1
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Xu XP, Cao W, Swift MF, Pandit NG, Huehn AE, Sindelar CV, De La Cruz EM, Hanein D, Volkmann N. High-resolution yeast actin structures indicate the molecular mechanism of actin filament stiffening by cations. Commun Chem 2024; 7:164. [PMID: 39079963 PMCID: PMC11289367 DOI: 10.1038/s42004-024-01243-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2024] [Accepted: 07/10/2024] [Indexed: 08/02/2024] Open
Abstract
Actin filament assembly and the regulation of its mechanical properties are fundamental processes essential for eukaryotic cell function. Residue E167 in vertebrate actins forms an inter-subunit salt bridge with residue K61 of the adjacent subunit. Saccharomyces cerevisiae actin filaments are more flexible than vertebrate filaments and have an alanine at this position (A167). Substitution of this alanine for a glutamic acid (A167E) confers Saccharomyces cerevisiae actin filaments with salt-dependent stiffness similar to vertebrate actins. We developed an optimized cryogenic electron microscopy workflow refining sample preparation and vitrification to obtain near-atomic resolution structures of wild-type and A167E mutant Saccharomyces cerevisiae actin filaments. The difference between these structures allowed us to pinpoint the potential binding site of a filament-associated cation that controls the stiffness of the filaments in vertebrate and A167E Saccharomyces cerevisiae actins. Through an analysis of previously published high-resolution reconstructions of vertebrate actin filaments, along with a newly determined high-resolution vertebrate actin structure in the absence of potassium, we identified a unique peak near residue 167 consistent with the binding of a magnesium ion. Our findings show how magnesium can contribute to filament stiffening by directly bridging actin subunits and allosterically affecting the orientation of the DNase-I binding loop of actin, which plays a regulatory role in modulating actin filament stiffness and interactions with regulatory proteins.
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Affiliation(s)
- Xiao-Ping Xu
- Scintillon Institute, 6868 Nancy Ridge Drive, San Diego, CA, 92121, USA
| | - Wenxiang Cao
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA
| | - Mark F Swift
- Scintillon Institute, 6868 Nancy Ridge Drive, San Diego, CA, 92121, USA
| | - Nandan G Pandit
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA
| | - Andrew E Huehn
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA
| | - Charles V Sindelar
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA
| | - Enrique M De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA
| | - Dorit Hanein
- Department of Chemistry and Biochemistry and Department of Biological Engineering, University of California, Santa Barbara, CA, 93106, USA.
| | - Niels Volkmann
- Department of Biological Engineering, Department of Electrical and Computer Engineering, Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, 93106, USA.
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2
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Homa KE, Hocky GM, Suarez C, Kovar DR. Arp2/3 complex- and formin-mediated actin cytoskeleton networks facilitate actin binding protein sorting in fission yeast. Eur J Cell Biol 2024; 103:151404. [PMID: 38493594 PMCID: PMC11211059 DOI: 10.1016/j.ejcb.2024.151404] [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: 11/07/2023] [Revised: 03/01/2024] [Accepted: 03/13/2024] [Indexed: 03/19/2024] Open
Abstract
While it is well-established that F-actin networks with specific organizations and dynamics are tightly regulated by distinct sets of associated actin-binding proteins (ABPs), how ABPs self-sort to particular F-actin networks remains largely unclear. We report that actin assembly factors Arp2/3 complex and formin Cdc12 tune the association of ABPs fimbrin Fim1 and tropomyosin Cdc8 to different F-actin networks in fission yeast. Genetic and pharmacological disruption of F-actin networks revealed that Fim1 is preferentially directed to Arp2/3-complex mediated actin patches, whereas Cdc8 is preferentially targeted to formin Cdc12-mediated filaments in the contractile ring. To investigate the role of Arp2/3 complex- and formin Cdc12-mediated actin assembly, we used four-color TIRF microscopy to observe the in vitro reconstitution of ABP sorting with purified proteins. Fim1 or Cdc8 alone bind similarly well to filaments assembled by either assembly factor. However, in 'competition' reactions containing both actin assembly factors and both ABPs, ∼2.0-fold more Fim1 and ∼3.5-fold more Cdc8 accumulates on Arp2/3 complex branch points and formin Cdc12-assembled actin filaments, respectively. These findings indicate that F-actin assembly factors Arp2/3 complex and formin Cdc12 help facilitate the recruitment of specific ABPs, thereby tuning ABP sorting and subsequently establishing the identity of F-actin networks in fission yeast.
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Affiliation(s)
- Kaitlin E Homa
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, United States
| | - Glen M Hocky
- Department of Chemistry, New York University, New York, NY, United States
| | - Cristian Suarez
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, United States
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, United States; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, United States.
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3
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Conboy JP, Istúriz Petitjean I, van der Net A, Koenderink GH. How cytoskeletal crosstalk makes cells move: Bridging cell-free and cell studies. BIOPHYSICS REVIEWS 2024; 5:021307. [PMID: 38840976 PMCID: PMC11151447 DOI: 10.1063/5.0198119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 05/13/2024] [Indexed: 06/07/2024]
Abstract
Cell migration is a fundamental process for life and is highly dependent on the dynamical and mechanical properties of the cytoskeleton. Intensive physical and biochemical crosstalk among actin, microtubules, and intermediate filaments ensures their coordination to facilitate and enable migration. In this review, we discuss the different mechanical aspects that govern cell migration and provide, for each mechanical aspect, a novel perspective by juxtaposing two complementary approaches to the biophysical study of cytoskeletal crosstalk: live-cell studies (often referred to as top-down studies) and cell-free studies (often referred to as bottom-up studies). We summarize the main findings from both experimental approaches, and we provide our perspective on bridging the two perspectives to address the open questions of how cytoskeletal crosstalk governs cell migration and makes cells move.
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Affiliation(s)
- James P. Conboy
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Irene Istúriz Petitjean
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Anouk van der Net
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Gijsje H. Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
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4
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Walker C, Chandrasekaran A, Mansour D, Graham K, Torres A, Wang L, Lafer EM, Rangamani P, Stachowiak JC. Liquid-like condensates that bind actin drive filament polymerization and bundling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.04.592527. [PMID: 38826190 PMCID: PMC11142076 DOI: 10.1101/2024.05.04.592527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Liquid-like protein condensates perform diverse physiological functions. Previous work showed that VASP, a processive actin polymerase, forms condensates that polymerize and bundle actin. To minimize their curvature, filaments accumulated at the inner condensate surface, ultimately deforming the condensate into a rod-like shape, filled with a bundle of parallel filaments. Here we show that this behavior does not require proteins with specific polymerase activity. Specifically, we found that condensates composed of Lamellipodin, a protein that binds actin but is not an actin polymerase, were also capable of polymerizing and bundling actin filaments. To probe the minimum requirements for condensate-mediated actin bundling, we developed an agent-based computational model. Guided by its predictions, we hypothesized that any condensate-forming protein that binds actin could bundle filaments through multivalent crosslinking. To test this idea, we added an actin-binding motif to Eps15, a condensate-forming protein that does not normally bind actin. The resulting chimera formed condensates that drove efficient actin polymerization and bundling. Collectively, these findings broaden the family of proteins that could organize cytoskeletal filaments to include any actin-binding protein that participates in protein condensation.
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Affiliation(s)
- Caleb Walker
- Biomedical Engineering, The University of Texas at Austin, Austin, TX, United States
| | - Aravind Chandrasekaran
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, United States
| | - Daniel Mansour
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, United States
| | - Kristin Graham
- Cell and Molecular Biology, The University of Texas at Austin, Austin, TX, United States
| | - Andrea Torres
- Biomedical Engineering, The University of Texas at Austin, Austin, TX, United States
| | - Liping Wang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
| | - Eileen M. Lafer
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, United States
| | - Jeanne C. Stachowiak
- Biomedical Engineering, The University of Texas at Austin, Austin, TX, United States
- Chemical Engineering, The University of Texas at Austin, Austin, TX, United States
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5
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Morrison JJ, Camberg JL. Building the Bacterial Divisome at the Septum. Subcell Biochem 2024; 104:49-71. [PMID: 38963483 DOI: 10.1007/978-3-031-58843-3_4] [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: 07/05/2024]
Abstract
Across living organisms, division is necessary for cell survival and passing heritable information to the next generation. For this reason, cell division is highly conserved among eukaryotes and prokaryotes. Among the most highly conserved cell division proteins in eukaryotes are tubulin and actin. Tubulin polymerizes to form microtubules, which assemble into cytoskeletal structures in eukaryotes, such as the mitotic spindle that pulls chromatids apart during mitosis. Actin polymerizes to form a morphological framework for the eukaryotic cell, or cytoskeleton, that undergoes reorganization during mitosis. In prokaryotes, two of the most highly conserved cell division proteins are the tubulin homolog FtsZ and the actin homolog FtsA. In this chapter, the functions of the essential bacterial cell division proteins FtsZ and FtsA and their roles in assembly of the divisome at the septum, the site of cell division, will be discussed. In most bacteria, including Escherichia coli, the tubulin homolog FtsZ polymerizes at midcell, and this step is crucial for recruitment of many other proteins to the division site. For this reason, both FtsZ abundance and polymerization are tightly regulated by a variety of proteins. The actin-like FtsA protein polymerizes and tethers FtsZ polymers to the cytoplasmic membrane. Additionally, FtsA interacts with later stage cell division proteins, which are essential for division and for building the new cell wall at the septum. Recent studies have investigated how actin-like polymerization of FtsA on the lipid membrane may impact division, and we will discuss this and other ways that division in bacteria is regulated through FtsZ and FtsA.
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Affiliation(s)
- Josiah J Morrison
- Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, RI, USA
| | - Jodi L Camberg
- Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, RI, USA.
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6
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Mao W, Renner LD, Cornilleau C, Li de la Sierra-Gallay I, Afensiss S, Benlamara S, Ah-Seng Y, Van Tilbeurgh H, Nessler S, Bertin A, Chastanet A, Carballido-Lopez R. On the role of nucleotides and lipids in the polymerization of the actin homolog MreB from a Gram-positive bacterium. eLife 2023; 12:e84505. [PMID: 37818717 PMCID: PMC10718530 DOI: 10.7554/elife.84505] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 10/08/2023] [Indexed: 10/12/2023] Open
Abstract
In vivo, bacterial actin MreB assembles into dynamic membrane-associated filamentous structures that exhibit circumferential motion around the cell. Current knowledge of MreB biochemical and polymerization properties in vitro remains limited and is mostly based on MreB proteins from Gram-negative species. In this study, we report the first observation of organized protofilaments by electron microscopy and the first 3D-structure of MreB from a Gram-positive bacterium. We show that Geobacillus stearothermophilus MreB forms straight pairs of protofilaments on lipid surfaces in the presence of ATP or GTP, but not in the presence of ADP, GDP or non-hydrolysable ATP analogs. We demonstrate that membrane anchoring is mediated by two spatially close short hydrophobic sequences while electrostatic interactions also contribute to lipid binding, and show that the population of membrane-bound protofilament doublets is in steady-state. In solution, protofilament doublets were not detected in any condition tested. Instead, MreB formed large sheets regardless of the bound nucleotide, albeit at a higher critical concentration. Altogether, our results indicate that both lipids and ATP are facilitators of MreB polymerization, and are consistent with a dual effect of ATP hydrolysis, in promoting both membrane binding and filaments assembly/disassembly.
