UMR168 – Laboratoire Physico-Chimie Curie

Publications de l’UMR 168

Année de publication : 2014

Havrylenko S, Mezanges X, Batchelder E, Plastino J (2014 Oct 1)

Extending the molecular clutch beyond actin-based cell motility

New Journal of Physics : 16 : 105012 : DOI : 10.1088/1367-2630/16/10/105012 En savoir plus
Résumé

Many cell movements occur via polymerization of the actin cytoskeleton beneath the plasma membrane at the front of the cell, forming a protrusion called a lamellipodium, while myosin contraction squeezes forward the back of the cell. In what is known as the « molecular clutch » description of cell motility, forward movement results from the engagement of the acto-myosin motor with cell-matrix adhesions, thus transmitting force to the substrate and producing movement. However during cell translocation, clutch engagement is not perfect, and as a result, the cytoskeleton slips with respect to the substrate, undergoing backward (retrograde) flow in the direction of the cell body. Retrograde flow is therefore inversely proportional to cell speed and depends on adhesion and acto-myosin dynamics. Here we asked whether the molecular clutch was a general mechanism by measuring motility and retrograde flow for the Caenorhabditis elegans sperm cell in different adhesive conditions. These cells move by adhering to the substrate and emitting a dynamic lamellipodium, but the sperm cell does not contain an acto-myosin cytoskeleton. Instead the lamellipodium is formed by the assembly of Major Sperm Protein (MSP), which has no biochemical or structural similarity to actin. We find that these cells display the same molecular clutch characteristics as acto-myosin containing cells. We further show that retrograde flow is produced both by cytoskeletal assembly and contractility in these cells. Overall this study shows that the molecular clutch hypothesis of how polymerization is transduced into motility via adhesions is a general description of cell movement regardless of the composition of the cytoskeleton.

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Pascal Martin (2014 Aug 21)

All that jazz coming out of my ears.

Biophysical journal : 800-2 : DOI : 10.1016/j.bpj.2014.07.011 En savoir plus
Résumé

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Bussonnier M, Carvalho K, Lemière J, Joanny JF, Sykes C, Betz T (2014 Aug 19)

Mechanical detection of a long-range actin network emanating from a biomimetic cortex

Biophysical Journal : 107 : 854-62 : DOI : 10.1016/j.bpj.2014.07.008 En savoir plus
Résumé

Actin is ubiquitous globular protein that polymerizes into filaments and forms networks that participate in the force generation of eukaryotic cells. Such forces are used for cell motility, cytokinesis, and tissue remodeling. Among those actin networks, we focus on the actin cortex, a dense branched network beneath the plasma membrane that is of particular importance for the mechanical properties of the cell. Here we reproduce the cellular cortex by activating actin filament growth on a solid surface. We unveil the existence of a sparse actin network that emanates from the surface and extends over a distance that is at least 10 times larger than the cortex itself. We call this sparse actin network the « actin cloud » and characterize its mechanical properties with optical tweezers. We show, both experimentally and theoretically, that the actin cloud is mechanically relevant and that it should be taken into account because it can sustain forces as high as several picoNewtons (pN). In particular, it is known that in plant cells, actin networks similar to the actin cloud have a role in positioning the nucleus; in large oocytes, they play a role in driving chromosome movement. Recent evidence shows that such networks even prevent granule condensation in large cells.

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Philippe Bun, JunJun Liu, Hervé Turlier, ZengZhen Liu, Karen Uriot, Jean-François Joanny, Maïté Coppey-Moisan (2014 Jul 17)

Mechanical checkpoint for persistent cell polarization in adhesion-naive fibroblasts.

Biophysical journal : 324-35 : DOI : 10.1016/j.bpj.2014.05.041 En savoir plus
Résumé

Cell polarization is a fundamental biological process implicated in nearly every aspect of multicellular development. The role of cell-extracellular matrix contacts in the establishment and the orientation of cell polarity have been extensively studied. However, the respective contributions of substrate mechanics and biochemistry remain unclear. Here we propose a believed novel single-cell approach to assess the minimal polarization trigger. Using nonadhered round fibroblast cells, we show that stiffness sensing through single localized integrin-mediated cues are necessary and sufficient to trigger and direct a shape polarization. In addition, the traction force developed by cells has to reach a minimal threshold of 56 ± 1.6 pN for persistent polarization. The polarization kinetics increases with the stiffness of the cue. The polarized state is characterized by cortical actomyosin redistribution together with cell shape change. We develop a physical model supporting the idea that a local and persistent inhibition of actin polymerization and/or myosin activity is sufficient to trigger and sustain the polarized state. Finally, the cortical polarity propagates to an intracellular polarity, evidenced by the reorientation of the centrosome. Our results define the minimal adhesive requirements and quantify the mechanical checkpoint for persistent cell shape and organelle polarization, which are critical regulators of tissue and cell development.

