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Pombo-García K, Adame-Arana O, Martin-Lemaitre C, Jülicher F, Honigmann A. Membrane prewetting by condensates promotes tight-junction belt formation. Nature 2024; 632:647-655. [PMID: 39112699 PMCID: PMC11324514 DOI: 10.1038/s41586-024-07726-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 06/17/2024] [Indexed: 08/16/2024]
Abstract
Biomolecular condensates enable cell compartmentalization by acting as membraneless organelles1. How cells control the interactions of condensates with other cellular structures such as membranes to drive morphological transitions remains poorly understood. We discovered that formation of a tight-junction belt, which is essential for sealing epithelial tissues, is driven by a wetting phenomenon that promotes the growth of a condensed ZO-1 layer2 around the apical membrane interface. Using temporal proximity proteomics in combination with imaging and thermodynamic theory, we found that the polarity protein PATJ mediates a transition of ZO-1 into a condensed surface layer that elongates around the apical interface. In line with the experimental observations, our theory of condensate growth shows that the speed of elongation depends on the binding affinity of ZO-1 to the apical interface and is constant. Here, using PATJ mutations, we show that ZO-1 interface binding is necessary and sufficient for tight-junction belt formation. Our results demonstrate how cells exploit the collective biophysical properties of protein condensates at membrane interfaces to shape mesoscale structures.
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Affiliation(s)
- Karina Pombo-García
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
- Rosalind Franklin Institute, Oxford, United Kingdom.
| | - Omar Adame-Arana
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | | | - Frank Jülicher
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
- Center for Systems Biology Dresden, Dresden, Germany
- Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany
| | - Alf Honigmann
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
- Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany.
- Technische Universität Dresden, Biotechnologisches Zentrum, Center for Molecular and Cellular Bioengineering, Dresden, Germany.
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2
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Landajuela A, Braun M, Rodrigues CDA, Karatekin E. Detection of membrane fission in single Bacillus subtilis cells during endospore formation with high temporal resolution. STAR Protoc 2024; 5:102965. [PMID: 38502684 PMCID: PMC10963649 DOI: 10.1016/j.xpro.2024.102965] [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: 02/23/2023] [Revised: 07/17/2023] [Accepted: 03/01/2024] [Indexed: 03/21/2024] Open
Abstract
Membrane fission is an essential process in all domains of life. The underlying mechanisms remain poorly understood in bacteria, partly because suitable assays are lacking. Here, we describe an assay to detect membrane fission during endospore formation in single Bacillus subtilis cells with a temporal resolution of ∼1 min. Other cellular processes can be quantified and temporally aligned to the membrane fission event in individual cells, revealing correlations and causal relationships. For complete details on the use and execution of this protocol, please refer to Landajuela et al.1.
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Affiliation(s)
- Ane Landajuela
- Cellular and Molecular Physiology, Yale University, New Haven, CT, USA; Nanobiology Institute, Yale University, West Haven, CT, USA.
| | - Martha Braun
- Nanobiology Institute, Yale University, West Haven, CT, USA; Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | | | - Erdem Karatekin
- Cellular and Molecular Physiology, Yale University, New Haven, CT, USA; Nanobiology Institute, Yale University, West Haven, CT, USA; Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA; Université de Paris, Saints-Pères Paris Institute for the Neurosciences (SPPIN), Centre National de la Recherche Scientifique (CNRS), 75006 Paris, France.
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3
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Niedzialkowska E, Runyan LA, Kudryashova E, Egelman EH, Kudryashov DS. Stabilization of F-actin by Salmonella effector SipA resembles the structural effects of inorganic phosphate and phalloidin. Structure 2024; 32:725-738.e8. [PMID: 38518780 PMCID: PMC11162321 DOI: 10.1016/j.str.2024.02.022] [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: 01/02/2024] [Revised: 02/08/2024] [Accepted: 02/26/2024] [Indexed: 03/24/2024]
Abstract
Entry of Salmonella into host enterocytes relies on its pathogenicity island 1 effector SipA. We found that SipA binds to F-actin in a 1:2 stoichiometry with sub-nanomolar affinity. A cryo-EM reconstruction revealed that SipA's globular core binds at the groove between actin strands, whereas the extended C-terminal arm penetrates deeply into the inter-strand space, stabilizing F-actin from within. The unusually strong binding of SipA is achieved by a combination of fast association via the core and very slow dissociation dictated by the arm. Similar to Pi, BeF3, and phalloidin, SipA potently inhibited actin depolymerization by actin depolymerizing factor (ADF)/cofilin, which correlated with increased filament stiffness, supporting the hypothesis that F-actin's mechanical properties contribute to the recognition of its nucleotide state by protein partners. The remarkably strong binding to F-actin maximizes the toxin's effects at the injection site while minimizing global influence on the cytoskeleton and preventing pathogen detection by the host cell.
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Affiliation(s)
- Ewa Niedzialkowska
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22903, USA
| | - Lucas A Runyan
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Elena Kudryashova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22903, USA.
| | - Dmitri S Kudryashov
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA.
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4
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Zhou M, Riva A, Gauthier MPL, Kladde MP, Ferl RJ, Paul AL. Single-molecule long-read methylation profiling reveals regional DNA methylation regulated by Elongator Complex Subunit 2 in Arabidopsis roots experiencing spaceflight. Biol Direct 2024; 19:33. [PMID: 38689301 PMCID: PMC11059628 DOI: 10.1186/s13062-024-00476-z] [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: 02/20/2024] [Accepted: 04/10/2024] [Indexed: 05/02/2024] Open
Abstract
BACKGROUND The Advanced Plant Experiment-04 - Epigenetic Expression (APEX-04-EpEx) experiment onboard the International Space Station examined the spaceflight-altered cytosine methylation in two genetic lines of Arabidopsis thaliana, wild-type Col-0 and the mutant elp2-5, which is deficient in an epigenetic regulator Elongator Complex Subunit 2 (ELP2). Whole-genome bisulfite sequencing (WGBS) revealed distinct spaceflight associated methylation differences, presenting the need to explore specific space-altered methylation at single-molecule resolution to associate specific changes over large regions of spaceflight related genes. To date, tools of multiplexed targeted DNA methylation sequencing remain limited for plant genomes. RESULTS To provide methylation data at single-molecule resolution, Flap-enabled next-generation capture (FENGC), a novel targeted multiplexed DNA capture and enrichment technique allowing cleavage at any specified sites, was applied to survey spaceflight-altered DNA methylation in genic regions of interest. The FENGC capture panel contained 108 targets ranging from 509 to 704 nt within the promoter or gene body regions of gene targets derived from spaceflight whole-genome data sets. In addition to genes with significant changes in expression and average methylation levels between spaceflight and ground control, targets with space-altered distributions of the proportion of methylated cytosines per molecule were identified. Moreover, trends of co-methylation of different cytosine contexts were exhibited in the same DNA molecules. We further identified significant DNA methylation changes in three previously biological process-unknown genes, and loss-of-function mutants of two of these genes (named as EMO1 and EMO2 for ELP2-regulated Methylation in Orbit 1 and 2) showed enhanced root growth rate. CONCLUSIONS FENGC simplifies and reduces the cost of multiplexed, targeted, single-molecule profiling of methylation in plants, providing additional resolution along each DNA molecule that is not seen in population-based short-read data such as WGBS. This case study has revealed spaceflight-altered regional modification of cytosine methylation occurring within single DNA molecules of cell subpopulations, which were not identified by WGBS. The single-molecule survey by FENGC can lead to identification of novel functional genes. The newly identified EMO1 and EMO2 are root growth regulators which may be epigenetically involved in plant adaptation to spaceflight.
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Affiliation(s)
- Mingqi Zhou
- Department of Horticultural Sciences, University of Florida, 2550 Hull Road, Fifield Hall, 32611, Gainesville, FL, USA
| | - Alberto Riva
- Interdisciplinary Center for Biotechnology Research, University of Florida, 2033 Mowry Road, 32610, Gainesville, FL, USA
| | - Marie-Pierre L Gauthier
- Department of Biochemistry and Molecular Biology, University of Florida, 2033 Mowry Rd, 32610, Gainesville, FL, USA
| | - Michael P Kladde
- Department of Biochemistry and Molecular Biology, University of Florida, 2033 Mowry Rd, 32610, Gainesville, FL, USA
| | - Robert J Ferl
- Department of Horticultural Sciences, University of Florida, 2550 Hull Road, Fifield Hall, 32611, Gainesville, FL, USA.
- UF Research, University of Florida, 1523 Union Rd, Grinter Hall, 32611, Gainesville, FL, USA.
| | - Anna-Lisa Paul
- Department of Horticultural Sciences, University of Florida, 2550 Hull Road, Fifield Hall, 32611, Gainesville, FL, USA.
- Interdisciplinary Center for Biotechnology Research, University of Florida, 2033 Mowry Road, 32610, Gainesville, FL, USA.
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5
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Sherer LA, Mahanta B, Courtemanche N. Computational tools for quantifying actin filament numbers, lengths, and bundling. Biol Open 2024; 13:bio060267. [PMID: 38372564 PMCID: PMC10924227 DOI: 10.1242/bio.060267] [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: 12/01/2023] [Accepted: 02/08/2024] [Indexed: 02/20/2024] Open
Abstract
The actin cytoskeleton is a dynamic filamentous network that assembles into specialized structures to enable cells to perform essential processes. Direct visualization of fluorescently-labeled cytoskeletal proteins has provided numerous insights into the dynamic processes that govern the assembly of actin-based structures. However, accurate analysis of these experiments is often complicated by the interdependent and kinetic natures of the reactions involved. It is often challenging to disentangle these processes to accurately track their evolution over time. Here, we describe two programs written in the MATLAB programming language that facilitate counting, length measurements, and quantification of bundling of actin filaments visualized in fluorescence micrographs. To demonstrate the usefulness of our programs, we describe their application to the analysis of two representative reactions: (1) a solution of pre-assembled filaments under equilibrium conditions, and (2) a reaction in which actin filaments are crosslinked together over time. We anticipate that these programs can be applied to extract equilibrium and kinetic information from a broad range of actin-based reactions, and that their usefulness can be expanded further to investigate the assembly of other biopolymers.
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Affiliation(s)
- Laura A. Sherer
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Biswaprakash Mahanta
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Naomi Courtemanche
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
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6
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Bremer KV, Wu C, Patel AA, He KL, Grunfeld AM, Chanfreau GF, Quinlan ME. Formin tails act as a switch, inhibiting or enhancing processive actin elongation. J Biol Chem 2024; 300:105557. [PMID: 38097186 PMCID: PMC10797183 DOI: 10.1016/j.jbc.2023.105557] [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: 09/01/2023] [Revised: 11/30/2023] [Accepted: 12/07/2023] [Indexed: 01/04/2024] Open
Abstract
Formins are large, multidomain proteins that nucleate new actin filaments and accelerate elongation through a processive interaction with the barbed ends of filaments. Their actin assembly activity is generally attributed to their eponymous formin homology (FH) 1 and 2 domains; however, evidence is mounting that regions outside of the FH1FH2 stretch also tune actin assembly. Here, we explore the underlying contributions of the tail domain, which spans the sequence between the FH2 domain and the C terminus of formins. Tails vary in length from ∼0 to >200 residues and contain a number of recognizable motifs. The most common and well-studied motif is the ∼15-residue-long diaphanous autoregulatory domain. This domain mediates all or nothing regulation of actin assembly through an intramolecular interaction with the diaphanous inhibitory domain in the N-terminal half of the protein. Multiple reports demonstrate that the tail can enhance both nucleation and processivity. In this study, we provide a high-resolution view of the alternative splicing encompassing the tail in the formin homology domain (Fhod) family of formins during development. While four distinct tails are predicted, we found significant levels of only two of these. We characterized the biochemical effects of the different tails. Surprisingly, the two highly expressed Fhod-tails inhibit processive elongation and diminish nucleation, while a third supports activity. These findings demonstrate a new mechanism of modulating actin assembly by formins and support a model in which splice variants are specialized to build distinct actin structures during development.
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Affiliation(s)
- Kathryn V Bremer
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Carolyn Wu
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Aanand A Patel
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Kevin L He
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Alex M Grunfeld
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA
| | - Guillaume F Chanfreau
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA; Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, USA
| | - Margot E Quinlan
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, USA; Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, USA.
