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Mishra M, Kapoor S. Modulation of a host's cell membrane nano-environment by mycobacterial glycolipids: involvement of PI(4,5)P 2 signaling lipid? Faraday Discuss 2021; 232:295-316. [PMID: 34542111 DOI: 10.1039/d0fd00051e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Virulence-associated glycolipids from Mycobacterium tuberculosis (Mtb) act as effector molecules during infection-in addition to proteins. Upon insertion, they alter the host cell's membrane properties modifying the host's functions to aid Mtb survival and disease course. Here we combine tether force experiments and microscopy to reveal previously unknown insights on the potential involvement of the phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) lipid in the Mtb lipid-host interaction landscape. Our data shows that Mtb lipids, having different structural and chemical make-up, distinctly alter a host's PI(4,5)P2 membrane abundance/organization and PI(4,5)P2-actin colocalization, thus impacting the plasma membrane-cytoskeletal adhesion forces. Combined with our previous findings that underscore the role of exogenous Mtb lipids in remodeling host plasma membrane organization and mechanics, this work builds upon a lipid-centric view of tubercular infections. Dynamically changing a host's plasma membrane lipid content - in response to virulent lipids - might represent a so far unexplored mechanism invoked by Mtb to modulate the host cell's adhesive properties to escape immune surveillance. These findings will deepen our collective understanding of the functional role of Mtb lipids in hijacking the host cell processes amenable to pharmacological inhibition.
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Affiliation(s)
- Manjari Mishra
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India.
| | - Shobhna Kapoor
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India.
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2
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Wakida NM, Cruz GMS, Pouladian P, Berns MW, Preece D. Fluid Shear Stress Enhances the Phagocytic Response of Astrocytes. Front Bioeng Biotechnol 2020; 8:596577. [PMID: 33262978 PMCID: PMC7686466 DOI: 10.3389/fbioe.2020.596577] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 10/15/2020] [Indexed: 12/22/2022] Open
Abstract
Astrocytes respond to brain injury at a cellular level by the process of reactive astrogliosis, and are able to adjust their response according to the severity of the insult. Included in the reactive response is the process of phagocytosis, where astrocytes clean up surrounding cellular debris from damaged cells. In this study, we observe the process of phagocytosis by primary cortical astrocytes in the presence of media flow across the apical surface of the cells. Both static and cells under flow conditions respond consistently via phagocytosis of laser-induced cellular debris. We found that astrocytes exposed to shear flow initiate phagocytosis at a consistently faster rate than cells observed under static conditions. Shear forces created by laminar flow were analyzed as well as the flow fields created around astrocyte cells. Results suggest astrocyte phagocytosis is a mechanosensitive response, thus revealing the potential to enhance astrocyte phagocytic cleanup of damaged nervous tissue.
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Affiliation(s)
- Nicole M Wakida
- Berns Laboratory, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA, United States
| | - Gladys Mae Saquilabon Cruz
- Berns Laboratory, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA, United States
| | - Pegah Pouladian
- Berns Laboratory, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA, United States.,Preece Laboratory, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA, United States
| | - Michael W Berns
- Berns Laboratory, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA, United States
| | - Daryl Preece
- Preece Laboratory, Beckman Laser Institute and Medical Clinic, University of California, Irvine, Irvine, CA, United States
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3
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The intracellular calcium dynamics in a single vascular endothelial cell being squeezed through a narrow microfluidic channel. Biomech Model Mechanobiol 2020; 20:55-67. [PMID: 32710185 DOI: 10.1007/s10237-020-01368-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 07/11/2020] [Indexed: 12/17/2022]
Abstract
Revealing the mechanisms underlying the intracellular calcium responses in vascular endothelial cells (VECs) induced by mechanical stimuli contributes to a better understanding for vascular diseases, including hypertension, atherosclerosis, and aneurysm. Combining with experimental measurement and Computational Fluid Dynamics simulation, we developed a mechanobiological model to investigate the intracellular [Ca2+] response in a single VEC being squeezed through narrow microfluidic channel. The time-dependent cellular surface tension dynamics was quantified throughout the squeezing process. In our model, the various Ca2+ signaling pathways activated by mechanical stimulation is fully considered. The simulation results of our model exhibited well agreement with our experimental results. By using the model, we theoretically explored the mechanism of the two-peak intracellular [Ca2+] response in single VEC being squeezed through narrow channel and made some testable predictions for guiding experiment in the future.
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4
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Modeling the Mechanosensitivity of Neutrophils Passing through a Narrow Channel. Biophys J 2016; 109:2235-45. [PMID: 26636935 DOI: 10.1016/j.bpj.2015.10.032] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 09/20/2015] [Accepted: 10/13/2015] [Indexed: 11/21/2022] Open
Abstract
Recent experiments have found that neutrophils may be activated after passing through microfluidic channels and filters. Mechanical deformation causes disassembly of the cytoskeleton and a sudden drop of the elastic modulus of the neutrophil. This fluidization is followed by either activation of the neutrophil with protrusion of pseudopods or a uniform recovery of the cytoskeleton network with no pseudopod. The former occurs if the neutrophil traverses the narrow channel at a slower rate. We propose a chemo-mechanical model for the fluidization and activation processes. Fluidization is treated as mechanical destruction of the cytoskeleton by sufficiently rapid bending. Loss of the cytoskeleton removes a pathway by which cortical tension inhibits the Rac protein. As a result, Rac rises and polarizes through a wave-pinning mechanism if the chemical reaction rate is fast enough. This leads to recovery and reinforcement of the cytoskeleton at the front of the neutrophil, and hence protrusion and activation. Otherwise the Rac signal returns to a uniform pre-deformation state and no activation occurs. Thus, mechanically induced neutrophil activation is understood as the competition between two timescales: that of chemical reaction and that of mechanical deformation. The model captures the main features of the experimental observation.
