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Mendonça DC, Morais STB, Ciol H, Pinto APA, Leonardo DA, Pereira HD, Valadares NF, Portugal RV, Klaholz BP, Garratt RC, Araujo APU. Structural Insights into Ciona intestinalis Septins: Complexes Suggest a Mechanism for Nucleotide-dependent Interfacial Cross-talk. J Mol Biol 2024; 436:168693. [PMID: 38960133 DOI: 10.1016/j.jmb.2024.168693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2024] [Revised: 06/19/2024] [Accepted: 06/27/2024] [Indexed: 07/05/2024]
Abstract
Septins are filamentous nucleotide-binding proteins which can associate with membranes in a curvature-dependent manner leading to structural remodelling and barrier formation. Ciona intestinalis, a model for exploring the development and evolution of the chordate lineage, has only four septin-coding genes within its genome. These represent orthologues of the four classical mammalian subgroups, making it a minimalist non-redundant model for studying the modular assembly of septins into linear oligomers and thereby filamentous polymers. Here, we show that C. intestinalis septins present a similar biochemistry to their human orthologues and also provide the cryo-EM structures of an octamer, a hexamer and a tetrameric sub-complex. The octamer, which has the canonical arrangement (2-6-7-9-9-7-6-2) clearly shows an exposed NC-interface at its termini enabling copolymerization with hexamers into mixed filaments. Indeed, only combinations of septins which had CiSEPT2 occupying the terminal position were able to assemble into filaments via NC-interface association. The CiSEPT7-CiSEPT9 tetramer is the smallest septin particle to be solved by Cryo-EM to date and its good resolution (2.7 Å) provides a well-defined view of the central NC-interface. On the other hand, the CiSEPT7-CiSEPT9 G-interface shows signs of fragility permitting toggling between hexamers and octamers, similar to that seen in human septins but not in yeast. The new structures provide insights concerning the molecular mechanism for cross-talk between adjacent interfaces. This indicates that C. intestinalis may represent a valuable tool for future studies, fulfilling the requirements of a complete but simpler system to understand the mechanisms behind the assembly and dynamics of septin filaments.
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Affiliation(s)
| | | | - Heloísa Ciol
- São Carlos Institute of Physics, USP, São Carlos, SP, Brazil
| | | | | | | | | | - Rodrigo V Portugal
- Brazilian Nanotechnology National Laboratory, CNPEM, Campinas, SP, Brazil; Biotechnosciency Program, Federal University of ABC, Santo André, SP, Brazil
| | - Bruno P Klaholz
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), 67404 Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, 67404 Illkirch, France; Institut National de la Santé et de la Recherche Médicale (INSERM) U964, 67404 Illkirch, France; Université de Strasbourg, 67081 Strasbourg, France
| | | | - Ana P U Araujo
- São Carlos Institute of Physics, USP, São Carlos, SP, Brazil.
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2
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Dean WF, Nawara TJ, Albert RM, Mattheyses AL. OOPS: Object-Oriented Polarization Software for analysis of fluorescence polarization microscopy images. PLoS Comput Biol 2024; 20:e1011723. [PMID: 39133751 PMCID: PMC11341096 DOI: 10.1371/journal.pcbi.1011723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 08/22/2024] [Accepted: 08/02/2024] [Indexed: 08/24/2024] Open
Abstract
Most essential cellular functions are performed by proteins assembled into larger complexes. Fluorescence Polarization Microscopy (FPM) is a powerful technique that goes beyond traditional imaging methods by allowing researchers to measure not only the localization of proteins within cells, but also their orientation or alignment within complexes or cellular structures. FPM can be easily integrated into standard widefield microscopes with the addition of a polarization modulator. However, the extensive image processing and analysis required to interpret the data have limited its widespread adoption. To overcome these challenges and enhance accessibility, we introduce OOPS (Object-Oriented Polarization Software), a MATLAB package for object-based analysis of FPM data. By combining flexible image segmentation and novel object-based analyses with a high-throughput FPM processing pipeline, OOPS empowers researchers to simultaneously study molecular order and orientation in individual biological structures; conduct population assessments based on morphological features, intensity statistics, and FPM measurements; and create publication-quality visualizations, all within a user-friendly graphical interface. Here, we demonstrate the power and versatility of our approach by applying OOPS to punctate and filamentous structures.
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Affiliation(s)
- William F. Dean
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Tomasz J. Nawara
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Rose M. Albert
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Alexa L. Mattheyses
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
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3
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Varela Salgado M, Adriaans IE, Touati SA, Ibanes S, Lai-Kee-Him J, Ancelin A, Cipelletti L, Picas L, Piatti S. Phosphorylation of the F-BAR protein Hof1 drives septin ring splitting in budding yeast. Nat Commun 2024; 15:3383. [PMID: 38649354 PMCID: PMC11035697 DOI: 10.1038/s41467-024-47709-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 04/09/2024] [Indexed: 04/25/2024] Open
Abstract
A double septin ring accompanies cytokinesis in yeasts and mammalian cells. In budding yeast, reorganisation of the septin collar at the bud neck into a dynamic double ring is essential for actomyosin ring constriction and cytokinesis. Septin reorganisation requires the Mitotic Exit Network (MEN), a kinase cascade essential for cytokinesis. However, the effectors of MEN in this process are unknown. Here we identify the F-BAR protein Hof1 as a critical target of MEN in septin remodelling. Phospho-mimicking HOF1 mutant alleles overcome the inability of MEN mutants to undergo septin reorganisation by decreasing Hof1 binding to septins and facilitating its translocation to the actomyosin ring. Hof1-mediated septin rearrangement requires its F-BAR domain, suggesting that it may involve a local membrane remodelling that leads to septin reorganisation. In vitro Hof1 can induce the formation of intertwined septin bundles, while a phosphomimetic Hof1 protein has impaired septin-bundling activity. Altogether, our data indicate that Hof1 modulates septin architecture in distinct ways depending on its phosphorylation status.
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Affiliation(s)
- Maritzaida Varela Salgado
- CRBM (Centre de Recherche en Biologie cellulaire de Montpellier), University of Montpellier, CNRS UMR 5237, 34293, Montpellier, France
| | - Ingrid E Adriaans
- CRBM (Centre de Recherche en Biologie cellulaire de Montpellier), University of Montpellier, CNRS UMR 5237, 34293, Montpellier, France
| | - Sandra A Touati
- Université Paris Cité, CNRS, Institut Jacques Monod, 75013, Paris, France
| | - Sandy Ibanes
- CRBM (Centre de Recherche en Biologie cellulaire de Montpellier), University of Montpellier, CNRS UMR 5237, 34293, Montpellier, France
| | - Joséphine Lai-Kee-Him
- CBS (Centre de Biologie Structurale), University of Montpellier, CNRS UMR 5048, INSERM U 1054, 34090, Montpellier, France
| | - Aurélie Ancelin
- CBS (Centre de Biologie Structurale), University of Montpellier, CNRS UMR 5048, INSERM U 1054, 34090, Montpellier, France
| | - Luca Cipelletti
- L2C (Laboratoire Charles Coulomb), University of Montpellier, CNRS 34095, Montpellier, France
- IUF (Institut Universitaire de France, 75231, Paris, France
| | - Laura Picas
- IRIM (Institut de Recherche en Infectiologie de Montpellier), University of Montpellier, CNRS UMR 9004, 34293, Montpellier, France
| | - Simonetta Piatti
- CRBM (Centre de Recherche en Biologie cellulaire de Montpellier), University of Montpellier, CNRS UMR 5237, 34293, Montpellier, France.
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4
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Müller J, Furlan M, Settele D, Grupp B, Johnsson N. Transient septin sumoylation steers a Fir1-Skt5 protein complex between the split septin ring. J Cell Biol 2024; 223:e202301027. [PMID: 37938157 PMCID: PMC10631487 DOI: 10.1083/jcb.202301027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 10/05/2023] [Accepted: 10/17/2023] [Indexed: 11/09/2023] Open
Abstract
Ubiquitylation and phosphorylation control composition and architecture of the cell separation machinery in yeast and other eukaryotes. The significance of septin sumoylation on cell separation remained an enigma. Septins form an hourglass structure at the bud neck of yeast cells that transforms into a split septin double ring during mitosis. We discovered that sumoylated septins recruit the cytokinesis checkpoint protein Fir1 to the peripheral side of the septin hourglass just before its transformation into the double-ring configuration. As this transition occurs, Fir1 is released from the septins and seamlessly relocates between the split septin rings through synchronized binding to the scaffold Spa2. Fir1 binds and carries the membrane-bound Skt5 on its route to the division plane where the Fir1-Skt5 complex serves as receptor for chitin synthase III.
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Affiliation(s)
- Judith Müller
- Department of Biology, Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Monique Furlan
- Department of Biology, Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - David Settele
- Department of Biology, Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Benjamin Grupp
- Department of Biology, Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
| | - Nils Johnsson
- Department of Biology, Institute of Molecular Genetics and Cell Biology, Ulm University, Ulm, Germany
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5
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Nakazawa K, Chauvin B, Mangenot S, Bertin A. Reconstituted in vitro systems to reveal the roles and functions of septins. J Cell Sci 2023; 136:jcs259448. [PMID: 37815088 DOI: 10.1242/jcs.259448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/11/2023] Open
Abstract
Septins are essential cytoskeletal proteins involved in key cellular processes and have also been implicated in diseases from cancers to neurodegenerative pathologies. However, they have not been as thoroughly studied as other cytoskeletal proteins. In vivo, septins interact with other cytoskeletal proteins and with the inner plasma membrane. Hence, bottom-up in vitro cell-free assays are well suited to dissect the roles and behavior of septins in a controlled environment. Specifically, in vitro studies have been invaluable in describing the self-assembly of septins into a large diversity of ultrastructures. Given that septins interact specifically with membrane, the details of these septin-membrane interactions have been analyzed using reconstituted lipid systems. In particular, at a membrane, septins are often localized at curvatures of micrometer scale. In that context, in vitro assays have been performed with substrates of varying curvatures (spheres, cylinders or undulated substrates) to probe the sensitivity of septins to membrane curvature. This Review will first present the structural properties of septins in solution and describe the interplay of septins with cytoskeletal partners. We will then discuss how septins interact with biomimetic membranes and induce their reshaping. Finally, we will highlight the curvature sensitivity of septins and how they alter the mechanical properties of membranes.
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Affiliation(s)
- Koyomi Nakazawa
- Physico Chimie Curie , Institut Curie, CNRS UMR 168, Sorbonne Université, 11 Rue Pierre et Paris Curie, 75005 Paris, France
| | - Brieuc Chauvin
- Physico Chimie Curie , Institut Curie, CNRS UMR 168, Sorbonne Université, 11 Rue Pierre et Paris Curie, 75005 Paris, France
| | - Stéphanie Mangenot
- Laboratoire Matière et Systèmes Complexes , Université de Paris Cité, CNRS UMR 7057, 45 Rue des Saint Pères, 75006 Paris, France
| | - Aurélie Bertin
- Physico Chimie Curie , Institut Curie, CNRS UMR 168, Sorbonne Université, 11 Rue Pierre et Paris Curie, 75005 Paris, France
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Werner B, Yadav S. Phosphoregulation of the septin cytoskeleton in neuronal development and disease. Cytoskeleton (Hoboken) 2023; 80:275-289. [PMID: 36127729 PMCID: PMC10025170 DOI: 10.1002/cm.21728] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 08/13/2022] [Accepted: 09/12/2022] [Indexed: 11/06/2022]
Abstract
Septins are highly conserved GTP-binding proteins that oligomerize and form higher order structures. The septin cytoskeleton plays an important role in cellular organization, intracellular transport, and cytokinesis. Kinase-mediated phosphorylation of septins regulates various aspects of their function, localization, and dynamics. Septins are enriched in the mammalian nervous system where they contribute to neurodevelopment and neuronal function. Emerging research has implicated aberrant changes in septin cytoskeleton in several human diseases. The mechanisms through which aberrant phosphorylation by kinases contributes to septin dysfunction in neurological disorders are poorly understood and represent an important question for future research with therapeutic implications. This review summarizes the current state of knowledge of the diversity of kinases that interact with and phosphorylate mammalian septins, delineates how phosphoregulation impacts septin dynamics, and describes how aberrant septin phosphorylation contributes to neurological disorders.
