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Sinclair R, Wang M, Jawaid MZ, Longkumer T, Aaron J, Rossetti B, Wait E, McDonald K, Cox D, Heddleston J, Wilkop T, Drakakaki G. Four-dimensional quantitative analysis of cell plate development using lattice light sheet microscopy identifies robust transition points between growth phases. J Exp Bot 2024:erae091. [PMID: 38436428 DOI: 10.1093/jxb/erae091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Indexed: 03/05/2024]
Abstract
Cell plate formation during cytokinesis entails multiple stages occurring concurrently and requiring orchestrated vesicle delivery, membrane remodeling, and timely polysaccharide deposition, such as callose. Understanding such a dynamic process requires dissection in time and space; this has been a major hurdle in studying cytokinesis. Using lattice light sheet microscopy (LLSM) we studied cell plate development in four dimensions, through the behavior of the cytokinesis specific GTPase YFP-RABA2a vesicles. We monitored the entire length of cell plate development, from its first emergence, with the aid of YFP-RABA2a, both in the presence and absence of cytokinetic callose. By developing a robust cytokinetic vesicle volume analysis pipeline, we identified distinct behavioral patterns, allowing the identification of three easily trackable, cell plate developmental phases. Notably, the phase transition between phase I and phase II is striking, indicating a switch from membrane accumulation to the recycling of excess membrane material. We interrogated the role of callose using pharmacological inhibition with LLSM and electron microscopy. Loss of callose inhibited the phase transitions, establishing the critical role and timing of the polysaccharide deposition in cell plate expansion and maturation. This study exemplifies the power of combining LLSM with quantitative analysis to decode and untangle such a complex process.
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Affiliation(s)
| | - Minmin Wang
- Department of Plant Sciences, University of California Davis
| | | | | | | | | | | | - Kent McDonald
- Electron Microscopy Facility, University of California Berkeley
| | - Daniel Cox
- Department of Physics and Astronomy, University of California Davis
| | | | - Thomas Wilkop
- Department of Molecular Cellular Biology, Light Microscope Core, University of California Davis
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2
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Neahring L, He Y, Cho NH, Liu G, Fernandes J, Rux CJ, Nakos K, Subramanian R, Upadhyayula S, Yildiz A, Dumont S. Torques within and outside the human spindle balance twist at anaphase. bioRxiv 2023:2023.12.10.570990. [PMID: 38405786 PMCID: PMC10888964 DOI: 10.1101/2023.12.10.570990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
At each cell division, nanometer-scale motors and microtubules give rise to the micron-scale spindle. Many mitotic motors step helically around microtubules in vitro, and most are predicted to twist the spindle in a left-handed direction. However, the human spindle exhibits only slight global twist, raising the question of how these molecular torques are balanced. Here, using lattice light sheet microscopy, we find that anaphase spindles in the epithelial cell line MCF10A have a high baseline twist, and we identify factors that both increase and decrease this twist. The midzone motors KIF4A and MKLP1 are redundantly required for left-handed twist at anaphase, and we show that KIF4A generates left-handed torque in vitro. The actin cytoskeleton also contributes to left-handed twist, but dynein and its cortical recruitment factor LGN counteract it. Together, our work demonstrates that force generators regulate twist in opposite directions from both within and outside the spindle, preventing strong spindle twist during chromosome segregation.
