201
|
Eg5 Overexpression Is Predictive of Poor Prognosis in Hepatocellular Carcinoma Patients. DISEASE MARKERS 2017; 2017:2176460. [PMID: 28684886 PMCID: PMC5480051 DOI: 10.1155/2017/2176460] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 03/25/2017] [Accepted: 04/19/2017] [Indexed: 01/01/2023]
Abstract
Eg5 (kinesin spindle protein) plays an essential role in mitosis. Inhibition of Eg5 function results in cell cycle arrest at mitosis, which leads to cell death. To date, Eg5 expression and its prognostic significance have not been studied in hepatocellular carcinoma (HCC). In this study, 26 freshly frozen HCC tissue samples and matched peritumoral tissue samples were evaluated with a one-step qPCR test and immunohistochemical (IHC) analysis was conducted on 156 HCC samples to investigate the relationships among Eg5 expression, clinicopathological factors, and prognosis. Eg5 mRNA and protein expression levels were significantly higher in HCC tissues relative to matched noncancerous tissues (p < 0.05). High Eg5 protein expression was significantly related to liver cirrhosis (p = 0.038) and TNM stage (p = 0.008). Kaplan-Meier survival and Cox regression analyses revealed that Eg5 overexpression (p = 0.001), liver cirrhosis (p = 0.009), and TNM stage (p = 0.025) were independent prognostic factors for overall survival. These findings indicate that Eg5 expression can be used as a biomarker of poor prognosis and as a novel therapeutic target for HCC.
Collapse
|
202
|
Kinesin-5-independent mitotic spindle assembly requires the antiparallel microtubule crosslinker Ase1 in fission yeast. Nat Commun 2017; 8:15286. [PMID: 28513584 PMCID: PMC5442317 DOI: 10.1038/ncomms15286] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 03/13/2017] [Indexed: 12/04/2022] Open
Abstract
Bipolar spindle assembly requires a balance of forces where kinesin-5 produces outward pushing forces to antagonize the inward pulling forces from kinesin-14 or dynein. Accordingly, Kinesin-5 inactivation results in force imbalance leading to monopolar spindle and chromosome segregation failure. In fission yeast, force balance is restored when both kinesin-5 Cut7 and kinesin-14 Pkl1 are deleted, restoring spindle bipolarity. Here we show that the cut7Δpkl1Δ spindle is fully competent for chromosome segregation independently of motor activity, except for kinesin-6 Klp9, which is required for anaphase spindle elongation. We demonstrate that cut7Δpkl1Δ spindle bipolarity requires the microtubule antiparallel bundler PRC1/Ase1 to recruit CLASP/Cls1 to stabilize microtubules. Brownian dynamics-kinetic Monte Carlo simulations show that Ase1 and Cls1 activity are sufficient for initial bipolar spindle formation. We conclude that pushing forces generated by microtubule polymerization are sufficient to promote spindle pole separation and the assembly of bipolar spindle in the absence of molecular motors. Bipolar spindle assembly requires a balance of kinesin 14 pulling and kinesin 5 pushing forces. Here, the authors show that in fission yeast, spindle formation can occur in the absence of kinesin 5 (Cut7) and 14 (Pkl1) but requires the microtubule-associated protein Ase1 for spindle bipolarity.
Collapse
|
203
|
Forth S, Kapoor TM. The mechanics of microtubule networks in cell division. J Cell Biol 2017; 216:1525-1531. [PMID: 28490474 PMCID: PMC5461028 DOI: 10.1083/jcb.201612064] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 03/13/2017] [Accepted: 04/18/2017] [Indexed: 11/23/2022] Open
Abstract
Forth and Kapoor review the mechanical properties of the spindle microtubule network during cell division. The primary goal of a dividing somatic cell is to accurately and equally segregate its genome into two new daughter cells. In eukaryotes, this process is performed by a self-organized structure called the mitotic spindle. It has long been appreciated that mechanical forces must be applied to chromosomes. At the same time, the network of microtubules in the spindle must be able to apply and sustain large forces to maintain spindle integrity. Here we consider recent efforts to measure forces generated within microtubule networks by ensembles of key proteins. New findings, such as length-dependent force generation, protein clustering by asymmetric friction, and entropic expansion forces will help advance models of force generation needed for spindle function and maintaining integrity.
Collapse
Affiliation(s)
- Scott Forth
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY 10065
| | - Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY 10065
| |
Collapse
|
204
|
Brouwers N, Mallol Martinez N, Vernos I. Role of Kif15 and its novel mitotic partner KBP in K-fiber dynamics and chromosome alignment. PLoS One 2017; 12:e0174819. [PMID: 28445502 PMCID: PMC5405935 DOI: 10.1371/journal.pone.0174819] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 03/15/2017] [Indexed: 11/26/2022] Open
Abstract
Faithful segregation of the genetic material during the cell cycle is key for the continuation of life. Central to this process is the assembly of a bipolar spindle that aligns the chromosomes and segregates them to the two daughter cells. Spindle bipolarity is strongly dependent on the activity of the homotetrameric kinesin Eg5. However, another kinesin, Kif15, also provides forces needed to separate the spindle poles during prometaphase and to maintain spindle bipolarity at metaphase. Here we identify KBP as a specific interaction partner of Kif15 in mitosis. We show that KBP promotes the localization of Kif15 to the spindle equator close to the chromosomes. Both Kif15 and KBP are required for the alignment of all the chromosomes to the metaphase plate and the assembly of stable kinetochore fibers of the correct length. Taken together our data uncover a novel role for Kif15 in complex with KBP during mitosis.
Collapse
Affiliation(s)
- Nathalie Brouwers
- Cell and Developmental Biology Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Nuria Mallol Martinez
- Cell and Developmental Biology Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Isabelle Vernos
- Cell and Developmental Biology Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluis Companys 23, Barcelona, Spain
- * E-mail:
| |
Collapse
|
205
|
Chen GY, Kang YJ, Gayek AS, Youyen W, Tüzel E, Ohi R, Hancock WO. Eg5 Inhibitors Have Contrasting Effects on Microtubule Stability and Metaphase Spindle Integrity. ACS Chem Biol 2017; 12:1038-1046. [PMID: 28165699 DOI: 10.1021/acschembio.6b01040] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To uncover their contrasting mechanisms, antimitotic drugs that inhibit Eg5 (kinesin-5) were analyzed in mixed-motor gliding assays of kinesin-1 and Eg5 motors in which Eg5 "braking" dominates motility. Loop-5 inhibitors (monastrol, STLC, ispinesib, and filanesib) increased gliding speeds, consistent with inducing a weak-binding state in Eg5, whereas BRD9876 slowed gliding, consistent with locking Eg5 in a rigor state. Biochemical and single-molecule assays demonstrated that BRD9876 acts as an ATP- and ADP-competitive inhibitor with 4 nM KI. Consistent with its microtubule polymerase activity, Eg5 was shown to stabilize microtubules against depolymerization. This stabilization activity was eliminated in monastrol but was enhanced by BRD9876. Finally, in metaphase-arrested RPE-1 cells, STLC promoted spindle collapse, whereas BRD9876 did not. Thus, different Eg5 inhibitors impact spindle assembly and architecture through contrasting mechanisms, and rigor inhibitors may paradoxically have the capacity to stabilize microtubule arrays in cells.
Collapse
Affiliation(s)
- Geng-Yuan Chen
- Department
of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - You Jung Kang
- Department
of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - A. Sophia Gayek
- Department
of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee 37203, United States
| | - Wiphu Youyen
- Department
of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, United States
| | - Erkan Tüzel
- Department
of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, United States
| | - Ryoma Ohi
- Department
of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee 37203, United States
| | - William O. Hancock
- Department
of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| |
Collapse
|
206
|
Spencer AK, Schaumberg AJ, Zallen JA. Scaling of cytoskeletal organization with cell size in Drosophila. Mol Biol Cell 2017; 28:1519-1529. [PMID: 28404752 PMCID: PMC5449150 DOI: 10.1091/mbc.e16-10-0691] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 03/31/2017] [Accepted: 04/05/2017] [Indexed: 11/11/2022] Open
Abstract
Actin-rich denticle precursors are regularly distributed in the Drosophila embryo. Cytoskeletal scaling occurs through changes in denticle number and spacing. Denticle spacing scales with cell length over a 10-fold range. Accurate denticle positioning requires the microtubule cytoskeleton. Spatially organized macromolecular complexes are essential for cell and tissue function, but the mechanisms that organize micron-scale structures within cells are not well understood. Microtubule-based structures such as mitotic spindles scale with cell size, but less is known about the scaling of actin structures within cells. Actin-rich denticle precursors cover the ventral surface of the Drosophila embryo and larva and provide templates for cuticular structures involved in larval locomotion. Using quantitative imaging and statistical modeling, we demonstrate that denticle number and spacing scale with cell length over a wide range of cell sizes in embryos and larvae. Denticle number and spacing are reduced under space-limited conditions, and both features robustly scale over a 10-fold increase in cell length during larval growth. We show that the relationship between cell length and denticle spacing can be recapitulated by specific mathematical equations in embryos and larvae and that accurate denticle spacing requires an intact microtubule network and the microtubule minus end–binding protein, Patronin. These results identify a novel mechanism of microtubule-dependent actin scaling that maintains precise patterns of actin organization during tissue growth.