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Affiliation(s)
- Bailey Werner
- Department of Pharmacology, University of Washington, Seattle, WA, United States
| | - Smita Yadav
- Department of Pharmacology, University of Washington, Seattle, WA, United States
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Benson A, McMurray M. Simultaneous co-overexpression of Saccharomyces cerevisiae septins Cdc3 and Cdc10 drives pervasive, phospholipid-, and tag-dependent plasma membrane localization. Cytoskeleton (Hoboken) 2023; 80:199-214. [PMID: 37098755 PMCID: PMC10524705 DOI: 10.1002/cm.21762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 03/29/2023] [Accepted: 04/17/2023] [Indexed: 04/27/2023]
Abstract
Septin proteins contribute to many eukaryotic processes involving cellular membranes. In the budding yeast Saccharomyces cerevisiae, septin hetero-oligomers interact with the plasma membrane (PM) almost exclusively at the future site of cytokinesis. While multiple mechanisms of membrane recruitment have been identified, including direct interactions with specific phospholipids and curvature-sensitive interactions via amphipathic helices, these do not fully explain why yeast septins do not localize all over the inner leaflet of the PM. While engineering an inducible split-yellow fluorescent protein (YFP) system to measure the kinetics of yeast septin complex assembly, we found that ectopic co-overexpression of two tagged septins, Cdc3 and Cdc10, resulted in nearly uniform PM localization, as well as perturbation of endogenous septin function. Septin localization and function in gametogenesis were also perturbed. PM localization required the C-terminal YFP fragment fused to the C terminus of Cdc3, the septin-associated kinases Cla4 and Gin4, and phosphotidylinositol-4,5-bis-phosphate (PI[4,5]P2 ), but not the putative PI(4,5)P2 -binding residues in Cdc3. Endogenous Cdc10 was recruited to the PM, likely contributing to the functional interference. PM-localized septins did not exchange with the cytosolic pool, indicative of stable polymers. These findings provide new clues as to what normally restricts septin localization to specific membranes.
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Affiliation(s)
- Aleyna Benson
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Michael McMurray
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
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8
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Ibanes S, El-Alaoui F, Lai-Kee-Him J, Cazevieille C, Hoh F, Lyonnais S, Bron P, Cipelletti L, Picas L, Piatti S. The Syp1/FCHo2 protein induces septin filament bundling through its intrinsically disordered domain. Cell Rep 2022; 41:111765. [PMID: 36476870 DOI: 10.1016/j.celrep.2022.111765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 09/30/2022] [Accepted: 11/10/2022] [Indexed: 12/12/2022] Open
Abstract
The septin collar of budding yeast is an ordered array of septin filaments that serves a scaffolding function for the cytokinetic machinery at the bud neck and compartmentalizes the membrane between mother and daughter cell. How septin architecture is aided by septin-binding proteins is largely unknown. Syp1 is an endocytic protein that was implicated in the timely recruitment of septins to the newly forming collar through an unknown mechanism. Using advanced microscopy and in vitro reconstitution assays, we show that Syp1 is able to align laterally and tightly pack septin filaments, thereby forming flat bundles or sheets. This property is shared by the Syp1 mammalian counterpart FCHo2, thus emphasizing conserved protein functions. Interestingly, the septin-bundling activity of Syp1 resides mainly in its intrinsically disordered region. Our data uncover the mechanism through which Syp1 promotes septin collar assembly and offer another example of functional diversity of unstructured protein domains.
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Affiliation(s)
- Sandy Ibanes
- CRBM (Centre de Recherche en Biologie cellulaire de Montpellier), University of Montpellier, CNRS UMR 5237, 1919 Route de Mende, 34293 Montpellier, France
| | - Fatima El-Alaoui
- IRIM (Institut de Recherche en Infectiologie de Montpellier), University of Montpellier, CNRS UMR 9004, 1919 Route de Mende, 34293 Montpellier, France
| | - Joséphine Lai-Kee-Him
- CBS (Centre de Biologie Structurale), University of Montpellier, CNRS UMR 5048, INSERM U 1054, 29 Rue de Navacelles, 34090 Montpellier, France
| | - Chantal Cazevieille
- COMET Electron Microscopy Platform, INM (Institute for Neurosciences of Montpellier), University of Montpellier, INSERM U 1298, 80 Rue Augustin Fliche, 34091 Montpellier, France
| | - François Hoh
- CBS (Centre de Biologie Structurale), University of Montpellier, CNRS UMR 5048, INSERM U 1054, 29 Rue de Navacelles, 34090 Montpellier, France
| | - Sébastien Lyonnais
- CEMIPAI (Centre d'Etudes des Maladies Infectieuses et Pharmacologie Anti-Infectieuse), University of Montpellier, UAR 3725 CNRS, Montpellier, France
| | - Patrick Bron
- CBS (Centre de Biologie Structurale), University of Montpellier, CNRS UMR 5048, INSERM U 1054, 29 Rue de Navacelles, 34090 Montpellier, France
| | - Luca Cipelletti
- L2C (Laboratoire Charles Coulomb), University of Montpellier, CNRS, Place E. Bataillon, 34095 Montpellier, France; IUF (Institut Universitaire de France), Paris, France
| | - Laura Picas
- IRIM (Institut de Recherche en Infectiologie de Montpellier), University of Montpellier, CNRS UMR 9004, 1919 Route de Mende, 34293 Montpellier, France
| | - Simonetta Piatti
- CRBM (Centre de Recherche en Biologie cellulaire de Montpellier), University of Montpellier, CNRS UMR 5237, 1919 Route de Mende, 34293 Montpellier, France.
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9
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Panagiotou TC, Chen A, Wilde A. An anillin-CIN85-SEPT9 complex promotes intercellular bridge maturation required for successful cytokinesis. Cell Rep 2022; 40:111274. [PMID: 36044846 DOI: 10.1016/j.celrep.2022.111274] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 07/17/2022] [Accepted: 08/05/2022] [Indexed: 11/20/2022] Open
Abstract
Cleavage of one cell into two is the most dramatic event in the life of a cell. Plasma membrane fission occurs within a narrow intercellular bridge (ICB) between the daughter cells, but the mechanisms underlying ICB formation and maturation are poorly understood. Here we identify CIN85 as an ICB assembly factor and demonstrate its requirement for robust and timely cytokinesis. CIN85 interacts directly with the N-terminal region of anillin and SEPT9 and thereby facilitates SEPT9-containing filament localization to the plasma membrane of the ICB. In contrast, the C-terminal pleckstrin homology (PH) domain of anillin binds to septin units lacking SEPT9 but enriched in SEPT11. Anillin's interactions with distinct septin units are required to promote ICB elongation and maturation that, we propose, generate the physical space into which the abscission machinery is recruited to drive the final membrane scission event releasing two independent daughter cells.
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Affiliation(s)
- Thomas C Panagiotou
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1M1, Canada
| | - Anan Chen
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1M1, Canada
| | - Andrew Wilde
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1M1, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1M1, Canada.
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10
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In vitro investigation of protein assembly by combined microscopy and infrared spectroscopy at the nanometer scale. Proc Natl Acad Sci U S A 2022; 119:e2200019119. [PMID: 35914130 PMCID: PMC9371722 DOI: 10.1073/pnas.2200019119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The nanoscale structure and dynamics of proteins on surfaces has been extensively studied using various imaging techniques, such as transmission electron microscopy and atomic force microscopy (AFM) in liquid environments. These powerful imaging techniques, however, can potentially damage or perturb delicate biological material and do not provide chemical information, which prevents a fundamental understanding of the dynamic processes underlying their evolution under physiological conditions. Here, we use a platform developed in our laboratory that enables acquisition of infrared (IR) spectroscopy and AFM images of biological material in physiological liquids with nanometer resolution in a cell closed by atomically thin graphene membranes transparent to IR photons. In this work, we studied the self-assembly process of S-layer proteins at the graphene-aqueous solution interface. The graphene acts also as the membrane separating the solution containing the proteins and Ca2+ ions from the AFM tip, thus eliminating sample damage and contamination effects. The formation of S-layer protein lattices and their structural evolution was monitored by AFM and by recording the amide I and II IR absorption bands, which reveal the noncovalent interaction between proteins and their response to the environment, including ionic strength and solvation. Our measurement platform opens unique opportunities to study biological material and soft materials in general.
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11
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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: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [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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12
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Guan M, Wang M, Zhanghao K, Zhang X, Li M, Liu W, Niu J, Yang X, Chen L, Jing Z, Zhang MQ, Jin D, Xi P, Gao J. Polarization modulation with optical lock-in detection reveals universal fluorescence anisotropy of subcellular structures in live cells. LIGHT, SCIENCE & APPLICATIONS 2022; 11:4. [PMID: 34974519 PMCID: PMC8720311 DOI: 10.1038/s41377-021-00689-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 11/05/2021] [Accepted: 11/27/2021] [Indexed: 05/05/2023]
Abstract
The orientation of fluorophores can reveal crucial information about the structure and dynamics of their associated subcellular organelles. Despite significant progress in super-resolution, fluorescence polarization microscopy remains limited to unique samples with relatively strong polarization modulation and not applicable to the weak polarization signals in samples due to the excessive background noise. Here we apply optical lock-in detection to amplify the weak polarization modulation with super-resolution. This novel technique, termed optical lock-in detection super-resolution dipole orientation mapping (OLID-SDOM), could achieve a maximum of 100 frames per second and rapid extraction of 2D orientation, and distinguish distance up to 50 nm, making it suitable for monitoring structural dynamics concerning orientation changes in vivo. OLID-SDOM was employed to explore the universal anisotropy of a large variety of GFP-tagged subcellular organelles, including mitochondria, lysosome, Golgi, endosome, etc. We found that OUF (Orientation Uniformity Factor) of OLID-SDOM can be specific for different subcellular organelles, indicating that the anisotropy was related to the function of the organelles, and OUF can potentially be an indicator to distinguish normal and abnormal cells (even cancer cells). Furthermore, dual-color super-resolution OLID-SDOM imaging of lysosomes and actins demonstrates its potential in studying dynamic molecular interactions. The subtle anisotropy changes of expanding and shrinking dendritic spines in live neurons were observed with real-time OLID-SDOM. Revealing previously unobservable fluorescence anisotropy in various samples and indicating their underlying dynamic molecular structural changes, OLID-SDOM expands the toolkit for live cell research.
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Affiliation(s)
- Meiling Guan
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, 100871, China
| | - Miaoyan Wang
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, 100871, China
| | - Karl Zhanghao
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, 100871, China
- UTS-SUStech Joint Research Centre for Biomedical Materials & Devices, Department of Biomedical Engineering, College of Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Xu Zhang
- MOE Key Laboratory of Bioinformatics, Bioinformatics Division, Center for Synthetic & Systems Biology, BNRist, Beijing, China
- Center for Synthetic & Systems Biology; Department of Automation, Tsinghua University, Beijing, 100084, China
- Beijing Institute of Collaborative Innovation, Beijing, 100094, China
| | - Meiqi Li
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, 100871, China
| | - Wenhui Liu
- Center for Synthetic & Systems Biology; Department of Automation, Tsinghua University, Beijing, 100084, China
| | - Jing Niu
- MOE Key Laboratory of Bioinformatics, Bioinformatics Division, Center for Synthetic & Systems Biology, BNRist, Beijing, China
| | - Xusan Yang
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, 100871, China
| | - Long Chen
- MOE Key Laboratory of Bioinformatics, Bioinformatics Division, Center for Synthetic & Systems Biology, BNRist, Beijing, China
- Center for Synthetic & Systems Biology; Department of Automation, Tsinghua University, Beijing, 100084, China
| | - Zhenli Jing
- MOE Key Laboratory of Bioinformatics, Bioinformatics Division, Center for Synthetic & Systems Biology, BNRist, Beijing, China
| | - Micheal Q Zhang
- MOE Key Laboratory of Bioinformatics, Bioinformatics Division, Center for Synthetic & Systems Biology, BNRist, Beijing, China
- Department of Biological Sciences and Center for System Biology, The University of Texas at Dallas, Richardson, 75080, USA
- School of Medical Sciences, Tsinghua University, Beijing, 100084, China
| | - Dayong Jin
- UTS-SUStech Joint Research Centre for Biomedical Materials & Devices, Department of Biomedical Engineering, College of Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China
- Institute for Biomedical Materials and Devices (IBMD), Faculty of Science, University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Peng Xi
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, 100871, China
- UTS-SUStech Joint Research Centre for Biomedical Materials & Devices, Department of Biomedical Engineering, College of Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China
- National Biomedical Imaging Center, Peking University, Beijing, 100871, China
| | - Juntao Gao
- MOE Key Laboratory of Bioinformatics, Bioinformatics Division, Center for Synthetic & Systems Biology, BNRist, Beijing, China.