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Affiliation(s)
- Lila Neahring
- Department of Bioengineering & Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Developmental & Stem Cell Biology Graduate Program, University of California San Francisco, San Francisco, CA, USA
| | - Yifei He
- Department of Chemistry, University of California Berkeley, Berkeley, CA, USA
| | - Nathan H. Cho
- Department of Bioengineering & Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Tetrad Graduate Program, University of California San Francisco, San Francisco, CA, USA
| | - Gaoxiang Liu
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA
| | - Jonathan Fernandes
- Department of Chemistry, University of California Berkeley, Berkeley, CA, USA
| | - Caleb J. Rux
- Department of Bioengineering & Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- UC Berkeley/UC San Francisco Graduate Group in Bioengineering, Berkeley, CA, USA
| | - Konstantinos Nakos
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Radhika Subramanian
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Srigokul Upadhyayula
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - Ahmet Yildiz
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA
- Physics Department, University of California Berkeley, Berkeley, CA, USA
| | - Sophie Dumont
- Department of Bioengineering & Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Developmental & Stem Cell Biology Graduate Program, University of California San Francisco, San Francisco, CA, USA
- Tetrad Graduate Program, University of California San Francisco, San Francisco, CA, USA
- UC Berkeley/UC San Francisco Graduate Group in Bioengineering, Berkeley, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
- Department of Biochemistry & Biophysics, University of California San Francisco, San Francisco, CA, USA
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3
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Lutton JE, Coker HLE, Paschke P, Munn CJ, King JS, Bretschneider T, Kay RR. Formation and closure of macropinocytic cups in Dictyostelium. Curr Biol 2023; 33:3083-3096.e6. [PMID: 37379843 PMCID: PMC7614961 DOI: 10.1016/j.cub.2023.06.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 05/05/2023] [Accepted: 06/05/2023] [Indexed: 06/30/2023]
Abstract
Macropinocytosis is a conserved endocytic process by which cells engulf droplets of medium into micron-sized vesicles. We use light-sheet microscopy to define an underlying set of principles by which macropinocytic cups are shaped and closed in Dictyostelium amoebae. Cups form around domains of PIP3 stretching almost to their lip and are supported by a specialized F-actin scaffold from lip to base. They are shaped by a ring of actin polymerization created by recruiting Scar/WAVE and Arp2/3 around PIP3 domains, but how cups evolve over time to close and form a vesicle is unknown. Custom 3D analysis shows that PIP3 domains expand from small origins, capturing new membrane into the cup, and crucially, that cups close when domain expansion stalls. We show that cups can close in two ways: either at the lip, by inwardly directed actin polymerization, or the base, by stretching and delamination of the membrane. This provides the basis for a conceptual mechanism whereby closure is brought about by a combination of stalled cup expansion, continued actin polymerization at the lip, and membrane tension. We test this through the use of a biophysical model, which can recapitulate both forms of cup closure and explain how 3D cup structures evolve over time to mediate engulfment.
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Affiliation(s)
- Judith E Lutton
- Department of Computer Science, University of Warwick, Coventry CV4 7AL, UK
| | - Helena L E Coker
- CAMDU, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Peggy Paschke
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | | | - Jason S King
- School of Biosciences, Western Bank, Sheffield S10 2TN, UK.
| | - Till Bretschneider
- Department of Computer Science, University of Warwick, Coventry CV4 7AL, UK.
| | - Robert R Kay
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.
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4
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Saltukoglu D, Özdemir B, Holtmannspötter M, Reski R, Piehler J, Kurre R, Reth M. Plasma membrane topography governs the 3D dynamic localization of IgM B cell antigen receptor clusters. EMBO J 2023; 42:e112030. [PMID: 36594262 PMCID: PMC9929642 DOI: 10.15252/embj.2022112030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 12/04/2022] [Accepted: 12/06/2022] [Indexed: 01/04/2023] Open
Abstract
B lymphocytes recognize bacterial or viral antigens via different classes of the B cell antigen receptor (BCR). Protrusive structures termed microvilli cover lymphocyte surfaces, and are thought to perform sensory functions in screening antigen-bearing surfaces. Here, we have used lattice light-sheet microscopy in combination with tailored custom-built 4D image analysis to study the cell-surface topography of B cells of the Ramos Burkitt's Lymphoma line and the spatiotemporal organization of the IgM-BCR. Ramos B-cell surfaces were found to form dynamic networks of elevated ridges bridging individual microvilli. A fraction of membrane-localized IgM-BCR was found in clusters, which were mainly associated with the ridges and the microvilli. The dynamic ridge-network organization and the IgM-BCR cluster mobility were linked, and both were controlled by Arp2/3 complex activity. Our results suggest that dynamic topographical features of the cell surface govern the localization and transport of IgM-BCR clusters to facilitate antigen screening by B cells.
