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Gavilan MP, Gandolfo P, Balestra FR, Arias F, Bornens M, Rios RM. The dual role of the centrosome in organizing the microtubule network in interphase. EMBO Rep 2018; 19:embr.201845942. [PMID: 30224411 DOI: 10.15252/embr.201845942] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 08/27/2018] [Accepted: 08/29/2018] [Indexed: 11/09/2022] Open
Abstract
Here, we address the regulation of microtubule nucleation during interphase by genetically ablating one, or two, of three major mammalian γ-TuRC-binding factors namely pericentrin, CDK5Rap2, and AKAP450. Unexpectedly, we find that while all of them participate in microtubule nucleation at the Golgi apparatus, they only modestly contribute at the centrosome where CEP192 has a more predominant function. We also show that inhibiting microtubule nucleation at the Golgi does not affect centrosomal activity, whereas manipulating the number of centrosomes with centrinone modifies microtubule nucleation activity of the Golgi apparatus. In centrosome-free cells, inhibition of Golgi-based microtubule nucleation triggers pericentrin-dependent formation of cytoplasmic-nucleating structures. Further depletion of pericentrin under these conditions leads to the generation of individual microtubules in a γ-tubulin-dependent manner. In all cases, a conspicuous MT network forms. Strikingly, centrosome loss increases microtubule number independently of where they were growing from. Our results lead to an unexpected view of the interphase centrosome that would control microtubule network organization not only by nucleating microtubules, but also by modulating the activity of alternative microtubule-organizing centers.
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Affiliation(s)
- Maria P Gavilan
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
| | - Pablo Gandolfo
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
| | - Fernando R Balestra
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
| | - Francisco Arias
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
| | | | - Rosa M Rios
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
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Song JG, King MR, Zhang R, Kadzik RS, Thawani A, Petry S. Mechanism of how augmin directly targets the γ-tubulin ring complex to microtubules. J Cell Biol 2018; 217:2417-2428. [PMID: 29875259 PMCID: PMC6028527 DOI: 10.1083/jcb.201711090] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 03/10/2018] [Accepted: 05/01/2018] [Indexed: 12/28/2022] Open
Abstract
Microtubules (MTs) must be generated from precise locations to form the structural frameworks required for cell shape and function. MTs are nucleated by the γ-tubulin ring complex (γ-TuRC), but it remains unclear how γ-TuRC gets to the right location. Augmin has been suggested to be a γ-TuRC targeting factor and is required for MT nucleation from preexisting MTs. To determine augmin's architecture and function, we purified Xenopus laevis augmin from insect cells. We demonstrate that augmin is sufficient to target γ-TuRC to MTs by in vitro reconstitution. Augmin is composed of two functional parts. One module (tetramer-II) is necessary for MT binding, whereas the other (tetramer-III) interacts with γ-TuRC. Negative-stain electron microscopy reveals that both tetramers fit into the Y-shape of augmin, and MT branching assays reveal that both are necessary for MT nucleation. The finding that augmin can directly bridge MTs with γ-TuRC via these two tetramers adds to our mechanistic understanding of how MTs can be nucleated from preexisting MTs.
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Affiliation(s)
- Jae-Geun Song
- Department of Molecular Biology, Princeton University, Princeton, NJ
| | - Matthew R King
- Department of Molecular Biology, Princeton University, Princeton, NJ
| | - Rui Zhang
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - Rachel S Kadzik
- Department of Molecular Biology, Princeton University, Princeton, NJ
| | - Akanksha Thawani
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ
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53
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Kumari A, Panda D. Regulation of microtubule stability by centrosomal proteins. IUBMB Life 2018; 70:602-611. [DOI: 10.1002/iub.1865] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 04/12/2018] [Indexed: 12/12/2022]
Affiliation(s)
- Anuradha Kumari
- Department of Biosciences and Bioengineering; Indian Institute of Technology Bombay; Mumbai India
| | - Dulal Panda
- Department of Biosciences and Bioengineering; Indian Institute of Technology Bombay; Mumbai India
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54
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Zvorykina Y, Tvorogova A, Gladkikh A, Vorobjev I. Non-centrosomal MTs play a crucial role in organization of MT array in interphase fibroblasts. AIMS GENETICS 2018; 5:141-160. [PMID: 31435518 PMCID: PMC6698575 DOI: 10.3934/genet.2018.2.141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 03/15/2018] [Indexed: 11/30/2022]
Abstract
Microtubules in interphase fibroblast-like cells are thought to be organized in a radial array growing from a centrosome-based microtubule-organizing center (MTOC) to the cell edges. However, many morphogenetic processes require the asymmetry of the microtubules (MT) array. One of the possible mechanisms of this asymmetry could be the presence of non-centrosomal microtubules in different intracellular areas. To evaluate the role of centrosome-born and non-centrosomal microtubules in the organization of microtubule array in motile 3T3 fibroblasts, we have performed the high-throughput analysis of microtubule growth in different functional zones of the cell and distinguished three subpopulations of growing microtubules (centrosome-born, marginal and inner cytoplasmic). Centrosome as an active microtubule-organizing center was absent in half of the cell population. However, these cells do not show any difference in microtubule growth pattern. In cells with active centrosome, it was constantly forming short (ephemeral) MTs, and ∼15–20 MT per minute grow outwards for a distance >1 µm. Almost no persistent growth of microtubules was observed in these cells with the average growth length of 5–6 µm and duration of growth periods within 30 s. However, the number of growing ends increased towards cell margin, especially towards the active edges. We found the peripheral cytoplasmic foci of microtubule growth there. During recovery from nocodazole treatment microtubules started to grow around the centrosome in a normal way and independently in all the cell areas. Within 5 minutes microtubules continued to grow mainly near the cell edge. Thus, our data confirm the negligible role of centrosome as MTOC in 3T3 fibroblasts and propose a model of non-centrosomal microtubules as major players that create the cell asymmetry in the cells with a mesenchymal type of motility. We suggest that increased density of dynamic microtubules near the active lamellum could be supported by microtubule-based microtubule nucleation.
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Affiliation(s)
| | - Anna Tvorogova
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Aleena Gladkikh
- Biology Department, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Ivan Vorobjev
- Biology Department, M.V. Lomonosov Moscow State University, Moscow, Russia.,A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Moscow, Russia.,School of Science and Technology, and National Laboratory Astana, Nazarbayev University, Astana, Kazakhstan
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55
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Coming into Focus: Mechanisms of Microtubule Minus-End Organization. Trends Cell Biol 2018; 28:574-588. [PMID: 29571882 DOI: 10.1016/j.tcb.2018.02.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 02/17/2018] [Accepted: 02/27/2018] [Indexed: 11/22/2022]
Abstract
Microtubule organization has a crucial role in regulating cell architecture. The geometry of microtubule arrays strongly depends on the distribution of sites responsible for microtubule nucleation and minus-end attachment. In cycling animal cells, the centrosome often represents a dominant microtubule-organizing center (MTOC). However, even in cells with a radial microtubule system, many microtubules are not anchored at the centrosome, but are instead linked to the Golgi apparatus or other structures. Non-centrosomal microtubules predominate in many types of differentiated cell and in mitotic spindles. In this review, we discuss recent advances in understanding how the organization of centrosomal and non-centrosomal microtubule networks is controlled by proteins involved in microtubule nucleation and specific factors that recognize free microtubule minus ends and regulate their localization and dynamics.
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VPS4 is a dynamic component of the centrosome that regulates centrosome localization of γ-tubulin, centriolar satellite stability and ciliogenesis. Sci Rep 2018; 8:3353. [PMID: 29463826 PMCID: PMC5820263 DOI: 10.1038/s41598-018-21491-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 02/06/2018] [Indexed: 01/18/2023] Open
Abstract
The hexameric AAA ATPase VPS4 facilitates ESCRT III filament disassembly on diverse intracellular membranes. ESCRT III components and VPS4 have been localized to the ciliary transition zone and spindle poles and reported to affect centrosome duplication and spindle pole stability. How the canonical ESCRT pathway could mediate these events is unclear. We studied the association of VPS4 with centrosomes and found that GFP-VPS4 was a dynamic component of both mother and daughter centrioles. A mutant, VPS4EQ, which can’t hydrolyze ATP, was less dynamic and accumulated at centrosomes. Centrosome localization of the VPS4EQ mutant, caused reduced γ-tubulin levels at centrosomes and consequently decreased microtubule growth and altered centrosome positioning. In addition, preventing VPS4 ATP hydrolysis nearly eliminated centriolar satellites and paused ciliogensis after formation of the ciliary vesicle. Zebrafish embryos injected with GFP-VPS4EQ mRNA were less viable, exhibited developmental defects and had fewer cilia in Kupffer’s vesicle. Surprisingly, ESCRT III proteins seldom localized to centrosomes and their depletion did not lead to these phenotypes. Our data support an ESCRT III-independent function for VPS4 at the centrosome and reveal that this evolutionary conserved AAA ATPase influences diverse centrosome functions and, as a result, global cellular architecture and development.
