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  1. AU=Forth Scott
  2. AU="Kreutzer, Susanne" AU="Kreutzer, Susanne"
  3. AU="St John, Maie"
  4. AU=Gerhardy A
  5. AU="Qi, Huixin"
  6. AU="Dobosiewicz, May"
  7. AU="Srivastava, Rakesh"
  8. AU="Grevtsov K.I."

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  1. Artikel ; Online: Directly Measuring Forces within Reconstituted Active Microtubule Bundles.

    Palumbo, Jacob / Tai, Ellinor / Forth, Scott

    Journal of visualized experiments : JoVE

    2022  , Heft 183

    Abstract: Microtubule networks are employed in cells to accomplish a wide range of tasks, ranging from acting as tracks for vesicle transport to working as specialized arrays during mitosis to regulate chromosome segregation. Proteins that interact with ... ...

    Abstract Microtubule networks are employed in cells to accomplish a wide range of tasks, ranging from acting as tracks for vesicle transport to working as specialized arrays during mitosis to regulate chromosome segregation. Proteins that interact with microtubules include motors such as kinesins and dynein, which can generate active forces and directional motion, as well as non-motor proteins that crosslink filaments into higher-order networks or regulate filament dynamics. To date, biophysical studies of microtubule-associated proteins have overwhelmingly focused on the role of single motor proteins needed for vesicle transport, and significant progress has been made in elucidating the force-generating properties and mechanochemical regulation of kinesins and dyneins. However, for processes in which microtubules act both as cargo and track, such as during filament sliding within the mitotic spindle, much less is understood about the biophysical regulation of ensembles of the crosslinking proteins involved. Here, we detail our methodology for directly probing force generation and response within crosslinked microtubule minimal networks reconstituted from purified microtubules and mitotic proteins. Microtubule pairs are crosslinked by proteins of interest, one microtubule is immobilized to a microscope coverslip, and the second microtubule is manipulated by an optical trap. Simultaneous total internal reflection fluorescence microscopy allows for multichannel visualization of all the components of this microtubule network as the filaments slide apart to generate force. We also demonstrate how these techniques can be used to probe pushing forces exerted by kinesin-5 ensembles and how viscous braking forces arise between sliding microtubule pairs crosslinked by the mitotic MAP PRC1. These assays provide insights into the mechanisms of spindle assembly and function and can be more broadly adapted to study dense microtubule network mechanics in diverse contexts, such as the axon and dendrites of neurons and polar epithelial cells.
    Mesh-Begriff(e) Dyneins/metabolism ; Kinesins ; Microtubule-Associated Proteins/metabolism ; Microtubules/metabolism ; Spindle Apparatus/metabolism
    Chemische Substanzen Microtubule-Associated Proteins ; Dyneins (EC 3.6.4.2) ; Kinesins (EC 3.6.4.4)
    Sprache Englisch
    Erscheinungsdatum 2022-05-10
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Video-Audio Media ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 2259946-0
    ISSN 1940-087X ; 1940-087X
    ISSN (online) 1940-087X
    ISSN 1940-087X
    DOI 10.3791/63819
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  2. Artikel ; Online: Two modes of PRC1-mediated mechanical resistance to kinesin-driven microtubule network disruption.

    Alfieri, Angus / Gaska, Ignas / Forth, Scott

    Current biology : CB

    2021  Band 31, Heft 12, Seite(n) 2495–2506.e4

    Abstract: The proper organization of the microtubule-based spindle during cell division requires the collective activity of many different proteins. These include non-motor microtubule-associated proteins (MAPs), whose functions include crosslinking microtubules ... ...