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7
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Niedzialkowska E, Runyan LA, Kudryashova E, Egelman EH, Kudryashov DS. Stabilization of F-actin by Salmonella effector SipA resembles the structural effects of inorganic phosphate and phalloidin. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.26.573373. [PMID: 38234808 PMCID: PMC10793455 DOI: 10.1101/2023.12.26.573373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Entry of Salmonella into host enterocytes strictly relies on its pathogenicity island 1 effector SipA. We found that SipA binds to F-actin in a unique mode in a 1:2 stoichiometry with picomolar affinity. A cryo-EM reconstruction revealed that SipA's globular core binds at the grove between actin strands, whereas the extended C-terminal arm penetrates deeply into the inter-strand space, stabilizing F-actin from within. The unusually strong binding of SipA is achieved via a combination of fast association via the core and very slow dissociation dictated by the arm. Similarly to Pi, BeF3, and phalloidin, SipA potently inhibited actin depolymerization by ADF/cofilin, which correlated with the increased filament stiffness, supporting the hypothesis that F-actin's mechanical properties contribute to the recognition of its nucleotide state by protein partners. The remarkably strong binding to F-actin maximizes the toxin's effects at the injection site while minimizing global influence on the cytoskeleton and preventing pathogen detection by the host cell.
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Affiliation(s)
- Ewa Niedzialkowska
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22903, USA
| | - Lucas A. Runyan
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Elena Kudryashova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Edward H. Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22903, USA
| | - Dmitri S. Kudryashov
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
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8
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Sazzed S, Scheible P, He J, Wriggers W. Untangling Irregular Actin Cytoskeleton Architectures in Tomograms of the Cell with Struwwel Tracer. Int J Mol Sci 2023; 24:17183. [PMID: 38139012 PMCID: PMC10743648 DOI: 10.3390/ijms242417183] [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: 10/09/2023] [Revised: 11/09/2023] [Accepted: 11/15/2023] [Indexed: 12/24/2023] Open
Abstract
In this work, we established, validated, and optimized a novel computational framework for tracing arbitrarily oriented actin filaments in cryo-electron tomography maps. Our approach was designed for highly complex intracellular architectures in which a long-range cytoskeleton network extends throughout the cell bodies and protrusions. The irregular organization of the actin network, as well as cryo-electron-tomography-specific noise, missing wedge artifacts, and map dimensions call for a specialized implementation that is both robust and efficient. Our proposed solution, Struwwel Tracer, accumulates densities along paths of a specific length in various directions, starting from locally determined seed points. The highest-density paths originating from the seed points form short linear candidate filament segments, which are further scrutinized and classified by users via inspection of a novel pruning map, which visualizes the likelihood of being a part of longer filaments. The pruned linear candidate filament segments are then iteratively fused into continuous, longer, and curved filaments based on their relative orientations, gap spacings, and extendibility. When applied to the simulated phantom tomograms of a Dictyostelium discoideum filopodium under experimental conditions, Struwwel Tracer demonstrated high efficacy, with F1-scores ranging from 0.85 to 0.90, depending on the noise level. Furthermore, when applied to a previously untraced experimental tomogram of mouse fibroblast lamellipodia, the filaments predicted by Struwwel Tracer exhibited a good visual agreement with the experimental map. The Struwwel Tracer framework is highly time efficient and can complete the tracing process in just a few minutes. The source code is publicly available with version 3.2 of the free and open-source Situs software package.
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Affiliation(s)
- Salim Sazzed
- Department of Computer Science, Old Dominion University, Norfolk, VA 23529, USA; (S.S.)
| | - Peter Scheible
- Department of Computer Science, Old Dominion University, Norfolk, VA 23529, USA; (S.S.)
| | - Jing He
- Department of Computer Science, Old Dominion University, Norfolk, VA 23529, USA; (S.S.)
| | - Willy Wriggers
- Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, VA 23529, USA
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9
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Li X, Hu X, Chen X, Fan J, Zhao Z, Wu J, Wang H, Dai Q. Spatial redundancy transformer for self-supervised fluorescence image denoising. NATURE COMPUTATIONAL SCIENCE 2023; 3:1067-1080. [PMID: 38177722 PMCID: PMC10766531 DOI: 10.1038/s43588-023-00568-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 11/07/2023] [Indexed: 01/06/2024]
Abstract
Fluorescence imaging with high signal-to-noise ratios has become the foundation of accurate visualization and analysis of biological phenomena. However, the inevitable noise poses a formidable challenge to imaging sensitivity. Here we provide the spatial redundancy denoising transformer (SRDTrans) to remove noise from fluorescence images in a self-supervised manner. First, a sampling strategy based on spatial redundancy is proposed to extract adjacent orthogonal training pairs, which eliminates the dependence on high imaging speed. Second, we designed a lightweight spatiotemporal transformer architecture to capture long-range dependencies and high-resolution features at low computational cost. SRDTrans can restore high-frequency information without producing oversmoothed structures and distorted fluorescence traces. Finally, we demonstrate the state-of-the-art denoising performance of SRDTrans on single-molecule localization microscopy and two-photon volumetric calcium imaging. SRDTrans does not contain any assumptions about the imaging process and the sample, thus can be easily extended to various imaging modalities and biological applications.
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Affiliation(s)
- Xinyang Li
- Department of Automation, Tsinghua University, Beijing, China
- Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China
- Institute for Brain and Cognitive Sciences, Tsinghua University, Beijing, China
| | - Xiaowan Hu
- Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China
| | - Xingye Chen
- Department of Automation, Tsinghua University, Beijing, China
- Institute for Brain and Cognitive Sciences, Tsinghua University, Beijing, China
- Research Institute for Frontier Science, Beihang University, Beijing, China
| | - Jiaqi Fan
- Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China
- Department of Electronic Engineering, Tsinghua University, Beijing, China
| | - Zhifeng Zhao
- Department of Automation, Tsinghua University, Beijing, China
- Institute for Brain and Cognitive Sciences, Tsinghua University, Beijing, China
| | - Jiamin Wu
- Department of Automation, Tsinghua University, Beijing, China.
- Institute for Brain and Cognitive Sciences, Tsinghua University, Beijing, China.
- Beijing Key Laboratory of Multi-dimension and Multi-scale Computational Photography (MMCP), Tsinghua University, Beijing, China.
- IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China.
| | - Haoqian Wang
- Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.
- The Shenzhen Institute of Future Media Technology, Shenzhen, China.
| | - Qionghai Dai
- Department of Automation, Tsinghua University, Beijing, China.
- Institute for Brain and Cognitive Sciences, Tsinghua University, Beijing, China.
- Beijing Key Laboratory of Multi-dimension and Multi-scale Computational Photography (MMCP), Tsinghua University, Beijing, China.
- IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China.
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10
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Oosterheert W, Blanc FEC, Roy A, Belyy A, Sanders MB, Hofnagel O, Hummer G, Bieling P, Raunser S. Molecular mechanisms of inorganic-phosphate release from the core and barbed end of actin filaments. Nat Struct Mol Biol 2023; 30:1774-1785. [PMID: 37749275 PMCID: PMC10643162 DOI: 10.1038/s41594-023-01101-9] [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: 04/07/2023] [Accepted: 08/18/2023] [Indexed: 09/27/2023]
Abstract
The release of inorganic phosphate (Pi) from actin filaments constitutes a key step in their regulated turnover, which is fundamental to many cellular functions. The mechanisms underlying Pi release from the core and barbed end of actin filaments remain unclear. Here, using human and bovine actin isoforms, we combine cryo-EM with molecular-dynamics simulations and in vitro reconstitution to demonstrate how actin releases Pi through a 'molecular backdoor'. While constantly open at the barbed end, the backdoor is predominantly closed in filament-core subunits and opens only transiently through concerted amino acid rearrangements. This explains why Pi escapes rapidly from the filament end but slowly from internal subunits. In a nemaline-myopathy-associated actin variant, the backdoor is predominantly open in filament-core subunits, resulting in accelerated Pi release and filaments with drastically shortened ADP-Pi caps. Our results provide the molecular basis for Pi release from actin and exemplify how a disease-linked mutation distorts the nucleotide-state distribution and atomic structure of the filament.
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Affiliation(s)
- Wout Oosterheert
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Florian E C Blanc
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Ankit Roy
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Alexander Belyy
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Micaela Boiero Sanders
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Oliver Hofnagel
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
- Institute for Biophysics, Goethe University, Frankfurt am Main, Germany.
| | - Peter Bieling
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
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11
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Hembrow J, Deeks MJ, Richards DM. Automatic extraction of actin networks in plants. PLoS Comput Biol 2023; 19:e1011407. [PMID: 37647341 PMCID: PMC10497154 DOI: 10.1371/journal.pcbi.1011407] [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: 12/18/2022] [Revised: 09/12/2023] [Accepted: 08/01/2023] [Indexed: 09/01/2023] Open
Abstract
The actin cytoskeleton is essential in eukaryotes, not least in the plant kingdom where it plays key roles in cell expansion, cell division, environmental responses and pathogen defence. Yet, the precise structure-function relationships of properties of the actin network in plants are still to be unravelled, including details of how the network configuration depends upon cell type, tissue type and developmental stage. Part of the problem lies in the difficulty of extracting high-quality, quantitative measures of actin network features from microscopy data. To address this problem, we have developed DRAGoN, a novel image analysis algorithm that can automatically extract the actin network across a range of cell types, providing seventeen different quantitative measures that describe the network at a local level. Using this algorithm, we then studied a number of cases in Arabidopsis thaliana, including several different tissues, a variety of actin-affected mutants, and cells responding to powdery mildew. In many cases we found statistically-significant differences in actin network properties. In addition to these results, our algorithm is designed to be easily adaptable to other tissues, mutants and plants, and so will be a valuable asset for the study and future biological engineering of the actin cytoskeleton in globally-important crops.
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Affiliation(s)
- Jordan Hembrow
- Living Systems Institute and Department of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| | - Michael J. Deeks
- Department of Biosciences, University of Exeter, Exeter, United Kingdom
| | - David M. Richards
- Living Systems Institute and Department of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
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12
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Fu G, Yan S, Khoo CJ, Chao VC, Liu Z, Mukhi M, Hervas R, Li XD, Ti SC. Integrated regulation of tubulin tyrosination and microtubule stability by human α-tubulin isotypes. Cell Rep 2023; 42:112653. [PMID: 37379209 DOI: 10.1016/j.celrep.2023.112653] [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: 07/28/2022] [Revised: 05/03/2023] [Accepted: 05/31/2023] [Indexed: 06/30/2023] Open
Abstract
Tubulin isotypes are critical for the functions of cellular microtubules, which exhibit different stability and harbor various post-translational modifications. However, how tubulin isotypes determine the activities of regulators for microtubule stability and modifications remains unknown. Here, we show that human α4A-tubulin, a conserved genetically detyrosinated α-tubulin isotype, is a poor substrate for enzymatic tyrosination. To examine the stability of microtubules reconstituted with defined tubulin compositions, we develop a strategy to site-specifically label recombinant human tubulin for single-molecule TIRF microscopy-based in vitro assays. The incorporation of α4A-tubulin into the microtubule lattice stabilizes the polymers from passive and MCAK-stimulated depolymerization. Further characterization reveals that the compositions of α-tubulin isotypes and tyrosination/detyrosination states allow graded control for the microtubule binding and the depolymerization activities of MCAK. Together, our results uncover the tubulin isotype-dependent enzyme activity for an integrated regulation of α-tubulin tyrosination/detyrosination states and microtubule stability, two well-correlated features of cellular microtubules.
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Affiliation(s)
- Guoling Fu
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China
| | - Shan Yan
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China
| | - Chen Jing Khoo
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China
| | - Victor C Chao
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China
| | - Zheng Liu
- Department of Chemistry, The University of Hong Kong, Hong Kong SAR, China
| | - Mayur Mukhi
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China
| | - Rubén Hervas
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China
| | - Xiang David Li
- Department of Chemistry, The University of Hong Kong, Hong Kong SAR, China
| | - Shih-Chieh Ti
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China.
