem Atchia
- From the Chemical Biology of Cell Division Laboratory
| | - Pierre Thibault
- the Laboratory of Proteomics and Bioanalytical Mass Spectrometry, Institute for Research in Immunology and Cancer, and the Departments of Chemistry
| | - Damien D'Amours
- the Laboratory of Cell Cycle Regulation and Chromosome Structure, and Pathology and Cellular Biology, and
| | - Benjamin H Kwok
- From the Chemical Biology of Cell Division Laboratory, Medicine, Université de Montréal, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada
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Abstract
Tau is a microtubule binding protein that forms pathological aggregates in the brain in Alzheimer's disease and other tauopathies. Disease etiology is thought to arise from loss of native interactions between tau and microtubules, as well as from gain of toxicity tied to tau aggregation, although neither mechanism is well understood. Here we investigate the link between function and disease using disease-associated and disease-motivated mutants of tau. We find that mutations to highly conserved proline residues in repeats 2 and 3 of the microtubule binding domain have differential effects on tau binding to tubulin and the capacity of tau to enhance tubulin polymerization. Notably, mutations to these residues result in an increased affinity for tubulin dimers while having a negligible effect on binding to stabilized microtubules. We measure conformational changes in tau on binding to tubulin that provide a structural framework for the observed altered affinity and function. Additionally, we find that these mutations do not necessarily enhance aggregation, which could have important implications for tau therapeutic strategies that focus solely on searching for tau aggregation inhibitors. We propose a model that describes tau binding to tubulin dimers and a mechanism by which disease-relevant alterations to tau impact its function. Together, these results draw attention to the interaction between tau and free tubulin as playing an important role in mechanisms of tau pathology.
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40
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Denis PA. Heuristic consequences of a load of oxygen in microtubules. Biosystems 2014; 118:17-30. [PMID: 24525190 DOI: 10.1016/j.biosystems.2014.01.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 01/07/2014] [Accepted: 01/31/2014] [Indexed: 11/17/2022]
Abstract
The current cell oxygen paradigm shows some major gaps that have not yet been resolved. Something seems to be lacking for the comprehensive statement of the oxygen distribution in the cell, especially the low cytoplasmic oxygen level. The entrapment of oxygen in microtubules (MTs) resolves the latter observation, as well as the occurrence of an extensive cytoplasmic foam formation. It leads to a novel oxygen paradigm for cells. During the steady-state treadmilling, the mobile cavity would absorb oxygenated cytoplasm forward, entrap gas nuclei and concentrate them. A fluorescence method is described to confirm the in vitro load of oxygen in MTs during their periodic growths and shrinkages. The latter operating mechanism is called the gas dynamic instability (GDI) of MTs. Several known biosystems could rest on the GDI. (1) The GTP-cap is linked with the gas meniscus encountered in a tube filled with gas. The GTP hydrolysis is linked to the conformational change of the GTPase domain according to the bubble pressure, and to the shaking of protofilaments with gas particles (soliton-like waves). (2) The GDI provides a free energy water pump because water molecules have to escape from MT pores when foam concentrates within the MT. Beside ATP hydrolysis in motor proteins, the GDI provides an additional driving force in intracellular transport of cargo. The water streams flowing from the MT through slits organize themselves as water layers between the cargo and the MT surface, and break ionic bridges. It makes the cargo glide over a water rail. (3) The GDI provides a universal motor for chromosome segregation because the depolymerization of kinetochorial MTs is expected to generate a strong cytoplasmic foam. Chromosomes are sucked up according to the pressure difference (or density difference) applied to opposite sides of the kinetochore, which is in agreement with Archimedes' principle of buoyancy. Non-kinetochorial MTs reabsorb foam during GDI. Last, the mitotic spindle is imagined as a gas recycler. (4) The luminal particles within MTs (called MIPs) are imagined as a foam organizer, the luminal proteins being part of the borders and edges of identical bubbles. (5) Last, volatile anesthetics could destabilize MTs through anesthetic-induced bubble nucleation between protofilaments, and therefore causing shear stress and the opening of MT. The load of oxygen in MTs might provide a major advance in this area of research.
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Affiliation(s)
- Pierre A Denis
- SOS Médecins, 50 rue Ville-Pépin, 35400 Saint-Malo, France.