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Ayako Yamada, Sungyon Lee, Patricia Bassereau, Charles N Baroud (2014 Jun 17)

Trapping and release of giant unilamellar vesicles in microfluidic wells.

Soft matter : 5878-85 : DOI : 10.1039/c4sm00065j En savoir plus
Résumé

We describe the trapping and release of giant unilamellar vesicles (GUVs) in a thin and wide microfluidic channel, As They cross indentations etched in the channel ceiling. This trapping results from the reduction of the membrane elastic energy, qui est Stored in the GUV as it squeezes to enter into the thin channel. We Demonstrate That GUVs Whose diameter is Slightly larger than the channel height can be trapped and That They Can be untrapped by the outer fluid flowing beyond a critical velocity. GUVs smaller than the flow channel height undisturbed while much larger Those can not squeeze into the thin regions. Within the ranks That allows trapping, larger GUVs are anchored more than smaller Strongly GUVs. The Ability to trap vesicles Provides access to the optical GUVs for extended Periods of time; this allows the observation of recirculation flow on the surface area of ​​the GUVs, in the direction of forward near the mid-plane of the channel and in the reverse direction of elsewhere. We also obtenir the shape of GUVs under different flow requirements through confocal microscopy. This geometric information is used to drift a mechanical model of the power balance That equates the viscous effects from the outer flow with the elastic effects based on the variation of the membrane stretching energy. This model yields Good agreement with the experimental data values ​​When stretching of the moduli are taken from the scientific literature. This microfluidic approach Provides a New Way of Storing a wide number of GUVs at specific locations, with or without the presence of an outer flow. As Such, it was deriving their high-throughput alternative to micropipette manipulation of individual chemical or biological GUVs for applications.

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Jana Kucerova, Zuzana Svobodova, Petr Knotek, Jiri Palarcik, Milan Vlcek, Miloslav Kincl, Daniel Horak, Julien Autebert, Jean-Louis Viovy, Zuzana Bilkova (2014 May 27)

PEGylation of magnetic poly(glycidyl methacrylate) microparticles for microfluidic bioassays.

Materials science & engineering. C, Materials for biological applications : 308-15 : DOI : 10.1016/j.msec.2014.04.011 En savoir plus
Résumé

In this study, magnetic poly(glycidyl methacrylate) microparticles containing carboxyl groups (PGMA-COOH) were coated using highly hydrophilic polymer poly(ethylene glycol) (PEG). PEG was used to reduce nonspecific interactions with proteins and cells while decreasing adhesion of particles to the walls of a microfluidic devices from poly(dimethylsiloxane) (PDMS) and cyclic olefin copolymer (COC). Zeta potential measurement, infrared spectroscopy, scanning electron microscopy, anti-PEG ELISA assay, and bioaffinity interactions between biotin and streptavidin-HRP successfully proved the presence of PEG on the surface of microspheres. Both neat and PEGylated microspheres were then incubated with the inert protein bovine serum albumin or cells to evaluate the rate of nonspecific adsorption (NSA). PEG with Mr of 30,000 Da was responsible for 45% reduction in NSA of proteins and 74% for cells compared to neat particles. The microspheres’ behavior in PDMS and COC microchannels was then evaluated. Aggregation and adhesion of PEGylated microspheres significantly decreased compared to neat particles. Finally, the model enzyme horseradish peroxidase was immobilized on the microspheres through the heterobifunctional PEG chain. The possibility for subsequent covalent coupling of the ligand of interest was confirmed. Such PEGylated microparticles can be efficiently used in PDMS microchips as a carrier for bioaffinity separation or of enzyme for catalysis.

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C Blanch-Mercader, J Casademunt, J F Joanny (2014 May 24)

Morphology and growth of polarized tissues.

The European physical journal. E, Soft matter : 41 : DOI : 10.1140/epje/i2014-14041-2 En savoir plus
Résumé

We study and classify the time-dependent morphologies of polarized tissues subject to anisotropic but spatially homogeneous growth. Extending previous studies, we model the tissue as a fluid, and discuss the interplay of the active stresses generated by the anisotropic cell division and three types of passive mechanical forces: viscous stresses, friction with the environment and tension at the tissue boundary. The morphology dynamics is formulated as a free-boundary problem, and conformal mapping techniques are used to solve the evolution numerically. We combine analytical and numerical results to elucidate how the different passive forces compete with the active stresses to shape the tissue in different temporal regimes and derive the corresponding scaling laws. We show that in general the aspect ratio of elongated tissues is non-monotonic in time, eventually recovering isotropic shapes in the presence of friction forces, which are asymptotically dominant.