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13
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Lakha R, Hachicho C, Mehlenbacher MR, Wilcox DE, Austin RN, Vizcarra CL. Metallothionein-3 attenuates the effect of Cu 2+ ions on actin filaments. J Inorg Biochem 2023; 242:112157. [PMID: 36801620 DOI: 10.1016/j.jinorgbio.2023.112157] [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: 12/19/2022] [Revised: 02/01/2023] [Accepted: 02/02/2023] [Indexed: 02/10/2023]
Abstract
Metallothionein 3 (MT-3) is a cysteine-rich metal-binding protein that is expressed in the mammalian central nervous system and kidney. Various reports have posited a role for MT-3 in regulating the actin cytoskeleton by promoting the assembly of actin filaments. We generated purified, recombinant mouse MT-3 of known metal compositions, either with zinc (Zn), lead (Pb), or copper/zinc (Cu/Zn) bound. None of these forms of MT-3 accelerated actin filament polymerization in vitro, either with or without the actin binding protein profilin. Furthermore, using a co-sedimentation assay, we did not observe Zn-bound MT-3 in complex with actin filaments. Cu2+ ions on their own induced rapid actin polymerization, an effect that we attribute to filament fragmentation. This effect of Cu2+ is reversed by adding either EGTA or Zn-bound MT-3, indicating that either molecule can chelate Cu2+ from actin. Altogether, our data indicate that purified recombinant MT-3 does not directly bind actin but it does attenuate the Cu-induced fragmentation of actin filaments.
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Affiliation(s)
- Rabina Lakha
- Department of Chemistry, Barnard College, New York, NY 10027, USA
| | - Carla Hachicho
- Department of Chemistry, Barnard College, New York, NY 10027, USA
| | | | - Dean E Wilcox
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA
| | - Rachel N Austin
- Department of Chemistry, Barnard College, New York, NY 10027, USA
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14
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Nelson S, Beck-Previs S, Sadayappan S, Tong C, Warshaw DM. Myosin-binding protein C stabilizes, but is not the sole determinant of SRX myosin in cardiac muscle. J Gen Physiol 2023; 155:e202213276. [PMID: 36688870 PMCID: PMC9884578 DOI: 10.1085/jgp.202213276] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 12/08/2022] [Accepted: 01/03/2023] [Indexed: 01/24/2023] Open
Abstract
The myosin super-relaxed (SRX) state is central to striated muscle metabolic and functional regulation. In skeletal muscle, SRX myosin are predominantly colocalized with myosin-binding protein C (MyBP-C) in the sarcomere C-zone. To define how cardiac MyBP-C (cMyBP-C) and its specific domains contribute to stabilizing the SRX state in cardiac muscle, we took advantage of transgenic cMyBP-C null mice and those expressing cMyBP-C with a 271-residue N-terminal truncation. Utilizing super-resolution microscopy, we determined the lifetime and subsarcomeric location of individual fluorescent-ATP turnover events within isolated cardiac myofibrils. The proportion of SRX myosin demonstrated a gradient along the half-thick filament, highest in the P- and C-zones (72 ± 9% and 71 ± 6%, respectively) and lower in the D-zone (45 ± 10%), which lies farther from the sarcomere center and lacks cMyBP-C, suggesting a possible role for cMyBP-C in stabilizing the SRX. However, myofibrils from cMyBP-C null mice demonstrated an ∼40% SRX reduction, not only within the now cMyBP-C-free C-zone (49 ± 9% SRX), but also within the D-zone (22 ± 5% SRX). These data suggest that the influence of cMyBP-C on the SRX state is not limited to the C-zone but extends along the thick filament. Interestingly, myofibrils with N-terminal truncated cMyBP-C had an SRX content and spatial gradient similar to the cMyBP-C null, indicating that the N terminus of cMyBP-C is necessary for cMyBP-C's role in enhancing the SRX gradient along the entire thick filament. Given that SRX myosin exist as a gradient along the thick filament that is highest in the C-zone, even in the absence of cMyBP-C or its N-terminus, an inherent bias must exist in the structure of the thick filament to stabilize the SRX state.
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Affiliation(s)
- Shane Nelson
- Department of Molecular Physiology and Biophysics, Cardiovascular Research Institute, University of Vermont, Burlington, VT, USA
| | - Samantha Beck-Previs
- Department of Molecular Physiology and Biophysics, Cardiovascular Research Institute, University of Vermont, Burlington, VT, USA
| | - Sakthivel Sadayappan
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Carl Tong
- Department of Medical Physiology, Texas A&M University, Bryan, TX, USA
| | - David M. Warshaw
- Department of Molecular Physiology and Biophysics, Cardiovascular Research Institute, University of Vermont, Burlington, VT, USA
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15
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Wang Y, Zhao Y, He J, Sun C, Lu W, Zhang Y, Fang Y. Doubling growth of egg-box structure during Calcium-mediated molecular assembly of alginate. J Colloid Interface Sci 2023; 634:747-756. [PMID: 36563431 DOI: 10.1016/j.jcis.2022.12.096] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 11/30/2022] [Accepted: 12/18/2022] [Indexed: 12/24/2022]
Abstract
Ca2+-mediated molecular assembly of alginate underpins its wide range of applications in foods, pharmaceutics, biomedicines, tissue engineering and environmental treatments. The mode of growth of egg-box structure of alginate in the presence of Ca2+ is a long-standing fundamental problem to be concluded. In this work, we investigate the Ca-induced structural evolution of alginate in dilute solution using atomic force microscopy and dilute solution viscometry. It is demonstrated that the structural evolution follows the three critical steps of monocomplexation, dimerization and multimerization, upon binding with Ca2+. Interestingly, the alginate single chains grow into dimers and multimers via a doubling mode, i.e., successive emerging of dimer, tetramer, octamer, and hexadecamer. Compared with lower guluronate (G) alginate, higher G alginate exhibits a more pronounced multimerization process occurring at a lower ratio of Ca/G. A mechanistic model depicting the evolution of egg-box structure is proposed. The results would add new knowledge to the current egg-box model regarding the molecular assembly and gelation of an important biopolymer alginate, and provide fundamental basis for molecular engineering of alginate for more advanced applications.
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Affiliation(s)
- Yi Wang
- School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Yiguo Zhao
- School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Jun He
- School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Cuixia Sun
- School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Wei Lu
- School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Yin Zhang
- Key Laboratory of Meat Processing of Sichuan, Chengdu University, Chengdu 610106, China
| | - Yapeng Fang
- School of Agriculture and Biology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China.
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16
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Fernández Casafuz AB, De Rossi MC, Bruno L. Mitochondrial cellular organization and shape fluctuations are differentially modulated by cytoskeletal networks. Sci Rep 2023; 13:4065. [PMID: 36906690 PMCID: PMC10008531 DOI: 10.1038/s41598-023-31121-w] [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: 12/20/2022] [Accepted: 03/07/2023] [Indexed: 03/13/2023] Open
Abstract
The interactions between mitochondria and the cytoskeleton have been found to alter mitochondrial function; however, the mechanisms underlying this phenomenon are largely unknown. Here, we explored how the integrity of the cytoskeleton affects the cellular organization, morphology and mobility of mitochondria in Xenopus laevis melanocytes. Cells were imaged in control condition and after different treatments that selectively affect specific cytoskeletal networks (microtubules, F-actin and vimentin filaments). We observed that mitochondria cellular distribution and local orientation rely mostly on microtubules, positioning these filaments as the main scaffolding of mitochondrial organization. We also found that cytoskeletal networks mold mitochondria shapes in distinct ways: while microtubules favor more elongated organelles, vimentin and actin filaments increase mitochondrial bending, suggesting the presence of mechanical interactions between these filaments and mitochondria. Finally, we identified that microtubule and F-actin networks play opposite roles in mitochondria shape fluctuations and mobility, with microtubules transmitting their jittering to the organelles and F-actin restricting the organelles motion. All our results support that cytoskeleton filaments interact mechanically with mitochondria and transmit forces to these organelles molding their movements and shapes.
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Affiliation(s)
- Agustina Belén Fernández Casafuz
- CONICET-Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Instituto de Cálculo (IC), Buenos Aires, 1428, Argentina
| | - María Cecilia De Rossi
- CONICET-Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Biológica, Instituto de Química Biológica (IQUIBICEN), Buenos Aires, 1428, Argentina.
- Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina.
| | - Luciana Bruno
- CONICET-Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Instituto de Cálculo (IC), Buenos Aires, 1428, Argentina.
- Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina.
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17
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Østerlund I, Persson S, Nikoloski Z. Tracing and tracking filamentous structures across scales: A systematic review. Comput Struct Biotechnol J 2022; 21:452-462. [PMID: 36618983 PMCID: PMC9804014 DOI: 10.1016/j.csbj.2022.12.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 12/14/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022] Open
Abstract
Filamentous structures are ubiquitous in nature, are studied in diverse scientific fields, and span vastly different spatial scales. Filamentous structures in biological systems fulfill different functions and often form dynamic networks that respond to perturbations. Therefore, characterizing the properties of filamentous structures and the networks they form is important to gain better understanding of systems level functions and dynamics. Filamentous structures are captured by various imaging technologies, and analysis of the resulting imaging data addresses two problems: (i) identification (tracing) of filamentous structures in a single snapshot and (ii) characterizing the dynamics (i.e., tracking) of filamentous structures over time. Therefore, considerable research efforts have been made in developing automated methods for tracing and tracking of filamentous structures. Here, we provide a systematic review in which we present, categorize, and discuss the state-of-the-art methods for tracing and tracking of filamentous structures in sparse and dense networks. We highlight the mathematical approaches, assumptions, and constraints particular for each method, allowing us to pinpoint outstanding challenges and offer perspectives for future research aimed at gaining better understanding of filamentous structures in biological systems.
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Affiliation(s)
- Isabella Østerlund
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871 Frederiksberg, Denmark,,Bioinformatics, Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany
| | - Staffan Persson
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871 Frederiksberg, Denmark
| | - Zoran Nikoloski
- Bioinformatics, Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany,Systems Biology and Mathematical Modeling, Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany,Corresponding author at: Bioinformatics, Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany.
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18
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Nasirimarekani V, Subramani S, Herzog S, Vilfan A, Guido I. Active Bending of Disordered Microtubule Bundles by Kinesin Motors. ACS OMEGA 2022; 7:43820-43828. [PMID: 36506136 PMCID: PMC9730755 DOI: 10.1021/acsomega.2c04958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 11/02/2022] [Indexed: 06/17/2023]
Abstract
Active networks of biopolymers and motor proteins in vitro self-organize and exhibit dynamic structures on length scales much larger than the interacting individual components of which they consist. How the dynamics is related across the range of length scales is still an open question. Here, we experimentally characterize and quantify the dynamic behavior of isolated microtubule bundles that bend due to the activity of motor proteins. At the motor level, we track and describe the motion features of kinesin-1 clusters stepping within the bending bundles. We find that there is a separation of length scales by at least 1 order of magnitude. At a run length of <1 μm, kinesin-1 activity leads to a bundle curvature in the range of tens of micrometers. We propose that the distribution of microtubule polarity plays a crucial role in the bending dynamics that we observe at both the bundle and motor levels. Our results contribute to the understanding of fundamental principles of vital intracellular processes by disentangling the multiscale dynamics in out-of-equilibrium active networks composed of cytoskeletal elements.