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41
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Bhogaraju S, Cajanek L, Fort C, Blisnick T, Weber K, Taschner M, Mizuno N, Lamla S, Bastin P, Nigg EA, Lorentzen E. Molecular basis of tubulin transport within the cilium by IFT74 and IFT81. Science 2013; 341:1009-12. [PMID: 23990561 DOI: 10.1126/science.1240985] [Citation(s) in RCA: 228] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Intraflagellar transport (IFT) of ciliary precursors such as tubulin from the cytoplasm to the ciliary tip is involved in the construction of the cilium, a hairlike organelle found on most eukaryotic cells. However, the molecular mechanisms of IFT are poorly understood. Here, we found that the two core IFT proteins IFT74 and IFT81 form a tubulin-binding module and mapped the interaction to a calponin homology domain of IFT81 and a highly basic domain in IFT74. Knockdown of IFT81 and rescue experiments with point mutants showed that tubulin binding by IFT81 was required for ciliogenesis in human cells.
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Affiliation(s)
- Sagar Bhogaraju
- Department of Structural Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
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42
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Macromolecular Crowding Pushes Catalyzed Microtubule Growth to Near the Theoretical Limit. Cell Mol Bioeng 2013. [DOI: 10.1007/s12195-013-0292-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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43
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Mandelkow EM, Mandelkow E. Biochemistry and cell biology of tau protein in neurofibrillary degeneration. Cold Spring Harb Perspect Med 2013; 2:a006247. [PMID: 22762014 DOI: 10.1101/cshperspect.a006247] [Citation(s) in RCA: 541] [Impact Index Per Article: 49.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Tau represents the subunit protein of one of the major hallmarks of Alzheimer disease (AD), the neurofibrillary tangles, and is therefore of major interest as an indicator of disease mechanisms. Many of the unusual properties of Tau can be explained by its nature as a natively unfolded protein. Examples are the large number of structural conformations and biochemical modifications (phosphorylation, proteolysis, glycosylation, and others), the multitude of interaction partners (mainly microtubules, but also other cytoskeletal proteins, kinases, and phosphatases, motor proteins, chaperones, and membrane proteins). The pathological aggregation of Tau is counterintuitive, given its high solubility, but can be rationalized by short hydrophobic motifs forming β structures. The aggregation of Tau is toxic in cell and animal models, but can be reversed by suppressing expression or by aggregation inhibitors. This review summarizes some of the structural, biochemical, and cell biological properties of Tau and Tau fibers. Further aspects of Tau as a diagnostic marker and therapeutic target, its involvement in other Tau-based diseases, and its histopathology are covered by other chapters in this volume.
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Affiliation(s)
- Eva-Maria Mandelkow
- Max-Planck Unit for Structural Molecular Biology, c/o DESY, 22607 Hamburg, Germany; DZNE, German Center for Neurodegenerative Diseases, and CAESAR Research Center, 53175 Bonn, Germany.
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Wawra S, Djamei A, Albert I, Nürnberger T, Kahmann R, van West P. In vitro translocation experiments with RxLR-reporter fusion proteins of Avr1b from Phytophthora sojae and AVR3a from Phytophthora infestans fail to demonstrate specific autonomous uptake in plant and animal cells. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:528-36. [PMID: 23547905 DOI: 10.1094/mpmi-08-12-0200-r] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Plant-pathogenic oomycetes have a large set of secreted effectors that can be translocated into their host cells during infection. One group of these effectors are the RxLR effectors for which it has been shown, in a few cases, that the RxLR motif is important for their translocation. It has been suggested that the RxLR-leader sequences alone are enough to translocate the respective effectors into eukaryotic cells through binding to surface-exposed phosphoinositol-3-phosphate. These conclusions were primary based on translocation experiments conducted with recombinant fusion proteins whereby the RxLR leader of RxLR effectors (i.e., Avr1b from Phytophthora sojae) were fused to the green fluorescent protein reporter-protein. However, we failed to observe specific cellular uptake for a comparable fusion protein where the RxLR leader of the P. infestans AVR3a was fused to monomeric red fluorescent protein. Therefore, we reexamined the ability of the reported P. sojae AVR1b RxLR leader to enter eukaryotic cells. Different relevant experiments were performed in three independent laboratories, using fluorescent reporter fusion constructs of AVR3a and Avr1b proteins in a side-by-side comparative study on plant tissue and human and animal cells. We report that we were unable to obtain conclusive evidence for specific RxLR-mediated translocation.