Collapse
Affiliation(s)
- Alison K Spencer
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences.,Howard Hughes Medical Institute and Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Andrew J Schaumberg
- Weill Cornell Graduate School of Medical Sciences and the Tri-Institutional PhD Program in Computational Biology and Medicine, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Jennifer A Zallen
- Howard Hughes Medical Institute and Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| |
Collapse
|
207
|
Embedding dual function into molecular motors through collective motion. Sci Rep 2017; 7:44288. [PMID: 28281683 PMCID: PMC5345074 DOI: 10.1038/srep44288] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 02/06/2017] [Indexed: 12/26/2022] Open
Abstract
Protein motors, such as kinesins and dyneins, bind to a microtubule and travel along it in a specific direction. Previously, it was thought that the directionality for a given motor was constant in the absence of an external force. However, the directionality of the kinesin-5 Cin8 was recently found to change as the number of motors that bind to the same microtubule is increased. Here, we introduce a simple mechanical model of a microtubule-sliding assay in which multiple motors interact with the filament. We show that, due to the collective phenomenon, the directionality of the motor changes (e.g., from minus- to plus- end directionality), depending on the number of motors. This is induced by a large diffusive component in the directional walk and by the subsequent frustrated motor configuration, in which multiple motors pull the filament in opposite directions, similar to a game of tug-of-war. A possible role of the dual-directional motors for the mitotic spindle formation is also discussed. Our framework provides a general mechanism to embed two conflicting tasks into a single molecular machine, which works context-dependently.
Collapse
|
208
|
Asbury CL. Anaphase A: Disassembling Microtubules Move Chromosomes toward Spindle Poles. BIOLOGY 2017; 6:E15. [PMID: 28218660 PMCID: PMC5372008 DOI: 10.3390/biology6010015] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 02/04/2017] [Accepted: 02/10/2017] [Indexed: 11/16/2022]
Abstract
The separation of sister chromatids during anaphase is the culmination of mitosis and one of the most strikingly beautiful examples of cellular movement. It consists of two distinct processes: Anaphase A, the movement of chromosomes toward spindle poles via shortening of the connecting fibers, and anaphase B, separation of the two poles from one another via spindle elongation. I focus here on anaphase A chromosome-to-pole movement. The chapter begins by summarizing classical observations of chromosome movements, which support the current understanding of anaphase mechanisms. Live cell fluorescence microscopy studies showed that poleward chromosome movement is associated with disassembly of the kinetochore-attached microtubule fibers that link chromosomes to poles. Microtubule-marking techniques established that kinetochore-fiber disassembly often occurs through loss of tubulin subunits from the kinetochore-attached plus ends. In addition, kinetochore-fiber disassembly in many cells occurs partly through 'flux', where the microtubules flow continuously toward the poles and tubulin subunits are lost from minus ends. Molecular mechanistic models for how load-bearing attachments are maintained to disassembling microtubule ends, and how the forces are generated to drive these disassembly-coupled movements, are discussed.
Collapse
Affiliation(s)
- Charles L Asbury
- Department of Physiology & Biophysics, University of Washington, Seattle, WA 98195, USA.
| |
Collapse
|
209
|
Kapoor TM. Metaphase Spindle Assembly. BIOLOGY 2017; 6:biology6010008. [PMID: 28165376 PMCID: PMC5372001 DOI: 10.3390/biology6010008] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 01/17/2017] [Accepted: 01/19/2017] [Indexed: 01/31/2023]
Abstract
A microtubule-based bipolar spindle is required for error-free chromosome segregation during cell division. In this review I discuss the molecular mechanisms required for the assembly of this dynamic micrometer-scale structure in animal cells.
Collapse
Affiliation(s)
- Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, the Rockefeller University, New York, NY 10065, USA.
| |
Collapse
|
210
|
Shapira O, Goldstein A, Al-Bassam J, Gheber L. A potential physiological role for bi-directional motility and motor clustering of mitotic kinesin-5 Cin8 in yeast mitosis. J Cell Sci 2017; 130:725-734. [PMID: 28069834 DOI: 10.1242/jcs.195040] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 12/29/2016] [Indexed: 01/25/2023] Open
Abstract
The bipolar kinesin-5 Cin8 switches from minus- to plus-end-directed motility under various conditions in vitro The mechanism and physiological significance of this switch remain unknown. Here, we show that under high ionic strength conditions, Cin8 moves towards and concentrates in clusters at the minus ends of stable and dynamic microtubules. Clustering of Cin8 induces a switch from fast minus- to slow plus-end-directed motility and forms sites that capture antiparallel microtubules (MTs) and induces their sliding apart through plus-end-directed motility. In early mitotic cells with monopolar spindles, Cin8 localizes near the spindle poles at microtubule minus ends. This localization is dependent on the minus-end-directed motility of Cin8. In cells with assembled bipolar spindles, Cin8 is distributed along the spindle microtubules. We propose that minus-end-directed motility is required for Cin8 clustering near the spindle poles before spindle assembly. Cin8 clusters promote the capture of microtubules emanating from the neighboring spindle poles and mediate their antiparallel sliding. This activity is essential to maximize microtubule crosslinking before bipolar spindle assembly and to induce the initial separation of the spindle poles.
Collapse
Affiliation(s)
- Ofer Shapira
- Department of Chemistry and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Alina Goldstein
- Department of Chemistry and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Jawdat Al-Bassam
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA 95616, USA
| | - Larisa Gheber
- Department of Chemistry and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| |
Collapse
|
211
|
Olziersky AM, Labidi-Galy SI. Clinical Development of Anti-mitotic Drugs in Cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1002:125-152. [PMID: 28600785 DOI: 10.1007/978-3-319-57127-0_6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Mitosis is one of the most fundamental processes of life by which a mammalian cell divides into two daughter cells. Mitosis has been an attractive target for anticancer therapies since fast proliferation was identified as one of the hallmarks of cancer cells. Despite efforts into developing specific inhibitors for mitotic kinases and kinesins, very few drugs have shown the efficiency of microtubule targeting-agents in cancer cells with paclitaxel being the most successful. A deeper translational research accompanying clinical trials of anti-mitotic drugs will help in identifying potent biomarkers predictive for response. Here, we review the current knowledge of mitosis targeting agents that have been tested so far in the clinics.
Collapse
Affiliation(s)
- Anna-Maria Olziersky
- Department of Cell Physiology and Metabolism, Faculty of Medicine, Geneva University, Geneva, Switzerland
| | - S Intidhar Labidi-Galy
- Department of Oncology, Geneva University Hospitals, Rue Gabrielle Perret-Gentil 4, Geneva, 1205, Switzerland.
| |
Collapse
|
212
|
Akera T, Watanabe Y. The spindle assembly checkpoint promotes chromosome bi-orientation: A novel Mad1 role in chromosome alignment. Cell Cycle 2016; 15:493-7. [PMID: 26752263 DOI: 10.1080/15384101.2015.1128596] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Faithful chromosome segregation relies on dynamic interactions between spindle microtubules and chromosomes. Especially, all chromosomes must be aligned at the equator of the spindle to establish bi-orientation before they start to segregate. The spindle assembly checkpoint (SAC) monitors this process, inhibiting chromosome segregation until all chromosomes achieve bi-orientation. The original concept of 'checkpoints' was proposed as an external surveillance system that does not play an active role in the process it monitors. However, accumulating evidence from recent studies suggests that SAC components do play an active role in chromosome bi-orientation. In this review, we highlight a novel Mad1 role in chromosome alignment, which is the first conserved mechanism that links the SAC and kinesin-mediated chromosome gliding.
Collapse
Affiliation(s)
- Takashi Akera
- a Laboratory of Chromosome Dynamics, Institute of Molecular Cellular Biosciences, University of Tokyo , Tokyo , Japan
| | - Yoshinori Watanabe
- a Laboratory of Chromosome Dynamics, Institute of Molecular Cellular Biosciences, University of Tokyo , Tokyo , Japan
| |
Collapse
|
213
|
Scholey JM, Civelekoglu-Scholey G, Brust-Mascher I. Anaphase B. BIOLOGY 2016; 5:biology5040051. [PMID: 27941648 PMCID: PMC5192431 DOI: 10.3390/biology5040051] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 11/30/2016] [Accepted: 12/01/2016] [Indexed: 11/16/2022]
Abstract
Anaphase B spindle elongation is characterized by the sliding apart of overlapping antiparallel interpolar (ip) microtubules (MTs) as the two opposite spindle poles separate, pulling along disjoined sister chromatids, thereby contributing to chromosome segregation and the propagation of all cellular life. The major biochemical “modules” that cooperate to mediate pole–pole separation include: (i) midzone pushing or (ii) braking by MT crosslinkers, such as kinesin-5 motors, which facilitate or restrict the outward sliding of antiparallel interpolar MTs (ipMTs); (iii) cortical pulling by disassembling astral MTs (aMTs) and/or dynein motors that pull aMTs outwards; (iv) ipMT plus end dynamics, notably net polymerization; and (v) ipMT minus end depolymerization manifest as poleward flux. The differential combination of these modules in different cell types produces diversity in the anaphase B mechanism. Combinations of antagonist modules can create a force balance that maintains the dynamic pre-anaphase B spindle at constant length. Tipping such a force balance at anaphase B onset can initiate and control the rate of spindle elongation. The activities of the basic motor filament components of the anaphase B machinery are controlled by a network of non-motor MT-associated proteins (MAPs), for example the key MT cross-linker, Ase1p/PRC1, and various cell-cycle kinases, phosphatases, and proteases. This review focuses on the molecular mechanisms of anaphase B spindle elongation in eukaryotic cells and briefly mentions bacterial DNA segregation systems that operate by spindle elongation.