    Abstract The proper organization of the microtubule-based spindle during cell division requires the collective activity of many different proteins. These include non-motor microtubule-associated proteins (MAPs), whose functions include crosslinking microtubules to regulate filament sliding rates and assemble microtubule arrays. One such protein is PRC1, an essential MAP that has been shown to preferentially crosslink overlapping antiparallel microtubules at the spindle midzone. PRC1 has been proposed to act as a molecular brake, but insight into the mechanism of how PRC1 molecules function cooperatively to resist motor-driven microtubule sliding and to allow for the formation of stable midzone overlaps remains unclear. Here, we employ a modified microtubule gliding assay to rupture PRC1-mediated microtubule pairs using surface-bound kinesins. We discovered that PRC1 crosslinks always reduce bundled filament sliding velocities relative to single-microtubule gliding rates and do so via two distinct emergent modes of mechanical resistance to motor-driven sliding. We term these behaviors braking and coasting, where braking events exhibit substantially slowed microtubule sliding compared to coasting events. Strikingly, braking behavior requires the formation of two distinct high-density clusters of PRC1 molecules near microtubule tips. Our results suggest a cooperative mechanism for PRC1 accumulation when under mechanical load that leads to a unique state of enhanced resistance to filament sliding and provides insight into collective protein ensemble behavior in regulating the mechanics of spindle assembly.
    Mesh-Begriff(e) Cell Cycle Proteins/metabolism ; Humans ; Kinesins/metabolism ; Microtubule-Associated Proteins/metabolism ; Microtubules/metabolism ; Spindle Apparatus/chemistry ; Spindle Apparatus/metabolism
    Chemische Substanzen Cell Cycle Proteins ; Microtubule-Associated Proteins ; PRC1 protein, human ; Kinesins (EC 3.6.4.4)
    Sprache Englisch
    Erscheinungsdatum 2021-04-12
    Erscheinungsland England
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1071731-6
    ISSN 1879-0445 ; 0960-9822
    ISSN (online) 1879-0445
    ISSN 0960-9822
    DOI 10.1016/j.cub.2021.03.034
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  3. Artikel ; Online: The mechanics of microtubule networks in cell division.

    Forth, Scott / Kapoor, Tarun M

    The Journal of cell biology

    2017  Band 216, Heft 6, Seite(n) 1525–1531

    Abstract: The primary goal of a dividing somatic cell is to accurately and equally segregate its genome into two new daughter cells. In eukaryotes, this process is performed by a self-organized structure called the mitotic spindle. It has long been appreciated ... ...

    Abstract The primary goal of a dividing somatic cell is to accurately and equally segregate its genome into two new daughter cells. In eukaryotes, this process is performed by a self-organized structure called the mitotic spindle. It has long been appreciated that mechanical forces must be applied to chromosomes. At the same time, the network of microtubules in the spindle must be able to apply and sustain large forces to maintain spindle integrity. Here we consider recent efforts to measure forces generated within microtubule networks by ensembles of key proteins. New findings, such as length-dependent force generation, protein clustering by asymmetric friction, and entropic expansion forces will help advance models of force generation needed for spindle function and maintaining integrity.
    Mesh-Begriff(e) Animals ; Cell Division ; Humans ; Mechanotransduction, Cellular ; Microtubule Proteins/metabolism ; Microtubules/metabolism ; Microtubules/physiology ; Spindle Apparatus/metabolism ; Spindle Apparatus/physiology ; Stress, Mechanical
    Chemische Substanzen Microtubule Proteins
    Sprache Englisch
    Erscheinungsdatum 2017-06-05
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Review
    ZDB-ID 218154-x
    ISSN 1540-8140 ; 0021-9525
    ISSN (online) 1540-8140
    ISSN 0021-9525
    DOI 10.1083/jcb.201612064
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  4. Artikel ; Online: The Mitotic Crosslinking Protein PRC1 Acts Like a Mechanical Dashpot to Resist Microtubule Sliding.

    Gaska, Ignas / Armstrong, Mason E / Alfieri, April / Forth, Scott

    Developmental cell

    2020  Band 54, Heft 3, Seite(n) 367–378.e5

    Abstract: Cell division in eukaryotes requires the regulated assembly of the spindle apparatus. The proper organization of microtubules within the spindle is driven by motor proteins that exert forces to slide filaments, whereas non-motor proteins crosslink ... ...

    Abstract Cell division in eukaryotes requires the regulated assembly of the spindle apparatus. The proper organization of microtubules within the spindle is driven by motor proteins that exert forces to slide filaments, whereas non-motor proteins crosslink filaments into higher-order motifs, such as overlapping bundles. It is not clear how active and passive forces are integrated to produce regulated mechanical outputs within spindles. Here, we employ simultaneous optical trapping and total internal reflection fluorescence (TIRF) microscopy to directly measure the frictional forces produced by the mitotic crosslinking protein PRC1 that resist microtubule sliding. These forces scale with microtubule sliding velocity and the number of PRC1 crosslinks but do not depend on overlap length or PRC1 density within overlaps. Our results suggest that PRC1 ensembles act similarly to a mechanical dashpot, producing significant resistance against fast motions but minimal resistance against slow motions, allowing for the integration of diverse motor activities into a single mechanical outcome.
    Mesh-Begriff(e) Cell Cycle Proteins/genetics ; Cell Cycle Proteins/metabolism ; HeLa Cells ; Humans ; Kinesin/metabolism ; Microtubules/genetics ; Microtubules/metabolism ; Mitosis/physiology ; Spindle Apparatus/genetics ; Spindle Apparatus/metabolism
    Chemische Substanzen Cell Cycle Proteins ; PRC1 protein, human ; Kinesin (EC 3.6.4.4)
    Sprache Englisch
    Erscheinungsdatum 2020-07-07
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2054967-2
    ISSN 1878-1551 ; 1534-5807
    ISSN (online) 1878-1551
    ISSN 1534-5807
    DOI 10.1016/j.devcel.2020.06.017
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  5. Artikel ; Online: The kinesin-5 tail and bipolar minifilament domains are the origin of its microtubule crosslinking and sliding activity.

