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Wang Y, Wu J, Zsolnay V, Pollard TD, Voth GA. Mechanism of Phosphate Release from Actin Filaments. bioRxiv 2024:2023.08.03.551904. [PMID: 37577500 PMCID: PMC10418243 DOI: 10.1101/2023.08.03.551904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
After ATP-actin monomers assemble filaments, the ATP's γ-phosphate is hydrolyzed within seconds and dissociates over minutes. We used all-atom molecular dynamics simulations to sample the release of phosphate from filaments and study residues that gate release. Dissociation of phosphate from Mg 2+ is rate limiting and associated with an energy barrier of 20 kcal/mol, consistent with experimental rates of phosphate release. Phosphate then diffuses in an internal cavity toward a gate formed by R177 suggested in prior computational studies and cryo-EM structures. The gate is closed when R177 hydrogen bonds with N111 and is open when R177 forms a salt bridge with D179. Most of the time interactions of R177 with other residues occludes the phosphate release pathway. Machine learning analysis reveals that the occluding interactions fluctuate rapidly, underscoring the secondary role of backdoor gate opening in P i release, in contrast with the previous hypothesis that gate opening is the primary event. Significance Statement The protein actin assembles into filaments that participate in muscle contraction and cellular movements. An ATP bound to the actin monomer is hydrolyzed rapidly during filament assembly, but the γ-phosphate dissociates slowly from the filament. We identified phosphate dissociation from Mg 2+ as the rate-limiting step in phosphate release from actin based on an energy barrier that aligns with the experimentally determined release rate. The release of phosphate from the protein requires opening a gate in the actin molecule formed by the interaction between sidechains of arginine 177 and asparagine 111. Surprisingly, simulations revealed other interactions of the sidechain of arginine 177 that occlude the release pathway most of the time but have not been observed in low-temperature cryo-EM structures.
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Chavali SS, Chou SZ, Cao W, Pollard TD, De La Cruz EM, Sindelar CV. Publisher Correction: Cryo-EM structures reveal how phosphate release from Arp3 weakens actin filament branches formed by Arp2/3 complex. Nat Commun 2024; 15:2354. [PMID: 38491023 PMCID: PMC10943100 DOI: 10.1038/s41467-024-46804-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2024] Open
Affiliation(s)
- Sai Shashank Chavali
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA
| | - Steven Z Chou
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, 06030, USA
| | - Wenxiang Cao
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA
| | - Thomas D Pollard
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
- Department of Cell Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
- Department of Molecular and Cell Biology, University of California, 638 Barker Hall, Berkeley, CA, 94720-3200, USA.
| | - Enrique M De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
| | - Charles V Sindelar
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
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Chavali SS, Chou SZ, Cao W, Pollard TD, De La Cruz EM, Sindelar CV. Cryo-EM structures reveal how phosphate release from Arp3 weakens actin filament branches formed by Arp2/3 complex. Nat Commun 2024; 15:2059. [PMID: 38448439 PMCID: PMC10918085 DOI: 10.1038/s41467-024-46179-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 02/16/2024] [Indexed: 03/08/2024] Open
Abstract
Arp2/3 complex nucleates branched actin filaments for cell and organelle movements. Here we report a 2.7 Å resolution cryo-EM structure of the mature branch junction formed by S. pombe Arp2/3 complex that provides details about interactions with both mother and daughter filaments. We determine a second structure at 3.2 Å resolution with the phosphate analog BeFx bound with ADP to Arp3 and ATP bound to Arp2. In this ADP-BeFx transition state the outer domain of Arp3 is rotated 2° toward the mother filament compared with the ADP state and makes slightly broader contacts with actin in both the mother and daughter filaments. Thus, dissociation of Pi from the ADP-Pi transition state reduces the interactions of Arp2/3 complex with the actin filaments and may contribute to the lower mechanical stability of mature branch junctions with ADP bound to the Arps. Our structures also reveal that the mother filament in contact with Arp2/3 complex is slightly bent and twisted, consistent with the preference of Arp2/3 complex binding curved actin filaments. The small degree of twisting constrains models of actin filament mechanics.
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Affiliation(s)
- Sai Shashank Chavali
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA
| | - Steven Z Chou
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, 06030, USA
| | - Wenxiang Cao
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA
| | - Thomas D Pollard
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
- Department of Cell Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
- Department of Molecular and Cell Biology, University of California, 638 Barker Hall, Berkeley, CA, 94720-3200, USA.
| | - Enrique M De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
| | - Charles V Sindelar
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
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Pollard TD, Korn ED. Discovery of the first unconventional myosin: Acanthamoeba myosin-I. Front Physiol 2023; 14:1324623. [PMID: 38046947 PMCID: PMC10693453 DOI: 10.3389/fphys.2023.1324623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 11/07/2023] [Indexed: 12/05/2023] Open
Abstract
Having characterized actin from Acanthamoeba castellanii (Weihing and Korn, Biochemistry, 1971, 10, 590-600) and knowing that myosin had been isolated from the slime mold Physarum (Hatano and Tazawa, Biochim. Biophys. Acta, 1968, 154, 507-519; Adelman and Taylor, Biochemistry, 1969, 8, 4976-4988), we set out in 1969 to find myosin in Acanthamoeba. We used K-EDTA-ATPase activity to assay myosin, because it is a unique feature of muscle myosins. After slightly less than 3 years, we purified a K-EDTA ATPase that interacted with actin. Actin filaments stimulated the Mg-ATPase activity of the crude enzyme, but this was lost with further purification. Recombining fractions from the column where this activity was lost revealed a "cofactor" that allowed actin filaments to stimulate the Mg-ATPase of the purified enzyme. The small size of the heavy chain and physical properties of the purified myosin were unprecedented, so many were skeptical, assuming that our myosin was a proteolytic fragment of a larger myosin similar to muscle or Physarum myosin. Subsequently our laboratories confirmed that Acanthamoeba myosin-I is a novel unconventional myosin that interacts with membrane lipids (Adams and Pollard, Nature, 1989, 340 (6234), 565-568) and that the cofactor is a myosin heavy chain kinase (Maruta and Korn, J. Biol. Chem., 1977, 252, 8329-8332). Phylogenetic analysis (Odronitz and Kollmar, Genome Biology, 2007, 8, R196) later established that class I myosin was the first myosin to appear during the evolution of eukaryotes.
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Affiliation(s)
- Thomas D. Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT, United States
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, United States
| | - Edward D. Korn
- Scientist Emeritus, Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, United States
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Chou SZ, Pollard TD. Cryo-EM structures of both ends of the actin filament explain why the barbed end elongates faster than the pointed end. bioRxiv 2023:2023.05.12.540494. [PMID: 37214997 PMCID: PMC10197683 DOI: 10.1101/2023.05.12.540494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Actin filament ends are the sites of subunit addition during elongation and subunit loss during depolymerization. Prior work established the kinetics and thermodynamics of the assembly reactions at both ends but not the structural basis of their differences. Cryo-EM reconstructions of the barbed end at 3.1 Å resolution and the pointed end at 3.5 Å reveal distinct conformations at the two ends. These conformations explain why barbed ends elongate faster than pointed ends and why pointed ends rapidly dissociate the γ-phosphate released from ATP hydrolysis during assembly. The D-loop of the penultimate subunit at the pointed end is folded onto the terminal subunit, precluding its binding incoming actin monomers, and gates on the phosphate release channels of both subunits are wide open. The samples were prepared with FH2 dimers from fission yeast formin Cdc12. The barbed end reconstruction has extra density that may be partial occupancy by the FH2 domains. Significance Statement Cells depend cytoplasmic filaments assembled from the protein actin for their physical integrity, as tracks for myosin motor proteins and movements of the whole cell and internal organelles. Actin filaments elongate and shrink at their ends by adding or dissociating single actin molecules. We used cryo-electron microscopy to determine the structures of the two ends of actin filaments at 3.5 Å resolution for the slowly growing pointed end and 3.1 Å for the rapidly growing barbed end. These structures reveal why barbed ends grow faster than the pointed ends, why the rate at the pointed end is not diffusion-limited and why the pointed end has a low affinity for the γ-phosphate released from bound ATP inside the filament.