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Affiliation(s)
- Vahid Nasirimarekani
- Max
Planck Institute for Dynamics and Self-Organization (MPIDS), Am Fassberg 17, 37077Göttingen, Germany
| | - Smrithika Subramani
- Max
Planck Institute for Dynamics and Self-Organization (MPIDS), Am Fassberg 17, 37077Göttingen, Germany
- Department
of Physics, University of Wisconsin-Milwaukee, 3135 N Maryland Avenue, Milwaukee, Wisconsin53211, United States
| | - Sebastian Herzog
- Max
Planck Institute for Dynamics and Self-Organization (MPIDS), Am Fassberg 17, 37077Göttingen, Germany
- Department
for Computational Neuroscience, Third Institute of Physics −
Biophysics, University of Göttingen, Friedrich-Hund-Platz 1, 37077Göttingen, Germany
| | - Andrej Vilfan
- Max
Planck Institute for Dynamics and Self-Organization (MPIDS), Am Fassberg 17, 37077Göttingen, Germany
- Jožef
Stefan Institute, Jamova
39, 1000Ljubljana, Slovenia
| | - Isabella Guido
- Max
Planck Institute for Dynamics and Self-Organization (MPIDS), Am Fassberg 17, 37077Göttingen, Germany
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19
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Dilliway C, Dyer O, Mandrou E, Mitchell D, Menon G, Sparks H, Kapitany V, Payne-Dwyer A. Working at the interface of physics and biology: An early career researcher perspective. iScience 2022; 25:105615. [DOI: 10.1016/j.isci.2022.105615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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20
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Landajuela A, Braun M, Martínez-Calvo A, Rodrigues CDA, Gomis Perez C, Doan T, Rudner DZ, Wingreen NS, Karatekin E. Membrane fission during bacterial spore development requires cellular inflation driven by DNA translocation. Curr Biol 2022; 32:4186-4200.e8. [PMID: 36041438 PMCID: PMC9730832 DOI: 10.1016/j.cub.2022.08.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 04/26/2022] [Accepted: 08/08/2022] [Indexed: 12/14/2022]
Abstract
Bacteria require membrane fission for both cell division and endospore formation. In Bacillus subtilis, sporulation initiates with an asymmetric division that generates a large mother cell and a smaller forespore that contains only a quarter of its genome. As the mother cell membranes engulf the forespore, a DNA translocase pumps the rest of the chromosome into the small forespore compartment, inflating it due to increased turgor. When the engulfing membrane undergoes fission, the forespore is released into the mother cell cytoplasm. The B. subtilis protein FisB catalyzes membrane fission during sporulation, but the molecular basis is unclear. Here, we show that forespore inflation and FisB accumulation are both required for an efficient membrane fission. Forespore inflation leads to higher membrane tension in the engulfment membrane than in the mother cell membrane, causing the membrane to flow through the neck connecting the two membrane compartments. Thus, the mother cell supplies some of the membrane required for the growth of the membranes surrounding the forespore. The oligomerization of FisB at the membrane neck slows the equilibration of membrane tension by impeding the membrane flow. This leads to a further increase in the tension of the engulfment membrane, promoting its fission through lysis. Collectively, our data indicate that DNA translocation has a previously unappreciated second function in energizing the FisB-mediated membrane fission under energy-limited conditions.
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Affiliation(s)
- Ane Landajuela
- Cellular and Molecular Physiology, Yale University, New Haven, CT, USA; Nanobiology Institute, Yale University, West Haven, CT, USA.
| | - Martha Braun
- Nanobiology Institute, Yale University, West Haven, CT, USA; Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.
| | - Alejandro Martínez-Calvo
- Princeton Center for Theoretical Science, Princeton University, Princeton, NJ 08544, USA; Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | | | - Carolina Gomis Perez
- Cellular and Molecular Physiology, Yale University, New Haven, CT, USA; Nanobiology Institute, Yale University, West Haven, CT, USA
| | - Thierry Doan
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Aix-Marseille Université-CNRS UMR7255, Marseilles, France
| | - David Z Rudner
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Ned S Wingreen
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Erdem Karatekin
- Cellular and Molecular Physiology, Yale University, New Haven, CT, USA; Nanobiology Institute, Yale University, West Haven, CT, USA; Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA; Université de Paris, Saints-Pères Paris Institute for the Neurosciences (SPPIN), Centre National de la Recherche Scientifique (CNRS), 75006 Paris, France.
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21
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Shree S, Sutradhar S, Trottier O, Tu Y, Liang X, Howard J. Dynamic instability of dendrite tips generates the highly branched morphologies of sensory neurons. SCIENCE ADVANCES 2022; 8:eabn0080. [PMID: 35767611 PMCID: PMC9242452 DOI: 10.1126/sciadv.abn0080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 05/12/2022] [Indexed: 06/15/2023]
Abstract
The highly ramified arbors of neuronal dendrites provide the substrate for the high connectivity and computational power of the brain. Altered dendritic morphology is associated with neuronal diseases. Many molecules have been shown to play crucial roles in shaping and maintaining dendrite morphology. However, the underlying principles by which molecular interactions generate branched morphologies are not understood. To elucidate these principles, we visualized the growth of dendrites throughout larval development of Drosophila sensory neurons and found that the tips of dendrites undergo dynamic instability, transitioning rapidly and stochastically between growing, shrinking, and paused states. By incorporating these measured dynamics into an agent-based computational model, we showed that the complex and highly variable dendritic morphologies of these cells are a consequence of the stochastic dynamics of their dendrite tips. These principles may generalize to branching of other neuronal cell types, as well as to branching at the subcellular and tissue levels.
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Affiliation(s)
- Sonal Shree
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Sabyasachi Sutradhar
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Olivier Trottier
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
- Department of Physics, Yale University, New Haven, CT 06511, USA
| | - Yuhai Tu
- IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, USA
| | - Xin Liang
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Jonathon Howard
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
- Department of Physics, Yale University, New Haven, CT 06511, USA
- Quantitative Biology Institute, Yale University, New Haven, CT 06511, USA
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22
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Abstract
Bacteria have evolved to develop multiple strategies for antibiotic resistance by effectively reducing intracellular antibiotic concentrations or antibiotic binding affinities, but the role of cell morphology in antibiotic resistance remains poorly understood. By analyzing cell morphological data for different bacterial species under antibiotic stress, we find that bacteria increase or decrease the cell surface-to-volume ratio depending on the antibiotic target. Using quantitative modeling, we show that by reducing the surface-to-volume ratio, bacteria can effectively reduce the intracellular antibiotic concentration by decreasing antibiotic influx. The model further predicts that bacteria can increase the surface-to-volume ratio to induce the dilution of membrane-targeting antibiotics, in agreement with experimental data. Using a whole-cell model for the regulation of cell shape and growth by antibiotics, we predict shape transformations that bacteria can utilize to increase their fitness in the presence of antibiotics. We conclude by discussing additional pathways for antibiotic resistance that may act in synergy with shape-induced resistance.
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Affiliation(s)
- Nikola Ojkic
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London, United Kingdom
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, United Kingdom
| | - Diana Serbanescu
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London, United Kingdom
| | - Shiladitya Banerjee
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
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23
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Measurement of the Persistence Length of Cytoskeletal Filaments using Curvature Distributions. Biophys J 2022; 121:1813-1822. [PMID: 35450824 DOI: 10.1016/j.bpj.2022.04.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 02/16/2022] [Accepted: 04/14/2022] [Indexed: 11/23/2022] Open
Abstract
Cytoskeletal filaments such as microtubules and actin filaments play important roles in the mechanical integrity of cells and the ability of cells to respond to their environment. Measuring the mechanical properties of cytoskeletal structures is crucial for gaining insight into intracellular mechanical stresses and their role in regulating cellular processes. One of the ways to characterize these mechanical properties is by measuring their persistence length, the average length over which filaments stay straight. There are several approaches in the literature for measuring filament deformations, such as Fourier analysis of images obtained using fluorescence microscopy. Here, we show how curvature distributions can be used as an alternative tool to quantify bio-filament deformations, and investigate how the apparent stiffness of filaments depends on the resolution and noise of the imaging system. We present analytical calculations of the scaling curvature distributions as a function of filament discretization, and test our predictions by comparing Monte Carlo simulations to results from existing techniques. We also apply our approach to microtubules and actin filaments obtained from in vitro gliding assay experiments with high densities of non-functional motors, and calculate the persistence length of these filaments. The presented curvature analysis is significantly more accurate compared to existing approaches for small data sets, and can be readily applied to both in vitro or in vivo filament data through the use of the open-source codes we provide.
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24
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Smith AJ, Bustamante-Marin XM, Yin W, Sears PR, Herring LE, Dicheva NN, López-Giráldez F, Mane S, Tarran R, Leigh MW, Knowles MR, Zariwala MA, Ostrowski LE. The role of SPAG1 in the assembly of axonemal dyneins in human airway epithelia. J Cell Sci 2022; 135:jcs259512. [PMID: 35178554 PMCID: PMC8995097 DOI: 10.1242/jcs.259512] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 02/14/2022] [Indexed: 11/20/2022] Open
Abstract
Mutations in SPAG1, a dynein axonemal assembly factor (DNAAF) that facilitates the assembly of dynein arms in the cytoplasm before their transport into the cilium, result in primary ciliary dyskinesia (PCD), a genetically heterogenous disorder characterized by chronic oto-sino-pulmonary disease, infertility and laterality defects. To further elucidate the role of SPAG1 in dynein assembly, we examined its expression, interactions and ciliary defects in control and PCD human airway epithelia. Immunoprecipitations showed that SPAG1 interacts with multiple DNAAFs, dynein chains and canonical components of the R2TP complex. Protein levels of dynein heavy chains (DHCs) and interactions between DHCs and dynein intermediate chains (DICs) were reduced in SPAG1 mutants. We also identified a previously uncharacterized 60 kDa SPAG1 isoform, through examination of PCD subjects with an atypical ultrastructural defect for SPAG1 variants, that can partially compensate for the absence of full-length SPAG1 to assemble a reduced number of outer dynein arms. In summary, our data show that SPAG1 is necessary for axonemal dynein arm assembly by scaffolding R2TP-like complexes composed of several DNAAFs that facilitate the folding and/or binding of the DHCs to the DIC complex.
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Affiliation(s)
- Amanda J. Smith
- Marsico Lung Institute/Cystic Fibrosis Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ximena M. Bustamante-Marin
- Marsico Lung Institute/Cystic Fibrosis Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Weining Yin
- Marsico Lung Institute/Cystic Fibrosis Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Patrick R. Sears
- Marsico Lung Institute/Cystic Fibrosis Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Laura E. Herring
- University of North Carolina Proteomics Core Facility, Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Nedyalka N. Dicheva
- University of North Carolina Proteomics Core Facility, Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | | | - Shrikant Mane
- Yale Center for Genome Analysis, Yale University, New Haven, CT 06520, USA
| | - Robert Tarran
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Margaret W. Leigh
- Marsico Lung Institute/Cystic Fibrosis Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Michael R. Knowles
- Marsico Lung Institute/Cystic Fibrosis Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Maimoona A. Zariwala
- Marsico Lung Institute/Cystic Fibrosis Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Lawrence E. Ostrowski
- Marsico Lung Institute/Cystic Fibrosis Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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25
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Constraint Release for Reptating Filaments in Semiflexible Networks Depends on Background Fluctuations. Polymers (Basel) 2022; 14:polym14040707. [PMID: 35215620 PMCID: PMC8879693 DOI: 10.3390/polym14040707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 02/06/2022] [Accepted: 02/07/2022] [Indexed: 11/17/2022] Open
Abstract
Entangled semiflexible polymer networks are usually described by the tube model, although this concept has not been able to explain all experimental observations. One of its major shortcomings is neglecting the thermal fluctuations of the polymers surrounding the examined test filament, such that disentanglement effects are not captured. In this study, we present experimental evidence that correlated constraint release which has been predicted theoretically occurs in entangled, but not in crosslinked semiflexible polymer networks. By tracking single semiflexible DNA nanotubes embedded both in entangled and crosslinked F-actin networks, we observed different reptation dynamics in both systems, emphasizing the need for a revision of the classical tube theory for entangled polymer solutions.
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26
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Abstract
The precise assembly and disassembly of actin filaments is required for several cellular processes, and their regulation has been scrutinized for decades. Twenty years ago, a handful of studies marked the advent of a new type of experiment to study actin dynamics: using optical microscopy to look at individual events, taking place on individual filaments in real time. Here, we summarize the main characteristics of this approach and how it has changed our ability to understand actin assembly dynamics. We also highlight some of its caveats and reflect on what we have learned over the past 20 years, leading us to propose a set of guidelines, which we hope will contribute to a better exploitation of this powerful tool.
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27
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Gomis Perez C, Dudzinski NR, Rouches M, Landajuela A, Machta B, Zenisek D, Karatekin E. Rapid propagation of membrane tension at retinal bipolar neuron presynaptic terminals. SCIENCE ADVANCES 2022; 8:eabl4411. [PMID: 34985955 DOI: 10.1126/sciadv.abl4411] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Many cellular activities, such as cell migration, cell division, phagocytosis, and exo-endocytosis, generate and are regulated by membrane tension gradients. Membrane tension gradients drive membrane flows, but there is controversy over how rapidly plasma membrane flow can relax tension gradients. Here, we show that membrane tension can propagate rapidly or slowly, spanning orders of magnitude in speed, depending on the cell type. In a neuronal terminal specialized for rapid synaptic vesicle turnover, membrane tension equilibrates within seconds. By contrast, membrane tension does not propagate in neuroendocrine adrenal chromaffin cells secreting catecholamines. Stimulation of exocytosis causes a rapid, global decrease in the synaptic terminal membrane tension, which recovers slowly due to endocytosis. Thus, membrane flow and tension equilibration may be adapted to distinct membrane recycling requirements.
