Membranes et fonctions cellulaires

Publications

Année de publication : 2021

Tsai Feng-Ching, Simunovic Mijo, Sorre Benoit , Bertin Aurélie, Manzi John, Callan-Jones Andrew, Bassereau Patricia (2021 Apr 6)

Comparing physical mechanisms for membrane curvature-driven sorting of BAR-domain proteins

Soft Matter : DOI : 10.1039/D0SM01573C En savoir plus
Résumé

Protein enrichment at specific membrane locations in cells is crucial for many cellular functions. It is well-recognized that the ability of some proteins to sense membrane curvature contributes partly to their enrichment in highly curved cellular membranes. In the past, different theoretical models have been developed to reveal the physical mechanisms underlying curvature-driven protein sorting. This review aims to provide a detailed discussion of the two continuous models that are based on the Helfrich elasticity energy, (1) the spontaneous curvature model and (2) the curvature mismatch model. These two models are commonly applied to describe experimental observations of protein sorting. We discuss how they can be used to explain the curvature-induced sorting data of two BAR proteins, amphiphysin and centaurin. We further discuss how membrane rigidity, and consequently the membrane curvature generated by BAR proteins, could influence protein organization on the curved membranes. Finally, we address future directions in extending these models to describe some cellular phenomena involving protein sorting.

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Année de publication : 2019

Julien Pernier, Remy Kusters, Hugo Bousquet, Thibaut Lagny, Antoine Morchain, Jean-François Joanny*, Patricia Bassereau*, Evelyne Coudrier* (2019 Nov 15)

Myosin 1b is an actin depolymerase.

Nature Communications : 10 : 5200 : DOI : 10.1038/s41467-019-13160-y En savoir plus
Résumé

The regulation of actin dynamics is essential for various cellular processes. Former evidence suggests a correlation between the function of non-conventional myosin motors and actin dynamics. Here we investigate the contribution of myosin 1b to actin dynamics using sliding motility assays. We observe that sliding on myosin 1b immobilized or bound to a fluid bilayer enhances actin depolymerization at the barbed end, while sliding on myosin II, although 5 times faster, has no effect. This work reveals a non-conventional myosin motor as another type of depolymerase and points to its singular interactions with the actin barbed end.

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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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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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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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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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Année de publication : 2017

Win Pin Ng, Kevin D. Webster, Caroline Stefani, Eva M. Schmid, Emmanuel Lemichez, Patricia Bassereau, Daniel A. Fletcher (2017 Oct 2)

Force-induced transcellular tunnel formation in endothelial cells

Molecular Biology of the Cell : 28 : 2650-2660 : DOI : 10.1091/mbc.E17-01-0080 En savoir plus
Résumé

The endothelium serves as a protective semipermeable barrier in blood vessels and lymphatic vessels. Leukocytes and pathogens can pass directly through the endothelium by opening holes in endothelial cells, known as transcellular tunnels, which are formed by contact and self-fusion of the apical and basal plasma membranes. Here we test the hypothesis that the actin cytoskeleton is the primary barrier to transcellular tunnel formation using a combination of atomic force microscopy and fluorescence microscopy of live cells. We find that localized mechanical forces are sufficient to induce the formation of transcellular tunnels in human umbilical vein endothelial cells (HUVECs). When HUVECs are exposed to the bacterial toxin called epidermal cell differentiation inhibitor (EDIN), which can induce spontaneous transcellular tunnels, less mechanical work is required to form tunnels due to the reduced cytoskeletal stiffness and thickness of these cells, similarly to the effects of a Rho-associated protein kinase (ROCK) inhibitor. We also observe actin enrichment in response to mechanical indentation that is reduced in cells exposed to the bacterial toxin. Our study shows that the actin cytoskeleton of endothelial cells provides both passive and active resistance against transcellular tunnel formation, serving as a mechanical barrier that can be overcome by mechanical force as well as disruption of the cytoskeleton.

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Caroline Stefani, David Gonzalez-Rodriguez, Yosuke Senju, Anne Doye, Nadia Efimova, Sébastien Janel, Justine Lipuma, Meng Chen Tsai, Daniel Hamaoui, Madhavi P. Maddugoda, Olivier Cochet-Escartin, Coline Prévost, Frank Lafont, Tatyana Svitkina, Pekka Lappalainen, Patricia Bassereau, Emmanuel Lemichez (2017 Jun 23)

Ezrin enhances line tension along transcellular tunnel edges via NMIIa driven actomyosin cable formation.

