1
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Martins CS, Taveneau C, Castro-Linares G, Baibakov M, Buzhinsky N, Eroles M, Milanović V, Omi S, Pedelacq JD, Iv F, Bouillard L, Llewellyn A, Gomes M, Belhabib M, Kuzmić M, Verdier-Pinard P, Lee S, Badache A, Kumar S, Chandre C, Brasselet S, Rico F, Rossier O, Koenderink GH, Wenger J, Cabantous S, Mavrakis M. Human septins organize as octamer-based filaments and mediate actin-membrane anchoring in cells. J Cell Biol 2023; 222:213778. [PMID: 36562751 PMCID: PMC9802686 DOI: 10.1083/jcb.202203016] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 10/20/2022] [Accepted: 12/01/2022] [Indexed: 12/24/2022] Open
Abstract
Septins are cytoskeletal proteins conserved from algae and protists to mammals. A unique feature of septins is their presence as heteromeric complexes that polymerize into filaments in solution and on lipid membranes. Although animal septins associate extensively with actin-based structures in cells, whether septins organize as filaments in cells and if septin organization impacts septin function is not known. Customizing a tripartite split-GFP complementation assay, we show that all septins decorating actin stress fibers are octamer-containing filaments. Depleting octamers or preventing septins from polymerizing leads to a loss of stress fibers and reduced cell stiffness. Super-resolution microscopy revealed septin fibers with widths compatible with their organization as paired septin filaments. Nanometer-resolved distance measurements and single-protein tracking further showed that septin filaments are membrane bound and largely immobilized. Finally, reconstitution assays showed that septin filaments mediate actin-membrane anchoring. We propose that septin organization as octamer-based filaments is essential for septin function in anchoring and stabilizing actin filaments at the plasma membrane.
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Affiliation(s)
- Carla Silva Martins
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France.,Centre de Recherche en Cancérologie de Toulouse (CRCT), INSERM, Université de Toulouse, UPS, CNRS, Toulouse, France
| | - Cyntia Taveneau
- Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia
| | - Gerard Castro-Linares
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands
| | - Mikhail Baibakov
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France
| | - Nicolas Buzhinsky
- CNRS, INSERM, LAI, Turing Centre for Living Systems, Aix-Marseille Univ, Marseille, France>
| | - Mar Eroles
- CNRS, INSERM, LAI, Turing Centre for Living Systems, Aix-Marseille Univ, Marseille, France>
| | - Violeta Milanović
- University Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR, Bordeaux, France
| | - Shizue Omi
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France
| | - Jean-Denis Pedelacq
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III-Paul Sabatier (UPS), Toulouse, France
| | - Francois Iv
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France
| | - Léa Bouillard
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France
| | - Alexander Llewellyn
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France
| | - Maxime Gomes
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France
| | - Mayssa Belhabib
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France
| | - Mira Kuzmić
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, Marseille, France
| | - Pascal Verdier-Pinard
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, Marseille, France
| | - Stacey Lee
- Department of Bioengineering, University of California, Berkeley, CA, USA
| | - Ali Badache
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, Marseille, France
| | - Sanjay Kumar
- Department of Bioengineering, University of California, Berkeley, CA, USA
| | | | - Sophie Brasselet
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France
| | - Felix Rico
- CNRS, INSERM, LAI, Turing Centre for Living Systems, Aix-Marseille Univ, Marseille, France>
| | - Olivier Rossier
- University Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR, Bordeaux, France
| | - Gijsje H Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands
| | - Jerome Wenger
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France
| | - Stéphanie Cabantous
- Centre de Recherche en Cancérologie de Toulouse (CRCT), INSERM, Université de Toulouse, UPS, CNRS, Toulouse, France
| | - Manos Mavrakis
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France
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2
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Abstract
How cells move is a fundamental biological question. The directionality of adherent migrating cells depends on the assembly and disassembly (turnover) of focal adhesions (FAs). FAs are micron-sized actin-based structures that link cells to the extracellular matrix. Traditionally, microtubules have been considered key to triggering FA turnover. Through the years, advancements in biochemistry, biophysics, and bioimaging tools have been invaluable for many research groups to unravel a variety of mechanisms and molecular players that contribute to FA turnover, beyond microtubules. Here, we discuss recent discoveries of key molecular players that affect the dynamics and organization of the actin cytoskeleton to enable timely FA turnover and consequently proper directed cell migration.
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Affiliation(s)
- Manos Mavrakis
- Institut Fresnel, CNRS, Aix-Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - M Angeles Juanes
- School of Health and Life Science, Teesside University, Middlesbrough, TS1 3BX, United Kingdom; National Horizons Centre, Teesside University, Darlington DL1 1HG, United Kingdom; Centro de Investigación Príncipe Felipe, Valencia, 46012, Spain.
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3
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Chauvin B, Nakazawa K, Beber A, Di Cicco A, Hajj B, Iv F, Mavrakis M, Koenderink GH, Cabral JT, Trichet M, Mangenot S, Bertin A. Bottom-Up <em>In Vitro</em> Methods to Assay the Ultrastructural Organization, Membrane Reshaping, and Curvature Sensitivity Behavior of Septins. J Vis Exp 2022. [DOI: 10.3791/63889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
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4
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Castro-linares G, den Haan J, Iv F, Silva Martins C, Bertin A, Mavrakis M, Koenderink GH. Purification and Quality Control of Recombinant Septin Complexes for Cell-Free Reconstitution. J Vis Exp 2022. [DOI: 10.3791/63871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
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5
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Arbizzani F, Mavrakis M, Hoya M, Ribas JC, Brasselet S, Paoletti A, Rincon SA. Septin filament compaction into rings requires the anillin Mid2 and contractile ring constriction. Cell Rep 2022; 39:110722. [PMID: 35443188 DOI: 10.1016/j.celrep.2022.110722] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 02/10/2022] [Accepted: 03/30/2022] [Indexed: 11/19/2022] Open
Abstract
Septin filaments assemble into high-order molecular structures that associate with membranes, acting as diffusion barriers and scaffold proteins crucial for many cellular processes. How septin filaments organize in such structures is still not understood. Here, we used fission yeast to explore septin filament organization during cell division and its cell cycle regulation. Live-imaging and polarization microscopy analysis uncovered that septin filaments are initially recruited as a diffuse meshwork surrounding the acto-myosin contractile ring (CR) in anaphase, which undergoes compaction into two rings when CR constriction is initiated. We found that the anillin-like protein Mid2 is necessary to promote this compaction step, possibly acting as a bundler for septin filaments. Moreover, Mid2-driven septin compaction requires inputs from the septation initiation network as well as CR constriction and the β(1,3)-glucan synthase Bgs1. This work highlights that anillin-mediated septin ring assembly is under strict cell cycle control.