    Nithianantham, Stanley / Iwanski, Malina K / Gaska, Ignas / Pandey, Himanshu / Bodrug, Tatyana / Inagaki, Sayaka / Major, Jennifer / Brouhard, Gary J / Gheber, Larissa / Rosenfeld, Steven S / Forth, Scott / Hendricks, Adam G / Al-Bassam, Jawdat

    Molecular biology of the cell

    2023  Band 34, Heft 11, Seite(n) ar111

    Abstract: Kinesin-5 crosslinks and slides apart microtubules to assemble, elongate, and maintain the mitotic spindle. Kinesin-5 is a tetramer, where two N-terminal motor domains are positioned at each end of the motor, and the coiled-coil stalk domains are ... ...

    Abstract Kinesin-5 crosslinks and slides apart microtubules to assemble, elongate, and maintain the mitotic spindle. Kinesin-5 is a tetramer, where two N-terminal motor domains are positioned at each end of the motor, and the coiled-coil stalk domains are organized into a tetrameric bundle through the bipolar assembly (BASS) domain. To dissect the function of the individual structural elements of the motor, we constructed a minimal kinesin-5 tetramer (mini-tetramer). We determined the x-ray structure of the extended, 34-nm BASS domain. Guided by these structural studies, we generated active bipolar kinesin-5 mini-tetramer motors from
    Mesh-Begriff(e) Humans ; Animals ; Kinesins ; Microtubules ; Spindle Apparatus ; Cluster Analysis ; Drosophila
    Chemische Substanzen Kinesins (EC 3.6.4.4)
    Sprache Englisch
    Erscheinungsdatum 2023-08-23
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 1098979-1
    ISSN 1939-4586 ; 1059-1524
    ISSN (online) 1939-4586
    ISSN 1059-1524
    DOI 10.1091/mbc.E23-07-0287
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  6. Buch ; Audio / Video: The purpose of generating fatigue crack growth threshold data

    Forth, Scott

    2006  

    Verfasserangabe Scott Forth
    Sprache Englisch
    Umfang 1 CD-ROM (16 S.)
    Verlag National Technical Information Service
    Erscheinungsort Springfield, Va
    Dokumenttyp Buch ; Audio / Video
    Anmerkung Enth. nur Präsentationsfolien, keinen ausgearb. Vortrag ; In Datenbanken fälschlicherweise "First International Conference for Smart Systems and Robotics in Space and Medicine" als Titel angegeben
    Datenquelle Katalog der Technische Informationsbibliothek Hannover

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  7. Artikel ; Online: Measuring Pushing and Braking Forces Generated by Ensembles of Kinesin-5 Crosslinking Two Microtubules.

    Shimamoto, Yuta / Forth, Scott / Kapoor, Tarun M

    Developmental cell

    2015  Band 34, Heft 6, Seite(n) 669–681

    Abstract: The proper organization of the microtubule-based mitotic spindle is proposed to depend on nanometer-sized motor proteins generating forces that scale with a micron-sized geometric feature, such as microtubule overlap length. However, it is unclear ... ...

