1
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Shultz KD, Al Anbari YF, Wright NT. I told you to stop: obscurin's role in epithelial cell migration. Biochem Soc Trans 2024; 52:1947-1956. [PMID: 39051125 DOI: 10.1042/bst20240564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2024] [Revised: 07/02/2024] [Accepted: 07/11/2024] [Indexed: 07/27/2024]
Abstract
The giant cytoskeletal protein obscurin contains multiple cell signaling domains that influence cell migration. Here, we follow each of these pathways, examine how these pathways modulate epithelial cell migration, and discuss the cross-talk between these pathways. Specifically, obscurin uses its PH domain to inhibit phosphoinositide-3-kinase (PI3K)-dependent migration and its RhoGEF domain to activate RhoA and slow cell migration. While obscurin's effect on the PI3K pathway agrees with the literature, obscurin's effect on the RhoA pathway runs counter to most other RhoA effectors, whose activation tends to lead to enhanced motility. Obscurin also phosphorylates cadherins, and this may also influence cell motility. When taken together, obscurin's ability to modulate three independent cell migration pathways is likely why obscurin knockout cells experience enhanced epithelial to mesenchymal transition, and why obscurin is a frequently mutated gene in several types of cancer.
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Affiliation(s)
- Kamrin D Shultz
- Department of Chemistry and Biochemistry, James Madison University, 901 Carrier Dr., Harrisonburg, VA 22807, U.S.A
| | - Yasmin F Al Anbari
- Department of Chemistry and Biochemistry, James Madison University, 901 Carrier Dr., Harrisonburg, VA 22807, U.S.A
| | - Nathan T Wright
- Department of Chemistry and Biochemistry, James Madison University, 901 Carrier Dr., Harrisonburg, VA 22807, U.S.A
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2
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McInally SG, Reading AJB, Rosario A, Jelenkovic PR, Goode BL, Kondev J. Length control emerges from cytoskeletal network geometry. Proc Natl Acad Sci U S A 2024; 121:e2401816121. [PMID: 39106306 PMCID: PMC11331072 DOI: 10.1073/pnas.2401816121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Accepted: 06/21/2024] [Indexed: 08/09/2024] Open
Abstract
Many cytoskeletal networks consist of individual filaments that are organized into elaborate higher-order structures. While it is appreciated that the size and architecture of these networks are critical for their biological functions, much of the work investigating control over their assembly has focused on mechanisms that regulate the turnover of individual filaments through size-dependent feedback. Here, we propose a very different, feedback-independent mechanism to explain how yeast cells control the length of their actin cables. Our findings, supported by quantitative cell imaging and mathematical modeling, indicate that actin cable length control is an emergent property that arises from the cross-linked and bundled organization of the filaments within the cable. Using this model, we further dissect the mechanisms that allow cables to grow longer in larger cells and propose that cell length-dependent tuning of formin activity allows cells to scale cable length with cell length. This mechanism is a significant departure from prior models of cytoskeletal filament length control and presents a different paradigm to consider how cells control the size, shape, and dynamics of higher-order cytoskeletal structures.
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Affiliation(s)
- Shane G. McInally
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA01609
| | | | - Aldric Rosario
- Department of Physics, Brandeis University, Waltham, MA02454
| | | | - Bruce L. Goode
- Department of Biology, Brandeis University, Waltham, MA02454
| | - Jane Kondev
- Department of Physics, Brandeis University, Waltham, MA02454
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3
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De Belly H, Weiner OD. Follow the flow: Actin and membrane act as an integrated system to globally coordinate cell shape and movement. Curr Opin Cell Biol 2024; 89:102392. [PMID: 38991476 DOI: 10.1016/j.ceb.2024.102392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 06/01/2024] [Accepted: 06/06/2024] [Indexed: 07/13/2024]
Abstract
Migratory cells are polarized with protrusive fronts and contractile rears. This spatial organization necessitates long-range coordination of the signals that organize protrusions and contractions. Cells leverage reciprocal interactions of short-range biochemical signals and long-range mechanical forces for this integration. The interface between the plasma membrane and actin cortex is where this communication occurs. Here, we review how the membrane and cortex form an integrated system for long-range coordination of cell polarity. We highlight the role of membrane-to-cortex-attachment proteins as regulators of tension transmission across the cell and discuss the interplay between actin-membrane and polarity signaling complexes. Rather than presenting an exhaustive list of recent findings, we focus on important gaps in our current understanding.