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Affiliation(s)
- Carolina Gomis Perez
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
- Nanobiology Institute, Yale University, West Haven, CT, USA
| | - Natasha R Dudzinski
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
- Nanobiology Institute, Yale University, West Haven, CT, USA
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT, USA
| | - Mason Rouches
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
- Systems Biology Institute, Yale University, West Haven, CT, USA
| | - Ane Landajuela
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
- Nanobiology Institute, Yale University, West Haven, CT, USA
| | - Benjamin Machta
- Systems Biology Institute, Yale University, West Haven, CT, USA
- Department of Physics, Yale University, New Haven, CT, USA
| | - David Zenisek
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT, USA
- Kavli Institute for Neuroscience, Yale University, New Haven, CT, USA
- Department of Neuroscience, Yale University, New Haven, CT, USA
- Department of Ophthalmology and Visual Sciences, Yale University, New Haven, CT, USA
| | - Erdem Karatekin
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
- Nanobiology Institute, Yale University, West Haven, CT, USA
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT, USA
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
- Université de Paris, SPPIN-Saints-Pères Paris Institute for the Neurosciences, Centre National de la Recherche Scientifique (CNRS), Paris F-75006, France
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28
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Guido I. Spontaneously Beating Biomimetic Structures. Methods Mol Biol 2022; 2430:205-218. [PMID: 35476334 DOI: 10.1007/978-1-0716-1983-4_13] [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: 06/14/2023]
Abstract
The propulsion of motile cells such as sperms and the transport of fluids on cell surfaces rely on oscillatory bending of cellular appendages that can perform periodic oscillations. These structures are flagella and cilia. Their beating is driven by the interaction between microtubules and motor proteins and the mechanism regulating this is still a puzzle. One approach to address this issue is the assembling of synthetic minimal systems by using natural building blocks, e.g., microtubules and kinesin motors, which undergo persistent oscillation in the presence of ATP. An example of an autonomous molecular system is reported in this chapter. It dynamically self-organizes through its elasticity and the interaction with the environment represented by the active forces exerted by motor proteins. The resulting motion resembles the beating of sperm flagella. Assembling such minimal systems able to mimic the behavior of complex biological structures might help to unveil basic mechanisms underlying the beating of natural cilia and flagella.
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Affiliation(s)
- Isabella Guido
- Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany.
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29
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Fernández Casafuz AB, De Rossi MC, Bruno L. Morphological fluctuations of individual mitochondria in living cells. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:094005. [PMID: 34847540 DOI: 10.1088/1361-648x/ac3e9c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 11/30/2021] [Indexed: 06/13/2023]
Abstract
Uncovering the link between mitochondrial morphology, dynamics, positioning and function is challenging. Mitochondria are very flexible organelles that are subject to tension and compression within cells. Recent findings highlighted the importance of these mechanical aspects in the regulation of mitochondria dynamics, arising the question on which are the processes and mechanisms involved in their shape remodeling. In this work we explored in detail the morphological changes and spatio-temporal fluctuations of these organelles in livingXenopus laevismelanophores, a well-characterized cellular model. We developed an automatic method for the classification of mitochondria shapes based on the analysis of the curvature of the contour shape from confocal microscopy images. A persistence length of 2.1μm was measured, quantifying, for the first time, the bending plasticity of mitochondria in their cellular environment. The shape evolution at the single organelle level was followed during a few minutes revealing that mitochondria can bend and unbend in the seconds timescale. Furthermore, the inspection of confocal movies simultaneously registering fluorescent mitochondria and microtubules suggests that the cytoskeleton network architecture and dynamics play a significant role in mitochondria shape remodeling and fluctuations. For instance changes from sinuous to elongated organelles related to transitions from confined behavior to fast directed motion along microtubule tracks were observed.
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Affiliation(s)
- Agustina B Fernández Casafuz
- CONICET-Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Instituto de Cálculo, Buenos Aires, Argentina
| | - María Cecilia De Rossi
- CONICET-Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Biológica, Instituto de Química Biológica (IQUIBICEN), Buenos Aires, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina
| | - Luciana Bruno
- CONICET-Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Instituto de Cálculo, Buenos Aires, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina
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30
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Galotto G, Wisanpitayakorn P, Bibeau JP, Liu YC, Furt F, Pierce EC, Simpson PJ, Tüzel E, Vidali L. Myosin XI drives polarized growth by vesicle focusing and local enrichment of F-actin in Physcomitrium patens. PLANT PHYSIOLOGY 2021; 187:2509-2529. [PMID: 34890463 PMCID: PMC8932395 DOI: 10.1093/plphys/kiab435] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 08/13/2021] [Indexed: 05/22/2023]
Abstract
In tip-growing plant cells, growth results from myosin XI and F-actin-mediated deposition of cell wall polysaccharides contained in secretory vesicles. Previous evidence showed that myosin XI anticipates F-actin accumulation at the cell's tip, suggesting a mechanism where vesicle clustering via myosin XI increases F-actin polymerization. To evaluate this model, we used a conditional loss-of-function strategy by generating moss (Physcomitrium patens) plants harboring a myosin XI temperature-sensitive allele. We found that loss of myosin XI function alters tip cell morphology, vacuolar homeostasis, and cell viability but not following F-actin depolymerization. Importantly, our conditional loss-of-function analysis shows that myosin XI focuses and directs vesicles at the tip of the cell, which induces formin-dependent F-actin polymerization, increasing F-actin's local concentration. Our findings support the role of myosin XI in vesicle focusing, possibly via clustering and F-actin organization, necessary for tip growth, and deepen our understanding of additional myosin XI functions.
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Affiliation(s)
- Giulia Galotto
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
| | | | - Jeffrey P Bibeau
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
| | - Yen-Chun Liu
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
| | - Fabienne Furt
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
| | - Ellen C Pierce
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
| | - Parker J Simpson
- Bioinformatics and Computational Biology Program, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
| | - Erkan Tüzel
- Bioengineering Department, Temple University, Philadelphia, Pennsylvania 19122, USA
| | - Luis Vidali
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
- Bioinformatics and Computational Biology Program, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
- Author for communication:
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31
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Nishi K, MacKintosh FC, Schmidt CF. Multiscale Microrheology Using Fluctuating Filaments as Stealth Probes. PHYSICAL REVIEW LETTERS 2021; 127:158001. [PMID: 34678027 DOI: 10.1103/physrevlett.127.158001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 08/18/2021] [Accepted: 08/19/2021] [Indexed: 06/13/2023]
Abstract
The mechanical properties of soft materials can be probed on small length scales by microrheology. A common approach tracks fluctuations of micrometer-sized beads embedded in the medium to be characterized. This approach yields results that depend on probe size when the medium has structure on comparable length scales. Here, we introduce filament-based microrheology using high-aspect-ratio semiflexible filaments as probes. Such quasi-1D probes are much less invasive than beads due to their small cross sections. Moreover, by imaging transverse bending modes, we simultaneously determine the micromechanical response of the medium on multiple length scales corresponding to the mode wavelengths. We use semiflexible single-walled carbon nanotubes as probes that can be accurately and rapidly imaged based on their stable near-IR fluorescence. We find that the viscoelastic properties of sucrose, polyethylene oxide, and hyaluronic acid solutions measured in this way are in good agreement with those measured by conventional micro- and macrorheology.
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Affiliation(s)
- Kengo Nishi
- Third Institute of Physics-Biophysics, Faculty of Physics, University of Göttingen, 37077 Göttingen, Germany
- Department of Physics & Soft Matter Center, Duke University, Durham, North Carolina 27708, USA
- Department of Applied Physical Sciences, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Fred C MacKintosh
- Department of Chemical & Biomolecular Engineering, Rice University, Houston, Texas 77005, USA
- Center for Theoretical Biological Physics, Rice University, Houston, Texas 77030, USA
- Department of Chemistry, Rice University, Houston, Texas 77005, USA
- Department of Physics & Astronomy, Rice University, Houston, Texas 77005, USA
| | - Christoph F Schmidt
- Third Institute of Physics-Biophysics, Faculty of Physics, University of Göttingen, 37077 Göttingen, Germany
- Department of Physics & Soft Matter Center, Duke University, Durham, North Carolina 27708, USA
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32
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Ivec A, Trupinić M, Tolić IM, Pavin N. Oblique circle method for measuring the curvature and twist of mitotic spindle microtubule bundles. Biophys J 2021; 120:3641-3648. [PMID: 34339637 PMCID: PMC8456293 DOI: 10.1016/j.bpj.2021.07.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 07/03/2021] [Accepted: 07/27/2021] [Indexed: 11/20/2022] Open
Abstract
The highly ordered spatial organization of microtubule bundles in the mitotic spindle is crucial for its proper functioning. The recent discovery of twisted shapes of microtubule bundles and spindle chirality suggests that the bundles extend along curved paths in three dimensions, rather than being confined to a plane. This, in turn, implies that rotational forces, i.e., torques, exist in the spindle in addition to the widely studied linear forces. However, studies of spindle architecture and forces are impeded by a lack of a robust method for the geometric quantification of microtubule bundles in the spindle. In this work, we describe a simple method for measuring and evaluating the shapes of microtubule bundles by characterizing them in terms of their curvature and twist. By using confocal microscopy, we obtain three-dimensional images of spindles, which allows us to trace the entire microtubule bundle. For each traced bundle, we first fit a plane and then fit a circle lying in that plane. With this robust method, we extract the curvature and twist, which represent the geometric information characteristic for each bundle. As the bundle shapes reflect the forces within them, this method is valuable for the understanding of forces that act on chromosomes during mitosis.
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Affiliation(s)
- Arian Ivec
- Department of Physics, Faculty of Science, University of Zagreb, Zagreb, Croatia.
| | - Monika Trupinić
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Iva M Tolić
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Nenad Pavin
- Department of Physics, Faculty of Science, University of Zagreb, Zagreb, Croatia.
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33
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Weißenbruch K, Grewe J, Hippler M, Fladung M, Tremmel M, Stricker K, Schwarz US, Bastmeyer M. Distinct roles of nonmuscle myosin II isoforms for establishing tension and elasticity during cell morphodynamics. eLife 2021; 10:71888. [PMID: 34374341 PMCID: PMC8391736 DOI: 10.7554/elife.71888] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 08/09/2021] [Indexed: 12/29/2022] Open
Abstract
Nonmuscle myosin II (NM II) is an integral part of essential cellular processes, including adhesion and migration. Mammalian cells express up to three isoforms termed NM IIA, B, and C. We used U2OS cells to create CRISPR/Cas9-based knockouts of all three isoforms and analyzed the phenotypes on homogenously coated surfaces, in collagen gels, and on micropatterned substrates. In contrast to homogenously coated surfaces, a structured environment supports a cellular phenotype with invaginated actin arcs even in the absence of NM IIA-induced contractility. A quantitative shape analysis of cells on micropatterns combined with a scale-bridging mathematical model reveals that NM IIA is essential to build up cellular tension during initial stages of force generation, while NM IIB is necessary to elastically stabilize NM IIA-generated tension. A dynamic cell stretch/release experiment in a three-dimensional scaffold confirms these conclusions and in addition reveals a novel role for NM IIC, namely the ability to establish tensional homeostasis.
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Affiliation(s)
- Kai Weißenbruch
- Zoological Institute, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.,Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Justin Grewe
- Institute for Theoretical Physics, University of Heidelberg, Heidelberg, Germany.,BioQuant-Center for Quantitative Biology, University of Heidelberg, Heidelberg, Germany
| | - Marc Hippler
- Zoological Institute, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.,Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Magdalena Fladung
- Zoological Institute, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Moritz Tremmel
- Zoological Institute, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Kathrin Stricker
- Zoological Institute, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Ulrich Sebastian Schwarz
- Institute for Theoretical Physics, University of Heidelberg, Heidelberg, Germany.,BioQuant-Center for Quantitative Biology, University of Heidelberg, Heidelberg, Germany
| | - Martin Bastmeyer
- Zoological Institute, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.,Institute for Biological and Chemical Systems - Biological Information Processing (IBCS-BIP), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
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34
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Flormann DAD, Schu M, Terriac E, Thalla D, Kainka L, Koch M, Gad AKB, Lautenschläger F. A novel universal algorithm for filament network tracing and cytoskeleton analysis. FASEB J 2021; 35:e21582. [PMID: 33835502 DOI: 10.1096/fj.202100048r] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 03/06/2021] [Accepted: 03/25/2021] [Indexed: 01/01/2023]
Abstract
The rapid development of advanced microscopy techniques over recent decades has significantly increased the quality of imaging and our understanding of subcellular structures, such as the organization of the filaments of the cytoskeleton using fluorescence and electron microscopy. However, these recent improvements in imaging techniques have not been matched by similar development of techniques for computational analysis of the images of filament networks that can now be obtained. Hence, for a wide range of applications, reliable computational analysis of such two-dimensional methods remains challenging. Here, we present a new algorithm for tracing of filament networks. This software can extract many important parameters from grayscale images of filament networks, including the mesh hole size, and filament length and connectivity (also known as Coordination Number). In addition, the method allows sub-networks to be distinguished in two-dimensional images using intensity thresholding. We show that the algorithm can be used to analyze images of cytoskeleton networks obtained using different advanced microscopy methods. We have thus developed a new improved method for computational analysis of two-dimensional images of filamentous networks that has wide applications for existing imaging techniques. The algorithm is available as open-source software.