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5
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Farrell B, Qian F, Kolomeisky A, Anvari B, Brownell WE. Measuring forces at the leading edge: a force assay for cell motility. Integr Biol (Camb) 2013; 5:204-14. [PMID: 23080534 DOI: 10.1039/c2ib20097j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cancer cells become mobile by remodelling their cytoskeleton to form migratory structures. This transformation is dominated by actin assembly and disassembly (polymerisation and depolymerisation) in the cytoplasm. Synthesis of filamentous actin produces a force at the leading edge that pushes the plasma membrane forward. We describe an assay to measure the restoring force of the membrane in response to forces generated within the cytoplasm adjacent to the membrane. A laser trap is used to form a long membrane nanotube from a living cell and to measure the axial membrane force at the end of the tube. When the tube, resembling a filopodium, is formed and in a relaxed state the axial membrane force exhibits a positive stationary value. This value reflects the influence of the cytoskeleton that acts to pull the tube back to the cell. A dynamic sawtooth force that rides upon the stationary value is also observed. This force is sensitive to a toxin that affects actin assembly and disassembly, but not affected by agents that influence microtubules and myosin light chain kinase. We deduce from the magnitude and characteristics of dynamic force measurements that it originates from depolymerisation and polymerisation of F-actin. The on- and off-rates, the number of working filaments, and the force per filament (2.5 pN) are determined. We suggest the force-dependent transitions are thermodynamically uncoupled as both the on- and off-rates decrease exponentially with a compressive load. We propose kinetic schemes that require attachment of actin filaments to the membrane during depolymerisation. This demonstrates that actin kinetics can be monitored in a living cell by measuring force at the membrane, and used to probe the mobility of cells including cancer cells.
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Affiliation(s)
- Brenda Farrell
- Bobby R Alford Department of Otolaryngology - Head & Neck Surgery, Baylor College of Medicine, Houston, TX 77030, USA.
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6
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Increasing membrane tension decreases miscibility temperatures; an experimental demonstration via micropipette aspiration. Biophys J 2012; 103:L35-7. [PMID: 23083725 DOI: 10.1016/j.bpj.2012.08.061] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 07/31/2012] [Accepted: 08/28/2012] [Indexed: 11/23/2022] Open
Abstract
It has been hypothesized that cytoskeletal tension prevents large-scale phase separation within cell plasma membranes. Here, we microaspirate giant unilamellar vesicles to determine the effect of mechanical stress on the liquid/liquid miscibility temperature of a membrane composed of a ternary lipid mixture. An increase in tension of 0.1 mN/m induces a decrease in miscibility temperature on the order of a few tenths of a degree K, which validates recent theoretical predictions.
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7
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Brownell WE, Qian F, Anvari B. Cell membrane tethers generate mechanical force in response to electrical stimulation. Biophys J 2010; 99:845-52. [PMID: 20682262 PMCID: PMC3297770 DOI: 10.1016/j.bpj.2010.05.025] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 03/25/2010] [Accepted: 05/10/2010] [Indexed: 11/22/2022] Open
Abstract
Living cells maintain a huge transmembrane electric field across their membranes. This electric field exerts a force on the membrane because the membrane surfaces are highly charged. We have measured electromechanical force generation by cell membranes using optically trapped beads to detach the plasma membrane from the cytoskeleton and form long thin cylinders (tethers). Hyperpolarizing potentials increased and depolarizing potentials decreased the force required to pull a tether. The membrane tether force in response to sinusoidal voltage signals was a function of holding potential, tether diameter, and tether length. Membrane electromechanical force production can occur at speeds exceeding those of ATP-based protein motors. By harnessing the energy in the transmembrane electric field, cell membranes may contribute to processes as diverse as outer hair cell electromotility, ion channel gating, and transport.
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Affiliation(s)
- William E Brownell
- Bobby R. Alford Department of Otolaryngology, Head & Neck Surgery, and Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA.
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Cuerrier CM, Gagner A, Lebel R, Gobeil F, Grandbois M. Effect of thrombin and bradykinin on endothelial cell mechanical properties monitored through membrane deformation. J Mol Recognit 2009; 22:389-96. [DOI: 10.1002/jmr.953] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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9
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Khismatullin DB. Chapter 3 The Cytoskeleton and Deformability of White Blood Cells. CURRENT TOPICS IN MEMBRANES 2009. [DOI: 10.1016/s1063-5823(09)64003-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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10
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Sun M, Northup N, Marga F, Huber T, Byfield FJ, Levitan I, Forgacs G. The effect of cellular cholesterol on membrane-cytoskeleton adhesion. J Cell Sci 2007; 120:2223-31. [PMID: 17550968 DOI: 10.1242/jcs.001370] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Whereas recent studies suggest that cholesterol plays important role in the regulation of membrane proteins, its effect on the interaction of the cell membrane with the underlying cytoskeleton is not well understood. Here, we investigated this by measuring the forces needed to extract nanotubes (tethers) from the plasma membrane, using atomic force microscopy. The magnitude of these forces provided a direct measure of cell stiffness, cell membrane effective surface viscosity and association with the underlying cytoskeleton. Furthermore, we measured the lateral diffusion constant of a lipid analog DiIC12, using fluorescence recovery after photobleaching, which offers additional information on the organization of the membrane. We found that cholesterol depletion significantly increased the adhesion energy between the membrane and the cytoskeleton and decreased the membrane diffusion constant. An increase in cellular cholesterol to a level higher than that in control cells led to a decrease in the adhesion energy and the membrane surface viscosity. Disassembly of the actin network abrogated all the observed effects, suggesting that cholesterol affects the mechanical properties of a cell through the underlying cytoskeleton. The results of these quantitative studies may help to better understand the biomechanical processes accompanying the development of atherosclerosis.