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Affiliation(s)
- Henry De Belly
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA; Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA.
| | - Orion D Weiner
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA; Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA.
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4
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Hachem Z, Hadrian C, Aldbaisi L, Alkaabi M, Wan LQ, Fan J. Asymmetrical positioning of cell organelles reflects the cell chirality of mouse myoblast cells. APL Bioeng 2024; 8:016119. [PMID: 38495528 PMCID: PMC10942803 DOI: 10.1063/5.0189401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 03/04/2024] [Indexed: 03/19/2024] Open
Abstract
Cell chirality is crucial for the chiral morphogenesis of biological tissues, yet its underlying mechanism remains unclear. Cell organelle polarization along multiple axes in a cell body, namely, apical-basal, front-rear, and left-right, is known to direct cell behavior such as orientation, rotation, and migration. Among these axes, the left-right bias holds significant sway in determining the chiral directionality of these behaviors. Normally, mouse myoblast (C2C12) cells exhibit a strong counterclockwise chirality on a ring-shaped micropattern, whereas they display a clockwise dominant chirality under Latrunculin A treatment. To investigate the relationship between multicellular chirality and organelle positioning in single cells, we studied the left-right positioning of cell organelles under distinct cell chirality in single cells via micropatterning technique, fluorescent microscopy, and imaging analysis. We found that on a "T"-shaped micropattern, a C2C12 cell adopts a triangular shape, with its nucleus-centrosome axis pointing toward the top-right direction of the "T." Several other organelles, including the Golgi apparatus, lysosomes, actin filaments, and microtubules, showed a preference to polarize on one side of the axis, indicating the universality of the left-right asymmetrical organelle positioning. Interestingly, upon reversing cell chirality with Latrunculin A, the organelles correspondingly reversed their left-right positioning bias, as suggested by the consistently biased metabolism and contractile properties at the leading edge. This left-right asymmetry in organelle positioning may help predict cell migration direction and serve as a potential marker for identifying cell chirality in biological models.
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Affiliation(s)
- Zeina Hachem
- Department of Natural Sciences, CASL, University of Michigan-Dearborn, Dearborn, Michigan 48128, USA
| | - Courtney Hadrian
- Department of Natural Sciences, CASL, University of Michigan-Dearborn, Dearborn, Michigan 48128, USA
| | - Lina Aldbaisi
- Department of Natural Sciences, CASL, University of Michigan-Dearborn, Dearborn, Michigan 48128, USA
| | - Muslim Alkaabi
- Department of Natural Sciences, CASL, University of Michigan-Dearborn, Dearborn, Michigan 48128, USA
| | | | - Jie Fan
- Department of Natural Sciences, CASL, University of Michigan-Dearborn, Dearborn, Michigan 48128, USA
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5
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Peterson A, Bennin D, Lasarev M, Chini J, Beebe DJ, Huttenlocher A. Neutrophil motility is regulated by both cell intrinsic and endothelial cell ARPC1B. J Cell Sci 2024; 137:jcs261774. [PMID: 38224139 PMCID: PMC10911274 DOI: 10.1242/jcs.261774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Accepted: 01/08/2024] [Indexed: 01/16/2024] Open
Abstract
Neutrophil-directed motility is necessary for host defense, but its dysregulation can also cause collateral tissue damage. Actinopathies are monogenic disorders that affect the actin cytoskeleton and lead to immune dysregulation. Deficiency in ARPC1B, a component of the Arp2/3 complex, results in vascular neutrophilic inflammation; however, the mechanism remains unclear. Here, we generated human induced pluripotent stem cell (iPSC)-derived neutrophils (denoted iNeutrophils) that are deficient in ARPC1B and show impaired migration and a switch from forming pseudopodia to forming elongated filopodia. We show, using a blood vessel on a chip model, that primary human neutrophils have impaired movement across an endothelium deficient in APRC1B. We also show that the combined deficiency of ARPC1B in iNeutrophils and endothelium results in further reduction in neutrophil migration. Taken together, these results suggest that ARPC1B in endothelium is sufficient to drive neutrophil behavior. Furthermore, the findings provide support for using the iPSC system to understand human neutrophil biology and model disease in a genetically tractable system.