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57
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Rale MJ, Kadzik RS, Petry S. Phase Transitioning the Centrosome into a Microtubule Nucleator. Biochemistry 2017; 57:30-37. [PMID: 29256606 DOI: 10.1021/acs.biochem.7b01064] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Centrosomes are self-assembling, micron-scale, nonmembrane bound organelles that nucleate microtubules (MTs) and organize the microtubule cytoskeleton of the cell. They orchestrate critical cellular processes such as ciliary-based motility, vesicle trafficking, and cell division. Much is known about the role of the centrosome in these contexts, but we have a less comprehensive understanding of how the centrosome assembles and generates microtubules. Studies over the past 10 years have fundamentally shifted our view of these processes. Subdiffraction imaging has probed the amorphous haze of material surrounding the core of the centrosome revealing a complex, hierarchically organized structure whose composition and size changes profoundly during the transition from interphase to mitosis. New biophysical insights into protein phase transitions, where a diffuse protein spontaneously separates into a locally concentrated, nonmembrane bounded compartment, have provided a fresh perspective into how the centrosome might rapidly condense from diffuse cytoplasmic components. In this Perspective, we focus on recent findings that identify several centrosomal proteins that undergo phase transitions. We discuss how to reconcile these results with the current model of the underlying organization of proteins in the centrosome. Furthermore, we reflect on how these findings impact our understanding of how the centrosome undergoes self-assembly and promotes MT nucleation.
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Affiliation(s)
- Michael J Rale
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States
| | - Rachel S Kadzik
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States
| | - Sabine Petry
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States
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58
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Microtubule-Organizing Centers: Towards a Minimal Parts List. Trends Cell Biol 2017; 28:176-187. [PMID: 29173799 DOI: 10.1016/j.tcb.2017.10.005] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 10/20/2017] [Accepted: 10/23/2017] [Indexed: 12/17/2022]
Abstract
Despite decades of molecular analysis of the centrosome, an important microtubule-organizing center (MTOC) of animal cells, the molecular basis of microtubule organization remains obscure. A major challenge is the sheer complexity of the interplay of the hundreds of proteins that constitute the centrosome. However, this complexity owes not only to the centrosome's role as a MTOC but also to the requirements of its duplication cycle and to various other functions such as the formation of cilia, the integration of various signaling pathways, and the organization of actin filaments. Thus, rather than using the parts lists to reconstruct the centrosome, we propose to identify the subset of proteins minimally needed to assemble a MTOC and to study this process at non-centrosomal sites.
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59
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Werner S, Pimenta-Marques A, Bettencourt-Dias M. Maintaining centrosomes and cilia. J Cell Sci 2017; 130:3789-3800. [DOI: 10.1242/jcs.203505] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
ABSTRACT
Centrosomes and cilia are present in organisms from all branches of the eukaryotic tree of life. These structures are composed of microtubules and various other proteins, and are required for a plethora of cell processes such as structuring the cytoskeleton, sensing the environment, and motility. Deregulation of centrosome and cilium components leads to a wide range of diseases, some of which are incompatible with life. Centrosomes and cilia are thought to be very stable and can persist over long periods of time. However, these structures can disappear in certain developmental stages and diseases. Moreover, some centrosome and cilia components are quite dynamic. While a large body of knowledge has been produced regarding the biogenesis of these structures, little is known about how they are maintained. In this Review, we propose the existence of specific centrosome and cilia maintenance programs, which are regulated during development and homeostasis, and when deregulated can lead to disease.
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Affiliation(s)
- Sascha Werner
- Cell Cycle Regulation Lab, Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal
| | - Ana Pimenta-Marques
- Cell Cycle Regulation Lab, Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal
| | - Mónica Bettencourt-Dias
- Cell Cycle Regulation Lab, Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal
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60
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Cukier CD, Tourdes A, El-Mazouni D, Guillet V, Nomme J, Mourey L, Milon A, Merdes A, Gervais V. NMR secondary structure and interactions of recombinant human MOZART1 protein, a component of the gamma-tubulin complex. Protein Sci 2017; 26:2240-2248. [PMID: 28851027 PMCID: PMC5654863 DOI: 10.1002/pro.3282] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 08/17/2017] [Accepted: 08/17/2017] [Indexed: 12/02/2022]
Abstract
Mitotic‐spindle organizing protein associated with a ring of γ‐tubulin 1 (MOZART1) is an 8.5 kDa protein linked to regulation of γ‐tubulin ring complexes (γTuRCs), which are involved in nucleation of microtubules. Despite its small size, MOZART1 represents a challenging target for detailed characterization in vitro. We described herein a protocol for efficient production of recombinant human MOZART1 in Escherichia coli and assessed the properties of the purified protein using a combination of size exclusion chromatography coupled with multiangle light scattering (SEC‐MALS), dynamic light scattering (DLS), and nuclear magnetic resonance (NMR) experiments. MOZART1 forms heterogeneous oligomers in solution. We identified optimal detergent and buffer conditions for recording well resolved NMR experiments allowing nearly full protein assignment and identification of three distinct alpha‐helical structured regions. Finally, using NMR, we showed that MOZART1 interacts with the N‐terminus (residues 1–250) of GCP3 (γ‐tubulin complex protein 3). Our data illustrate the capacity of MOZART1 to form oligomers, promoting multiple contacts with a subset of protein partners in the context of microtubule nucleation.
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Affiliation(s)
- Cyprian D Cukier
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Audrey Tourdes
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Dounia El-Mazouni
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Valérie Guillet
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Julian Nomme
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Lionel Mourey
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Alain Milon
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Andreas Merdes
- Centre de Biologie du Développement, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Virginie Gervais
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
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61
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A centrosomal protein FOR20 regulates microtubule assembly dynamics and plays a role in cell migration. Biochem J 2017; 474:2841-2859. [DOI: 10.1042/bcj20170303] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 07/03/2017] [Accepted: 07/10/2017] [Indexed: 11/17/2022]
Abstract
Here, we report that a centrosomal protein FOR20 [FOP (FGFR1 (fibroblast growth factor receptor 1) oncogene protein)-like protein of molecular mass of 20 kDa; also named as C16orf63, FLJ31153 or PHSECRG2] can regulate the assembly and stability of microtubules. Both FOR20 IgG antibody and GST (glutathione S-transferase)-tagged FOR20 could precipitate tubulin from the HeLa cell extract, indicating a possible interaction between FOR20 and tubulin. FOR20 was also detected in goat brain tissue extract and it cycled with microtubule-associated proteins. Furthermore, FOR20 bound to purified tubulin and inhibited the assembly of tubulin in vitro. The overexpression of FOR20 depolymerized interphase microtubules and the depletion of FOR20 prevented nocodazole-induced depolymerization of microtubules in HeLa cells. In addition, the depletion of FOR20 suppressed the dynamics of individual microtubules in live HeLa cells. FOR20-depleted MDA-MB-231 cells displayed zigzag motion and migrated at a slower rate than the control cells, indicating that FOR20 plays a role in directed cell migration. The results suggested that the centrosomal protein FOR20 is a new member of the microtubule-associated protein family and that it regulates the assembly and dynamics of microtubules.
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Barandalla M, Shi H, Xiao H, Colleoni S, Galli C, Lio P, Trotter M, Lazzari G. Global gene expression profiling and senescence biomarker analysis of hESC exposed to H 2O 2 induced non-cytotoxic oxidative stress. Stem Cell Res Ther 2017; 8:160. [PMID: 28676096 PMCID: PMC5497375 DOI: 10.1186/s13287-017-0602-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 05/31/2017] [Indexed: 02/07/2023] Open
Abstract
Background Human embryonic stem cells (hESCs) potentially offer new routes to study, on the basis of the Developmental Origins of Health and Disease (DOHaD) concept, how the maternal environment during pregnancy influences the offspring’s health and can predispose to chronic disease in later life. Reactive oxygen species (ROS), antioxidant defences and cellular redox status play a key function in gene expression regulation and are involved in diabetes and metabolic syndromes as in ageing. Methods We have, therefore, designed an in vitro cell model of oxidative stress by exposing hESCs to hydrogen peroxide (H2O2) during 72 h, in order to resemble the period of preimplantation embryonic development. Results We have analysed the global gene expression profiles of hESCs (HUES3) exposed to non-cytotoxic H2O2 concentrations, using Illumina microarray HT-12 v4, and we found the differential expression of 569 upregulated and 485 downregulated genes. The most affected gene ontology categories were those related with RNA processing and splicing, oxidation reduction and sterol metabolic processes. We compared our findings with a published RNA-seq profiling dataset of human embryos developed in vitro, thereupon exposed to oxidative stress, and we observed that one of the common downregulated genes between this publication and our data, NEDD1, is involved in centrosome structure and function. Conclusions Therefore, we assessed the presence of supernumerary centrosomes and showed that the percentage of cells with more than two centrosomes increased acutely with H2O2 treatment in hESCs (HUES3 and 7) and in a control somatic cell line (Hs27), inducing a premature entry into senescence. Electronic supplementary material The online version of this article (doi:10.1186/s13287-017-0602-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Maria Barandalla
- Avantea srl, Laboratory of Reproductive Technologies, Via Porcellasco 7/F, Cremona, 26100, Italy.