- Center for Synthetic & Systems Biology; Department of Automation, Tsinghua University, Beijing, 100084, China.
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13
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Marquardt J, Chen X, Bi E. Septin Assembly and Remodeling at the Cell Division Site During the Cell Cycle. Front Cell Dev Biol 2021; 9:793920. [PMID: 34901034 PMCID: PMC8656427 DOI: 10.3389/fcell.2021.793920] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 11/08/2021] [Indexed: 11/17/2022] Open
Abstract
The septin family of proteins can assemble into filaments that further organize into different higher order structures to perform a variety of different functions in different cell types and organisms. In the budding yeast Saccharomyces cerevisiae, the septins localize to the presumptive bud site as a cortical ring prior to bud emergence, expand into an hourglass at the bud neck (cell division site) during bud growth, and finally “split” into a double ring sandwiching the cell division machinery during cytokinesis. While much work has been done to understand the functions and molecular makeups of these structures, the mechanisms underlying the transitions from one structure to another have largely remained elusive. Recent studies involving advanced imaging and in vitro reconstitution have begun to reveal the vast complexity involved in the regulation of these structural transitions, which defines the focus of discussion in this mini-review.
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Affiliation(s)
- Joseph Marquardt
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Xi Chen
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
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14
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Lecinski S, Shepherd JW, Frame L, Hayton I, MacDonald C, Leake MC. Investigating molecular crowding during cell division and hyperosmotic stress in budding yeast with FRET. CURRENT TOPICS IN MEMBRANES 2021; 88:75-118. [PMID: 34862033 PMCID: PMC7612257 DOI: 10.1016/bs.ctm.2021.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cell division, aging, and stress recovery triggers spatial reorganization of cellular components in the cytoplasm, including membrane bound organelles, with molecular changes in their compositions and structures. However, it is not clear how these events are coordinated and how they integrate with regulation of molecular crowding. We use the budding yeast Saccharomyces cerevisiae as a model system to study these questions using recent progress in optical fluorescence microscopy and crowding sensing probe technology. We used a Förster Resonance Energy Transfer (FRET) based sensor, illuminated by confocal microscopy for high throughput analyses and Slimfield microscopy for single-molecule resolution, to quantify molecular crowding. We determine crowding in response to cellular growth of both mother and daughter cells, in addition to osmotic stress, and reveal hot spots of crowding across the bud neck in the burgeoning daughter cell. This crowding might be rationalized by the packing of inherited material, like the vacuole, from mother cells. We discuss recent advances in understanding the role of crowding in cellular regulation and key current challenges and conclude by presenting our recent advances in optimizing FRET-based measurements of crowding while simultaneously imaging a third color, which can be used as a marker that labels organelle membranes. Our approaches can be combined with synchronized cell populations to increase experimental throughput and correlate molecular crowding information with different stages in the cell cycle.
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Affiliation(s)
- Sarah Lecinski
- Department of Physics, University of York, York, United Kingdom
| | - Jack W Shepherd
- Department of Physics, University of York, York, United Kingdom; Department of Biology, University of York, York, United Kingdom
| | - Lewis Frame
- School of Natural Sciences, University of York, York, United Kingdom
| | - Imogen Hayton
- Department of Biology, University of York, York, United Kingdom
| | - Chris MacDonald
- Department of Biology, University of York, York, United Kingdom
| | - Mark C Leake
- Department of Physics, University of York, York, United Kingdom; Department of Biology, University of York, York, United Kingdom.
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15
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Yao L, Zhang L, Chen L, Gong X, Zhong J, Wang B, Fei Y, Mi L, Ma J. Dynamic Structure of Yeast Septin by Fast Fluctuation-Enhanced Structured Illumination Microscopy. Microorganisms 2021; 9:microorganisms9112255. [PMID: 34835381 PMCID: PMC8620077 DOI: 10.3390/microorganisms9112255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/23/2021] [Accepted: 10/25/2021] [Indexed: 12/05/2022] Open
Abstract
When Saccharomyces cerevisiae divides, a structure composed of different septin proteins arranged according to a certain rule is formed at the cell division site. The structure undergoes multiple remodeling stages during the cell cycle, thus guiding the yeast cells to complete the entire division process. Although the higher-order structure of septins can be determined using electron microscopy, the septin’s dynamic processes are poorly understood because of limitations in living cell super-resolution imaging technology. Herein, we describe a high lateral resolution and temporal resolution technique, known as fast fluctuation-enhanced structured illumination microscopy (fFE-SIM), which more than doubles the SIM resolution at a frame rate of 38 Hz in living cells. This allows a highly dynamic and sparse septin structure to be observed in Saccharomyces cerevisiae.
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Affiliation(s)
- Longfang Yao
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, School of Information Science and Technology, Fudan University, 220 Handan Road, Shanghai 200433, China; (L.Y.); (L.C.); (X.G.); (Y.F.)
| | - Li Zhang
- Shanghai Engineering Research Center of Industrial Microorganisms, The Multiscale Research Institute of Complex Systems (MRICS), School of Life Sciences, Fudan University, 220 Handan Road, Shanghai 200433, China;
| | - Liwen Chen
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, School of Information Science and Technology, Fudan University, 220 Handan Road, Shanghai 200433, China; (L.Y.); (L.C.); (X.G.); (Y.F.)
| | - Xingyu Gong
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, School of Information Science and Technology, Fudan University, 220 Handan Road, Shanghai 200433, China; (L.Y.); (L.C.); (X.G.); (Y.F.)
| | - Jiahui Zhong
- Institute of Biomedical Engineering and Technology, Academy for Engineer and Technology, Fudan University, 220 Handan Road, Shanghai 200433, China;
| | - Baoju Wang
- Centre for Optical and Electromagnetic Research, Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China;
| | - Yiyan Fei
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, School of Information Science and Technology, Fudan University, 220 Handan Road, Shanghai 200433, China; (L.Y.); (L.C.); (X.G.); (Y.F.)
| | - Lan Mi
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, School of Information Science and Technology, Fudan University, 220 Handan Road, Shanghai 200433, China; (L.Y.); (L.C.); (X.G.); (Y.F.)
- Institute of Biomedical Engineering and Technology, Academy for Engineer and Technology, Fudan University, 220 Handan Road, Shanghai 200433, China;
- Correspondence: (L.M.); (J.M.)
| | - Jiong Ma
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, School of Information Science and Technology, Fudan University, 220 Handan Road, Shanghai 200433, China; (L.Y.); (L.C.); (X.G.); (Y.F.)
- Shanghai Engineering Research Center of Industrial Microorganisms, The Multiscale Research Institute of Complex Systems (MRICS), School of Life Sciences, Fudan University, 220 Handan Road, Shanghai 200433, China;
- Institute of Biomedical Engineering and Technology, Academy for Engineer and Technology, Fudan University, 220 Handan Road, Shanghai 200433, China;
- Correspondence: (L.M.); (J.M.)
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16
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POLArIS, a versatile probe for molecular orientation, revealed actin filaments associated with microtubule asters in early embryos. Proc Natl Acad Sci U S A 2021; 118:2019071118. [PMID: 33674463 DOI: 10.1073/pnas.2019071118] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Biomolecular assemblies govern the physiology of cells. Their function often depends on the changes in molecular arrangements of constituents, both in the positions and orientations. While recent advancements of fluorescence microscopy including super-resolution microscopy have enabled us to determine the positions of fluorophores with unprecedented accuracy, monitoring the orientation of fluorescently labeled molecules within living cells in real time is challenging. Fluorescence polarization microscopy (FPM) reports the orientation of emission dipoles and is therefore a promising solution. For imaging with FPM, target proteins need labeling with fluorescent probes in a sterically constrained manner, but because of difficulties in the rational three-dimensional design of protein connection, a universal method for constrained tagging with fluorophore was not available. Here, we report POLArIS, a genetically encoded and versatile probe for molecular orientation imaging. Instead of using a direct tagging approach, we used a recombinant binder connected to a fluorescent protein in a sterically constrained manner that can target specific biomolecules of interest by combining with phage display screening. As an initial test case, we developed POLArISact, which specifically binds to F-actin in living cells. We confirmed that the orientation of F-actin can be monitored by observing cells expressing POLArISact with FPM. In living starfish early embryos expressing POLArISact, we found actin filaments radially extending from centrosomes in association with microtubule asters during mitosis. By taking advantage of the genetically encoded nature, POLArIS can be used in a variety of living specimens, including whole bodies of developing embryos and animals, and also be expressed in a cell type/tissue specific manner.
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17
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Mendonça DC, Guimarães SL, Pereira HD, Pinto AA, de Farias MA, de Godoy AS, Araujo APU, van Heel M, Portugal RV, Garratt RC. An atomic model for the human septin hexamer by cryo-EM. J Mol Biol 2021; 433:167096. [PMID: 34116125 DOI: 10.1016/j.jmb.2021.167096] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 05/25/2021] [Accepted: 06/02/2021] [Indexed: 01/22/2023]
Abstract
In order to form functional filaments, human septins must assemble into hetero-oligomeric rod-like particles which polymerize end-to-end. The rules governing the assembly of these particles and the subsequent filaments are incompletely understood. Although crystallographic approaches have been successful in studying the separate components of the system, there has been difficulty in obtaining high resolution structures of the full particle. Here we report a first cryo-EM structure for a hexameric rod composed of human septins 2, 6 and 7 with a global resolution of ~3.6 Å and a local resolution of between ~3.0 Å and ~5.0 Å. By fitting the previously determined high-resolution crystal structures of the component subunits into the cryo-EM map, we are able to provide an essentially complete model for the particle. This exposes SEPT2 NC-interfaces at the termini of the hexamer and leaves internal cavities between the SEPT6-SEPT7 pairs. The floor of the cavity is formed by the two α0 helices including their polybasic regions. These are locked into place between the two subunits by interactions made with the α5 and α6 helices of the neighbouring monomer together with its polyacidic region. The cavity may serve to provide space allowing the subunits to move with respect to one another. The elongated particle shows a tendency to bend at its centre where two copies of SEPT7 form a homodimeric G-interface. Such bending is almost certainly related to the ability of septin filaments to recognize and even induce membrane curvature.
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Affiliation(s)
| | | | | | | | | | | | - Ana P U Araujo
- São Carlos Institute of Physics, USP, São Carlos, SP, Brazil
| | - Marin van Heel
- Brazilian Nanotechnology National Laboratory, CNPEM, Campinas, SP, Brazil
| | - Rodrigo V Portugal
- Brazilian Nanotechnology National Laboratory, CNPEM, Campinas, SP, Brazil.