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Affiliation(s)
- Ashley Peterson
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA
- Comparative Biomedical Sciences Graduate Program, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - David Bennin
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Pediatrics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Michael Lasarev
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI 53706, USA
| | - Julia Chini
- Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - David J. Beebe
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA
- Carbone Cancer Center, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Anna Huttenlocher
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Pediatrics, University of Wisconsin-Madison, Madison, WI 53706, USA
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6
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Leeds BK, Kostello KF, Liu YY, Nelson CR, Biggins S, Asbury CL. Mechanical coupling coordinates microtubule growth. eLife 2023; 12:RP89467. [PMID: 38150374 PMCID: PMC10752587 DOI: 10.7554/elife.89467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2023] Open
Abstract
During mitosis, kinetochore-attached microtubules form bundles (k-fibers) in which many filaments grow and shorten in near-perfect unison to align and segregate each chromosome. However, individual microtubules grow at intrinsically variable rates, which must be tightly regulated for a k-fiber to behave as a single unit. This exquisite coordination might be achieved biochemically, via selective binding of polymerases and depolymerases, or mechanically, because k-fiber microtubules are coupled through a shared load that influences their growth. Here, we use a novel dual laser trap assay to show that microtubule pairs growing in vitro are coordinated by mechanical coupling. Kinetic analyses show that microtubule growth is interrupted by stochastic, force-dependent pauses and indicate persistent heterogeneity in growth speed during non-pauses. A simple model incorporating both force-dependent pausing and persistent growth speed heterogeneity explains the measured coordination of microtubule pairs without any free fit parameters. Our findings illustrate how microtubule growth may be synchronized during mitosis and provide a basis for modeling k-fiber bundles with three or more microtubules, as found in many eukaryotes.
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Affiliation(s)
- Bonnibelle K Leeds
- Department of Physiology & Biophysics, University of WashingtonSeattleUnited States
| | - Katelyn F Kostello
- Department of Physiology & Biophysics, University of WashingtonSeattleUnited States
| | - Yuna Y Liu
- Department of Physiology & Biophysics, University of WashingtonSeattleUnited States
| | - Christian R Nelson
- Basic Sciences Division, Fred Hutchinson Cancer Research CenterSeattleUnited States
| | - Sue Biggins
- Basic Sciences Division, Fred Hutchinson Cancer Research CenterSeattleUnited States
| | - Charles L Asbury
- Department of Physiology & Biophysics, University of WashingtonSeattleUnited States
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7
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McInally SG, Reading AJ, Rosario A, Jelenkovic PR, Goode BL, Kondev J. Length control emerges from cytoskeletal network geometry. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.28.569063. [PMID: 38076874 PMCID: PMC10705815 DOI: 10.1101/2023.11.28.569063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Many cytoskeletal networks consist of individual filaments that are organized into elaborate higher order structures. While it is appreciated that the size and architecture of these networks are critical for their biological functions, much of the work investigating control over their assembly has focused on mechanisms that regulate the turnover of individual filaments through size-dependent feedback. Here, we propose a very different, feedback-independent mechanism to explain how yeast cells control the length of their actin cables. Our findings, supported by quantitative cell imaging and mathematical modeling, indicate that actin cable length control is an emergent property that arises from the cross-linked and bundled organization of the filaments within the cable. Using this model, we further dissect the mechanisms that allow cables to grow longer in larger cells, and propose that cell length-dependent tuning of formin activity allows cells to scale cable length with cell length. This mechanism is a significant departure from prior models of cytoskeletal filament length control and presents a new paradigm to consider how cells control the size, shape, and dynamics of higher order cytoskeletal structures.