| | - Hui Shi
- Department of Genetics, University of Cambridge, Cambridge, UK
| | - Hui Xiao
- Computer laboratory, University of Cambridge, Cambridge, UK
| | - Silvia Colleoni
- Avantea srl, Laboratory of Reproductive Technologies, Via Porcellasco 7/F, Cremona, 26100, Italy
| | - Cesare Galli
- Avantea srl, Laboratory of Reproductive Technologies, Via Porcellasco 7/F, Cremona, 26100, Italy.,Department of Medical Sciences, University of Bologna, Bologna, Italy
| | - Pietro Lio
- Computer laboratory, University of Cambridge, Cambridge, UK
| | - Matthew Trotter
- Celgene Institute for Translational Research Europe (CITRE), Seville, Spain
| | - Giovanna Lazzari
- Avantea srl, Laboratory of Reproductive Technologies, Via Porcellasco 7/F, Cremona, 26100, Italy
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63
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Chen JV, Buchwalter RA, Kao LR, Megraw TL. A Splice Variant of Centrosomin Converts Mitochondria to Microtubule-Organizing Centers. Curr Biol 2017; 27:1928-1940.e6. [PMID: 28669756 DOI: 10.1016/j.cub.2017.05.090] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 05/02/2017] [Accepted: 05/31/2017] [Indexed: 11/25/2022]
Abstract
Non-centrosomal microtubule organizing centers (MTOCs) direct microtubule (MT) organization to exert diverse cell-type-specific functions. In Drosophila spermatids, the giant mitochondria provide structural platforms for MT reorganization to support elongation of the extremely long sperm. However, the molecular basis for this mitochondrial MTOC and other non-centrosomal MTOCs has not been discerned. Here we report that Drosophila centrosomin (cnn) expresses two major protein variants: the centrosomal form (CnnC) and a non-centrosomal form in testes (CnnT). CnnC is established as essential for functional centrosomes, the major MTOCs in animal cells. We show that CnnT is expressed exclusively in testes by alternative splicing and localizes to giant mitochondria in spermatids. In cell culture, CnnT targets to the mitochondrial surface, recruits the MT nucleator γ-tubulin ring complex (γ-TuRC), and is sufficient to convert mitochondria to MTOCs independent of core pericentriolar proteins that regulate MT assembly at centrosomes. We mapped two separate domains in CnnT: one that is necessary and sufficient to target it to mitochondria and another that is necessary and sufficient to recruit γ-TuRCs and nucleate MTs. In elongating spermatids, CnnT forms speckles on the giant mitochondria that are required to recruit γ-TuRCs to organize MTs and support spermiogenesis. This molecular characterization of the mitochondrial MTOC defines a minimal molecular requirement for MTOC generation and implicates the potent role of Cnn (or its related) proteins in the direct regulation of MT assembly and organization of non-centrosomal MTOCs.
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Affiliation(s)
- Jieyan V Chen
- Department of Biomedical Sciences, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA.
| | - Rebecca A Buchwalter
- Department of Biomedical Sciences, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA
| | - Ling-Rong Kao
- Department of Biomedical Sciences, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA
| | - Timothy L Megraw
- Department of Biomedical Sciences, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA.
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64
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Abstract
The organization of microtubule networks is crucial for controlling chromosome segregation during cell division, for positioning and transport of different organelles, and for cell polarity and morphogenesis. The geometry of microtubule arrays strongly depends on the localization and activity of the sites where microtubules are nucleated and where their minus ends are anchored. Such sites are often clustered into structures known as microtubule-organizing centers, which include the centrosomes in animals and spindle pole bodies in fungi. In addition, other microtubules, as well as membrane compartments such as the cell nucleus, the Golgi apparatus, and the cell cortex, can nucleate, stabilize, and tether microtubule minus ends. These activities depend on microtubule-nucleating factors, such as γ-tubulin-containing complexes and their activators and receptors, and microtubule minus end-stabilizing proteins with their binding partners. Here, we provide an overview of the current knowledge on how such factors work together to control microtubule organization in different systems.
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Affiliation(s)
- Jingchao Wu
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, The Netherlands; ,
| | - Anna Akhmanova
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 Utrecht, The Netherlands; ,
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65
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Conduit PT. Microtubule organization: A complex solution. J Cell Biol 2017; 213:609-12. [PMID: 27325787 PMCID: PMC4915197 DOI: 10.1083/jcb.201606008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 06/01/2016] [Indexed: 01/12/2023] Open
Abstract
Microtubule nucleation within cells is catalyzed by γ-tubulin ring complexes localized at specific microtubule-organizing centers. In this issue, Muroyama et al. (2016. J. Cell Biol.http://dx.doi.org/10.1083/jcb.201601099) reveal heterogeneity in the composition and function of these complexes, with wide implications for how cells organize their microtubule arrays.
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Affiliation(s)
- Paul T Conduit
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, England, UK
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66
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Sulimenko V, Hájková Z, Klebanovych A, Dráber P. Regulation of microtubule nucleation mediated by γ-tubulin complexes. PROTOPLASMA 2017; 254:1187-1199. [PMID: 28074286 DOI: 10.1007/s00709-016-1070-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 12/22/2016] [Indexed: 05/18/2023]
Abstract
The microtubule cytoskeleton is critically important for spatio-temporal organization of eukaryotic cells. The nucleation of new microtubules is typically restricted to microtubule organizing centers (MTOCs) and requires γ-tubulin that assembles into multisubunit complexes of various sizes. γ-Tubulin ring complexes (TuRCs) are efficient microtubule nucleators and are associated with large number of targeting, activating and modulating proteins. γ-Tubulin-dependent nucleation of microtubules occurs both from canonical MTOCs, such as spindle pole bodies and centrosomes, and additional sites such as Golgi apparatus, nuclear envelope, plasma membrane-associated sites, chromatin and surface of pre-existing microtubules. Despite many advances in structure of γ-tubulin complexes and characterization of γTuRC interacting factors, regulatory mechanisms of microtubule nucleation are not fully understood. Here, we review recent work on the factors and regulatory mechanisms that are involved in centrosomal and non-centrosomal microtubule nucleation.
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Affiliation(s)
- Vadym Sulimenko
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20, Prague 4, Czech Republic
| | - Zuzana Hájková
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20, Prague 4, Czech Republic
| | - Anastasiya Klebanovych
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20, Prague 4, Czech Republic
| | - Pavel Dráber
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20, Prague 4, Czech Republic.
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67
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Baumann C, Wang X, Yang L, Viveiros MM. Error-prone meiotic division and subfertility in mice with oocyte-conditional knockdown of pericentrin. J Cell Sci 2017; 130:1251-1262. [PMID: 28193732 DOI: 10.1242/jcs.196188] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 02/06/2017] [Indexed: 01/24/2023] Open
Abstract
Mouse oocytes lack canonical centrosomes and instead contain unique acentriolar microtubule-organizing centers (aMTOCs). To test the function of these distinct aMTOCs in meiotic spindle formation, pericentrin (Pcnt), an essential centrosome/MTOC protein, was knocked down exclusively in oocytes by using a transgenic RNAi approach. Here, we provide evidence that disruption of aMTOC function in oocytes promotes spindle instability and severe meiotic errors that lead to pronounced female subfertility. Pcnt-depleted oocytes from transgenic (Tg) mice were ovulated at the metaphase-II stage, but show significant chromosome misalignment, aneuploidy and premature sister chromatid separation. These defects were associated with loss of key Pcnt-interacting proteins (γ-tubulin, Nedd1 and Cep215) from meiotic spindle poles, altered spindle structure and chromosome-microtubule attachment errors. Live-cell imaging revealed disruptions in the dynamics of spindle assembly and organization, together with chromosome attachment and congression defects. Notably, spindle formation was dependent on Ran GTPase activity in Pcnt-deficient oocytes. Our findings establish that meiotic division is highly error-prone in the absence of Pcnt and disrupted aMTOCs, similar to what reportedly occurs in human oocytes. Moreover, these data underscore crucial differences between MTOC-dependent and -independent meiotic spindle assembly.
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Affiliation(s)
- Claudia Baumann
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
| | - Xiaotian Wang
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
| | - Luhan Yang
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
| | - Maria M Viveiros
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA .,Regenerative Biosciences Center (RBC), University of Georgia, Athens, GA 30602, USA
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68
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Abstract
The mitotic spindle has a crucial role in ensuring the accurate segregation of chromosomes into the two daughter cells during cell division, which is paramount for maintaining genome integrity. It is a self-organized and dynamic macromolecular structure that is constructed from microtubules, microtubule-associated proteins and motor proteins. Thirty years of research have led to the identification of centrosome-, chromatin- and microtubule-mediated microtubule nucleation pathways that each contribute to mitotic spindle assembly. Far from being redundant pathways, data are now emerging regarding how they function together to ensure the timely completion of mitosis. We are also beginning to comprehend the multiple mechanisms by which cells regulate spindle scaling. Together, this research has increased our understanding of how cells coordinate hundreds of proteins to assemble the dynamic, precise and robust structure that is the mitotic spindle.
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69
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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.
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Affiliation(s)
- Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, the Rockefeller University, New York, NY 10065, USA.