Collapse
Affiliation(s)
- Jonathan M Scholey
- Department of Molecular and Cell Biology, University of California, Davis, CA 95616, USA.
| | | | - Ingrid Brust-Mascher
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
| |
Collapse
|
214
|
Cooperation Between Kinesin Motors Promotes Spindle Symmetry and Chromosome Organization in Oocytes. Genetics 2016; 205:517-527. [PMID: 27932541 DOI: 10.1534/genetics.116.194647] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 11/29/2016] [Indexed: 11/18/2022] Open
Abstract
The oocyte spindle in most animal species is assembled in the absence of the microtubule-organizing centers called centrosomes. Without the organization provided by centrosomes, acentrosomal meiotic spindle organization may rely heavily on the bundling of microtubules by kinesin motor proteins. Indeed, the minus-end directed kinesin-14 NCD, and the plus-end directed kinesin-6 Subito are known to be required for oocyte spindle organization in Drosophila melanogaster How multiple microtubule-bundling kinesins interact to produce a functional acentrosomal spindle is not known. In addition, there have been few studies on the meiotic function of one of the most important microtubule-bundlers in mitotic cells, the kinesin-5 KLP61F. We have found that the kinesin-5 KLP61F is required for spindle and centromere symmetry in oocytes. The asymmetry observed in the absence of KLP61F depends on NCD, the kinesin-12 KLP54D, and the microcephaly protein ASP. In contrast, KLP61F and Subito work together in maintaining a bipolar spindle. We propose that the prominent central spindle, stabilized by Subito, provides the framework for the coordination of multiple microtubule-bundling activities. The activities of several proteins, including NCD, KLP54D, and ASP, generate asymmetries within the acentrosomal spindle, while KLP61F and Subito balance these forces, resulting in the capacity to accurately segregate chromosomes.
Collapse
|
215
|
Müller K, Klein PM, Heissig P, Roidl A, Wagner E. EGF receptor targeted lipo-oligocation polyplexes for antitumoral siRNA and miRNA delivery. NANOTECHNOLOGY 2016; 27:464001. [PMID: 27736810 DOI: 10.1088/0957-4484/27/46/464001] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Antitumoral siRNA and miRNA delivery was demonstrated by epidermal growth factor receptor (EGFR) targeted oligoaminoamide polyplexes. For this purpose, the T-shaped lipo-oligomer 454 was used to complex RNA into a core polyplex, which was subsequently functionalized with the targeting peptide ligand GE11 via a polyethylene glycol (PEG) linker. To this end, free cysteines on the surface of 454 polyplex were coupled with a maleimide-PEG-GE11 reagent (Mal-GE11). Resulting particles with sizes of 120-150 nm showed receptor-mediated uptake into EGFR-positive T24 bladder cancer cells, MDA-MB 231 breast cancer cells and Huh7 liver cancer cells. Furthermore, these formulations led to ligand-dependent gene silencing. RNA interference (RNAi) triggered antitumoral effects were observed for two different therapeutic RNAs, a miRNA-200c mimic or EG5 siRNA. Using polyplexes modified with a ratio of 0.8 molar equivalents of Mal-GE11, treatment of T24 or MDA-MB 231 cancer cells with miR-200c led to the expected decreased proliferation and migration, changes in cell cycle and enhanced sensitivity towards doxorubicin. Delivery of EG5 siRNA into Huh7 cells resulted in antitumoral activity with G2/M arrest, triggered by loss of mitotic spindle separation and formation of mono-astral spindles. These findings demonstrate the potential of GE11 ligand-containing RNAi polyplexes for cancer treatment.
Collapse
Affiliation(s)
- Katharina Müller
- Pharmaceutical Biotechnology, Center for System-based Drug Research, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, D-81377 Munich, Germany
| | | | | | | | | |
Collapse
|
216
|
Mann BJ, Balchand SK, Wadsworth P. Regulation of Kif15 localization and motility by the C-terminus of TPX2 and microtubule dynamics. Mol Biol Cell 2016; 28:65-75. [PMID: 27852894 PMCID: PMC5221630 DOI: 10.1091/mbc.e16-06-0476] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 11/04/2016] [Accepted: 11/07/2016] [Indexed: 12/31/2022] Open
Abstract
Mitotic motor proteins generate force to establish and maintain spindle bipolarity, but how they are temporally and spatially regulated in vivo is unclear. Prior work demonstrated that a microtubule-associated protein, TPX2, targets kinesin-5 and kinesin-12 motors to spindle microtubules. The C-terminal domain of TPX2 contributes to the localization and motility of the kinesin-5, Eg5, but it is not known whether this domain regulates kinesin-12, Kif15. We found that the C-terminal domain of TPX2 contributes to the localization of Kif15 to spindle microtubules in cells and suppresses motor walking in vitro. Kif15 and Eg5 are partially redundant motors, and overexpressed Kif15 can drive spindle formation in the absence of Eg5 activity. Kif15-dependent bipolar spindle formation in vivo requires the C-terminal domain of TPX2. In the spindle, fluorescent puncta of GFP-Kif15 move toward the equatorial region at a rate equivalent to microtubule growth. Reduction of microtubule growth with paclitaxel suppresses GFP-Kif15 motility, demonstrating that dynamic microtubules contribute to Kif15 behavior. Our results show that the C-terminal region of TPX2 regulates Kif15 in vitro, contributes to motor localization in cells, and is required for Kif15 force generation in vivo and further reveal that dynamic microtubules contribute to Kif15 behavior in vivo.
Collapse
Affiliation(s)
- Barbara J Mann
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003
| | - Sai K Balchand
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003
| | - Patricia Wadsworth
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003
| |
Collapse
|
217
|
Schizosaccharomyces pombe kinesin-5 switches direction using a steric blocking mechanism. Proc Natl Acad Sci U S A 2016; 113:E7483-E7489. [PMID: 27834216 DOI: 10.1073/pnas.1611581113] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Cut7, the sole kinesin-5 in Schizosaccharomyces pombe, is essential for mitosis. Like other yeast kinesin-5 motors, Cut7 can reverse its stepping direction, by mechanisms that are currently unclear. Here we show that for full-length Cut7, the key determinant of stepping direction is the degree of motor crowding on the microtubule lattice, with greater crowding converting the motor from minus end-directed to plus end-directed stepping. To explain how high Cut7 occupancy causes this reversal, we postulate a simple proximity sensing mechanism that operates via steric blocking. We propose that the minus end-directed stepping action of Cut7 is selectively inhibited by collisions with neighbors under crowded conditions, whereas its plus end-directed action, being less space-hungry, is not. In support of this idea, we show that the direction of Cut7-driven microtubule sliding can be reversed by crowding it with non-Cut7 proteins. Thus, crowding by either dynein microtubule binding domain or Klp2, a kinesin-14, converts Cut7 from net minus end-directed to net plus end-directed stepping. Biochemical assays confirm that the Cut7 N terminus increases Cut7 occupancy by binding directly to microtubules. Direct observation by cryoEM reveals that this occupancy-enhancing N-terminal domain is partially ordered. Overall, our data point to a steric blocking mechanism for directional reversal through which collisions of Cut7 motor domains with their neighbors inhibit their minus end-directed stepping action, but not their plus end-directed stepping action. Our model can potentially reconcile a number of previous, apparently conflicting, observations and proposals for the reversal mechanism of yeast kinesins-5.
Collapse
|
218
|
Kinesin-5 Contributes to Spindle-length Scaling in the Evolution of Cancer toward Metastasis. Sci Rep 2016; 6:35767. [PMID: 27767194 PMCID: PMC5073351 DOI: 10.1038/srep35767] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 10/05/2016] [Indexed: 01/03/2023] Open
Abstract
During natural evolution, the spindles often scale with cell sizes to orchestrate accurate chromosome segregation. Whether in cancer evolution, when the constraints on genome integrity are relaxed, cancer cells may evolve the spindle to confer other advantages has not been investigated. Using invasion as a selective pressure in vitro, we found that a highly metastatic cancer clone displays a lengthened metaphase spindle, with faster spindle elongation that correlates with transiently elevated speed of cell migration. We found that kinesin-5 is upregulated in this malignant clone, and weak inhibition of kinesin-5 activity could revert the spindle to a smaller aspect ratio, decrease the speed of spindle pole separation, and suppress post-mitotic cell migration. A correlation was found between high aspect ratio and strong metastatic potential in cancers that evolved and were selected in vivo, implicating that the spindle aspect ratio could serve as a promising cellular biomarker for metastatic cancer clones.
Collapse
|
219
|
van Ree JH, Nam HJ, van Deursen JM. Mitotic kinase cascades orchestrating timely disjunction and movement of centrosomes maintain chromosomal stability and prevent cancer. Chromosome Res 2016; 24:67-76. [PMID: 26615533 DOI: 10.1007/s10577-015-9501-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Centrosomes are microtubule-organizing centers that duplicate in S phase to form bipolar spindles that separate duplicated chromosomes faithfully into two daughter cells during cell division. Recent studies show that proper timing of centrosome dynamics, the disjunction and movement of centrosomes, is tightly linked to spindle symmetry, correct microtubule-kinetochore attachment, and chromosome segregation. Here, we review mechanisms that regulate centrosome dynamics, with emphasis on the roles of key mitotic kinases in the proper timing of centrosome dynamics and how aberrancies in these processes may cause chromosomal instability and cancer.