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Affiliation(s)
- Shane G. McInally
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, 01609, USA
| | | | - Aldric Rosario
- Department of Physics, Brandeis University, Waltham, MA, 02454, USA
| | | | - Bruce L. Goode
- Department of Biology, Brandeis University, Waltham, MA, 02454, USA
| | - Jane Kondev
- Department of Physics, Brandeis University, Waltham, MA, 02454, USA
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8
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Leeds BK, Kostello KF, Liu YY, Nelson CR, Biggins S, Asbury CL. Mechanical coupling coordinates microtubule growth. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.29.547092. [PMID: 37905093 PMCID: PMC10614740 DOI: 10.1101/2023.06.29.547092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
During mitosis, kinetochore-attached microtubules form bundles (k-fibers) in which many filaments grow and shorten in near-perfect unison to align and segregate each chromosome. However, individual microtubules grow at intrinsically variable rates, which must be tightly regulated for a k-fiber to behave as a single unit. This exquisite coordination might be achieved biochemically, via selective binding of polymerases and depolymerases, or mechanically, because k-fiber microtubules are coupled through a shared load that influences their growth. Here, we use a novel dual laser trap assay to show that microtubule pairs growing in vitro are coordinated by mechanical coupling. Kinetic analyses show that microtubule growth is interrupted by stochastic, force-dependent pauses and indicate persistent heterogeneity in growth speed during non-pauses. A simple model incorporating both force-dependent pausing and persistent growth speed heterogeneity explains the measured coordination of microtubule pairs without any free fit parameters. Our findings illustrate how microtubule growth may be synchronized during mitosis and provide a basis for modeling k-fiber bundles with three or more microtubules, as found in many eukaryotes.
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Affiliation(s)
- Bonnibelle K. Leeds
- Physiology & Biophysics Department, University of Washington School of Medicine, Seattle WA, USA
| | - Katelyn F. Kostello
- Physiology & Biophysics Department, University of Washington School of Medicine, Seattle WA, USA
| | - Yuna Y. Liu
- Physiology & Biophysics Department, University of Washington School of Medicine, Seattle WA, USA
| | | | | | - Charles L. Asbury
- Physiology & Biophysics Department, University of Washington School of Medicine, Seattle WA, USA
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9
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Fink A, Doll CR, Yagüe Relimpio A, Dreher Y, Spatz JP, Göpfrich K, Cavalcanti-Adam EA. Extracellular Cues Govern Shape and Cytoskeletal Organization in Giant Unilamellar Lipid Vesicles. ACS Synth Biol 2023; 12:369-374. [PMID: 36652603 PMCID: PMC9942188 DOI: 10.1021/acssynbio.2c00516] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Spontaneous and induced front-rear polarization and a subsequent asymmetric actin cytoskeleton is a crucial event leading to cell migration, a key process involved in a variety of physiological and pathological conditions such as tissue development, wound healing, and cancer. Migration of adherent cells relies on the balance between adhesion to the underlying matrix and cytoskeleton-driven front protrusion and rear retraction. A current challenge is to uncouple the effect of adhesion and shape from the contribution of the cytoskeleton in regulating the onset of front-rear polarization. Here, we present a minimal model system that introduces an asymmetric actin cytoskeleton in synthetic cells, which are resembled by giant unilamellar lipid vesicles (GUVs) adhering onto symmetric and asymmetric micropatterned surfaces. Surface micropatterning of streptavidin-coated regions with varying adhesion shape and area was achieved by maskless UV photopatterning. To further study the effects of GUV shape on the cytoskeletal organization, actin filaments were polymerized together with bundling proteins inside the GUVs. The micropatterns induce synthetic cell deformation upon adhesion to the surface, with the cell shape adapting to the pattern shape and size. As expected, asymmetric patterns induce an asymmetric deformation in adherent synthetic cells. Actin filaments orient along the long axis of the deformed GUV, when having a length similar to the size of the major axis, whereas short filaments exhibit random orientation. With this bottom-up approach we have laid the first steps to identify the relationship between cell front-rear polarization and cytoskeleton organization in the future. Such a minimal system will allow us to further study the major components needed to create a polarized cytoskeleton at the onset of migration.