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18
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Nakai N, Sato K, Tani T, Kawagishi M, Ka H, Saito K, Terada S. Development of nanobody-based POLArIS orientation probes enabled multi-color/multi-target orientation imaging in living cells. Biochem Biophys Res Commun 2021; 565:50-56. [PMID: 34090210 DOI: 10.1016/j.bbrc.2021.05.088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 05/26/2021] [Indexed: 10/21/2022]
Abstract
Fluorescence polarization microscopy (FPM) can visualize the dipole orientation of fluorescent molecules and has been used for analyzing architectural dynamics of biomolecules including cytoskeletal proteins. To monitor the orientation of target molecules by FPM, target molecules need to be labeled with fluorophores in a sterically constrained manner, so that the fluorophores do not freely rotate. Recently, a versatile probe for such labeling using fluorescent proteins, POLArIS (Probe for Orientation and Localization Assessment, recognizing specific Intracellular Structures of interest), was reported. POLArIS is a fusion protein consisting of a non-immunoglobulin-based recombinant binder Affimer and a green fluorescent protein (GFP), where the Affimer and GFP are rigidly connected to each other. POLArIS probe for molecules of interest can be developed through phage display screening of Affimer. This screening is followed by the rigid connection of fluorescent proteins to the selected Affimers. The Affimer-based POLArIS, however, cannot be used with animal immune libraries for selecting specific binder clones. In addition, multi-color FPM by POLArIS was not available due to the lack of color variations of POLArIS. In this study, we have developed new versions of POLArIS with nanobodies, which are compatible with animal immune libraries, and expanded color variations of POLArIS with cyan/green/yellow/red fluorescent proteins, enabling multi-color orientation imaging for multiple targets. Using nanobody-based POLArIS orientation probes, we performed two-color FPM of F-actin and vimentin in living cells. Furthermore, we made nanobody-based POLArIS probes that have different dipole orientations for adjusting the orientation of fluorescence polarization with respect to the target molecules. These nanobody-based POLArIS with options of colors and dipole orientations will enhance the performance of this probe for broader applications of fluorescence polarization imaging in living cells, tissues, and whole organisms.
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Affiliation(s)
- Nori Nakai
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo, 113-8519, Japan; Center for Brain Integration Research, TMDU, Bunkyo-ku, Tokyo, 113-8519, Japan.
| | - Keisuke Sato
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo, 113-8519, Japan; Center for Brain Integration Research, TMDU, Bunkyo-ku, Tokyo, 113-8519, Japan.
| | - Tomomi Tani
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ikeda, Osaka, 563-8577, Japan.
| | - Masahiko Kawagishi
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo, 113-8519, Japan; Center for Brain Integration Research, TMDU, Bunkyo-ku, Tokyo, 113-8519, Japan.
| | - Hiromasa Ka
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo, 113-8519, Japan; Center for Brain Integration Research, TMDU, Bunkyo-ku, Tokyo, 113-8519, Japan.
| | - Kenta Saito
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo, 113-8519, Japan; Center for Brain Integration Research, TMDU, Bunkyo-ku, Tokyo, 113-8519, Japan.
| | - Sumio Terada
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo, 113-8519, Japan; Center for Brain Integration Research, TMDU, Bunkyo-ku, Tokyo, 113-8519, Japan.
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19
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Ramakrishnan S, Stagno JR, Magidson V, Heinz WF, Wang YX. Dependence of phase transition uniformity on crystal sizes characterized using birefringence. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2021; 8:034301. [PMID: 34235229 PMCID: PMC8248999 DOI: 10.1063/4.0000098] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 04/29/2021] [Indexed: 06/13/2023]
Abstract
Solid-solid phase transitions (SSPTs) have been widely observed in crystals of organic or inorganic small-molecules. Although SSPTs in macromolecular crystals have been reported, the majority involve local atomic changes, such as those induced by changes in hydration. SSPTs driven by large conformational changes, however, can be more difficult to characterize since they often significantly disrupt lattice packing interactions. Such drastic changes make the cooperativity of molecular motion at the atomic level less easily achieved and more dependent on intrinsic properties of the crystal that define lattice order. Here, we investigate the effect of crystal size on the uniformity of SSPT in thin plate-like crystals of the adenine riboswitch aptamer RNA (riboA) by monitoring changes in crystal birefringence upon the diffusion of adenine ligand. The birefringence intensity is directly related to molecular order and the concurrent changes to polarizability of molecules that results from structural changes throughout the phase transition. The riboA crystals were loosely grouped into three categories (small, medium, and large) based on the surface area of the crystal plates. The time width of transition increased as a function of crystal size, ranging from ∼13 s for small crystals to ∼40 s for the largest crystal. Whereas the transitions in small crystals (<10 μm2) were mostly uniform throughout, the medium and large crystals exhibited large variations in the time and width of the transition peak depending on the region of the crystal being analyzed. Our study provides insight into the spatiotemporal behavior of phase transitions in crystals of biological molecules and is of general interest to time-resolved crystallographic studies, where the kinetics of conformational changes may be governed by the kinetics of an associated SSPT.
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Affiliation(s)
- Saminathan Ramakrishnan
- Structural Biophysics Laboratory, Centre for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, USA
| | - Jason R. Stagno
- Structural Biophysics Laboratory, Centre for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, USA
| | - Valentin Magidson
- Optical Microscopy and Analysis Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702, USA
| | - William F. Heinz
- Optical Microscopy and Analysis Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702, USA
| | - Yun-Xing Wang
- Structural Biophysics Laboratory, Centre for Cancer Research, National Cancer Institute, Frederick, Maryland 21702, USA
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20
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Optical vector field rotation and switching with near-unity transmission by fully developed chiral photonic crystals. Proc Natl Acad Sci U S A 2021; 118:2021304118. [PMID: 33853945 DOI: 10.1073/pnas.2021304118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
State-of-the-art nanostructured chiral photonic crystals (CPCs), metamaterials, and metasurfaces have shown giant optical rotatory power but are generally passive and beset with large optical losses and with inadequate performance due to limited size/interaction length and narrow operation bandwidth. In this work, we demonstrate by detailed theoretical modeling and experiments that a fully developed CPC, one for which the number of unit cells N is high enough that it acquires the full potentials of an ideal (N → ∞) crystal, will overcome the aforementioned limitations, leading to a new generation of versatile high-performance polarization manipulation optics. Such high-N CPCs are realized by field-assisted self-assembly of cholesteric liquid crystals to unprecedented thicknesses not possible with any other means. Characterization studies show that high-N CPCs exhibit broad transmission maxima accompanied by giant rotatory power, thereby enabling large (>π) polarization rotation with near-unity transmission over a large operation bandwidth. Polarization rotation is demonstrated to be independent of input polarization orientation and applies equally well on continuous-wave or ultrafast (picosecond to femtosecond) pulsed lasers of simple or complex (radial, azimuthal) vector fields. Liquid crystal-based CPCs also allow very wide tuning of the operation spectral range and dynamic polarization switching and control possibilities by virtue of several stimuli-induced index or birefringence changing mechanisms.
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21
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Wang X, Zhou W, Xu D, Yin J. Analysis and verification of fluorescence super-resolution microscopy via polarization modulation in reciprocal space. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2021; 38:337-343. [PMID: 33690462 DOI: 10.1364/josaa.406029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 01/05/2021] [Indexed: 06/12/2023]
Abstract
Based on the polarization property of fluorescent dipoles, fluorescence super-resolution microscopy recently has been proposed by modulating the polarization of the excitation light. In this technique, the super-resolution image is reconstructed by processing the polarization-modulated fluorescence image stack with an iteration algorithm. However, the mechanism of resolution improvement by polarization modulation has been questioned. In this paper, the mechanism of resolution enhancement by polarization modulation is analyzed in reciprocal space. The mathematical model and the reconstruction algorithm of fluorescence super-resolution microscopy via polarization modulation are proposed in reciprocal space. The corresponding simulation results and analysis show that polarization modulation can enlarge the highest detected spatial frequency of fluorescence microscopy to achieve super resolution, which verifies the role of polarization modulation in resolution improvement and provides a useful reference to study fluorescence super-resolution microscopy via polarization modulation in reciprocal space.
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22
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Synergistic role of nucleotides and lipids for the self-assembly of Shs1 septin oligomers. Biochem J 2021; 477:2697-2714. [PMID: 32726433 DOI: 10.1042/bcj20200199] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 07/07/2020] [Accepted: 07/09/2020] [Indexed: 12/25/2022]
Abstract
Budding yeast septins are essential for cell division and polarity. Septins assemble as palindromic linear octameric complexes. The function and ultra-structural organization of septins are finely governed by their molecular polymorphism. In particular, in budding yeast, the end subunit can stand either as Shs1 or Cdc11. We have dissected, here, for the first time, the behavior of the Shs1 protomer bound to membranes at nanometer resolution, in complex with the other septins. Using electron microscopy, we have shown that on membranes, Shs1 protomers self-assemble into rings, bundles, filaments or two-dimensional gauzes. Using a set of specific mutants we have demonstrated a synergistic role of both nucleotides and lipids for the organization and oligomerization of budding yeast septins. Besides, cryo-electron tomography assays show that vesicles are deformed by the interaction between Shs1 oligomers and lipids. The Shs1-Shs1 interface is stabilized by the presence of phosphoinositides, allowing the visualization of micrometric long filaments formed by Shs1 protomers. In addition, molecular modeling experiments have revealed a potential molecular mechanism regarding the selectivity of septin subunits for phosphoinositide lipids.
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23
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Myšková J, Rybakova O, Brynda J, Khoroshyy P, Bondar A, Lazar J. Directionality of light absorption and emission in representative fluorescent proteins. Proc Natl Acad Sci U S A 2020; 117:32395-32401. [PMID: 33273123 PMCID: PMC7768707 DOI: 10.1073/pnas.2017379117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 10/30/2020] [Indexed: 12/13/2022] Open
Abstract
Fluorescent molecules are like antennas: The rate at which they absorb light depends on their orientation with respect to the incoming light wave, and the apparent intensity of their emission depends on their orientation with respect to the observer. However, the directions along which the most important fluorescent molecules in biology, fluorescent proteins (FPs), absorb and emit light are generally not known. Our optical and X-ray investigations of FP crystals have now allowed us to determine the molecular orientations of the excitation and emission transition dipole moments in the FPs mTurquoise2, eGFP, and mCherry, and the photoconvertible FP mEos4b. Our results will allow using FP directionality in studies of molecular and biological processes, but also in development of novel bioengineering and bioelectronics applications.
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Affiliation(s)
- Jitka Myšková
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610 Prague 6, Czech Republic
| | - Olga Rybakova
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610 Prague 6, Czech Republic
- Institute of Microbiology, Czech Academy of Sciences, 37333 Nové Hrady, Czech Republic
| | - Jiří Brynda
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610 Prague 6, Czech Republic
- Institute of Molecular Genetics, Czech Academy of Sciences, 14220 Prague 4, Czech Republic
| | - Petro Khoroshyy
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610 Prague 6, Czech Republic
- Institute of Microbiology, Czech Academy of Sciences, 37333 Nové Hrady, Czech Republic
| | - Alexey Bondar
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610 Prague 6, Czech Republic
- Institute of Microbiology, Czech Academy of Sciences, 37333 Nové Hrady, Czech Republic
| | - Josef Lazar
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 16610 Prague 6, Czech Republic;
- Institute of Microbiology, Czech Academy of Sciences, 37333 Nové Hrady, Czech Republic
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24
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Woods BL, Gladfelter AS. The state of the septin cytoskeleton from assembly to function. Curr Opin Cell Biol 2020; 68:105-112. [PMID: 33188984 DOI: 10.1016/j.ceb.2020.10.007] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 10/01/2020] [Accepted: 10/08/2020] [Indexed: 01/09/2023]
Abstract
Septins are conserved guanine nucleotide-binding proteins that polymerize into filaments at the cell cortex or in association with other cytoskeletal proteins, such as actin or microtubules. As integral players in many morphogenic and signaling events, septins form scaffolds important for the recruitment of the cytokinetic machinery, organization of the plasma membrane, and orientation of cell polarity. Mutations in septins or their misregulation are associated with numerous diseases. Despite growing appreciation for the importance of septins in different aspects of cell biology and disease, septins remain relatively poorly understood compared with other cytoskeletal proteins. Here in this review, we highlight some of the recent developments of the last two years in the field of septin cell biology.