Collapse
Affiliation(s)
- Janine H van Ree
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
| | - Hyun-Ja Nam
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
| | - Jan M van Deursen
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA. .,Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA.
| |
Collapse
|
220
|
A Force-Induced Directional Switch of a Molecular Motor Enables Parallel Microtubule Bundle Formation. Cell 2016; 167:539-552.e14. [DOI: 10.1016/j.cell.2016.09.029] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 06/25/2016] [Accepted: 09/12/2016] [Indexed: 12/17/2022]
|
221
|
Kim K, Sikora A, Nakazawa H, Umetsu M, Hwang W, Teizer W. Isomorphic coalescence of aster cores formed in vitro from microtubules and kinesin motors. Phys Biol 2016; 13:056002. [PMID: 27652512 DOI: 10.1088/1478-3975/13/5/056002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We report fluorescence microscopy studies of the formation of aster-like structures emerging from a cellular element-based active system and a novel analysis of the aster condensation. The system consists of rhodamine labeled microtubules which are dynamically coupled by functionalized kinesin motor proteins cross-linked via streptavidin-coated quantum dots (QDs). The aster-shaped objects contain core structures. The cores are aggregates of the QD-motor protein complexes, and result from the dynamic condensation of sub-clusters that are connected to each other randomly. The structural specificity of the aster core reflects a configuration of the initial connectivity between sub-clusters. Detailed image analysis allows us to extract a novel correlation between the condensation speed and the sub-cluster separation. The size of the core is scaled down during the condensation process, following a power law dependence on the distance between sub-clusters. The exponent of the power law is close to two, as expected from a geometric model. This single exponent common to all the contractile lines implies that there exists a time regime during which an isomorphic contraction of the aster core continues during the condensation process. We analyze the observed contraction by using a model system with potential applicability in a wide range of emergent phenomena in randomly coupled active networks, which are prevalent in the cellular environment.
Collapse
Affiliation(s)
- K Kim
- WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Japan
| | | | | | | | | | | |
Collapse
|
222
|
Möckel MM, Hund C, Mayer TU. Chemical Genetics Approach to Engineer Kinesins with Sensitivity towards a Small-Molecule Inhibitor of Eg5. Chembiochem 2016; 17:2042-2045. [PMID: 27550380 DOI: 10.1002/cbic.201600451] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Indexed: 12/14/2022]
Abstract
Due to their fast and often reversible mode of action, small molecules are ideally suited to dissect biological processes. Yet, the validity of small-molecule studies is intimately tied to the specificity of the applied compounds, thus imposing a great challenge to screens for novel inhibitors. Here, we applied a chemical-genetics approach to render kinesin motor proteins sensitive to inhibition by the well-characterized small molecule S-Trityl-l-cysteine (STLC). STLC specifically inhibits the kinesin Eg5 through binding to a known allosteric site within the motor domain. Transfer of this allosteric binding site into the motor domain of the human kinesins Kif3A and Kif4A sensitizes them towards STLC. Single-molecule microscopy analyses confirmed that STLC inhibits the movement of chimeric but not wild-type Kif4A along microtubules. Thus, our proof-of-concept study revealed that this chemical-genetic approach provides a powerful strategy to specifically inhibit kinesins in vitro for which small-molecule inhibitors are not yet available.
Collapse
Affiliation(s)
- Martin M Möckel
- Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany
| | - Corinna Hund
- Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany.,FGen GmbH, Hochbergerstrasse 60C, 4057, Basel, Switzerland
| | - Thomas U Mayer
- Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany.
| |
Collapse
|
223
|
Duan Y, Huo D, Gao J, Wu H, Ye Z, Liu Z, Zhang K, Shan L, Zhou X, Wang Y, Su D, Ding X, Shi L, Wang Y, Shang Y, Xuan C. Ubiquitin ligase RNF20/40 facilitates spindle assembly and promotes breast carcinogenesis through stabilizing motor protein Eg5. Nat Commun 2016; 7:12648. [PMID: 27557628 PMCID: PMC5007379 DOI: 10.1038/ncomms12648] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 07/19/2016] [Indexed: 12/30/2022] Open
Abstract
Whether transcriptional regulators are functionally involved in mitosis is a fundamental question in cell biology. Here we report that the RNF20/40 complex, a major ubiquitin ligase catalysing histone H2B monoubiquitination, interacts with the motor protein Eg5 during mitosis and participates in spindle assembly. We show that the RNF20/40 complex monoubiquitinates and stabilizes Eg5. Loss of RNF20/40 results in spindle assembly defects, cell cycle arrest and apoptosis. Consistently, depletion of either RNF20/40 or Eg5 suppresses breast cancer in vivo. Significantly, RNF20/40 and Eg5 are concurrently upregulated in human breast carcinomas and high Eg5 expression is associated with poorer overall survival of patients with luminal A, or B, breast cancer. Our study uncovers an important spindle assembly role of the RNF20/40 complex, and implicates the RNF20/40-Eg5 axis in breast carcinogenesis, supporting the pursuit of these proteins as potential targets for breast cancer therapeutic interventions. Eg5 has a role in spindle assembly and has been associated with tumorigenesis but it is not clear how its activity is regulated. Here, the authors show that the E3 ligase RNF20/40 regulates mitotic spindle assembly by regulating the stability of Eg5 through mono-ubiquitination of K745.
Collapse
Affiliation(s)
- Yang Duan
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Dawei Huo
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Jie Gao
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Heng Wu
- Tianjin Key Laboratory of Lung Cancer Metastasis and Tumour Microenvironment, Tianjin Lung Cancer Institute, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Zheng Ye
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Zhe Liu
- Department of Immunology, Tianjin Medical University, Tianjin 300070, China
| | - Kai Zhang
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Lin Shan
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Xing Zhou
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Yue Wang
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Dongxue Su
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Xiang Ding
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Lei Shi
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Yan Wang
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| | - Yongfeng Shang
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China.,Department of Biochemistry and Molecular Biology, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Peking University Health Science Center, Beijing 100191, China
| | - Chenghao Xuan
- Department of Biochemistry and Molecular Biology, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin 300070, China
| |
Collapse
|
224
|
Zheng Z, Wang J, Chen P, Xie M, Zhang L, Hou Y, Zhang X, Jiang J, Wang J, Lu Q, Liang G. Using L-STM to directly visualize enzymatic self-assembly/disassembly of nanofibers. NANOSCALE 2016; 8:15142-15146. [PMID: 27492656 DOI: 10.1039/c6nr03056d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Self-assembly/disassembly is ubiquitous in nature and plays an important role in many biological events. But noninvasive characterization of this process in real time at molecular resolution remains challenging. Herein, using homebuilt liquid-phase scanning tunneling microscopy (L-STM) with ultrahigh stability, we directly visualized enzymatic self-assembly/disassembly of oligopeptide nanofibers in real time for the first time. Static high-resolution L-STM images clearly showed the molecular packing details in the supramolecular nanofiber and the diameter of the nanofiber was consistent with that of cryo transmission electron microscopy (cryo-TEM) observations. Moreover, the self-repairing behavior of the supramolecular nanofibers was also directly observed at high resolution for the first time. This work unprecedentedly revealed new insights into Nature-mimic self-assembly and disassembly at the molecular level. It also illustrates the potential of our homebuilt L-STM in studying delicate biological processes in physiological solution with high resolution.
Collapse
Affiliation(s)
- Zhen Zheng
- High Magnetic Field Laboratory, Hefei Science Center, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui, China. and CAS Key Laboratory of Soft Matter Chemistry, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jihao Wang
- High Magnetic Field Laboratory, Hefei Science Center, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui, China. and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Peiyao Chen
- High Magnetic Field Laboratory, Hefei Science Center, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui, China. and CAS Key Laboratory of Soft Matter Chemistry, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Maolin Xie
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Lei Zhang
- High Magnetic Field Laboratory, Hefei Science Center, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui, China.
| | - Yubin Hou
- High Magnetic Field Laboratory, Hefei Science Center, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui, China.
| | - Xin Zhang
- High Magnetic Field Laboratory, Hefei Science Center, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui, China.
| | - Jun Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China and Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Junfeng Wang
- High Magnetic Field Laboratory, Hefei Science Center, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui, China.
| | - Qingyou Lu
- High Magnetic Field Laboratory, Hefei Science Center, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui, China. and CAS Key Laboratory of Soft Matter Chemistry, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, Jiangsu 210093, China
| | - Gaolin Liang
- High Magnetic Field Laboratory, Hefei Science Center, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui, China. and CAS Key Laboratory of Soft Matter Chemistry, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China
| |
Collapse
|
225
|
Vleugel M, Roth S, Groenendijk CF, Dogterom M. Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets. J Vis Exp 2016. [PMID: 27584979 DOI: 10.3791/54278] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Mitotic spindle assembly, positioning and orientation depend on the combined forces generated by microtubule dynamics, microtubule motor proteins and cross-linkers. Growing microtubules can generate pushing forces, while depolymerizing microtubules can convert the energy from microtubule shrinkage into pulling forces, when attached, for example, to cortical dynein or chromosomes. In addition, motor proteins and diffusible cross-linkers within the spindle contribute to spindle architecture by connecting and sliding anti-parallel microtubules. In vivo, it has proven difficult to unravel the relative contribution of individual players to the overall balance of forces. Here we present the methods that we recently developed in our efforts to reconstitute basic mitotic spindles bottom-up in vitro. Using microfluidic techniques, centrosomes and tubulin are encapsulated in water-in-oil emulsion droplets, leading to the formation of geometrically confined (double) microtubule asters. By additionally introducing cortically anchored dynein, plus-end directed microtubule motors and diffusible cross-linkers, this system is used to reconstitute spindle-like structures. The methods presented here provide a starting point for reconstitution of more complete mitotic spindles, allowing for a detailed study of the contribution of each individual component, and for obtaining an integrated quantitative view of the force-balance within the mitotic spindle.