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70
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Inoue D, Stemmer M, Thumberger T, Ruppert T, Bärenz F, Wittbrodt J, Gruss OJ. Expression of the novel maternal centrosome assembly factor Wdr8 is required for vertebrate embryonic mitoses. Nat Commun 2017; 8:14090. [PMID: 28098238 PMCID: PMC5253655 DOI: 10.1038/ncomms14090] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 11/29/2016] [Indexed: 02/07/2023] Open
Abstract
The assembly of the first centrosome occurs upon fertilisation when male centrioles recruit pericentriolar material (PCM) from the egg cytoplasm. The mechanisms underlying the proper assembly of centrosomes during early embryogenesis remain obscure. We identify Wdr8 as a novel maternally essential protein that is required for centrosome assembly during embryonic mitoses of medaka (Oryzias latipes). By CRISPR-Cas9-mediated knockout, maternal/zygotic Wdr8-null (m/zWdr8-/-) blastomeres exhibit severe defects in centrosome structure that lead to asymmetric division, multipolar mitotic spindles and chromosome alignment errors. Via its WD40 domains, Wdr8 interacts with the centriolar satellite protein SSX2IP. Combining targeted gene knockout and in vivo reconstitution of the maternally essential Wdr8-SSX2IP complex reveals an essential link between maternal centrosome proteins and the stability of the zygotic genome for accurate vertebrate embryogenesis. Our approach provides a way of distinguishing maternal from paternal effects in early embryos and should contribute to understanding molecular defects in human infertility.
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Affiliation(s)
- Daigo Inoue
- Centre for Organismal Studies (COS), Heidelberg University, Im Neuenheimer Feld 230, Heidelberg 69120, Germany
| | - Manuel Stemmer
- Centre for Organismal Studies (COS), Heidelberg University, Im Neuenheimer Feld 230, Heidelberg 69120, Germany
| | - Thomas Thumberger
- Centre for Organismal Studies (COS), Heidelberg University, Im Neuenheimer Feld 230, Heidelberg 69120, Germany
| | - Thomas Ruppert
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany
| | - Felix Bärenz
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany
| | - Joachim Wittbrodt
- Centre for Organismal Studies (COS), Heidelberg University, Im Neuenheimer Feld 230, Heidelberg 69120, Germany
| | - Oliver J Gruss
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany.,Institute of Genetics, University of Bonn, Karlrobert-Kreiten-Straße 13, Bonn 53115, Germany
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71
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Deficiency of RITA results in multiple mitotic defects by affecting microtubule dynamics. Oncogene 2016; 36:2146-2159. [DOI: 10.1038/onc.2016.372] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 08/08/2016] [Accepted: 08/28/2016] [Indexed: 01/31/2023]
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72
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Fang CT, Kuo HH, Pan TS, Yu FC, Yih LH. HSP70 regulates the function of mitotic centrosomes. Cell Mol Life Sci 2016; 73:3949-60. [PMID: 27137183 PMCID: PMC11108311 DOI: 10.1007/s00018-016-2236-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 04/16/2016] [Accepted: 04/21/2016] [Indexed: 10/21/2022]
Abstract
To establish a functional bipolar mitotic spindle, the centrosome expands and matures, acquiring enhanced activities for microtubule (MT) nucleation and assembly at the onset of mitosis. However, the regulatory mechanisms of centrosome maturation and MT assembly from the matured centrosome are largely unknown. In this study, we showed that heat shock protein (HSP) 70 considerably accumulates at the mitotic centrosome during prometaphase to metaphase and is required for bipolar spindle assembly. Inhibition or depletion of HSP70 impaired the function of mitotic centrosome and disrupted MT nucleation and polymerization from the spindle pole, and may thus result in formation of abnormal mitotic spindles. In addition, HSP70 may associate with NEDD1 and γ-tubulin, two pericentriolar material (PCM) components essential for centrosome maturation and MT nucleation. Loss of HSP70 function disrupted the interaction between NEDD1 and γ-tubulin, and reduced their accumulation at the mitotic centrosome. Our results thus demonstrate a role for HSP70 in regulating centrosome integrity during mitosis, and indicate that HSP70 is required for the maintenance of a functional mitotic centrosome that supports the assembly of a bipolar mitotic spindle.
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Affiliation(s)
- Chieh-Ting Fang
- Department of Life Science, National Taiwan University, Taipei, Taiwan
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, 115, Taiwan
| | - Hsiao-Hui Kuo
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, 115, Taiwan
| | - Tiffany S Pan
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, 115, Taiwan
| | - Fu-Chi Yu
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, 115, Taiwan
| | - Ling-Huei Yih
- Department of Life Science, National Taiwan University, Taipei, Taiwan.
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, 115, Taiwan.
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73
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Farache D, Jauneau A, Chemin C, Chartrain M, Rémy MH, Merdes A, Haren L. Functional Analysis of γ-Tubulin Complex Proteins Indicates Specific Lateral Association via Their N-terminal Domains. J Biol Chem 2016; 291:23112-23125. [PMID: 27660388 DOI: 10.1074/jbc.m116.744862] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Indexed: 11/06/2022] Open
Abstract
Microtubules are nucleated from multiprotein complexes containing γ-tubulin and associated γ-tubulin complex proteins (GCPs). Small complexes (γTuSCs) comprise two molecules of γ-tubulin bound to the C-terminal domains of GCP2 and GCP3. γTuSCs associate laterally into helical structures, providing a structural template for microtubule nucleation. In most eukaryotes γTuSCs associate with additional GCPs (4, 5, and 6) to form the core of the so-called γ-tubulin ring complex (γTuRC). GCPs 2-6 constitute a family of homologous proteins. Previous structural analysis and modeling of GCPs suggest that all family members can potentially integrate into the helical structure. Here we provide experimental evidence for this model. Using chimeric proteins in which the N- and C-terminal domains of different GCPs are swapped, we show that the N-terminal domains define the functional identity of GCPs, whereas the C-terminal domains are exchangeable. FLIM-FRET experiments indicate that GCP4 and GCP5 associate laterally within the complex, and their interaction is mediated by their N-terminal domains as previously shown for γTuSCs. Our results suggest that all GCPs are incorporated into the helix via lateral interactions between their N-terminal domains, whereas the C-terminal domains mediate longitudinal interactions with γ-tubulin. Moreover, we show that binding to γ-tubulin is not essential for integrating into the helical complex.
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Affiliation(s)
- Dorian Farache
- From the Centre de Biologie du Développement, CNRS-Université Toulouse III, 31062 Toulouse, France and
| | - Alain Jauneau
- Plateforme Imagerie-Microscopie, FR 3450 Pôle de Biotechnologie Végétale, 31326 Castanet-Tolosan, France
| | - Cécile Chemin
- From the Centre de Biologie du Développement, CNRS-Université Toulouse III, 31062 Toulouse, France and
| | - Marine Chartrain
- From the Centre de Biologie du Développement, CNRS-Université Toulouse III, 31062 Toulouse, France and
| | - Marie-Hélène Rémy
- From the Centre de Biologie du Développement, CNRS-Université Toulouse III, 31062 Toulouse, France and
| | - Andreas Merdes
- From the Centre de Biologie du Développement, CNRS-Université Toulouse III, 31062 Toulouse, France and
| | - Laurence Haren
- From the Centre de Biologie du Développement, CNRS-Université Toulouse III, 31062 Toulouse, France and
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74
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Bauer M, Cubizolles F, Schmidt A, Nigg EA. Quantitative analysis of human centrosome architecture by targeted proteomics and fluorescence imaging. EMBO J 2016; 35:2152-2166. [PMID: 27539480 PMCID: PMC5048348 DOI: 10.15252/embj.201694462] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 07/25/2016] [Indexed: 12/14/2022] Open
Abstract
Centrioles are essential for the formation of centrosomes and cilia. While numerical and/or structural centrosomes aberrations are implicated in cancer, mutations in centriolar and centrosomal proteins are genetically linked to ciliopathies, microcephaly, and dwarfism. The evolutionarily conserved mechanisms underlying centrosome biogenesis are centered on a set of key proteins, including Plk4, Sas-6, and STIL, whose exact levels are critical to ensure accurate reproduction of centrioles during cell cycle progression. However, neither the intracellular levels of centrosomal proteins nor their stoichiometry within centrosomes is presently known. Here, we have used two complementary approaches, targeted proteomics and EGFP-tagging of centrosomal proteins at endogenous loci, to measure protein abundance in cultured human cells and purified centrosomes. Our results provide a first assessment of the absolute and relative amounts of major components of the human centrosome. Specifically, they predict that human centriolar cartwheels comprise up to 16 stacked hubs and 1 molecule of STIL for every dimer of Sas-6. This type of quantitative information will help guide future studies of the molecular basis of centrosome assembly and function.
