UMR168 – Laboratoire Physico-Chimie Curie

Publications de l’UMR 168

Année de publication : 2019

Mijo Simunovic, Emma Evergren, Andrew Callan-Jones*, Patricia Bassereau* (2019 Oct 7)

Curving Cells Inside and Out: Roles of BAR Domain Proteins in Membrane Shaping and Its Cellular Implications.

Annual Review of Cell and Developmental Biology : 35 : DOI : 10.1146/annurev-cellbio-100617-060558 En savoir plus
Résumé

Many cellular processes rely on precise and timely deformation of the cell membrane. While many proteins participate in membrane reshaping and scission, usually in highly specialized ways, Bin/amphiphysin/Rvs (BAR) domain proteins play a pervasive role, as they not only participate in many aspects of cell trafficking but also are highly versatile membrane remodelers. Subtle changes in the shape and size of the BAR domain can greatly impact the way in which BAR domain proteins interact with the membrane. Furthermore, the activity of BAR domain proteins can be tuned by external physical parameters, and so they behave differently depending on protein surface density, membrane tension, or membrane shape. These proteins can form 3D structures that mold the membrane and alter its liquid properties, even promoting scission under various circumstances. As such, BAR domain proteins have numerous roles within the cell. Endocytosis is among the most highly studied processes in which BAR domain proteins take on important roles. Over the years, a more complete picture has emerged in which BAR domain proteins are tied to almost all intracellular compartments; examples include endosomal sorting and tubular networks in the endoplasmic reticulum and T-tubules. These proteins also have a role in autophagy, and their activity has been linked with cancer. Here, we briefly review the history of BAR domain protein discovery, discuss the mechanisms by which BAR domain proteins induce curvature, and attempt to settle important controversies in the field. Finally, we review BAR domain proteins in the context of a cell, highlighting their emerging roles in cell signaling and organelle shaping.

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Moitrier Sarah, Pricoupenko Nastassia, Kerjouan Adèle, Oddou Christiane, Destaing Olivier, Battistella Aude, Silberzan Pascal, Bonnet Isabelle (2019 Sep 3)

Local light-activation of the Src oncoprotein in an epithelial monolayer promotes collective extrusion

Communications Physics : 2 : 98 : DOI : 10.1038/s42005-019-0198-5 En savoir plus
Résumé

Transformed isolated cells are usually extruded from normal epithelia and subsequently eliminated. However, multicellular tumors outcompete healthy cells, highlighting the importance of collective effects. Here, we investigate this situation in vitro by controlling in space and time the activity of the Src oncoprotein within a normal Madin–Darby Canine Kidney (MDCK) epithelial cell monolayer. Using an optogenetics approach with cells expressing a synthetic light-sensitive version of Src (optoSrc), we reversibly trigger the oncogenic activity by exposing monolayers to well-defined light patterns. We show that small populations of activated optoSrc cells embedded in the non-transformed monolayer collectively extrude as a tridimensional aggregate and remain alive, while the surrounding normal cells migrate towards the exposed area. This phenomenon requires an interface between normal and transformed cells and is partially reversible. Traction forces show that Src- activated cells either actively extrude or are pushed out by the surrounding cells in a non- autonomous way.

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Zack Jarin, Feng-Ching Tsai, Aram Davtyan, Alexander J.Pak, Patricia Bassereau, Gregory A.Voth (2019 Aug 6)

Unusual Organization of I-BAR Proteins on Tubular and Vesicular Membranes.

Biophysical Journal : 117 : 553-562 : DOI : 10.1016/j.bpj.2019.06.025 En savoir plus
Résumé