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Affiliation(s)
- Daniel A D Flormann
- Department of Physics, Saarland University, Saarbruecken, Germany.,INM - Leibniz Institute for New Materials, Saarbruecken, Germany
| | - Moritz Schu
- Department of Physics, Saarland University, Saarbruecken, Germany
| | - Emmanuel Terriac
- INM - Leibniz Institute for New Materials, Saarbruecken, Germany
| | - Divyendu Thalla
- Department of Physics, Saarland University, Saarbruecken, Germany.,INM - Leibniz Institute for New Materials, Saarbruecken, Germany
| | - Lucina Kainka
- Department of Physics, Saarland University, Saarbruecken, Germany.,INM - Leibniz Institute for New Materials, Saarbruecken, Germany
| | - Marcus Koch
- INM - Leibniz Institute for New Materials, Saarbruecken, Germany
| | - Annica K B Gad
- Department of Oncology and Metabolism, The Medical School, Weston Park Cancer Centre, Sheffield, UK.,Centro de Química da Madeira, Universidade da Madeira, Funchal, Portugal
| | - Franziska Lautenschläger
- Department of Physics, Saarland University, Saarbruecken, Germany.,INM - Leibniz Institute for New Materials, Saarbruecken, Germany
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35
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Chaigne A, Smith MB, Lopez Cavestany R, Hannezo E, Chalut KJ, Paluch EK. Three-dimensional geometry controls division symmetry in stem cell colonies. J Cell Sci 2021; 134:jcs255018. [PMID: 34323278 PMCID: PMC8349555 DOI: 10.1242/jcs.255018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 06/16/2021] [Indexed: 11/24/2022] Open
Abstract
Proper control of division orientation and symmetry, largely determined by spindle positioning, is essential to development and homeostasis. Spindle positioning has been extensively studied in cells dividing in two-dimensional (2D) environments and in epithelial tissues, where proteins such as NuMA (also known as NUMA1) orient division along the interphase long axis of the cell. However, little is known about how cells control spindle positioning in three-dimensional (3D) environments, such as early mammalian embryos and a variety of adult tissues. Here, we use mouse embryonic stem cells (ESCs), which grow in 3D colonies, as a model to investigate division in 3D. We observe that, at the periphery of 3D colonies, ESCs display high spindle mobility and divide asymmetrically. Our data suggest that enhanced spindle movements are due to unequal distribution of the cell-cell junction protein E-cadherin between future daughter cells. Interestingly, when cells progress towards differentiation, division becomes more symmetric, with more elongated shapes in metaphase and enhanced cortical NuMA recruitment in anaphase. Altogether, this study suggests that in 3D contexts, the geometry of the cell and its contacts with neighbors control division orientation and symmetry. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Agathe Chaigne
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Matthew B. Smith
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Rocio Lopez Cavestany
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | | | - Kevin J. Chalut
- Wellcome/MRC Stem Cell Institute, University of Cambridge, Cambridge CB2 0AW, UK
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Ewa K. Paluch
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
- Wellcome/MRC Stem Cell Institute, University of Cambridge, Cambridge CB2 0AW, UK
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
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36
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Händler T, Tutmarc C, Glaser M, Freitag JS, Smith DM, Schnauß J. Measuring structural parameters of crosslinked and entangled semiflexible polymer networks with single-filament tracing. Phys Rev E 2021; 103:062501. [PMID: 34271634 DOI: 10.1103/physreve.103.062501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 04/17/2021] [Indexed: 12/15/2022]
Abstract
Single-filament tracing has been a valuable tool to directly determine geometrical and mechanical properties of entangled polymer networks. However, systematically verifying how the stiffness of the tracer filament or its molecular interactions with the surrounding network impacts the measurement of these parameters has not been possible with the established experimental systems. Here we use mechanically programmable DNA nanotubes embedded in crosslinked and entangled F-actin networks, as well as in synthetic DNA networks, in order to measure fundamental, structural network properties like tube width and mesh size with respect to the stiffness of the tracers. While we confirm some predictions derived from models based purely on steric interactions, our results indicate that these models should be expanded to account for additional interfilament interactions, thereby describing the behavior of real polymer networks.
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Affiliation(s)
- Tina Händler
- Peter Debye Institute for Soft Matter Physics, University of Leipzig, Linnéstraße 5, 04103 Leipzig, Germany.,Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, 04103 Leipzig, Germany
| | - Cary Tutmarc
- Peter Debye Institute for Soft Matter Physics, University of Leipzig, Linnéstraße 5, 04103 Leipzig, Germany.,Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, 04103 Leipzig, Germany
| | - Martin Glaser
- Peter Debye Institute for Soft Matter Physics, University of Leipzig, Linnéstraße 5, 04103 Leipzig, Germany.,Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, 04103 Leipzig, Germany
| | - Jessica S Freitag
- Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, 04103 Leipzig, Germany
| | - David M Smith
- Peter Debye Institute for Soft Matter Physics, University of Leipzig, Linnéstraße 5, 04103 Leipzig, Germany.,Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, 04103 Leipzig, Germany.,Institute of Clinical Immunology, University of Leipzig Medical Faculty, 04103 Leipzig, Germany.,Dhirubhai Ambani Institute of Information and Communication Technology, Gandhinagar 382 007, India
| | - Jörg Schnauß
- Peter Debye Institute for Soft Matter Physics, University of Leipzig, Linnéstraße 5, 04103 Leipzig, Germany.,Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, 04103 Leipzig, Germany.,Unconventional Computing Laboratory, Department of Computer Science, University of the West of England, Bristol, United Kingdom
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37
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Zhang N, Shan H, Liu M, Li T, Luo R, Yang L, Qi L, Chu X, Su X, Wang R, Liu Y, Sun W, Shen QT. Structure and assembly of double-headed Sendai virus nucleocapsids. Commun Biol 2021; 4:494. [PMID: 33888861 PMCID: PMC8062630 DOI: 10.1038/s42003-021-02027-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 03/23/2021] [Indexed: 01/17/2023] Open
Abstract
Paramyxoviruses, including the mumps virus, measles virus, Nipah virus and Sendai virus (SeV), have non-segmented single-stranded negative-sense RNA genomes which are encapsidated by nucleoproteins into helical nucleocapsids. Here, we reported a double-headed SeV nucleocapsid assembled in a tail-to-tail manner, and resolved its helical stems and clam-shaped joint at the respective resolutions of 2.9 and 3.9 Å, via cryo-electron microscopy. Our structures offer important insights into the mechanism of the helical polymerization, in particular via an unnoticed exchange of a N-terminal hole formed by three loops of nucleoproteins, and unveil the clam-shaped joint in a hyper-closed state for nucleocapsid dimerization. Direct visualization of the loop from the disordered C-terminal tail provides structural evidence that C-terminal tail is correlated to the curvature of nucleocapsid and links nucleocapsid condensation and genome replication and transcription with different assembly forms.
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Affiliation(s)
- Na Zhang
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Hong Shan
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Mingdong Liu
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Tianhao Li
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Rui Luo
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Liuyan Yang
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
- College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Lei Qi
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
| | - Xiaofeng Chu
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xin Su
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Rui Wang
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Yunhui Liu
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Wenzhi Sun
- Chinese Institute for Brain Research, Beijing, China
- School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - Qing-Tao Shen
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai, China.
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.
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38
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Özdemir B, Reski R. Automated and semi-automated enhancement, segmentation and tracing of cytoskeletal networks in microscopic images: A review. Comput Struct Biotechnol J 2021; 19:2106-2120. [PMID: 33995906 PMCID: PMC8085673 DOI: 10.1016/j.csbj.2021.04.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 04/05/2021] [Accepted: 04/07/2021] [Indexed: 11/28/2022] Open
Abstract
Cytoskeletal filaments are structures of utmost importance to biological cells and organisms due to their versatility and the significant functions they perform. These biopolymers are most often organised into network-like scaffolds with a complex morphology. Understanding the geometrical and topological organisation of these networks provides key insights into their functional roles. However, this non-trivial task requires a combination of high-resolution microscopy and sophisticated image processing/analysis software. The correct analysis of the network structure and connectivity needs precise segmentation of microscopic images. While segmentation of filament-like objects is a well-studied concept in biomedical imaging, where tracing of neurons and blood vessels is routine, there are comparatively fewer studies focusing on the segmentation of cytoskeletal filaments and networks from microscopic images. The developments in the fields of microscopy, computer vision and deep learning, however, began to facilitate the task, as reflected by an increase in the recent literature on the topic. Here, we aim to provide a short summary of the research on the (semi-)automated enhancement, segmentation and tracing methods that are particularly designed and developed for microscopic images of cytoskeletal networks. In addition to providing an overview of the conventional methods, we cover the recently introduced, deep-learning-assisted methods alongside the advantages they offer over classical methods.
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Affiliation(s)
- Bugra Özdemir
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, Freiburg, Germany
| | - Ralf Reski
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, Freiburg, Germany.,Cluster of Excellence livMatS @ FIT - Freiburg Centre for Interactive Materials and Bioinspired Technologies, Freiburg, Germany
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Bibeau JP, Gray S, De La Cruz EM. Clusters of a Few Bound Cofilins Sever Actin Filaments. J Mol Biol 2021; 433:166833. [PMID: 33524412 DOI: 10.1016/j.jmb.2021.166833] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/12/2021] [Accepted: 01/14/2021] [Indexed: 02/06/2023]
Abstract
Cofilin is an essential actin filament severing protein that accelerates the assembly dynamics and turnover of actin networks by increasing the number of filament ends where subunits add and dissociate. It binds filament subunits stoichiometrically and cooperatively, forming clusters of contiguously-bound cofilin at sub-saturating occupancies. Filaments partially occupied with cofilin sever at boundaries between bare and cofilin-decorated segments. Imaging studies concluded that bound clusters must reach a critical size (Cc) of 13-100 cofilins to sever filaments. In contrast, structural and modeling studies suggest that a few or even a single cofilin can sever filaments, possibly with different severing rate constants. How clusters grow through the cooperative incorporation of additional cofilin molecules, specifically if they elongate asymmetrically or uniformly from both ends and if they are modulated by filament shape and external force, also lacks consensus. Here, using hydrodynamic flow to visualize individual actin filaments with TIRF microscopy, we found that neither flow-induced filament bending, tension, nor surface attachment conditions substantially affected the kinetics of cofilin binding to actin filaments. Clusters of bound cofilin preferentially extended toward filament pointed ends and displayed severing competency at small sizes (Cc < 3), with no detectable severing dependence on cluster size. These data support models in which small clusters of cofilin introduce local, but asymmetric, structural changes in actin filaments that promote filament severing with a rate constant that depends weakly on the size of the cluster.
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Affiliation(s)
- Jeffrey P Bibeau
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, United States
| | - Shawn Gray
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, United States
| | - Enrique M De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, United States.