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Rosenbloom AD, Pollard TD. The proline-rich domain of fission yeast WASp (Wsp1p) interacts with actin filaments and inhibits actin polymerization. FEBS Lett 2023; 597:672-681. [PMID: 36650956 PMCID: PMC10023459 DOI: 10.1002/1873-3468.14571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 12/01/2022] [Indexed: 01/19/2023]
Abstract
Members of the Wiskott-Aldrich Syndrome protein (WASp) family activate Arp2/3 complex (actin-related proteins 2 and 3 complex) to form actin filament branches. The proline-rich domain (PRD) of WASp contributes to branching nucleation, and the PRD of budding yeast Las17 binds actin filaments [Urbanek AN et al. (2013) Curr Biol 23, 196-203]. Biochemical assays showed the recombinant PRD of fission yeast Schizosaccharomyces pombe Wsp1p binds actin filaments with micromolar affinity. Recombinant PRDs of both Wsp1p and Las17p slowed the elongation of actin filaments by Mg-ATP-actin monomers by half and slowed the spontaneous polymerization of Mg-ATP-actin monomers modestly. The affinity of PRDs of WASp-family proteins for actin filaments is high enough to contribute to the reported stimulation of actin filament branching by Arp2/3 complex.
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Affiliation(s)
- Aaron D. Rosenbloom
- Department of Chemistry, Yale University, PO Box 208107, New Haven, CT 06520-8103 USA
| | - Thomas D. Pollard
- Departments of Molecular Cellular and Developmental Biology, of Molecular Biophysics and Biochemistry and of Cell Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103 USA
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Pollard TD, Seoane-Viaño I, Ong JJ, Januskaite P, Awwad S, Orlu M, Bande MF, Basit AW, Goyanes A. Inkjet drug printing onto contact lenses: Deposition optimisation and non-invasive dose verification. Int J Pharm X 2022; 5:100150. [PMID: 36593987 PMCID: PMC9804110 DOI: 10.1016/j.ijpx.2022.100150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 12/17/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022] Open
Abstract
Inkjet printing has the potential to advance the treatment of eye diseases by printing drugs on demand onto contact lenses for localised delivery and personalised dosing, while near-infrared (NIR) spectroscopy can further be used as a quality control method for quantifying the drug but has yet to be demonstrated with contact lenses. In this study, a glaucoma therapy drug, timolol maleate, was successfully printed onto contact lenses using a modified commercial inkjet printer. The drug-loaded ink prepared for the printer was designed to match the properties of commercial ink, whilst having maximal drug loading and avoiding ocular inflammation. This setup demonstrated personalised drug dosing by printing multiple passes. Light transmittance was found to be unaffected by drug loading on the contact lens. A novel dissolution model was built, and in vitro dissolution studies showed drug release over at least 3 h, significantly longer than eye drops. NIR was used as an external validation method to accurately quantify the drug dose. Overall, the combination of inkjet printing and NIR represent a novel method for point-of-care personalisation and quantification of drug-loaded contact lenses.
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Affiliation(s)
- Thomas D. Pollard
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Iria Seoane-Viaño
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK,Department of Pharmacology, Pharmacy and Pharmaceutical Technology, Paraquasil Group (GI-2109), Faculty of Pharmacy, and Health Research Institute of Santiago de Compostela (IDIS), University of Santiago de Compostela (USC), Santiago de Compostela 15782, Spain
| | - Jun Jie Ong
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Patricija Januskaite
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Sahar Awwad
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Mine Orlu
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Manuel F. Bande
- Department of Ophthalmology, University Hospital of Santiago de Compostela, Ramon Baltar S/N, Santiago de Compostela 15706, Spain
| | - Abdul W. Basit
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK,FabRx Ltd., Henwood House, Henwood, Ashford TN24 8DH, UK,Corresponding authors at: Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK.
| | - Alvaro Goyanes
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK,FabRx Ltd., Henwood House, Henwood, Ashford TN24 8DH, UK,Departamento de Farmacología, Farmacia y Tecnología Farmacéutica, I+D Farma Group (GI-1645), Facultad de Farmacia, iMATUS and Health Research Institute of Santiago de Compostela (IDIS), Universidade de Santiago de Compostela (USC), Santiago de Compostela 15782, Spain,Corresponding authors at: Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK.
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Chou SZ, Chatterjee M, Pollard TD. Mechanism of actin filament branch formation by Arp2/3 complex revealed by a high-resolution cryo-EM structureof the branch junction. Proc Natl Acad Sci U S A 2022; 119:e2206722119. [PMID: 36442092 PMCID: PMC9894260 DOI: 10.1073/pnas.2206722119] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 10/17/2022] [Indexed: 11/29/2022] Open
Abstract
We reconstructed the structure of actin filament branch junctions formed by fission yeast Arp2/3 complex at 3.5 Å resolution from images collected by electron cryo-microscopy. During specimen preparation, all of the actin subunits and Arp3 hydrolyzed their bound adenosine triphosphate (ATP) and dissociated the γ-phosphate, but Arp2 retained the γ-phosphate. Binding tightly to the side of the mother filament and nucleating the daughter filament growing as a branch requires Arp2/3 complex to undergo a dramatic conformational change where two blocks of structure rotate relative to each other about 25° to align Arp2 and Arp3 as the first two subunits in the branch. During branch formation, Arp2/3 complex acquires more than 8,000 Å2 of new buried surface, accounting for the stability of the branch. Inactive Arp2/3 complex binds only transiently to the side of an actin filament, because its conformation allows only a subset of the interactions found in the branch junction.
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Affiliation(s)
- Steven Z. Chou
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT06520
| | - Moon Chatterjee
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT06520
| | - Thomas D. Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT06520
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT06520
- Department of Cell Biology, Yale University, New Haven, CT06520
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Abstract
Cytokinesis nodes are assemblies of stoichiometric ratios of proteins associated with the plasma membrane, which serve as precursors for the contractile ring during cytokinesis by fission yeast. The total number of nodes is uncertain, because of the limitations of the methods used previously. Here, we used the ~140 nm resolution of Airyscan super-resolution microscopy to measure the fluorescence intensity of small, single cytokinesis nodes marked with Blt1-mEGFP in live fission yeast cells early in mitosis. The ratio of the total Blt1-mEGFP fluorescence in the broad band of cytokinesis nodes to the average fluorescence of a single node gives about 190 single cytokinesis nodes in wild-type fission yeast cells early in mitosis. Most, but not all of these nodes condense into a contractile ring. The number of cytokinesis nodes scales with cell size in four strains tested, although large diameter rga4Δ mutant cells form somewhat fewer cytokinesis nodes than expected from the overall trend. The Pom1 kinase restricts cytokinesis nodes from the ends of cells, but the surface density of Pom1 on the plasma membrane around the equators of cells is similar with a wide range of node numbers, so Pom1 does not control cytokinesis node number. However, when the concentrations of either kinase Pom1 or kinase Cdr2 were varied with the nmt1 promoter, the numbers of cytokinesis nodes increased above a baseline of about ~190 with the total cellular concentration of either kinase.
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Affiliation(s)
- Wasim A Sayyad
- Department of Molecular Cellular and Developmental Biology,Yale University, New Haven, United States
| | - Thomas D Pollard
- Department of Molecular Cellular and Developmental Biology,Yale University, New Haven, United States.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States.,Department of Cell Biology,Yale University, New Haven, United States
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Pollard TD. Landmarks in the discovery of a role for actin in cell locomotion. Mol Biol Cell 2022; 33:rt2. [PMID: 35612984 PMCID: PMC9561858 DOI: 10.1091/mbc.e21-08-0401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
During the late 1960s four independent lines of research implicated actin in cellular motility. This Retrospective recounts how biochemistry, light and electron microscopy, and inhibitory natural products all contributed to this breakthrough.
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Affiliation(s)
- Thomas D Pollard
- Departments of Molecular Cellular and Developmental Biology, Departments of Molecular Biophysics and Biochemistry, and Department of Cell Biology, Yale University, New Haven, CT 06520-8103
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Nickaeen M, Berro J, Pollard TD, Slepchenko BM. A model of actin-driven endocytosis explains differences of endocytic motility in budding and fission yeast. Mol Biol Cell 2022; 33:ar16. [PMID: 34910589 PMCID: PMC9250386 DOI: 10.1091/mbc.e21-07-0362] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 11/23/2021] [Accepted: 12/10/2021] [Indexed: 11/15/2022] Open
Abstract
A comparative study (Sun et al., 2019) showed that the abundance of proteins at sites of endocytosis in fission and budding yeast is more similar in the two species than previously thought, yet membrane invaginations in fission yeast elongate twofold faster and are nearly twice as long as in budding yeast. Here we use a three-dimensional model of a motile endocytic invagination (Nickaeen et al., 2019) to investigate factors affecting elongation of the invaginations. We found that differences in turgor pressure in the two yeast species can largely explain the paradoxical differences observed experimentally in endocytic motility.