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Affiliation(s)
- Wei Mao
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis InstituteJouy-en-JosasFrance
| | - Lars D Renner
- Leibniz Institute of Polymer Research, and the Max-Bergmann-Center of BiomaterialsDresdenGermany
| | - Charlène Cornilleau
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis InstituteJouy-en-JosasFrance
| | - Ines Li de la Sierra-Gallay
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRSGif-sur-YvetteFrance
| | - Sana Afensiss
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis InstituteJouy-en-JosasFrance
| | - Sarah Benlamara
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis InstituteJouy-en-JosasFrance
| | - Yoan Ah-Seng
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis InstituteJouy-en-JosasFrance
| | - Herman Van Tilbeurgh
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRSGif-sur-YvetteFrance
| | - Sylvie Nessler
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRSGif-sur-YvetteFrance
| | - Aurélie Bertin
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, Sorbonne Université, 75005ParisFrance
| | - Arnaud Chastanet
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis InstituteJouy-en-JosasFrance
| | - Rut Carballido-Lopez
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis InstituteJouy-en-JosasFrance
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7
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Park J, Bird JE. The actin cytoskeleton in hair bundle development and hearing loss. Hear Res 2023; 436:108817. [PMID: 37300948 PMCID: PMC10408727 DOI: 10.1016/j.heares.2023.108817] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 05/18/2023] [Accepted: 05/25/2023] [Indexed: 06/12/2023]
Abstract
Inner ear hair cells assemble mechanosensitive hair bundles on their apical surface that transduce sounds and accelerations. Each hair bundle is comprised of ∼ 100 individual stereocilia that are arranged into rows of increasing height and width; their specific and precise architecture being necessary for mechanoelectrical transduction (MET). The actin cytoskeleton is fundamental to establishing this architecture, not only by forming the structural scaffold shaping each stereocilium, but also by composing rootlets and the cuticular plate that together provide a stable foundation supporting each stereocilium. In concert with the actin cytoskeleton, a large assortment of actin-binding proteins (ABPs) function to cross-link actin filaments into specific topologies, as well as control actin filament growth, severing, and capping. These processes are individually critical for sensory transduction and are all disrupted in hereditary forms of human hearing loss. In this review, we provide an overview of actin-based structures in the hair bundle and the molecules contributing to their assembly and functional properties. We also highlight recent advances in mechanisms driving stereocilia elongation and how these processes are tuned by MET.
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Affiliation(s)
- Jinho Park
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610, United States; Myology Institute, University of Florida, Gainesville, FL 32610, United States
| | - Jonathan E Bird
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610, United States; Myology Institute, University of Florida, Gainesville, FL 32610, United States.
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8
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Demosthene B, Lee M, Marracino RR, Heidings JB, Kang EH. Molecular Basis for Actin Polymerization Kinetics Modulated by Solution Crowding. Biomolecules 2023; 13:biom13050786. [PMID: 37238656 DOI: 10.3390/biom13050786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Revised: 04/18/2023] [Accepted: 04/25/2023] [Indexed: 05/28/2023] Open
Abstract
Actin polymerization drives cell movement and provides cells with structural integrity. Intracellular environments contain high concentrations of solutes, including organic compounds, macromolecules, and proteins. Macromolecular crowding has been shown to affect actin filament stability and bulk polymerization kinetics. However, the molecular mechanisms behind how crowding influences individual actin filament assembly are not well understood. In this study, we investigated how crowding modulates filament assembly kinetics using total internal reflection fluorescence (TIRF) microscopy imaging and pyrene fluorescence assays. The elongation rates of individual actin filaments analyzed from TIRF imaging depended on the type of crowding agent (polyethylene glycol, bovine serum albumin, and sucrose) as well as their concentrations. Further, we utilized all-atom molecular dynamics (MD) simulations to evaluate the effects of crowding molecules on the diffusion of actin monomers during filament assembly. Taken together, our data suggest that solution crowding can regulate actin assembly kinetics at the molecular level.
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Affiliation(s)
- Bryan Demosthene
- NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA
- Burnett School of Biomedical Sciences, University of Central Florida, Orlando, FL 32827, USA
| | - Myeongsang Lee
- NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA
| | - Ryan R Marracino
- NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA
- Burnett School of Biomedical Sciences, University of Central Florida, Orlando, FL 32827, USA
| | - James B Heidings
- NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA
- Burnett School of Biomedical Sciences, University of Central Florida, Orlando, FL 32827, USA
| | - Ellen Hyeran Kang
- NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA
- Department of Physics, University of Central Florida, Orlando, FL 32816, USA
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32816, USA
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9
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Abstract
Actin cytoskeleton force generation, sensing, and adaptation are dictated by the bending and twisting mechanics of filaments. Here, we use magnetic tweezers and microfluidics to twist and pull individual actin filaments and evaluate their response to applied loads. Twisted filaments bend and dissipate torsional strain by adopting a supercoiled plectoneme. Pulling prevents plectoneme formation, which causes twisted filaments to sever. Analysis over a range of twisting and pulling forces and direct visualization of filament and single subunit twisting fluctuations yield an actin filament torsional persistence length of ~10 µm, similar to the bending persistence length. Filament severing by cofilin is driven by local twist strain at boundaries between bare and decorated segments and is accelerated by low pN pulling forces. This work explains how contractile forces generated by myosin motors accelerate filament severing by cofilin and establishes a role for filament twisting in the regulation of actin filament stability and assembly dynamics.
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10
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Reynolds MJ, Hachicho C, Carl AG, Gong R, Alushin GM. Bending forces and nucleotide state jointly regulate F-actin structure. Nature 2022; 611:380-386. [PMID: 36289330 PMCID: PMC9646526 DOI: 10.1038/s41586-022-05366-w] [Citation(s) in RCA: 39] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 09/20/2022] [Indexed: 02/05/2023]
Abstract
ATP-hydrolysis-coupled actin polymerization is a fundamental mechanism of cellular force generation1-3. In turn, force4,5 and actin filament (F-actin) nucleotide state6 regulate actin dynamics by tuning F-actin's engagement of actin-binding proteins through mechanisms that are unclear. Here we show that the nucleotide state of actin modulates F-actin structural transitions evoked by bending forces. Cryo-electron microscopy structures of ADP-F-actin and ADP-Pi-F-actin with sufficient resolution to visualize bound solvent reveal intersubunit interfaces bridged by water molecules that could mediate filament lattice flexibility. Despite extensive ordered solvent differences in the nucleotide cleft, these structures feature nearly identical lattices and essentially indistinguishable protein backbone conformations that are unlikely to be discriminable by actin-binding proteins. We next introduce a machine-learning-enabled pipeline for reconstructing bent filaments, enabling us to visualize both continuous structural variability and side-chain-level detail. Bent F-actin structures reveal rearrangements at intersubunit interfaces characterized by substantial alterations of helical twist and deformations in individual protomers, transitions that are distinct in ADP-F-actin and ADP-Pi-F-actin. This suggests that phosphate rigidifies actin subunits to alter the bending structural landscape of F-actin. As bending forces evoke nucleotide-state dependent conformational transitions of sufficient magnitude to be detected by actin-binding proteins, we propose that actin nucleotide state can serve as a co-regulator of F-actin mechanical regulation.
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Affiliation(s)
- Matthew J Reynolds
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
| | - Carla Hachicho
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
| | - Ayala G Carl
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
- Tri-Institutional Program in Chemical Biology, The Rockefeller University, New York, NY, USA
| | - Rui Gong
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
| | - Gregory M Alushin
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA.
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11
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Abstract
One of the major challenges of bottom-up synthetic biology is rebuilding a minimal cell division machinery. From a reconstitution perspective, the animal cell division apparatus is mechanically the simplest and therefore attractive to rebuild. An actin-based ring produces contractile force to constrict the membrane. By contrast, microbes and plant cells have a cell wall, so division requires concerted membrane constriction and cell wall synthesis. Furthermore, reconstitution of the actin division machinery helps in understanding the physical and molecular mechanisms of cytokinesis in animal cells and thus our own cells. In this review, we describe the state-of-the-art research on reconstitution of minimal actin-mediated cytokinetic machineries. Based on the conceptual requirements that we obtained from the physics of the shape changes involved in cell division, we propose two major routes for building a minimal actin apparatus capable of division. Importantly, we acknowledge both the passive and active roles that the confining lipid membrane can play in synthetic cytokinesis. We conclude this review by identifying the most pressing challenges for future reconstitution work, thereby laying out a roadmap for building a synthetic cell equipped with a minimal actin division machinery.
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12
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How do cells stiffen? Biochem J 2022; 479:1825-1842. [PMID: 36094371 DOI: 10.1042/bcj20210806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 08/21/2022] [Accepted: 08/24/2022] [Indexed: 11/17/2022]
Abstract
Cell stiffness is an important characteristic of cells and their response to external stimuli. In this review, we survey methods used to measure cell stiffness, summarize stimuli that alter cell stiffness, and discuss signaling pathways and mechanisms that control cell stiffness. Several pathological states are characterized by changes in cell stiffness, suggesting this property can serve as a potential diagnostic marker or therapeutic target. Therefore, we consider the effect of cell stiffness on signaling and growth processes required for homeostasis and dysfunction in healthy and pathological states. Specifically, the composition and structure of the cell membrane and cytoskeleton are major determinants of cell stiffness, and studies have identified signaling pathways that affect cytoskeletal dynamics both directly and by altered gene expression. We present the results of studies interrogating the effects of biophysical and biochemical stimuli on the cytoskeleton and other cellular components and how these factors determine the stiffness of both individual cells and multicellular structures. Overall, these studies represent an intersection of the fields of polymer physics, protein biochemistry, and mechanics, and identify specific mechanisms involved in mediating cell stiffness that can serve as therapeutic targets.
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13
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Hundt N, Cole D, Hantke MF, Miller JJ, Struwe WB, Kukura P. Direct observation of the molecular mechanism underlying protein polymerization. SCIENCE ADVANCES 2022; 8:eabm7935. [PMID: 36044567 PMCID: PMC9432825 DOI: 10.1126/sciadv.abm7935] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 07/19/2022] [Indexed: 06/15/2023]
Abstract
Protein assembly is a main route to generating complexity in living systems. Revealing the relevant molecular details is challenging because of the intrinsic heterogeneity of species ranging from few to hundreds of molecules. Here, we use mass photometry to quantify and monitor the full range of actin oligomers during polymerization with single-molecule sensitivity. We find that traditional nucleation-based models cannot account for the observed distributions of actin oligomers. Instead, the key step of filament formation is a slow transition between distinct states of an actin filament mediated by cation exchange or ATP hydrolysis. The resulting model reproduces important aspects of actin polymerization, such as the critical concentration for filament formation and bulk growth behavior. Our results revise the mechanism of actin nucleation, shed light on the role and function of actin-associated proteins, and introduce a general and quantitative means to studying protein assembly at the molecular level.