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Affiliation(s)
- Mingzhai Sun
- Department of Physics and Astronomy, University of Missouri-Columbia, Columbia, MO 65211, USA
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11
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Hosu BG, Sun M, Marga F, Grandbois M, Forgacs G. Eukaryotic membrane tethers revisited using magnetic tweezers. Phys Biol 2007; 4:67-78. [PMID: 17664652 DOI: 10.1088/1478-3975/4/2/001] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Membrane nanotubes, under physiological conditions, typically form en masse. We employed magnetic tweezers (MTW) to extract tethers from human brain tumor cells and compared their biophysical properties with tethers extracted after disruption of the cytoskeleton and from a strongly differing cell type, Chinese hamster ovary cells. In this method, the constant force produced with the MTW is transduced to cells through super-paramagnetic beads attached to the cell membrane. Multiple sudden jumps in bead velocity were manifest in the recorded bead displacement-time profiles. These discrete events were interpreted as successive ruptures of individual tethers. Observation with scanning electron microscopy supported the simultaneous existence of multiple tethers. The physical characteristics, in particular, the number and viscoelastic properties of the extracted tethers were determined from the analytic fit to bead trajectories, provided by a standard model of viscoelasticity. Comparison of tethers formed with MTW and atomic force microscopy (AFM), a technique where the cantilever-force transducer is moved at constant velocity, revealed significant differences in the two methods of tether formation. Our findings imply that extreme care must be used to interpret the outcome of tether pulling experiments performed with single molecular techniques (MTW, AFM, optical tweezers, etc). First, the different methods may be testing distinct membrane structures with distinct properties. Second, as soon as a true cell membrane (as opposed to that of a vesicle) can attach to a substrate, upon pulling on it, multiple nonspecific membrane tethers may be generated. Therefore, under physiological conditions, distinguishing between tethers formed through specific and nonspecific interactions is highly nontrivial if at all possible.
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Affiliation(s)
- Basarab G Hosu
- Department of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
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12
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Cantiello HF, Montalbetti N, Li Q, Chen XZ. The Cytoskeletal Connection to Ion Channels as a Potential Mechanosensory Mechanism: Lessons from Polycystin-2 (TRPP2). CURRENT TOPICS IN MEMBRANES 2007; 59:233-96. [PMID: 25168140 DOI: 10.1016/s1063-5823(06)59010-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Mechanosensitivity of ion channels, or the ability to transfer mechanical forces into a gating mechanism of channel regulation, is split into two main working (not mutually exclusive) hypotheses. One is that elastic and/or structural changes in membrane properties act as a transducing mechanism of channel regulation. The other hypothesis involves tertiary elements, such as the cytoskeleton which, itself by dynamic interactions with the ion channel, may convey conformational changes, including those ascribed to mechanical forces. This hypothesis is supported by numerous instances of regulatory changes in channel behavior by alterations in cytoskeletal structures/interactions. However, only recently, the molecular nature of these interactions has slowly emerged. Recently, a surge of evidence has emerged to indicate that transient receptor potential (TRP) channels are key elements in the transduction of a variety of environmental signals. This chapter describes the molecular linkage and regulatory elements of polycystin-2 (PC2), a TRP-type (TRPP2) nonselective cation channel whose mutations cause autosomal dominant polycystic kidney disease (ADPKD). The chapter focuses on the involvement of cytoskeletal structures in the regulation of PC2 and discusses how these connections are the transducing mechanism of environmental signals to its channel function.
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Affiliation(s)
- Horacio F Cantiello
- Renal Unit, Massachusetts General Hospital East, Charlestown, Massachusetts 02129; Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115; Laboratorio de Canales Iónicos, Departamento de Fisicoquímica y Química Analítica, Facultad de Farmacia y Bioquímica, Buenos Aires 1113, Argentina
| | - Nicolás Montalbetti
- Laboratorio de Canales Iónicos, Departamento de Fisicoquímica y Química Analítica, Facultad de Farmacia y Bioquímica, Buenos Aires 1113, Argentina
| | - Qiang Li
- Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada
| | - Xing-Zhen Chen
- Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada
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Suzuki T, Yanai M, Kubo H, Kanda A, Sasaki H, Butler JP. Interaction of non-adherent suspended neutrophils to complement opsonized pathogens: a new assay using optical traps. Cell Res 2006; 16:887-94. [PMID: 17063142 DOI: 10.1038/sj.cr.7310103] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Phagocytosis of opsonized pathogens by circulating non-adherent neutrophils is an essential step in host defense, which when overwhelmed contributes to sepsis. To investigate the role played by ligation of complement receptors CR3 and CR4 in non-adherent neutrophils, we designed a novel assay system utilizing dual optical traps, respectively, holding a suspended unactivated cell and presenting a specific ligand-coated bead to the cell surface. We chose anti-CD18 as an example ligand, mimicking the bacterial opsonizing complement fragment iC3b. Presentation of anti-CD18-coated beads elicited both pseudopodial protrusion and subsequent phagocytosis. This is in sharp contrast to previously reported responses of adherent neutrophils, which phagocytize opsonized particles without pseudopod formation. We used this same new assay to probe actomyosin pathways in the neutrophil's pseudopodial and phagocytic response. Disruption of actin or inhibition of myosin light-chain kinase dose-dependently reduced pseudopod formation and phagocytosis rates. In summary, i) the new dual trap assay can be used to study the responses of suspended neutrophils to a variety of ligands, and ii) in a first application of this technique, we found that local ligation of CR3/4 in unactivated neutrophils in suspension induces pseudopod formation and phagocytosis at that site, and that these events occur via an actomyosin-dependent pathway.
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Affiliation(s)
- Tomoko Suzuki
- Department of Geriatric and Respiratory Medicine, Tohoku University School of Medicine, Sendai 980-8574, Japan
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Vonna L, Wiedemann A, Aepfelbacher M, Sackmann E. Micromechanics of filopodia mediated capture of pathogens by macrophages. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2006; 36:145-51. [PMID: 17160406 DOI: 10.1007/s00249-006-0118-y] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Revised: 11/15/2006] [Accepted: 11/17/2006] [Indexed: 11/24/2022]
Abstract
The biological function of filopodia has been extensively studied while only little work has been done on their mechanical properties. In the present study, we apply magnetic microbeads to explore the capturing and initial step of phagocytosis of pathogens by macrophages through filopodia. Microbeads were covered by the bacterial coat protein invasin which is known to trigger the invasion of the intestine by the bacteria Yersinia enterocolitica. These mimetics of bacteria were placed in the vicinity of J774 mouse macrophages exhibiting long filopodia. The specific adhesion of beads to the tip of a filopodium induced the retraction of the protrusion resulting in the dragging of the bead towards the cell body. The dynamics of the retraction process was analyzed by following the in-plane motion of the bead. We estimated the minimal force developed by filopodia and compared the results with previous magnetic tweezer studies of mechanical force induced growth of protrusions (Vonna et al. 2003). We show that very thin filopodia can generate astonishingly large retraction forces over large distances (>10 microm) and can act as an efficient mechanical tool to detach pathogens adhering on surfaces.