Protein-mediated membrane remodeling is a ubiquitous and critical process for proper cellular function. Inverse Bin/Amphiphysin/Rvs (I-BAR) domains drive local membrane deformation as a precursor to large-scale membrane remodeling. We employ a multiscale approach to provide the molecular mechanism of unusual I-BAR domain-driven membrane remodeling at a low protein surface concentration with near-atomistic detail. We generate a bottom-up coarse-grained model that demonstrates similar membrane-bound I-BAR domain aggregation behavior as our recent Mesoscopic Membrane with Explicit Proteins model. Together, these models bridge several length scales and reveal an aggregation behavior of I-BAR domains. We find that at low surface coverage (i.e., low bound protein density), I-BAR domains form transient, tip-to-tip strings on periodic flat membrane sheets. Inside of lipid bilayer tubules, we find linear aggregates parallel to the axis of the tubule. Finally, we find that I-BAR domains form tip-to-tip aggregates around the edges of membrane domes. These results are supported by in vitro experiments showing low curvature bulges surrounded by I-BAR domains on giant unilamellar vesicles. Overall, our models reveal new I-BAR domain aggregation behavior in membrane tubules and on the surface of vesicles at low surface concentration that add insight into how I-BAR domain proteins may contribute to certain aspects of membrane remodeling in cells.

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Mathieu Richard, Carles Blanch-Mercader, Hajer Ennomani, Wenxiang Cao, Enrique M De La Cruz, Jean-François Joanny, Frank Jülicher, Laurent Blanchoin, Pascal Martin (2019 Jul 11)

Active cargo positioning in antiparallel transport networks.

Proceedings of the National Academy of Sciences of the United States of America : DOI : 10.1073/pnas.1900416116 En savoir plus
Résumé

Cytoskeletal filaments assemble into dense parallel, antiparallel, or disordered networks, providing a complex environment for active cargo transport and positioning by molecular motors. The interplay between the network architecture and intrinsic motor properties clearly affects transport properties but remains poorly understood. Here, by using surface micropatterns of actin polymerization, we investigate stochastic transport properties of colloidal beads in antiparallel networks of overlapping actin filaments. We found that 200-nm beads coated with myosin Va motors displayed directed movements toward positions where the net polarity of the actin network vanished, accumulating there. The bead distribution was dictated by the spatial profiles of local bead velocity and diffusion coefficient, indicating that a diffusion-drift process was at work. Remarkably, beads coated with heavy-mero-myosin II motors showed a similar behavior. However, although velocity gradients were steeper with myosin II, the much larger bead diffusion observed with this motor resulted in less precise positioning. Our observations are well described by a 3-state model, in which active beads locally sense the net polarity of the network by frequently detaching from and reattaching to the filaments. A stochastic sequence of processive runs and diffusive searches results in a biased random walk. The precision of bead positioning is set by the gradient of net actin polarity in the network and by the run length of the cargo in an attached state. Our results unveiled physical rules for cargo transport and positioning in networks of mixed polarity.

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Nicola de Franceschi, Maryam Alqabandi, Winfried Weissenhorn, Patricia Bassereau (2019 Jul 5)

Dynamic and Sequential Protein Reconstitution on Negatively Curved Membranes by Giant Vesicles Fusion.

Bio-Protocol : 9 : e3294 : DOI : 10.21769/BioProtoc.3294 En savoir plus
Résumé

In vitro investigation of the interaction between proteins and positively curved membranes can be performed using a classic nanotube pulling method. However, characterizing protein interaction with negatively curved membranes still represents a formidable challenge. Here, we describe our recently developed approach based on laser-triggered Giant Unilamellar Vesicles (GUVs) fusion. Our protocol allows sequential addition of proteins to a negatively curved membrane, while at the same time controlling the buffer composition, lipid composition and membrane tension. Moreover, this method does not require a step of protein detachment, greatly simplifying the process of protein encapsulation over existing methods.

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Elena Beltrán-Heredia, Feng-Ching Tsai, Samuel Salinas-Almaguer, Francisco J. Cao*, Patricia Bassereau*, Francisco Monroy* (2019 Jun 20)

Membrane curvature induces cardiolipin sorting.

Communications Biology : 2 : 225 : DOI : 10.1038/s42003-019-0471-x En savoir plus
Résumé

Cardiolipin is a cone-shaped lipid predominantly localized in curved membrane sites of bacteria and in the mitochondrial cristae. This specific localization has been argued to be geometry-driven, since the CL’s conical shape relaxes curvature frustration. Although previous evidence suggests a coupling between CL concentration and membrane shape in vivo, no precise experimental data are available for curvature-based CL sorting in vitro. Here, we test this hypothesis in experiments that isolate the effects of membrane curvature in lipid-bilayer nanotubes. CL sorting is observed with increasing tube curvature, reaching a maximum at optimal CL concentrations, a fact compatible with self-associative clustering. Observations are compatible with a model of membrane elasticity including van der Waals entropy, from which a negative intrinsic curvature of -1.1 nm-1 is predicted for CL. The results contribute to understanding the physicochemical interplay between membrane curvature and composition, providing key insights into mitochondrial and bacterial membrane organization and dynamics.