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Affiliation(s)
- Nikolas Hundt
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
- The Kavli Institute for Nanoscience Discovery, Oxford, UK
| | - Daniel Cole
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
- The Kavli Institute for Nanoscience Discovery, Oxford, UK
| | - Max F. Hantke
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
- The Kavli Institute for Nanoscience Discovery, Oxford, UK
| | - Jack J. Miller
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PT, UK
- The PET Research Centre and The MR Research Centre, Aarhus University, Aarhus, Denmark
| | - Weston B. Struwe
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
- The Kavli Institute for Nanoscience Discovery, Oxford, UK
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
- The Kavli Institute for Nanoscience Discovery, Oxford, UK
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14
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Wang Y, Peng Q, Mou X, Wang X, Li H, Han T, Sun Z, Wang X. A successful hybrid deep learning model aiming at promoter identification. BMC Bioinformatics 2022; 23:206. [PMID: 35641900 PMCID: PMC9158169 DOI: 10.1186/s12859-022-04735-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 05/16/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The zone adjacent to a transcription start site (TSS), namely, the promoter, is primarily involved in the process of DNA transcription initiation and regulation. As a result, proper promoter identification is critical for further understanding the mechanism of the networks controlling genomic regulation. A number of methodologies for the identification of promoters have been proposed. Nonetheless, due to the great heterogeneity existing in promoters, the results of these procedures are still unsatisfactory. In order to establish additional discriminative characteristics and properly recognize promoters, we developed the hybrid model for promoter identification (HMPI), a hybrid deep learning model that can characterize both the native sequences of promoters and the morphological outline of promoters at the same time. We developed the HMPI to combine a method called the PSFN (promoter sequence features network), which characterizes native promoter sequences and deduces sequence features, with a technique referred to as the DSPN (deep structural profiles network), which is specially structured to model the promoters in terms of their structural profile and to deduce their structural attributes. RESULTS The HMPI was applied to human, plant and Escherichia coli K-12 strain datasets, and the findings showed that the HMPI was successful at extracting the features of the promoter while greatly enhancing the promoter identification performance. In addition, after the improvements of synthetic sampling, transfer learning and label smoothing regularization, the improved HMPI models achieved good results in identifying subtypes of promoters on prokaryotic promoter datasets. CONCLUSIONS The results showed that the HMPI was successful at extracting the features of promoters while greatly enhancing the performance of identifying promoters on both eukaryotic and prokaryotic datasets, and the improved HMPI models are good at identifying subtypes of promoters on prokaryotic promoter datasets. The HMPI is additionally adaptable to different biological functional sequences, allowing for the addition of new features or models.
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Affiliation(s)
- Ying Wang
- Systems Engineering Institute, Xi'an Jiaotong University, Xi'an, China
| | - Qinke Peng
- Systems Engineering Institute, Xi'an Jiaotong University, Xi'an, China.
| | - Xu Mou
- Systems Engineering Institute, Xi'an Jiaotong University, Xi'an, China
| | - Xinyuan Wang
- Systems Engineering Institute, Xi'an Jiaotong University, Xi'an, China
| | - Haozhou Li
- Systems Engineering Institute, Xi'an Jiaotong University, Xi'an, China
| | - Tian Han
- Systems Engineering Institute, Xi'an Jiaotong University, Xi'an, China
| | - Zhao Sun
- Systems Engineering Institute, Xi'an Jiaotong University, Xi'an, China
| | - Xiao Wang
- Systems Engineering Institute, Xi'an Jiaotong University, Xi'an, China
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15
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Chakraborty S, Chaudhuri D, Chaudhuri D, Singh V, Banerjee S, Chowdhury D, Haldar S. Connecting conformational stiffness of the protein with energy landscape by a single experiment. NANOSCALE 2022; 14:7659-7673. [PMID: 35546109 DOI: 10.1039/d1nr07582a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The structure-function dynamics of a protein as a flexible polymer is essential to describe its biological functions. Here, using single-molecule magnetic tweezers, we have studied the effect of ionic strength on the folding mechanics of protein L, and probed its folding-associated physical properties by re-measuring the same protein in a range of ammonium sulfate concentrations from 150 mM to 650 mM. We observed an electrolyte-dependent conformational dynamics and folding landscape of the protein in a single experiment. Salt increases the refolding kinetics, while decreasing the unfolding kinetics under force, which in turn modifies the barrier heights towards the folded state. Additionally, salt enhances the molecular compaction by decreasing the Kuhn length of the protein polymer from 1.18 nm to 0.58 nm, which we have explained by modifying the freely jointed chain model. Finally, we correlated polymer chain physics to the folding dynamics, and thus provided an analytical framework for understanding compaction-induced folding mechanics across a range of ionic strengths from a single experiment.
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Affiliation(s)
- Soham Chakraborty
- Department of Biological Sciences, Ashoka University, Sonepat, Haryana 131029, India.
| | - Deep Chaudhuri
- Department of Biological Sciences, Ashoka University, Sonepat, Haryana 131029, India.
| | - Dyuti Chaudhuri
- Department of Biological Sciences, Ashoka University, Sonepat, Haryana 131029, India.
| | - Vihan Singh
- Department of Biological Sciences, Ashoka University, Sonepat, Haryana 131029, India.
| | - Souradeep Banerjee
- Department of Biological Sciences, Ashoka University, Sonepat, Haryana 131029, India.
| | - Debojyoti Chowdhury
- Department of Biological Sciences, Ashoka University, Sonepat, Haryana 131029, India.
| | - Shubhasis Haldar
- Department of Biological Sciences, Ashoka University, Sonepat, Haryana 131029, India.
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16
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Boiero Sanders M, Toret CP, Guillotin A, Antkowiak A, Vannier T, Robinson RC, Michelot A. Specialization of actin isoforms derived from the loss of key interactions with regulatory factors. EMBO J 2022; 41:e107982. [PMID: 35178724 PMCID: PMC8886540 DOI: 10.15252/embj.2021107982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 01/19/2022] [Accepted: 01/21/2022] [Indexed: 11/09/2022] Open
Abstract
A paradox of eukaryotic cells is that while some species assemble a complex actin cytoskeleton from a single ortholog, other species utilize a greater diversity of actin isoforms. The physiological consequences of using different actin isoforms, and the molecular mechanisms by which highly conserved actin isoforms are segregated into distinct networks, are poorly known. Here, we sought to understand how a simple biological system, composed of a unique actin and a limited set of actin‐binding proteins, reacts to a switch to heterologous actin expression. Using yeast as a model system and biomimetic assays, we show that such perturbation causes drastic reorganization of the actin cytoskeleton. Our results indicate that defective interaction of a heterologous actin for important regulators of actin assembly limits certain actin assembly pathways while reinforcing others. Expression of two heterologous actin variants, each specialized in assembling a different network, rescues cytoskeletal organization and confers resistance to external perturbation. Hence, while species using a unique actin have homeostatic actin networks, actin assembly pathways in species using several actin isoforms may act more independently.
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Affiliation(s)
| | - Christopher P Toret
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Audrey Guillotin
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Adrien Antkowiak
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Thomas Vannier
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Robert C Robinson
- Research Institute for Interdisciplinary Science (RIIS), Okayama University, Okayama, Japan.,School of Biomolecular Science and Engineering (BSE), Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong, Thailand
| | - Alphée Michelot
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
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17
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Park J, Kravchuk P, Krishnaprasad A, Roy T, Kang EH. Graphene Enhances Actin Filament Assembly Kinetics and Modulates NIH-3T3 Fibroblast Cell Spreading. Int J Mol Sci 2022; 23:509. [PMID: 35008935 PMCID: PMC8745492 DOI: 10.3390/ijms23010509] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/28/2021] [Accepted: 12/30/2021] [Indexed: 01/01/2023] Open
Abstract
Actin plays critical roles in various cellular functions, including cell morphogenesis, differentiation, and movement. The assembly of actin monomers into double-helical filaments is regulated in surrounding microenvironments. Graphene is an attractive nanomaterial that has been used in various biomaterial applications, such as drug delivery cargo and scaffold for cells, due to its unique physical and chemical properties. Although several studies have shown the potential effects of graphene on actin at the cellular level, the direct influence of graphene on actin filament dynamics has not been studied. Here, we investigate the effects of graphene on actin assembly kinetics using spectroscopy and total internal reflection fluorescence microscopy. We demonstrate that graphene enhances the rates of actin filament growth in a concentration-dependent manner. Furthermore, cell morphology and spreading are modulated in mouse embryo fibroblast NIH-3T3 cultured on a graphene surface without significantly affecting cell viability. Taken together, these results suggest that graphene may have a direct impact on actin cytoskeleton remodeling.
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Affiliation(s)
- Jinho Park
- NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA; (J.P.); (P.K.); (A.K.); (T.R.)
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32816, USA
| | - Pavlo Kravchuk
- NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA; (J.P.); (P.K.); (A.K.); (T.R.)
| | - Adithi Krishnaprasad
- NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA; (J.P.); (P.K.); (A.K.); (T.R.)
- Department of Electrical and Computer Engineering, University of Central Florida, Orlando, FL 32816, USA
| | - Tania Roy
- NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA; (J.P.); (P.K.); (A.K.); (T.R.)
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32816, USA
- Department of Electrical and Computer Engineering, University of Central Florida, Orlando, FL 32816, USA
| | - Ellen Hyeran Kang
- NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA; (J.P.); (P.K.); (A.K.); (T.R.)
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32816, USA
- Department of Physics, University of Central Florida, Orlando, FL 32816, USA
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18
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Sahoo S, Maiti I, Laha A, De R, Maiti S, De P. Cholate Conjugated Cationic Polymers for Regulation of Actin Dynamics. J Mater Chem B 2022; 10:8033-8045. [DOI: 10.1039/d2tb01364a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cytoskeletal movement is a compulsory necessity for proper cell functioning and is largely controlled by actin filament dynamics. The actin dynamics can be finetuned by various natural and artificial materials...
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19
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Castaneda N, Feuillie C, Molinari M, Kang EH. Actin Bundle Nanomechanics and Organization Are Modulated by Macromolecular Crowding and Electrostatic Interactions. Front Mol Biosci 2021; 8:760950. [PMID: 34901154 PMCID: PMC8662701 DOI: 10.3389/fmolb.2021.760950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 11/02/2021] [Indexed: 11/21/2022] Open
Abstract
The structural and mechanical properties of actin bundles are essential to eukaryotic cells, aiding in cell motility and mechanical support of the plasma membrane. Bundle formation occurs in crowded intracellular environments composed of various ions and macromolecules. Although the roles of cations and macromolecular crowding in the mechanics and organization of actin bundles have been independently established, how changing both intracellular environmental conditions influence bundle mechanics at the nanoscale has yet to be established. Here we investigate how electrostatics and depletion interactions modulate the relative Young’s modulus and height of actin bundles using atomic force microscopy. Our results demonstrate that cation- and depletion-induced bundles display an overall reduction of relative Young’s modulus depending on either cation or crowding concentrations. Furthermore, we directly measure changes to cation- and depletion-induced bundle height, indicating that bundles experience alterations to filament packing supporting the reduction to relative Young’s modulus. Taken together, our work suggests that electrostatic and depletion interactions may act counteractively, impacting actin bundle nanomechanics and organization.