Nature Communications : 8 : 15839 : DOI : 10.1038/ncomms15839 En savoir plus
Résumé

Transendothelial cell macroaperture (TEM) tunnels control endothelium barrier function and are triggered by several toxins from pathogenic bacteria that provoke vascular leakage. Cellular dewetting theory predicted that a line tension of uncharacterized origin works at TEM boundaries to limit their widening. Here, by conducting high-resolution microscopy approaches we unveil the presence of an actomyosin cable encircling TEMs. We develop a theoretical cellular dewetting framework to interpret TEM physical parameters that are quantitatively determined by laser ablation experiments. This establishes the critical role of ezrin and non-muscle myosin II (NMII) in the progressive implementation of line tension. Mechanistically, fluorescence-recovery-after-photobleaching experiments point for the upstream role of ezrin in stabilizing actin filaments at the edges of TEMs, thereby favouring their crosslinking by NMIIa. Collectively, our findings ascribe to ezrin and NMIIa a critical function of enhancing line tension at the cell boundary surrounding the TEMs by promoting the formation of an actomyosin ring.

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David Saletti, Jens Radzimanowski, Gregory Effantin, Daniel Midtvedt, Stéphanie Mangenot, Winfried Weissenhorn, Patricia Bassereau, Marta Bally (2017 Jan 26)

The Matrix protein M1 from influenza C virus induces tubular membrane invaginations in an in vitro cell membrane model.

Scientific reports : 40801 : DOI : 10.1038/srep40801 En savoir plus
Résumé

Matrix proteins from enveloped viruses play an important role in budding and stabilizing virus particles. In order to assess the role of the matrix protein M1 from influenza C virus (M1-C) in plasma membrane deformation, we have combined structural and in vitro reconstitution experiments with model membranes. We present the crystal structure of the N-terminal domain of M1-C and show by Small Angle X-Ray Scattering analysis that full-length M1-C folds into an elongated structure that associates laterally into ring-like or filamentous polymers. Using negatively charged giant unilamellar vesicles (GUVs), we demonstrate that M1-C full-length binds to and induces inward budding of membrane tubules with diameters that resemble the diameter of viruses. Membrane tubule formation requires the C-terminal domain of M1-C, corroborating its essential role for M1-C polymerization. Our results indicate that M1-C assembly on membranes constitutes the driving force for budding and suggest that M1-C plays a key role in facilitating viral egress.

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Garten M., Mosgaard L.D., Bornschlögl T., Dieudonné S., Bassereau P., Toombes G.E.S. (2017 Jan 1)

Whole-GUV patch-clamping

Proceedings of the National Academy of Sciences : 114 : 328-333 : DOI : 10.1073/pnas.1609142114 En savoir plus
Résumé

Studying how the membrane modulates ion channel and transporter activity is challenging because cells actively regulate membrane properties, whereas existing in vitro systems have limitations, such as residual solvent and unphysiologically high membrane tension. Cell-sized giant unilamellar vesicles (GUVs) would be ideal for in vitro electrophysiology, but efforts to measure the membrane current of intact GUVs have been unsuccessful. In this work, two challenges for obtaining the “whole-GUV” patch-clamp configuration were identified and resolved. First, unless the patch pipette and GUV pressures are precisely matched in the GUV-attached configuration, breaking the patch membrane also ruptures the GUV. Second, GUVs shrink irreversibly because the membrane/glass adhesion creating the high-resistance seal (>1 GΩ) continuously pulls membrane into the pipette. In contrast, for cell-derived giant plasma membrane vesicles (GPMVs), breaking the patch membrane allows the GPMV contents to passivate the pipette surface, thereby dynamically blocking membrane spreading in the whole-GMPV mode. To mimic this dynamic passivation mechanism, beta-casein was encapsulated into GUVs, yielding a stable, high-resistance, whole-GUV configuration for a range of membrane compositions. Specific membrane capacitance measurements confirmed that the membranes were truly solvent-free and that membrane tension could be controlled over a physiological range. Finally, the potential for ion transport studies was tested using the model ion channel, gramicidin, and voltage-clamp fluorometry measurements were performed with a voltage-dependent fluorophore/quencher pair. Whole-GUV patch-clamping allows ion transport and other voltage-dependent processes to be studied while controlling membrane composition, tension, and shape.

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Année de publication : 2016

Mijo Simunovic, Coline Prévost, Andrew Callan-Jones, Patricia Bassereau (2016 Jun 15)

Physical basis of some membrane shaping mechanisms.