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45
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Szyk A, Piszczek G, Roll-Mecak A. Tubulin tyrosine ligase and stathmin compete for tubulin binding in vitro. J Mol Biol 2013; 425:2412-4. [PMID: 23624152 DOI: 10.1016/j.jmb.2013.04.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2013] [Revised: 04/10/2013] [Accepted: 04/18/2013] [Indexed: 11/17/2022]
Abstract
Tubulin partition between soluble and polymeric forms is tightly regulated in cells. Stathmin and tubulin tyrosine ligase (TTL) each form stable complexes with tubulin and inhibit tubulin polymerization. Here we explore the mutual relationship between these proteins in vitro and demonstrate that full-length stathmin and TTL compete for binding to tubulin and fail to make a stable tubulin:stathmin:TTL triple complex in solution. Moreover, stathmin depresses TTL tubulin tyrosination activity in vitro. These results suggest either that TTL and stathmin have a partially overlapping footprint on the tubulin dimer or that stathmin induces a tubulin conformation incompatible with stable TTL binding.
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Affiliation(s)
- Agnieszka Szyk
- Cell Biology and Biophysics Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
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46
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Cline EN, Li MH, Choi SK, Herbstman JF, Kaul N, Meyhöfer E, Skiniotis G, Baker JR, Larson RG, Walter NG. Paclitaxel-conjugated PAMAM dendrimers adversely affect microtubule structure through two independent modes of action. Biomacromolecules 2013; 14:654-64. [PMID: 23391096 PMCID: PMC3603340 DOI: 10.1021/bm301719b] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Paclitaxel (Taxol) is an anticancer drug that induces mitotic arrest via microtubule hyperstabilization but causes side effects due to its hydrophobicity and cellular promiscuity. The targeted cytotoxicity of hydrophilic paclitaxel-conjugated polyamidoamine (PAMAM) dendrimers has been demonstrated in cultured cancer cells. Mechanisms of action responsible for this cytotoxicity are unknown, that is, whether the cytotoxicity is due to paclitaxel stabilization of microtubules, as is whether paclitaxel is released intracellularly from the dendrimer. To determine whether the conjugated paclitaxel can bind microtubules, we used a combination of ensemble and single microtubule imaging techniques in vitro. We demonstrate that these conjugates adversely affect microtubules by (1) promoting the polymerization and stabilization of microtubules in a paclitaxel-dependent manner, and (2) bundling preformed microtubules in a paclitaxel-independent manner, potentially due to protonation of tertiary amines in the dendrimer interior. Our results provide mechanistic insights into the cytotoxicity of paclitaxel-conjugated PAMAM dendrimers and uncover unexpected risks of using such conjugates therapeutically.
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Affiliation(s)
- Erika N. Cline
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI 48109
- Single Molecule Analysis Group, University of Michigan, Ann Arbor, MI 48109
| | - Ming-Hsin Li
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
- Michigan Nanotechnology Institute for Medicine and Biological Sciences, University of Michigan, Ann Arbor, MI 48109
| | - Seok Ki Choi
- Michigan Nanotechnology Institute for Medicine and Biological Sciences, University of Michigan, Ann Arbor, MI 48109
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | | | - Neha Kaul
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Edgar Meyhöfer
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109
| | | | - James R. Baker
- Michigan Nanotechnology Institute for Medicine and Biological Sciences, University of Michigan, Ann Arbor, MI 48109
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | - Ronald G. Larson
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Nils G. Walter
- Single Molecule Analysis Group, University of Michigan, Ann Arbor, MI 48109
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
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47
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Location-dependent coronary artery diffusive and convective mass transport properties of a lipophilic drug surrogate measured using nonlinear microscopy. Pharm Res 2012; 30:1147-60. [PMID: 23224981 DOI: 10.1007/s11095-012-0950-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 11/27/2012] [Indexed: 10/27/2022]
Abstract
PURPOSE Arterial wall mass transport properties dictate local distribution of biomolecules or locally delivered dugs. Knowing how these properties vary between coronary artery locations could provide insight into how therapy efficacy is altered between arterial locations. METHODS We introduced an indocarbocyanine drug surrogate to the lumens of left anterior descending and right coronary (LADC; RC) arteries from pigs with or without a pressure gradient. Interstitial fluorescent intensity was measured on live samples with multiphoton microscopy. We also measured binding to porcine coronary SMCs in monoculture. RESULTS Diffusive transport constants peaked in the middle sections of the LADC and RC arteries by 2.09 and 2.04 times, respectively, compared to the proximal and distal segments. There was no statistical difference between the average diffusivity value between LADC and RC arteries. The convection coefficients had an upward trend down each artery, with the RC being higher than the LADC by 3.89 times. CONCLUSIONS This study demonstrates that the convective and diffusive transport of lipophilic molecules changes between the LADC and the RC arteries as well as along their length. These results may have important implications in optimizing drug delivery for the treatment of coronary artery disease.