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Affiliation(s)
- Masoud Nickaeen
- Richard D. Berlin Center for Cell Analysis and Modeling, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030
| | - Julien Berro
- Department of Molecular Biophysics and Biochemistry, Yale University, and Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06511, and
- Nanobiology Institute, Yale University, New Haven, CT 06520
| | - Thomas D. Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University
- Department of Molecular Biophysics and Biochemistry, Yale University, and Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06511, and
| | - Boris M. Slepchenko
- Richard D. Berlin Center for Cell Analysis and Modeling, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030
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Awad A, Trenfield SJ, Pollard TD, Ong JJ, Elbadawi M, McCoubrey LE, Goyanes A, Gaisford S, Basit AW. Connected healthcare: Improving patient care using digital health technologies. Adv Drug Deliv Rev 2021; 178:113958. [PMID: 34478781 DOI: 10.1016/j.addr.2021.113958] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 07/12/2021] [Accepted: 08/29/2021] [Indexed: 12/22/2022]
Abstract
Now more than ever, traditional healthcare models are being overhauled with digital technologies of Healthcare 4.0 increasingly adopted. Worldwide, digital devices are improving every stage of the patient care pathway. For one, sensors are being used to monitor patient metrics 24/7, permitting swift diagnosis and interventions. At the treatment stage, 3D printers are under investigation for the concept of personalised medicine by allowing patients access to on-demand, customisable therapeutics. Robots are also being explored for treatment, by empowering precision surgery, rehabilitation, or targeted drug delivery. Within medical logistics, drones are being leveraged to deliver critical treatments to remote areas, collect samples, and even provide emergency aid. To enable seamless integration within healthcare, the Internet of Things technology is being exploited to form closed-loop systems that remotely communicate with one another. This review outlines the most promising healthcare technologies and devices, their strengths, drawbacks, and opportunities for clinical adoption.
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Affiliation(s)
- Atheer Awad
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Sarah J Trenfield
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Thomas D Pollard
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Jun Jie Ong
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Moe Elbadawi
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Laura E McCoubrey
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Alvaro Goyanes
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK; FabRx Ltd., Henwood House, Henwood, Ashford, Kent TN24 8DH, UK; Departamento de Farmacología, Farmacia y Tecnología Farmacéutica, I+D Farma (GI-1645), Facultad de Farmacia, Health Research Institute of Santiago de Compostela (IDIS), Universidade de Santiago de Compostela, 15782, Spain
| | - Simon Gaisford
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK; FabRx Ltd., Henwood House, Henwood, Ashford, Kent TN24 8DH, UK
| | - Abdul W Basit
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK; FabRx Ltd., Henwood House, Henwood, Ashford, Kent TN24 8DH, UK.
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Rosenbloom AD, Kovar EW, Kovar DR, Loew LM, Pollard TD. Mechanism of actin filament nucleation. Biophys J 2021; 120:4399-4417. [PMID: 34509503 DOI: 10.1016/j.bpj.2021.09.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 07/23/2021] [Accepted: 09/07/2021] [Indexed: 11/16/2022] Open
Abstract
We used computational methods to analyze the mechanism of actin filament nucleation. We assumed a pathway where monomers form dimers, trimers, and tetramers that then elongate to form filaments but also considered other pathways. We aimed to identify the rate constants for these reactions that best fit experimental measurements of polymerization time courses. The analysis showed that the formation of dimers and trimers is unfavorable because the association reactions are orders of magnitude slower than estimated in previous work rather than because of rapid dissociation of dimers and trimers. The 95% confidence intervals calculated for the four rate constants spanned no more than one order of magnitude. Slow nucleation reactions are consistent with published high-resolution structures of actin filaments and molecular dynamics simulations of filament ends. One explanation for slow dimer formation, which we support with computational analysis, is that actin monomers are in a conformational equilibrium with a dominant conformation that cannot participate in the nucleation steps.
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Affiliation(s)
| | - Elizabeth W Kovar
- Biological Sciences Collegiate Division, The University of Chicago, Chicago, Illinois; R. D. Berlin Center for Cell Analysis and Modeling, The University of Connecticut School of Medicine, Farmington, Connecticut
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois; and
| | - Leslie M Loew
- R. D. Berlin Center for Cell Analysis and Modeling, The University of Connecticut School of Medicine, Farmington, Connecticut
| | - Thomas D Pollard
- Departments of Molecular Cellular and Developmental Biology, of Molecular Biophysics and Biochemistry, and of Cell Biology, Yale University, New Haven, Connecticut.
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14
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Malla M, Pollard TD, Chen Q. Counting actin in contractile rings reveals novel contributions of cofilin and type II myosins to fission yeast cytokinesis. Mol Biol Cell 2021; 33:ar51. [PMID: 34613787 PMCID: PMC9265160 DOI: 10.1091/mbc.e21-08-0376] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Cytokinesis by animals, fungi, and amoebas depends on actomyosin contractile rings, which are stabilized by continuous turnover of actin filaments. Remarkably little is known about the amount of polymerized actin in contractile rings, so we used low concentrations of GFP-Lifeact to count total polymerized actin molecules in the contractile rings of live fission yeast cells. Contractile rings of wild-type cells accumulated polymerized actin molecules at 4900/min to a peak number of ∼198,000 followed by a loss of actin at 5400/min throughout ring constriction. In adf1-M3 mutant cells with cofilin that severs actin filaments poorly, contractile rings accumulated polymerized actin at twice the normal rate and eventually had almost twofold more actin along with a proportional increase in type II myosins Myo2, Myp2, and formin Cdc12. Although 30% of adf1-M3 mutant cells failed to constrict their rings fully, the rest lost actin from the rings at the wild-type rates. Mutations of type II myosins Myo2 and Myp2 reduced contractile ring actin filaments by half and slowed the rate of actin loss from the rings.
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Affiliation(s)
- Mamata Malla
- Department of Biological Sciences, The University of Toledo, Toledo, OH 43606
| | - Thomas D Pollard
- Departments of Molecular Cellular and Developmental Biology.,Departments of Molecular Biophysics and Biochemistry.,Department of Cell Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103 USA
| | - Qian Chen
- Department of Biological Sciences, The University of Toledo, Toledo, OH 43606.,Departments of Molecular Cellular and Developmental Biology
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15
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Ong JJ, Pollard TD, Goyanes A, Gaisford S, Elbadawi M, Basit AW. Optical biosensors - Illuminating the path to personalized drug dosing. Biosens Bioelectron 2021; 188:113331. [PMID: 34038838 DOI: 10.1016/j.bios.2021.113331] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 05/06/2021] [Accepted: 05/08/2021] [Indexed: 02/06/2023]
Abstract
Optical biosensors are low-cost, sensitive and portable devices that are poised to revolutionize the medical industry. Healthcare monitoring has already been transformed by such devices, with notable recent applications including heart rate monitoring in smartwatches and COVID-19 lateral flow diagnostic test kits. The commercial success and impact of existing optical sensors has galvanized research in expanding its application in numerous disciplines. Drug detection and monitoring seeks to benefit from the fast-approaching wave of optical biosensors, with diverse applications ranging from illicit drug testing, clinical trials, monitoring in advanced drug delivery systems and personalized drug dosing. The latter has the potential to significantly improve patients' lives by minimizing toxicity and maximizing efficacy. To achieve this, the patient's serum drug levels must be frequently measured. Yet, the current method of obtaining such information, namely therapeutic drug monitoring (TDM), is not routinely practiced as it is invasive, expensive, time-consuming and skilled labor-intensive. Certainly, optical sensors possess the capabilities to challenge this convention. This review explores the current state of optical biosensors in personalized dosing with special emphasis on TDM, and provides an appraisal on recent strategies. The strengths and challenges of optical biosensors are critically evaluated, before concluding with perspectives on the future direction of these sensors.