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Affiliation(s)
| | - Manos Mavrakis
- Aix Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, UMR 7249, 13013 Marseille, France
| | - Marta Hoya
- Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca, 37007 Salamanca, Spain
| | - Juan Carlos Ribas
- Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca, 37007 Salamanca, Spain
| | - Sophie Brasselet
- Aix Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, UMR 7249, 13013 Marseille, France
| | - Anne Paoletti
- Institut Curie, PSL University, CNRS UMR 144, 75005 Paris, France.
| | - Sergio A Rincon
- Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca, 37007 Salamanca, Spain.
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6
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Rimoli CV, Valades-Cruz CA, Curcio V, Mavrakis M, Brasselet S. 4polar-STORM polarized super-resolution imaging of actin filament organization in cells. Nat Commun 2022; 13:301. [PMID: 35027553 PMCID: PMC8758668 DOI: 10.1038/s41467-022-27966-w] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 12/20/2021] [Indexed: 11/18/2022] Open
Abstract
Single-molecule localization microscopy provides insights into the nanometer-scale spatial organization of proteins in cells, however it does not provide information on their conformation and orientation, which are key functional signatures. Detecting single molecules' orientation in addition to their localization in cells is still a challenging task, in particular in dense cell samples. Here, we present a polarization-splitting scheme which combines Stochastic Optical Reconstruction Microscopy (STORM) with single molecule 2D orientation and wobbling measurements, without requiring a strong deformation of the imaged point spread function. This method called 4polar-STORM allows, thanks to a control of its detection numerical aperture, to determine both single molecules' localization and orientation in 2D and to infer their 3D orientation. 4polar-STORM is compatible with relatively high densities of diffraction-limited spots in an image, and is thus ideally placed for the investigation of dense protein assemblies in cells. We demonstrate the potential of this method in dense actin filament organizations driving cell adhesion and motility.
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Affiliation(s)
- Caio Vaz Rimoli
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, F-13013, Marseille, France
| | - Cesar Augusto Valades-Cruz
- Institut Curie, PSL Research University, UMR144 CNRS, Space-Time imaging of organelles and Endomembranes Dynamics Team, F-75005, Paris, France
- Inria Centre Rennes-Bretagne Atlantique, SERPICO Project Team, F-35042, Rennes, France
| | - Valentina Curcio
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, F-13013, Marseille, France
| | - Manos Mavrakis
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, F-13013, Marseille, France.
| | - Sophie Brasselet
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, F-13013, Marseille, France.
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7
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Kuzmić M, Linares GC, Fialová JL, Iv F, Salaün D, Llewellyn A, Gomes M, Belhabib M, Liu Y, Asano K, Rodrigues M, Isnardon D, Tachibana T, Koenderink GH, Badache A, Mavrakis M, Verdier-Pinard P. Septin-microtubule association via a motif unique to the isoform 1 of septin 9 tunes stress fibers. J Cell Sci 2021; 135:273936. [PMID: 34854883 DOI: 10.1242/jcs.258850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 11/19/2021] [Indexed: 10/19/2022] Open
Abstract
Septins, a family of GTP-binding proteins assembling into higher order structures, interface with the membrane, actin filaments and microtubules, which positions them as important regulators of cytoarchitecture. Septin 9 (SEPT9), which is frequently overexpressed in tumors and mutated in hereditary neuralgic amyotrophy (HNA), mediates the binding of septins to microtubules, but the molecular determinants of this interaction remained uncertain. We demonstrate that a short MAP-like motif unique to SEPT9 isoform 1 (SEPT9_i1) drives septin octamer-microtubule interaction in cells and in vitro reconstitutions. Septin-microtubule association requires polymerizable septin octamers harboring SEPT9_i1. Although outside of the MAP-like motif, HNA mutations abrogates this association, identifying a putative regulatory domain. Removal of this domain from SEPT9_i1 sequesters septins on microtubules, promotes microtubule stability and alters actomyosin fiber distribution and tension. Thus, we identify key molecular determinants and potential regulatory roles of septin-microtubule interaction, paving the way to deciphering the mechanisms underlying septin-associated pathologies.
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Affiliation(s)
- Mira Kuzmić
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, 13009 Marseille, France
| | - Gerard Castro Linares
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Jindřiška Leischner Fialová
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, 13009 Marseille, France.,Department of Pathological Physiology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - François Iv
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Danièle Salaün
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, 13009 Marseille, France
| | - Alex Llewellyn
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Maxime Gomes
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Mayssa Belhabib
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Yuxiang Liu
- Department of Bioengineering, Graduate School of Engineering, Osaka City University, Osaka, Japan
| | - Keisuke Asano
- Department of Bioengineering, Graduate School of Engineering, Osaka City University, Osaka, Japan
| | - Magda Rodrigues
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, 13009 Marseille, France
| | - Daniel Isnardon
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, 13009 Marseille, France
| | - Taro Tachibana
- Department of Bioengineering, Graduate School of Engineering, Osaka City University, Osaka, Japan.,Cell Engineering Corporation, Osaka, Japan
| | - Gijsje H Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Ali Badache
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, 13009 Marseille, France
| | - Manos Mavrakis
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Pascal Verdier-Pinard
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, 13009 Marseille, France
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8
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Iv F, Martins CS, Castro-Linares G, Taveneau C, Barbier P, Verdier-Pinard P, Camoin L, Audebert S, Tsai FC, Ramond L, Llewellyn A, Belhabib M, Nakazawa K, Di Cicco A, Vincentelli R, Wenger J, Cabantous S, Koenderink GH, Bertin A, Mavrakis M. Insights into animal septins using recombinant human septin octamers with distinct SEPT9 isoforms. J Cell Sci 2021; 134:jcs258484. [PMID: 34350965 DOI: 10.1242/jcs.258484] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 07/02/2021] [Indexed: 01/22/2023] Open
Abstract
Septin GTP-binding proteins contribute essential biological functions that range from the establishment of cell polarity to animal tissue morphogenesis. Human septins in cells form hetero-octameric septin complexes containing the ubiquitously expressed SEPT9 subunit (also known as SEPTIN9). Despite the established role of SEPT9 in mammalian development and human pathophysiology, biochemical and biophysical studies have relied on monomeric SEPT9, thus not recapitulating its native assembly into hetero-octameric complexes. We established a protocol that enabled, for the first time, the isolation of recombinant human septin octamers containing distinct SEPT9 isoforms. A combination of biochemical and biophysical assays confirmed the octameric nature of the isolated complexes in solution. Reconstitution studies showed that octamers with either a long or a short SEPT9 isoform form filament assemblies, and can directly bind and cross-link actin filaments, raising the possibility that septin-decorated actin structures in cells reflect direct actin-septin interactions. Recombinant SEPT9-containing octamers will make it possible to design cell-free assays to dissect the complex interactions of septins with cell membranes and the actin and microtubule cytoskeleton.