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Affiliation(s)
- Nicholas Castaneda
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States.,Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, United States
| | - Cecile Feuillie
- Institute of Chemistry and Biology of Membranes and Nano-objects, CBMN CNRS UMR 5248, IPB, Université de Bordeaux, Pessac, France
| | - Michael Molinari
- Institute of Chemistry and Biology of Membranes and Nano-objects, CBMN CNRS UMR 5248, IPB, Université de Bordeaux, Pessac, France
| | - Ellen Hyeran Kang
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States.,Department of Physics, University of Central Florida, Orlando, FL, United States.,Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, United States
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20
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Jacobi A, Ariza de Schellenberger A, Uca YO, Herbig M, Guck J, Sack I. Real-Time Deformability Cytometry Detects Leukocyte Stiffening After Gadolinium-Based Contrast Agent Exposure. Invest Radiol 2021; 56:837-844. [PMID: 34038063 DOI: 10.1097/rli.0000000000000794] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES Reports on gadolinium (Gd) retention in soft tissues after administration of Gd-based contrast agents (GBCAs) raise concerns about Gd-induced changes in the biophysical properties of cells and tissues. Here, we investigate if clinical GBCAs of both classes of linear and macrocyclic structure cause changes in the mechanical properties of leukocytes in human blood samples. MATERIAL AND METHODS Real-time deformability cytometry was applied to human blood samples from 6 donors. The samples were treated with 1 mM gadoteric acid (Dotarem), gadopentetic acid (Magnevist), gadobutrol (Gadovist), or Gd trichloride at 37°C for 1 hour to mimic clinical doses of GBCAs and exposure times. Leukocyte subtypes-lymphocytes, monocytes, and neutrophils-were identified based on their size and brightness and analyzed for deformability, which is inversely correlated with cellular stiffness. RESULTS We observed significant stiffening (3%-13%, P < 0.01) of all investigated leukocyte subtypes, which was most pronounced for lymphocytes, followed by neutrophils and monocytes, and the effects were independent of the charge and steric structure of the GBCA applied. In contrast, no changes in cell size and brightness were observed, suggesting that deformability and cell stiffness measured by real-time deformability cytometry are sensitive to changes in the physical phenotypes of leukocytes after GBCA exposure. CONCLUSIONS Real-time deformability cytometry might provide a quantitative blood marker for critical changes in the physical properties of blood cells in patients undergoing GBCA-enhanced magnetic resonance imaging.
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Affiliation(s)
| | - Angela Ariza de Schellenberger
- Department of Radiology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin
| | - Yavuz Oguz Uca
- Department of Radiology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin
| | | | - Jochen Guck
- From the Max Planck Institute for the Science of Light & Max-Planck-Zentrum für Physik und Medizin, Erlangen
| | - Ingolf Sack
- Department of Radiology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Berlin
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21
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Castaneda N, Park J, Kang EH. Regulation of Actin Bundle Mechanics and Structure by Intracellular Environmental Factors. FRONTIERS IN PHYSICS 2021; 9:675885. [PMID: 34422787 PMCID: PMC8376200 DOI: 10.3389/fphy.2021.675885] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The mechanical and structural properties of actin cytoskeleton drive various cellular processes, including structural support of the plasma membrane and cellular motility. Actin monomers assemble into double-stranded helical filaments as well as higher-ordered structures such as bundles and networks. Cells incorporate macromolecular crowding, cation interactions, and actin-crosslinking proteins to regulate the organization of actin bundles. Although the roles of each of these factors in actin bundling have been well-known individually, how combined factors contribute to actin bundle assembly, organization, and mechanics is not fully understood. Here, we describe recent studies that have investigated the mechanisms of how intracellular environmental factors influence actin bundling. This review highlights the effects of macromolecular crowding, cation interactions, and actin-crosslinking proteins on actin bundle organization, structure, and mechanics. Understanding these mechanisms is important in determining in vivo actin biophysics and providing insights into cell physiology.
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Affiliation(s)
- Nicholas Castaneda
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, United States
| | - Jinho Park
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, United States
| | - Ellen Hyeran Kang
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, United States
- Department of Physics, University of Central Florida, Orlando, FL, United States
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22
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Gruszczynska-Biegala J, Stefan A, Kasprzak AA, Dobryszycki P, Khaitlina S, Strzelecka-Gołaszewska H. Myopathy-Sensitive G-Actin Segment 227-235 Is Involved in Salt-Induced Stabilization of Contacts within the Actin Filament. Int J Mol Sci 2021; 22:ijms22052327. [PMID: 33652657 PMCID: PMC7956362 DOI: 10.3390/ijms22052327] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 02/16/2021] [Accepted: 02/21/2021] [Indexed: 01/09/2023] Open
Abstract
Formation of stable actin filaments, critically important for actin functions, is determined by the ionic strength of the solution. However, not much is known about the elements of the actin fold involved in ionic-strength-dependent filament stabilization. In this work, F-actin was destabilized by Cu2+ binding to Cys374, and the effects of solvent conditions on the dynamic properties of F-actin were correlated with the involvement of Segment 227-235 in filament stabilization. The results of our work show that the presence of Mg2+ at the high-affinity cation binding site of Cu-modified actin polymerized with MgCl2 strongly enhances the rate of filament subunit exchange and promotes the filament instability. In the presence of 0.1 M KCl, the filament subunit exchange was 2-3-fold lower than that in the MgCl2-polymerized F-actin. This effect correlates with the reduced accessibility of the D-loop and Segment 227-235 on opposite filament strands, consistent with an ionic-strength-dependent conformational change that modulates involvement of Segment 227-235 in stabilization of the intermonomer interface. KCl may restrict the mobility of the α-helix encompassing part of Segment 227-235 and/or be bound to Asp236 at the boundary of Segment 227-235. These results provide experimental evidence for the involvement of Segment 227-235 in salt-induced stabilization of contacts within the actin filament and suggest that they can be weakened by mutations characteristic of actin-associated myopathies.
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Affiliation(s)
- Joanna Gruszczynska-Biegala
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland; (J.G.-B.); (A.S.); (A.A.K.); (H.S.-G.)
- Molecular Biology Unit, Mossakowski Medical Research Institute Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Andrzej Stefan
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland; (J.G.-B.); (A.S.); (A.A.K.); (H.S.-G.)
| | - Andrzej A. Kasprzak
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland; (J.G.-B.); (A.S.); (A.A.K.); (H.S.-G.)
| | - Piotr Dobryszycki
- Faculty of Chemistry, Wrocław University of Technology, 50-370 Wroclaw, Poland;
| | - Sofia Khaitlina
- Laboratory of Cytology of Unicellular Organisms, Institute of Cytology, Russian Academy of Sciences, 194064 St. Petersburg, Russia
- Correspondence:
| | - Hanna Strzelecka-Gołaszewska
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland; (J.G.-B.); (A.S.); (A.A.K.); (H.S.-G.)
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23
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Heidings JB, Demosthene B, Merlino TR, Castaneda N, Kang EH. Gelsolin-mediated actin filament severing in crowded environments. Biochem Biophys Res Commun 2020; 532:548-554. [PMID: 32900483 DOI: 10.1016/j.bbrc.2020.08.041] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 08/15/2020] [Indexed: 10/24/2022]
Abstract
Gelsolin is a calcium-regulated actin binding protein that severs and caps actin filaments. Gelsolin's severing activity is important for regulating actin filament assembly dynamics that are required for cell motility as well as survival. The majority of in vitro studies of gelsolin have been performed in dilute buffer conditions which do not simulate the molecular interactions occurring in the crowded intracellular environment. We hypothesize that crowding results in greater gelsolin severing activity due to induced conformational changes in actin filaments and/or gelsolin. In this study, we evaluated the effects of crowding on gelsolin-mediated actin filament severing and gelsolin binding to actin filaments in crowded solutions, utilizing total internal reflection fluorescence (TIRF) microscopy and co-sedimentation assays. Our data indicates that the presence of crowders causes a decrease in the rate of gelsolin severing as well as a decrease in the amount of gelsolin bound to actin filaments, with greater effects caused by the polymeric crowder. Despite the severing rate decrease, gelsolin-mediated filament severing is increased in the presence of crowders. Understanding the crowding effect on gelsolin-mediated actin filament severing offers insight into the interactions between gelsolin and actin that occur inside the crowded cytoplasm.
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Affiliation(s)
- James B Heidings
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32816, USA; NanoScience Technology Center, University of Central Florida, Orlando, FL, 32826, USA
| | - Bryan Demosthene
- NanoScience Technology Center, University of Central Florida, Orlando, FL, 32826, USA
| | - Theresa R Merlino
- NanoScience Technology Center, University of Central Florida, Orlando, FL, 32826, USA
| | - Nicholas Castaneda
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32816, USA; NanoScience Technology Center, University of Central Florida, Orlando, FL, 32826, USA
| | - Ellen H Kang
- NanoScience Technology Center, University of Central Florida, Orlando, FL, 32826, USA; Department of Physics, University of Central Florida, Orlando, FL, 32816, USA; Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, 32816, USA.
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24
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Xu XP, Pokutta S, Torres M, Swift MF, Hanein D, Volkmann N, Weis WI. Structural basis of αE-catenin-F-actin catch bond behavior. eLife 2020; 9:e60878. [PMID: 32915141 PMCID: PMC7588230 DOI: 10.7554/elife.60878] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 09/09/2020] [Indexed: 11/13/2022] Open
Abstract
Cell-cell and cell-matrix junctions transmit mechanical forces during tissue morphogenesis and homeostasis. α-Catenin links cell-cell adhesion complexes to the actin cytoskeleton, and mechanical load strengthens its binding to F-actin in a direction-sensitive manner. Specifically, optical trap experiments revealed that force promotes a transition between weak and strong actin-bound states. Here, we describe the cryo-electron microscopy structure of the F-actin-bound αE-catenin actin-binding domain, which in solution forms a five-helix bundle. In the actin-bound structure, the first helix of the bundle dissociates and the remaining four helices and connecting loops rearrange to form the interface with actin. Deletion of the first helix produces strong actin binding in the absence of force, suggesting that the actin-bound structure corresponds to the strong state. Our analysis explains how mechanical force applied to αE-catenin or its homolog vinculin favors the strongly bound state, and the dependence of catch bond strength on the direction of applied force.
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Affiliation(s)
| | - Sabine Pokutta
- Departments of Structural Biology and Molecular & Cellular Physiology, Stanford University School of MedicineStanfordUnited States
| | - Megan Torres
- Departments of Structural Biology and Molecular & Cellular Physiology, Stanford University School of MedicineStanfordUnited States
| | | | - Dorit Hanein
- Scintillon InstituteSan DiegoUnited States
- Department of Structural Biology and Chemistry, Pasteur InstituteParisFrance
| | - Niels Volkmann
- Scintillon InstituteSan DiegoUnited States
- Department of Structural Biology and Chemistry, Pasteur InstituteParisFrance
| | - William I Weis
- Departments of Structural Biology and Molecular & Cellular Physiology, Stanford University School of MedicineStanfordUnited States
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25
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Janco M, Dedova I, Bryce NS, Hardeman EC, Gunning PW. Visualizing the in vitro assembly of tropomyosin/actin filaments using TIRF microscopy. Biophys Rev 2020; 12:879-885. [PMID: 32638329 PMCID: PMC7429660 DOI: 10.1007/s12551-020-00720-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 07/02/2020] [Indexed: 12/23/2022] Open
Abstract
Tropomyosins are elongated alpha-helical proteins that form co-polymers with most actin filaments within a cell and play important roles in the structural and functional diversification of the actin cytoskeleton. How the assembly of tropomyosins along an actin filament is regulated and the kinetics of tropomyosin association with an actin filament is yet to be fully determined. A recent series of publications have used total internal reflection fluorescence (TIRF) microscopy in combination with advanced surface and protein chemistry to visualise the molecular assembly of actin/tropomyosin filaments in vitro. Here, we review the use of the in vitro TIRF assay in the determination of kinetic data on tropomyosin filament assembly. This sophisticated approach has enabled generation of real-time single-molecule data to fill the gap between in vitro bulk assays and in vivo assays of tropomyosin function. The in vitro TIRF assays provide a new foundation for future studies involving multiple actin-binding proteins that will more accurately reflect the physiological protein-protein interactions in cells.