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Affiliation(s)
- Deniz Saltukoglu
- Department of Molecular Immunology, Biology III, Faculty of BiologyUniversity of FreiburgFreiburgGermany
- Signaling Research Centers CIBSS and BIOSSUniversity of FreiburgFreiburgGermany
| | - Bugra Özdemir
- Signaling Research Centers CIBSS and BIOSSUniversity of FreiburgFreiburgGermany
- Plant Biotechnology, Faculty of BiologyUniversity of FreiburgFreiburgGermany
- Present address:
Euro‐BioImaging, European Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | - Michael Holtmannspötter
- Department of Biology/Chemistry and Center for Cellular NanoanalyticsOsnabrück UniversityOsnabrückGermany
| | - Ralf Reski
- Signaling Research Centers CIBSS and BIOSSUniversity of FreiburgFreiburgGermany
- Plant Biotechnology, Faculty of BiologyUniversity of FreiburgFreiburgGermany
| | - Jacob Piehler
- Department of Biology/Chemistry and Center for Cellular NanoanalyticsOsnabrück UniversityOsnabrückGermany
| | - Rainer Kurre
- Department of Biology/Chemistry and Center for Cellular NanoanalyticsOsnabrück UniversityOsnabrückGermany
| | - Michael Reth
- Department of Molecular Immunology, Biology III, Faculty of BiologyUniversity of FreiburgFreiburgGermany
- Signaling Research Centers CIBSS and BIOSSUniversity of FreiburgFreiburgGermany
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5
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Colin-York H, Heddleston J, Wait E, Karedla N, deSantis M, Khuon S, Chew TL, Sbalzarini IF, Fritzsche M. Quantifying Molecular Dynamics within Complex Cellular Morphologies using LLSM-FRAP. Small Methods 2022; 6:e2200149. [PMID: 35344286 DOI: 10.1002/smtd.202200149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Indexed: 06/14/2023]
Abstract
Quantifying molecular dynamics within the context of complex cellular morphologies is essential toward understanding the inner workings and function of cells. Fluorescence recovery after photobleaching (FRAP) is one of the most broadly applied techniques to measure the reaction diffusion dynamics of molecules in living cells. FRAP measurements typically restrict themselves to single-plane image acquisition within a subcellular-sized region of interest due to the limited temporal resolution and undesirable photobleaching induced by 3D fluorescence confocal or widefield microscopy. Here, an experimental and computational pipeline combining lattice light sheet microscopy, FRAP, and numerical simulations, offering rapid and minimally invasive quantification of molecular dynamics with respect to 3D cell morphology is presented. Having the opportunity to accurately measure and interpret the dynamics of molecules in 3D with respect to cell morphology has the potential to reveal unprecedented insights into the function of living cells.
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Affiliation(s)
- Huw Colin-York
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK
- Kennedy Institute for Rheumatology, University of Oxford, Oxford, OX3 7LF, UK
| | - John Heddleston
- Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA 20147, USA
| | - Eric Wait
- Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA 20147, USA
| | - Narain Karedla
- Rosalind Franklin Institute, Harwell Campus, Didcot, OX11 0FA, UK
| | - Michael deSantis
- Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA 20147, USA
| | - Satya Khuon
- Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA 20147, USA
| | - Teng-Leong Chew
- Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA 20147, USA
| | - Ivo F Sbalzarini
- Faculty of Computer Science, Technische Universität Dresden, 01187, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307, Dresden, Germany
| | - Marco Fritzsche
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK
- Kennedy Institute for Rheumatology, University of Oxford, Oxford, OX3 7LF, UK
- Rosalind Franklin Institute, Harwell Campus, Didcot, OX11 0FA, UK
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6
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Brameshuber M, Klotzsch E, Ponjavic A, Sezgin E. Understanding immune signaling using advanced imaging techniques. Biochem Soc Trans 2022:BST20210479. [PMID: 35343569 DOI: 10.1042/BST20210479] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 03/07/2022] [Accepted: 03/08/2022] [Indexed: 12/13/2022]
Abstract
Advanced imaging is key for visualizing the spatiotemporal regulation of immune signaling which is a complex process involving multiple players tightly regulated in space and time. Imaging techniques vary in their spatial resolution, spanning from nanometers to micrometers, and in their temporal resolution, ranging from microseconds to hours. In this review, we summarize state-of-the-art imaging methodologies and provide recent examples on how they helped to unravel the mysteries of immune signaling. Finally, we discuss the limitations of current technologies and share our insights on how to overcome these limitations to visualize immune signaling with unprecedented fidelity.