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40
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Ojkic N, Lilja E, Direito S, Dawson A, Allen RJ, Waclaw B. A Roadblock-and-Kill Mechanism of Action Model for the DNA-Targeting Antibiotic Ciprofloxacin. Antimicrob Agents Chemother 2020; 64:e02487-19. [PMID: 32601161 PMCID: PMC7449190 DOI: 10.1128/aac.02487-19] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 06/19/2020] [Indexed: 12/19/2022] Open
Abstract
Fluoroquinolones, antibiotics that cause DNA damage by inhibiting DNA topoisomerases, are clinically important, but their mechanism of action is not yet fully understood. In particular, the dynamical response of bacterial cells to fluoroquinolone exposure has hardly been investigated, although the SOS response, triggered by DNA damage, is often thought to play a key role. Here, we investigated the growth inhibition of the bacterium Escherichia coli by the fluoroquinolone ciprofloxacin at low concentrations. We measured the long-term and short-term dynamical response of the growth rate and DNA production rate to ciprofloxacin at both the population and single-cell levels. We show that, despite the molecular complexity of DNA metabolism, a simple roadblock-and-kill model focusing on replication fork blockage and DNA damage by ciprofloxacin-poisoned DNA topoisomerase II (gyrase) quantitatively reproduces long-term growth rates in the presence of ciprofloxacin. The model also predicts dynamical changes in the DNA production rate in wild-type E. coli and in a recombination-deficient mutant following a step-up of ciprofloxacin. Our work highlights that bacterial cells show a delayed growth rate response following fluoroquinolone exposure. Most importantly, our model explains why the response is delayed: it takes many doubling times to fragment the DNA sufficiently to inhibit gene expression. We also show that the dynamical response is controlled by the timescale of DNA replication and gyrase binding/unbinding to the DNA rather than by the SOS response, challenging the accepted view. Our work highlights the importance of including detailed biophysical processes in biochemical-systems models to quantitatively predict the bacterial response to antibiotics.
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Affiliation(s)
- Nikola Ojkic
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
| | - Elin Lilja
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
| | - Susana Direito
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
| | - Angela Dawson
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
| | - Rosalind J Allen
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
- Centre for Synthetic and Systems Biology, Edinburgh, United Kingdom
| | - Bartlomiej Waclaw
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
- Centre for Synthetic and Systems Biology, Edinburgh, United Kingdom
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41
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Modes of action of the archaeal Mre11/Rad50 DNA-repair complex revealed by fast-scan atomic force microscopy. Proc Natl Acad Sci U S A 2020; 117:14936-14947. [PMID: 32541055 PMCID: PMC7334584 DOI: 10.1073/pnas.1915598117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The Mre11/Rad50 (M/R) complex forms the core of an essential DNA-repair complex, conserved in all divisions of life. Here we investigate this complex from the thermophilic archaeon Sulfolobus acidocaldarius using real-time atomic force microscopy. We demonstrate that the coiled-coil regions of Rad50 facilitate M/R interaction with DNA and permit substrate translocation until a free end is encountered. We also observe that the M/R complex drives unprecedented unwinding of the DNA duplexes. Taking these findings together, we provide a model for how the M/R complex can identify DNA double-strand breaks and orchestrate repair events. Mre11 and Rad50 (M/R) proteins are part of an evolutionarily conserved macromolecular apparatus that maintains genomic integrity through repair pathways. Prior structural studies have revealed that this apparatus is extremely dynamic, displaying flexibility in the long coiled-coil regions of Rad50, a member of the structural maintenance of chromosome (SMC) superfamily of ATPases. However, many details of the mechanics of M/R chromosomal manipulation during DNA-repair events remain unclear. Here, we investigate the properties of the thermostable M/R complex from the archaeon Sulfolobus acidocaldarius using atomic force microscopy (AFM) to understand how this macromolecular machinery orchestrates DNA repair. While previous studies have observed canonical interactions between the globular domains of M/R and DNA, we observe transient interactions between DNA substrates and the Rad50 coiled coils. Fast-scan AFM videos (at 1–2 frames per second) of M/R complexes reveal that these interactions result in manipulation and translocation of the DNA substrates. Our study also shows dramatic and unprecedented ATP-dependent DNA unwinding events by the M/R complex, which extend hundreds of base pairs in length. Supported by molecular dynamic simulations, we propose a model for M/R recognition at DNA breaks in which the Rad50 coiled coils aid movement along DNA substrates until a DNA end is encountered, after which the DNA unwinding activity potentiates the downstream homologous recombination (HR)-mediated DNA repair.
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Dimchev G, Amiri B, Humphries AC, Schaks M, Dimchev V, Stradal TEB, Faix J, Krause M, Way M, Falcke M, Rottner K. Lamellipodin tunes cell migration by stabilizing protrusions and promoting adhesion formation. J Cell Sci 2020; 133:jcs239020. [PMID: 32094266 PMCID: PMC7157940 DOI: 10.1242/jcs.239020] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 02/19/2020] [Indexed: 01/01/2023] Open
Abstract
Efficient migration on adhesive surfaces involves the protrusion of lamellipodial actin networks and their subsequent stabilization by nascent adhesions. The actin-binding protein lamellipodin (Lpd) is thought to play a critical role in lamellipodium protrusion, by delivering Ena/VASP proteins onto the growing plus ends of actin filaments and by interacting with the WAVE regulatory complex, an activator of the Arp2/3 complex, at the leading edge. Using B16-F1 melanoma cell lines, we demonstrate that genetic ablation of Lpd compromises protrusion efficiency and coincident cell migration without altering essential parameters of lamellipodia, including their maximal rate of forward advancement and actin polymerization. We also confirmed lamellipodia and migration phenotypes with CRISPR/Cas9-mediated Lpd knockout Rat2 fibroblasts, excluding cell type-specific effects. Moreover, computer-aided analysis of cell-edge morphodynamics on B16-F1 cell lamellipodia revealed that loss of Lpd correlates with reduced temporal protrusion maintenance as a prerequisite of nascent adhesion formation. We conclude that Lpd optimizes protrusion and nascent adhesion formation by counteracting frequent, chaotic retraction and membrane ruffling.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Georgi Dimchev
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffen Strasse 7, 38124 Braunschweig, Germany
| | - Behnam Amiri
- Max Delbrück Center for Molecular Medicine, Robert Rössle Strasse 10, 13125 Berlin, Germany
| | - Ashley C Humphries
- Cellular Signalling and Cytoskeletal Function Laboratory, The Francis Crick Institute, London NW1 1AT, UK
| | - Matthias Schaks
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffen Strasse 7, 38124 Braunschweig, Germany
| | - Vanessa Dimchev
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffen Strasse 7, 38124 Braunschweig, Germany
| | - Theresia E B Stradal
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffen Strasse 7, 38124 Braunschweig, Germany
| | - Jan Faix
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Matthias Krause
- Randall Centre of Cell & Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL, UK
| | - Michael Way
- Cellular Signalling and Cytoskeletal Function Laboratory, The Francis Crick Institute, London NW1 1AT, UK
- Department of Infectious Disease, Imperial College, London W2 1PG, UK
| | - Martin Falcke
- Max Delbrück Center for Molecular Medicine, Robert Rössle Strasse 10, 13125 Berlin, Germany
- Department of Physics, Humboldt University, Newtonstrasse 15, 12489 Berlin, Germany
| | - Klemens Rottner
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffen Strasse 7, 38124 Braunschweig, Germany
- Braunschweig Integrated Centre of Systems Biology (BRICS), 38106 Braunschweig, Germany
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43
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Mosby LS, Hundt N, Young G, Fineberg A, Polin M, Mayor S, Kukura P, Köster DV. Myosin II Filament Dynamics in Actin Networks Revealed with Interferometric Scattering Microscopy. Biophys J 2020; 118:1946-1957. [PMID: 32191863 PMCID: PMC7175421 DOI: 10.1016/j.bpj.2020.02.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 02/25/2020] [Accepted: 02/25/2020] [Indexed: 11/30/2022] Open
Abstract
The plasma membrane and the underlying cytoskeletal cortex constitute active platforms for a variety of cellular processes. Recent work has shown that the remodeling acto-myosin network modifies local membrane organization, but the molecular details are only partly understood because of difficulties with experimentally accessing the relevant time and length scales. Here, we use interferometric scattering microscopy to investigate a minimal acto-myosin network linked to a supported lipid bilayer membrane. Using the magnitude of the interferometric contrast, which is proportional to molecular mass, and fast acquisition rates, we detect and image individual membrane-attached actin filaments diffusing within the acto-myosin network and follow individual myosin II filament dynamics. We quantify myosin II filament dwell times and processivity as functions of ATP concentration, providing experimental evidence for the predicted ensemble behavior of myosin head domains. Our results show how decreasing ATP concentrations lead to both increasing dwell times of individual myosin II filaments and a global change from a remodeling to a contractile state of the acto-myosin network.
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Affiliation(s)
- Lewis S Mosby
- Centre for Mechanochemical Cell Biology, University of Warwick, Coventry, United Kingdom; Physics Department, University of Warwick, Coventry, United Kingdom
| | - Nikolas Hundt
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Gavin Young
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Adam Fineberg
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Marco Polin
- Centre for Mechanochemical Cell Biology, University of Warwick, Coventry, United Kingdom; Physics Department, University of Warwick, Coventry, United Kingdom
| | - Satyajit Mayor
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bangalore, India; Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, India.
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom.
| | - Darius V Köster
- Centre for Mechanochemical Cell Biology, University of Warwick, Coventry, United Kingdom; Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
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44
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Cai X, Arias DS, Velazquez LR, Vexler S, Bevier AL, Fygenson DK. DNA Nunchucks: Nanoinstrumentation for Single-Molecule Measurement of Stiffness and Bending. NANO LETTERS 2020; 20:1388-1395. [PMID: 31872766 DOI: 10.1021/acs.nanolett.9b04980] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Bending of double-stranded DNA (dsDNA) has important applications in biology and engineering, but measurement of DNA bend angles is notoriously difficult and rarely dynamic. Here we introduce a nanoscale instrument that makes dynamic measurement of the bend in short dsDNAs easy enough to be routine. The instrument works by embedding the ends of a dsDNA in stiff, fluorescently labeled DNA nanotubes, thereby mechanically magnifying their orientations. The DNA nanotubes are readily confined to a plane and imaged while freely diffusing. Single-molecule bend angles are rapidly and reliably extracted from the images by a neural network. We find that angular variance across a population increases with dsDNA length, as predicted by the worm-like chain model, although individual distributions can differ significantly from one another. For dsDNAs with phased A6-tracts, we measure an intrinsic bend of 17 ± 1° per A6-tract, consistent with other methods, and a length-dependent angular variance that indicates A6-tracts are (80 ± 30)% stiffer than generic dsDNA.
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Affiliation(s)
- Xinyue Cai
- Department of Physics , University of California, Santa Barbara , Santa Barbara , California , United States
| | - D Sebastian Arias
- Department of Physics , University of California, Santa Barbara , Santa Barbara , California , United States
| | - Lourdes R Velazquez
- Department of Physics , University of California, Santa Barbara , Santa Barbara , California , United States
- Biomolecular Science & Engineering Program , University of California, Santa Barbara , Santa Barbara , California , United States
| | - Shelby Vexler
- Biomolecular Science & Engineering Program , University of California, Santa Barbara , Santa Barbara , California , United States
| | - Alexander L Bevier
- Department of Physics , University of California, Santa Barbara , Santa Barbara , California , United States
| | - D Kuchnir Fygenson
- Department of Physics , University of California, Santa Barbara , Santa Barbara , California , United States
- Biomolecular Science & Engineering Program , University of California, Santa Barbara , Santa Barbara , California , United States
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45
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Califar B, Sng NJ, Zupanska A, Paul AL, Ferl RJ. Root Skewing-Associated Genes Impact the Spaceflight Response of Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2020; 11:239. [PMID: 32194611 PMCID: PMC7064724 DOI: 10.3389/fpls.2020.00239] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 02/17/2020] [Indexed: 05/03/2023]
Abstract
The observation that plant roots skew in microgravity recently refuted the long-held conviction that skewing was a gravity-dependent phenomenon. Further, spaceflight root skewing suggests that specific root morphologies and cell wall remodeling systems may be important aspects of spaceflight physiological adaptation. However, connections between skewing, cell wall modification and spaceflight physiology are currently based on inferences rather than direct tests. Therefore, the Advanced Plant Experiments-03-2 (APEX-03-2) spaceflight study was designed to elucidate the contribution of two skewing- and cell wall-associated genes in Arabidopsis to root behavior and gene expression patterns in spaceflight, to assess whether interruptions of different skewing pathways affect the overall spaceflight-associated process. SPIRAL1 is a skewing-related protein implicated in directional cell expansion, and functions by regulating cortical microtubule dynamics. SKU5 is skewing-related glycosylphosphatidylinositol-anchored protein of the plasma membrane and cell wall implicated in stress response signaling. These two genes function in different cellular pathways that affect skewing on the Earth, and enable a test of the relevance of skewing pathways to spaceflight physiological adaptation. In this study, both sku5 and spr1 mutants showed different skewing behavior and markedly different patterns of gene expression in the spaceflight environment. The spr1 mutant showed fewer differentially expressed genes than its Col-0 wild-type, whereas sku5 showed considerably more than its WS wild-type. Developmental age played a substantial role in spaceflight acclimation in all genotypes, but particularly in sku5 plants, where spaceflight 4d seedlings had almost 10-times as many highly differentially expressed genes as the 8d seedlings. These differences demonstrated that the two skewing pathways represented by SKU5 and SPR1 have unique and opposite contributions to physiological adaptation to spaceflight. The spr1 response is less intense than wild type, suggesting that the loss of SPR1 positively impacts spaceflight adaptation. Conversely, the intensity of the sku5 responses suggests that the loss of SKU5 initiates a much more complex, deeper and more stress related response to spaceflight. This suggests that proper SKU5 function is important to spaceflight adaptation.