Collapse
Affiliation(s)
- Mathijs Vleugel
- Department of Bionanoscience, Delft University of Technology
| | - Sophie Roth
- Department of Bionanoscience, Delft University of Technology
| | | | | |
Collapse
|
226
|
PTEN regulates EG5 to control spindle architecture and chromosome congression during mitosis. Nat Commun 2016; 7:12355. [PMID: 27492783 PMCID: PMC4980451 DOI: 10.1038/ncomms12355] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Accepted: 06/24/2016] [Indexed: 02/07/2023] Open
Abstract
Architectural integrity of the mitotic spindle is required for efficient chromosome congression and accurate chromosome segregation to ensure mitotic fidelity. Tumour suppressor PTEN has multiple functions in maintaining genome stability. Here we report an essential role of PTEN in mitosis through regulation of the mitotic kinesin motor EG5 for proper spindle architecture and chromosome congression. PTEN depletion results in chromosome misalignment in metaphase, often leading to catastrophic mitotic failure. In addition, metaphase cells lacking PTEN exhibit defects of spindle geometry, manifested prominently by shorter spindles. PTEN is associated and co-localized with EG5 during mitosis. PTEN deficiency induces aberrant EG5 phosphorylation and abrogates EG5 recruitment to the mitotic spindle apparatus, leading to spindle disorganization. These data demonstrate the functional interplay between PTEN and EG5 in controlling mitotic spindle structure and chromosome behaviour during mitosis. We propose that PTEN functions to equilibrate mitotic phosphorylation for proper spindle formation and faithful genomic transmission. One of the cellular functions of the tumour suppressor PTEN is to maintain genome stability. Here, the authors show that PTEN depletion leads to mitotic spindle shortening and chromosome misalignment due to aberrant EG5 activation.
Collapse
|
227
|
Tang Q, Billington N, Krementsova EB, Bookwalter CS, Lord M, Trybus KM. A single-headed fission yeast myosin V transports actin in a tropomyosin-dependent manner. J Cell Biol 2016; 214:167-79. [PMID: 27432898 PMCID: PMC4949448 DOI: 10.1083/jcb.201511102] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 06/15/2016] [Indexed: 12/20/2022] Open
Abstract
Myo51, a class V myosin in fission yeast, localizes to and assists in the assembly of the contractile ring, a conserved eukaryotic actomyosin structure that facilitates cytokinesis. Rng8 and Rng9 are binding partners that dictate the cellular localization and function of Myo51. Myo51 was expressed in insect cells in the presence or absence of Rng8/9. Surprisingly, electron microscopy of negatively stained images and hydrodynamic measurements showed that Myo51 is single headed, unlike most class V myosins. When Myo51-Rng8/9 was bound to actin-tropomyosin, two attachment sites were observed: the typical ATP-dependent motor domain attachment and a novel ATP-independent binding of the tail mediated by Rng8/9. A modified motility assay showed that this additional binding site anchors Myo51-Rng8/9 so that it can cross-link and slide actin-tropomyosin filaments relative to one another, functions that may explain the role of this motor in contractile ring assembly.
Collapse
Affiliation(s)
- Qing Tang
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405
| | - Neil Billington
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Elena B Krementsova
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405
| | - Carol S Bookwalter
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405
| | - Matthew Lord
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405
| | - Kathleen M Trybus
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405
| |
Collapse
|
228
|
Chen GY, Mickolajczyk KJ, Hancock WO. The Kinesin-5 Chemomechanical Cycle Is Dominated by a Two-heads-bound State. J Biol Chem 2016; 291:20283-20294. [PMID: 27402829 DOI: 10.1074/jbc.m116.730697] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Indexed: 12/29/2022] Open
Abstract
Single-molecule microscopy and stopped-flow kinetics assays were carried out to understand the microtubule polymerase activity of kinesin-5 (Eg5). Four lines of evidence argue that the motor primarily resides in a two-heads-bound (2HB) state. First, upon microtubule binding, dimeric Eg5 releases both bound ADPs. Second, microtubule dissociation in saturating ADP is 20-fold slower for the dimer than for the monomer. Third, ATP-triggered mant-ADP release is 5-fold faster than the stepping rate. Fourth, ATP binding is relatively fast when the motor is locked in a 2HB state. Shortening the neck-linker does not facilitate rear-head detachment, suggesting a minimal role for rear-head-gating. This 2HB state may enable Eg5 to stabilize incoming tubulin at the growing microtubule plus-end. The finding that slowly hydrolyzable ATP analogs trigger slower nucleotide release than ATP suggests that ATP hydrolysis in the bound head precedes stepping by the tethered head, leading to a mechanochemical cycle in which processivity is determined by the race between unbinding of the bound head and attachment of the tethered head.
Collapse
Affiliation(s)
- Geng-Yuan Chen
- From the Department of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Keith J Mickolajczyk
- From the Department of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802
| | - William O Hancock
- From the Department of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802
| |
Collapse
|
229
|
Affiliation(s)
- Nenad Pavin
- Department of Physics, Faculty of Science, University of Zagreb, 10000 Zagreb, Croatia;
| | - Iva M. Tolić
- Division of Molecular Biology, Ruđer Bošković Institute, 10000 Zagreb, Croatia;
| |
Collapse
|
230
|
van Heesbeen RGHP, Raaijmakers JA, Tanenbaum ME, Halim VA, Lelieveld D, Lieftink C, Heck AJR, Egan DA, Medema RH. Aurora A, MCAK, and Kif18b promote Eg5-independent spindle formation. Chromosoma 2016; 126:473-486. [PMID: 27354041 PMCID: PMC5509784 DOI: 10.1007/s00412-016-0607-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 06/19/2016] [Accepted: 06/21/2016] [Indexed: 11/28/2022]
Abstract
Inhibition of the microtubule (MT) motor protein Eg5 results in a mitotic arrest due to the formation of monopolar spindles, making Eg5 an attractive target for anti-cancer therapies. However, Eg5-independent pathways for bipolar spindle formation exist, which might promote resistance to treatment with Eg5 inhibitors. To identify essential components for Eg5-independent bipolar spindle formation, we performed a genome-wide siRNA screen in Eg5-independent cells (EICs). We find that the kinase Aurora A and two kinesins, MCAK and Kif18b, are essential for bipolar spindle assembly in EICs and in cells with reduced Eg5 activity. Aurora A promotes bipolar spindle assembly by phosphorylating Kif15, hereby promoting Kif15 localization to the spindle. In turn, MCAK and Kif18b promote bipolar spindle assembly by destabilizing the astral MTs. One attractive way to interpret our data is that, in the absence of MCAK and Kif18b, excessive astral MTs generate inward pushing forces on centrosomes at the cortex that inhibit centrosome separation. Together, these data suggest a novel function for astral MTs in force generation on spindle poles and how proteins involved in regulating microtubule length can contribute to bipolar spindle assembly.
Collapse
Affiliation(s)
| | - Jonne A Raaijmakers
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Marvin E Tanenbaum
- Hubrecht Institute, The Royal Netherlands Academy of Arts and Sciences (KNAW) and University Medical Center Utrecht, Utrecht, the Netherlands
| | - Vincentius A Halim
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.,Biomolecular Mass Spectrometry and Proteomics Group, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands
| | - Daphne Lelieveld
- Cell Screening Core, Department of Cell Biology, Center for Molecular Medicine, University Medical Centre, Utrecht, The Netherlands
| | - Cor Lieftink
- Division of Molecular Carcinogenesis, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics Group, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands
| | - David A Egan
- Cell Screening Core, Department of Cell Biology, Center for Molecular Medicine, University Medical Centre, Utrecht, The Netherlands
| | - René H Medema
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
| |
Collapse
|
231
|
McNally KP, Panzica MT, Kim T, Cortes DB, McNally FJ. A novel chromosome segregation mechanism during female meiosis. Mol Biol Cell 2016; 27:2576-89. [PMID: 27335123 PMCID: PMC4985259 DOI: 10.1091/mbc.e16-05-0331] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 06/14/2016] [Indexed: 01/28/2023] Open
Abstract
During conventional anaphase A, chromosomes move outward toward spindle poles. Caenorhabditis elegans meiotic spindle poles move inward toward chromosomes to achieve the same end. In a wide range of eukaryotes, chromosome segregation occurs through anaphase A, in which chromosomes move toward stationary spindle poles, anaphase B, in which chromosomes move at the same velocity as outwardly moving spindle poles, or both. In contrast, Caenorhabditis elegans female meiotic spindles initially shorten in the pole-to-pole axis such that spindle poles contact the outer kinetochore before the start of anaphase chromosome separation. Once the spindle pole-to-kinetochore contact has been made, the homologues of a 4-μm-long bivalent begin to separate. The spindle shortens an additional 0.5 μm until the chromosomes are embedded in the spindle poles. Chromosomes then separate at the same velocity as the spindle poles in an anaphase B–like movement. We conclude that the majority of meiotic chromosome movement is caused by shortening of the spindle to bring poles in contact with the chromosomes, followed by separation of chromosome-bound poles by outward sliding.