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Affiliation(s)
- Benjamin L Woods
- Biology Department, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Amy S Gladfelter
- Biology Department, University of North Carolina, Chapel Hill, NC, 27599, USA; Marine Biological Laboratory, Woods Hole, MA, 02543, USA.
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25
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Carim SC, Kechad A, Hickson GRX. Animal Cell Cytokinesis: The Rho-Dependent Actomyosin-Anilloseptin Contractile Ring as a Membrane Microdomain Gathering, Compressing, and Sorting Machine. Front Cell Dev Biol 2020; 8:575226. [PMID: 33117802 PMCID: PMC7575755 DOI: 10.3389/fcell.2020.575226] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 09/07/2020] [Indexed: 12/19/2022] Open
Abstract
Cytokinesis is the last step of cell division that partitions the cellular organelles and cytoplasm of one cell into two. In animal cells, cytokinesis requires Rho-GTPase-dependent assembly of F-actin and myosin II (actomyosin) to form an equatorial contractile ring (CR) that bisects the cell. Despite 50 years of research, the precise mechanisms of CR assembly, tension generation and closure remain elusive. This hypothesis article considers a holistic view of the CR that, in addition to actomyosin, includes another Rho-dependent cytoskeletal sub-network containing the scaffold protein, Anillin, and septin filaments (collectively termed anillo-septin). We synthesize evidence from our prior work in Drosophila S2 cells that actomyosin and anillo-septin form separable networks that are independently anchored to the plasma membrane. This latter realization leads to a simple conceptual model in which CR assembly and closure depend upon the micro-management of the membrane microdomains to which actomyosin and anillo-septin sub-networks are attached. During CR assembly, actomyosin contractility gathers and compresses its underlying membrane microdomain attachment sites. These microdomains resist this compression, which builds tension. During CR closure, membrane microdomains are transferred from the actomyosin sub-network to the anillo-septin sub-network, with which they flow out of the CR as it advances. This relative outflow of membrane microdomains regulates tension, reduces the circumference of the CR and promotes actomyosin disassembly all at the same time. According to this hypothesis, the metazoan CR can be viewed as a membrane microdomain gathering, compressing and sorting machine that intrinsically buffers its own tension through coordination of actomyosin contractility and anillo-septin-membrane relative outflow, all controlled by Rho. Central to this model is the abandonment of the dogmatic view that the plasma membrane is always readily deformable by the underlying cytoskeleton. Rather, the membrane resists compression to build tension. The notion that the CR might generate tension through resistance to compression of its own membrane microdomain attachment sites, can account for numerous otherwise puzzling observations and warrants further investigation using multiple systems and methods.
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Affiliation(s)
- Sabrya C. Carim
- CHU Sainte-Justine Research Center, Université de Montréal, Montréal, QC, Canada
| | - Amel Kechad
- CHU Sainte-Justine Research Center, Université de Montréal, Montréal, QC, Canada
| | - Gilles R. X. Hickson
- CHU Sainte-Justine Research Center, Université de Montréal, Montréal, QC, Canada
- Département de Pathologie et Biologie Cellulaire, Faculté de Médecine, Université de Montréal, Montréal, QC, Canada
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26
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Chen L, Chen X, Yang X, He C, Wang M, Xi P, Gao J. Advances of super-resolution fluorescence polarization microscopy and its applications in life sciences. Comput Struct Biotechnol J 2020; 18:2209-2216. [PMID: 32952935 PMCID: PMC7476067 DOI: 10.1016/j.csbj.2020.06.038] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Revised: 06/20/2020] [Accepted: 06/22/2020] [Indexed: 11/29/2022] Open
Abstract
Fluorescence polarization microscopy (FPM) analyzes both intensity and orientation of fluorescence dipole, and reflects the structural specificity of target molecules. It has become an important tool for studying protein organization, orientational order, and structural changes in cells. However, suffering from optical diffraction limit, conventional FPM has low orientation resolution and observation accuracy, as the polarization information is averaged by multiple fluorescent molecules within a diffraction-limited volume. Recently, novel super-resolution FPMs have been developed to break the diffraction barrier. In this review, we will introduce the recent progress to achieve sub-diffraction determination of dipole orientation. Biological applications, based on polarization analysis of fluorescence dipole, are also summarized, with focus on chromophore-target molecule interaction and molecular organization.
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Affiliation(s)
- Long Chen
- Department of Automation, Tsinghua University, 100084 Beijing, China.,MOE Key Laboratory of Bioinformatics; Bioinformatics Division, Center for Synthetic & Systems Biology, BNRist; Center for Synthetic & Systems Biology, Tsinghua University, 100084 Beijing, China
| | - Xingye Chen
- Department of Automation, Tsinghua University, 100084 Beijing, China
| | - Xusan Yang
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Chao He
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
| | - Miaoyan Wang
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Peng Xi
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Juntao Gao
- Department of Automation, Tsinghua University, 100084 Beijing, China.,MOE Key Laboratory of Bioinformatics; Bioinformatics Division, Center for Synthetic & Systems Biology, BNRist; Center for Synthetic & Systems Biology, Tsinghua University, 100084 Beijing, China
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27
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Chen X, Zhanghao K, Li M, Qiao C, Liu W, Xi P, Dai Q. Enhanced reconstruction of structured illumination microscopy on a polarized specimen. OPTICS EXPRESS 2020; 28:25642-25654. [PMID: 32907080 DOI: 10.1364/oe.395092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 06/27/2020] [Indexed: 06/11/2023]
Abstract
Structured illumination microscopy (SIM) requires polarization control to guarantee the high-contrast illumination pattern. However, this modulated polarization will induce artifacts in SIM when imaging fluorescent dipoles. Here we proposed the polarization weighted recombination of frequency components to reconstruct SIM data with suppressed artifacts and better resolving power. Both the simulation results and experimental data demonstrate that our algorithm can obtain isotropic resolution on dipoles and resolve a clearer structure in high-density sections compared to the conventional algorithm. Our work reinforces the SIM theory and paves the avenue for the application of SIM on a polarized specimen.
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28
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Farkašovský M. Septin architecture and function in budding yeast. Biol Chem 2020; 401:903-919. [PMID: 31913844 DOI: 10.1515/hsz-2019-0401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 12/28/2019] [Indexed: 01/22/2023]
Abstract
The septins constitute a conserved family of guanosine phosphate-binding and filament-forming proteins widespread across eukaryotic species. Septins appear to have two principal functions. One is to form a cortical diffusion barrier, like the septin collar at the bud neck of Saccharomyces cerevisiae, which prevents movement of membrane-associated proteins between the mother and daughter cells. The second is to serve as a polymeric scaffold for recruiting the proteins required for critical cellular processes to particular subcellular areas. In the last decade, structural information about the different levels of septin organization has appeared, but crucial structural determinants and factors responsible for septin assembly remain largely unknown. This review highlights recent findings on the architecture and function of septins and their remodeling with an emphasis on mitotically dividing budding yeasts.
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Affiliation(s)
- Marian Farkašovský
- Department of Biochemistry and Protein Structure, Institute of Molecular Biology SAS, Dubravska cesta 21, 84551 Bratislava, Slovak Republic
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29
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Bartle EI, Rao TC, Beggs RR, Dean WF, Urner TM, Kowalczyk AP, Mattheyses AL. Protein exchange is reduced in calcium-independent epithelial junctions. J Cell Biol 2020; 219:151763. [PMID: 32399559 PMCID: PMC7265307 DOI: 10.1083/jcb.201906153] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Revised: 01/29/2020] [Accepted: 03/11/2020] [Indexed: 12/29/2022] Open
Abstract
Desmosomes are cell–cell junctions that provide mechanical integrity to epithelial and cardiac tissues. Desmosomes have two distinct adhesive states, calcium-dependent and hyperadhesive, which balance tissue plasticity and strength. A highly ordered array of cadherins in the adhesive interface is hypothesized to drive hyperadhesion, but how desmosome structure confers adhesive state is still elusive. We employed fluorescence polarization microscopy to show that cadherin order is not required for hyperadhesion induced by pharmacologic and genetic approaches. FRAP experiments in cells treated with the PKCα inhibitor Gö6976 revealed that cadherins, plakoglobin, and desmoplakin have significantly reduced exchange in and out of hyperadhesive desmosomes. To test whether this was a result of enhanced keratin association, we used the desmoplakin mutant S2849G, which conferred reduced protein exchange. We propose that inside-out regulation of protein exchange modulates adhesive function, whereby proteins are “locked in” to hyperadhesive desmosomes while protein exchange confers plasticity on calcium-dependent desmosomes, thereby providing rapid control of adhesion.
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Affiliation(s)
- Emily I Bartle
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL
| | - Tejeshwar C Rao
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL
| | - Reena R Beggs
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL
| | - William F Dean
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL
| | - Tara M Urner
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL
| | - Andrew P Kowalczyk
- Departments of Cell Biology and Dermatology, Emory University, Atlanta, GA
| | - Alexa L Mattheyses
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL
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30
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Cytokinesis: An Anillin–RhoGEF Module Sets the Stage for Septin Double Ring Assembly. Curr Biol 2020; 30:R347-R349. [DOI: 10.1016/j.cub.2020.02.035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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31
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Chen X, Wang K, Svitkina T, Bi E. Critical Roles of a RhoGEF-Anillin Module in Septin Architectural Remodeling during Cytokinesis. Curr Biol 2020; 30:1477-1490.e3. [PMID: 32197082 DOI: 10.1016/j.cub.2020.02.023] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 12/23/2019] [Accepted: 02/10/2020] [Indexed: 12/24/2022]
Abstract
How septin architecture is remodeled from an hourglass to a double ring during cytokinesis in fungal and animal cells remains unknown. Here, we show that during the hourglass-to-double-ring transition in budding yeast, septins acquire a "zonal architecture" in which paired septin filaments that are organized along the mother-bud axis associate with circumferential single septin filaments, the Rho guanine-nucleotide-exchange factor (RhoGEF) Bud3, and the anillin-like protein Bud4 exclusively at the outer zones and with myosin-II filaments in the middle zone. Deletion of Bud3 or its Bud4-interacting domain, but not its RhoGEF domain, leads to a complete loss of the single filaments, whereas deletion of Bud4 or its Bud3-interacting domain destabilizes the transitional hourglass, especially at the mother side, with partial loss of both filament types. Deletion of Bud3 and Bud4 together further weakens the transitional structure and abolishes the double ring formation while causing no obvious defect in actomyosin ring constriction. This and further analyses suggest that Bud3 stabilizes the single filaments, whereas Bud4 strengthens the interaction between the paired and single filaments at the outer zones of the transitional hourglass, as well as in the double ring. This study reveals a striking zonal architecture for the transitional hourglass that pre-patterns two cytokinetic structures-a septin double ring and an actomyosin ring-and also defines the essential roles of a RhoGEF-anillin module in septin architectural remodeling during cytokinesis at the filament level.
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Affiliation(s)
- Xi Chen
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA
| | - Kangji Wang
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA
| | - Tatyana Svitkina
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA.
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32
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Yeast as a Model to Understand Actin-Mediated Cellular Functions in Mammals-Illustrated with Four Actin Cytoskeleton Proteins. Cells 2020; 9:cells9030672. [PMID: 32164332 PMCID: PMC7140605 DOI: 10.3390/cells9030672] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/05/2020] [Accepted: 03/05/2020] [Indexed: 12/31/2022] Open
Abstract
The budding yeast Saccharomyces cerevisiae has an actin cytoskeleton that comprises a set of protein components analogous to those found in the actin cytoskeletons of higher eukaryotes. Furthermore, the actin cytoskeletons of S. cerevisiae and of higher eukaryotes have some similar physiological roles. The genetic tractability of budding yeast and the availability of a stable haploid cell type facilitates the application of molecular genetic approaches to assign functions to the various actin cytoskeleton components. This has provided information that is in general complementary to that provided by studies of the equivalent proteins of higher eukaryotes and hence has enabled a more complete view of the role of these proteins. Several human functional homologues of yeast actin effectors are implicated in diseases. A better understanding of the molecular mechanisms underpinning the functions of these proteins is critical to develop improved therapeutic strategies. In this article we chose as examples four evolutionarily conserved proteins that associate with the actin cytoskeleton: (1) yeast Hof1p/mammalian PSTPIP1, (2) yeast Rvs167p/mammalian BIN1, (3) yeast eEF1A/eEF1A1 and eEF1A2 and (4) yeast Yih1p/mammalian IMPACT. We compare the knowledge on the functions of these actin cytoskeleton-associated proteins that has arisen from studies of their homologues in yeast with information that has been obtained from in vivo studies using live animals or in vitro studies using cultured animal cell lines.