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Affiliation(s)
- Manuel Bauer
- Biozentrum, University of Basel, Basel, Switzerland
| | | | | | - Erich A Nigg
- Biozentrum, University of Basel, Basel, Switzerland
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75
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Cavazza T, Malgaretti P, Vernos I. The sequential activation of the mitotic microtubule assembly pathways favors bipolar spindle formation. Mol Biol Cell 2016; 27:2935-45. [PMID: 27489339 PMCID: PMC5042580 DOI: 10.1091/mbc.e16-05-0322] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 07/27/2016] [Indexed: 01/22/2023] Open
Abstract
A combination of experimental data obtained in somatic cells and Xenopus egg extracts and modeling suggests a novel function for centrosome maturation that balances the activity of the mitotic microtubule assembly pathways favoring bipolar spindle formation. Centrosome maturation is the process by which the duplicated centrosomes recruit pericentriolar components and increase their microtubule nucleation activity before mitosis. The role of this process in cells entering mitosis has been mostly related to the separation of the duplicated centrosomes and thereby to the assembly of a bipolar spindle. However, spindles can form without centrosomes. In fact, all cells, whether they have centrosomes or not, rely on chromatin-driven microtubule assembly to form a spindle. To test whether the sequential activation of these microtubule assembly pathways, defined by centrosome maturation and nuclear envelope breakdown, plays any role in spindle assembly, we combined experiments in tissue culture cells and Xenopus laevis egg extracts with a mathematical model. We found that interfering with the sequential activation of the microtubule assembly pathways compromises bipolar spindle assembly in tissue culture cells but not in X. laevis egg extracts. Our data suggest a novel function for centrosome maturation that determines the contribution of the chromosomal microtubule assembly pathway and favors bipolar spindle formation in most animal cells in which tubulin is in limiting amounts.
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Affiliation(s)
- Tommaso Cavazza
- Cell and Developmental Biology Programme, Centre for Genomic Regulation, Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Paolo Malgaretti
- Departament de Fisica Fonamental, Universitat de Barcelona, 08028 Barcelona, Spain Max-Planck-Institut für Intelligente Systeme and IV. Institut für Theoretische Physik, Universität Stuttgart, D-70569 Stuttgart, Germany
| | - Isabelle Vernos
- Cell and Developmental Biology Programme, Centre for Genomic Regulation, Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain Institució Catalana de Recerca I Estudis Avançats, 08010 Barcelona, Spain
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76
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An Amino-Terminal Polo Kinase Interaction Motif Acts in the Regulation of Centrosome Formation and Reveals a Novel Function for centrosomin (cnn) in Drosophila. Genetics 2016; 201:685-706. [PMID: 26447129 DOI: 10.1534/genetics.115.181842] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The formation of the pericentriolar matrix (PCM) and a fully functional centrosome in syncytial Drosophila melanogaster embryos requires the rapid transport of Cnn during initiation of the centrosome replication cycle. We show a Cnn and Polo kinase interaction is apparently required during embryogenesis and involves the exon 1A-initiating coding exon, suggesting a subset of Cnn splice variants is regulated by Polo kinase. During PCM formation exon 1A Cnn-Long Form proteins likely bind Polo kinase before phosphorylation by Polo for Cnn transport to the centrosome. Loss of either of these interactions in a portion of the total Cnn protein pool is sufficient to remove native Cnn from the pool, thereby altering the normal localization dynamics of Cnn to the PCM. Additionally, Cnn-Short Form proteins are required for polar body formation, a process known to require Polo kinase after the completion of meiosis. Exon 1A Cnn-LF and Cnn-SF proteins, in conjunction with Polo kinase, are required at the completion of meiosis and for the formation of functional centrosomes during early embryogenesis.
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77
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Non-centrosomal nucleation mediated by augmin organizes microtubules in post-mitotic neurons and controls axonal microtubule polarity. Nat Commun 2016; 7:12187. [PMID: 27405868 PMCID: PMC4947180 DOI: 10.1038/ncomms12187] [Citation(s) in RCA: 119] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 06/09/2016] [Indexed: 12/19/2022] Open
Abstract
Neurons display a highly polarized microtubule network that mediates trafficking throughout the extensive cytoplasm and is crucial for neuronal differentiation and function. In newborn migrating neurons, the microtubule network is organized by the centrosome. During neuron maturation, however, the centrosome gradually loses this activity, and how microtubules are organized in more mature neurons remains poorly understood. Here, we demonstrate that microtubule organization in post-mitotic neurons strongly depends on non-centrosomal nucleation mediated by augmin and by the nucleator γTuRC. Disruption of either complex not only reduces microtubule density but also microtubule bundling. These microtubule defects impair neurite formation, interfere with axon specification and growth, and disrupt axonal trafficking. In axons augmin does not merely mediate nucleation of microtubules but ensures their uniform plus end-out orientation. Thus, the augmin-γTuRC module, initially identified in mitotic cells, may be commonly used to generate and maintain microtubule configurations with specific polarity. In mature neurons the centrosome no longer functions as the main microtubule organizer and it is unclear how ordered microtubule arrays are assembled. Here, the authors show that in post-mitotic neurons this process depends on non-centrosomal nucleation mediated by the protein complex augmin and the nucleator gamma-TuRC.
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78
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Bury L, Coelho PA, Glover DM. From Meiosis to Mitosis: The Astonishing Flexibility of Cell Division Mechanisms in Early Mammalian Development. Curr Top Dev Biol 2016; 120:125-71. [PMID: 27475851 DOI: 10.1016/bs.ctdb.2016.04.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The execution of female meiosis and the establishment of the zygote is arguably the most critical stage of mammalian development. The egg can be arrested in the prophase of meiosis I for decades, and when it is activated, the spindle is assembled de novo. This spindle must function with the highest of fidelity and yet its assembly is unusually achieved in the absence of conventional centrosomes and with minimal influence of chromatin. Moreover, its dramatic asymmetric positioning is achieved through remarkable properties of the actin cytoskeleton to ensure elimination of the polar bodies. The second meiotic arrest marks a uniquely prolonged metaphase eventually interrupted by egg activation at fertilization to complete meiosis and mark a period of preparation of the male and female pronuclear genomes not only for their entry into the mitotic cleavage divisions but also for the imminent prospect of their zygotic expression.
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Affiliation(s)
- L Bury
- University of Cambridge, Cambridge, United Kingdom.
| | - P A Coelho
- University of Cambridge, Cambridge, United Kingdom
| | - D M Glover
- University of Cambridge, Cambridge, United Kingdom
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79
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Muroyama A, Seldin L, Lechler T. Divergent regulation of functionally distinct γ-tubulin complexes during differentiation. J Cell Biol 2016; 213:679-92. [PMID: 27298324 PMCID: PMC4915192 DOI: 10.1083/jcb.201601099] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 04/29/2016] [Indexed: 11/22/2022] Open
Abstract
Differentiation induces the formation of noncentrosomal microtubule arrays in diverse tissues. The formation of these arrays requires loss of microtubule-organizing activity (MTOC) at the centrosome, but the mechanisms regulating this transition remain largely unexplored. Here, we use the robust loss of centrosomal MTOC activity in the epidermis to identify two pools of γ-tubulin that are biochemically and functionally distinct and differentially regulated. Nucleation-competent CDK5RAP2-γ-tubulin complexes were maintained at centrosomes upon initial epidermal differentiation. In contrast, Nedd1-γ-tubulin complexes did not promote nucleation but were required for anchoring of microtubules, a previously uncharacterized activity for this complex. Cell cycle exit specifically triggered loss of Nedd1-γ-tubulin complexes, providing a mechanistic link connecting MTOC activity and differentiation. Collectively, our studies demonstrate that distinct γ-tubulin complexes regulate different microtubule behaviors at the centrosome and show that differential regulation of these complexes drives loss of centrosomal MTOC activity.
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Affiliation(s)
- Andrew Muroyama
- Department of Dermatology, Duke University Medical Center, Durham, NC 27710 Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
| | - Lindsey Seldin
- Department of Dermatology, Duke University Medical Center, Durham, NC 27710 Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
| | - Terry Lechler
- Department of Dermatology, Duke University Medical Center, Durham, NC 27710 Department of Cell Biology, Duke University Medical Center, Durham, NC 27710
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80
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Abstract
The mitotic spindle is made of microtubules (MTs) nucleated through different pathways involving the centrosomes, the chromosomes or the walls of pre-existing MTs. MCRS1 is a RanGTP target that specifically associates with the chromosome-driven MTs protecting them from MT depolymerases. MCRS1 is also needed for the control of kinetochore fiber (K-fiber) MT minus-ends dynamics in metaphase. Here, we investigated the regulation of MCRS1 activity in M-phase. We show that MCRS1 is phosphorylated by the Aurora-A kinase in mitosis on Ser35/36. Although this phosphorylation has no role on MCRS1 localization to chromosomal MTs and K-fiber minus-ends, we show that it regulates MCRS1 activity in mitosis. We conclude that Aurora-A activity is particularly important in the tuning of K-fiber minus-ends dynamics in mitosis.
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Affiliation(s)
- Sylvain Meunier
- a Center for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology , Barcelona , Spain.,b Universitat Pompeu Fabra (UPF) , Barcelona , Spain
| | - Krystal Timón
- a Center for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology , Barcelona , Spain.,b Universitat Pompeu Fabra (UPF) , Barcelona , Spain
| | - Isabelle Vernos
- a Center for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology , Barcelona , Spain.,b Universitat Pompeu Fabra (UPF) , Barcelona , Spain.,c Insitució Catalana de Recerca i Estudis Avançats (ICREA) , Barcelona , Spain
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81
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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.