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Lin Jia, Di Cui, Jérôme Bignon, Aurelie Di Cicco, Joanna Wdzieczak-Bakala, Jianmiao Liu, Min-Hui Li (2014 May 19)

Reduction-responsive cholesterol-based block copolymer vesicles for drug delivery.

Biomacromolecules : 2206-17 : DOI : 10.1021/bm5003569 En savoir plus
Résumé

We developed a new robust reduction-responsive polymersome based on the amphiphilic block copolymer PEG-SS-PAChol. The stability and robustness were achieved by the smectic physical cross-linking of cholesterol-containing liquid crystal polymer PAChol in the hydrophobic layer. The reduction-sensitivity was introduced by the disulfide bridge (-S-S-) that links the hydrophilic PEG block and the hydrophobic PAChol block. We used a versatile synthetic strategy based on atom transfer radical polymerization (ATRP) to synthesize the reduction-responsive amphiphilic block copolymers. The reductive cleavage of the disulfide bridge in the block copolymers was first evidenced in organic solution. The partial destruction of PEG-SS-PAChol polymersomes in the presence of a reducing agent was then demonstrated by cryo-electron microscopy. Finally, the calcein release from PEG-SS-PAChol polymersomes triggered by glutathione (GSH) was observed both in PBS suspension and in vitro inside the macrophage cells. High GSH concentrations (≥35 mM in PBS or artificially enhanced in macrophage cells by GSH-OEt pretreatment) and long incubation time (in the order of hours) were, however, necessary to get significant calcein release. These polymersomes could be used as drug carriers with very long circulation profiles and slow release kinetics.

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Laura Picas, Julien Viaud, Kristine Schauer, Stefano Vanni, Karim Hnia, Vincent Fraisier, Aurélien Roux, Patricia Bassereau, Frédérique Gaits-Iacovoni, Bernard Payrastre, Jocelyn Laporte, Jean-Baptiste Manneville, Bruno Goud (2014 May 19)

BIN1/M-Amphiphysin2 induces clustering of phosphoinositides to recruit its downstream partner dynamin.

Nature communications : 5647 : DOI : 10.1038/ncomms6647 En savoir plus
Résumé

Phosphoinositide play a central role in physiological processes by Many Assisting the recruitment of proteins to membranes through specific phosphoinositide-binding motifs. How is this recruitment Coordinated in space and time is not well Understood. Here we show That BIN1 / M-Amphiphysin2, a protein Involved in T-tubule biogenesis in muscle cells and frequently mutated in centronuclear myopathies, clusters PtdIns (4,5) P2 to recruit ict downstream partner dynamin. By using Several mutants associated with centronuclear myopathies, we find that N-BAR and the SH3 domains of BIN1 control the kinetics and the accumulation of dynamin we membranes, respectively. We that show phosphoinositide Clustering is a mechanism shared by –other That proteins interact with PtdIns (4,5) P2, do not aim to contain a BAR domain. Our numerical simulations Point Out That clustering is a diffusion-driven process in which molecules are not sequestered phosphoinositide. We propose That this mechanism plays a key role in the recruitment of downstream phosphoinositide-binding proteins.

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Deforet M, Hakim V, Yevick HG, Duclos G, Silberzan P (2014 May 6)

Emergence of collective modes and tri-dimensional structures from epithelial confinement.

Nat Commun5:3747 : DOI : 10.1038/ncomms4747 En savoir plus
Résumé

Many in vivo processes, including morphogenesis or tumour maturation, involve small populations of cells within a spatially restricted region. However, the basic mechanisms underlying the dynamics of confined cell assemblies remain largely to be deciphered and would greatly benefit from well-controlled in vitro experiments. Here we show that confluent epithelial cells cultured on finite population-sized domains, exhibit collective low-frequency radial displacement modes as well as stochastic global rotation reversals. A simple mathematical model, in which cells are described as persistent random walkers that adapt their motion to that of their neighbours, captures the essential characteristics of these breathing oscillations. As these epithelia mature, a tri-dimensional peripheral cell cord develops at the domain edge by differential extrusion, as a result of the additional degrees of freedom of the border cells. These results demonstrate that epithelial confinement alone can induce morphogenesis-like processes including spontaneous collective pulsations and transition from 2D to 3D.

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Volker Bormuth, Jérémie Barral, Jean-François Joanny, Frank Jülicher, Pascal Martin (2014 May 5)

Transduction channels’ gating can control friction on vibrating hair-cell bundles in the ear.