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Affiliation(s)
- Jun Jie Ong
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, United Kingdom
| | - Thomas D Pollard
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, United Kingdom
| | - Alvaro Goyanes
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, United Kingdom; Departamento de Farmacología, Farmacia y Tecnología Farmacéutica, I+D Farma Group (GI-1645), Universidade de Santiago de Compostela, 15782, Spain
| | - Simon Gaisford
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, United Kingdom
| | - Mohammed Elbadawi
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, United Kingdom
| | - Abdul W Basit
- Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, United Kingdom.
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16
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Chou SZ, Pollard TD. Cryo-electron microscopy structures of pyrene-labeled ADP-P i- and ADP-actin filaments. Nat Commun 2020; 11:5897. [PMID: 33214556 PMCID: PMC7677365 DOI: 10.1038/s41467-020-19762-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 10/28/2020] [Indexed: 11/17/2022] Open
Abstract
Since the fluorescent reagent N-(1-pyrene)iodoacetamide was first used to label skeletal muscle actin in 1981, the pyrene-labeled actin has become the most widely employed tool to measure the kinetics of actin polymerization and the interaction between actin and actin-binding proteins. Here we report high-resolution cryo-electron microscopy structures of actin filaments with N-1-pyrene conjugated to cysteine 374 and either ADP (3.2 Å) or ADP-phosphate (3.0 Å) in the active site. Polymerization buries pyrene in a hydrophobic cavity between subunits along the long-pitch helix with only minor differences in conformation compared with native actin filaments. These structures explain how polymerization increases the fluorescence 20-fold, how myosin and cofilin binding to filaments reduces the fluorescence, and how profilin binding to actin monomers increases the fluorescence. For almost forty years, N-(1-pyrene) iodoacetamide has been used to label actin at C374, but the mechanisms of the fluorescence changes are still unknown due to the lack of structural information. Here authors provide cryo-EM structures of actin filaments with N-1-pyrene conjugated to cysteine 374 and either ADP or ADP-phosphate in the active site.
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Affiliation(s)
- Steven Z Chou
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA
| | - Thomas D Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA. .,Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA. .,Department of Cell Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
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17
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Dundon SER, Pollard TD. Microtubule nucleation promoters Mto1 and Mto2 regulate cytokinesis in fission yeast. Mol Biol Cell 2020; 31:1846-1856. [PMID: 32520628 PMCID: PMC7525812 DOI: 10.1091/mbc.e19-12-0686] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 05/26/2020] [Accepted: 06/04/2020] [Indexed: 01/16/2023] Open
Abstract
Microtubules of the mitotic spindle direct cytokinesis in metazoans but this has not been documented in fungi. We report evidence that microtubule nucleators at the spindle pole body help coordinate cytokinetic furrow formation in fission yeast. The temperature-sensitive cps1-191 strain (Liu et al., 1999) with a D277N substitution in β-glucan synthase 1 (Cps1/Bgs1) was reported to arrest with an unconstricted contractile ring. We discovered that contractile rings in cps1-191 cells constrict slowly and that an mto2S338N mutation is required with the bgs1D277Nmutation to reproduce the cps1-191 phenotype. Complexes of Mto2 and Mto1 with γ-tubulin regulate microtubule assembly. Deletion of Mto1 along with the bgs1D277N mutation also gives the cps1-191 phenotype, which is not observed in mto2S338N or mto1Δ cells expressing bgs1+. Both mto2S338N and mto1Δ cells nucleate fewer astral microtubules than normal and have higher levels of Rho1-GTP at the division site than wild-type cells. We report multiple conditions that sensitize mto1Δ and mto2S338N cells to furrow ingression phenotypes.
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Affiliation(s)
- Samantha E. R. Dundon
- Departments of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103
| | - Thomas D. Pollard
- Departments of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103
- Departments of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8103
- Department of Cell Biology, Yale University, New Haven, CT 06520-8103
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18
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Abstract
We provide guidelines for using statistical methods to analyze the types of experiments reported in cellular and molecular biology journals such as Molecular Biology of the Cell. Our aim is to help experimentalists use these methods skillfully, avoid mistakes, and extract the maximum amount of information from their laboratory work. We focus on comparing the average values of control and experimental samples. A Supplemental Tutorial provides examples of how to analyze experimental data using R software.
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Affiliation(s)
- Daniel A Pollard
- Department of Biology, Western Washington University, Bellingham, WA 98225-9160
| | - Thomas D Pollard
- Departments of Molecular Cellular and Developmental Biology, Molecular Biophysics and Biochemistry, and Cell Biology, Yale University, New Haven, CT 06520-8103
| | - Katherine S Pollard
- Gladstone Institutes, Chan-Zuckerberg Biohub, and University of California, San Francisco, San Francisco, CA 94158
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19
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20
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Sun Y, Schöneberg J, Chen X, Jiang T, Kaplan C, Xu K, Pollard TD, Drubin DG. Direct comparison of clathrin-mediated endocytosis in budding and fission yeast reveals conserved and evolvable features. eLife 2019; 8:50749. [PMID: 31829937 PMCID: PMC6908435 DOI: 10.7554/elife.50749] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 11/14/2019] [Indexed: 12/13/2022] Open
Abstract
Conserved proteins drive clathrin-mediated endocytosis (CME), which from yeast to humans involves a burst of actin assembly. To gain mechanistic insights into this process, we performed a side-by-side quantitative comparison of CME in two distantly related yeast species. Though endocytic protein abundance in S. pombe and S. cerevisiae is more similar than previously thought, membrane invagination speed and depth are two-fold greater in fission yeast. In both yeasts, accumulation of ~70 WASp molecules activates the Arp2/3 complex to drive membrane invagination. In contrast to budding yeast, WASp-mediated actin nucleation plays an essential role in fission yeast endocytosis. Genetics and live-cell imaging revealed core CME spatiodynamic similarities between the two yeasts, although the assembly of two zones of actin filaments is specific for fission yeast and not essential for CME. These studies identified conserved CME mechanisms and species-specific adaptations with broad implications that are expected to extend from yeast to humans.
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Affiliation(s)
- Yidi Sun
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Johannes Schöneberg
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Xuyan Chen
- Department of Chemistry, University of California, Berkeley, Berkeley, United States
| | - Tommy Jiang
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Charlotte Kaplan
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, Berkeley, United States
| | - Thomas D Pollard
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States.,Department of Cell Biology, Yale University, New Haven, United States.,Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, United States
| | - David G Drubin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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21
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Abstract
This is the story of someone who has been fortunate to work in a field of research where essentially nothing was known at the outset but that blossomed with the discovery of profound insights about two basic biological processes: cell motility and cytokinesis. The field started with no molecules, just a few people, and primitive methods. Over time, technological advances in biophysics, biochemistry, and microscopy allowed the combined efforts of scientists in hundreds of laboratories to explain mysterious processes with molecular mechanisms that can be embodied in mathematical equations and simulated by computers. The success of this field is a tribute to the power of the reductionist strategy for understanding biology.
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Affiliation(s)
- Thomas D Pollard
- Departments of Molecular, Cellular and Developmental Biology; Molecular Biophysics and Biochemistry; and Cell Biology, Yale University, New Haven, Connecticut 06520-8103, USA;
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22
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Abstract
We formulated a spatially resolved model to estimate forces exerted by a polymerizing actin meshwork on an invagination of the plasma membrane during endocytosis in yeast cells. The model, which approximates the actin meshwork as a visco-active gel exerting forces on a rigid spherocylinder representing the endocytic invagination, is tightly constrained by experimental data. Simulations of the model produce forces that can overcome resistance of turgor pressure in yeast cells. Strong forces emerge due to the high density of polymerized actin in the vicinity of the invagination and because of entanglement of the meshwork due to its dendritic structure and cross-linking. The model predicts forces orthogonal to the invagination that are consistent with formation of a flask shape, which would diminish the net force due to turgor pressure. Simulations of the model with either two rings of nucleation-promoting factors (NPFs) as in fission yeast or a single ring of NPFs as in budding yeast produce enough force to elongate the invagination against the turgor pressure.