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Affiliation(s)
- Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544-1014;
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82
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Chu CW, Ossipova O, Ioannou A, Sokol SY. Prickle3 synergizes with Wtip to regulate basal body organization and cilia growth. Sci Rep 2016; 6:24104. [PMID: 27062996 PMCID: PMC4827067 DOI: 10.1038/srep24104] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 03/21/2016] [Indexed: 12/21/2022] Open
Abstract
PCP proteins maintain planar polarity in many epithelial tissues and have been implicated in cilia development in vertebrate embryos. In this study we examine Prickle3 (Pk3), a vertebrate homologue of Drosophila Prickle, in Xenopus gastrocoel roof plate (GRP). GRP is a tissue equivalent to the mouse node, in which cilia-generated flow promotes left-right patterning. We show that Pk3 is enriched at the basal body of GRP cells but is recruited by Vangl2 to anterior cell borders. Interference with Pk3 function disrupted the anterior polarization of endogenous Vangl2 and the posterior localization of cilia in GRP cells, demonstrating its role in PCP. Strikingly, in cells with reduced Pk3 activity, cilia growth was inhibited and γ-tubulin and Nedd1 no longer associated with the basal body, suggesting that Pk3 has a novel function in basal body organization. Mechanistically, this function of Pk3 may involve Wilms tumor protein 1-interacting protein (Wtip), which physically associates with and cooperates with Pk3 to regulate ciliogenesis. We propose that, in addition to cell polarity, PCP components control basal body organization and function.
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Affiliation(s)
- Chih-Wen Chu
- Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Olga Ossipova
- Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Andriani Ioannou
- Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Sergei Y Sokol
- Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
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Intra-spindle Microtubule Assembly Regulates Clustering of Microtubule-Organizing Centers during Early Mouse Development. Cell Rep 2016; 15:54-60. [PMID: 27052165 DOI: 10.1016/j.celrep.2016.02.087] [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: 09/30/2015] [Revised: 01/14/2016] [Accepted: 02/24/2016] [Indexed: 11/20/2022] Open
Abstract
Errors during cell division in oocytes and early embryos are linked to birth defects in mammals. Bipolar spindle assembly in early mouse embryos is unique in that three or more acentriolar microtubule-organizing centers (MTOCs) are initially formed and are then clustered into two spindle poles. Using a knockout mouse and live imaging of spindles in embryos, we demonstrate that MTOC clustering during the blastocyst stage requires augmin, a critical complex for MT-dependent MT nucleation within the spindle. Functional analyses in cultured cells with artificially increased numbers of centrosomes indicate that the lack of intra-spindle MT nucleation, but not loss of augmin per se or overall reduction of spindle MTs, is the cause of clustering failure. These data suggest that onset of mitosis with three or more MTOCs is turned into a typical bipolar division through augmin-dependent intra-spindle MT assembly.
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84
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GIT1/βPIX signaling proteins and PAK1 kinase regulate microtubule nucleation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:1282-97. [PMID: 27012601 DOI: 10.1016/j.bbamcr.2016.03.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 03/14/2016] [Accepted: 03/18/2016] [Indexed: 12/13/2022]
Abstract
Microtubule nucleation from γ-tubulin complexes, located at the centrosome, is an essential step in the formation of the microtubule cytoskeleton. However, the signaling mechanisms that regulate microtubule nucleation in interphase cells are largely unknown. In this study, we report that γ-tubulin is in complexes containing G protein-coupled receptor kinase-interacting protein 1 (GIT1), p21-activated kinase interacting exchange factor (βPIX), and p21 protein (Cdc42/Rac)-activated kinase 1 (PAK1) in various cell lines. Immunofluorescence microscopy revealed association of GIT1, βPIX and activated PAK1 with centrosomes. Microtubule regrowth experiments showed that depletion of βPIX stimulated microtubule nucleation, while depletion of GIT1 or PAK1 resulted in decreased nucleation in the interphase cells. These data were confirmed for GIT1 and βPIX by phenotypic rescue experiments, and counting of new microtubules emanating from centrosomes during the microtubule regrowth. The importance of PAK1 for microtubule nucleation was corroborated by the inhibition of its kinase activity with IPA-3 inhibitor. GIT1 with PAK1 thus represent positive regulators, and βPIX is a negative regulator of microtubule nucleation from the interphase centrosomes. The regulatory roles of GIT1, βPIX and PAK1 in microtubule nucleation correlated with recruitment of γ-tubulin to the centrosome. Furthermore, in vitro kinase assays showed that GIT1 and βPIX, but not γ-tubulin, serve as substrates for PAK1. Finally, direct interaction of γ-tubulin with the C-terminal domain of βPIX and the N-terminal domain of GIT1, which targets this protein to the centrosome, was determined by pull-down experiments. We propose that GIT1/βPIX signaling proteins with PAK1 kinase represent a novel regulatory mechanism of microtubule nucleation in interphase cells.
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85
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Uehara R, Kamasaki T, Hiruma S, Poser I, Yoda K, Yajima J, Gerlich DW, Goshima G. Augmin shapes the anaphase spindle for efficient cytokinetic furrow ingression and abscission. Mol Biol Cell 2016; 27:812-27. [PMID: 26764096 PMCID: PMC4803307 DOI: 10.1091/mbc.e15-02-0101] [Citation(s) in RCA: 17] [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: 02/23/2015] [Revised: 01/05/2016] [Accepted: 01/07/2016] [Indexed: 11/11/2022] Open
Abstract
During anaphase, distinct populations of microtubules (MTs) form by either centrosome-dependent or augmin-dependent nucleation. It remains largely unknown whether these different MT populations contribute distinct functions to cytokinesis. Here we show that augmin-dependent MTs are required for the progression of both furrow ingression and abscission. Augmin depletion reduced the accumulation of anillin, a contractile ring regulator at the cell equator, yet centrosomal MTs were sufficient to mediate RhoA activation at the furrow. This defect in contractile ring organization, combined with incomplete spindle pole separation during anaphase, led to impaired furrow ingression. During the late stages of cytokinesis, astral MTs formed bundles in the intercellular bridge, but these failed to assemble a focused midbody structure and did not establish tight linkage to the plasma membrane, resulting in furrow regression. Thus augmin-dependent acentrosomal MTs and centrosomal MTs contribute to nonredundant targeting mechanisms of different cytokinesis factors, which are required for the formation of a functional contractile ring and midbody.
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Affiliation(s)
- Ryota Uehara
- Creative Research Institution, Hokkaido University, Sapporo 001-0021, Japan Department of Life Sciences, School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Tomoko Kamasaki
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Shota Hiruma
- Creative Research Institution, Hokkaido University, Sapporo 001-0021, Japan
| | - Ina Poser
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Kinya Yoda
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Junichiro Yajima
- Department of Life Sciences, School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan
| | - Daniel W Gerlich
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna Biocenter Campus, 1030 Vienna, Austria
| | - Gohta Goshima
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
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86
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Abstract
Microtubules mediate important cellular processes by forming highly ordered arrays. Organization of these networks is achieved by nucleating and anchoring microtubules at centrosomes and other structures collectively known as microtubule-organizing centers (MTOCs). However, the diverse microtubule configurations found in different cell types may not be generated and maintained by MTOCs alone. Work over the last few years has revealed a mechanism that has the capacity to generate cell-type-specific microtubule arrays independently of a specific organizer: nucleation of microtubules from the lateral surface of pre-existing microtubules. This type of nucleation requires cooperation between two different multi-subunit protein complexes, augmin and the γ-tubulin ring complex (γTuRC). Here we review recent molecular insight into microtubule-dependent nucleation and discuss the possibility that the augmin-γTuRC module, initially described in mitosis, may broadly contribute to microtubule organization also in non-mitotic cells.
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Affiliation(s)
- Carlos Sánchez-Huertas
- Institute for Research in Biomedicine (IRB Barcelona), C/ Baldiri Reixac 10, Barcelona, Spain
| | - Jens Lüders
- Institute for Research in Biomedicine (IRB Barcelona), C/ Baldiri Reixac 10, Barcelona, Spain.
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87
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Cota RR, Teixidó-Travesa N, Ezquerra A, Eibes S, Lacasa C, Roig J, Lüders J. MZT1 regulates microtubule nucleation by linking γTuRC assembly to adapter-mediated targeting and activation. J Cell Sci 2016; 130:406-419. [DOI: 10.1242/jcs.195321] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 11/09/2016] [Indexed: 01/22/2023] Open
Abstract
Regulation of the γ-tubulin ring complex (γTuRC) through targeting and activation restricts nucleation of microtubules to microtubule organizing centers (MTOCs), aiding in the assembly of ordered microtubule arrays. However, the mechanistic basis of this important regulation remains poorly understood. Here we show that in human cells γTuRC integrity, determined by the presence of γ-tubulin complex proteins (GCPs) 2-6, is a prerequisite for interaction with the targeting factor NEDD1, impacting on essentially all γ-tubulin dependent functions. Recognition of γTuRC integrity is mediated by MZT1, which binds not only to the GCP3 subunit as previously shown, but cooperatively also to other GCPs through a conserved hydrophobic motif present in the N-termini of GCP2, GCP3, GCP5, and GCP6. MZT1 knockdown causes severe cellular defects under conditions that leave γTuRC intact, suggesting that the essential function of MZT1 is not in γTuRC assembly. Instead, MZT1 specifically binds fully assembled γTuRC to enable interaction with NEDD1 for targeting, and with the CM1 domain of CDK5RAP2 for stimulating nucleation activity. Thus, MZT1 is a ‘priming factor’ for the γTuRC that allows spatial regulation of nucleation.