Proceedings of the National Academy of Sciences of the United States of America : 7185-90 : DOI : 10.1073/pnas.1402556111 En savoir plus
Résumé

Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. Friction is generally thought to result mainly from viscous drag by the surrounding fluid. We demonstrate here that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle. We characterized friction by analyzing hysteresis in the force-displacement relation of single hair-cell bundles in response to periodic triangular stimuli. For bundle velocities high enough to outrun adaptation, we found that frictional forces were maximal within the narrow region of deflections that elicited significant channel gating, plummeted upon application of a channel blocker, and displayed a sublinear growth for increasing bundle velocity. At low velocity, the slope of the relation between the frictional force and velocity was nearly fivefold larger than the hydrodynamic friction coefficient that was measured when the transduction machinery was decoupled from bundle motion by severing tip links. A theoretical analysis reveals that channel friction arises from coupling the dynamics of the conformational change associated with channel gating to tip-link tension. Varying channel properties affects friction, with faster channels producing smaller friction. We propose that this intrinsic source of friction may contribute to the process that sets the hair cell’s characteristic frequency of responsiveness.

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Philippe Marcq (2014 Apr 29)

Spatio-temporal dynamics of an active, polar, viscoelastic ring.

The European physical journal. E, Soft matter : 29 : DOI : 10.1140/epje/i2014-14029-x En savoir plus
Résumé

Constitutive equations for a one-dimensional, active, polar, viscoelastic liquid are derived by treating the strain field as a slow hydrodynamic variable. Taking into account the couplings between strain and polarity allowed by symmetry, the hydrodynamics of an active, polar, viscoelastic body include an evolution equation for the polarity field that generalizes the damped Kuramoto-Sivashinsky equation. Beyond thresholds of the active coupling coefficients between the polarity and the stress or the strain rate, bifurcations of the homogeneous state lead first to stationary waves, then to propagating waves of the strain, stress and polarity fields. I argue that these results are relevant to living matter, and may explain rotating actomyosin rings in cells and mechanical waves in epithelial cell monolayers.

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Reffay M, Parrini MC, Cochet-Escartin O, Ladoux B, Buguin A, Coscoy S, Amblard F, Camonis J, Silberzan P (2014 Apr 16)

Interplay of RhoA and mechanical forces in collective cell migration driven by leader cells

Nat Cell Biol16(4):382 : DOI : 10.1038/ncb2917 En savoir plus
Résumé

The leading front of a collectively migrating epithelium often destabilizes into multicellular migration fingers where a cell initially similar to the others becomes a leader cell while its neighbours do not alter. The determinants of these leader cells include mechanical and biochemical cues, often under the control of small GTPases. However, an accurate dynamic cartography of both mechanical and biochemical activities remains to be established. Here, by mapping the mechanical traction forces exerted on the surface by MDCK migration fingers, we show that these structures are mechanical global entities with the leader cells exerting a large traction force. Moreover, the spatial distribution of RhoA differential activity at the basal plane strikingly mirrors this force cartography. We propose that RhoA controls the development of these fingers through mechanical cues: the leader cell drags the structure and the peripheral pluricellular acto-myosin cable prevents the initiation of new leader cells.

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Shalin H Naik, Ton N Schumacher, Leïla Perié (2014 Apr 15)

Cellular barcoding: a technical appraisal.

Experimental hematology : 598-608 : DOI : 10.1016/j.exphem.2014.05.003 En savoir plus
Résumé

Cellular barcoding involves the tagging of individual cells of interest with unique genetic heritable identifiers or barcodes and is emerging as a powerful tool to address individual cell fates on a large scale. However, as with many new technologies, diverse technical and analytical challenges have emerged. Here, we review those challenges and highlight both the power and limitations of cellular barcoding. We then illustrate the contribution of cellular barcoding to the understanding of hematopoiesis and outline the future potential of this technology.

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Ayako Yamada, Alexandre Mamane, Jonathan Lee-Tin-Wah, Aurélie Di Cicco, Coline Prévost, Daniel Lévy, Jean-François Joanny, Evelyne Coudrier*, Patricia Bassereau* (2014 Apr 7)

Catch-bond behaviour facilitates membrane tubulation by non-processive myosin 1b.

Nature communications : 3624 : DOI : 10.1038/ncomms4624 En savoir plus
Résumé

Myosin 1b is a single-headed membrane-associated motor actin filaments to That Bind with a catch-hop behavior in response to load. In vivo, myosin 1b is required to form membrane tubules at Both endosomes and the trans-Golgi network. To suit les the link entre thesis Fundamental two properties, here we Investigate the capacity of myosin 1b to extract membrane tubes along bundled actin filaments in a minimum reconstituted system. We that show single-headed non-processive myosin 1b can extract membrane tubes at biologically relevant low density. In contrast to kinesins we do not observe motor accumulation at the tip, Suggesting que la Underlying mechanism for tube formation is different. In our theoretical model, myosin 1b catch-bond properties Facilitate tube extraction under the conditions of membrane voltage by Increasing Reducing the density of myo1b required to pull tubes.

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