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Affiliation(s)
- Andreas Fink
- Department
of Cellular Biophysics, Max Planck Institute
for Medical Research, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Charlotte R. Doll
- Department
of Cellular Biophysics, Max Planck Institute
for Medical Research, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Ana Yagüe Relimpio
- Department
of Cellular Biophysics, Max Planck Institute
for Medical Research, Jahnstraße 29, 69120 Heidelberg, Germany,Institute
for Molecular Systems Engineering, University
of Heidelberg, Im Neuenheimer
Feld 253, 69120 Heidelberg, Germany
| | - Yannik Dreher
- Biophysical
Engineering Group, Max Planck Institute
for Medical Research, Jahnstraße 29, 69120 Heidelberg, Germany,Department
of Physics and Astronomy, Heidelberg University, 69120 Heidelberg, Germany
| | - Joachim P. Spatz
- Department
of Cellular Biophysics, Max Planck Institute
for Medical Research, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Kerstin Göpfrich
- Biophysical
Engineering Group, Max Planck Institute
for Medical Research, Jahnstraße 29, 69120 Heidelberg, Germany,Department
of Physics and Astronomy, Heidelberg University, 69120 Heidelberg, Germany
| | - Elisabetta Ada Cavalcanti-Adam
- Department
of Cellular Biophysics, Max Planck Institute
for Medical Research, Jahnstraße 29, 69120 Heidelberg, Germany,E-mail:
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10
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Labuz EC, Footer MJ, Theriot JA. Confined keratocytes mimic in vivo migration and reveal volume-speed relationship. Cytoskeleton (Hoboken) 2023; 80:34-51. [PMID: 36576104 DOI: 10.1002/cm.21741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 12/07/2022] [Accepted: 12/26/2022] [Indexed: 12/29/2022]
Abstract
Fish basal epidermal cells, known as keratocytes, are well-suited for cell migration studies. In vitro, isolated keratocytes adopt a stereotyped shape with a large fan-shaped lamellipodium and a nearly spherical cell body. However, in their native in vivo environment, these cells adopt a significantly different shape during their rapid migration toward wounds. Within the epidermis, keratocytes experience two-dimensional (2D) confinement between the outer epidermal cell layer and the basement membrane; these two deformable surfaces constrain keratocyte cell bodies to be flatter in vivo than in isolation. In vivo keratocytes also exhibit a relative elongation of the front-to-back axis and substantially more lamellipodial ruffling, as compared to isolated cells. We have explored the effects of 2D confinement, separated from other in vivo environmental cues, by overlaying isolated cells with an agarose hydrogel with occasional spacers, or with a ceiling made of polydimethylsiloxane (PDMS) elastomer. Under these conditions, isolated keratocytes more closely resemble the in vivo migratory shape phenotype, displaying a flatter apical-basal axis and a longer front-to-back axis than unconfined keratocytes. We propose that 2D confinement contributes to multiple dimensions of in vivo keratocyte shape determination. Further analysis demonstrates that confinement causes a synchronous 20% decrease in both cell speed and volume. Interestingly, we were able to replicate the 20% decrease in speed using a sorbitol hypertonic shock to shrink the cell volume, which did not affect other aspects of cell shape. Collectively, our results suggest that environmentally imposed changes in cell volume may influence cell migration speed, potentially by perturbing physical properties of the cytoplasm.
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Affiliation(s)
- Ellen C Labuz
- Biophysics Program, Stanford University, Stanford, California, USA.,Department of Biology and Howard Hughes Medical Institute, University of Washington, Seattle, Washington, USA
| | - Matthew J Footer
- Department of Biology and Howard Hughes Medical Institute, University of Washington, Seattle, Washington, USA
| | - Julie A Theriot
- Department of Biology and Howard Hughes Medical Institute, University of Washington, Seattle, Washington, USA
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11
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A network of mixed actin polarity in the leading edge of spreading cells. Commun Biol 2022; 5:1338. [PMID: 36473943 PMCID: PMC9727120 DOI: 10.1038/s42003-022-04288-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 11/22/2022] [Indexed: 12/12/2022] Open
Abstract
Physical interactions of cells with the underlying extracellular matrix (ECM) play key roles in multiple cellular processes. The actin cytoskeleton is a central driver and regulator of cellular dynamics, that produces membrane-protrusions such as lamellipodia and filopodia. Here, we examined actin organization in expanding lamellipodia during early stages of cell spreading. To gain insight into the 3D actin organization, we plated fibroblasts on galectin-8 coated EM grids, an ECM protein presents in disease states. We then combined cryo-electron tomography with advanced image processing tools for reconstructing the structure of F-actin in the lamellipodia. This approach enabled us to resolve the polarity and orientation of filaments, and the structure of the Arp2/3 complexes associated with F-actin branches. We show that F-actin in lamellipodial protrusions forms a dense network with three distinct sub-domains. One consists primarily of radial filaments, with their barbed ends pointing towards the membrane, the other is enriched with parallel filaments that run between the radial fibers, in addition to an intermediate sub-domain. Surprisingly, a minor, yet significant (~10%) population of actin filaments, are oriented with their barbed-ends towards the cell center. Our results provide structural insights into F-actin assembly and dynamic reorganization in the leading edge of spreading cells.