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Affiliation(s)
- Rosa Ramírez Cota
- Institute for Research in Biomedicine (IRB Barcelona), 08028 Barcelona, Spain
| | | | - Artur Ezquerra
- Institute for Research in Biomedicine (IRB Barcelona), 08028 Barcelona, Spain
| | - Susana Eibes
- Institute for Research in Biomedicine (IRB Barcelona), 08028 Barcelona, Spain
| | - Cristina Lacasa
- Institute for Research in Biomedicine (IRB Barcelona), 08028 Barcelona, Spain
| | - Joan Roig
- Institute for Research in Biomedicine (IRB Barcelona), 08028 Barcelona, Spain
- Molecular Biology Institute of Barcelona (IBMB-CSIC), 08028 Barcelona, Spain
| | - Jens Lüders
- Institute for Research in Biomedicine (IRB Barcelona), 08028 Barcelona, Spain
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88
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The γ-tubulin-specific inhibitor gatastatin reveals temporal requirements of microtubule nucleation during the cell cycle. Nat Commun 2015; 6:8722. [PMID: 26503935 PMCID: PMC4640066 DOI: 10.1038/ncomms9722] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 09/24/2015] [Indexed: 11/26/2022] Open
Abstract
Inhibitors of microtubule (MT) assembly or dynamics that target α/β-tubulin are widely exploited in cancer therapy and biological research. However, specific inhibitors of the MT nucleator γ-tubulin that would allow testing temporal functions of γ-tubulin during the cell cycle are yet to be identified. By evolving β-tubulin-binding drugs we now find that the glaziovianin A derivative gatastatin is a γ-tubulin-specific inhibitor. Gatastatin decreased interphase MT dynamics of human cells without affecting MT number. Gatastatin inhibited assembly of the mitotic spindle in prometaphase. Addition of gatastatin to preformed metaphase spindles altered MT dynamics, reduced the number of growing MTs and shortened spindle length. Furthermore, gatastatin prolonged anaphase duration by affecting anaphase spindle structure, indicating the continuous requirement of MT nucleation during mitosis. Thus, gatastatin facilitates the dissection of the role of γ-tubulin during the cell cycle and reveals the sustained role of γ-tubulin. Current microtubule inhibitors target α/β-tubulin, but no specific inhibitor of γ-tubulin has been developed. Here the authors present gatastatin as a γ-tubulin inhibitor and use it to probe the role of γ-tubulin during the cell cycle.
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89
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Yeh C, Coyaud É, Bashkurov M, van der Lelij P, Cheung SWT, Peters JM, Raught B, Pelletier L. The Deubiquitinase USP37 Regulates Chromosome Cohesion and Mitotic Progression. Curr Biol 2015; 25:2290-9. [PMID: 26299517 DOI: 10.1016/j.cub.2015.07.025] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 06/08/2015] [Accepted: 07/09/2015] [Indexed: 12/31/2022]
Abstract
A bipolar mitotic spindle facilitates the equal segregation of chromosomes to two daughter cells. To achieve bipolar attachment of microtubules to kinetochores of sister chromatids, chromatids must remain paired after replication. This cohesion is mediated by the conserved cohesin complex comprised of SMC1, SMC3, SCC1, and either SA1 or SA2 in humans. Because defects in spindle assembly or sister chromatid cohesion can lead to aneuploidy in daughter cells, proper regulation of these processes is essential for fidelity in chromosome segregation. In an RNAi screen for regulators of spindle assembly, we identify the deubiquitinase USP37 as a regulator of mitotic progression, centrosome integrity, and chromosome alignment. USP37 associates with cohesin and contributes to sister chromatid resolution. Cohesion defects are rescued by expression of an RNAi-resistant USP37, but not the catalytically impaired USP37(C350A) mutant. Further, USP37 associates with WAPL, a negative regulator of cohesion necessary for cohesin release in prophase, in a manner dependent on USP37's second and third ubiquitin-interacting motifs. Depletion of USP37 reduces the stability of chromatin-associated WAPL and increases the fraction of WAPL that is more heavily ubiquitylated in mitosis. Consistently, overexpression of USP37(C350A) results in increased modification of WAPL, and addition of purified USP37(WT), but not USP37(C350A), to WAPL immunoprecipitates results in a reduction of ubiquitylated products. Taken together, our results ascribe a novel function for USP37 in mitotic progression and further suggest that USP37 positively regulates the stability of chromatin-associated WAPL to facilitate sister chromatid resolution.
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Affiliation(s)
- Christina Yeh
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, ON M5G 1X5, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Étienne Coyaud
- Princess Margaret Cancer Centre, University Health Network, 101 College Street, Toronto, ON M5G 1L7, Canada
| | - Mikhail Bashkurov
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, ON M5G 1X5, Canada
| | - Petra van der Lelij
- Research Institute of Molecular Pathology (IMP), Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Sally W T Cheung
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, ON M5G 1X5, Canada
| | - Jan Michael Peters
- Research Institute of Molecular Pathology (IMP), Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Brian Raught
- Princess Margaret Cancer Centre, University Health Network, 101 College Street, Toronto, ON M5G 1L7, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Laurence Pelletier
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, ON M5G 1X5, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada.
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90
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91
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Microtubule-associated proteins control the kinetics of microtubule nucleation. Nat Cell Biol 2015; 17:907-16. [PMID: 26098575 DOI: 10.1038/ncb3188] [Citation(s) in RCA: 141] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 05/14/2015] [Indexed: 02/07/2023]
Abstract
Microtubules are born and reborn continuously, even during quiescence. These polymers are nucleated from templates, namely γ-tubulin ring complexes (γ-TuRCs) and severed microtubule ends. Using single-molecule biophysics, we show that nucleation from γ-TuRCs, axonemes and seed microtubules requires tubulin concentrations that lie well above the critical concentration. We measured considerable time lags between the arrival of tubulin and the onset of steady-state elongation. Microtubule-associated proteins (MAPs) alter these time lags. Catastrophe factors (MCAK and EB1) inhibited nucleation, whereas a polymerase (XMAP215) and an anti-catastrophe factor (TPX2) promoted nucleation. We observed similar phenomena in cells. We conclude that GTP hydrolysis inhibits microtubule nucleation by destabilizing the nascent plus ends required for persistent elongation. Our results explain how MAPs establish the spatial and temporal profile of microtubule nucleation.
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92
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A sensitised RNAi screen reveals a ch-TOG genetic interaction network required for spindle assembly. Sci Rep 2015; 5:10564. [PMID: 26037491 PMCID: PMC4453164 DOI: 10.1038/srep10564] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Accepted: 04/20/2015] [Indexed: 02/06/2023] Open
Abstract
How multiple spindle assembly pathways are integrated to drive bipolar spindle assembly is poorly understood. We performed an image-based double RNAi screen to identify genes encoding Microtubule-Associated Proteins (MAPs) that interact with the highly conserved ch-TOG gene to regulate bipolar spindle assembly in human cells. We identified a ch-TOG centred network of genetic interactions which promotes ensures centrosome-mediated microtubule polymerisation, leading to the incorporation of microtubules polymerised by all pathways into a bipolar structure. Our genetic screen also reveals that ch-TOG maintains a dynamic microtubule population, in part, through modulating HSET activity. ch-TOG ensures that spindle assembly is robust to perturbation but sufficiently dynamic such that spindles can explore a diverse shape space in search of structures that can align chromosomes.
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93
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Peng Y, Moritz M, Han X, Giddings TH, Lyon A, Kollman J, Winey M, Yates J, Agard DA, Drubin DG, Barnes G. Interaction of CK1δ with γTuSC ensures proper microtubule assembly and spindle positioning. Mol Biol Cell 2015; 26:2505-18. [PMID: 25971801 PMCID: PMC4571304 DOI: 10.1091/mbc.e14-12-1627] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 05/04/2015] [Indexed: 01/09/2023] Open
Abstract
Casein kinase 1δ (CK1δ) family members associate with microtubule-organizing centers from yeast to humans. Budding yeast CK1δ, Hrr25, directly phosphorylated γTuSC proteins in vivo and in vitro, and this phosphorylation promoted δTuSC integrity and activity in biochemical assays. Casein kinase 1δ (CK1δ) family members associate with microtubule-organizing centers (MTOCs) from yeast to humans, but their mitotic roles and targets have yet to be identified. We show here that budding yeast CK1δ, Hrr25, is a γ-tubulin small complex (γTuSC) binding factor. Moreover, Hrr25's association with γTuSC depends on its kinase activity and its noncatalytic central domain. Loss of Hrr25 kinase activity resulted in assembly of unusually long cytoplasmic microtubules and defects in spindle positioning, consistent with roles in regulation of γTuSC-mediated microtubule nucleation and the Kar9 spindle-positioning pathway, respectively. Hrr25 directly phosphorylated γTuSC proteins in vivo and in vitro, and this phosphorylation promoted γTuSC integrity and activity. Because CK1δ and γTuSC are highly conserved and present at MTOCs in diverse eukaryotes, similar regulatory mechanisms are expected to apply generally in eukaryotes.