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Affiliation(s)
- Miro Janco
- School of Medical Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Irina Dedova
- School of Medical Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Nicole S Bryce
- School of Medical Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Edna C Hardeman
- School of Medical Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Peter W Gunning
- School of Medical Sciences, University of New South Wales, Sydney, NSW, 2052, Australia.
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26
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Horan BG, Hall AR, Vavylonis D. Insights into Actin Polymerization and Nucleation Using a Coarse-Grained Model. Biophys J 2020; 119:553-566. [PMID: 32668234 DOI: 10.1016/j.bpj.2020.06.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 06/17/2020] [Accepted: 06/19/2020] [Indexed: 12/20/2022] Open
Abstract
We studied actin filament polymerization and nucleation with molecular dynamics simulations and a previously established coarse-grained model having each residue represented by a single interaction site located at the Cα atom. We approximate each actin protein as a fully or partially rigid unit to identify the equilibrium structural ensemble of interprotein complexes. Monomers in the F-actin configuration bound to both barbed and pointed ends of a short F-actin filament at the anticipated locations for polymerization. Binding at both ends occurred with similar affinity. Contacts between residues of the incoming subunit and the short filament were consistent with expectation from models based on crystallography, x-ray diffraction, and cryo-electron microscopy. Binding at the barbed and pointed end also occurred at an angle with respect to the polymerizable bound structure, and the angle range depended on the flexibility of the D-loop. Additional barbed end bound states were seen when the incoming subunit was in the G-actin form. Consistent with an activation barrier for pointed end polymerization, G-actin did not bind at an F-actin pointed end. In all cases, binding at the barbed end also occurred in a configuration similar to the antiparallel (lower) dimer. Individual monomers bound each other in a short-pitch helix complex in addition to other configurations, with several of them apparently nonproductive for polymerization. Simulations with multiple monomers in the F-actin form show assembly into filaments as well as transient aggregates at the barbed end. We discuss the implications of these observations on the kinetic pathway of actin filament nucleation and polymerization and possibilities for future improvements of the coarse-grained model.
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Affiliation(s)
- Brandon G Horan
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania
| | - Aaron R Hall
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania
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27
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How Actin Tracks Affect Myosin Motors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1239:183-197. [DOI: 10.1007/978-3-030-38062-5_9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
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28
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The many implications of actin filament helicity. Semin Cell Dev Biol 2019; 102:65-72. [PMID: 31862222 DOI: 10.1016/j.semcdb.2019.10.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 10/15/2019] [Accepted: 10/31/2019] [Indexed: 12/17/2022]
Abstract
One of the best known features of actin filaments is their helical structure. A number of essential properties emerge from this molecular arrangement of actin subunits. Here, we give an overview of the mechanical and biochemical implications of filament helicity, at different scales. In particular, a number of recent studies have highlighted the role of filament helicity in the adaptation to and the generation of mechanical torsion, and in the modulation of the filament's interaction with very different actin-binding proteins (such as myosins, cross-linkers, formins, and cofilin). Helicity can thus be seen as a key factor for the regulation of actin assembly, and as a link between biochemical regulators and their mechanical context. In addition, actin filament helicity appears to play an essential role in the establishment of chirality at larger scales, up to the organismal scale. Altogether, helicity appears to be an essential feature contributing to the regulation of actin assembly dynamics, and to actin's ability to organize cells at a larger scale.
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29
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Merino F, Pospich S, Raunser S. Towards a structural understanding of the remodeling of the actin cytoskeleton. Semin Cell Dev Biol 2019; 102:51-64. [PMID: 31836290 PMCID: PMC7221352 DOI: 10.1016/j.semcdb.2019.11.018] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 11/27/2019] [Accepted: 11/28/2019] [Indexed: 12/03/2022]
Abstract
Actin filaments (F-actin) are a key component of eukaryotic cells. Whether serving as a scaffold for myosin or using their polymerization to push onto cellular components, their function is always related to force generation. To control and fine-tune force production, cells have a large array of actin-binding proteins (ABPs) dedicated to control every aspect of actin polymerization, filament localization, and their overall mechanical properties. Although great advances have been made in our biochemical understanding of the remodeling of the actin cytoskeleton, the structural basis of this process is still being deciphered. In this review, we summarize our current understanding of this process. We outline how ABPs control the nucleation and disassembly, and how these processes are affected by the nucleotide state of the filaments. In addition, we highlight recent advances in the understanding of actomyosin force generation, and describe recent advances brought forward by the developments of electron cryomicroscopy.
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Affiliation(s)
- Felipe Merino
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Sabrina Pospich
- Department of Structural Biochemistry, 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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30
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Mechanical stiffness of reconstituted actin patches correlates tightly with endocytosis efficiency. PLoS Biol 2019; 17:e3000500. [PMID: 31652255 PMCID: PMC6834286 DOI: 10.1371/journal.pbio.3000500] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 11/06/2019] [Accepted: 10/18/2019] [Indexed: 01/16/2023] Open
Abstract
Clathrin-mediated endocytosis involves the sequential assembly of more than 60 proteins at the plasma membrane. An important fraction of these proteins regulates the assembly of an actin-related protein 2/3 (Arp2/3)-branched actin network, which is essential to generate the force during membrane invagination. We performed, on wild-type (WT) yeast and mutant strains lacking putative actin crosslinkers, a side-by-side comparison of in vivo endocytic phenotypes and in vitro rigidity measurements of reconstituted actin patches. We found a clear correlation between softer actin networks and a decreased efficiency of endocytosis. Our observations support a chain-of-consequences model in which loss of actin crosslinking softens Arp2/3-branched actin networks, directly limiting the transmission of the force. Additionally, the lifetime of failed endocytic patches increases, leading to a larger number of patches and a reduced pool of polymerizable actin, which slows down actin assembly and further impairs endocytosis. This study uses in vitro reconstitution of endocytic actin patches and mechanical measurements with chains of superparamagnetic microbeads to reveal a tight correlation between the stiffness of actin networks and the efficiency of endocytosis in yeast.
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31
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Castaneda N, Lee M, Rivera-Jacquez HJ, Marracino RR, Merlino TR, Kang H. Actin Filament Mechanics and Structure in Crowded Environments. J Phys Chem B 2019; 123:2770-2779. [PMID: 30817154 DOI: 10.1021/acs.jpcb.8b12320] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The cellular environment is crowded with high concentrations of macromolecules that significantly reduce accessible volume for biomolecular interactions. Reductions in cellular volume can generate depletion forces that affect protein assembly and stability. The mechanical and structural properties of actin filaments play critical roles in various cellular functions, including structural support, cell movement, division, and intracellular transport. Although the effects of molecular crowding on actin polymerization have been shown, how crowded environments affect filament mechanics and structure is unknown. In this study, we investigate the effects of solution crowding on the modulations of actin filament bending stiffness and conformations both in vitro and in silico. Direct visualization of thermally fluctuating filaments in the presence of crowding agents is achieved by fluorescence microscopy imaging. Biophysical analysis indicates that molecular crowding enhances filament's effective bending stiffness and reduces average filament lengths. Utilizing the all-atom molecular dynamics simulations, we demonstrate that molecular crowding alters filament conformations and intersubunit contacts that are directly coupled to the mechanical properties of filaments. Taken together, our study suggests that the interplay between excluded volume effects and nonspecific interactions raised from molecular crowding may modulate actin filament mechanics and structure.
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Affiliation(s)
- Nicholas Castaneda
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States.,Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida 32827 , United States
| | - Myeongsang Lee
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Hector J Rivera-Jacquez
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Ryan R Marracino
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States.,Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida 32827 , United States
| | - Theresa R Merlino
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Hyeran Kang
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
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32
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Wioland H, Jegou A, Romet-Lemonne G. Quantitative Variations with pH of Actin Depolymerizing Factor/Cofilin's Multiple Actions on Actin Filaments. Biochemistry 2018; 58:40-47. [PMID: 30499293 PMCID: PMC6358128 DOI: 10.1021/acs.biochem.8b01001] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
![]()
Actin
depolymerizing factor (ADF)/cofilin is the main protein family
promoting the disassembly of actin filaments, which is essential for
numerous cellular functions. ADF/cofilin proteins disassemble actin
filaments through different reactions, as they bind to their sides,
sever them, and promote the depolymerization of the resulting ADF/cofilin-saturated
filaments. Moreover, the efficiency of ADF/cofilin is known to be
very sensitive to pH. ADF/cofilin thus illustrates two challenges
in actin biochemistry: separating the different regulatory actions
of a single protein and characterizing them as a function of specific
biochemical conditions. Here, we investigate the different reactions
of ADF/cofilin on actin filaments, at four different pH values ranging
from 6.6 to 7.8, using single-filament microfluidics techniques. We
show that decreasing the pH decreases the effective filament severing
rate by increasing the rate at which filaments become saturated by
ADF/cofilin, thereby reducing the number of ADF/cofilin domain boundaries,
where severing can occur. The severing rate per domain boundary, however,
remains unchanged at different pH values. The ADF/cofilin-decorated
filaments (“cofilactin” filaments) depolymerize from
both ends. We show here that, at physiological pH (7.0–7.4),
the pointed end depolymerization of cofilactin filaments is barely
faster than that of bare filaments. In contrast, cofilactin barbed
ends undergo an “unstoppable” depolymerization (depolymerizing
for minutes despite the presence of free actin monomers and capping
protein in solution), throughout our pH range. We thus show that,
at physiological pH, the main contribution of ADF/cofilin to filament
depolymerization is at the barbed end.
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Affiliation(s)
- Hugo Wioland
- Institut Jacques Monod, CNRS, Université Paris-Diderot , 75013 Paris , France
| | - Antoine Jegou
- Institut Jacques Monod, CNRS, Université Paris-Diderot , 75013 Paris , France
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33
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Kobayashi M, Ramirez BE, Warren CM. Interplay of actin, ADP and Mg 2+ interactions with striated muscle myosin: Implications of their roles in ATPase. Arch Biochem Biophys 2018; 662:101-110. [PMID: 30529103 DOI: 10.1016/j.abb.2018.12.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 11/25/2018] [Accepted: 12/03/2018] [Indexed: 12/15/2022]
Abstract
The effects of Mg2+ on the interaction between ADP, a product of the ATPase reaction, and striated muscle myosin-subfragment 1 (S1) were investigated with both functional and spectroscopic methods. Mg2+ inhibited striated muscle myosin ATPase in the presence of F-actin. Significant effects of Mg2+ were observed in both rate constants of NOE build-up and maximal intensities in WaterLOGSY NMR experiments as F-actin concentration increased. In the absence of F-actin, myosin S1 with Mg2+ bound to a fluorescent ADP analog about five-times tighter than without Mg2+. In the presence of F-actin, the affinity of myosin S1 toward the ADP analog significantly decreased both with and without Mg2+. The equilibrium titration of myosin-S1 into F-actin revealed that in the presence of ADP the apparent dissociation constant (Kd) without Mg2+ was more than five-fold smaller than with Mg2+. Further, we examined effects of F-actin, ADP and Mg2+ binding to myosin on the tertiary structure of myosin-S1 using near UV circular dichroism (CD) spectroscopy. Both in the presence and absence of ADP, there was a Mg2+-dependent difference in the near UV CD spectra of actomyosin. Our results show that Mg2+ affects myosin-ADP and actin-myosin interactions which may be reflected in myosin ATPase activity.