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33
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Wang X, Zhang Y, Zhou W, Xu D, Yin J. Mapping the dipole orientation distribution within a super-resolution scale via fluorescence polarization modulation. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2020; 37:353-360. [PMID: 32118917 DOI: 10.1364/josaa.380805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 01/02/2020] [Indexed: 06/10/2023]
Abstract
Conventional fluorescence polarization microscopy has been largely used to monitor the orientation and the structural information of biomolecules labeled with fluorescence dipoles but suffers from the optical diffraction limit. Here, we put forward a novel algorithm to simultaneously acquire the super-resolution image and the effective orientation distribution information of dipole clusters at corresponding super-resolution. In this paper, the orientation distribution of dipole clusters is statistically modeled by its mean orientation and orientation deviation, which are, respectively, represented by the middle direction and the opening angle of a sector shape. According to this model and microscopy imaging theory, the joint reconstruction algorithm is deduced mathematically in detail based on the conjugate gradient least-squares method. By applying this algorithm to different samples, the reconstructed results prove more than twice the resolution of wide-field images and the orientation distribution information at corresponding spatial resolution. Furthermore, the high accuracy of this algorithm in reconstructing super-resolution orientation distribution information is verified by Monte Carlo simulations.
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34
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Nakai N, Sato K, Tani T, Saito K, Sato F, Terada S. Genetically encoded orientation probes for F-actin for fluorescence polarization microscopy. Microscopy (Oxf) 2020; 68:359-368. [PMID: 31264686 DOI: 10.1093/jmicro/dfz022] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 04/23/2019] [Accepted: 04/24/2019] [Indexed: 12/16/2022] Open
Abstract
Fluorescence polarization microscopy, which can visualize both position and orientation of fluorescent molecules, is useful for analyzing architectural dynamics of proteins in vivo, especially that of cytoskeletal proteins such as actin. Fluorescent phalloidin conjugates and SiR-actin can be used as F-actin orientation probes for fluorescence polarization microscopy, but a lack of appropriate methods for their introduction to living specimens especially to tissues, embryos, and whole animals hampers their applications to image the orientation of F-actin. To solve this problem, we have developed genetically encoded F-actin orientation probes for fluorescence polarization microscopy. We rigidly connected circular permutated green fluorescent protein (GFP) to the N-terminal α-helix of actin-binding protein Lifeact or utrophin calponin homology domain (UtrCH), and normal mEGFP to the C-terminal α-helix of UtrCH. After evaluation of ensemble and single particle fluorescence polarization with the instantaneous FluoPolScope, one of the constructs turned out to be suitable for practical usage in live cell imaging. Our new, genetically encoded F-actin orientation probe, which has a similar property of an F-actin probe to conventional GFP-UtrCH, is expected to report the 3D architecture of the actin cytoskeleton with fluorescence polarization microscopy, paving the way for both the single molecular orientation imaging in cultured cells and the sub-optical resolution architectural analysis of F-actin networks analysis of F-actin in various living systems.
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Affiliation(s)
- Nori Nakai
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.,Center for Brain Integration Research, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
| | - Keisuke Sato
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.,Center for Brain Integration Research, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
| | - Tomomi Tani
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Kenta Saito
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.,Center for Brain Integration Research, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
| | - Fumiya Sato
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.,Center for Brain Integration Research, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
| | - Sumio Terada
- Department of Neuroanatomy and Cellular Neurobiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.,Center for Brain Integration Research, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
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35
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Chen L, Wang M, Zhang X, Zhang M, Hu Y, Shi Z, Xi P, Gao J. Group-Sparsity-Based Super-Resolution Dipole Orientation Mapping. IEEE TRANSACTIONS ON MEDICAL IMAGING 2019; 38:2687-2694. [PMID: 30990177 DOI: 10.1109/tmi.2019.2910221] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The dipole orientation of fluorophores could be resolved by fluorescence polarization microscopy (FPM), which in turn reveals structural specificity for the labeled organelles. Conventional FPM can detect only the averaged fluorescence anisotropy collected from dipoles within the diffraction-limited volume. Super-resolution dipole orientation mapping (SDOM) method, which applies sparse deconvolution and least square estimation to fluorescence polarization modulation data, achieves the dipole orientation measurement within a sub-diffraction focal area. However, during SDOM analysis, some pixels with fluorescence signal are not resolved with orientation for relatively small adjusted R2. Here we report group-sparsity-based SDOM (GS-SDOM), which utilizes the relevance of modulation sequences to effectively improve the SDOM reconstruction model. More credible resolved dipole orientations with higher adjusted R2 can be mapped and false positive estimation for local dipole orientation is vitally corrected. In addition to achieving the same spatial super-resolution as SDOM does, GS-SDOM accesses more morphological information with more credible orientations and more accurate local dipole distribution estimation. During the GS-SDOM analysis of actin filaments in mammalian kidney cells, the dipole orientation of fluorescence is detected always parallel to the direction of the actin filaments. Also with dipole orientation information extracted by GS-SDOM, the reconstructed visual circle from intensity dimension is discerned as jointed by double close filaments and 3-dimensional co-localization is accomplished in the intersection of actin filaments.
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36
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Zhanghao K, Chen X, Liu W, Li M, Liu Y, Wang Y, Luo S, Wang X, Shan C, Xie H, Gao J, Chen X, Jin D, Li X, Zhang Y, Dai Q, Xi P. Super-resolution imaging of fluorescent dipoles via polarized structured illumination microscopy. Nat Commun 2019; 10:4694. [PMID: 31619676 PMCID: PMC6795901 DOI: 10.1038/s41467-019-12681-w] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 09/20/2019] [Indexed: 12/26/2022] Open
Abstract
Fluorescence polarization microscopy images both the intensity and orientation of fluorescent dipoles and plays a vital role in studying molecular structures and dynamics of bio-complexes. However, current techniques remain difficult to resolve the dipole assemblies on subcellular structures and their dynamics in living cells at super-resolution level. Here we report polarized structured illumination microscopy (pSIM), which achieves super-resolution imaging of dipoles by interpreting the dipoles in spatio-angular hyperspace. We demonstrate the application of pSIM on a series of biological filamentous systems, such as cytoskeleton networks and λ-DNA, and report the dynamics of short actin sliding across a myosin-coated surface. Further, pSIM reveals the side-by-side organization of the actin ring structures in the membrane-associated periodic skeleton of hippocampal neurons and images the dipole dynamics of green fluorescent protein-labeled microtubules in live U2OS cells. pSIM applies directly to a large variety of commercial and home-built SIM systems with various imaging modality. Polarization microscopy has been combined with single-molecule localization, but it’s often limited in either speed or resolution. Here the authors present polarized Structured Illumination Microscopy (pSIM), a method that uses polarized laser excitation to measure dye orientation during fast super-resolution live cell imaging.
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Affiliation(s)
- Karl Zhanghao
- Department of Biomedical Engineering, College of Engineering, Peking University, 100871, Beijing, China.
| | - Xingye Chen
- Department of Automation, Tsinghua University, 100084, Beijing, China
| | - Wenhui Liu
- Department of Automation, Tsinghua University, 100084, Beijing, China
| | - Meiqi Li
- Department of Biomedical Engineering, College of Engineering, Peking University, 100871, Beijing, China
| | - Yiqiong Liu
- PKU-IDG/McGovern Institute for Brain Research, Peking University, 100871, Beijing, China
| | - Yiming Wang
- PKU-IDG/McGovern Institute for Brain Research, Peking University, 100871, Beijing, China
| | - Sha Luo
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 100101, Beijing, China
| | - Xiao Wang
- State Key Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, 100871, Beijing, China
| | - Chunyan Shan
- College of Life Sciences, Peking University, 100871, Beijing, China
| | - Hao Xie
- Department of Automation, Tsinghua University, 100084, Beijing, China
| | - Juntao Gao
- Department of Automation, Tsinghua University, 100084, Beijing, China
| | - Xiaowei Chen
- State Key Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, 100871, Beijing, China
| | - Dayong Jin
- Institute for Biomedical Materials & Devices (IBMD), Faculty of Science, University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Xiangdong Li
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 100101, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Yan Zhang
- PKU-IDG/McGovern Institute for Brain Research, Peking University, 100871, Beijing, China
| | - Qionghai Dai
- Department of Automation, Tsinghua University, 100084, Beijing, China.
| | - Peng Xi
- Department of Biomedical Engineering, College of Engineering, Peking University, 100871, Beijing, China.
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37
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CHANDLER TALON, SHROFF HARI, OLDENBOURG RUDOLF, LA RIVIÈRE PATRICK. Spatio-angular fluorescence microscopy I. Basic theory. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2019; 36:1334-1345. [PMID: 31503559 PMCID: PMC7045726 DOI: 10.1364/josaa.36.001334] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 06/07/2019] [Indexed: 05/22/2023]
Abstract
We introduce the basic elements of a spatio-angular theory of fluorescence microscopy, providing a unified framework for analyzing systems that image single fluorescent dipoles and ensembles of overlapping dipoles that label biological molecules. We model an aplanatic microscope imaging an ensemble of fluorescent dipoles as a linear Hilbert-space operator, and we show that the operator takes a particularly convenient form when expressed in a basis of complex exponentials and spherical harmonics-a form we call the dipole spatio-angular transfer function. We discuss the implications of our analysis for all quantitative fluorescence microscopy studies and lay out a path toward a complete theory.
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Affiliation(s)
- TALON CHANDLER
- University of Chicago, Department of Radiology, Chicago, Illinois 60637, USA
| | - HARI SHROFF
- Section on High Resolution Optical Imaging, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
- Marine Biological Laboratory, Bell Center, Woods Hole, Massachusetts 02543, USA
| | - RUDOLF OLDENBOURG
- Marine Biological Laboratory, Bell Center, Woods Hole, Massachusetts 02543, USA
| | - PATRICK LA RIVIÈRE
- University of Chicago, Department of Radiology, Chicago, Illinois 60637, USA
- Marine Biological Laboratory, Bell Center, Woods Hole, Massachusetts 02543, USA
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38
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Membrane reshaping by micrometric curvature sensitive septin filaments. Nat Commun 2019; 10:420. [PMID: 30679428 PMCID: PMC6345803 DOI: 10.1038/s41467-019-08344-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 12/19/2018] [Indexed: 12/31/2022] Open
Abstract
Septins are cytoskeletal filaments that assemble at the inner face of the plasma membrane. They are localized at constriction sites and impact membrane remodeling. We report in vitro tools to examine how yeast septins behave on curved and deformable membranes. Septins reshape the membranes of Giant Unilamellar Vesicles with the formation of periodic spikes, while flattening smaller vesicles. We show that membrane deformations are associated to preferential arrangement of septin filaments on specific curvatures. When binding to bilayers supported on custom-designed periodic wavy patterns displaying positive and negative micrometric radii of curvatures, septin filaments remain straight and perpendicular to the curvature of the convex parts, while bending negatively to follow concave geometries. Based on these results, we propose a theoretical model that describes the deformations and micrometric curvature sensitivity observed in vitro. The model captures the reorganizations of septin filaments throughout cytokinesis in vivo, providing mechanistic insights into cell division. Septins are cytoskeletal filaments that localize at constriction sites and impact membrane remodeling. Here authors examine the curvature sensitivity of septins using bilayers on wavy patterns and derive a theoretical model that quantitatively describe the results.