Collapse
Affiliation(s)
- Karen Perry McNally
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
| | - Michelle T Panzica
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
| | - Taekyung Kim
- Ludwig Institute for Cancer Research, San Diego, CA 92093 Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Daniel B Cortes
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
| | - Francis J McNally
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
| |
Collapse
|
232
|
CDK-1 Inhibition in G2 Stabilizes Kinetochore-Microtubules in the following Mitosis. PLoS One 2016; 11:e0157491. [PMID: 27281342 PMCID: PMC4900577 DOI: 10.1371/journal.pone.0157491] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 05/30/2016] [Indexed: 11/18/2022] Open
Abstract
Cell proliferation is driven by cyclical activation of cyclin-dependent kinases (CDKs), which produce distinct biochemical cell cycle phases. Mitosis (M phase) is orchestrated by CDK-1, complexed with mitotic cyclins. During M phase, chromosomes are segregated by a bipolar array of microtubules called the mitotic spindle. The essential bipolarity of the mitotic spindle is established by the kinesin-5 Eg5, but factors influencing the maintenance of spindle bipolarity are not fully understood. Here, we describe an unexpected link between inhibiting CDK-1 before mitosis and bipolar spindle maintenance. Spindles in human RPE-1 cells normally collapse to monopolar structures when Eg5 is inhibited at metaphase. However, we found that inhibition of CDK-1 in the G2 phase of the cell cycle improved the ability of RPE-1 cells to maintain spindle bipolarity without Eg5 activity in the mitosis immediately after release from CDK-1 inhibition. This improved bipolarity maintenance correlated with an increase in the stability of kinetochore-microtubules, the subset of microtubules that link chromosomes to the spindle. The improvement in bipolarity maintenance after CDK-1 inhibition in G2 required both the kinesin-12 Kif15 and increased stability of kinetochore-microtubules. Consistent with increased kinetochore-microtubule stability, we find that inhibition of CDK-1 in G2 impairs mitotic fidelity by increasing the incidence of lagging chromosomes in anaphase. These results suggest that inhibition of CDK-1 in G2 causes unpredicted effects in mitosis, even after CDK-1 inhibition is relieved.
Collapse
|
233
|
Silkova OG, Loginova DB. Sister chromatid separation and monopolar spindle organization in the first meiosis as two mechanisms of unreduced gametes formation in wheat-rye hybrids. PLANT REPRODUCTION 2016; 29:199-213. [PMID: 26994004 PMCID: PMC4909807 DOI: 10.1007/s00497-016-0279-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 03/02/2016] [Indexed: 05/20/2023]
Abstract
KEY MESSAGE Unreduced gametes. The absence of a strict pachytene checkpoint in plants presents an opportunity to study meiosis in polyhaploid organisms. In the present study, we demonstrate that meiosis is coordinated in hybrids between disomic wheat-rye substitution lines 1Rv(1A), 2R(2D), 5R(5D), 6R(6A) and rye (Triticum aestivum L. × Secale cereale L., 4x = 28, ABDR). By using in situ hybridization with a centromere pAet6-09 probe and immunostaining with H3Ser10ph-, CENH3-, and α-tubulin-specific antibodies, we distinguished four chromosome behaviour types. The first one is a mitotic-like division that is characterized by mitotic centromere architecture, robust bipolar spindle, one-step loss of arm and centromere cohesion, and sister chromatid separation in the first and only meiotic division. The second type involves a monopolar spindle formation, which appears as a hat-shaped group of chromosomes moving in one direction, wherein MT bundles are co-oriented polewards. It prevents chromosome segregation in meiosis I, with a bipolar spindle distributing sister chromatids to the poles in meiosis II. These events subsequently result in the formation of unreduced microspores. The other two meiotic-like chromosome segregation patterns known as reductional and equational plus reductional represent stand-alone types of cell division rather than intermediate steps of meiosis I. Only sterile pollen is produced as a result of such meiotic-like chromosome behaviours. Slightly variable meiotic phenotypes are reproducibly observed in hybrids under different growth conditions. The 2R(2D)xR genotype tends to promote reductional division. In contrast, the genotypes 1Rv(1A)xR, 5R(5D)xR, and 6R(6A)xR promote equational chromosome segregation and monopolar spindle formation in addition to reductional and equational plus reductional division types.
Collapse
Affiliation(s)
- O G Silkova
- Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Lavrentiev Ave. 10, Novosibirsk, 630090, Russia.
| | - D B Loginova
- Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Lavrentiev Ave. 10, Novosibirsk, 630090, Russia
| |
Collapse
|
234
|
Shapira O, Gheber L. Motile properties of the bi-directional kinesin-5 Cin8 are affected by phosphorylation in its motor domain. Sci Rep 2016; 6:25597. [PMID: 27216310 PMCID: PMC4877575 DOI: 10.1038/srep25597] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 04/20/2016] [Indexed: 12/25/2022] Open
Abstract
The Saccharomyces cerevisiae kinesin-5 Cin8 performs essential mitotic functions in spindle assembly and anaphase B spindle elongation. Recent work has shown that Cin8 is a bi-directional motor which moves towards the minus-end of microtubules (MTs) under high ionic strength (IS) conditions and changes directionality in low IS conditions and when bound between anti-parallel microtubules. Previous work from our laboratory has also indicated that Cin8 is differentially phosphorylated during late anaphase at cyclin-dependent kinase 1 (Cdk1)-specific sites located in its motor domain. In vivo, such phosphorylation causes Cin8 detachment from spindles and reduces the spindle elongation rate, while maintaining proper spindle morphology. To study the effect of phosphorylation on Cin8 motor function, we examined in vitro motile properties of wild type Cin8, as well as its phosphorylation using phospho-deficient and phospho-mimic variants, in a single molecule fluorescence motility assay. Analysis was performed on whole cell extracts and on purified Cin8 samples. We found that addition of negative charges in the phospho-mimic mutant weakened the MT-motor interaction, increased motor velocity and promoted minus-end-directed motility. These results indicate that phosphorylation in the catalytic domain of Cin8 regulates its motor function.
Collapse
Affiliation(s)
- Ofer Shapira
- Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Larisa Gheber
- Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| |
Collapse
|
235
|
Abstract
Life depends on cell proliferation and the accurate segregation of chromosomes, which are mediated by the microtubule (MT)-based mitotic spindle and ∼200 essential MT-associated proteins. Yet, a mechanistic understanding of how the mitotic spindle is assembled and achieves chromosome segregation is still missing. This is mostly due to the density of MTs in the spindle, which presumably precludes their direct observation. Recent insight has been gained into the molecular building plan of the metaphase spindle using bulk and single-molecule measurements combined with computational modeling. MT nucleation was uncovered as a key principle of spindle assembly, and mechanistic details about MT nucleation pathways and their coordination are starting to be revealed. Lastly, advances in studying spindle assembly can be applied to address the molecular mechanisms of how the spindle segregates chromosomes.
Collapse
Affiliation(s)
- Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544-1014;
| |
Collapse
|
236
|
Bullerdiek J, Dotzauer A, Bauer I. The mitotic spindle: linking teratogenic effects of Zika virus with human genetics? Mol Cytogenet 2016; 9:32. [PMID: 27099632 PMCID: PMC4837584 DOI: 10.1186/s13039-016-0240-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 04/01/2016] [Indexed: 11/10/2022] Open
Abstract
Background Recently, an association between Zika virus infection and microcephaly/ocular findings was found to be reasonable e.g. because of the demonstration that the virus was found in the brain of a fetus after presumed maternal infection. Although there is no proof yet for a causal relationship, for an appropriate risk calculation efforts are urgently needed to either establish or disprove this assumption. Presentation of the hypothesis On the basis of inherited syndromes combining microcephaly with ocular findings similar to those associated with Zika infections, we have hypothesized that the impairment of the proper function of the mitotic apparatus is a possible mechanism by which Zika can exert teratogenic effects. Testing the hypothesis A bundle of well-known cytogenetic and molecular-cytogenetic methods (e.g. formation of micronuclei, chromosomal lagging, immunofluorescence of centrosomes) to evaluate proper function, maintenance, and establishment of the mitotic spindle poles can be applied on infected cells. Also, the viral proteins can be tested for their possible interaction with proteins encoded by genes involved in inherited syndromes with microcephaly and ocular findings resembling those in presumed cases of intrauterine ZIKV infection. Implications of the hypothesis Once proved, this hypothesis allows for a targeted approach into mechanisms of possible relevance as e.g. if different strains of the virus are implicated in the teratogenic effects to the same or a different extent.
Collapse
Affiliation(s)
- Joern Bullerdiek
- Centre for Human Genetics, University of Bremen, Leobener Str. ZHG, D-28359 Bremen, Germany ; Institute of Medical Genetics, University Rostock Medical Center, Ernst-Heydemann-Strasse 8, D-18057 Rostock, Germany
| | - Andreas Dotzauer
- Laboratory of Virus Research, University of Bremen, Leobener Straße/UFT, 28359, D-28359 Bremen, Germany
| | - Ingrid Bauer
- Institute of Medical Genetics, University Rostock Medical Center, Ernst-Heydemann-Strasse 8, D-18057 Rostock, Germany
| |
Collapse
|
237
|
Sturgill EG, Norris SR, Guo Y, Ohi R. Kinesin-5 inhibitor resistance is driven by kinesin-12. J Cell Biol 2016; 213:213-27. [PMID: 27091450 PMCID: PMC5084272 DOI: 10.1083/jcb.201507036] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 03/10/2016] [Indexed: 12/27/2022] Open
Abstract
The kinesin-5 Eg5 is essential for mitotic progression, and the lethal effects of Eg5 inhibitors make these inhibitors attractive candidates for chemotherapy drugs. Sturgill et al. show that kinesin-12 and a nonmotile Eg5 mutant form an alternative spindle assembly pathway that provides resistance to Eg5 inhibitors. The microtubule (MT) cytoskeleton bipolarizes at the onset of mitosis to form the spindle. In animal cells, the kinesin-5 Eg5 primarily drives this reorganization by actively sliding MTs apart. Its primacy during spindle assembly renders Eg5 essential for mitotic progression, demonstrated by the lethal effects of kinesin-5/Eg5 inhibitors (K5Is) administered in cell culture. However, cultured cells can acquire resistance to K5Is, indicative of alternative spindle assembly mechanisms and/or pharmacological failure. Through characterization of novel K5I-resistant cell lines, we unveil an Eg5 motility-independent spindle assembly pathway that involves both an Eg5 rigor mutant and the kinesin-12 Kif15. This pathway centers on spindle MT bundling instead of Kif15 overexpression, distinguishing it from those previously described. We further show that large populations (∼107 cells) of HeLa cells require Kif15 to survive K5I treatment. Overall, this study provides insight into the functional plasticity of mitotic kinesins during spindle assembly and has important implications for the development of antimitotic regimens that target this process.