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Affiliation(s)
- Francois Iv
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Carla Silva Martins
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Gerard Castro-Linares
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Cyntia Taveneau
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR 168, Laboratoire Physico Chimie Curie, 75005 Paris, France
- ARC Centre of Excellence in Advanced Molecular Imaging, Monash University, Australia; Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, 3800 Clayton, Australia
| | - Pascale Barbier
- Aix-Marseille Univ, CNRS, UMR 7051, Institut de Neurophysiopathologie (INP), 13005 Marseille, France
| | - Pascal Verdier-Pinard
- Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, Institut Paoli-Calmettes, Aix Marseille Univ, CNRS, 13009 Marseille, France
| | - Luc Camoin
- Aix-Marseille Univ, INSERM, CNRS, Institut Paoli-Calmettes, CRCM, Marseille Protéomique, Marseille, France
| | - Stéphane Audebert
- Aix-Marseille Univ, INSERM, CNRS, Institut Paoli-Calmettes, CRCM, Marseille Protéomique, Marseille, France
| | - Feng-Ching Tsai
- Department of Living Matter, AMOLF, 1098 XG Amsterdam, The Netherlands
| | - Laurie Ramond
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Alex Llewellyn
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Mayssa Belhabib
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Koyomi Nakazawa
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR 168, Laboratoire Physico Chimie Curie, 75005 Paris, France
| | - Aurélie Di Cicco
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR 168, Laboratoire Physico Chimie Curie, 75005 Paris, France
| | - Renaud Vincentelli
- Architecture et Fonction des Macromolécules Biologiques (AFMB), CNRS UMR7257, Aix Marseille Univ, 13009 Marseille, France
| | - Jerome Wenger
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
| | - Stéphanie Cabantous
- Centre de Recherche en Cancérologie de Toulouse (CRCT), Inserm, Université Paul Sabatier-Toulouse III, CNRS, 31037 Toulouse, France
| | - Gijsje H Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
- Department of Living Matter, AMOLF, 1098 XG Amsterdam, The Netherlands
| | - Aurélie Bertin
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR 168, Laboratoire Physico Chimie Curie, 75005 Paris, France
| | - Manos Mavrakis
- Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
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9
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Szuba A, Bano F, Castro-Linares G, Iv F, Mavrakis M, Richter RP, Bertin A, Koenderink GH. Membrane binding controls ordered self-assembly of animal septins. eLife 2021; 10:63349. [PMID: 33847563 PMCID: PMC8099429 DOI: 10.7554/elife.63349] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 04/12/2021] [Indexed: 12/23/2022] Open
Abstract
Septins are conserved cytoskeletal proteins that regulate cell cortex mechanics. The mechanisms of their interactions with the plasma membrane remain poorly understood. Here, we show by cell-free reconstitution that binding to flat lipid membranes requires electrostatic interactions of septins with anionic lipids and promotes the ordered self-assembly of fly septins into filamentous meshworks. Transmission electron microscopy reveals that both fly and mammalian septin hexamers form arrays of single and paired filaments. Atomic force microscopy and quartz crystal microbalance demonstrate that the fly filaments form mechanically rigid, 12- to 18-nm thick, double layers of septins. By contrast, C-terminally truncated septin mutants form 4-nm thin monolayers, indicating that stacking requires the C-terminal coiled coils on DSep2 and Pnut subunits. Our work shows that membrane binding is required for fly septins to form ordered arrays of single and paired filaments and provides new insights into the mechanisms by which septins may regulate cell surface mechanics.
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Affiliation(s)
- Agata Szuba
- AMOLF, Department of Living Matter, Biological Soft Matter group, Amsterdam, Netherlands
| | - Fouzia Bano
- School of Biomedical Sciences, Faculty of Biological Sciences, Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom.,School of Physics and Astronomy, Faculty of Engineering and Physical Sciences, University of Leeds, Leeds, United Kingdom.,Bragg Centre for Materials Research, University of Leeds, Leeds, United Kingdom
| | - Gerard Castro-Linares
- AMOLF, Department of Living Matter, Biological Soft Matter group, Amsterdam, Netherlands.,Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, Netherlands
| | - Francois Iv
- Institut Fresnel, CNRS, Aix-Marseille Univ, Centrale Marseille, Marseille, France
| | - Manos Mavrakis
- Institut Fresnel, CNRS, Aix-Marseille Univ, Centrale Marseille, Marseille, France
| | - Ralf P Richter
- School of Biomedical Sciences, Faculty of Biological Sciences, Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom.,School of Physics and Astronomy, Faculty of Engineering and Physical Sciences, University of Leeds, Leeds, United Kingdom.,Bragg Centre for Materials Research, University of Leeds, Leeds, United Kingdom
| | - Aurélie Bertin
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France.,Sorbonne Université, Paris, France
| | - Gijsje H Koenderink
- AMOLF, Department of Living Matter, Biological Soft Matter group, Amsterdam, Netherlands.,Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, Netherlands
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10
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Chowdhary S, Madan S, Tomer D, Mavrakis M, Rikhy R. Mitochondrial morphology and activity regulate furrow ingression and contractile ring dynamics in Drosophila cellularization. Mol Biol Cell 2020; 31:2331-2347. [PMID: 32755438 PMCID: PMC7851960 DOI: 10.1091/mbc.e20-03-0177] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Mitochondria are maternally inherited in many organisms. Mitochondrial morphology and activity regulation is essential for cell survival, differentiation, and migration. An analysis of mitochondrial dynamics and function in morphogenetic events in early metazoan embryogenesis has not been carried out. In our study we find a crucial role of mitochondrial morphology regulation in cell formation in Drosophila embryogenesis. We find that mitochondria are small and fragmented and translocate apically on microtubules and distribute progressively along the cell length during cellularization. Embryos mutant for the mitochondrial fission protein, Drp1 (dynamin-related protein 1), die in embryogenesis and show an accumulation of clustered mitochondria on the basal side in cellularization. Additionally, Drp1 mutant embryos contain lower levels of reactive oxygen species (ROS). ROS depletion was previously shown to decrease myosin II activity. Drp1 loss also leads to myosin II depletion at the membrane furrow, thereby resulting in decreased cell height and larger contractile ring area in cellularization similar to that in myosin II mutants. The mitochondrial morphology and cellularization defects in Drp1 mutants are suppressed by reducing mitochondrial fusion and increasing cytoplasmic ROS in superoxide dismutase mutants. Our data show a key role for mitochondrial morphology and activity in supporting the morphogenetic events that drive cellularization in Drosophila embryos.