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Affiliation(s)
- L Vonna
- Institut de Chimie des Surfaces et Interfaces, 15, rue Jean Starcky, BP2478, 68057 Mulhouse Cedex, France.
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15
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Heinrich D, Sackmann E. Active mechanical stabilization of the viscoplastic intracellular space of Dictyostelia cells by microtubule-actin crosstalk. Acta Biomater 2006; 2:619-31. [PMID: 16942924 DOI: 10.1016/j.actbio.2006.05.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2006] [Revised: 05/19/2006] [Accepted: 05/23/2006] [Indexed: 10/24/2022]
Abstract
The micro-viscoelasticity of the intracellular space of Dictyostelium discoideum cells is studied by evaluating the intracellular transport of magnetic force probes and their viscoelastic responses to force pulses of 20-700 pN. The role of the actin cortex, the microtubule (MT) aster and their crosstalk is explored by comparing the behaviour of wild-type cells, myosin II null mutants, latrunculin A and benomyl treated cells. The MT coupled beads perform irregular local and long range directed motions which are characterized by measuring their velocity distributions (P(v)). The correlated motion of the MT and the centrosome are evaluated by microfluorescence of GFP-labelled MTs. P(v) can be represented by log-normal distributions with long tails and it is determined by random sweeping motions (v approximately 0.5 microm/s) of the MTs (caused by tangential forces on the filament ends coupled to the actin cortex) and by intermittent bead transports parallel to the MTs (v(max) approximately 1.5 microm/s). The tails are due to spontaneous filament deflections (with speeds up to 10 microm/s) attributed to pre-stressing of the MT by local cortical tensions, generated by dynactin motors generating plus-end directed forces in the MTs. The viscoelastic responses are strongly non-linear and are mostly directed opposite or perpendicular to the force, showing that the cytoplasm behaves as an active viscoplastic body with time and force dependent drag coefficients. Nano-Newton loads exerted on the soft MT are balanced by traction forces arising at the MT ends coupled to the actin cortex and the centrosome, respectively. The mechanical coupling between the soft microtubules and the viscoelastic actin cortex provides cells with high mechanical stability despite the softness of the cytoplasm.
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Affiliation(s)
- Doris Heinrich
- Physik Department, Lehrstuhl fuer Biophysik E22, Technische Universitaet Muenchen, D-85748 Garching, Germany
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16
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Karamichos D, Brown RA, Mudera V. Complex dependence of substrate stiffness and serum concentration on cell-force generation. J Biomed Mater Res A 2006; 78:407-15. [PMID: 16715519 DOI: 10.1002/jbm.a.30814] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Collagen is a widely used biomaterial in tissue engineering. Mechanical stimulation of cell-seeded collagen constructs and its effects on cell orientation, intracellular signaling, and molecular responses have been reported. Our aim was to study the transfer of applied mechanical load to resident cells in 3D collagen constructs. Stainless steel markers were embedded in constructs as reporters of micromovement and uniaxial (0-15%) strain was applied. Cell-seeded collagen constructs were also subjected to (0-15%) uniaxial strain and material responses recorded. The viscoelastic properties of collagen resulted in comparatively small movement of the marker bars relative to gel deformation. Cell seeding density of 1 million/mL had no significant effect on the viscoelastic properties of collagen for the range of strain tested. Our findings indicate that viscoelastic properties of collagen result in minimal force transfer of applied loads as recorded by movement of stainless steel markers. At higher strain rates as collagen got stiffer the movement decreased. These findings indicate that as cell-seeded collagen constructs mature in a bioreactor and become stiffer due to ECM production/deposition, mechanical stimulation will have to be tailored over time to account for increased stiffness of constructs in vitro to elicit predictable and consistent cellular responses.
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Affiliation(s)
- D Karamichos
- UCL, Tissue Repair and Engineering Centre, Institute of Orthopaedics and Musculoskeletal Sciences, Stanmore, London, HA7 4LP, United Kingdom
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17
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Gardel ML, Nakamura F, Hartwig JH, Crocker JC, Stossel TP, Weitz DA. Prestressed F-actin networks cross-linked by hinged filamins replicate mechanical properties of cells. Proc Natl Acad Sci U S A 2006; 103:1762-7. [PMID: 16446458 PMCID: PMC1413620 DOI: 10.1073/pnas.0504777103] [Citation(s) in RCA: 271] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We show that actin filaments, shortened to physiological lengths by gelsolin and cross-linked with recombinant human filamins (FLNs), exhibit dynamic elastic properties similar to those reported for live cells. To achieve elasticity values of comparable magnitude to those of cells, the in vitro network must be subjected to external prestress, which directly controls network elasticity. A molecular requirement for the strain-related behavior at physiological conditions is a flexible hinge found in FLNa and some FLNb molecules. Basic physical properties of the in vitro filamin-F-actin network replicate the essential mechanical properties of living cells. This physical behavior could accommodate passive deformation and internal organelle trafficking at low strains yet resist externally or internally generated high shear forces.
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Affiliation(s)
- M. L. Gardel
- Department of Physics and Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
| | - F. Nakamura
- Hematology Division, Brigham and Women’s Hospital, Department of Medicine, Harvard Medical School, Boston, MA 02115; and
| | - J. H. Hartwig
- Hematology Division, Brigham and Women’s Hospital, Department of Medicine, Harvard Medical School, Boston, MA 02115; and
| | - J. C. Crocker
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104
| | - T. P. Stossel
- Hematology Division, Brigham and Women’s Hospital, Department of Medicine, Harvard Medical School, Boston, MA 02115; and
| | - D. A. Weitz
- Department of Physics and Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
- To whom correspondence should be addressed at:
Department of Physics and Division of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138. E-mail:
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Sun M, Graham JS, Hegedüs B, Marga F, Zhang Y, Forgacs G, Grandbois M. Multiple membrane tethers probed by atomic force microscopy. Biophys J 2005; 89:4320-9. [PMID: 16183875 PMCID: PMC1366996 DOI: 10.1529/biophysj.104.058180] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Using the atomic force microscope to locally probe the cell membrane, we observed the formation of multiple tethers (thin nanotubes, each requiring a similar pulling force) as reproducible features within force profiles recorded on individual cells. Forces obtained with Chinese hamster ovary cells, a malignant human brain tumor cell line, and human endothelial cells (EA hy926) were found to be 28 +/- 10 pN, 29 +/- 9 pN, and 29 +/- 10 pN, respectively, independent of the nature of attachment to the cantilever. The rather large variation of the tether pulling forces measured at several locations on individual cells points to the existence of heterogeneity in the membrane properties of a morphologically homogeneous cell. Measurement of the summary lengths of the simultaneously extracted tethers provides a measure of the size of the available membrane reservoir through which co-existing tethers are associated. As expected, partial disruption of the actin cytoskeleton and removal of the hyaluronan backbone of the glycocalyx were observed to result in a marked decrease (30-50%) in the magnitude and a significant sharpening of the force distribution indicating reduced heterogeneity of membrane properties. Taken together, our results demonstrate the ability of the plasma membrane to locally produce multiple interdependent tethers-a process that could play an important role in the mechanical association of cells with their environment.