Collapse
Affiliation(s)
- Emma G Sturgill
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Stephen R Norris
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Yan Guo
- Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Ryoma Ohi
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232
| |
Collapse
|
238
|
Lu M, Zhu H, Wang X, Zhang D, Xiong L, Xu L, You Y. The prognostic role of Eg5 expression in laryngeal squamous cell carcinoma. Pathology 2016; 48:214-8. [DOI: 10.1016/j.pathol.2016.02.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 11/09/2015] [Accepted: 11/11/2015] [Indexed: 12/28/2022]
|
239
|
The natural diterpene tonantzitlolone A and its synthetic enantiomer inhibit cell proliferation and kinesin-5 function. Eur J Med Chem 2016; 112:164-170. [DOI: 10.1016/j.ejmech.2016.02.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 02/05/2016] [Accepted: 02/07/2016] [Indexed: 01/05/2023]
|
240
|
Braun M, Lansky Z, Hilitski F, Dogic Z, Diez S. Entropic forces drive contraction of cytoskeletal networks. Bioessays 2016; 38:474-81. [DOI: 10.1002/bies.201500183] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Marcus Braun
- B CUBE – Center for Molecular BioengineeringTechnische Universität DresdenDresdenGermany
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
| | - Zdenek Lansky
- B CUBE – Center for Molecular BioengineeringTechnische Universität DresdenDresdenGermany
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Institute of Biotechnology CASBIOCEV CenterVestecCzech Republic
| | - Feodor Hilitski
- Martin Fisher School of PhysicsBrandeis UniversityWalthamMAUSA
| | - Zvonimir Dogic
- Martin Fisher School of PhysicsBrandeis UniversityWalthamMAUSA
| | - Stefan Diez
- B CUBE – Center for Molecular BioengineeringTechnische Universität DresdenDresdenGermany
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
| |
Collapse
|
241
|
Kinesin-12 motors cooperate to suppress microtubule catastrophes and drive the formation of parallel microtubule bundles. Proc Natl Acad Sci U S A 2016; 113:E1635-44. [PMID: 26969727 DOI: 10.1073/pnas.1516370113] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Human Kinesin-12 (hKif15) plays a crucial role in assembly and maintenance of the mitotic spindle. These functions of hKif15 are partially redundant with Kinesin-5 (Eg5), which can cross-link and drive the extensile sliding of antiparallel microtubules. Although both motors are known to be tetramers, the functional properties of hKif15 are less well understood. Here we reveal how single or multiple Kif15 motors can cross-link, transport, and focus the plus-ends of intersecting microtubules. During transport, Kif15 motors step simultaneously along both microtubules with relative microtubule transport driven by a velocity differential between motor domain pairs. Remarkably, this differential is affected by the underlying intersection geometry: the differential is low on parallel and extreme on antiparallel microtubules where one motor domain pair becomes immobile. As a result, when intersecting microtubules are antiparallel, canonical transport of one microtubule along the other is allowed because one motor is firmly attached to one microtubule while it is stepping on the other. When intersecting microtubules are parallel, however, Kif15 motors can drive (biased) parallel sliding because the motor simultaneously steps on both microtubules that it cross-links. These microtubule rearrangements will focus microtubule plus-ends and finally lead to the formation of parallel bundles. At the same time, Kif15 motors cooperate to suppress catastrophe events at polymerizing microtubule plus-ends, raising the possibility that Kif15 motors may synchronize the dynamics of bundles that they have assembled. Thus, Kif15 is adapted to operate on parallel microtubule substrates, a property that clearly distinguishes it from the other tetrameric spindle motor, Eg5.
Collapse
|
242
|
Zhang W, Zhai L, Lu W, Boohaker RJ, Padmalayam I, Li Y. Discovery of Novel Allosteric Eg5 Inhibitors Through Structure-Based Virtual Screening. Chem Biol Drug Des 2016; 88:178-87. [PMID: 26864917 DOI: 10.1111/cbdd.12744] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 12/08/2015] [Accepted: 01/31/2016] [Indexed: 12/11/2022]
Abstract
Mitotic kinesin Eg5 is an attractive anticancer drug target. Discovery of Eg5 inhibitors has been focused on targeting the 'monastrol-binding site'. However, acquired drug resistance has been reported for such inhibitors. Therefore, identifying new Eg5 inhibitors which function through a different mechanism(s) could complement current drug candidates and improve drug efficacy. In this study, we explored a novel allosteric site of Eg5 and identified new Eg5 inhibitors through structure-based virtual screening. Experiments with the saturation-transfer difference NMR demonstrated that the identified Eg5 inhibitor SRI35566 binds directly to Eg5 without involving microtubules. Moreover, SRI35566 and its two analogs significantly induced monopolar spindle formation in colorectal cancer HCT116 cells and suppressed cancer cell viability and colony formation. Together, our findings reveal a new allosteric regulation mechanism of Eg5 and a novel drug targeting site for cancer therapy.
Collapse
Affiliation(s)
- Wei Zhang
- Drug Discovery Division, Southern Research Institute, 2000 9th Avenue South, Birmingham, AL, USA
| | - Ling Zhai
- Drug Discovery Division, Southern Research Institute, 2000 9th Avenue South, Birmingham, AL, USA
| | - Wenyan Lu
- Drug Discovery Division, Southern Research Institute, 2000 9th Avenue South, Birmingham, AL, USA
| | - Rebecca J Boohaker
- Drug Discovery Division, Southern Research Institute, 2000 9th Avenue South, Birmingham, AL, USA
| | - Indira Padmalayam
- Drug Discovery Division, Southern Research Institute, 2000 9th Avenue South, Birmingham, AL, USA
| | - Yonghe Li
- Drug Discovery Division, Southern Research Institute, 2000 9th Avenue South, Birmingham, AL, USA
| |
Collapse
|
243
|
Kevenaar JT, Bianchi S, van Spronsen M, Olieric N, Lipka J, Frias CP, Mikhaylova M, Harterink M, Keijzer N, Wulf PS, Hilbert M, Kapitein LC, de Graaff E, Ahkmanova A, Steinmetz MO, Hoogenraad CC. Kinesin-Binding Protein Controls Microtubule Dynamics and Cargo Trafficking by Regulating Kinesin Motor Activity. Curr Biol 2016; 26:849-61. [PMID: 26948876 DOI: 10.1016/j.cub.2016.01.048] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 12/31/2015] [Accepted: 01/20/2016] [Indexed: 11/24/2022]
Abstract
Kinesin motor proteins play a fundamental role for normal neuronal development by controlling intracellular cargo transport and microtubule (MT) cytoskeleton organization. Regulating kinesin activity is important to ensure their proper functioning, and their misregulation often leads to severe human neurological disorders. Homozygous nonsense mutations in kinesin-binding protein (KBP)/KIAA1279 cause the neurological disorder Goldberg-Shprintzen syndrome (GOSHS), which is characterized by intellectual disability, microcephaly, and axonal neuropathy. Here, we show that KBP regulates kinesin activity by interacting with the motor domains of a specific subset of kinesins to prevent their association with the MT cytoskeleton. The KBP-interacting kinesins include cargo-transporting motors such as kinesin-3/KIF1A and MT-depolymerizing motor kinesin-8/KIF18A. We found that KBP blocks KIF1A/UNC-104-mediated synaptic vesicle transport in cultured hippocampal neurons and in C. elegans PVD sensory neurons. In contrast, depletion of KBP results in the accumulation of KIF1A motors and synaptic vesicles in the axonal growth cone. We also show that KBP regulates neuronal MT dynamics by controlling KIF18A activity. Our data suggest that KBP functions as a kinesin inhibitor that modulates MT-based cargo motility and depolymerizing activity of a subset of kinesin motors. We propose that misregulation of KBP-controlled kinesin motors may represent the underlying molecular mechanism that contributes to the neuropathological defects observed in GOSHS patients.
Collapse
Affiliation(s)
- Josta T Kevenaar
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands
| | - Sarah Bianchi
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Myrrhe van Spronsen
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands; Department of Neuroscience, Erasmus Medical Center, 3015 Rotterdam, the Netherlands
| | - Natacha Olieric
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Joanna Lipka
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands; International Institute of Molecular and Cell Biology, 02-1009 Warsaw, Poland
| | - Cátia P Frias
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands
| | - Marina Mikhaylova
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands; RG Neuroplasticity, Leibniz-Institute for Neurobiology, 39118 Magdeburg, Germany
| | - Martin Harterink
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands
| | - Nanda Keijzer
- Department of Neuroscience, Erasmus Medical Center, 3015 Rotterdam, the Netherlands
| | - Phebe S Wulf
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands; Department of Neuroscience, Erasmus Medical Center, 3015 Rotterdam, the Netherlands
| | - Manuel Hilbert
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Lukas C Kapitein
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands; Department of Neuroscience, Erasmus Medical Center, 3015 Rotterdam, the Netherlands
| | - Esther de Graaff
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands; Department of Neuroscience, Erasmus Medical Center, 3015 Rotterdam, the Netherlands
| | - Anna Ahkmanova
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands
| | - Michel O Steinmetz
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, the Netherlands; Department of Neuroscience, Erasmus Medical Center, 3015 Rotterdam, the Netherlands.