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Affiliation(s)
- Masoud Nickaeen
- Richard D. Berlin Center for Cell Analysis and Modeling, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030
| | - Julien Berro
- Departments of Molecular Biophysics and Biochemistry and of Cell Biology.,Nanobiology Institute, Yale University, New Haven, CT 06520
| | - Thomas D Pollard
- Departments of Molecular Biophysics and Biochemistry and of Cell Biology.,Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06520
| | - Boris M Slepchenko
- Richard D. Berlin Center for Cell Analysis and Modeling, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030
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23
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Chatterjee M, Pollard TD. The Functionally Important N-Terminal Half of Fission Yeast Mid1p Anillin Is Intrinsically Disordered and Undergoes Phase Separation. Biochemistry 2019; 58:3031-3041. [PMID: 31243991 DOI: 10.1021/acs.biochem.9b00217] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Division of fungal and animal cells depends on scaffold proteins called anillins. Cytokinesis by the fission yeast Schizosaccharomyces pombe is compromised by the loss of anillin Mid1p (Mid1, UniProtKB P78953 ), because cytokinesis organizing centers, called nodes, are misplaced and fail to acquire myosin-II, so they assemble slowly into abnormal contractile rings. The C-terminal half of Mid1p consists of lipid binding C2 and PH domains, but the N-terminal half (Mid1p-N452) performs most of the functions of the full-length protein. Little is known about the structure of the N-terminal half of Mid1p, so we investigated its physical properties using structure prediction tools, spectroscopic techniques, and hydrodynamic measurements. The data indicate that Mid1p-N452 is intrinsically disordered but moderately compact. Recombinant Mid1p-N452 purified from insect cells was phosphorylated, which weakens its tendency to aggregate. Purified Mid1p-N452 demixes into liquid droplets at concentrations far below its concentration in nodes. These physical properties are appropriate for scaffolding other proteins in nodes.
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24
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Abstract
Division of amoebas, fungi, and animal cells into two daughter cells at the end of the cell cycle depends on a common set of ancient proteins, principally actin filaments and myosin-II motors. Anillin, formins, IQGAPs, and many other proteins regulate the assembly of the actin filaments into a contractile ring positioned between the daughter nuclei by different mechanisms in fungi and animal cells. Interactions of myosin-II with actin filaments produce force to assemble and then constrict the contractile ring to form a cleavage furrow. Contractile rings disassemble as they constrict. In some cases, knowledge about the numbers of participating proteins and their biochemical mechanisms has made it possible to formulate molecularly explicit mathematical models that reproduce the observed physical events during cytokinesis by computer simulations.
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Affiliation(s)
- Thomas D Pollard
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA;
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8103, USA
- Department of Cell Biology, Yale University, New Haven, Connecticut 06520-8103, USA
| | - Ben O'Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA;
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25
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Abstract
Division of amoebas, fungi, and animal cells into two daughter cells at the end of the cell cycle depends on a common set of ancient proteins, principally actin filaments and myosin-II motors. Anillin, formins, IQGAPs, and many other proteins regulate the assembly of the actin filaments into a contractile ring positioned between the daughter nuclei by different mechanisms in fungi and animal cells. Interactions of myosin-II with actin filaments produce force to assemble and then constrict the contractile ring to form a cleavage furrow. Contractile rings disassemble as they constrict. In some cases, knowledge about the numbers of participating proteins and their biochemical mechanisms has made it possible to formulate molecularly explicit mathematical models that reproduce the observed physical events during cytokinesis by computer simulations.
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Affiliation(s)
- Thomas D Pollard
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA;
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8103, USA
- Department of Cell Biology, Yale University, New Haven, Connecticut 06520-8103, USA
| | - Ben O'Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA;
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26
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Chou SZ, Pollard TD. Mechanism of actin polymerization revealed by cryo-EM structures of actin filaments with three different bound nucleotides. Proc Natl Acad Sci U S A 2019; 116:4265-4274. [PMID: 30760599 PMCID: PMC6410863 DOI: 10.1073/pnas.1807028115] [Citation(s) in RCA: 131] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We used cryo-electron microscopy (cryo-EM) to reconstruct actin filaments with bound AMPPNP (β,γ-imidoadenosine 5'-triphosphate, an ATP analog, resolution 3.1 Å), ADP-Pi (ADP with inorganic phosphate, resolution 3.1 Å), or ADP (resolution 3.6 Å). Subunits in the three filaments have similar backbone conformations, so assembly rather than ATP hydrolysis or phosphate dissociation is responsible for their flattened conformation in filaments. Polymerization increases the rate of ATP hydrolysis by changing the positions of the side chains of Q137 and H161 in the active site. Flattening during assembly also promotes interactions along both the long-pitch and short-pitch helices. In particular, conformational changes in subdomain 3 open up multiple favorable interactions with the DNase-I binding loop in subdomain 2 of the adjacent subunit. Subunits at the barbed end of the filament are likely to be in this favorable conformation, while monomers are not. This difference explains why filaments grow faster at the barbed end than the pointed end. When phosphate dissociates from ADP-Pi-actin through a backdoor channel, the conformation of the C terminus changes so it distorts the DNase binding loop, which allows cofilin binding, and a network of interactions among S14, H73, G74, N111, R177, and G158 rearranges to open the phosphate release site.
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Affiliation(s)
- Steven Z Chou
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103
| | - Thomas D Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103;
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8103
- Department of Cell Biology, Yale University, New Haven, CT 06520-8103
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27
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28
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Abstract
This short review traces how our knowledge of the molecular mechanisms of cellular movements originated and developed over the past 50 years. Work on actin-based and microtubule-based movements developed in different ways, but in both fields, the discovery of the key proteins drove progress. Starting from an inventory of zero molecules in 1960, both fields matured spectacularly, so we now know the atomic structures of the important proteins, understand the kinetics and thermodynamics of their interactions, have documented how the molecules behave in cells, and can test theories with molecularly explicit computer simulations of cellular processes.
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Affiliation(s)
- Thomas D Pollard
- Departments of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
- Departments of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
- Department of Cell Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
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29
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Epstein AE, Espinoza-Sanchez S, Pollard TD. Phosphorylation of Arp2 is not essential for Arp2/3 complex activity in fission yeast. Life Sci Alliance 2018; 1:e201800202. [PMID: 30456391 PMCID: PMC6238581 DOI: 10.26508/lsa.201800202] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 10/12/2018] [Accepted: 10/12/2018] [Indexed: 12/23/2022] Open
Abstract
LeClaire et al presented evidence that phosphorylation of three sites on the Arp2 subunit activates the Arp2/3 complex to nucleate actin filaments. We mutated the homologous residues of Arp2 (Y198, T233, and T234) in the fission yeast genome to amino acids that preclude or mimic phosphorylation. Arp2/3 complex is essential for the viability of fission yeast, yet strains unable to phosphorylate these sites grew normally. Y198F/T233A/T234A Arp2 was only nonfunctional if GFP-tagged, as observed by LeClaire et al in Drosophila cells. Replacing both T233 and T234 with aspartic acid was lethal, suggesting that phosphorylation might be inhibitory. Nevertheless, blocking phosphorylation at these sites had the same effect as mimicking it: slowing assembly of endocytic actin patches. Mass spectrometry revealed phosphorylation at a fourth conserved Arp2 residue, Y218, but both blocking and mimicking phosphorylation of Y218 only slowed actin patch assembly slightly. Therefore, phosphorylation of Y198, T233, T234, and Y218 is not required for the activity of fission yeast Arp2/3 complex.