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39
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Song L, Feng Y, Guo X, Shen Y, Wu D, Wu Z, Zhou C, Zhu L, Gao S, Liu W, Zhang X, Li Z. Ultrafast polarization bio-imaging based on coherent detection and time-stretch techniques. BIOMEDICAL OPTICS EXPRESS 2018; 9:6556-6568. [PMID: 31065449 PMCID: PMC6490988 DOI: 10.1364/boe.9.006556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 11/22/2018] [Accepted: 11/23/2018] [Indexed: 06/09/2023]
Abstract
Optical polarization imaging has played an important role in many biological and biomedical applications, as it provides a label-free and non-invasive detection scheme to reveal the polarization information of optical rotation, birefringence, and photoelasticity distribution inherent in biological samples. However, the imaging speeds of the previously demonstrated polarization imaging techniques were often limited by the slow frame rates of the arrayed imaging detectors, which usually run at frame rates of several hundred hertz. By combining the optical coherent detection of orthogonal polarizations and the optical time-stretch imaging technique, we achieved ultrafast polarization bio-imaging at an extremely fast record line scanning rate up to 100 MHz without averaging. We experimentally demonstrated the superior performance of our method by imaging three slices of different kinds of biological samples with the retrieved Jones matrix and polarization-sensitive information including birefringence and diattenuation. The proposed system in this paper may find potential applications for ultrafast polarization dynamics in living samples or some other advanced biomedical research.
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Affiliation(s)
- Lu Song
- Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou 510632, China
| | - Yuanhua Feng
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou 510632, China
| | - Xiaojie Guo
- Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou 510632, China
| | - Yuecheng Shen
- School of Electronics and Information Technology, Sun Yat-Sen University, Guangzhou 510006, China
| | - Daixuan Wu
- School of Electronics and Information Technology, Sun Yat-Sen University, Guangzhou 510006, China
| | - Zhenhua Wu
- Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou 510632, China
| | - Congran Zhou
- Department of Pharmacology, School of Medicine, Jinan University, Guangzhou 510632, China
| | - Linyan Zhu
- Department of Pharmacology, School of Medicine, Jinan University, Guangzhou 510632, China
| | - Shecheng Gao
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou 510632, China
| | - Weiping Liu
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou 510632, China
| | - Xuming Zhang
- Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China
| | - Zhaohui Li
- School of Electronics and Information Technology, Sun Yat-Sen University, Guangzhou 510006, China
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40
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Molecular mechanisms of contractile-ring constriction and membrane trafficking in cytokinesis. Biophys Rev 2018; 10:1649-1666. [PMID: 30448943 DOI: 10.1007/s12551-018-0479-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 11/06/2018] [Indexed: 12/14/2022] Open
Abstract
In this review, we discuss the molecular mechanisms of cytokinesis from plants to humans, with a focus on contribution of membrane trafficking to cytokinesis. Selection of the division site in fungi, metazoans, and plants is reviewed, as well as the assembly and constriction of a contractile ring in fungi and metazoans. We also provide an introduction to exocytosis and endocytosis, and discuss how they contribute to successful cytokinesis in eukaryotic cells. The conservation in the coordination of membrane deposition and cytoskeleton during cytokinesis in fungi, metazoans, and plants is highlighted.
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41
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Tamborrini D, Juanes MA, Ibanes S, Rancati G, Piatti S. Recruitment of the mitotic exit network to yeast centrosomes couples septin displacement to actomyosin constriction. Nat Commun 2018; 9:4308. [PMID: 30333493 PMCID: PMC6193047 DOI: 10.1038/s41467-018-06767-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 09/10/2018] [Indexed: 01/11/2023] Open
Abstract
In many eukaryotic organisms cytokinesis is driven by a contractile actomyosin ring (CAR) that guides membrane invagination. What triggers CAR constriction at a precise time of the cell cycle is a fundamental question. In budding yeast CAR is assembled via a septin scaffold at the division site. A Hippo-like kinase cascade, the Mitotic Exit Network (MEN), promotes mitotic exit and cytokinesis, but whether and how these two processes are independently controlled by MEN is poorly understood. Here we show that a critical function of MEN is to promote displacement of the septin ring from the division site, which in turn is essential for CAR constriction. This is independent of MEN control over mitotic exit and involves recruitment of MEN components to the spindle pole body (SPB). Ubiquitination of the SPB scaffold Nud1 inhibits MEN signaling at the end of mitosis and prevents septin ring splitting, thus silencing the cytokinetic machinery. The Mitotic Exit Network (MEN) promotes mitotic exit and cytokinesis but if and how MEN independently controls these two processes is unclear. Here, the authors report that MEN displaces septins from the cell division site to promote actomyosin ring constriction, independently of MEN control of mitotic exit.
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Affiliation(s)
- Davide Tamborrini
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), 1919 Route de Mende, 34293, Montpellier, France.,Max-Planck-Institute of Molecular Physiology, Otto-Hahn Str. 11, 44227, Dortmund, Germany
| | - Maria Angeles Juanes
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), 1919 Route de Mende, 34293, Montpellier, France.,Brandeis University, 415 South Street, Waltham, MA, 02454, USA
| | - Sandy Ibanes
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), 1919 Route de Mende, 34293, Montpellier, France
| | - Giulia Rancati
- Institute of Medical Biology, 8a Biomedical Grove, Singapore, 138648, Singapore
| | - Simonetta Piatti
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), 1919 Route de Mende, 34293, Montpellier, France.
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Marquardt J, Chen X, Bi E. Architecture, remodeling, and functions of the septin cytoskeleton. Cytoskeleton (Hoboken) 2018; 76:7-14. [PMID: 29979831 DOI: 10.1002/cm.21475] [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: 03/30/2018] [Revised: 06/05/2018] [Accepted: 06/22/2018] [Indexed: 01/22/2023]
Abstract
The septin family of proteins has fascinated cell biologists for decades due to the elaborate architecture they adopt in different eukaryotic cells. Whether they exist as rings, collars, or gauzes in different cell types and at different times in the cell cycle illustrates a complex series of regulation in structure. While the organization of different septin structures at the cortex of different cell types during the cell cycle has been described to various degrees, the exact structure and regulation at the filament level are still largely unknown. Recent advances in fluorescent and electron microscopy, as well as work in septin biochemistry, have allowed new insights into the aspects of septin architecture, remodeling, and function in many cell types. This mini-review highlights many of the recent findings with an emphasis on the budding yeast model.
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Affiliation(s)
- Joseph Marquardt
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Xi Chen
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Erfei Bi
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
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43
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Ge B, Zhou R, Takiguchi Y, Yaqoob Z, So PTC. Single-Shot Optical Anisotropy Imaging with Quantitative Polarization Interference Microscopy. LASER & PHOTONICS REVIEWS 2018; 12:1800070. [PMID: 30899335 PMCID: PMC6424346 DOI: 10.1002/lpor.201800070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Indexed: 06/01/2023]
Abstract
Optical anisotropy measurement is essential for material characterization and biological imaging. In order to achieve single-shot mapping of the birefringence parameters of anisotropic samples, a novel polarized light imaging concept is proposed, namely quantitative polarization interference microscopy (QPIM). QPIM can be realized through designing a compact polarization-resolved interference microscopy system that captures interferograms bearing sample's linear birefringence information. To extract the retardance and the orientation angle maps from a single-shot measurement, a mathematical model for QPIM is further developed. The QPIM system is validated by measuring a calibrated quarter-wave plate, whose fast-axis orientation angle and retardance are determined with great accuracies. The single-shot nature of QPIM further allows to measure the transient dynamics of birefringence changes in material containing anisotropic structures. This application is demonstrated by capturing transient retardance changes in a custom-designed parallel-aligned nematic liquid crystal-based device.
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Affiliation(s)
- Baoliang Ge
- Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge, MA 02139, USA, Department of Biological Engineering Massachusetts Institute of Technology Cambridge, MA 02139, USA, Laser Biomedical Research Center Massachusetts Institute of Technology Cambridge, MA 02139, USA
| | - Renjie Zhou
- Department of Biomedical Engineering The Chinese University of Hong Kong Shatin, New Territories, Hong Kong SAR, China,
| | - Yu Takiguchi
- Central Research Laboratory Hamamatsu Photonics K.K Hamamatsu, Shizuoka 434-8601, Japan
| | - Zahid Yaqoob
- Laser Biomedical Research Center Massachusetts Institute of Technology Cambridge, MA 02139, USA,
| | - Peter T C So
- Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge, MA 02139, USA, Department of Biological Engineering Massachusetts Institute of Technology Cambridge, MA 02139, USA, Laser Biomedical Research Center Massachusetts Institute of Technology Cambridge, MA 02139, USA
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44
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Wang X, Fei F, Qu J, Li C, Li Y, Zhang S. The role of septin 7 in physiology and pathological disease: A systematic review of current status. J Cell Mol Med 2018; 22:3298-3307. [PMID: 29602250 PMCID: PMC6010854 DOI: 10.1111/jcmm.13623] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Accepted: 03/05/2018] [Indexed: 12/22/2022] Open
Abstract
Septins are a conserved family of cytoskeletal GTPases present in different organisms, including yeast, drosophila, Caenorhabditis elegans and humans. In humans, septins are involved in various cellular processes, including exocytosis, apoptosis, leukemogenesis, carcinogenesis and neurodegeneration. Septin 7 is unique out of 13 human septins. Mammalian septin 6, septin 7, septin 2 and septin 9 coisolate together in complexes to form the core unit for the generation of the septin filaments. Physiological septin filaments are hetero‐oligomeric complexes consisting of core septin hexamers and octamers. Furthermore, septin 7 plays a crucial role in cytokinesis and mitosis. Septin 7 is localized to the filopodia and branches of developing hippocampal neurons, and is the most abundant septin in the adult rat forebrain as well as a structural component of the human and mouse sperm annuli. Septin 7 is crucial to the spine morphogenesis and dendrite growth in neurons, and is also a structural constituent of the annulus in human and mouse sperm. It can suppress growth of some tumours such as glioma and papillary thyroid carcinoma. However, the molecular mechanisms of involvement of septin 7 in human disease, especially in the development of cancer, remain unclear. This review focuses on the structure, function and mechanism of septin 7 in vivo, and summarizes the role of septin 7 in cell proliferation, cytokinesis, nervous and reproductive systems, as well as the underlying molecular events linking septin 7 to various diseases, such as Alzheimer's disease, schizophrenia, neuropsychiatric systemic lupus erythematosus, tumour and so on.
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Affiliation(s)
- Xinlu Wang
- Graduate School, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Department of Pathology, Tianjin Union Medical Center, Tianjin, China
| | - Fei Fei
- Department of Pathology, Tianjin Union Medical Center, Tianjin, China.,Nankai University School of Medicine, Nankai University, Tianjin, China
| | - Jie Qu
- Department of Pathology, Tianjin Union Medical Center, Tianjin, China.,Nankai University School of Medicine, Nankai University, Tianjin, China
| | - Chunyuan Li
- Department of Pathology, Tianjin Union Medical Center, Tianjin, China.,Nankai University School of Medicine, Nankai University, Tianjin, China
| | - Yuwei Li
- Department of Colorectal Surgery, Tianjin Union Medical Center, Tianjin, China
| | - Shiwu Zhang
- Department of Pathology, Tianjin Union Medical Center, Tianjin, China
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45
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Jung J, Kim J, Seo MK, Park Y. Measurements of polarization-dependent angle-resolved light scattering from individual microscopic samples using Fourier transform light scattering. OPTICS EXPRESS 2018; 26:7701-7711. [PMID: 29609322 DOI: 10.1364/oe.26.007701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 02/24/2018] [Indexed: 05/27/2023]
Abstract
We present a method to measure the vector-field light scattering of individual microscopic objects. The polarization-dependent optical field images are measured with quantitative phase imaging at the sample plane, and then numerically propagated to the far-field plane. This approach allows the two-dimensional polarization-dependent angle-resolved light scattered patterns from individual object to be obtained with high precision and sensitivity. Using this method, we present the measurements of the polarization-dependent light scattering of a liquid crystal droplet and individual silver nanowires over scattering angles of 50°. In addition, the spectroscopic extension of the polarization-dependent angle-resolved light scattering is demonstrated using wavelength-scanning illumination.