    Abstract The proper organization of the microtubule-based mitotic spindle is proposed to depend on nanometer-sized motor proteins generating forces that scale with a micron-sized geometric feature, such as microtubule overlap length. However, it is unclear whether such regulation can be achieved by any mitotic motor protein. Here, we employ an optical-trap- and total internal reflection fluorescence (TIRF)-based assay to show that ensembles of kinesin-5, a conserved mitotic motor protein, can push apart overlapping antiparallel microtubules to generate a force whose magnitude scales with filament overlap length. We also find that kinesin-5 can produce overlap-length-dependent "brake-like" resistance against relative microtubule sliding in both parallel and antiparallel geometries, an activity that has been suggested by cell biological studies but had not been directly measured. Together, these findings, along with numerical simulations, reveal how a motor protein can function as an analog converter, "reading" simple geometric and dynamic features in cytoskeletal networks to produce regulated force outputs.
    Mesh-Begriff(e) Animals ; Cross-Linking Reagents/metabolism ; Kinesin/metabolism ; Microscopy, Fluorescence ; Microtubules/metabolism ; Spindle Apparatus/physiology ; Xenopus Proteins/metabolism ; Xenopus laevis/growth & development ; Xenopus laevis/metabolism
    Chemische Substanzen Cross-Linking Reagents ; KIF11 protein, Xenopus ; Xenopus Proteins ; Kinesin (EC 3.6.4.4)
    Sprache Englisch
    Erscheinungsdatum 2015-09-28
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 2054967-2
    ISSN 1878-1551 ; 1534-5807
    ISSN (online) 1878-1551
    ISSN 1534-5807
    DOI 10.1016/j.devcel.2015.08.017
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  8. Artikel: Substrate-Enzyme Interactions in Intramembrane Proteolysis: γ-Secretase as the Prototype.

    Liu, Xinyue / Zhao, Jing / Zhang, Yingkai / Ubarretxena-Belandia, Iban / Forth, Scott / Lieberman, Raquel L / Wang, Chunyu

    Frontiers in molecular neuroscience

    2020  Band 13, Seite(n) 65

    Abstract: Intramembrane-cleaving proteases (I-CLiPs) catalyze the hydrolysis of peptide bonds within the transmembrane regions of membrane protein substrates, releasing bioactive fragments that play roles in many physiological and pathological processes. Based on ... ...

    Abstract Intramembrane-cleaving proteases (I-CLiPs) catalyze the hydrolysis of peptide bonds within the transmembrane regions of membrane protein substrates, releasing bioactive fragments that play roles in many physiological and pathological processes. Based on their catalytic mechanism and nucleophile, I-CLiPs are classified into metallo, serine, aspartyl, and glutamyl proteases. Presenilin is the most prominent among I-CLiPs, as the catalytic subunit of γ-secretase (GS) complex responsible for cleaving the amyloid precursor protein (APP) and Notch, as well as many other membrane substrates. Recent cryo-electron microscopy (cryo-EM) structures of GS provide new details on how presenilin recognizes and cleaves APP and Notch. First, presenilin transmembrane helix (TM) 2 and 6 are dynamic. Second, upon binding to GS, the substrate TM helix is unwound from the C-terminus, resulting in an intermolecular β-sheet between the substrate and presenilin. The transition of the substrate C-terminus from α-helix to β-sheet is proposed to expose the scissile peptide bond in an extended conformation, leaving it susceptible to protease cleavage. Despite the astounding new insights in recent years, many crucial questions remain unanswered regarding the inner workings of γ-secretase, however. Key unanswered questions include how the enzyme recognizes and recruits substrates, how substrates are translocated from an initial docking site to the active site, how active site aspartates recruit and coordinate catalytic water, and the nature of the mechanisms of processive trimming of the substrate and product release. Answering these questions will have important implications for drug discovery aimed at selectively reducing the amyloid load in Alzheimer's disease (AD) with minimal side effects.
    Sprache Englisch
    Erscheinungsdatum 2020-05-19
    Erscheinungsland Switzerland
    Dokumenttyp Journal Article ; Review
    ZDB-ID 2452967-9
    ISSN 1662-5099
    ISSN 1662-5099
    DOI 10.3389/fnmol.2020.00065
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  9. Artikel ; Online: High-resolution imaging reveals how the spindle midzone impacts chromosome movement.

    Pamula, Melissa C / Carlini, Lina / Forth, Scott / Verma, Priyanka / Suresh, Subbulakshmi / Legant, Wesley R / Khodjakov, Alexey / Betzig, Eric / Kapoor, Tarun M

    The Journal of cell biology

    2019  Band 218, Heft 8, Seite(n) 2529–2544

    Abstract: In the spindle midzone, microtubules from opposite half-spindles form bundles between segregating chromosomes. Microtubule bundles can either push or restrict chromosome movement during anaphase in different cellular contexts, but how these activities ... ...