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Affiliation(s)
- Alexander E Epstein
- Departments of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Sofia Espinoza-Sanchez
- Departments of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Thomas D Pollard
- Departments of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT, USA
- Departments of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
- Department of Cell Biology, Yale University, New Haven, CT, USA
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30
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Fujiwara I, Zweifel ME, Courtemanche N, Pollard TD. Latrunculin A Accelerates Actin Filament Depolymerization in Addition to Sequestering Actin Monomers. Curr Biol 2018; 28:3183-3192.e2. [PMID: 30270183 DOI: 10.1016/j.cub.2018.07.082] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 04/30/2018] [Accepted: 07/31/2018] [Indexed: 11/16/2022]
Abstract
Latrunculin A (LatA), a toxin from the red sea sponge Latrunculia magnifica, is the most widely used reagent to depolymerize actin filaments in experiments on live cells. LatA binds actin monomers and sequesters them from polymerization [1, 2]. Low concentrations of LatA result in rapid (tens of seconds) disassembly of actin filaments in animal [3] and yeast cells [2]. Depolymerization is usually assumed to result from sequestration of actin monomers. Our observations of single-muscle actin filaments by TIRF microscopy showed that LatA bound ATP-actin monomers with a higher affinity (Kd = 0.1 μM) than ADP-Pi-actin (Kd = 0.4 μM) or ADP-actin (Kd = 4.7 μM). LatA also slowly severed filaments and increased the depolymerization rate at both ends of filaments freshly assembled from ATP-actin to the rates of ADP-actin. This rate plateaued at LatA concentrations >60 μM. LatA did not change the depolymerization rates of ADP- actin filaments or ADP-Pi-actin filaments generated with 160 mM phosphate in the buffer. LatA did not increase the rate of phosphate release from bulk samples of filaments assembled from ATP-actin. Thermodynamic analysis showed that LatA binds weakly to actin filaments with a Kd >100 μM. We propose that concentrations of LatA much lower than this Kd promote phosphate dissociation only from both ends of filaments, resulting in depolymerization limited by the rate of ADP-actin dissociation. Thus, one must consider both rapid actin depolymerization and severing in addition to sequestering actin monomers when interpreting the effects of LatA on cells.
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Affiliation(s)
- Ikuko Fujiwara
- Frontier Research Institute for Materials Science, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya 466-8555, Japan; Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT 06520, USA.
| | - Mark E Zweifel
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Naomi Courtemanche
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Thomas D Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT 06520, USA; Departments of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA; Department of Cell Biology, Yale University, New Haven, CT 06520, USA
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31
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Pollard TD. Theory from the Oster Laboratory Leaps Ahead of Experiment in Understanding Actin-Based Cellular Motility. Biophys J 2018; 111:1589-1592. [PMID: 27760345 DOI: 10.1016/j.bpj.2016.08.044] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 08/30/2016] [Indexed: 10/20/2022] Open
Affiliation(s)
- Thomas D Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, Connecticut; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut; Department of Cell Biology, Yale University, New Haven, Connecticut.
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32
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Dey SK, Pollard TD. Involvement of the septation initiation network in events during cytokinesis in fission yeast. J Cell Sci 2018; 131:jcs.216895. [PMID: 30072443 DOI: 10.1242/jcs.216895] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 07/23/2018] [Indexed: 10/28/2022] Open
Abstract
The septation initiation network (SIN), comprising a GTPase and a cascade of three protein kinases, regulates cell division in fission yeast Schizosaccharomyces pombe, but questions remain about its influence on cytokinesis. Here, we made quantitative measurements of the numbers of Cdc7p kinase molecules (a marker for SIN activity) on spindle pole bodies (SPBs), and on the timing of assembly, maturation and constriction of contractile rings via six different proteins tagged with fluorescent proteins. When SIN activity is low in spg1-106 mutant cells at 32°C, cytokinetic nodes formed contractile rings ∼3 min slower than wild-type cells. During the maturation period, these rings maintained normal levels of the myosin-II mEGFP-Myo2p but accumulated less of the F-BAR protein Cdc15p-GFP than in wild-type cells. The Cdc15p-GFP fluorescence then disintegrated into spots as mEGFP-Myo2p dissociated slowly. Some rings started to constrict at the normal time, but most failed to complete constriction. When high SIN activity persists far longer than normal on both SPBs in cdc16-116 mutant cells at 32°C, contractile rings assembled and constricted normally, but disassembled slowly, delaying cell separation.
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Affiliation(s)
- Sumit K Dey
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA
| | - Thomas D Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA .,Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA.,Department of Cell Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA
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33
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Abstract
Formins play an important role in the polymerization of unbranched actin filaments, and particular formins slow elongation by 5–95%. We studied the interactions between actin and the FH2 domains of formins Cdc12, Bni1 and mDia1 to understand the factors underlying their different rates of polymerization. All-atom molecular dynamics simulations revealed two factors that influence actin filament elongation and correlate with the rates of elongation. First, FH2 domains can sterically block the addition of new actin subunits. Second, FH2 domains flatten the helical twist of the terminal actin subunits, making the end less favorable for subunit addition. Coarse-grained simulations over longer time scales support these conclusions. The simulations show that filaments spend time in states that either allow or block elongation. The rate of elongation is a time-average of the degree to which the formin compromises subunit addition rather than the formin-actin complex literally being in ‘open’ or ‘closed’ states.
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Affiliation(s)
- Fikret Aydin
- Department of Chemistry, The University of Chicago, Chicago, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, United States.,James Franck Institute, The University of Chicago, Chicago, United States
| | - Naomi Courtemanche
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, United States.,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, United States
| | - Thomas D Pollard
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, United States.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Gregory A Voth
- Department of Chemistry, The University of Chicago, Chicago, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, United States.,James Franck Institute, The University of Chicago, Chicago, United States
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34
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Abstract
Organisms in the three domains of life depend on protein polymers to form a cytoskeleton that helps to establish their shapes, maintain their mechanical integrity, divide, and, in many cases, move. Eukaryotes have the most complex cytoskeletons, comprising three cytoskeletal polymers-actin filaments, intermediate filaments, and microtubules-acted on by three families of motor proteins (myosin, kinesin, and dynein). Prokaryotes have polymers of proteins homologous to actin and tubulin but no motors, and a few bacteria have a protein related to intermediate filament proteins.
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Affiliation(s)
- Thomas D Pollard
- Departments of Molecular Cellular and Developmental Biology, Molecular Biophysics and Biochemistry, and Cell Biology, Yale University, New Haven, Connecticut 06520-8103
| | - Robert D Goldman
- Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
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35
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Friend JE, Sayyad WA, Arasada R, McCormick CD, Heuser JE, Pollard TD. Fission yeast Myo2: Molecular organization and diffusion in the cytoplasm. Cytoskeleton (Hoboken) 2017; 75:164-173. [PMID: 29205883 DOI: 10.1002/cm.21425] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 11/22/2017] [Accepted: 11/27/2017] [Indexed: 12/20/2022]
Abstract
Myosin-II is required for the assembly and constriction of cytokinetic contractile rings in fungi and animals. We used electron microscopy, fluorescence recovery after photobleaching (FRAP), and fluorescence correlation spectroscopy (FCS) to characterize the physical properties of Myo2 from fission yeast Schizosaccharomyces pombe. By electron microscopy, Myo2 has two heads and a coiled-coiled tail like myosin-II from other species. The first 65 nm of the tail is a stiff rod, followed by a flexible, less-ordered region up to 30 nm long. Myo2 sediments as a 7 S molecule in high salt, but aggregates rather than forming minifilaments at lower salt concentrations; this is unaffected by heavy chain phosphorylation. We used FRAP and FCS to observe the dynamics of Myo2 in live S. pombe cells and in cell extracts at different salt concentrations; both show that Myo2 with an N-terminal mEGFP tag has a diffusion coefficient of ∼ 3 µm2 s-1 in the cytoplasm of live cells during interphase and mitosis. Photon counting histogram analysis of the FCS data confirmed that Myo2 diffuses as doubled-headed molecules in the cytoplasm. FCS measurements on diluted cell extracts showed that mEGFP-Myo2 has a diffusion coefficient of ∼ 30 µm2 s-1 in 50 to 400 mM KCl concentrations.