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Affiliation(s)
- Minae Kobayashi
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, USA; Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, IL, USA.
| | - Benjamin E Ramirez
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA
| | - Chad M Warren
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, USA; Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, IL, USA
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34
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Aydin F, Katkar HH, Voth GA. Multiscale simulation of actin filaments and actin-associated proteins. Biophys Rev 2018; 10:1521-1535. [PMID: 30382557 PMCID: PMC6297090 DOI: 10.1007/s12551-018-0474-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 10/21/2018] [Indexed: 02/04/2023] Open
Abstract
Actin is an important cytoskeletal protein that serves as a building block to form filament networks that span across the cell. These networks are orchestrated by a myriad of other cytoskeletal entities including the unbranched filament-forming protein formin and branched network-forming protein complex Arp2/3. Computational models have been able to provide insights into many important structural transitions that are involved in forming these networks, and into the nature of interactions essential for actin filament formation and for regulating the behavior of actin-associated proteins. In this review, we summarize a subset of such models that focus on the atomistic features and those that can integrate atomistic features into a larger picture in a multiscale fashion.
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Affiliation(s)
- Fikret Aydin
- Department of Chemistry, Institute of Biophysical Dynamics, and James Frank Institute, University of Chicago, Chicago, IL, USA
| | - Harshwardhan H Katkar
- Department of Chemistry, Institute of Biophysical Dynamics, and James Frank Institute, University of Chicago, Chicago, IL, USA
| | - Gregory A Voth
- Department of Chemistry, Institute of Biophysical Dynamics, and James Frank Institute, University of Chicago, Chicago, IL, USA.
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35
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Katkar HH, Davtyan A, Durumeric AEP, Hocky GM, Schramm AC, De La Cruz EM, Voth GA. Insights into the Cooperative Nature of ATP Hydrolysis in Actin Filaments. Biophys J 2018; 115:1589-1602. [PMID: 30249402 PMCID: PMC6260209 DOI: 10.1016/j.bpj.2018.08.034] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 08/21/2018] [Accepted: 08/22/2018] [Indexed: 12/11/2022] Open
Abstract
Actin filaments continually assemble and disassemble within a cell. Assembled filaments "age" as a bound nucleotide ATP within each actin subunit quickly hydrolyzes followed by a slower release of the phosphate Pi, leaving behind a bound ADP. This subtle change in nucleotide state of actin subunits affects filament rigidity as well as its interactions with binding partners. We present here a systematic multiscale ultra-coarse-graining approach that provides a computationally efficient way to simulate a long actin filament undergoing ATP hydrolysis and phosphate-release reactions while systematically taking into account available atomistic details. The slower conformational changes and their dependence on the chemical reactions are simulated with the ultra-coarse-graining model by assigning internal states to the coarse-grained sites. Each state is represented by a unique potential surface of a local heterogeneous elastic network. Internal states undergo stochastic transitions that are coupled to conformations of the underlying molecular system. The model reproduces mechanical properties of the filament and allows us to study whether conformational fluctuations in actin subunits produce cooperative filament aging. We find that the nucleotide states of neighboring subunits modulate the reaction kinetics, implying cooperativity in ATP hydrolysis and Pi release. We further systematically coarse grain the system into a Markov state model that incorporates assembly and disassembly, facilitating a direct comparison with previously published models. We find that cooperativity in ATP hydrolysis and Pi release significantly affects the filament growth dynamics only near the critical G-actin concentration, whereas far from it, both cooperative and random mechanisms show similar growth dynamics. In contrast, filament composition in terms of the bound nucleotide distribution varies significantly at all monomer concentrations studied. These results provide new insights, to our knowledge, into the cooperative nature of ATP hydrolysis and Pi release and the implications it has for actin filament properties, providing novel predictions for future experimental studies.
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Affiliation(s)
- Harshwardhan H Katkar
- Department of Chemistry, Institute for Biophysical Dynamics and James Frank Institute, University of Chicago, Chicago, Illinois
| | - Aram Davtyan
- Department of Chemistry, Institute for Biophysical Dynamics and James Frank Institute, University of Chicago, Chicago, Illinois
| | - Aleksander E P Durumeric
- Department of Chemistry, Institute for Biophysical Dynamics and James Frank Institute, University of Chicago, Chicago, Illinois
| | - Glen M Hocky
- Department of Chemistry, Institute for Biophysical Dynamics and James Frank Institute, University of Chicago, Chicago, Illinois
| | - Anthony C Schramm
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Enrique M De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Gregory A Voth
- Department of Chemistry, Institute for Biophysical Dynamics and James Frank Institute, University of Chicago, Chicago, Illinois.
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36
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Structural evidence for the roles of divalent cations in actin polymerization and activation of ATP hydrolysis. Proc Natl Acad Sci U S A 2018; 115:10345-10350. [PMID: 30254171 PMCID: PMC6187199 DOI: 10.1073/pnas.1806394115] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Actin polymerization is a divalent cation-dependent process. Here we identify a cation binding site on the surface of actin in a 2.0-Å resolution X-ray structure of actin and find evidence of three additional sites in published high-resolution structures. These cations are stable in molecular dynamics (MD) simulations of the filament, suggesting a functional role in polymerization or filament rigidity. Polymerization activates the ATPase activity of the incorporating actin protomers. Careful analysis of water molecules that approach the ATP in the MD simulations revealed Gln137-activated water to be in a suitable position in F-actin, to initiate attack for ATP hydrolysis, and its occupancy was dependent on bound cations. The structure of the actin filament is known at a resolution that has allowed the architecture of protein components to be unambiguously assigned. However, fully understanding the chemistry of the system requires higher resolution to identify the ions and water molecules involved in polymerization and ATP hydrolysis. Here, we find experimental evidence for the association of cations with the surfaces of G-actin in a 2.0-Å resolution X-ray structure of actin bound to a Cordon-Bleu WH2 motif and in previously determined high-resolution X-ray structures. Three of four reoccurring divalent cation sites were stable during molecular dynamics (MD) simulations of the filament, suggesting that these sites may play a functional role in stabilizing the filament. We modeled the water coordination at the ATP-bound Mg2+, which also proved to be stable during the MD simulations. Using this model of the filament with a hydrated ATP-bound Mg2+, we compared the cumulative probability of an activated hydrolytic water molecule approaching the γ-phosphorous of ATP, in comparison with G-actin, in the MD simulations. The cumulative probability increased in F-actin in line with the activation of actin’s ATPase activity on polymerization. However, inclusion of the cations in the filament lowered cumulative probability, suggesting the rate of hydrolysis may be linked to filament flexibility. Together, these data extend the possible roles of Mg2+ in polymerization and the mechanism of polymerization-induced activation of actin’s ATPase activity.
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37
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Castaneda N, Zheng T, Rivera-Jacquez HJ, Lee HJ, Hyun J, Balaeff A, Huo Q, Kang H. Cations Modulate Actin Bundle Mechanics, Assembly Dynamics, and Structure. J Phys Chem B 2018; 122:3826-3835. [PMID: 29608304 DOI: 10.1021/acs.jpcb.8b00663] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Actin bundles are key factors in the mechanical support and dynamic reorganization of the cytoskeleton. High concentrations of multivalent counterions promote bundle formation through electrostatic attraction between actin filaments that are negatively charged polyelectrolytes. In this study, we evaluate how physiologically relevant divalent cations affect the mechanical, dynamic, and structural properties of actin bundles. Using a combination of total internal reflection fluorescence microscopy, transmission electron microscopy, and dynamic light scattering, we demonstrate that divalent cations modulate bundle stiffness, length distribution, and lateral growth. Molecular dynamics simulations of an all-atom model of the actin bundle reveal specific actin residues coordinate cation-binding sites that promote the bundle formation. Our work suggests that specific cation interactions may play a fundamental role in the assembly, structure, and mechanical properties of actin bundles.
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Affiliation(s)
- Nicholas Castaneda
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States.,Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida 32827 , United States
| | - Tianyu Zheng
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Hector J Rivera-Jacquez
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Hyun-Ju Lee
- Electron Microscopy Research Center , Korea Basic Science Institute (KBSI) , Cheongju-si , Chungcheongbuk-do 28119 , Republic of Korea
| | - Jaekyung Hyun
- Electron Microscopy Research Center , Korea Basic Science Institute (KBSI) , Cheongju-si , Chungcheongbuk-do 28119 , Republic of Korea
| | - Alexander Balaeff
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Qun Huo
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Hyeran Kang
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
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38
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Architecture shapes contractility in actomyosin networks. Curr Opin Cell Biol 2018; 50:79-85. [PMID: 29482169 DOI: 10.1016/j.ceb.2018.01.015] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 01/30/2018] [Indexed: 01/03/2023]
Abstract
Myosin-driven contraction of the actin cytoskeleton is at the base of cell and tissue morphogenesis. At the molecular level, myosin motors drive contraction by sliding actin filaments past one another using energy produced by ATP hydrolysis. How this microscopic sliding activity gives rise to cell-scale contractions has been an active research question first in muscle cells, and over the last few decades in non-muscle cells. While many early investigations focused on myosin motor activity, increasingly, the nanoscale architecture of the actin network emerges as a key regulator of contractility. Here we review theoretical and in vitro reconstitution studies that have uncovered some of the key mechanisms by which actin network organization controls contractile tension generation. We then discuss recent findings indicating that similar principles apply in cells.
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39
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Wollrab V, Belmonte JM, Baldauf L, Leptin M, Nédeléc F, Koenderink GH. Polarity sorting drives remodeling of actin-myosin networks. J Cell Sci 2018; 132:jcs.219717. [DOI: 10.1242/jcs.219717] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Accepted: 11/01/2018] [Indexed: 12/18/2022] Open
Abstract
Cytoskeletal networks of actin filaments and myosin motors drive many dynamic cell processes. A key characteristic of these networks is their contractility. Despite intense experimental and theoretical efforts, it is not clear what mechanism favors network contraction over expansion. Recent work points to a dominant role for the nonlinear mechanical response of actin filaments, which can withstand stretching but buckle upon compression. Here we present an alternative mechanism. We study how interactions between actin and myosin-2 at the single filament level translate into contraction at the network scale by performing time-lapse imaging on reconstituted quasi-2D-networks mimicking the cell cortex. We observe myosin end-dwelling after it runs processively along actin filaments. This leads to transport and clustering of actin filament ends and the formation of transiently stable bipolar structures. Further we show that myosin-driven polarity sorting produces polar actin asters, which act as contractile nodes that drive contraction in crosslinked networks. Computer simulations comparing the roles of the end-dwelling mechanism and a buckling-dependent mechanism show that the relative contribution of end-dwelling contraction increases as the network mesh-size decreases.
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Affiliation(s)
| | - Julio M. Belmonte
- EMBL, Cell Biology and Developmental Biology Unit and Director's Research Unit, Meyerhofstraße 1, Heidelberg, Germany
| | - Lucia Baldauf
- AMOLF, Science Park 104, 1098 XG Amsterdam, the Netherlands
| | - Maria Leptin
- EMBL, Cell Biology and Developmental Biology Unit and Director's Research Unit, Meyerhofstraße 1, Heidelberg, Germany
| | - François Nédeléc
- EMBL, Cell Biology and Developmental Biology Unit and Director's Research Unit, Meyerhofstraße 1, Heidelberg, Germany
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40
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Kikumoto M, Oosawa F. Thermodynamic measurements of actin polymerization with various cation species. Cytoskeleton (Hoboken) 2017; 74:465-471. [PMID: 29080281 DOI: 10.1002/cm.21416] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 09/26/2017] [Accepted: 10/13/2017] [Indexed: 12/28/2022]
Abstract
We measured the critical concentration of actin polymerized with different polymerization ions and bound divalent cations at low temperatures and estimated thermodynamic parameters. The entropy and enthalpy changes of actin polymerization were 36-55 (cal/mol K) and 2-8 (kcal/mol), respectively, with some exceptions. Both the entropy and enthalpy changes of the polymerization of Ca2+ -actin were sensitive to the polymerization ion (K+ or Na+ ): ΔS = 39 or 36 (cal/mol K), ΔΗ= 3.9 or 2.7 (kcal/mol). The entropy and enthalpy changes (cal/mol K, kcal/mol) of Mg2+ -actin were also sensitive to the polymerization ion in the following order: Mg2+ (55, 7.6) > K+ (46, 5.3) > Na+ (38, 2.4). Those values largely decreased and became even negative in the presence of a high concentration (0.1 M) of K+ , which was likely caused by the charge screening effect of that ion.