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12
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Lappalainen P, Kotila T, Jégou A, Romet-Lemonne G. Biochemical and mechanical regulation of actin dynamics. Nat Rev Mol Cell Biol 2022; 23:836-852. [PMID: 35918536 DOI: 10.1038/s41580-022-00508-4] [Citation(s) in RCA: 77] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2022] [Indexed: 12/30/2022]
Abstract
Polymerization of actin filaments against membranes produces force for numerous cellular processes, such as migration, morphogenesis, endocytosis, phagocytosis and organelle dynamics. Consequently, aberrant actin cytoskeleton dynamics are linked to various diseases, including cancer, as well as immunological and neurological disorders. Understanding how actin filaments generate forces in cells, how force production is regulated by the interplay between actin-binding proteins and how the actin-regulatory machinery responds to mechanical load are at the heart of many cellular, developmental and pathological processes. During the past few years, our understanding of the mechanisms controlling actin filament assembly and disassembly has evolved substantially. It has also become evident that the activities of key actin-binding proteins are not regulated solely by biochemical signalling pathways, as mechanical regulation is critical for these proteins. Indeed, the architecture and dynamics of the actin cytoskeleton are directly tuned by mechanical load. Here we discuss the general mechanisms by which key actin regulators, often in synergy with each other, control actin filament assembly, disassembly, and monomer recycling. By using an updated view of actin dynamics as a framework, we discuss how the mechanics and geometry of actin networks control actin-binding proteins, and how this translates into force production in endocytosis and mesenchymal cell migration.
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Affiliation(s)
- Pekka Lappalainen
- Institute of Biotechnology and Helsinki Institute of Life Sciences, University of Helsinki, Helsinki, Finland.
| | - Tommi Kotila
- Institute of Biotechnology and Helsinki Institute of Life Sciences, University of Helsinki, Helsinki, Finland
| | - Antoine Jégou
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
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13
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Alderfer S, Sun J, Tahtamouni L, Prasad A. Morphological signatures of actin organization in single cells accurately classify genetic perturbations using CNNs with transfer learning. SOFT MATTER 2022; 18:8342-8354. [PMID: 36222484 DOI: 10.1039/d2sm01000c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The actin cytoskeleton plays essential roles in countless cell processes, from cell division to migration to signaling. In cancer cells, cytoskeletal dynamics, cytoskeletal filament organization, and overall cell morphology are known to be altered substantially. We hypothesize that actin fiber organization and cell shape may carry specific signatures of genetic or signaling perturbations. We used convolutional neural networks (CNNs) on a small fluorescence microscopy image dataset of retinal pigment epithelial (RPE) cells and triple-negative breast cancer (TNBC) cells for identifying morphological signatures in cancer cells. Using a transfer learning approach, CNNs could be trained to accurately distinguish between normal and oncogenically transformed RPE cells with an accuracy of about 95% or better at the single cell level. Furthermore, CNNs could distinguish transformed cell lines differing by an oncogenic mutation from each other and could also detect knockdown of cofilin in TNBC cells, indicating that each single oncogenic mutation or cytoskeletal perturbation produces a unique signature in actin morphology. Application of the Local Interpretable Model-Agnostic Explanations (LIME) method for visually interpreting the CNN results revealed features of the global actin structure relevant for some cells and classification tasks. Interestingly, many of these features were supported by previous biological observation. Actin fiber organization is thus a sensitive marker for cell identity, and identification of its perturbations could be very useful for assaying cell phenotypes, including disease states.
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Affiliation(s)
- Sydney Alderfer
- Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO 80523, USA.
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA
| | - Jiangyu Sun
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Lubna Tahtamouni
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
- Department of Biology and Biotechnology, The Hashemite University, Zarqa, Jordan
| | - Ashok Prasad
- Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO 80523, USA.
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA
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