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Affiliation(s)
- Sayali Chowdhary
- Department of Biology, Indian Institute of Science Education and Research, Pashan, Pune 411008, India
| | - Somya Madan
- Department of Biology, Indian Institute of Science Education and Research, Pashan, Pune 411008, India
| | - Darshika Tomer
- Department of Biology, Indian Institute of Science Education and Research, Pashan, Pune 411008, India
| | - Manos Mavrakis
- Aix Marseille University, CNRS, Centrale Marseille, Institut Fresnel, 13013 Marseille, France
| | - Richa Rikhy
- Department of Biology, Indian Institute of Science Education and Research, Pashan, Pune 411008, India
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11
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Juanes MA, Isnardon D, Badache A, Brasselet S, Mavrakis M, Goode BL. The role of APC-mediated actin assembly in microtubule capture and focal adhesion turnover. J Cell Biol 2019; 218:3415-3435. [PMID: 31471457 PMCID: PMC6781439 DOI: 10.1083/jcb.201904165] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2019] [Revised: 07/11/2019] [Accepted: 07/26/2019] [Indexed: 12/16/2022] Open
Abstract
Actin assembly by APC maintains proper organization and dynamics of F-actin at focal adhesions. This, in turn, impacts the organization of other molecular components and the responsiveness of focal adhesions to microtubule capture and autophagosome-induced disassembly. Focal adhesion (FA) turnover depends on microtubules and actin. Microtubule ends are captured at FAs, where they induce rapid FA disassembly. However, actin’s roles are less clear. Here, we use polarization-resolved microscopy, FRAP, live cell imaging, and a mutant of Adenomatous polyposis coli (APC-m4) defective in actin nucleation to investigate the role of actin assembly in FA turnover. We show that APC-mediated actin assembly is critical for maintaining normal F-actin levels, organization, and dynamics at FAs, along with organization of FA components. In WT cells, microtubules are captured repeatedly at FAs as they mature, but once a FA reaches peak maturity, the next microtubule capture event leads to delivery of an autophagosome, triggering FA disassembly. In APC-m4 cells, microtubule capture frequency and duration are altered, and there are long delays between autophagosome delivery and FA disassembly. Thus, APC-mediated actin assembly is required for normal feedback between microtubules and FAs, and maintaining FAs in a state “primed” for microtubule-induced turnover.
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Affiliation(s)
| | - Daniel Isnardon
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Ali Badache
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Sophie Brasselet
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Centrale Marseille, Institut Fresnel, Marseille, France
| | - Manos Mavrakis
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Centrale Marseille, Institut Fresnel, Marseille, France
| | - Bruce L Goode
- Department of Biology, Brandeis University, Waltham, MA
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12
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Abstract
Functional studies in Drosophila have been key for establishing a role for the septin family of proteins in animal cell division and thus extending for the first time observations from the budding yeast to animal cells. Visualizing the distribution of specific septins in different Drosophila tissues and, in particular, in the Drosophila embryo, together with biochemical and mutant phenotype data, has contributed important advances to our understanding of animal septin biology, suggesting roles in processes other than in cytokinesis. Septin localization using immunofluorescence assays has been possible due to the generation of antibodies against different Drosophila septins. The recent availability of lines expressing fluorescent protein fusions of specific septins further promises to facilitate studies on septin dynamics. Here, we provide protocols for preparing early Drosophila embryos to visualize septins using immunofluorescence assays and live fluorescence microscopy. The genetic tractability of the Drosophila embryo together with its amenability to high-resolution fluorescence microscopy promises to provide novel insights into animal septin structure and function.
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Affiliation(s)
- M Mavrakis
- Aix Marseille Université, CNRS, Centrale Marseille, Institut Fresnel UMR 7249, Marseille, France.
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13
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Mavrakis M, Tsai FC, Koenderink G. Purification of recombinant human and Drosophila septin hexamers for TIRF assays of actin–septin filament assembly. Methods Cell Biol 2016; 136:199-220. [DOI: 10.1016/bs.mcb.2016.03.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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14
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Rikhy R, Mavrakis M, Lippincott-Schwartz J. Dynamin regulates metaphase furrow formation and plasma membrane compartmentalization in the syncytial Drosophila embryo. Biol Open 2015; 4:301-11. [PMID: 25661871 PMCID: PMC4359736 DOI: 10.1242/bio.20149936] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The successive nuclear division cycles in the syncytial Drosophila embryo are accompanied by ingression and regression of plasma membrane furrows, which surround individual nuclei at the embryo periphery, playing a central role in embryo compartmentalization prior to cellularization. Here, we demonstrate that cell cycle changes in dynamin localization and activity at the plasma membrane (PM) regulate metaphase furrow formation and PM organization in the syncytial embryo. Dynamin was localized on short PM furrows during interphase, mediating endocytosis of PM components. Dynamin redistributed off ingressed PM furrows in metaphase, correlating with stabilized PM components and the associated actin regulatory machinery on long furrows. Acute inhibition of dynamin in the temperature sensitive shibire mutant embryo resulted in morphogenetic consequences in the syncytial division cycle. These included inhibition of metaphase furrow ingression, randomization of proteins normally polarized to intercap PM and disruption of the diffusion barrier separating PM domains above nuclei. Based on these findings, we propose that cell cycle changes in dynamin orchestrate recruitment of actin regulatory machinery for PM furrow dynamics during the early mitotic cycles in the Drosophila embryo.
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Affiliation(s)
- Richa Rikhy
- Cell Biology and Metabolism Program, NICHD, NIH, Building 18T, 101, 18 Library Drive, Bethesda, MD, USA. Present address: Indian Institute of Science Education and Research, Homi Bhabha Road, Pashan, Pune, 411008, India.
| | - Manos Mavrakis
- Institut de Biologie du Développement de Marseille, CNRS UMR7288, Aix-Marseille Université, 13288 Marseille, France
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15
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Mavrakis M, Azou-Gros Y, Tsai FC, Alvarado J, Bertin A, Iv F, Kress A, Brasselet S, Koenderink GH, Lecuit T. Septins promote F-actin ring formation by crosslinking actin filaments into curved bundles. Nat Cell Biol 2014; 16:322-34. [PMID: 24633326 DOI: 10.1038/ncb2921] [Citation(s) in RCA: 157] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 01/23/2014] [Indexed: 11/09/2022]
Abstract
Animal cell cytokinesis requires a contractile ring of crosslinked actin filaments and myosin motors. How contractile rings form and are stabilized in dividing cells remains unclear. We address this problem by focusing on septins, highly conserved proteins in eukaryotes whose precise contribution to cytokinesis remains elusive. We use the cleavage of the Drosophila melanogaster embryo as a model system, where contractile actin rings drive constriction of invaginating membranes to produce an epithelium in a manner akin to cell division. In vivo functional studies show that septins are required for generating curved and tightly packed actin filament networks. In vitro reconstitution assays show that septins alone bundle actin filaments into rings, accounting for the defects in actin ring formation in septin mutants. The bundling and bending activities are conserved for human septins, and highlight unique functions of septins in the organization of contractile actomyosin rings.