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7
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Balagopalan L, Raychaudhuri K, Samelson LE. Microclusters as T Cell Signaling Hubs: Structure, Kinetics, and Regulation. Front Cell Dev Biol 2021; 8:608530. [PMID: 33575254 PMCID: PMC7870797 DOI: 10.3389/fcell.2020.608530] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 12/10/2020] [Indexed: 11/16/2022] Open
Abstract
When T cell receptors (TCRs) engage with stimulatory ligands, one of the first microscopically visible events is the formation of microclusters at the site of T cell activation. Since the discovery of these structures almost 20 years ago, they have been studied extensively in live cells using confocal and total internal reflection fluorescence (TIRF) microscopy. However, due to limits in image resolution and acquisition speed, the spatial relationships of signaling components within microclusters, the kinetics of their assembly and disassembly, and the role of vesicular trafficking in microcluster formation and maintenance were not finely characterized. In this review, we will summarize how new microscopy techniques have revealed novel insights into the assembly of these structures. The sub-diffraction organization of microclusters as well as the finely dissected kinetics of recruitment and disassociation of molecules from microclusters will be discussed. The role of cell surface molecules in microcluster formation and the kinetics of molecular recruitment via intracellular vesicular trafficking to microclusters is described. Finally, the role of post-translational modifications such as ubiquitination in the downregulation of cell surface signaling molecules is also discussed. These results will be related to the role of these structures and processes in T cell activation.
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Affiliation(s)
- Lakshmi Balagopalan
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States
| | - Kumarkrishna Raychaudhuri
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States
| | - Lawrence E Samelson
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, United States
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8
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Quinney KB, Frankel EB, Shankar R, Kasberg W, Luong P, Audhya A. Growth factor stimulation promotes multivesicular endosome biogenesis by prolonging recruitment of the late-acting ESCRT machinery. Proc Natl Acad Sci U S A 2019; 116:6858-67. [PMID: 30894482 DOI: 10.1073/pnas.1817898116] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The formation of multivesicular endosomes (MVEs) mediates the turnover of numerous integral membrane proteins and has been implicated in the down-regulation of growth factor signaling, thereby exhibiting properties of a tumor suppressor. The endosomal sorting complex required for transport (ESCRT) machinery plays a key role in MVE biogenesis, enabling cargo selection and intralumenal vesicle (ILV) budding. However, the spatiotemporal pattern of endogenous ESCRT complex assembly and disassembly in mammalian cells remains poorly defined. By combining CRISPR/Cas9-mediated genome editing and live cell imaging using lattice light sheet microscopy (LLSM), we determined the native dynamics of both early- and late-acting ESCRT components at MVEs under multiple growth conditions. Specifically, our data indicate that ESCRT-0 accumulates quickly on endosomes, typically in less than 30 seconds, and its levels oscillate in a manner dependent on the downstream recruitment of ESCRT-I. Similarly, levels of the ESCRT-I complex also fluctuate on endosomes, but its average residency time is more than fivefold shorter compared with ESCRT-0. Vps4 accumulation is the most transient, however, suggesting that the completion of ILV formation occurs rapidly. Upon addition of epidermal growth factor (EGF), both ESCRT-I and Vps4 are retained at endosomes for dramatically extended periods of time, while ESCRT-0 dynamics are only modestly affected. Our findings are consistent with a model in which growth factor stimulation stabilizes late-acting components of the ESCRT machinery at endosomes to accelerate the rate of ILV biogenesis and attenuate signal transduction initiated by receptor activation.