    Abstract In the spindle midzone, microtubules from opposite half-spindles form bundles between segregating chromosomes. Microtubule bundles can either push or restrict chromosome movement during anaphase in different cellular contexts, but how these activities are achieved remains poorly understood. Here, we use high-resolution live-cell imaging to analyze individual microtubule bundles, growing filaments, and chromosome movement in dividing human cells. Within bundles, filament overlap length marked by the cross-linking protein PRC1 decreases during anaphase as chromosome segregation slows. Filament ends within microtubule bundles appear capped despite dynamic PRC1 turnover and submicrometer proximity to growing microtubules. Chromosome segregation distance and rate are increased in two human cell lines when microtubule bundle assembly is prevented via PRC1 knockdown. Upon expressing a mutant PRC1 with reduced microtubule affinity, bundles assemble but chromosome hypersegregation is still observed. We propose that microtubule overlap length reduction, typically linked to pushing forces generated within filament bundles, is needed to properly restrict spindle elongation and position chromosomes within daughter cells.
    Mesh-Begriff(e) Anaphase ; Cell Cycle Proteins/metabolism ; Chromosome Segregation ; Chromosomes, Human/metabolism ; Fluorescence Recovery After Photobleaching ; HeLa Cells ; Humans ; Imaging, Three-Dimensional ; Microtubule-Associated Proteins/metabolism ; Microtubules/metabolism ; Movement ; Mutation/genetics ; Spindle Apparatus/metabolism
    Chemische Substanzen Cell Cycle Proteins ; MAPRE1 protein, human ; Microtubule-Associated Proteins ; PRC1 protein, human
    Sprache Englisch
    Erscheinungsdatum 2019-06-27
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 218154-x
    ISSN 1540-8140 ; 0021-9525
    ISSN (online) 1540-8140
    ISSN 0021-9525
    DOI 10.1083/jcb.201904169
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  10. Artikel ; Online: Asymmetric friction of nonmotor MAPs can lead to their directional motion in active microtubule networks.

    Forth, Scott / Hsia, Kuo-Chiang / Shimamoto, Yuta / Kapoor, Tarun M

    Cell

    2014  Band 157, Heft 2, Seite(n) 420–432

    Abstract: Diverse cellular processes require microtubules to be organized into distinct structures, such as asters or bundles. Within these dynamic motifs, microtubule-associated proteins (MAPs) are frequently under load, but how force modulates these proteins' ... ...

    Abstract Diverse cellular processes require microtubules to be organized into distinct structures, such as asters or bundles. Within these dynamic motifs, microtubule-associated proteins (MAPs) are frequently under load, but how force modulates these proteins' function is poorly understood. Here, we combine optical trapping with TIRF-based microscopy to measure the force dependence of microtubule interaction for three nonmotor MAPs (NuMA, PRC1, and EB1) required for cell division. We find that frictional forces increase nonlinearly with MAP velocity across microtubules and depend on filament polarity, with NuMA's friction being lower when moving toward minus ends, EB1's lower toward plus ends, and PRC1's exhibiting no directional preference. Mathematical models predict, and experiments confirm, that MAPs with asymmetric friction can move directionally within actively moving microtubule pairs they crosslink. Our findings reveal how nonmotor MAPs can generate frictional resistance in dynamic cytoskeletal networks via micromechanical adaptations whose anisotropy may be optimized for MAP localization and function within cellular structures.
    Mesh-Begriff(e) Antigens, Nuclear/chemistry ; Antigens, Nuclear/metabolism ; Biomechanical Phenomena ; Cell Cycle Proteins/chemistry ; Cell Cycle Proteins/metabolism ; Microscopy, Fluorescence ; Microtubule-Associated Proteins/chemistry ; Microtubule-Associated Proteins/metabolism ; Microtubules/metabolism ; Models, Biological ; Nuclear Matrix-Associated Proteins/chemistry ; Nuclear Matrix-Associated Proteins/metabolism ; Optical Tweezers
    Chemische Substanzen Antigens, Nuclear ; Cell Cycle Proteins ; MAPRE1 protein, human ; Microtubule-Associated Proteins ; NUMA1 protein, human ; Nuclear Matrix-Associated Proteins ; PRC1 protein, human
    Sprache Englisch
    Erscheinungsdatum 2014-04-11
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 187009-9
    ISSN 1097-4172 ; 0092-8674
    ISSN (online) 1097-4172
    ISSN 0092-8674
    DOI 10.1016/j.cell.2014.02.018
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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