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Affiliation(s)
- Mingzhai Sun
- Department of Physics, University of Missouri, Columbia, Missouri, USA
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Kalapesi FB, Tan JCH, Coroneo MT. Stretch-activated channels: a mini-review. Are stretch-activated channels an ocular barometer? Clin Exp Ophthalmol 2005; 33:210-7. [PMID: 15807835 DOI: 10.1111/j.1442-9071.2005.00981.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
All cells are subject to physical forces by virtue of their position in a dynamically changing environment. This review outlines the various putative 'mechanosensors', or sensors of pressure cells possess, and discusses in particular the role stretch-activated membrane channels play in pressure recognition and transduction. The widespread occurrence of these channels is discussed and these 'mechanosensors' are related to pressure-related diseases, in particular, glaucoma.
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Affiliation(s)
- Freny B Kalapesi
- Department of Ophthalmology, Prince of Wales Hospital, University of New South Wales, Sydney, New South Wales, Australia
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20
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Kong HJ, Polte TR, Alsberg E, Mooney DJ. FRET measurements of cell-traction forces and nano-scale clustering of adhesion ligands varied by substrate stiffness. Proc Natl Acad Sci U S A 2005; 102:4300-5. [PMID: 15767572 PMCID: PMC555469 DOI: 10.1073/pnas.0405873102] [Citation(s) in RCA: 207] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The mechanical properties of cell adhesion substrates regulate cell phenotype, but the mechanism of this relation is currently unclear. It may involve the magnitude of traction force applied by the cell, and/or the ability of the cells to rearrange the cell adhesion molecules presented from the material. In this study, we describe a FRET technique that can be used to evaluate the mechanics of cell-material interactions at the molecular level and simultaneously quantify the cell-based nanoscale rearrangement of the material itself. We found that these events depended on the mechanical rigidity of the adhesion substrate. Furthermore, both the proliferation and differentiation of preosteoblasts (MC3T3-E1) correlated to the magnitude of force that cells generate to cluster the cell adhesion ligands, but not the extent of ligand clustering. Together, these data demonstrate the utility of FRET in analyzing cell-material interactions, and suggest that regulation of phenotype with substrate stiffness is related to alterations in cellular traction forces.
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Affiliation(s)
- Hyun Joon Kong
- Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
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21
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Feneberg W, Aepfelbacher M, Sackmann E. Microviscoelasticity of the apical cell surface of human umbilical vein endothelial cells (HUVEC) within confluent monolayers. Biophys J 2005; 87:1338-50. [PMID: 15298936 PMCID: PMC1304472 DOI: 10.1529/biophysj.103.037044] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We studied the local viscoelasticity of the apical membrane of human umbilical vein endothelial cells within confluent layers by magnetic tweezers microrheometry. Magnetic beads are coupled to various integrins by coating with fibronectin or invasin. By analyzing the deflection of beads evoked by various force scenarios we demonstrate that the cell envelope behaves as a linear viscoelastic body if forces up to 2 nN are applied for short times (<20 s) but can respond in an adaptive way if stress pulses are applied longer (>30 s). The time-dependent shear relaxation modulus G(t) exhibits three time regimes: a fast response (t < 0.05 s) where the relaxation modulus G(t) obeys a power law G(t) approximately t(-0.82+/-0.02); a plateau-like behavior (at 0.05 s < t < 0.15 s); and a slow flow-like response which is, however, partially reversible. Strain field mapping experiments with colloidal probes show that local forces induce a strain field exhibiting a range of zeta = 10 +/- 1 microm, but which could only be observed if nonmagnetic beads were coupled to the cell surface by invasin. By application of the theory of elasticity of planar bodies we estimated a surface shear modulus of 2.5 x10(-4) N/m. By assuming a thickness of the actin cortex of approximately 0.5 microm we estimate a Young modulus micro approximately 400 Pa for the apical membrane. The value agrees with a plateau modulus of an entangled or weakly cross-linked actin network of an actin concentration of 100 microM (mesh size 0.2 microm). This result together with our observation of a strong reduction of the shear modulus by the actin destabilizing agent latrunculin A suggests that the shear modulus measured by our technique is determined by the actin cortex. The effect of two ligands inducing actin stress fiber formation and centripetal contraction of cells (associated with the formation of gaps in the confluent cell monolayer) on the viscoelastic responses were studied: histamine and lysophosphatidic acid (LPA). Histamine evoked a dramatic increase of the cell stiffness by >1 order of magnitude within <30 s, which is attributed to a transient rise of the intracellular Ca(2+) level, since DMSO exerted a similar effect. The stiffening is accompanied by a concomitant rounding of the cells as observed by microinterferometry and relaxes partially in the timescale of 5 min, whereas gaps between cells close after approximately 30 min. LPA did not exert a remarkable and reproducible effect other than an occasional very weak transient increase of the shear stiffness, which shows that the gap formation activated by LPA is mediated by a different mechanism than that induced by histamine.