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Affiliation(s)
- Yutian Peng
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Michelle Moritz
- Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158
| | - Xuemei Han
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037
| | - Thomas H Giddings
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Boulder, CO 80309
| | - Andrew Lyon
- Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158
| | - Justin Kollman
- Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158
| | - Mark Winey
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Boulder, CO 80309
| | - John Yates
- Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037
| | - David A Agard
- Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158
| | - David G Drubin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Georjana Barnes
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
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94
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Targeting of γ-tubulin complexes to microtubule organizing centers: conservation and divergence. Trends Cell Biol 2015; 25:296-307. [DOI: 10.1016/j.tcb.2014.12.002] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 11/25/2014] [Accepted: 12/01/2014] [Indexed: 11/29/2022]
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95
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Ritter A, Sanhaji M, Steinhäuser K, Roth S, Louwen F, Yuan J. The activity regulation of the mitotic centromere-associated kinesin by Polo-like kinase 1. Oncotarget 2015; 6:6641-55. [PMID: 25504441 PMCID: PMC4466640 DOI: 10.18632/oncotarget.2843] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 12/01/2014] [Indexed: 01/10/2023] Open
Abstract
The mitotic centromere-associated kinesin (MCAK), a potent microtubule depolymerase, is involved in regulating microtubule dynamics. The activity and subcellular localization of MCAK are tightly regulated by key mitotic kinases, such as Polo-like kinase 1 (Plk1) by phosphorylating multiple residues in MCAK. Since Plk1 phosphorylates very often different residues of substrates at different stages, we have dissected individual phosphorylation of MCAK by Plk1 and characterized its function in more depth. We have recently shown that S621 in MCAK is the major phosphorylation site of Plk1, which is responsible for regulating MCAK's degradation by promoting the association of MCAK with APC/CCdc20. In the present study, we have addressed another two residues phosphorylated by Plk1, namely S632/S633 in the C-terminus of MCAK. Our data suggest that Plk1 phosphorylates S632/S633 and regulates its catalytic activity in mitosis. This phosphorylation is required for proper spindle assembly during early phases of mitosis. The subsequent dephosphorylation of S632/S633 might be necessary to timely align the chromosomes onto the metaphase plate. Therefore, our studies suggest new mechanisms by which Plk1 regulates MCAK: the degradation of MCAK is controlled by Plk1 phosphorylation on S621, whereas its activity is modulated by Plk1 phosphorylation on S632/S633 in mitosis.
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Affiliation(s)
- Andreas Ritter
- Department of Gynecology and Obstetrics, School of Medicine, J. W. Goethe-University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
| | - Mourad Sanhaji
- Department of Gynecology and Obstetrics, School of Medicine, J. W. Goethe-University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
- Present address: University Hospital Jena, Institute for Diagnostic and Interventional Radiology, Experimental Radiology, Erlanger Allee 101, 07747 Jena, Germany
| | - Kerstin Steinhäuser
- Department of Gynecology and Obstetrics, School of Medicine, J. W. Goethe-University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
| | - Susanne Roth
- Department of Gynecology and Obstetrics, School of Medicine, J. W. Goethe-University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
| | - Frank Louwen
- Department of Gynecology and Obstetrics, School of Medicine, J. W. Goethe-University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
| | - Juping Yuan
- Department of Gynecology and Obstetrics, School of Medicine, J. W. Goethe-University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
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96
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Abstract
A shared feature among all microtubule (MT)-dependent processes is the requirement for MTs to be organized in arrays of defined geometry. At a fundamental level, this is achieved by precisely controlling the timing and localization of the nucleation events that give rise to new MTs. To this end, MT nucleation is restricted to specific subcellular sites called MT-organizing centres. The primary MT-organizing centre in proliferating animal cells is the centrosome. However, the discovery of MT nucleation capacity of the Golgi apparatus (GA) has substantially changed our understanding of MT network organization in interphase cells. Interestingly, MT nucleation at the Golgi apparently relies on multiprotein complexes, similar to those present at the centrosome, that assemble at the cis-face of the organelle. In this process, AKAP450 plays a central role, acting as a scaffold to recruit other centrosomal proteins important for MT generation. MT arrays derived from either the centrosome or the GA differ in their geometry, probably reflecting their different, yet complementary, functions. Here, I review our current understanding of the molecular mechanisms involved in MT nucleation at the GA and how Golgi- and centrosome-based MT arrays work in concert to ensure the formation of a pericentrosomal polarized continuous Golgi ribbon structure, a critical feature for cell polarity in mammalian cells. In addition, I comment on the important role of the Golgi-nucleated MTs in organizing specialized MT arrays that serve specific functions in terminally differentiated cells.
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Affiliation(s)
- Rosa M Rios
- Cell Signalling Department, CABIMER-CSIC, Seville 41092, Spain
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97
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Sulimenko V, Hájková Z, Černohorská M, Sulimenko T, Sládková V, Dráberová L, Vinopal S, Dráberová E, Dráber P. Microtubule Nucleation in Mouse Bone Marrow–Derived Mast Cells Is Regulated by the Concerted Action of GIT1/βPIX Proteins and Calcium. THE JOURNAL OF IMMUNOLOGY 2015; 194:4099-111. [DOI: 10.4049/jimmunol.1402459] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 02/27/2015] [Indexed: 11/19/2022]
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98
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Wolniak SM, Boothby TC, van der Weele CM. Posttranscriptional control over rapid development and ciliogenesis in Marsilea. Methods Cell Biol 2015; 127:403-44. [PMID: 25837402 DOI: 10.1016/bs.mcb.2015.01.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Marsilea vestita is a semiaquatic fern that produces its spores (meiotic products) as it undergoes a process of natural desiccation. During the period of desiccation, the spores mature, and produce large quantities of pre-mRNA, which is partially processed and stored in nuclear speckles and can remain stable during a period of extended quiescence in the dry spore. Rehydration of the spores initiates a highly coordinated developmental program, featuring nine successive mitotic division cycles that occur at precise times and in precise planes within the spore wall to produce 39 cells, 32 of which are spermatids. The spermatids then undergo de novo basal body formation, the assembly of a massive cytoskeleton, nuclear and cell elongation, and finally ciliogenesis, before being released from the spore wall. The entire developmental program requires only 11 h to reach completion, and is synchronous in a population of spores rehydrated at the same time. Rapid development in this endosporic gametophyte is controlled posttranscriptionally, where stored pre-mRNAs, many of which are intron-retaining transcripts, are unmasked, processed, and translated under tight spatial and temporal control. Here, we describe posttranscriptional mechanisms that exert temporal and spatial control over this developmental program, which culminates in the production of ∼140 ciliary axonemes in each spermatozoid.
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Affiliation(s)
- Stephen M Wolniak
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park MD 20742, USA
| | - Thomas C Boothby
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park MD 20742, USA
| | - Corine M van der Weele
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park MD 20742, USA
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99
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Centrosome maturation requires YB-1 to regulate dynamic instability of microtubules for nucleus reassembly. Sci Rep 2015; 5:8768. [PMID: 25740062 PMCID: PMC4350100 DOI: 10.1038/srep08768] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 01/29/2015] [Indexed: 12/18/2022] Open
Abstract
Microtubule formation from the centrosome increases dramatically at the onset of mitosis. This process is termed centrosome maturation. However, regulatory mechanisms of microtubule assembly from the centrosome in response to the centrosome maturation are largely unknown. Here we found that YB-1, a cellular cancer susceptibility protein, is required for the centrosome maturation. Phosphorylated YB-1 accumulated in the centrosome at mitotic phase. By YB-1 knockdown, microtubules were found detached from the centrosome at telophase and an abnormal nuclear shape called nuclear lobulation was found due to defective reassembly of nuclear envelope by mis-localization of non-centrosomal microtubules. In conclusion, we propose that YB-1 is important for the assembly of centrosomal microtubule array for temporal and spatial regulation of microtubules.
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Keerthisinghe S, Nadeau JA, Lucas JR, Nakagawa T, Sack FD. The Arabidopsis leucine-rich repeat receptor-like kinase MUSTACHES enforces stomatal bilateral symmetry in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 81:684-94. [PMID: 25594156 DOI: 10.1111/tpj.12757] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 12/12/2014] [Accepted: 12/22/2014] [Indexed: 05/09/2023]
Abstract
Stomata display a mirror-like symmetry that is adaptive for shoot/atmosphere gas exchange. This symmetry includes the facing guard cells around a lens-shaped and bilaterally symmetric pore, as well as radially arranged microtubule arrays that primarily originate at the pore and then grow outwards. Mutations in MUSTACHES (MUS), which encodes a leucine-rich repeat receptor-like kinase, disrupt this symmetry, resulting in defects ranging from skewed pores and abnormally focused and depolarized radial microtubule arrays, to paired guard cells that face away from each other, or a severe loss of stomatal shape. Translational MUSproMUS:tripleGFP fusions are expressed in cell plates in most cells types in roots and shoots, and cytokinesis and cell plates are mostly normal in mus mutants. However, in guard mother cells, which divide and then form stomata, MUS expression is notably absent from new cell plates, and instead is peripherally located. These results are consistent with a role for MUS in enforcing wall building and cytoskeletal polarity at the centre of the developing stoma via signalling from the vicinity of the guard cell membrane.
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Affiliation(s)
- Sandra Keerthisinghe
- Botany Department, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
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