Relaxation of Loaded ESCRT-III Spiral Springs Drives Membrane Deformation

International audienceESCRT-III is required for lipid membrane remodeling in many cellular processes, from abscission to viral budding and multi-vesicular body biogenesis. However, how ESCRT-III polymerization generates membrane curvature remains debated. Here, we show that Snf7, the main component of ESCRT-III, polymerizes into spirals at the surface of lipid bilayers. When covering the entire membrane surface, these spirals stopped growing when densely packed: they had a polygonal shape, suggesting that lateral compression could deform them. We reasoned that Snf7 spirals could function as spiral springs. By measuring the polymerization energy and the rigidity of Snf7 filaments, we showed that they were deformed while growing in a confined area. Furthermore, we observed that the elastic expansion of compressed Snf7 spirals generated an area difference between the two sides of the membrane and thus curvature. This spring-like activity underlies the driving force by which ESCRT-III could mediate membrane deformation and fission

Understanding the effects of omega-3 fatty acid supplementation on the physical properties of brain lipid membranes

Impact Factor: 0.8Fil: Longarzo, María L. Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata, Argentina.Fil: Vázquez, Romina F. Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata, Argentina.Fil: Bellini, María J. Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata, Argentina.Fil: Zamora, Ricardo A. The Barcelona Institute of Science and Technology. Institute for Bioengineering of Catalonia, Spain.Fil: Zamora, Ricardo A. Universidad de Talca. Vicerrectoría Académica. Instituto de Investigación Interdisciplinaria, Chile.Fil: Zamora, Ricardo A. Universidad de Talca. Facultad de Ingeniería. Centro de Bioinformática, Simulación y Modelado, Chile.Fil: Redondo-Morata, Lorena. Universite´ de Lille. Institut Pasteur de Lille. Center for Infection and Immunity of Lille, France.Fil: Giannotti, Marina I. The Barcelona Institute of Science and Technology. Institute for Bioengineering of Catalonia, Spain.Fil: Giannotti, Marina I. Centro de Investigación Biomédica en Red en el área temática de Bioingeniería, Biomateriales y Nanomedicina, Spain.Fil: Giannotti, Marina I. University of Barcelona. Department of Materials Science and Physical Chemistry, Spain.Fil: Oliveira, Osvaldo N. Jr. Universidad de São Paulo. São Carlos Institute of Physics, Brazil.Fil: Fanani, María L. Universidad Nacional de Córdoba, Facultad de Ciencias Químicas Departamento de Química Biológica Raquel Caputto, Argentina.Fil: Fanani, María L. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Química Biológica de Córdoba, Argentina.Fil: Mate, Sabina M. Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata, Argentina.A deficiency in omega-3 fatty acids (ω3 FAs) in the brain has been correlated with cognitive impairment, learning deficiencies, and behavioral changes. In this study, we provided ω3 FAs as a supplement to spontaneously hypertensive rats (SHR+ ω3). Our focus was on examining the impact of dietary supplementation on the physicochemical properties of the brain-cell membranes. Significant increases in ω3 levels in the cerebral cortex of SHR+ ω3 were observed, leading to alterations in brain lipid membranes molecular packing, elasticity, and lipid miscibility, resulting in an augmented phase disparity. Results from synthetic lipid mixtures confirmed the disordering effect introduced by ω3 lipids, showing its consequences on the hydration levels of the monolayers and the organization of the membrane domains. These findings suggest that dietary ω3 FAs influence the organization of brain membranes, providing insight into a potential mechanism for the broad effects of dietary fat on brain health and disease.info:eu-repo/semantics/publishedVersionFil: Longarzo, María L. Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata, Argentina.Fil: Vázquez, Romina F. Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata, Argentina.Fil: Bellini, María J. Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata, Argentina.Fil: Zamora, Ricardo A. The Barcelona Institute of Science and Technology. Institute for Bioengineering of Catalonia, Spain.Fil: Zamora, Ricardo A. Universidad de Talca. Vicerrectoría Académica. Instituto de Investigación Interdisciplinaria, Chile.Fil: Zamora, Ricardo A. Universidad de Talca. Facultad de Ingeniería. Centro de Bioinformática, Simulación y Modelado, Chile.Fil: Redondo-Morata, Lorena. Universite´ de Lille. Institut Pasteur de Lille. Center for Infection and Immunity of Lille, France.Fil: Giannotti, Marina I. The Barcelona Institute of Science and Technology. Institute for Bioengineering of Catalonia, Spain.Fil: Giannotti, Marina I. Centro de Investigación Biomédica en Red en el área temática de Bioingeniería, Biomateriales y Nanomedicina, Spain.Fil: Giannotti, Marina I. University of Barcelona. Department of Materials Science and Physical Chemistry, Spain.Fil: Oliveira, Osvaldo N. Jr. Universidad de São Paulo. São Carlos Institute of Physics, Brazil.Fil: Fanani, María L. Universidad Nacional de Córdoba, Facultad de Ciencias Químicas Departamento de Química Biológica Raquel Caputto, Argentina.Fil: Fanani, María L. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Química Biológica de Córdoba, Argentina.Fil: Mate, Sabina M. Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata, Argentina

Molecular recognition of a membrane-anchored HIV-1 pan-neutralizing epitope.