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Affiliation(s)
- Mahito Kikumoto
- Structural Biology Research Center, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Fumio Oosawa
- Graduate School of Science, Nagoya University, Professor Emeritus of Nagoya University, Nagoya/Graduate School of Engineering Science, Osaka University, Professor Emeritus of Osaka University, Suita, Japan
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41
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Zimmermann D, Homa KE, Hocky GM, Pollard LW, De La Cruz EM, Voth GA, Trybus KM, Kovar DR. Mechanoregulated inhibition of formin facilitates contractile actomyosin ring assembly. Nat Commun 2017; 8:703. [PMID: 28951543 PMCID: PMC5614989 DOI: 10.1038/s41467-017-00445-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 06/27/2017] [Indexed: 11/20/2022] Open
Abstract
Cytokinesis physically separates dividing cells by forming a contractile actomyosin ring. The fission yeast contractile ring has been proposed to assemble by Search-Capture-Pull-Release from cytokinesis precursor nodes that include the molecular motor type-II myosin Myo2 and the actin assembly factor formin Cdc12. By successfully reconstituting Search-Capture-Pull in vitro, we discovered that formin Cdc12 is a mechanosensor, whereby myosin pulling on formin-bound actin filaments inhibits Cdc12-mediated actin assembly. We mapped Cdc12 mechanoregulation to its formin homology 1 domain, which facilitates delivery of new actin subunits to the elongating actin filament. Quantitative modeling suggests that the pulling force of the myosin propagates through the actin filament, which behaves as an entropic spring, and thereby may stretch the disordered formin homology 1 domain and impede formin-mediated actin filament elongation. Finally, live cell imaging of mechano-insensitive formin mutant cells established that mechanoregulation of formin Cdc12 is required for efficient contractile ring assembly in vivo. The fission yeast cytokinetic ring assembles by Search-Capture-Pull-Release from precursor nodes that include formin Cdc12 and myosin Myo2. The authors reconstitute Search-Capture-Pull in vitro and find that Myo2 pulling on Cdc12-associated actin filaments mechano-inhibits Cdc12-mediated assembly, which enables proper ring assembly in vivo.
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Affiliation(s)
- Dennis Zimmermann
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 E. 58th St., CSLC 212, Chicago, IL, 60637, USA
| | - Kaitlin E Homa
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 E. 58th St., CSLC 212, Chicago, IL, 60637, USA
| | - Glen M Hocky
- Department of Chemistry, The James Franck Institute and Institute for Biophysical Dynamics and Computation Institute, The University of Chicago, 5735 S. Ellis Ave., Searle Chemistry Laboratory 231, Chicago, IL, 60637, USA
| | - Luther W Pollard
- Department of Molecular Physiology and Biophysics, University of Vermont, 149 Beaumont Ave., HSRF 130, Burlington, VT, 05405, USA
| | - Enrique M De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208114, 266 Whitney Ave., New Haven, CT, 06520-8114, USA
| | - Gregory A Voth
- Department of Chemistry, The James Franck Institute and Institute for Biophysical Dynamics and Computation Institute, The University of Chicago, 5735 S. Ellis Ave., Searle Chemistry Laboratory 231, Chicago, IL, 60637, USA.
| | - Kathleen M Trybus
- Department of Molecular Physiology and Biophysics, University of Vermont, 149 Beaumont Ave., HSRF 130, Burlington, VT, 05405, USA.
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 E. 58th St., CSLC 212, Chicago, IL, 60637, USA. .,Department of Biochemistry and Molecular Biology, The University of Chicago, 920 E. 58th St., CSLC 212, Chicago, IL, 60637, USA.
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42
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Elam WA, Cao W, Kang H, Huehn A, Hocky GM, Prochniewicz E, Schramm AC, Negrón K, Garcia J, Bonello TT, Gunning PW, Thomas DD, Voth GA, Sindelar CV, De La Cruz EM. Phosphomimetic S3D cofilin binds but only weakly severs actin filaments. J Biol Chem 2017; 292:19565-19579. [PMID: 28939776 DOI: 10.1074/jbc.m117.808378] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 09/18/2017] [Indexed: 12/30/2022] Open
Abstract
Many biological processes, including cell division, growth, and motility, rely on rapid remodeling of the actin cytoskeleton and on actin filament severing by the regulatory protein cofilin. Phosphorylation of vertebrate cofilin at Ser-3 regulates both actin binding and severing. Substitution of serine with aspartate at position 3 (S3D) is widely used to mimic cofilin phosphorylation in cells and in vitro The S3D substitution weakens cofilin binding to filaments, and it is presumed that subsequent reduction in cofilin occupancy inhibits filament severing, but this hypothesis has remained untested. Here, using time-resolved phosphorescence anisotropy, electron cryomicroscopy, and all-atom molecular dynamics simulations, we show that S3D cofilin indeed binds filaments with lower affinity, but also with a higher cooperativity than wild-type cofilin, and severs actin weakly across a broad range of occupancies. We found that three factors contribute to the severing deficiency of S3D cofilin. First, the high cooperativity of S3D cofilin generates fewer boundaries between bare and decorated actin segments where severing occurs preferentially. Second, S3D cofilin only weakly alters filament bending and twisting dynamics and therefore does not introduce the mechanical discontinuities required for efficient filament severing at boundaries. Third, Ser-3 modification (i.e. substitution with Asp or phosphorylation) "undocks" and repositions the cofilin N terminus away from the filament axis, which compromises S3D cofilin's ability to weaken longitudinal filament subunit interactions. Collectively, our results demonstrate that, in addition to inhibiting actin binding, Ser-3 modification favors formation of a cofilin-binding mode that is unable to sufficiently alter filament mechanical properties and promote severing.
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Affiliation(s)
- W Austin Elam
- From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Wenxiang Cao
- From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Hyeran Kang
- From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Andrew Huehn
- From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Glen M Hocky
- the Department of Chemistry, University of Chicago, Chicago, Illinois 60637
| | - Ewa Prochniewicz
- the Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, and
| | - Anthony C Schramm
- From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Karina Negrón
- From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Jean Garcia
- From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Teresa T Bonello
- the School of Medical Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Peter W Gunning
- the School of Medical Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - David D Thomas
- the Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, and
| | - Gregory A Voth
- the Department of Chemistry, University of Chicago, Chicago, Illinois 60637
| | - Charles V Sindelar
- From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
| | - Enrique M De La Cruz
- From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520,
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43
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Bacterial Tubulins A and B Exhibit Polarized Growth, Mixed-Polarity Bundling, and Destabilization by GTP Hydrolysis. J Bacteriol 2017; 199:JB.00211-17. [PMID: 28716960 DOI: 10.1128/jb.00211-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 07/06/2017] [Indexed: 11/20/2022] Open
Abstract
Bacteria of the genus Prosthecobacter express homologs of eukaryotic α- and β-tubulin, called BtubA and BtubB (BtubA/B), that have been observed to assemble into filaments in the presence of GTP. BtubA/B polymers are proposed to be composed in vitro by two to six protofilaments in contrast to that in vivo, where they have been reported to form 5-protofilament tubes named bacterial microtubules (bMTs). The btubAB genes likely entered the Prosthecobacter lineage via horizontal gene transfer and may be derived from an early ancestor of the modern eukaryotic microtubule (MT). Previous biochemical studies revealed that BtubA/B polymerization is reversible and that BtubA/B folding does not require chaperones. To better understand BtubA/B filament behavior and gain insight into the evolution of microtubule dynamics, we characterized in vitro BtubA/B assembly using a combination of polymerization kinetics assays and microscopy. Like eukaryotic microtubules, BtubA/B filaments exhibit polarized growth with different assembly rates at each end. GTP hydrolysis stimulated by BtubA/B polymerization drives a stochastic mechanism of filament disassembly that occurs via polymer breakage and/or fast continuous depolymerization. We also observed treadmilling (continuous addition and loss of subunits at opposite ends) of BtubA/B filament fragments. Unlike MTs, polymerization of BtubA/B requires KCl, which reduces the critical concentration for BtubA/B assembly and induces it to form stable mixed-orientation bundles in the absence of any additional BtubA/B-binding proteins. The complex dynamics that we observe in stabilized and unstabilized BtubA/B filaments may reflect common properties of an ancestral eukaryotic tubulin polymer.IMPORTANCE Microtubules are polymers within all eukaryotic cells that perform critical functions; they segregate chromosomes, organize intracellular transport, and support the flagella. These functions rely on the remarkable range of tunable dynamic behaviors of microtubules. Bacterial tubulin A and B (BtubA/B) are evolutionarily related proteins that form polymers. They are proposed to be evolved from the ancestral eukaryotic tubulin, a missing link in microtubule evolution. Using microscopy and biochemical approaches to characterize BtubA/B assembly in vitro, we observed that they exhibit complex and structurally polarized dynamic behavior like eukaryotic microtubules but differ in how they self-associate into bundles and how this bundling affects their stability. Our results demonstrate the diversity of mechanisms through which tubulin homologs promote filament dynamics and monomer turnover.
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44
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Ohnuki J, Yodogawa A, Takano M. Electrostatic balance between global repulsion and local attraction in reentrant polymerization of actin. Cytoskeleton (Hoboken) 2017; 74:504-511. [DOI: 10.1002/cm.21391] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 07/11/2017] [Accepted: 07/21/2017] [Indexed: 11/07/2022]
Affiliation(s)
- Jun Ohnuki
- Department of Pure and Applied Physics; Waseda University; Tokyo 169-8555 Japan
| | - Akira Yodogawa
- Department of Advanced Science and Engineering; Waseda University; Tokyo 169-8555 Japan
| | - Mitsunori Takano
- Department of Pure and Applied Physics; Waseda University; Tokyo 169-8555 Japan
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45
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Abstract
Computational and structural studies have been indispensable in investigating the molecular origins of actin filament mechanical properties and modulation by the regulatory severing protein cofilin. All-atom molecular dynamics simulations of cofilactin filament structures determined by electron cryomicroscopy reveal how cofilin enhances the bending and twisting compliance of actin filaments. Continuum mechanics models suggest that buckled cofilactin filaments localize elastic energy at boundaries between bare and cofilin-decorated segments because of their nonuniform elasticity, thereby accelerating filament severing. Here, we develop mesoscopic length-scale (cofil)actin filament models and evaluate the effects of compressive and twisting loads on strain energy distribution at specific interprotein interfaces. The models reliably capture the filament bending and torsional rigidities and intersubunit torsional flexibility measured experimentally with purified protein components. Buckling is predicted to enhance cofilactin filament severing with minimal effects on cofilin occupancy, whereas filament twisting enhances cofilin dissociation without compromising filament integrity. Preferential severing at actin-cofilactin boundaries of buckled filaments is more prominent than predicted by continuum models because of the enhanced spatial resolution. The models developed here will be valuable for evaluating the effects of filament shape deformations on filament stability and interactions with regulatory proteins, and analysis of single filament manipulation assays.