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Affiliation(s)
- Janice E Friend
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103
| | - Wasim A Sayyad
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103
| | - Rajesh Arasada
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103
| | - Chad D McCormick
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8103.,Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892-1855
| | - John E Heuser
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8103
| | - Thomas D Pollard
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8103.,Department of Cell Biology, Yale University, New Haven, Connecticut 06520-8103
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36
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Arasada R, Sayyad WA, Berro J, Pollard TD. High-speed superresolution imaging of the proteins in fission yeast clathrin-mediated endocytic actin patches. Mol Biol Cell 2017; 29:295-303. [PMID: 29212877 PMCID: PMC5996959 DOI: 10.1091/mbc.e17-06-0415] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 11/28/2017] [Accepted: 11/28/2017] [Indexed: 12/31/2022] Open
Abstract
High-speed superresolution localization microscopy shows that actin filaments assemble in two zones in Schizosaccharomyces pombe actin patches, one around the base of the membrane invagination and another ~200 nm deeper into the cytoplasm. Both zones of actin filaments are important for elongation of the endocytic tubule and membrane scission To internalize nutrients and cell surface receptors via clathrin-mediated endocytosis, cells assemble at least 50 proteins, including clathrin, clathrin-interacting proteins, actin filaments, and actin binding proteins, in a highly ordered and regulated manner. The molecular mechanism by which actin filament polymerization deforms the cell membrane is unknown, largely due to lack of knowledge about the organization of the regulatory proteins and actin filaments. We used high-speed superresolution localization microscopy of live fission yeast cells to improve the spatial resolution to ∼35 nm with 1-s temporal resolution. The nucleation promoting factors Wsp1p (WASp) and Myo1p (myosin-I) define two independent pathways that recruit Arp2/3 complex, which assembles two zones of actin filaments. Myo1p concentrates at the site of endocytosis and initiates a zone of actin filaments assembled by Arp2/3 complex. Wsp1p appears simultaneously at this site but subsequently moves away from the cell surface as it stimulates Arp2/3 complex to assemble a second zone of actin filaments. Cells lacking either nucleation-promoting factor assemble only one, stationary, zone of actin filaments. These observations support our two-zone hypothesis to explain endocytic tubule elongation and vesicle scission in fission yeast.
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Affiliation(s)
- Rajesh Arasada
- Departments of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103
| | - Wasim A Sayyad
- Departments of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103
| | - Julien Berro
- Departments of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8103.,Department of Cell Biology, Yale University, New Haven, CT 06520-8103.,Nanobiology Institute, Yale University, New Haven, CT 06520-8103
| | - Thomas D Pollard
- Departments of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103 .,Departments of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8103.,Department of Cell Biology, Yale University, New Haven, CT 06520-8103
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37
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Akamatsu M, Lin Y, Bewersdorf J, Pollard TD. Analysis of interphase node proteins in fission yeast by quantitative and superresolution fluorescence microscopy. Mol Biol Cell 2017; 28:3203-3214. [PMID: 28539404 PMCID: PMC5687023 DOI: 10.1091/mbc.e16-07-0522] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 04/14/2017] [Accepted: 05/15/2017] [Indexed: 02/06/2023] Open
Abstract
We used quantitative confocal microscopy and FPALM superresolution microscopy of live fission yeast to investigate the structures and assembly of two types of interphase nodes-multiprotein complexes associated with the plasma membrane that merge together and mature into the precursors of the cytokinetic contractile ring. During the long G2 phase of the cell cycle, seven different interphase node proteins maintain constant concentrations as they accumulate in proportion to cell volume. During mitosis, the total numbers of type 1 node proteins (cell cycle kinases Cdr1p, Cdr2p, Wee1p, and anillin Mid1p) are constant even when the nodes disassemble. Quantitative measurements provide strong evidence that both types of nodes have defined sizes and numbers of constituent proteins, as observed for cytokinesis nodes. Type 1 nodes assemble in two phases-a burst at the end of mitosis, followed by steady increase during interphase to double the initial number. Type 2 nodes containing Blt1p, Rho-GEF Gef2p, and kinesin Klp8p remain intact throughout the cell cycle and are constituents of the contractile ring. They are released from the contractile ring as it disassembles and then associate with type 1 nodes around the equator of the cell during interphase.
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Affiliation(s)
- Matthew Akamatsu
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8103.,Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, CT 06520-8103
| | - Yu Lin
- Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, CT 06520-8103.,Department of Cell Biology, Yale University, New Haven, CT 06520-8103.,Department of Biomedical Engineering, Yale University, New Haven, CT 06520-8103
| | - Joerg Bewersdorf
- Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, CT 06520-8103.,Department of Biomedical Engineering, Yale University, New Haven, CT 06520-8103
| | - Thomas D Pollard
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103 .,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8103.,Department of Cell Biology, Yale University, New Haven, CT 06520-8103
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38
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Abstract
Experiments on model systems have revealed that cytokinesis in cells with contractile rings (amoebas, fungi, and animals) depends on shared molecular mechanisms in spite of some differences that emerged during a billion years of divergent evolution. Understanding these fundamental mechanisms depends on identifying the participating proteins and characterizing the mechanisms that position the furrow, assemble the contractile ring, anchor the ring to the plasma membrane, trigger ring constriction, produce force to form a furrow, disassemble the ring, expand the plasma membrane in the furrow, and separate the daughter cell membranes. This review reveals that fascinating questions remain about each step.
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Affiliation(s)
- Thomas D Pollard
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT
- Department of Cell Biology, Yale University, New Haven, CT
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39
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Pollard TD. A Third Look at the Structure of Leiomodin Bound to Actin. Biophys J 2017; 113:762-764. [PMID: 28834712 DOI: 10.1016/j.bpj.2017.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 07/18/2017] [Indexed: 11/30/2022] Open
Affiliation(s)
- Thomas D Pollard
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut; Department of Cell Biology, Yale University, New Haven, Connecticut.
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40
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Pollard TD. Tribute to Fumio Oosawa the pioneer in actin biophysics. Cytoskeleton (Hoboken) 2017; 74:446-449. [DOI: 10.1002/cm.21379] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 05/26/2017] [Indexed: 11/10/2022]
Affiliation(s)
- Thomas D. Pollard
- Department of Molecular Cellular and Developmental Biology; New Haven CT 06520-8103
- Department of Molecular Biophysics and Biochemistry; New Haven CT 06520-8103
- Department of Cell Biology; Yale University; New Haven CT 06520-8103
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41
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Abstract
Stimulated by our 2015 Current Biology paper [1], Zambon et al. reinvestigated how three myosin isoforms participate in the formation and constriction of the contractile ring in fission yeast. Our paper presented evidence that these myosin isoforms have distinct roles: "Conventional myosin-II Myo2 is crucial to ring assembly, unconventional myosin-II Myp2 is most important for ring constriction, and type V myosin Myo51 aids the other two myosins." Zambon et al. used different markers to reexamine the contributions of the three myosins to cytokinesis and concluded "that Myo2p is the major motor involved in ring contraction in S. pombe." Here, we show that most of the differences observed by Zambon et al. can be attributed to their use of the Rlc1p-3GFP marker, which genetically interacts with myo2-E1.
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Affiliation(s)
- Caroline Laplante
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | - Thomas D Pollard
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA; Department of Cell Biology, Yale University, New Haven, CT 06520, USA.
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42
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Anderson KL, Page C, Swift MF, Suraneni P, Janssen MEW, Pollard TD, Li R, Volkmann N, Hanein D. Redefining the Role of the Arp2/3 Complex: Regulation of Morphology at the Leading Edge. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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43
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Thiyagarajan S, Chin H, Karatekin E, Pollard TD, O'Shaughnessy B. Fission Yeast Contractile Ring Tension Increases ∼2-Fold Throughout Constriction and Regulates Septum Closure but does not Set the Constriction Rate. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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44
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Anderson KL, Page C, Swift MF, Suraneni P, Janssen MEW, Pollard TD, Li R, Volkmann N, Hanein D. Nano-scale actin-network characterization of fibroblast cells lacking functional Arp2/3 complex. J Struct Biol 2016; 197:312-321. [PMID: 28013022 DOI: 10.1016/j.jsb.2016.12.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Accepted: 12/18/2016] [Indexed: 01/06/2023]
Abstract
Arp2/3 complex is thought to be the primary protrusive force generator in cell migration by controlling the assembly and turnover of the branched filament network that pushes the leading edge of moving cells forward. However, mouse fibroblasts without functional Arp2/3 complex migrate at rates similar to wild-type cells, contradicting this paradigm. We show by correlative fluorescence and large-scale cryo-tomography studies combined with automated actin-network analysis that the absence of functional Arp2/3 complex has profound effects on the nano-scale architecture of actin networks. Our quantitative analysis at the single-filament level revealed that cells lacking functional Arp2/3 complex fail to regulate location-dependent fine-tuning of actin filament growth and organization that is distinct from its role in the formation and regulation of dendritic actin networks.