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Affiliation(s)
- Wolfgang Feneberg
- Technische Universität München, Lehrstuhl für Biophysik E22, Garching, Germany
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22
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Chodniewicz D, Alteraifi AM, Zhelev DV. Experimental Evidence for the Limiting Role of Enzymatic Reactions in Chemoattractant-induced Pseudopod Extension in Human Neutrophils. J Biol Chem 2004; 279:24460-6. [PMID: 15051729 DOI: 10.1074/jbc.m312764200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chemoattractant-stimulated pseudopod growth in human neutrophils was used as a model system to study the rate-limiting mechanism of cytoskeleton rearrangement induced by activated G-protein-coupled receptors. Cells were activated with N-formyl-Met-Leu-Phe, and the temperature dependence of the rate of pseudopod extension was measured in the presence of pharmacological inhibitors with known mechanisms of action. Three groups of inhibitors were used: (i) inhibitors sequestering substrates involved in F-actin polymerization (latrunculin A for G-actin and cytochalasin D for actin filament-free barbed ends) or sequestering secondary messengers (PIP-binding peptide for phosphoinositide lipids); (ii) competitively binding inhibitors (Akt-inhibitor for Akt/protein kinase B); and (iii) inhibitors that reduce enzyme activity (wortmannin for phosphoinositide 3-kinase and chelerythrine for protein kinase C). The experimental data are consistent with a model in which the relative involvement of a given pathway of F-actin polymerization to the measured rate of pseudopod extension is limited by a slowest (bottleneck) reaction in the cascade of reactions involved in the overall signaling pathway. The approach we developed was used to demonstrate that chemoattractant-induced pseudopod growth and mechanically stimulated cytoskeleton rearrangement are controlled by distinct pathways of F-actin polymerization.
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Affiliation(s)
- David Chodniewicz
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708-0300, USA
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23
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Smith AS, Sackmann E, Seifert U. Pulling tethers from adhered vesicles. PHYSICAL REVIEW LETTERS 2004; 92:208101. [PMID: 15169384 DOI: 10.1103/physrevlett.92.208101] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2003] [Indexed: 05/24/2023]
Abstract
The competition between adhesion and tether formation in bound vesicles is investigated. A theoretical model is developed in which tethers are induced by the application of a pulling force to the top of a strongly adhered vesicle. A critical onset force is identified where the tether spontaneously appears as part of a first order shape transition. Further growth of the tether initiates a detachment process that culminates in a continuous unbinding of the vesicle at a finite detachment force. Both critical forces, as well as all shape parameters, are calculated as a function of the reduced volume and the strength of adhesive potential.
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Affiliation(s)
- Ana-Suncana Smith
- E 22 Institut für Biophysik, Technische Universität München, D-85748 Garching, Germany
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24
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Vonna L, Wiedemann A, Aepfelbacher M, Sackmann E. Local force induced conical protrusions of phagocytic cells. J Cell Sci 2003; 116:785-90. [PMID: 12571276 DOI: 10.1242/jcs.00230] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Magnetic tweezers were used to study the passive and active response of macrophages to local centripetal nanonewton forces on beta1 integrins. Superparamagnetic beads coated with the beta1-integrin-binding protein invasin were attached to J774 murine macrophages to mimic phagocytosis of bacterial pathogens. Forces exceeding approximately 0.5 nN induce the active formation of trumpet-like protrusions resembling pseudopodia after an initial elastic deflection and a response time of approximately 30 seconds. The speed of advancement of the protrusion is <v>=0.065+/-0.020 micro m second(-1) and is force independent. After saturation (after about 100 seconds) the protrusion stops abruptly and is completely retracted again against forces exceeding 5 nN with an effective relaxation time of approximately 30 seconds. The active protrusion is tentatively attributed to the growth of the actin cortex in the direction of the force, and evidence for the involvement of actin is provided by the finding that Latrunculin A abolishes the activated cone growth. The growth is assumed to be activated by cell signaling mediated by the invasin-specific integrins (exhibiting beta1 chains) and could play a role in phagocytic and protrusive events during immune response by macrophages.
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Affiliation(s)
- Laurent Vonna
- Physik Depatment E22 (biophysics group), Technische Universität München, D-85748 Garching, Germany.
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25
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Hochmuth RM, Marcus WD. Membrane tethers formed from blood cells with available area and determination of their adhesion energy. Biophys J 2002; 82:2964-9. [PMID: 12023219 PMCID: PMC1302084 DOI: 10.1016/s0006-3495(02)75637-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Fundamental to all mammalian cells is the adherence of the lipid bilayer membrane to the underlying membrane associated cytoskeleton. To investigate this adhesion, we physically detach the lipid membrane from the cell by mechanically forming membrane tethers. For the most part these have been tethers formed from either neutrophils or red cells. Here we do a simple thermodynamic analysis of the tether formation process using the entire cell, including tether, as the control volume. For a neutrophil, we show that the total adhesion energy per unit area between lipid membrane and cytoskeleton depends on the square of the tether force. For a flaccid red cell, we show that the total adhesion energy minus the tension in the spectrin cytoskeleton depends also on the square of the tether force. Finally, we discuss briefly the viscous flow of membrane. Using published data we calculate and compare values for the various adhesion energies and viscosities.
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Affiliation(s)
- Robert M Hochmuth
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708-0300, USA.
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26
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Veselská R, Janisch R. Reaction of the skin fibroblast cytoskeleton to micromanipulation interventions. J Struct Biol 2001; 136:110-8. [PMID: 11886212 DOI: 10.1006/jsbi.2001.4432] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Micromanipulation is a strong mechanical intervention into cellular integrity and induces large changes in the fine structure of the treated cells. Human diploid skin fibroblasts (KF1 and KF2 cell lines) were chosen as an experimental model. Special hatching needles were used for defined micromanipulation interventions (deformation of plasma membrane). Changes in cytoskeletal structures were visualized by using fluorescent and confocal microscopy. The actin cytoskeleton showed a more sensitive response to micromanipulation than microtubules. Characteristic changes in microfilaments, i.e., thickenings and knot formation, were visible in treated cells fixed immediately after micromanipulation and were the result of hatching-needle pressure on the plasma membrane as well as a reaction of actin filaments localized near the plasma membrane deformation. These direct changes and also other specific alterations in the actin filament network were detectable 14 to 16 h after treatment, but they were not observed when longer reparation intervals were used.