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Affiliation(s)
- Manos Mavrakis
- Institut de Biologie du Développement de Marseille, CNRS UMR 7288, Aix-Marseille Université, 13288 Marseille, France
| | - Yannick Azou-Gros
- Institut de Biologie du Développement de Marseille, CNRS UMR 7288, Aix-Marseille Université, 13288 Marseille, France
| | - Feng-Ching Tsai
- 1] FOM Institute AMOLF, 1098 XG Amsterdam, The Netherlands [2]
| | - José Alvarado
- 1] FOM Institute AMOLF, 1098 XG Amsterdam, The Netherlands [2]
| | - Aurélie Bertin
- 1] Institut Curie, CNRS UMR 168, 75231 Paris, France [2]
| | - Francois Iv
- Institut de Biologie du Développement de Marseille, CNRS UMR 7288, Aix-Marseille Université, 13288 Marseille, France
| | - Alla Kress
- Institut Fresnel, CNRS UMR 7249, Aix-Marseille Université, Ecole Centrale Marseille, 13397 Marseille, France
| | - Sophie Brasselet
- Institut Fresnel, CNRS UMR 7249, Aix-Marseille Université, Ecole Centrale Marseille, 13397 Marseille, France
| | | | - Thomas Lecuit
- Institut de Biologie du Développement de Marseille, CNRS UMR 7288, Aix-Marseille Université, 13288 Marseille, France
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16
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Mavrakis M, Rikhy R, Lippincott-Schwartz J. Cells within a cell: Insights into cellular architecture and polarization from the organization of the early fly embryo. Commun Integr Biol 2013; 2:313-4. [PMID: 19721875 DOI: 10.4161/cib.2.4.8240] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Accepted: 02/19/2009] [Indexed: 11/19/2022] Open
Abstract
Drosophila embryogenesis begins with 13 rapid nuclear divisions within a common cytoplasm. These divisions produce approximately 6,000 nuclei that, during the next division cycle, become encased in plasma membrane (PM) and generate the primary embryonic epithelium in the process known as cellularization. Despite the absence of PM boundaries between syncytial nuclei, the secretory membrane system is organized in functionally compartmentalized units around individual nuclei.1 We have recently used in vivo fluorescence imaging to characterize the dynamics of proteins in the PM of the embryonic syncytium. These studies revealed that the PM is polarized already before cellularization. One PM region resides above individual nuclei and has apical-like features, while PM regions lateral to nuclei have basolateral characteristics. Optical highlighting experiments showed that membrane components do not exchange between PM regions that reside above adjacent nuclei. An intact F-actin network was shown to be important for both the PM apicobasallike polarity and the diffusion barriers within the syncytial PM. Our findings, as well as their possible implications, are further discussed in this Addendum.
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Affiliation(s)
- Manos Mavrakis
- Cell Biology and Metabolism Program; National Institute of Child Health and Human Development; National Institutes of Health; Bethesda, MD USA
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17
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Abstract
Embryology and genetics have given rise to a mechanistic framework that explains the architecture of a developing organism. Until recently, however, such studies suffered from a lack of quantification and real-time visualization at the subcellular level, limiting their ability to monitor the dynamics of developmental processes. Live imaging using fluorescent proteins has overcome these limitations, uncovering unprecedented insights that call many established models into question. We review how the study of patterning, cell polarization and morphogenesis has benefited from this technology and discuss the possibilities offered by fluorescence imaging and by the contributions of quantitative disciplines.
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Affiliation(s)
- Manos Mavrakis
- IBDML (Institut de Biologie du Développement de Marseille Luminy), UMR6216 CNRS—Université de la Méditerranée, Parc Scientifique de Luminy BP 907, 13009 Marseille, France
| | - Olivier Pourquié
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire) / Inserm U964 / CNRS UMR7104, 67400 Illkirch, France; and Université de Strasbourg, 67000 Strasbourg, France
| | - Thomas Lecuit
- IBDML (Institut de Biologie du Développement de Marseille Luminy), UMR6216 CNRS—Université de la Méditerranée, Parc Scientifique de Luminy BP 907, 13009 Marseille, France
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18
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Mavrakis M, Rikhy R, Lippincott-Schwartz J. Plasma membrane polarity and compartmentalization are established before cellularization in the fly embryo. Dev Cell 2009; 16:93-104. [PMID: 19154721 PMCID: PMC2684963 DOI: 10.1016/j.devcel.2008.11.003] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Revised: 08/27/2008] [Accepted: 11/06/2008] [Indexed: 10/21/2022]
Abstract
Patterning in the Drosophila embryo requires local activation and dynamics of proteins in the plasma membrane (PM). We used in vivo fluorescence imaging to characterize the organization and diffusional properties of the PM in the early embryonic syncytium. Before cellularization, the PM is polarized into discrete domains having epithelial-like characteristics. One domain resides above individual nuclei and has apical-like characteristics, while the other domain is lateral to nuclei and contains markers associated with basolateral membranes and junctions. Pulse-chase photoconversion experiments show that molecules can diffuse within each domain but do not exchange between PM regions above adjacent nuclei. Drug-induced F-actin depolymerization disrupted both the apicobasal-like polarity and the diffusion barriers within the syncytial PM. These events correlated with perturbations in the spatial pattern of dorsoventral Toll signaling. We propose that epithelial-like properties and an intact F-actin network compartmentalize the PM and shape morphogen gradients in the syncytial embryo.