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46
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Orellana-Muñoz S, Dueñas-Santero E, Arnáiz-Pita Y, Del Rey F, Correa-Bordes J, Vázquez de Aldana CR. The anillin-related Int1 protein and the Sep7 septin collaborate to maintain cellular ploidy in Candida albicans. Sci Rep 2018; 8:2257. [PMID: 29396461 PMCID: PMC5797091 DOI: 10.1038/s41598-018-20249-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 01/15/2018] [Indexed: 11/13/2022] Open
Abstract
Variation in cell ploidy is a common feature of Candida albicans clinical isolates that are resistant to the antifungal drug fluconazole. Here, we report that the anillin-related protein Int1 interacts with septins for coupling cytokinesis with nuclear segregation. Loss of Int1 results in a rapid disassembly of duplicated septin rings from the bud neck at the onset of actomyosin ring contraction. Strikingly, this has no major impact on cytokinesis and septum formation. However, Int1 genetically interacts with the Sep7 septin, maintaining the diffusion barrier at the bud neck and guarantying a faithful nuclear segregation. Indeed, int1ΔΔ sep7ΔΔ mutant cells, in contrast to int1ΔΔ cdc10ΔΔ, undergo a premature activation of mitotic exit prior to the alignment of the mitotic spindle with the division axis, producing large multinucleated cells. Some of these multinucleated cells arise from trimeras similar to those observed upon fluconazole exposure. Finally, the defects in nuclear segregation could be in part due to the inability to maintain the Lte1 mitotic exit activator at the cortex of the daughter cell. These results suggest that Int1 and Sep7 play a role in maintaining genome stability by acting as a diffusion barrier for Lte1.
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Affiliation(s)
- Sara Orellana-Muñoz
- Instituto de Biología Funcional y Genómica, IBFG-CSIC. Universidad de Salamanca, Salamanca, Spain
| | | | - Yolanda Arnáiz-Pita
- Instituto de Biología Funcional y Genómica, IBFG-CSIC. Universidad de Salamanca, Salamanca, Spain
| | - Francisco Del Rey
- Instituto de Biología Funcional y Genómica, IBFG-CSIC. Universidad de Salamanca, Salamanca, Spain
| | - Jaime Correa-Bordes
- Departamento de Ciencias Biomédicas, Universidad de Extremadura, Badajoz, Spain
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47
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Bartle EI, Urner TM, Raju SS, Mattheyses AL. Desmoglein 3 Order and Dynamics in Desmosomes Determined by Fluorescence Polarization Microscopy. Biophys J 2018; 113:2519-2529. [PMID: 29212005 DOI: 10.1016/j.bpj.2017.09.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 09/18/2017] [Accepted: 09/21/2017] [Indexed: 11/24/2022] Open
Abstract
Desmosomes are macromolecular cell-cell junctions that provide adhesive strength in epithelial tissue. Desmosome function is inseparably linked to structure, and it is hypothesized that the arrangement, or order, of desmosomal cadherins in the intercellular space is critical for adhesive strength. However, due to desmosome size, molecular complexity, and dynamics, the role that order plays in adhesion is challenging to study. Herein, we present an excitation resolved fluorescence polarization microscopy approach to measure the spatiotemporal dynamics of order and disorder of the desmosomal cadherin desmoglein 3 (Dsg3) in living cells. Simulations were used to establish order factor as a robust metric for quantifying the spatiotemporal dynamics of order and disorder. Order factor measurements in keratinocytes showed the Dsg3 extracellular domain is ordered at the individual desmosome, single cell, and cell population levels compared to a series of disordered controls. Desmosomal adhesion is Ca2+ dependent, and reduction of extracellular Ca2+ leads to a loss of adhesion measured by dispase fragmentation assay (λ = 15.1 min). Live cell imaging revealed Dsg3 order decreased more rapidly (λ = 5.5 min), indicating that cadherin order is not required for adhesion. Our results suggest that rapid disordering of cadherins can communicate a change in extracellular Ca2+ concentration to the cell, leading to a downstream loss of adhesion. Fluorescence polarization is an effective bridge between protein structure and complex dynamics and the approach presented here is broadly applicable to studying order in macromolecular structures.
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Affiliation(s)
- Emily I Bartle
- Department of Cell Biology, Emory University, Atlanta, Georgia
| | - Tara M Urner
- Department of Cell Biology, Emory University, Atlanta, Georgia
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48
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Nordenfelt P, Moore TI, Mehta SB, Kalappurakkal JM, Swaminathan V, Koga N, Lambert TJ, Baker D, Waters JC, Oldenbourg R, Tani T, Mayor S, Waterman CM, Springer TA. Direction of actin flow dictates integrin LFA-1 orientation during leukocyte migration. Nat Commun 2017; 8:2047. [PMID: 29229906 PMCID: PMC5725580 DOI: 10.1038/s41467-017-01848-y] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 10/20/2017] [Indexed: 12/31/2022] Open
Abstract
Integrin αβ heterodimer cell surface receptors mediate adhesive interactions that provide traction for cell migration. Here, we test whether the integrin, when engaged to an extracellular ligand and the cytoskeleton, adopts a specific orientation dictated by the direction of actin flow on the surface of migrating cells. We insert GFP into the rigid, ligand-binding head of the integrin, model with Rosetta the orientation of GFP and its transition dipole relative to the integrin head, and measure orientation with fluorescence polarization microscopy. Cytoskeleton and ligand-bound integrins orient in the same direction as retrograde actin flow with their cytoskeleton-binding β-subunits tilted by applied force. The measurements demonstrate that intracellular forces can orient cell surface integrins and support a molecular model of integrin activation by cytoskeletal force. Our results place atomic, Å-scale structures of cell surface receptors in the context of functional and cellular, μm-scale measurements.
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Affiliation(s)
- Pontus Nordenfelt
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Program in Cellular and Molecular Medicine, Children's Hospital, and Department of Biological Chemistry and Molecular Pharmacology and Medicine, Harvard Medical School, Boston, MA, 02115, USA
- Division of Infection Medicine, Department of Clinical Sciences Lund, Faculty of Medicine, Lund University, Lund, 221 84, Sweden
| | - Travis I Moore
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Program in Cellular and Molecular Medicine, Children's Hospital, and Department of Biological Chemistry and Molecular Pharmacology and Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - Shalin B Mehta
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Chan Zuckerberg Biohub, San Francisco, CA, 94158, USA
| | - Joseph Mathew Kalappurakkal
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- National Center for Biological Sciences, Bangalore, 560065, India
| | - Vinay Swaminathan
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Cell Biology and Physiology Center, NHLBI, NIH, Bethesda, MD, 20824, USA
| | - Nobuyasu Koga
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, 98195, USA
- Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan
| | - Talley J Lambert
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - David Baker
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, 98195, USA
| | - Jennifer C Waters
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - Rudolf Oldenbourg
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
| | - Tomomi Tani
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
| | - Satyajit Mayor
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- National Center for Biological Sciences, Bangalore, 560065, India
| | - Clare M Waterman
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Cell Biology and Physiology Center, NHLBI, NIH, Bethesda, MD, 20824, USA
| | - Timothy A Springer
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.
- Program in Cellular and Molecular Medicine, Children's Hospital, and Department of Biological Chemistry and Molecular Pharmacology and Medicine, Harvard Medical School, Boston, MA, 02115, USA.
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49
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Spira F, Cuylen-Haering S, Mehta S, Samwer M, Reversat A, Verma A, Oldenbourg R, Sixt M, Gerlich DW. Cytokinesis in vertebrate cells initiates by contraction of an equatorial actomyosin network composed of randomly oriented filaments. eLife 2017; 6. [PMID: 29106370 PMCID: PMC5673306 DOI: 10.7554/elife.30867] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Accepted: 10/28/2017] [Indexed: 12/21/2022] Open
Abstract
The actomyosin ring generates force to ingress the cytokinetic cleavage furrow in animal cells, yet its filament organization and the mechanism of contractility is not well understood. We quantified actin filament order in human cells using fluorescence polarization microscopy and found that cleavage furrow ingression initiates by contraction of an equatorial actin network with randomly oriented filaments. The network subsequently gradually reoriented actin filaments along the cell equator. This strictly depended on myosin II activity, suggesting local network reorganization by mechanical forces. Cortical laser microsurgery revealed that during cytokinesis progression, mechanical tension increased substantially along the direction of the cell equator, while the network contracted laterally along the pole-to-pole axis without a detectable increase in tension. Our data suggest that an asymmetric increase in cortical tension promotes filament reorientation along the cytokinetic cleavage furrow, which might have implications for diverse other biological processes involving actomyosin rings.
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Affiliation(s)
- Felix Spira
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna Biocenter, Vienna, Austria
| | - Sara Cuylen-Haering
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna Biocenter, Vienna, Austria
| | - Shalin Mehta
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, United States
| | - Matthias Samwer
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna Biocenter, Vienna, Austria
| | - Anne Reversat
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Amitabh Verma
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, United States
| | - Rudolf Oldenbourg
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, United States
| | - Michael Sixt
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Daniel W Gerlich
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna Biocenter, Vienna, Austria
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50
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Swaminathan V, Kalappurakkal JM, Mehta SB, Nordenfelt P, Moore TI, Koga N, Baker DA, Oldenbourg R, Tani T, Mayor S, Springer TA, Waterman CM. Actin retrograde flow actively aligns and orients ligand-engaged integrins in focal adhesions. Proc Natl Acad Sci U S A 2017; 114:10648-10653. [PMID: 29073038 PMCID: PMC5635867 DOI: 10.1073/pnas.1701136114] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Integrins are transmembrane receptors that, upon activation, bind extracellular ligands and link them to the actin filament (F-actin) cytoskeleton to mediate cell adhesion and migration. Cytoskeletal forces in migrating cells generated by polymerization- or contractility-driven "retrograde flow" of F-actin from the cell leading edge have been hypothesized to mediate integrin activation for ligand binding. This predicts that these forces should align and orient activated, ligand-bound integrins at the leading edge. Here, polarization-sensitive fluorescence microscopy of GFP-αVβ3 integrins in fibroblasts shows that integrins are coaligned in a specific orientation within focal adhesions (FAs) in a manner dependent on binding immobilized ligand and a talin-mediated linkage to the F-actin cytoskeleton. These findings, together with Rosetta modeling, suggest that integrins in FA are coaligned and may be highly tilted by cytoskeletal forces. Thus, the F-actin cytoskeleton sculpts an anisotropic molecular scaffold in FAs, and this feature may underlie the ability of migrating cells to sense directional extracellular cues.
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Affiliation(s)
- Vinay Swaminathan
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA 02543
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD 20892
| | - Joseph Mathew Kalappurakkal
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA 02543
- National Centre for Biological Sciences, Bangalore 560065, Karnataka, India
| | - Shalin B Mehta
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA 02543
| | - Pontus Nordenfelt
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA 02543
- Division of Infection Medicine, Lund University, SE-221 84 Lund, Sweden
- Program in Cellular and Molecular Medicine, Children's Hospital, Boston, MA 02115
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Travis I Moore
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543
- Program in Cellular and Molecular Medicine, Children's Hospital, Boston, MA 02115
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Nobuyasu Koga
- Department of Biochemistry, University of Washington, Seattle, WA 98195
- Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195
- Institute for Molecular Science, Okazaki 444-8585, Japan
| | - David A Baker
- Department of Biochemistry, University of Washington, Seattle, WA 98195
- Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195
| | - Rudolf Oldenbourg
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA 02543
| | - Tomomi Tani
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA 02543
| | - Satyajit Mayor
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA 02543
- National Centre for Biological Sciences, Bangalore 560065, Karnataka, India
| | - Timothy A Springer
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543
- Program in Cellular and Molecular Medicine, Children's Hospital, Boston, MA 02115
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Clare M Waterman
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543;
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA 02543
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD 20892
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