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Affiliation(s)
- Karen L Anderson
- Bioinformatics and Structural Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA, United States
| | - Christopher Page
- Bioinformatics and Structural Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA, United States
| | - Mark F Swift
- Bioinformatics and Structural Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA, United States
| | - Praveen Suraneni
- Department of Cell Biology, Johns Hopkins School of Medicine, Baltimore, MD, United States
| | - Mandy E W Janssen
- Bioinformatics and Structural Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA, United States
| | - Thomas D Pollard
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, United States; Department of Cell Biology and of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, United States
| | - Rong Li
- Department of Cell Biology, Johns Hopkins School of Medicine, Baltimore, MD, United States
| | - Niels Volkmann
- Bioinformatics and Structural Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA, United States.
| | - Dorit Hanein
- Bioinformatics and Structural Biology Program, Sanford-Burnham Medical Research Institute, La Jolla, CA, United States.
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45
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Noble DB, Mochrie SGJ, O'Hern CS, Pollard TD, Regan L. Promoting convergence: The integrated graduate program in physical and engineering biology at Yale University, a new model for graduate education. Biochem Mol Biol Educ 2016; 44:537-549. [PMID: 27292366 PMCID: PMC5132113 DOI: 10.1002/bmb.20977] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 03/28/2016] [Indexed: 06/01/2023]
Abstract
In 2008, we established the Integrated Graduate Program in Physical and Engineering Biology (IGPPEB) at Yale University. Our goal was to create a comprehensive graduate program to train a new generation of scientists who possess a sophisticated understanding of biology and who are capable of applying physical and quantitative methodologies to solve biological problems. Here we describe the framework of the training program, report on its effectiveness, and also share the insights we gained during its development and implementation. The program features co-teaching by faculty with complementary specializations, student peer learning, and novel hands-on courses that facilitate the seamless blending of interdisciplinary research and teaching. It also incorporates enrichment activities to improve communication skills, engage students in science outreach, and foster a cohesive program cohort, all of which promote the development of transferable skills applicable in a variety of careers. The curriculum of the graduate program is integrated with the curricular requirements of several Ph.D.-granting home programs in the physical, engineering, and biological sciences. Moreover, the wide-ranging recruiting activities of the IGPPEB serve to enhance the quality and diversity of students entering graduate school at Yale. We also discuss some of the challenges we encountered in establishing and optimizing the program, and describe the institution-level changes that were catalyzed by the introduction of the new graduate program. The goal of this article is to serve as both an inspiration and as a practical "how to" manual for those who seek to establish similar programs at their own institutions. © 2016 by The International Union of Biochemistry and Molecular Biology, 44(6):537-549, 2016.
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Affiliation(s)
- Dorottya B. Noble
- Integrated Graduate Program in Physical and Engineering Biology
- Department of Molecular Biophysics and Biochemistry
| | - Simon G. J. Mochrie
- Integrated Graduate Program in Physical and Engineering Biology
- Department of Physics
- Department of Applied Physics
| | - Corey S. O'Hern
- Integrated Graduate Program in Physical and Engineering Biology
- Department of Physics
- Department of Applied Physics
- Department of Mechanical Engineering and Materials Science
- Graduate Program in Computational Biology and Bioinformatics
| | - Thomas D. Pollard
- Integrated Graduate Program in Physical and Engineering Biology
- Department of Molecular Biophysics and Biochemistry
- Department of Molecular, Cellular, and Developmental Biology
- Department of Cell Biology
| | - Lynne Regan
- Integrated Graduate Program in Physical and Engineering Biology
- Department of Molecular Biophysics and Biochemistry
- Graduate Program in Computational Biology and Bioinformatics
- Department of Chemistry, Yale UniversityNew HavenConnecticut 06520USA
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46
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Antonny B, Burd C, De Camilli P, Chen E, Daumke O, Faelber K, Ford M, Frolov VA, Frost A, Hinshaw JE, Kirchhausen T, Kozlov MM, Lenz M, Low HH, McMahon H, Merrifield C, Pollard TD, Robinson PJ, Roux A, Schmid S. Membrane fission by dynamin: what we know and what we need to know. EMBO J 2016; 35:2270-2284. [PMID: 27670760 PMCID: PMC5090216 DOI: 10.15252/embj.201694613] [Citation(s) in RCA: 313] [Impact Index Per Article: 39.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 07/25/2016] [Indexed: 12/04/2022] Open
Abstract
The large GTPase dynamin is the first protein shown to catalyze membrane fission. Dynamin and its related proteins are essential to many cell functions, from endocytosis to organelle division and fusion, and it plays a critical role in many physiological functions such as synaptic transmission and muscle contraction. Research of the past three decades has focused on understanding how dynamin works. In this review, we present the basis for an emerging consensus on how dynamin functions. Three properties of dynamin are strongly supported by experimental data: first, dynamin oligomerizes into a helical polymer; second, dynamin oligomer constricts in the presence of GTP; and third, dynamin catalyzes membrane fission upon GTP hydrolysis. We present the two current models for fission, essentially diverging in how GTP energy is spent. We further discuss how future research might solve the remaining open questions presently under discussion.
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Affiliation(s)
- Bruno Antonny
- CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice Sophia-Antipolis, Valbonne, France
| | - Christopher Burd
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Pietro De Camilli
- Departments of Neuroscience and Cell Biology, Howard Hughes Medical Institute and Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, USA
| | - Elizabeth Chen
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Oliver Daumke
- Department of Crystallography, Max-Delbrück Centrum für Molekulare Medizin, Berlin, Germany
| | - Katja Faelber
- Department of Crystallography, Max-Delbrück Centrum für Molekulare Medizin, Berlin, Germany
| | - Marijn Ford
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Vadim A Frolov
- Biofisika Institute (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, Leioa, Spain.,IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - Adam Frost
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Jenny E Hinshaw
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD, USA
| | - Tom Kirchhausen
- Departments of Cell Biology and Pediatrics, Harvard Medical School, Boston, MA, USA.,Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
| | - Michael M Kozlov
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Martin Lenz
- LPTMS, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Orsay, France
| | - Harry H Low
- Department of Life Sciences, Imperial College, London, UK
| | | | | | - Thomas D Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Phillip J Robinson
- Cell Signalling Unit, Children's Medical Research Institute, The University of Sydney, Westmead, NSW, Australia
| | - Aurélien Roux
- Department of Biochemistry and Swiss NCCR Chemical Biology, University of Geneva, Geneva 4, Switzerland
| | - Sandra Schmid
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
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47
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Abstract
Growth cones on neuronal process navigate over long distances to their targets in the developing nervous system. New work by Menon et al., 2015 in the current issue of Developmental Cell reveals that reversible ubiquitination of the actin filament polymerase called VASP is part of the guidance system.
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Affiliation(s)
- Thomas D Pollard
- Departments of Molecular Cellular and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA; Departments of Molecular Biophysics and Biochemistry, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA; Department of Cell Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA.
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48
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Pu KM, Akamatsu M, Pollard TD. The septation initiation network controls the assembly of nodes containing Cdr2p for cytokinesis in fission yeast. J Cell Sci 2016; 128:441-6. [PMID: 25501814 DOI: 10.1242/jcs.160077] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the fission yeast Schizosaccharomyces pombe, cortical protein structures called interphase nodes help to prepare the cell for cytokinesis by positioning precursors of the cytokinetic contractile ring, and the septation initiation network (SIN) regulates the onset of cytokinesis and septum formation. Previous work has noted that one type of interphase node disappears during mitosis providing SIN activity is high. Here, we used time-lapse fluorescence microscopy to provide evidence that SIN activity is necessary and sufficient to disperse the type 1 node proteins Cdr2p and Mid1p into the cytoplasm, so these nodes assemble only during interphase through early mitosis when SIN activity is low. Activating the SIN in interphase cells dispersed Cdr2p and anillin Mid1p from type 1 nodes a few min after the SIN kinase Cdc7p–GFP accumulated at spindle pole bodies. If the SIN was then turned off in interphase cells, Cdr2p and Mid1p reappeared in nodes in parallel with the decline in SIN activity. Hyperactivating SIN during mitosis dispersed type 1 nodes earlier than normal, and prolonged SIN activation prevented nodes from reforming at the end of mitosis.
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Affiliation(s)
- Ben O'Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA.
| | - Thomas D Pollard
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
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Wang S, Chin HF, Karatekin E, Pollard TD, O'Shaughnessy B. Two Isoforms of Myosin-II Account for the Tension of the Fission Yeast Cytokinetic Ring. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.3317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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