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Affiliation(s)
- Manos Mavrakis
- Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, Bldg. 18T, 18 Library Drive, Bethesda, MD 20892, USA
| | - Richa Rikhy
- Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, Bldg. 18T, 18 Library Drive, Bethesda, MD 20892, USA
| | - Jennifer Lippincott-Schwartz
- Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, Bldg. 18T, 18 Library Drive, Bethesda, MD 20892, USA
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19
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Meoli E, Bossis I, Cazabat L, Mavrakis M, Horvath A, Stergiopoulos S, Shiferaw ML, Fumey G, Perlemoine K, Muchow M, Robinson-White A, Weinberg F, Nesterova M, Patronas Y, Groussin L, Bertherat J, Stratakis CA. Protein kinase A effects of an expressed PRKAR1A mutation associated with aggressive tumors. Cancer Res 2008; 68:3133-41. [PMID: 18451138 DOI: 10.1158/0008-5472.can-08-0064] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Most PRKAR1A tumorigenic mutations lead to nonsense mRNA that is decayed; tumor formation has been associated with an increase in type II protein kinase A (PKA) subunits. The IVS6+1G>T PRKAR1A mutation leads to a protein lacking exon 6 sequences [R1 alpha Delta 184-236 (R1 alpha Delta 6)]. We compared in vitro R1 alpha Delta 6 with wild-type (wt) R1 alpha. We assessed PKA activity and subunit expression, phosphorylation of target molecules, and properties of wt-R1 alpha and mutant (mt) R1 alpha; we observed by confocal microscopy R1 alpha tagged with green fluorescent protein and its interactions with Cerulean-tagged catalytic subunit (C alpha). Introduction of the R1 alpha Delta 6 led to aberrant cellular morphology and higher PKA activity but no increase in type II PKA subunits. There was diffuse, cytoplasmic localization of R1 alpha protein in wt-R1 alpha- and R1 alpha Delta 6-transfected cells but the former also exhibited discrete aggregates of R1 alpha that bound C alpha; these were absent in R1 alpha Delta 6-transfected cells and did not bind C alpha at baseline or in response to cyclic AMP. Other changes induced by R1 alpha Delta 6 included decreased nuclear C alpha. We conclude that R1 alpha Delta 6 leads to increased PKA activity through the mt-R1 alpha decreased binding to C alpha and does not involve changes in other PKA subunits, suggesting that a switch to type II PKA activity is not necessary for increased kinase activity or tumorigenesis.
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Affiliation(s)
- Elise Meoli
- Section on Endocrinology and Genetics, Program in Developmental Endocrinology and Genetics, National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892, USA
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20
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Mavrakis M, Rikhy R, Lilly M, Lippincott‐Schwartz J. Fluorescence Imaging Techniques for StudyingDrosophilaEmbryo Development. ACTA ACUST UNITED AC 2008; Chapter 4:Unit 4.18. [DOI: 10.1002/0471143030.cb0418s39] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Manos Mavrakis
- Institute of Developmental Biology of Marseille‐Luminy, UMR6216 CNRS‐Université de la Méditerranée Marseille France
| | - Richa Rikhy
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health Bethesda Maryland
| | - Mary Lilly
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health Bethesda Maryland
| | - Jennifer Lippincott‐Schwartz
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health Bethesda Maryland
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21
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Missirlis F, Kosmidis S, Brody T, Mavrakis M, Holmberg S, Odenwald WF, Skoulakis EMC, Rouault TA. Homeostatic mechanisms for iron storage revealed by genetic manipulations and live imaging of Drosophila ferritin. Genetics 2007; 177:89-100. [PMID: 17603097 PMCID: PMC2013694 DOI: 10.1534/genetics.107.075150] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ferritin is a symmetric, 24-subunit iron-storage complex assembled of H and L chains. It is found in bacteria, plants, and animals and in two classes of mutations in the human L-chain gene, resulting in hereditary hyperferritinemia cataract syndrome or in neuroferritinopathy. Here, we examined systemic and cellular ferritin regulation and trafficking in the model organism Drosophila melanogaster. We showed that ferritin H and L transcripts are coexpressed during embryogenesis and that both subunits are essential for embryonic development. Ferritin overexpression impaired the survival of iron-deprived flies. In vivo expression of GFP-tagged holoferritin confirmed that iron-loaded ferritin molecules traffic through the Golgi organelle and are secreted into hemolymph. A constant ratio of ferritin H and L subunits, secured via tight post-transcriptional regulation, is characteristic of the secreted ferritin in flies. Differential cellular expression, conserved post-transcriptional regulation via the iron regulatory element, and distinct subcellular localization of the ferritin subunits prior to the assembly of holoferritin are all important steps mediating iron homeostasis. Our study revealed both conserved features and insect-specific adaptations of ferritin nanocages and provides novel imaging possibilities for their in vivo characterization.
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Affiliation(s)
- Fanis Missirlis
- Neural Cell-Fate Determinants Section, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland 20892, USA.
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22
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Mavrakis M, Lippincott-Schwartz J, Stratakis CA, Bossis I. mTOR kinase and the regulatory subunit of protein kinase A (PRKAR1A) spatially and functionally interact during autophagosome maturation. Autophagy 2007; 3:151-3. [PMID: 17204847 DOI: 10.4161/auto.3632] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The regulatory subunit 1-alpha (RIalpha) of protein kinase A (PKA) and the mTOR kinase are involved in a common pathway regulating mammalian autophagy. RIalpha was found to localize on Rab7-positive late endosomes and on LC3-positive autophagosomal membranes in cultured cells. RIalpha was also shown to physically interact with mTOR kinase and affect its phosphorylation and activity. In this addendum, we further explore the subcellular distribution of mTOR related to RIalpha and LC3. We present experiments showing that mTOR colocalizes with RIalpha-, Rab7- and LC3-positive membranes in cultured cells. Because RIalpha regulates the phosphorylation and activity of mTOR kinase, which we now show localizes on autophagosomal membranes, the possibility emerges that the RIalpha-mTOR complex acts at the level of autophagosome maturation.
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Affiliation(s)
- Manos Mavrakis
- Cell Biology and Metabolism Branch, Section on Endocrinology and Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-5430, USA
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23
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Mavrakis M, Lippincott-Schwartz J, Stratakis CA, Bossis I. Depletion of type IA regulatory subunit (RIalpha) of protein kinase A (PKA) in mammalian cells and tissues activates mTOR and causes autophagic deficiency. Hum Mol Genet 2006; 15:2962-71. [PMID: 16963469 DOI: 10.1093/hmg/ddl239] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The human PRKAR1A gene encodes the regulatory subunit 1-alpha (RIalpha) of the cAMP-dependent protein kinase A (PKA) holoenzyme. Regulation of the catalytic activity of PKA is the only well-studied function of RIalpha. Inactivating PRKAR1A mutations cause primary pigmented nodular adrenocortical disease (PPNAD) or Carney complex (CNC), an inherited syndrome associated with abnormal skin pigmentation and multiple neoplasias, including PPNAD. Histochemistry of tissues from CNC patients is indicative of autophagic deficiency and this led us to investigate the relationship between RIalpha and mammalian autophagy. We found that fluorescently tagged RIalpha associates with late endosomes and autophagosomes in cultured cells. The number of autophagosomes in prkar1a-/- mouse embryonic fibroblasts (MEFs) was reduced compared with wild-type MEFs. RIalpha co-immunoprecipitated with mTOR kinase, a major regulator of autophagy. Phosphorylated-mTOR levels and mTOR activity were dramatically increased in prkar1a-/- mouse cells, and in HEK 293 cells with RIalpha levels reduced by siRNA. Finally, phosphorylated-mTOR levels and mTOR activity were increased in CNC cells and in PPNAD tissues. These data suggest that RIalpha deficiency decreases autophagy by the activation of mTOR, providing a molecular basis to autophagic deficiency in PPNAD.