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46
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Burke TA, Harker AJ, Dominguez R, Kovar DR. The bacterial virulence factors VopL and VopF nucleate actin from the pointed end. J Cell Biol 2017; 216:1267-1276. [PMID: 28363971 PMCID: PMC5412564 DOI: 10.1083/jcb.201608104] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 01/31/2017] [Accepted: 02/16/2017] [Indexed: 11/22/2022] Open
Abstract
How the bacterial virulence factors VopL/F from Vibrio catalyze actin nucleation is unclear. Using multicolor TIRF microscopy imaging, Burke et al. find that VopL and VopF stimulate actin assembly via identical pointed-end nucleation mechanisms. VopL and VopF (VopL/F) are tandem WH2-domain actin assembly factors used by infectious Vibrio species to induce actin assembly in host cells. There is disagreement about the filament assembly mechanism of VopL/F, including whether they associate with the filament barbed or pointed end. Here, we used multicolor total internal reflection fluorescence microscopy to directly observe actin assembly with fluorescently labeled VopL/F. In actin monomer assembly reactions, VopL/F exclusively nucleate actin filament assemblies, remaining only briefly associated with the pointed end. VopL/F do not associate with the ends of preassembled filaments. In assembly reactions with saturating profilin, ∼85% of VopL/F molecules also promote nucleation from the pointed end, whereas a smaller fraction (<15%) associate for ∼25 s with the barbed end of preassembled filaments, inhibiting their elongation. We conclude that VopL/F function primarily as actin nucleation factors that remain briefly (∼100 s) associated with the pointed end.
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Affiliation(s)
- Thomas A Burke
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637
| | - Alyssa J Harker
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637
| | - Roberto Dominguez
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637 .,Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637
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47
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Suzuki S, Itakura S, Matsui R, Nakayama K, Nishi T, Nishimoto A, Hama S, Kogure K. Tumor Microenvironment-Sensitive Liposomes Penetrate Tumor Tissue via Attenuated Interaction of the Extracellular Matrix and Tumor Cells and Accompanying Actin Depolymerization. Biomacromolecules 2017; 18:535-543. [PMID: 28055201 DOI: 10.1021/acs.biomac.6b01688] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Delivery of anticancer drugs into tumor cores comprised of malignant cancer cells can result in potent therapeutic effects. However, conventional nanoparticle-based drug delivery systems used for cancer therapy often exhibit inefficient tumor-penetrating properties, thus, suggesting the need to improve the functional design of such systems. Herein, we focus on the interactions between cancer cells and the extracellular matrix (ECM) and demonstrate that liposomes modified with slightly acidic pH-sensitive peptide (SAPSp-lipo) can penetrate in vivo tumor tissue and in vitro spheroids comprised of cancer cells and ECM. We previously reported SAPSp-lipo, tumor microenvironment-sensitive liposomes, are effectively delivered to tumor tissue (Hama et al. J Control Release 2015, 206, 67-74). Compared with conventional liposomes, SAPSp-lipo could be delivered to deeper regions within both spheroids and tumor tissues. Furthermore, tumor penetration was found to be promoted at regions where actin depolymerization was induced by SAPSp-lipo and inhibited by the polymerization of actin. In addition, SAPSp-lipo attenuated the interaction between cancer cells and ECM, contributing to the penetration of SAPSp-lipo. These results suggest that SAPSp-lipo penetrates tumors via the interspace route and is accompanied by actin depolymerization. Taken together, SAPSp-lipo demonstrates potential as a novel tumor-penetrable drug carrier for induction of therapeutic effects against malignant cells that comprise tumor cores.
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Affiliation(s)
- Satoko Suzuki
- Department of Biophysical Chemistry, Kyoto Pharmaceutical University , 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan
| | - Shoko Itakura
- Department of Biophysical Chemistry, Kyoto Pharmaceutical University , 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan
| | - Ryo Matsui
- Department of Biophysical Chemistry, Kyoto Pharmaceutical University , 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan
| | - Kayoko Nakayama
- Department of Biophysical Chemistry, Kyoto Pharmaceutical University , 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan
| | - Takayuki Nishi
- Department of Biophysical Chemistry, Kyoto Pharmaceutical University , 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan
| | - Akinori Nishimoto
- Department of Biophysical Chemistry, Kyoto Pharmaceutical University , 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan
| | - Susumu Hama
- Department of Biophysical Chemistry, Kyoto Pharmaceutical University , 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan
| | - Kentaro Kogure
- Department of Biophysical Chemistry, Kyoto Pharmaceutical University , 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan
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48
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Kim TH, Gill NK, Nyberg KD, Nguyen AV, Hohlbauch SV, Geisse NA, Nowell CJ, Sloan EK, Rowat AC. Cancer cells become less deformable and more invasive with activation of β-adrenergic signaling. J Cell Sci 2016; 129:4563-4575. [PMID: 27875276 DOI: 10.1242/jcs.194803] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 11/06/2016] [Indexed: 12/22/2022] Open
Abstract
Invasion by cancer cells is a crucial step in metastasis. An oversimplified view in the literature is that cancer cells become more deformable as they become more invasive. β-adrenergic receptor (βAR) signaling drives invasion and metastasis, but the effects on cell deformability are not known. Here, we show that activation of β-adrenergic signaling by βAR agonists reduces the deformability of highly metastatic human breast cancer cells, and that these stiffer cells are more invasive in vitro We find that βAR activation also reduces the deformability of ovarian, prostate, melanoma and leukemia cells. Mechanistically, we show that βAR-mediated cell stiffening depends on the actin cytoskeleton and myosin II activity. These changes in cell deformability can be prevented by pharmacological β-blockade or genetic knockout of the β2-adrenergic receptor. Our results identify a β2-adrenergic-Ca2+-actin axis as a new regulator of cell deformability, and suggest that the relationship between cell mechanical properties and invasion might be dependent on context.
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Affiliation(s)
- Tae-Hyung Kim
- Department of Integrative Biology and Physiology, University of California, Los Angeles 90095, USA.,Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles 90095, USA
| | - Navjot Kaur Gill
- Department of Integrative Biology and Physiology, University of California, Los Angeles 90095, USA
| | - Kendra D Nyberg
- Department of Integrative Biology and Physiology, University of California, Los Angeles 90095, USA.,Department of Bioengineering, University of California, Los Angeles 90095, USA
| | - Angelyn V Nguyen
- Department of Integrative Biology and Physiology, University of California, Los Angeles 90095, USA
| | - Sophia V Hohlbauch
- Asylum Research, an Oxford Instruments Company, Santa Barbara, CA 93117, USA
| | - Nicholas A Geisse
- Asylum Research, an Oxford Instruments Company, Santa Barbara, CA 93117, USA
| | - Cameron J Nowell
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Erica K Sloan
- Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles 90095, USA.,Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia.,Division of Cancer Surgery, Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia.,UCLA Jonsson Comprehensive Cancer Center, University of California, Los Angeles 90095, USA.,UCLA AIDS Institute, University of California, Los Angeles 90095, USA
| | - Amy C Rowat
- Department of Integrative Biology and Physiology, University of California, Los Angeles 90095, USA .,Department of Bioengineering, University of California, Los Angeles 90095, USA.,UCLA Jonsson Comprehensive Cancer Center, University of California, Los Angeles 90095, USA
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49
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Hocky GM, Baker JL, Bradley MJ, Sinitskiy AV, De La Cruz EM, Voth GA. Cations Stiffen Actin Filaments by Adhering a Key Structural Element to Adjacent Subunits. J Phys Chem B 2016; 120:4558-67. [PMID: 27146246 PMCID: PMC4959277 DOI: 10.1021/acs.jpcb.6b02741] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Ions
regulate the assembly and mechanical properties of actin filaments.
Recent work using structural bioinformatics and site-specific mutagenesis
favors the existence of two discrete and specific divalent cation
binding sites on actin filaments, positioned in the long axis between
actin subunits. Cation binding at one site drives polymerization,
while the other modulates filament stiffness and plays a role in filament
severing by the regulatory protein, cofilin. Existing structural methods
have not been able to resolve filament-associated cations, and so
in this work we turn to molecular dynamics simulations to suggest
a candidate binding pocket geometry for each site and to elucidate
the mechanism by which occupancy of the “stiffness site”
affects filament mechanical properties. Incorporating a magnesium
ion in the “polymerization site” does not seem to require
any large-scale change to an actin subunit’s conformation.
Binding of a magnesium ion in the “stiffness site” adheres
the actin DNase-binding loop (D-loop) to its long-axis neighbor, which
increases the filament torsional stiffness and bending persistence
length. Our analysis shows that bound D-loops occupy a smaller region
of accessible conformational space. Cation occupancy buries key conserved
residues of the D-loop, restricting accessibility to regulatory proteins
and enzymes that target these amino acids.
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Affiliation(s)
- Glen M Hocky
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, and Computation Institute, The University of Chicago , Chicago, Illinois 60637, United States
| | - Joseph L Baker
- Department of Chemistry, The College of New Jersey , Ewing Township, New Jersey 08628, United States
| | - Michael J Bradley
- Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06520, United States
| | - Anton V Sinitskiy
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, and Computation Institute, The University of Chicago , Chicago, Illinois 60637, United States
| | - Enrique M De La Cruz
- Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06520, United States
| | - Gregory A Voth
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, and Computation Institute, The University of Chicago , Chicago, Illinois 60637, United States
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50
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Gurung R, Yadav R, Brungardt JG, Orlova A, Egelman EH, Beck MR. Actin polymerization is stimulated by actin cross-linking protein palladin. Biochem J 2016; 473:383-96. [PMID: 26607837 PMCID: PMC4912051 DOI: 10.1042/bj20151050] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 11/25/2015] [Indexed: 12/15/2022]
Abstract
The actin scaffold protein palladin regulates both normal cell migration and invasive cell motility, processes that require the co-ordinated regulation of actin dynamics. However, the potential effect of palladin on actin dynamics has remained elusive. In the present study, we show that the actin-binding immunoglobulin-like domain of palladin, which is directly responsible for both actin binding and bundling, also stimulates actin polymerization in vitro. Palladin eliminated the lag phase that is characteristic of the slow nucleation step of actin polymerization. Furthermore, palladin dramatically reduced depolymerization, slightly enhanced the elongation rate, and did not alter the critical concentration. Microscopy and in vitro cross-linking assays reveal differences in actin bundle architecture when palladin is incubated with actin before or after polymerization. These results suggest a model whereby palladin stimulates a polymerization-competent form of globular or monomeric actin (G-actin), akin to metal ions, either through charge neutralization or through conformational changes.
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Affiliation(s)
- Ritu Gurung
- Chemistry Department, Wichita State University, Wichita, KS 67260, U.S.A
| | - Rahul Yadav
- Chemistry Department, Wichita State University, Wichita, KS 67260, U.S.A
| | - Joseph G Brungardt
- Chemistry Department, Wichita State University, Wichita, KS 67260, U.S.A
| | - Albina Orlova
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908, U.S.A
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908, U.S.A
| | - Moriah R Beck
- Chemistry Department, Wichita State University, Wichita, KS 67260, U.S.A.
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