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Mélanie Tobin, Atitheb Chaiyasitdhi, Vincent Michel, Nicolas Michalski, Pascal Martin (2019 Apr 2)

Stiffness and tension gradients of the hair cell’s tip-link complex in the mammalian cochlea.

eLife : DOI : 10.7554/eLife.43473 En savoir plus
Résumé

Sound analysis by the cochlea relies on frequency tuning of mechanosensory hair cells along a tonotopic axis. To clarify the underlying biophysical mechanism, we have investigated the micromechanical properties of the hair cell’s mechanoreceptive hair bundle within the apical half of the rat cochlea. We studied both inner and outer hair cells, which send nervous signals to the brain and amplify cochlear vibrations, respectively. We find that tonotopy is associated with gradients of stiffness and resting mechanical tension, with steeper gradients for outer hair cells, emphasizing the division of labor between the two hair-cell types. We demonstrate that tension in the tip links that convey force to the mechano-electrical transduction channels increases at reduced Ca. Finally, we reveal gradients in stiffness and tension at the level of a single tip link. We conclude that mechanical gradients of the tip-link complex may help specify the characteristic frequency of the hair cell.

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Joanna Podkalicka, Patricia Bassereau (2019 Apr 1)

How membrane physics rules the HIV envelope.

Nature Cell Biology : 21 : 413–415 : DOI : 10.1038/s41556-019-0312-7 En savoir plus
Résumé

HIV particles incorporate host membrane proteins into their envelope to evade the immune system and infect other cells. A study now shows that Gag assembly on the host cell membrane produces a raft-like nanodomain favourable for protein partitioning due to a transbilayer coupling mechanism assisted by long saturated chain lipids and cholesterol.

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Simon C*, Kusters R*, Caorsi V*, Allard A, Abou-Ghali M, Manzi J, Di Cicco A, Lévy D, Lenz M, Joanny J-F, Campillo C, Plastino J, Sens P*, Sykes C* (2019 Mar 18)

Actin dynamics drive cell-like membrane deformation

Nature Physics : DOI : 10.1038/s41567-019-0464-1 En savoir plus
Résumé

Cell membrane deformations are crucial for proper cell function. Specialized protein assemblies initiate inward or outward membrane deformations that the cell uses respectively to uptake external substances or probe the environment. The assembly and dynamics of the actin cytoskeleton are involved in this process, although their detailed role remains controversial. We show here that a dynamic, branched actin network is sufficient to initiate both inward and outward membrane deformation. The polymerization of a dense actin network at the membrane of liposomes produces inward membrane bending at low tension, while outward deformations are robustly generated regardless of tension. Our results shed light on the mechanism cells use to internalize material, both in mammalian cells, where actin polymerization forces are required when membrane tension is increased, and in yeast, where those forces are necessary to overcome the opposing turgor pressure. By combining experimental observations with physical modelling, we propose a mechanism that explains how membrane tension and the architecture of the actin network regulate cell-like membrane deformations.

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Sarah Moitrier, Carles Blanch-Mercader, Simon Garcia, Kristina Sliogeryte,abc Tobias Martin, Jacques Camonis, Philippe Marcq, Pascal Silberzan and Isabelle Bonnet (2019 Feb 4)

Collective stresses drive competition between monolayers of normal and Ras-transformed cells

Soft Matter : 15 : DOI : 10.1039/C8SM01523F En savoir plus
Résumé

We study the competition for space between two cell lines that differ only in the expression of the Ras oncogene. The two cell populations are initially separated and set to migrate antagonistically towards an in-between stripe of free substrate. After contact, their interface moves towards the population of normal cells. We interpret the velocity and traction force data taken before and after contact thanks to a hydrodynamic description of collectively migrating cohesive cell sheets. The kinematics of cells, before and after contact, allows us to estimate the relative material parameters for both cell lines. As predicted by the model, the transformed cell population with larger collective stresses pushes the wild type cell population.