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Affiliation(s)
- Manos Mavrakis
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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Frescas D, Mavrakis M, Lorenz H, Delotto R, Lippincott-Schwartz J. The secretory membrane system in the Drosophila syncytial blastoderm embryo exists as functionally compartmentalized units around individual nuclei. J Cell Biol 2006; 173:219-30. [PMID: 16636144 PMCID: PMC2063813 DOI: 10.1083/jcb.200601156] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Accepted: 03/20/2006] [Indexed: 01/08/2023] Open
Abstract
Drosophila melanogaster embryogenesis begins with 13 nuclear division cycles within a syncytium. This produces >6,000 nuclei that, during the next division cycle, become encased in plasma membrane in the process known as cellularization. In this study, we investigate how the secretory membrane system becomes equally apportioned among the thousands of syncytial nuclei in preparation for cellularization. Upon nuclear arrival at the cortex, the endoplasmic reticulum (ER) and Golgi were found to segregate among nuclei, with each nucleus becoming surrounded by a single ER/Golgi membrane system separate from adjacent ones. The nuclear-associated units of ER and Golgi across the syncytial blastoderm produced secretory products that were delivered to the plasma membrane in a spatially restricted fashion across the embryo. This occurred in the absence of plasma membrane boundaries between nuclei and was dependent on centrosome-derived microtubules. The emergence of secretory membranes that compartmentalized around individual nuclei in the syncytial blastoderm is likely to ensure that secretory organelles are equivalently partitioned among nuclei at cellularization and could play an important role in the establishment of localized gene and protein expression patterns within the early embryo.
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Affiliation(s)
- David Frescas
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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25
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Mavrakis M, Méhouas S, Réal E, Iseni F, Blondel D, Tordo N, Ruigrok RWH. Rabies virus chaperone: identification of the phosphoprotein peptide that keeps nucleoprotein soluble and free from non-specific RNA. Virology 2006; 349:422-9. [PMID: 16494915 DOI: 10.1016/j.virol.2006.01.030] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Revised: 01/12/2006] [Accepted: 01/24/2006] [Indexed: 11/25/2022]
Abstract
The genomic RNA of rabies virus is always complexed with the viral nucleoprotein (N). This N-RNA complex is the template for viral transcription and replication. The viral phosphoprotein (P) has two functions during the infection process: it binds through its carboxy-terminus to N in the N-RNA complex and at the same time with an amino-terminal domain to the polymerase and in this way fixes the polymerase to its template. The second function of P is to bind to newly produced N in the infected cell in order to prevent that N binds non-specifically and irreversibly to cellular RNA. In order to identify the part of the phosphoprotein that binds to N and keeps the latter soluble, we isolated the N-P complex, performed sequential protease digestions, and determined the identity of the remaining N and P peptides in the purified digested complex. Although the digestion steps removed short sequences of N, most of N remained intact and soluble, indicating that the overall structure was not affected. Most of P, including the carboxy-terminal N-RNA-binding domain, was removed during the first digestion step. N-terminal sequencing and mass spectrometry analysis identified a P peptide containing residues 4-40 that remained associated with N. Coexpression and coimmunoprecipitation experiments and yeast two-hybrid experiments showed that this peptide alone could bind to N in vivo.
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Affiliation(s)
- Manos Mavrakis
- EMBL Grenoble Outstation, B.P. 181, 38042 Grenoble cedex 9, France
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Murray JL, Mavrakis M, McDonald NJ, Yilla M, Sheng J, Bellini WJ, Zhao L, Le Doux JM, Shaw MW, Luo CC, Lippincott-Schwartz J, Sanchez A, Rubin DH, Hodge TW. Rab9 GTPase is required for replication of human immunodeficiency virus type 1, filoviruses, and measles virus. J Virol 2005; 79:11742-51. [PMID: 16140752 PMCID: PMC1212642 DOI: 10.1128/jvi.79.18.11742-11751.2005] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Rab proteins and their effectors facilitate vesicular transport by tethering donor vesicles to their respective target membranes. By using gene trap insertional mutagenesis, we identified Rab9, which mediates late-endosome-to-trans-Golgi-network trafficking, among several candidate host genes whose disruption allowed the survival of Marburg virus-infected cells, suggesting that Rab9 is utilized in Marburg replication. Although Rab9 has not been implicated in human immunodeficiency virus (HIV) replication, previous reports suggested that the late endosome is an initiation site for HIV assembly and that TIP47-dependent trafficking out of the late endosome to the trans-Golgi network facilitates the sorting of HIV Env into virions budding at the plasma membrane. We examined the role of Rab9 in the life cycles of HIV and several unrelated viruses, using small interfering RNA (siRNA) to silence Rab9 expression before viral infection. Silencing Rab9 expression dramatically inhibited HIV replication, as did silencing the host genes encoding TIP47, p40, and PIKfyve, which also facilitate late-endosome-to-trans-Golgi vesicular transport. In addition, silencing studies revealed that HIV replication was dependent on the expression of Rab11A, which mediates trans-Golgi-to-plasma-membrane transport, and that increased HIV Gag was sequestered in a CD63+ endocytic compartment in a cell line stably expressing Rab9 siRNA. Replication of the enveloped Ebola, Marburg, and measles viruses was inhibited with Rab9 siRNA, although the non-enveloped reovirus was insensitive to Rab9 silencing. These results suggest that Rab9 is an important cellular target for inhibiting diverse viruses and help to define a late-endosome-to-plasma-membrane vesicular transport pathway important in viral assembly.
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Affiliation(s)
- James L Murray
- National Center for HIV, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA
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Mavrakis M, McCarthy AA, Roche S, Blondel D, Ruigrok RWH. Structure and function of the C-terminal domain of the polymerase cofactor of rabies virus. J Mol Biol 2004; 343:819-31. [PMID: 15476803 PMCID: PMC7173060 DOI: 10.1016/j.jmb.2004.08.071] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2004] [Revised: 08/23/2004] [Accepted: 08/24/2004] [Indexed: 11/17/2022]
Abstract
The phosphoprotein (P) of rabies virus binds the viral polymerase to the nucleoprotein (N)-RNA template for transcription and replication. By limited protease digestion we defined a monomeric C-terminal domain of P that can bind to N-RNA. The atomic structure of this domain was determined and previously described mutations that interfere with binding of P to N-RNA could now be interpreted. There appears to be two features involved in this activity situated at opposite surfaces of the molecule: a positively charged patch and a hydrophobic pocket with an exposed tryptophan side-chain. Other previously published work suggests a conformational change in P when it binds to N-RNA, which may imply the repositioning of two helices that would expose a hydrophobic groove for interaction with N. This domain of rabies virus P is structurally unrelated to the N-RNA binding domains of the phosphoproteins of Sendai and measles virus that are members of the same order of viruses, the non-segmented negative strand RNA viruses. The implications of this finding for the evolution of this virus group are discussed.