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Affiliation(s)
- Brandon Califar
- Horticultural Sciences, University of Florida, Gainesville, FL, United States
- The Genetics Institute, University of Florida, Gainesville, FL, United States
- Program in Genetics and Genomics, University of Florida, Gainesville, FL, United States
| | - Natasha J. Sng
- Horticultural Sciences, University of Florida, Gainesville, FL, United States
| | - Agata Zupanska
- Horticultural Sciences, University of Florida, Gainesville, FL, United States
| | - Anna-Lisa Paul
- Horticultural Sciences, University of Florida, Gainesville, FL, United States
- The Genetics Institute, University of Florida, Gainesville, FL, United States
- Program in Genetics and Genomics, University of Florida, Gainesville, FL, United States
- Program in Plant Molecular and Cellular Biology, University of Florida, Gainesville, FL, United States
- Interdisciplinary Center for Biotechnology and Research, University of Florida, Gainesville, FL, United States
- *Correspondence: Anna-Lisa Paul,
| | - Robert J. Ferl
- Horticultural Sciences, University of Florida, Gainesville, FL, United States
- The Genetics Institute, University of Florida, Gainesville, FL, United States
- Program in Genetics and Genomics, University of Florida, Gainesville, FL, United States
- Program in Plant Molecular and Cellular Biology, University of Florida, Gainesville, FL, United States
- Robert J. Ferl,
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46
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Bradley AO, Vizcarra CL, Bailey HM, Quinlan ME. Spire stimulates nucleation by Cappuccino and binds both ends of actin filaments. Mol Biol Cell 2019; 31:273-286. [PMID: 31877067 PMCID: PMC7183766 DOI: 10.1091/mbc.e19-09-0550] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The actin nucleators Spire and Cappuccino synergize to promote actin assembly, but the mechanism of their synergy is controversial. Together these proteins promote the formation of actin meshes, which are conserved structures that regulate the establishment of oocyte polarity. Direct interaction between Spire and Cappuccino is required for oogenesis and for in vitro synergistic actin assembly. This synergy is proposed to be driven by elongation and the formation of a ternary complex at filament barbed ends, or by nucleation and interaction at filament pointed ends. To mimic the geometry of Spire and Cappuccino in vivo, we immobilized Spire on beads and added Cappuccino and actin. Barbed ends, protected by Cappuccino, grow away from the beads while pointed ends are retained, as expected for nucleation-driven synergy. We found that Spire is sufficient to bind barbed ends and retain pointed ends of actin filaments near beads and we identified Spire’s barbed-end binding domain. Loss of barbed-end binding increases nucleation by Spire and synergy with Cappuccino in bulk pyrene assays and on beads. Importantly, genetic rescue by the loss-of-function mutant indicates that barbed-end binding is not necessary for oogenesis. Thus, increased nucleation is a critical element of synergy both in vitro and in vivo.
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Affiliation(s)
- Alexander O Bradley
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Christina L Vizcarra
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Hannah M Bailey
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Margot E Quinlan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095.,Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
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47
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Zhang T, Tang H, Vavylonis D, Cosgrove DJ. Disentangling loosening from softening: insights into primary cell wall structure. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 100:1101-1117. [PMID: 31469935 DOI: 10.1111/tpj.14519] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 08/08/2019] [Accepted: 08/19/2019] [Indexed: 05/13/2023]
Abstract
How cell wall elasticity, plasticity, and time-dependent extension (creep) relate to one another, to plant cell wall structure and to cell growth remain unsettled topics. To examine these issues without the complexities of living tissues, we treated cell-free strips of onion epidermal walls with various enzymes and other agents to assess which polysaccharides bear mechanical forces in-plane and out-of-plane of the cell wall. This information is critical for integrating concepts of wall structure, wall material properties, tissue mechanics and mechanisms of cell growth. With atomic force microscopy we also monitored real-time changes in the wall surface during treatments. Driselase, a potent cocktail of wall-degrading enzymes, removed cellulose microfibrils in superficial lamellae sequentially, layer-by-layer, and softened the wall (reduced its mechanical stiffness), yet did not induce wall loosening (creep). In contrast Cel12A, a bifunctional xyloglucanase/cellulase, induced creep with only subtle changes in wall appearance. Both Driselase and Cel12A increased the tensile compliance, but differently for elastic and plastic components. Homogalacturonan solubilization by pectate lyase and calcium chelation greatly increased the indentation compliance without changing tensile compliances. Acidic buffer induced rapid cell wall creep via endogenous α-expansins, with negligible effects on wall compliances. We conclude that these various wall properties are not tightly coupled and therefore reflect distinctive aspects of wall structure. Cross-lamellate networks of cellulose microfibrils influenced creep and tensile stiffness whereas homogalacturonan influenced indentation mechanics. This information is crucial for constructing realistic molecular models that define how wall mechanics and growth depend on primary cell wall structure.
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Affiliation(s)
- Tian Zhang
- Department of Biology and Center for Lignocellulose Structure and Formation, 208 Mueller Laboratory, Pennsylvania State University, University Park, State College, Pennsylvania, 16802, USA
| | - Haosu Tang
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania, 18015, USA
| | - Dimitrios Vavylonis
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania, 18015, USA
| | - Daniel J Cosgrove
- Department of Biology and Center for Lignocellulose Structure and Formation, 208 Mueller Laboratory, Pennsylvania State University, University Park, State College, Pennsylvania, 16802, USA
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48
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Koseki K, Taniguchi D, Yamashiro S, Mizuno H, Vavylonis D, Watanabe N. Lamellipodium tip actin barbed ends serve as a force sensor. Genes Cells 2019; 24:705-718. [PMID: 31514256 DOI: 10.1111/gtc.12720] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 09/04/2019] [Accepted: 09/04/2019] [Indexed: 01/31/2023]
Abstract
Cells change direction of migration by sensing rigidity of environment and traction force, yet its underlying mechanism is unclear. Here, we show that tip actin barbed ends serve as an active "force sensor" at the leading edge. We established a method to visualize intracellular single-molecule fluorescent actin through an elastic culture substrate. We found that immediately after cell edge stretch, actin assembly increased specifically at the lamellipodium tip. The rate of actin assembly increased with increasing stretch speed. Furthermore, tip actin polymerization remained elevated at the subsequent hold step, which was accompanied by a decrease in the load on the tip barbed ends. Stretch-induced tip actin polymerization was still observed without either the WAVE complex or Ena/VASP proteins. The observed relationships between forces and tip actin polymerization are consistent with a force-velocity relationship as predicted by the Brownian ratchet mechanism. Stretch caused extra membrane protrusion with respect to the stretched substrate and increased local tip polymerization by >5% of total cellular actin in 30 s. Our data reveal that augmentation of lamellipodium tip actin assembly is directly coupled to the load decrease, which may serve as a force sensor for directed cell protrusion.
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Affiliation(s)
- Kazuma Koseki
- Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Daisuke Taniguchi
- Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Sawako Yamashiro
- Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan.,Laboratory of Single-Molecule Cell Biology, Kyoto University Graduate School of Biostudies, Kyoto, Japan
| | - Hiroaki Mizuno
- Laboratory of Single-Molecule Cell Biology, Kyoto University Graduate School of Biostudies, Kyoto, Japan
| | | | - Naoki Watanabe
- Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan.,Laboratory of Single-Molecule Cell Biology, Kyoto University Graduate School of Biostudies, Kyoto, Japan
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Mandriota N, Friedsam C, Jones-Molina JA, Tatem KV, Ingber DE, Sahin O. Cellular nanoscale stiffness patterns governed by intracellular forces. NATURE MATERIALS 2019; 18:1071-1077. [PMID: 31209386 PMCID: PMC6754298 DOI: 10.1038/s41563-019-0391-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 04/30/2019] [Indexed: 05/24/2023]
Abstract
Cell stiffness measurements have led to insights into various physiological and pathological processes1,2. Although many cellular behaviours are influenced by intracellular mechanical forces3-6 that also alter the material properties of the cell, the precise mechanistic relationship between intracellular forces and cell stiffness remains unclear. Here we develop a cell mechanical imaging platform with high spatial resolution that reveals the existence of nanoscale stiffness patterns governed by intracellular forces. On the basis of these findings, we develop and validate a cellular mechanical model that quantitatively relates cell stiffness to intracellular forces. This allows us to determine the magnitude of tension within actin bundles, cell cortex and plasma membrane from the cell stiffness patterns across individual cells. These results expand our knowledge on the mechanical interaction between cells and their environments, and offer an alternative approach to determine physiologically relevant intracellular forces from high-resolution cell stiffness images.
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Affiliation(s)
- Nicola Mandriota
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Claudia Friedsam
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
| | | | - Kathleen V Tatem
- Department of Biological Sciences, Columbia University, New York, NY, USA
- Department of Physics, Columbia University, New York, NY, USA
| | - Donald E Ingber
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Vascular Biology Program and Departments of Surgery, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Ozgur Sahin
- Department of Biological Sciences, Columbia University, New York, NY, USA.
- Department of Physics, Columbia University, New York, NY, USA.
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50
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Khanna K, Lopez-Garrido J, Zhao Z, Watanabe R, Yuan Y, Sugie J, Pogliano K, Villa E. The molecular architecture of engulfment during Bacillus subtilis sporulation. eLife 2019; 8:45257. [PMID: 31282858 PMCID: PMC6684271 DOI: 10.7554/elife.45257] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 07/04/2019] [Indexed: 01/08/2023] Open
Abstract
The study of bacterial cell biology is limited by difficulties in visualizing cellular structures at high spatial resolution within their native milieu. Here, we visualize Bacillus subtilis sporulation using cryo-electron tomography coupled with cryo-focused ion beam milling, allowing the reconstruction of native-state cellular sections at molecular resolution. During sporulation, an asymmetrically-positioned septum generates a larger mother cell and a smaller forespore. Subsequently, the mother cell engulfs the forespore. We show that the septal peptidoglycan is not completely degraded at the onset of engulfment. Instead, the septum is uniformly and only slightly thinned as it curves towards the mother cell. Then, the mother cell membrane migrates around the forespore in tiny finger-like projections, whose formation requires the mother cell SpoIIDMP protein complex. We propose that a limited number of SpoIIDMP complexes tether to and degrade the peptidoglycan ahead of the engulfing membrane, generating an irregular membrane front.
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Affiliation(s)
- Kanika Khanna
- Division of Biological SciencesUniversity of California, San DiegoLa JollaUnited States
| | - Javier Lopez-Garrido
- Division of Biological SciencesUniversity of California, San DiegoLa JollaUnited States
| | - Ziyi Zhao
- Division of Biological SciencesUniversity of California, San DiegoLa JollaUnited States
| | - Reika Watanabe
- Division of Biological SciencesUniversity of California, San DiegoLa JollaUnited States
| | - Yuan Yuan
- Division of Biological SciencesUniversity of California, San DiegoLa JollaUnited States
| | - Joseph Sugie
- Division of Biological SciencesUniversity of California, San DiegoLa JollaUnited States
| | - Kit Pogliano
- Division of Biological SciencesUniversity of California, San DiegoLa JollaUnited States
| | - Elizabeth Villa
- Division of Biological SciencesUniversity of California, San DiegoLa JollaUnited States
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