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9
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Adell MAY, Migliano SM, Upadhyayula S, Bykov YS, Sprenger S, Pakdel M, Vogel GF, Jih G, Skillern W, Behrouzi R, Babst M, Schmidt O, Hess MW, Briggs JA, Kirchhausen T, Teis D. Recruitment dynamics of ESCRT-III and Vps4 to endosomes and implications for reverse membrane budding. eLife 2017; 6:31652. [PMID: 29019322 PMCID: PMC5665648 DOI: 10.7554/elife.31652] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 09/25/2017] [Indexed: 12/18/2022] Open
Abstract
The ESCRT machinery mediates reverse membrane scission. By quantitative fluorescence lattice light-sheet microscopy, we have shown that ESCRT-III subunits polymerize rapidly on yeast endosomes, together with the recruitment of at least two Vps4 hexamers. During their 3–45 s lifetimes, the ESCRT-III assemblies accumulated 75–200 Snf7 and 15–50 Vps24 molecules. Productive budding events required at least two additional Vps4 hexamers. Membrane budding was associated with continuous, stochastic exchange of Vps4 and ESCRT-III components, rather than steady growth of fixed assemblies, and depended on Vps4 ATPase activity. An all-or-none step led to final release of ESCRT-III and Vps4. Tomographic electron microscopy demonstrated that acute disruption of Vps4 recruitment stalled membrane budding. We propose a model in which multiple Vps4 hexamers (four or more) draw together several ESCRT-III filaments. This process induces cargo crowding and inward membrane buckling, followed by constriction of the nascent bud neck and ultimately ILV generation by vesicle fission.
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Affiliation(s)
- Manuel Alonso Y Adell
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Simona M Migliano
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Srigokul Upadhyayula
- Department of Pediatrics, Harvard Medical School, Boston, United States.,Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Yury S Bykov
- Structural and Computational Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Simon Sprenger
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Mehrshad Pakdel
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.,Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Georg F Vogel
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.,Division of Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria
| | - Gloria Jih
- Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Wesley Skillern
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, United States
| | - Reza Behrouzi
- Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Markus Babst
- Department of Biology, University of Utah, Utah, United States.,Center for Cell and Genome Science, University of Utah, Utah, United States
| | - Oliver Schmidt
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Michael W Hess
- Division of Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria
| | - John Ag Briggs
- Structural and Computational Unit, European Molecular Biology Laboratory, Heidelberg, Germany.,Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Tomas Kirchhausen
- Department of Pediatrics, Harvard Medical School, Boston, United States.,Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - David Teis
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.,Austrian Drug Screening Institute, Innsbruck, Austria
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10
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Imhof S, Fragoso C, Hemphill A, von Schubert C, Li D, Legant W, Betzig E, Roditi I. Flagellar membrane fusion and protein exchange in trypanosomes; a new form of cell-cell communication? F1000Res 2016; 5:682. [PMID: 27239276 PMCID: PMC4870996 DOI: 10.12688/f1000research.8249.1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/01/2016] [Indexed: 11/20/2022] Open
Abstract
Diverse structures facilitate direct exchange of proteins between cells, including plasmadesmata in plants and tunnelling nanotubes in bacteria and higher eukaryotes. Here we describe a new mechanism of protein transfer, flagellar membrane fusion, in the unicellular parasite
Trypanosoma brucei. When fluorescently tagged trypanosomes were co-cultured, a small proportion of double-positive cells were observed. The formation of double-positive cells was dependent on the presence of extracellular calcium and was enhanced by placing cells in medium supplemented with fresh bovine serum. Time-lapse microscopy revealed that double-positive cells arose by bidirectional protein exchange in the absence of nuclear transfer. Furthermore, super-resolution microscopy showed that this process occurred in ≤1 minute, the limit of temporal resolution in these experiments. Both cytoplasmic and membrane proteins could be transferred provided they gained access to the flagellum. Intriguingly, a component of the RNAi machinery (Argonaute) was able to move between cells, raising the possibility that small interfering RNAs are transported as cargo. Transmission electron microscopy showed that shared flagella contained two axonemes and two paraflagellar rods bounded by a single membrane. In some cases flagellar fusion was partial and interactions between cells were transient. In other cases fusion occurred along the entire length of the flagellum, was stable for several hours and might be irreversible. Fusion did not appear to be deleterious for cell function: paired cells were motile and could give rise to progeny while fused. The motile flagella of unicellular organisms are related to the sensory cilia of higher eukaryotes, raising the possibility that protein transfer between cells via cilia or flagella occurs more widely in nature.
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Affiliation(s)
- Simon Imhof
- Institute of Cell Biology, University of Bern, Bern, Switzerland; Graduate School of Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Cristina Fragoso
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Andrew Hemphill
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Conrad von Schubert
- Division of Molecular Pathobiology, DCR-VPH, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Dong Li
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Wesley Legant
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Eric Betzig
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Isabel Roditi
- Institute of Cell Biology, University of Bern, Bern, Switzerland
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