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Samson AL, Knaupp AS, Sashindranath M, Borg RJ, Au AEL, Cops EJ, Saunders HM, Cody SH, McLean CA, Nowell CJ, Hughes VA, Bottomley SP, Medcalf RL. Nucleocytoplasmic coagulation: an injury-induced aggregation event that disulfide crosslinks proteins and facilitates their removal by plasmin. Cell Rep 2012; 2:889-901. [PMID: 23041318 DOI: 10.1016/j.celrep.2012.08.026] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 07/27/2012] [Accepted: 08/24/2012] [Indexed: 11/18/2022] Open
Abstract
Cellular injury causes a myriad of processes that affect proteostasis. We describe nucleocytoplasmic coagulation (NCC), an intracellular disulfide-dependent protein crosslinking event occurring upon late-stage cell death that orchestrates the proteolytic removal of misfolded proteins. In vitro and in vivo models of neuronal injury show that NCC involves conversion of soluble intracellular proteins, including tubulin, into insoluble oligomers. These oligomers, also seen in human brain tissue following neurotrauma, act as a cofactor and substrate for the plasminogen-activating system. In plasminogen(-/-) mice, levels of misfolded β-tubulin were elevated and its clearance delayed following neurotrauma, demonstrating a requirement for plasminogen in the removal of NCC constituents. While additional in vivo studies will further dissect this phenomenon, our study clearly shows that NCC, a process analogous to the formation of thrombi, generates an aggregated protein scaffold that limits release of cellular components and recruits clearance mechanisms to the site of injury.
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Affiliation(s)
- Andre L Samson
- Australian Centre for Blood Diseases, AMREP, Monash University, Melbourne, Victoria 3004, Australia.
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Widlund PO, Podolski M, Reber S, Alper J, Storch M, Hyman AA, Howard J, Drechsel DN. One-step purification of assembly-competent tubulin from diverse eukaryotic sources. Mol Biol Cell 2012; 23:4393-401. [PMID: 22993214 PMCID: PMC3496613 DOI: 10.1091/mbc.e12-06-0444] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A method is presented that allows rapid and efficient purification of native, active tubulin from a variety of species and tissue sources by affinity chromatography. It eliminates the need to use heterologous systems for the study of microtubule-associated proteins and motor proteins, which has been a major issue in microtubule-related research. We have developed a protocol that allows rapid and efficient purification of native, active tubulin from a variety of species and tissue sources by affinity chromatography. The affinity matrix comprises a bacterially expressed, recombinant protein, the TOG1/2 domains from Saccharomyces cerevisiae Stu2, covalently coupled to a Sepharose support. The resin has a high capacity to specifically bind tubulin from clarified crude cell extracts, and, after washing, highly purified tubulin can be eluted under mild conditions. The eluted tubulin is fully functional and can be efficiently assembled into microtubules. The method eliminates the need to use heterologous systems for the study of microtubule-associated proteins and motor proteins, which has been a major issue in microtubule-related research.
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Affiliation(s)
- Per O Widlund
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
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50
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Najafi M, Calvert PD. Transport and localization of signaling proteins in ciliated cells. Vision Res 2012; 75:11-8. [PMID: 22922002 DOI: 10.1016/j.visres.2012.08.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 08/05/2012] [Accepted: 08/08/2012] [Indexed: 11/16/2022]
Abstract
Most cells in the human body elaborate cilia which serve a wide variety of functions, including cell and tissue differentiation during development, sensing physical and chemical properties of the extracellular milieu and mechanical force generation. Common among cilia is the transduction of external stimuli into signals that regulate the activities of the cilia and the cells that possess them. These functions require the transport and localization of specialized proteins to the cilium, a process that many recent studies have shown to be vital for normal cell function and, ultimately, the health of the organism. Here we discuss several mechanisms proposed for the transport and localization of soluble and peripheral membrane proteins to, or their exclusion from the ciliary compartment with a focus on how the structure of the cytoplasm and the size and shape of proteins influence these processes. Additionally, we examine the impact of cell and protein structure on our ability to accurately measure the relative concentrations of fluorescently tagged proteins amongst various cellular domains, which is integral to our understanding of the molecular mechanisms underlying protein localization and transport.
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Affiliation(s)
- Mehdi Najafi
- Department of Ophthalmology and the Center for Vision Research, SUNY Upstate Medical University, United States
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