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Affiliation(s)
- R Veselská
- Cell Culture Laboratory, Department of Biology, Medical Faculty, Masaryk University, Brno, Czech Republic.
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27
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Hodgson L, Qiu W, Dong C, Henderson AJ. Use of green fluorescent protein-conjugated beta-actin as a novel molecular marker for in vitro tumor cell chemotaxis assay. Biotechnol Prog 2000; 16:1106-14. [PMID: 11101341 PMCID: PMC2852904 DOI: 10.1021/bp000093o] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To study the dynamics of actin cytoskeleton rearrangement in living cells, an eukaryotic expression vector expressing a beta-actin-GFP fusion protein was generated. The expression construct when transfected into NIH3T3 fibroblast, A2058 human melanoma and 293T human embryonic kidney carcinoma cell lines expressed beta-actin-GFP fusion protein, which colocalized with endogenous cellular actin as determined by histoimmunofluorescence staining. The beta-actin-GFP was also observed to be reorganized in response to treatments with the chemoattractant type IV collagen. Cells extended pseudopodial protrusions and altered the morphology of their cortical structure in response to type IV collagen stimulation. More importantly, beta-actin-GFP accumulated in areas undergoing these dynamic cytoskeleton changes, indicating that beta-actin-GFP could participate in actin polymerization. Although ectopic expression of beta-actin-GFP lead to minor side effects on cell proliferation, these studies suggest that this strategy provides an alternative to the invasive techniques currently used to study actin dynamics and permits real-time visualization of actin rearrangements in response to environmental cues.
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Affiliation(s)
- Louis Hodgson
- Department of Bioengineering, 229 Hallowell Building, 115 Henning Building, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Wei Qiu
- Department of Bioengineering, 229 Hallowell Building, 115 Henning Building, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Cheng Dong
- Department of Bioengineering, 229 Hallowell Building, 115 Henning Building, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Andrew J. Henderson
- Department of Veterinary Science, 115 Henning Building, Pennsylvania State University, University Park, Pennsylvania 16802
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28
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Schwarz EC, Neuhaus EM, Kistler C, Henkel AW, Soldati T. Dictyostelium myosin IK is involved in the maintenance of cortical tension and affects motility and phagocytosis. J Cell Sci 2000; 113 ( Pt 4):621-33. [PMID: 10652255 DOI: 10.1242/jcs.113.4.621] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dictyostelium discoideum myosin Ik (MyoK) is a novel type of myosin distinguished by a remarkable architecture. MyoK is related to class I myosins but lacks a cargo-binding tail domain and carries an insertion in a surface loop suggested to modulate motor velocity. This insertion shows similarity to a secondary actin-binding site present in the tail of some class I myosins, and indeed a GST-loop construct binds actin. Probably as a consequence, binding of MyoK to actin was not only ATP- but also salt-dependent. Moreover, as both binding sites reside within its motor domain and carry potential sites of regulation, MyoK might represent a new form of actin crosslinker. MyoK was distributed in the cytoplasm with a significant enrichment in dynamic regions of the cortex. Absence of MyoK resulted in a drop of cortical tension whereas overexpression led to significantly increased tension. Absence and overexpression of MyoK dramatically affected the cortical actin cytoskeleton and resulted in reduced initial rates of phagocytosis. Cells lacking MyoK showed excessive ruffling, mostly in the form of large lamellipodia, accompanied by a thicker basal actin cortex. At early stages of development, aggregation of myoK null cells was slowed due to reduced motility. Altogether, the data indicate a distinctive role for MyoK in the maintenance and dynamics of the cell cortex.
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Affiliation(s)
- E C Schwarz
- Department of Molecular Cell Research, Max-Planck-Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Germany
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29
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Kindzelskii AL, Petty HR. Extremely low frequency pulsed DC electric fields promote neutrophil extension, metabolic resonance and DNA damage when phase-matched with metabolic oscillators. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1495:90-111. [PMID: 10634935 DOI: 10.1016/s0167-4889(99)00148-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Application of extremely low frequency pulsed DC electric fields that are frequency- and phase-matched with endogenous metabolic oscillations leads to greatly exaggerated neutrophil extension and metabolic resonance wherein oscillatory NAD(P)H amplitudes are increased. In the presence of a resonant field, migrating cell length grows from 10 to approximately 40 microm, as does the overall length of microfilament assemblies. In contrast, cells stop locomotion and become spherical when exposed to phase-mismatched fields. Although cellular effects were not found to be dependent on electrode type and buffer, they were sensitive to temporal constraints (phase and pulse length) and cell surface charge. We suggest an electromechanical coupling hypothesis wherein applied electric fields and cytoskeletal polymerization forces act together to overcome the surface/cortical tension of neutrophils, thus promoting net cytoskeletal assembly and heightened metabolic amplitudes. Metabolic resonance enhances reactive oxygen metabolic production by neutrophils. Furthermore, cellular DNA damage was observed after prolonged metabolic resonance using both single cell gel electrophoresis ('comet' assay) and 3'-OH DNA labeling using terminal deoxynucleotidyl transferase. These results provide insights into transmembrane signal processing and cell interactions with weak electric fields.
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Affiliation(s)
- A L Kindzelskii
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
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30
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Yanai M, Butler JP, Suzuki T, Kanda A, Kurachi M, Tashiro H, Sasaki H. Intracellular elasticity and viscosity in the body, leading, and trailing regions of locomoting neutrophils. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:C432-40. [PMID: 10484330 DOI: 10.1152/ajpcell.1999.277.3.c432] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To investigate the mechanisms underlying pseudopod protrusion in locomoting neutrophils, we measured the intracellular stiffness and viscosity in the leading region, main body, and trailing region from displacements of oscillating intracellular granules driven with an optical trap. Experiments were done in control conditions and after treatment with cytochalasin D or nocodazole. We found 1) in the body and trailing region, the granules divided into a "fixed" population (too stiff to measure) and a "free" population (easily oscillated; fixed fraction 65%, free fraction 35%). By contrast, the fixed fraction in the leading region was <5%. 2) In the body and trailing region, there was no difference in stiffness or viscosity, but both were sharply lower in the leading region (respectively, 20-fold and 5-fold). 3) Neither cytochalasin D nor nocodazole caused a decrease in stiffness, but both treatments markedly reduced the fixed fraction in the body and trailing region to <20% and <40%, respectively. These observations suggest a discrete lattice structure in the body and trailing region and suggest that the developing pseudopod has a core that is more fluidlike, in the sense of a much lower viscosity and an almost total loss of stiffness. This is consistent with the contraction/solation hypothesis of pseudopodial formation.