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Année de publication : 2018

Cáceres R, Bojanala N, Kelley LC, Dreier J, Manzi J, Di Federico F, Chi Q, Risler T, Testa I, Sherwood DR, Plastino J (2018 Nov 6)

Forces drive basement membrane invasion in Caenorhabditis elegans

Proceedings of the National Academy of Sciences USA : 115 : 11537-11542 : DOI : 10.1073/pnas.1808760115 En savoir plus
Résumé

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Vincent Nier, Grégoire Peyret, Joseph d'Alessandro, Shuji Ishihara, Benoit Ladoux, Philippe Marcq (2018 Oct 11)

Kalman Inversion Stress Microscopy.

Biophysical journal : DOI : S0006-3495(18)31065-8 En savoir plus
Résumé

Although mechanical cues are crucial to tissue morphogenesis and development, the tissue mechanical stress field remains poorly characterized. Given traction force time-lapse movies, as obtained by traction force microscopy of in vitro cellular sheets, we show that the tissue stress field can be estimated by Kalman filtering. After validation using numerical data, we apply Kalman inversion stress microscopy to experimental data. We combine the inferred stress field with velocity and cell-shape measurements to quantify the rheology of epithelial cell monolayers in physiological conditions, found to be close to that of an elastic and active material.

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Duclos G., Blanch-Mercader C., Yashunsky V., Salbreux G., Joanny J.-F., Prost J., Silberzan P. (2018 Oct 3)

Spontaneous shear flow in confined cellular nematics

Nature Physics : DOI : 10.1038/s41567-018-0099-7 En savoir plus
Résumé

In embryonic development or tumour evolution, cells often migrate collectively within confining tracks defined by their microenvironment1,2. In some of these situations, the displacements within a cell strand are antiparallel3, giving rise to shear flows. However, the mechanisms underlying these spontaneous flows remain poorly understood. Here, we show that an ensemble of spindle-shaped cells plated in a well-defined stripe spontaneously develops a shear flow whose characteristics depend on the width of the stripe. On wide stripes, the cells self-organize in a nematic phase with a director at a well-defined angle with the stripe’s direction, and develop a shear flow close to the stripe’s edges. However, on stripes narrower than a critical width, the cells perfectly align with the stripe’s direction and the net flow vanishes. A hydrodynamic active gel theory provides an understanding of these observations and identifies the transition between the non-flowing phase oriented along the stripe and the tilted phase exhibiting shear flow as a Fréedericksz transition driven by the activity of the cells. This physical theory is grounded in the active nature of the cells and based on symmetries and conservation laws, providing a generic mechanism to interpret in vivo antiparallel cell displacements.

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Plastino J, Blanchoin L (2018 Aug 13)

Dynamic stability of the actin ecosystem

Journal of Cell Science : 132 : pii: jcs219832 : DOI : 10.1242/jcs.219832 En savoir plus
Résumé

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Camille Clément, Guillermo A Orsi, Alberto Gatto, Ekaterina Boyarchuk, Audrey Forest, Bassam Hajj, Judith Miné-Hattab, Mickaël Garnier, Zachary A Gurard-Levin, Jean-Pierre Quivy, Geneviève Almouzni (2018 Aug 9)

High-resolution visualization of H3 variants during replication reveals their controlled recycling

Nature communications : 9 : DOI : 10.1038/s41467-018-05697-1 En savoir plus
Résumé

DNA replication is a challenge for the faithful transmission of parental information to daughter cells, as both DNA and chromatin organization must be duplicated. Replication stress further complicates the safeguard of epigenome integrity. Here, we investigate the transmission of the histone variants H3.3 and H3.1 during replication. We follow their distribution relative to replication timing, first in the genome and, second, in 3D using super-resolution microscopy. We find that H3.3 and H3.1 mark early- and late-replicating chromatin, respectively. In the nucleus, H3.3 forms domains, which decrease in density throughout replication, while H3.1 domains increase in density. Hydroxyurea impairs local recycling of parental histones at replication sites. Similarly, depleting the histone chaperone ASF1 affects recycling, leading to an impaired histone variant landscape. We discuss how faithful transmission of histone variants involves ASF1 and can be impacted by replication stress, with ensuing consequences for cell fate and tumorigenesis.

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