| |
Collapse
|
244
|
Brust-Mascher I, Civelekoglu-Scholey G, Scholey JM. Mechanism for Anaphase B: Evaluation of "Slide-and-Cluster" versus "Slide-and-Flux-or-Elongate" Models. Biophys J 2016; 108:2007-18. [PMID: 25902440 PMCID: PMC4407247 DOI: 10.1016/j.bpj.2015.03.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 02/08/2015] [Accepted: 03/02/2015] [Indexed: 01/07/2023] Open
Abstract
Elongation of the mitotic spindle during anaphase B contributes to chromosome segregation in many cells. Here, we quantitatively test the ability of two models for spindle length control to describe the dynamics of anaphase B spindle elongation using experimental data from Drosophila embryos. In the slide-and-flux-or-elongate (SAFE) model, kinesin-5 motors persistently slide apart antiparallel interpolar microtubules (ipMTs). During pre-anaphase B, this outward sliding of ipMTs is balanced by depolymerization of their minus ends at the poles, producing poleward flux, while the spindle maintains a constant length. Following cyclin B degradation, ipMT depolymerization ceases so the sliding ipMTs can push the poles apart. The competing slide-and-cluster (SAC) model proposes that MTs nucleated at the equator are slid outward by the cooperative actions of the bipolar kinesin-5 and a minus-end-directed motor, which then pulls the sliding MTs inward and clusters them at the poles. In assessing both models, we assume that kinesin-5 preferentially cross-links and slides apart antiparallel MTs while the MT plus ends exhibit dynamic instability. However, in the SAC model, minus-end-directed motors bind the minus ends of MTs as cargo and transport them poleward along adjacent, parallel MT tracks, whereas in the SAFE model, all MT minus ends that reach the pole are depolymerized by kinesin-13. Remarkably, the results show that within a narrow range of MT dynamic instability parameters, both models can reproduce the steady-state length and dynamics of pre-anaphase B spindles and the rate of anaphase B spindle elongation. However, only the SAFE model reproduces the change in MT dynamics observed experimentally at anaphase B onset. Thus, although both models explain many features of anaphase B in this system, our quantitative evaluation of experimental data regarding several different aspects of spindle dynamics suggests that the SAFE model provides a better fit.
Collapse
Affiliation(s)
- Ingrid Brust-Mascher
- Department of Molecular and Cell Biology, University of California at Davis, Davis, California
| | - Gul Civelekoglu-Scholey
- Department of Molecular and Cell Biology, University of California at Davis, Davis, California
| | - Jonathan M Scholey
- Department of Molecular and Cell Biology, University of California at Davis, Davis, California.
| |
Collapse
|
245
|
Hueschen CL, Long AF, Dumont S. Kinesin-5: A Team Is Just the Sum of Its Parts. Dev Cell 2016; 34:609-10. [PMID: 26418291 DOI: 10.1016/j.devcel.2015.09.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
How the cell builds a spindle remains an open question. In this issue of Developmental Cell, Shimamoto, Forth, and Kapoor (2015) show that kinesin-5 motor ensembles can exert sliding forces that scale with microtubule overlap length. This behavior could allow microtubule architecture-dependent modulation of force and contribute to spindle self-organization.
Collapse
Affiliation(s)
- Christina L Hueschen
- Department of Cell & Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA; Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Alexandra F Long
- Department of Cell & Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA; Tetrad Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Sophie Dumont
- Department of Cell & Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA; Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA; Tetrad Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94143, USA.
| |
Collapse
|
246
|
Overlap microtubules link sister k-fibres and balance the forces on bi-oriented kinetochores. Nat Commun 2016; 7:10298. [PMID: 26728792 PMCID: PMC4728446 DOI: 10.1038/ncomms10298] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/26/2015] [Indexed: 02/04/2023] Open
Abstract
During metaphase, forces on kinetochores are exerted by k-fibres, bundles of microtubules that end at the kinetochore. Interestingly, non-kinetochore microtubules have been observed between sister kinetochores, but their function is unknown. Here we show by laser-cutting of a k-fibre in HeLa and PtK1 cells that a bundle of non-kinetochore microtubules, which we term ‘bridging fibre', bridges sister k-fibres and balances the interkinetochore tension. We found PRC1 and EB3 in the bridging fibre, suggesting that it consists of antiparallel dynamic microtubules. By using a theoretical model that includes a bridging fibre, we show that the forces at the pole and at the kinetochore depend on the bridging fibre thickness. Moreover, our theory and experiments show larger relaxation of the interkinetochore distance for cuts closer to kinetochores. We conclude that the bridging fibre, by linking sister k-fibres, withstands the tension between sister kinetochores and enables the spindle to obtain a curved shape. During metaphase, k-fibre microtubules exert force on kinetochores, but there are also non-kinetochore microtubules close to kinetochores without a known function. Here the authors show that these microtubules, which they call bridging fibres, balance interkinetochore tension by bridging sister k-fibres.
Collapse
|
247
|
Shimamoto Y, Forth S, Kapoor TM. Measuring Pushing and Braking Forces Generated by Ensembles of Kinesin-5 Crosslinking Two Microtubules. Dev Cell 2016; 34:669-81. [PMID: 26418296 DOI: 10.1016/j.devcel.2015.08.017] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 07/07/2015] [Accepted: 08/26/2015] [Indexed: 01/10/2023]
Abstract
The proper organization of the microtubule-based mitotic spindle is proposed to depend on nanometer-sized motor proteins generating forces that scale with a micron-sized geometric feature, such as microtubule overlap length. However, it is unclear whether such regulation can be achieved by any mitotic motor protein. Here, we employ an optical-trap- and total internal reflection fluorescence (TIRF)-based assay to show that ensembles of kinesin-5, a conserved mitotic motor protein, can push apart overlapping antiparallel microtubules to generate a force whose magnitude scales with filament overlap length. We also find that kinesin-5 can produce overlap-length-dependent "brake-like" resistance against relative microtubule sliding in both parallel and antiparallel geometries, an activity that has been suggested by cell biological studies but had not been directly measured. Together, these findings, along with numerical simulations, reveal how a motor protein can function as an analog converter, "reading" simple geometric and dynamic features in cytoskeletal networks to produce regulated force outputs.
Collapse
Affiliation(s)
- Yuta Shimamoto
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY 10065, USA; JST PRESTO, The Rockefeller University, New York, NY 10065, USA
| | - Scott Forth
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY 10065, USA
| | - Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY 10065, USA.
| |
Collapse
|
248
|
Jakobs M, Franze K, Zemel A. Force Generation by Molecular-Motor-Powered Microtubule Bundles; Implications for Neuronal Polarization and Growth. Front Cell Neurosci 2015; 9:441. [PMID: 26617489 PMCID: PMC4639704 DOI: 10.3389/fncel.2015.00441] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 10/26/2015] [Indexed: 11/16/2022] Open
Abstract
The heavily cross-linked microtubule (MT) bundles found in neuronal processes play a central role in the initiation, growth and maturation of axons and dendrites; however, a quantitative understanding of their mechanical function is still lacking. We here developed computer simulations to investigate the dynamics of force generation in 1D bundles of MTs that are cross-linked and powered by molecular motors. The motion of filaments and the forces they exert are investigated as a function of the motor type (unipolar or bipolar), MT density and length, applied load, and motor connectivity. We demonstrate that only unipolar motors (e.g., kinesin-1) can provide the driving force for bundle expansion, while bipolar motors (e.g., kinesin-5) oppose it. The force generation capacity of the bundles is shown to depend sharply on the fraction of unipolar motors due to a percolation transition that must occur in the bundle. Scaling laws between bundle length, force, MT length and motor fraction are presented. In addition, we investigate the dynamics of growth in the presence of a constant influx of MTs. Beyond a short equilibration period, the bundles grow linearly in time. In this growth regime, the bundle extends as one mass forward with most filaments sliding with the growth velocity. The growth velocity is shown to be dictated by the inward flux of MTs, to inversely scale with the load and to be independent of the free velocity of the motors. These findings provide important molecular-level insights into the mechanical function of the MT cytoskeleton in normal axon growth and regeneration after injury.
Collapse
Affiliation(s)
- Maximilian Jakobs
- Department of Physiology, Development and Neuroscience, University of CambridgeCambridge, UK
- Bonn Cologne Graduate School of Physics and Astronomy, University of CologneCologne, Germany
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, University of CambridgeCambridge, UK
| | - Assaf Zemel
- Institute of Dental Sciences and Fritz Haber Research Center for Molecular Dynamics, Hebrew University of JerusalemJerusalem, Israel
| |
Collapse
|
249
|
Overexpression of Eg5 correlates with high grade astrocytic neoplasm. J Neurooncol 2015; 126:77-80. [DOI: 10.1007/s11060-015-1954-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 10/05/2015] [Indexed: 11/25/2022]
|
250
|
Abstract
Kinesin-5 slides antiparallel microtubules during spindle assembly, and regulates the branching of growing axons. Besides the mechanical activities enabled by its tetrameric configuration, the specific motor properties of kinesin-5 that underlie its cellular function remain unclear. Here by engineering a stable kinesin-5 dimer and reconstituting microtubule dynamics in vitro, we demonstrate that kinesin-5 promotes microtubule polymerization by increasing the growth rate and decreasing the catastrophe frequency. Strikingly, microtubules growing in the presence of kinesin-5 have curved plus ends, suggesting that the motor stabilizes growing protofilaments. Single-molecule fluorescence experiments reveal that kinesin-5 remains bound to the plus ends of static microtubules for 7 s, and tracks growing microtubule plus ends in a manner dependent on its processivity. We propose that kinesin-5 pauses at microtubule plus ends and enhances polymerization by stabilizing longitudinal tubulin-tubulin interactions, and that these activities underlie the ability kinesin-5 to slide and stabilize microtubule bundles in cells.
Collapse
|