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Affiliation(s)
- M Yanai
- Department of Geriatric and Respiratory Medicine, Tohoku University School of Medicine, Sendai 980-8574, Japan.
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31
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Dai J, Ting-Beall HP, Hochmuth RM, Sheetz MP, Titus MA. Myosin I contributes to the generation of resting cortical tension. Biophys J 1999; 77:1168-76. [PMID: 10423462 PMCID: PMC1300408 DOI: 10.1016/s0006-3495(99)76968-7] [Citation(s) in RCA: 144] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The amoeboid myosin I's are required for cellular cortical functions such as pseudopod formation and macropinocytosis, as demonstrated by the finding that Dictyostelium cells overexpressing or lacking one or more of these actin-based motors are defective in these processes. Defects in these processes are concomitant with changes in the actin-filled cortex of various Dictyostelium myosin I mutants. Given that the amoeboid myosin I's possess both actin- and membrane-binding domains, the mutant phenotypes could be due to alterations in the generation and/or regulation of cell cortical tension. This has been directly tested by analyzing mutant Dictyostelium that either lacks or overexpresses various myosin I's, using micropipette aspiration techniques. Dictyostelium cells lacking only one myosin I have normal levels of cortical tension. However, myosin I double mutants have significantly reduced (50%) cortical tension, and those that mildly overexpress an amoeboid myosin I exhibit increased cortical tension. Treatment of either type of mutant with the lectin concanavalin A (ConA) that cross-links surface receptors results in significant increases in cortical tension, suggesting that the contractile activity of these myosin I's is not controlled by this stimulus. These results demonstrate that myosin I's work cooperatively to contribute substantially to the generation of resting cortical tension that is required for efficient cell migration and macropinocytosis.
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Affiliation(s)
- J Dai
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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32
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Abstract
The dynamics of human neutrophils during micropipette aspiration are frequently analyzed by approximating these cells as simple slippery droplets of viscous fluid. Here, we present computations that reveal the detailed predictions of the simplest and most idealized case of such a scheme; namely, the case where the fluid of the droplet is homogeneous and Newtonian, and the surface tension of the droplet is constant. We have investigated the behavior of this model as a function of surface tension, droplet radius, viscosity, aspiration pressure, and pipette radius. In addition, we have tabulated a dimensionless factor, M, which can be utilized to calculate the apparent viscosity of the slippery droplet. Computations were carried out using a low Reynolds number hydrodynamics transport code based on the finite-element method. Although idealized and simplistic, we find that the slippery droplet model predicts many observed features of neutrophil aspiration. However, there are certain features that are not observed in neutrophils. In particular, the model predicts dilation of the membrane past the point of being continuous, as well as a reentrant jet at high aspiration pressures.
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Affiliation(s)
- J L Drury
- Department of Biomedical Engineering, Boston University, Boston, MA 02215 USA
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33
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Choquet D, Felsenfeld DP, Sheetz MP. Extracellular matrix rigidity causes strengthening of integrin-cytoskeleton linkages. Cell 1997; 88:39-48. [PMID: 9019403 DOI: 10.1016/s0092-8674(00)81856-5] [Citation(s) in RCA: 875] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
To move forward, migrating cells must generate traction forces through surface receptors bound to extracellular matrix molecules coupled to a rigid structure. We investigated whether cells sample and respond to the rigidity of the anchoring matrix. Movement of beads coated with fibronectin or an anti-integrin antibody was restrained with an optical trap on fibroblasts to mimic extracellular attachment sites of different resistance. Cells precisely sense the restraining force on fibronectin beads and respond by a localized, proportional strengthening of the cytoskeleton linkages, allowing stronger force to be exerted on the integrins. This strengthening was absent or transient with antibody beads, but restored with soluble fibronectin. Hence, ligand binding site occupancy was required. Finally, phenylarsine oxide inhibited strengthening of cytoskeletal linkages, indicating a role for dephosphorylation. Thus, the strength of integrin-cytoskeleton linkages is dependent on matrix rigidity and on its biochemical composition. Matrix rigidity may, therefore, serve as a guidance cue in a process of mechanotaxis.
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Affiliation(s)
- D Choquet
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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34
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Affiliation(s)
- D A Lauffenburger
- Center for Biomedical Engineering, Massachusetts Institute of Technology Cambridge 02139, USA
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35
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36
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Zhelev DV, Alteraifi AM, Hochmuth RM. F-actin network formation in tethers and in pseudopods stimulated by chemoattractant. CELL MOTILITY AND THE CYTOSKELETON 1996; 35:331-44. [PMID: 8956004 DOI: 10.1002/(sici)1097-0169(1996)35:4<331::aid-cm5>3.0.co;2-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Micropipets are used either to deliver a given concentration of the chemoattractant N-formyl-methionyl-leucyl-phenylalanine (fMLP) to a local region of a human neutrophil or to create a membrane tether. Pseudopods, which have a cylindrical shape and grow at a constant rate, are formed in either case. After reaching a maximum extension, they retract, even in the presence of chemoattractant. As a pseudopod grows, cell granules begin to penetrate the pseudopod region to a "boundary" that defines a distance to the pseudopod's leading edge that is almost constant. The exclusion of granules from this domain indicates that it is filled with a dense network. The formation of this network involves the plasma membrane because pseudopod growth ceases when a membrane tether is pulled away from the leading edge. The rate of pseudopod growth depends on fMLP concentration just as the number of occupied N-formyl peptide receptors depends on this concentration. The experimental data are explained by assuming that F-actin network is formed next to the plasma membrane. The newly formed network displaces the membrane and the dominant process in the network region then becomes F-actin depolymerization. The rate of pseudopod growth is determined by the rate of the process leading to network formation. This process is apparently an enzymatic type of reaction. It has a positive enthalpy change and, therefore, is endothermic.
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Affiliation(s)
- D V Zhelev
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708-0300, USA
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