Philosophical transactions. Series A, Mathematical, physical, and engineering sciences : DOI : 10.1098/rsta.2016.0034 En savoir plus
Résumé

In vesicular transportation pathways, membrane lipids and proteins are internalized, externalized or transported Within cells, not by bulk diffusion of single molecules, goal embedded in the membrane of small vesicles or thin tubules. The formation of These ‘transportation carriers’ Follows sequential events: bending membrane fission from the donor compartment, and transportation Eventually fusion with the acceptor membrane. A similar sequence is Involved During the internalization of drug or gene carriers inside cells. These membrane-shaping events are mediated by proteins Generally binding to membranes. The thesis Mechanisms behind biological processes are Actively Studied Both in the context of cell biology and biophysics. Bin / Amphiphysin / Rvs (BAR) domain proteins are Ideally suited for single Illustrating how soft matter principles can account for deformation by membrane proteins. We review here Some experimental methods and theoretical models to measure Corresponding thesis how proteins affect the mechanics and the shape of membranes. In more detail, we show how an experimental method Employing optical tweezers to pull a tube from a giant vesicle May give significant quantitative insights into the mechanism by which proteins sense and generate membrane curvature and the mechanism of membrane scission.This article is share of the themed issue ‘Soft interfacial materials: from fundamentals to formulation’.

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Alice Berthaud, François Quemeneur, Maxime Deforet, Patricia Bassereau, Françoise Brochard-Wyart, Stéphanie Mangenot (2015 Dec 15)

Spreading of porous vesicles subjected to osmotic shocks: the role of aquaporins.

Soft matter : 12 : 1601-1609 : DOI : 10.1039/c5sm01654a En savoir plus
Résumé

Aquaporin 0 (AQP0) is a transmembrane protein specific to the eye lens, Involved as a water carrier across the lipid membranes. During maturation eye lens, AQP0s are truncated by proteolytic cleavage. We Investigate this work in the capability of truncated AQP0 to conduite water across membranes. We Developed a method to Accurately determine water permeability across lipid membranes and proteins across from the deflation under osmotic pressure of giant unilamellar vesicles (GUVs) Deposited adhesive substrate on year. Using reflection interference contrast microscopy (RICM), we measure the spreading area of ​​GUVs During deswelling. We interpret thesis results using a model based on hydrodynamic, binder diffusion Reviews towards the touch area, and Helfrich’s law for the membrane voltage, qui allows us to spread recounts the area to the internal vesicle volume. We first study the specific adhesion of vesicles coated with biotin was spreading streptavidin substrate. Then we determine the permeability of a single functional AQP0 and Demonstrate That truncated AQP0 is no more a water channel.

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Année de publication : 2015

Mijo Simunovic, Gregory A Voth, Andrew Callan-Jones, Patricia Bassereau (2015 Nov 2)

When Physics Takes Over: BAR Proteins and Membrane Curvature.

Trends in cell biology : 780-92 : DOI : 10.1016/j.tcb.2015.09.005 En savoir plus
Résumé

Cell membranes Become highly curved During membrane trafficking, cytokinesis, infection, immune response, or cell motion. Bin / Amphiphysin / Rvs (BAR) domain proteins Intrinsically With Their curved shape anisotropy and are Involved in Many of These processes, aim with a wide spectrum of modes of action. In vitro experiments and computer simulations multiscale-have Contributed in Identifying a minimal set of physical parameters derived derived, namely protein density on the membrane, membrane voltage and membrane shape, That control how bound BAR domain proteins behave on the membrane. In this review, we summarize the multifaceted BAR coupling of proteins to membrane mechanics and offers a single-phase diagram That Recapitulates the effects of These parameters.

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Thibaut J Lagny, Patricia Bassereau (2015 Oct 15)

Bioinspired membrane-based systems for a physical approach of cell organization and dynamics: usefulness and limitations.

Interface focus : 20150038 : DOI : 10.1098/rsfs.2015.0038 En savoir plus
Résumé

Being at the Periphery of Each cell compartment and enclosing the Entire cell while interacting with a large part of cell components, cell membranes Participate in MOST of the cell’s vital functions. Biologists-have for a long time Worked on deciphering how membranes are Organized, How They contribuer to trafficking, motility, cytokinesis, cell-cell communication, transport information, etc., using top-down Approaches and always more advanced techniques. In contrast, physicists-have Developed bottom-up Approaches and minimal model membrane systems of growing complexity in order to build up general models That explain how cell membranes work and How They interact with proteins, eg the cytoskeleton. We review the different model membrane systems That ares currently available, and How They can help deciphering cell functioning, goal aussi Their list limitations. Model membrane systems are aussi used in synthetic biology and can-have potential applications beyond basic research. We can the Chat the synergy entre le development of complex membrane systems in vitro in a biological context and for technological applications. Questions That Could aussi be Discussed are: what can we still do with synthetic systems, where do we stop building up and qui are the alternative solutions?

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