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Affiliation(s)
- Manos Mavrakis
- EMBL Grenoble Outstation, BP181, 38042 Grenoble Cedex 9, France
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Schoehn G, Mavrakis M, Albertini A, Wade R, Hoenger A, Ruigrok RWH. The 12 A structure of trypsin-treated measles virus N-RNA. J Mol Biol 2004; 339:301-12. [PMID: 15136034 DOI: 10.1016/j.jmb.2004.03.073] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2004] [Revised: 03/24/2004] [Accepted: 03/26/2004] [Indexed: 10/26/2022]
Abstract
Recombinant measles virus nucleoprotein (N) was produced in insect cells where it bound to cellular RNA to form helical N-RNA structures. These structures were observed by electron microscopy but were too flexible for high-resolution image analysis. Removal of the C-terminal tail of N by trypsin treatment resulted in structures that were much more rigid and seemed more regular. Several methods of image analysis were employed in order to make a helical reconstruction of the digested N-RNA. During this analysis, it became clear that the apparently regular coils of digested N-RNA consisted of a series of closely related helical states. The iterative helical real space reconstruction method allowed the identification of two helical states for which a reconstruction could be calculated. The model with the highest resolution shows N monomers that consist of three domains and that are connected to their neighbours by two narrow connections, one close to the helical axis and another toward the middle of the monomers. There are no connections between N molecules in subsequent helical turns. After labelling the RNA in the structure with cis-platinum, the connection closest to the helical axis increased in density, suggesting the position of the RNA. The shapes of the monomers of the nucleoproteins of influenza virus, rabies virus (both determined before) and that of measles virus (determined here) are all similar, whereas the overall shapes of their respective N-RNAs (nucleocapsids) is very different. This is probably due to the position and number of the connections between the N subunits in the N-RNA, one for influenza virus allowing much flexibility, two for rabies virus at either end of the N molecules leading to ribbons and two for measles virus leading to the typical paramyxovirus helical nucleocapsid.
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Affiliation(s)
- Guy Schoehn
- EMBL Grenoble Outstation, 6 rue Jules Horowitz, B.P. 181, 38042 Grenoble 9, France.
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Mavrakis M, Iseni F, Mazza C, Schoehn G, Ebel C, Gentzel M, Franz T, Ruigrok RWH. Isolation and characterisation of the rabies virus N degrees-P complex produced in insect cells. Virology 2003; 305:406-14. [PMID: 12573586 DOI: 10.1006/viro.2002.1748] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
When the nucleoprotein (N) of nonsegmented negative-strand RNA viruses is expressed in insect cells, it binds to cellular RNA and forms N-RNA complexes just like viral nucleocapsids. However, in virus-infected cells, N is prevented from binding to cellular RNA because a soluble complex is formed between N and the viral phosphoprotein (P), the N degrees -P complex. N is only released from this complex for binding to newly made viral or complementary RNA. We coexpressed rabies virus N and P proteins in insect cells and purified the N degrees -P complex. Characterisation by gel filtration, polyacrylamide gel electrophoresis, analytical ultracentrifugation, native mass spectroscopy, and electron microscopy showed that the complex consists of one N protein plus two P proteins, i.e., an N degrees -P(2) complex.
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Affiliation(s)
- Manos Mavrakis
- EMBL Grenoble Outstation, B.P. 181, 38042 Grenoble Cedex 9, France
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Abstract
When Marburg virus (MBGV) nucleoprotein (NP) is expressed in insect cells, it binds to cellular RNA and forms NP-RNA complexes such as insect cell-expressed nucleoproteins from other nonsegmented negative-strand RNA viruses. Recombinant MBGV NP-RNA forms loose coils that resemble rabies virus N-RNA. MBGV NP monomers are rods that are spaced along the coil similar to the nucleoprotein monomers of the rabies virus N-RNA. High salt treatment induces tight coiling of the MBGV NP-RNA, again a characteristic observed for other nonsegmented negative-strand virus N-RNAs. Electron microscopy of fixed Marburg virus particles shows that the viral nucleocapsid has a smaller diameter than the free, recombinant NP-RNA. This difference in helical parameters could be caused by the interaction of other viral proteins with the NP-RNA. A similar but opposite phenomenon is observed for rhabdovirus nucleocapsids that are condensed by the viral matrix protein upon which they acquire a larger diameter. Finally, there appears to be an extensive and regular protein scaffold between the viral nucleocapsid and the membrane that seems not to exist in the other negative-strand RNA viruses.
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Schoehn G, Iseni F, Mavrakis M, Blondel D, Ruigrok RW. Structure of recombinant rabies virus nucleoprotein-RNA complex and identification of the phosphoprotein binding site. J Virol 2001; 75:490-8. [PMID: 11119617 PMCID: PMC113941 DOI: 10.1128/jvi.75.1.490-498.2001] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rabies virus nucleoprotein (N) was produced in insect cells, in which it forms nucleoprotein-RNA (N-RNA) complexes that are biochemically and biophysically indistinguishable from rabies virus N-RNA. We selected recombinant N-RNA complexes that were bound to short insect cellular RNAs which formed small rings containing 9 to 11 N monomers. We also produced recombinant N-RNA rings and viral N-RNA that were treated with trypsin and that had lost the C-terminal quarter of the nucleoprotein. Trypsin-treated N-RNA no longer bound to recombinant rabies virus phosphoprotein (the viral polymerase cofactor), so the presence of the C-terminal part of N is needed for binding of the phosphoprotein. Both intact and trypsin-treated recombinant N-RNA rings were analyzed with cryoelectron microscopy, and three-dimensional models were calculated from single-particle image analysis combined with back projection. Nucleoprotein has a bilobed shape, and each monomer has two sites of interaction with each neighbor. Trypsin treatment cuts off part of one of the lobes without shortening the protein or changing other structural parameters. Using negative-stain electron microscopy, we visualized phosphoprotein bound to the tips of the N-RNA rings, most likely at the site that can be removed by trypsin. Based on the shape of N determined here and on structural parameters derived from electron microscopy on free rabies virus N-RNA and from nucleocapsid in virus, we propose a low-resolution model for rabies virus N-RNA in the virus.
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Affiliation(s)
- G Schoehn
- European Molecular Biology Laboratory Grenoble Outstation, 38042 Grenoble cedex 9, France
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