Antibodies against the carboxy-terminal section of the membrane-proximal external region (C-MPER) of the HIV-1 envelope glycoprotein (Env) are considered as nearly pan-neutralizing. Development of vaccines capable of producing analogous broadly neutralizing antibodies requires deep understanding of the mechanism that underlies C-MPER recognition in membranes. Here, we use the archetypic 10E8 antibody and a variety of biophysical techniques including single-molecule approaches to study the molecular recognition of C-MPER in membrane mimetics. In contrast to the assumption that an interfacial MPER helix embodies the entire C-MPER epitope recognized by 10E8, our data indicate that transmembrane domain (TMD) residues contribute to binding affinity and specificity. Moreover, anchoring to membrane the helical C-MPER epitope through the TMD augments antibody binding affinity and relieves the effects exerted by the interfacial MPER helix on the mechanical stability of the lipid bilayer. These observations support that addition of TMD residues may result in more efficient and stable anti-MPER vaccines.This study was supported by MCIN/AEI/10.13039/501100011033 - “ERDF A way of making Europe” (Grant PID2021-126014OB-I00 to J.L.N. and B.A.), MCIN/AEI/10.13039/501100011033 (Grant PID2020-112821GB-I00 to M.A.J.), Basque Government (Grant: IT1449-22 to J.L.N. and B.A.) and Kiban-B grant 20H03228 from JSPS to J.M.M.C. L.R.-M. acknowledges funding from the Agence National de la Recherche (ANR), as part of the ‘Investments d′Avenir’ Program (I-SITE ULNE/ANR-16-IDEX-0004 ULNE). This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 895819 (to C.V.). Work at Pompeu Fabra University was supported by the María de Maeztu network of Units of Excellence of the Spanish Ministry of Science and Innovation. Technical assistance from Miguel García-Porras is greatly acknowledged. The NMR experiments were performed in the “Manuel Rico” NMR laboratory, LMR, CSIC, a node of the Spanish Large-Scale National Facility ICTS R-LRB

Molecular, dynamic, and structural origin of inhomogeneous magnetization transfer in lipid membranes

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136337/1/mrm26210.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136337/2/mrm26210_am.pd

Ions modulate stress-induced nano-texture in supported fluid lipid bilayers.

Most plasma membranes comprise a large number of different molecules including lipids and proteins. In the standard fluid mosaic model, the membrane function is effected by proteins whereas lipids are largely passive and serve solely in the membrane cohesion. Here we show, using supported 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayers in different saline solutions, that ions can locally induce ordering of the lipid molecules within the otherwise fluid bilayer when the latter is supported. This nanoordering exhibits a characteristic length scale of ∼20 nm, and manifests itself clearly when mechanical stress is applied to the membrane. Atomic force microscopy (AFM) measurements in aqueous solutions containing NaCl, KCl, CaCl2, and Tris buffer show that the magnitude of the effect is strongly ion-specific, with Ca2+ and Tris, respectively, promoting and reducing stress-induced nanotexturing of the membrane. The AFM results are complemented by fluorescence recovery after photobleaching experiments, which reveal an inverse correlation between the tendency for molecular nanoordering and the diffusion coefficient within the bilayer. Control AFM experiments on other lipids and at different temperatures support the hypothesis that the nanotexturing is induced by reversible, localized gel-like solidification of the membrane. These results suggest that supported fluid phospholipid bilayers are not homogenous at the nanoscale, but specific ions are able to locally alter molecular organization and mobility, and spatially modulate the membrane’s properties on a length scale of ∼20 nm. To illustrate this point, AFM was used to follow the adsorption of the membrane-penetrating antimicrobial peptide Temporin L in different solutions. The results confirm that the peptides do not absorb randomly, but follow the ion-induced spatial modulation of the membrane. Our results suggest that ionic effects have a significant impact for passively modulating the local properties of biological membranes, when in contact with a support such as the cytoskeleton

Biological physics by high-speed atomic force microscopy

International audienceWhile many fields have contributed to biological physics, nanotechnology offered a new scale of observation. High-speed atomic force microscopy (HS-AFM) provides nanometre structural information and dynamics with subsecond resolution of biological systems. Moreover, HS-AFM allows us to measure piconewton forces within microseconds giving access to unexplored, fast biophysical processes. Thus, HS-AFM provides a tool to nourish biological physics through the observation of emergent physical phenomena in biological systems. In this review, we present an overview of the contribution of HS-AFM, both in imaging and force spectroscopy modes, to the field of biological physics. We focus on examples in which HS AFM observations on membrane remodelling, molecular motors or the unfolding of proteins have stimulated the development of novel theories or the emergence of new concepts. We finally provide expected applications and developments of HS-AFM that we believe will continue contributing toour understanding of nature, by serving to the dialog between biology and physics. This article is part of the discussion meeting issue ‘Dynamic in situ microscopy relating structure and function’

High resolution and High-Speed Atomic Force Microscope imaging

International audienceThe advent of high-speed atomic force microscopy (HS-AFM) in recent years has opened up new horizons for the study of structure, function and dynamics of biological molecules. HS-AFM is capable of 1000 times faster imaging than conventional AFM. This circumstance uniquely enables the observation of the dynamics of all the molecules present in the imaging area. In the last ten years, the HS-AFM has gone from a prototype-state technology that only a few labs in the world had access to (including ours) to an established commercialized technology that is present in tens of labs around the world. In this protocol chapter we share with the readers our practical know-how on high resolution HS-AFM imaging

Recovery of ESCRT-III Filaments Subjected to Force: An ‘Invasive Mode’ HS-AFM Study

Endosomal sorting complex required for transport III (ESCRT-III) proteins are crucial to membrane sculpting processes, including cytokinesis and biogenesis of multivesicular bodies. How ESCRT-III polymerization generates membrane curvature remains debated. Using High-Speed Atomic Force Microscopy (HS-AFM), a versatile technique with unprecedented spatial and temporal resolution, we acquired insights into how Snf7 assemblies, the major component of the ESCRT-III system, changed architecture in the presence of divalent cations and how they recover after being dissected by applying increased forces to well-defined delimited areas of the sample surface. The dissected assemblies present free ends of broken filaments onto which new monomers from the imaging solution can polymerize. After initial perturbation, the recovering assemblies show a tendency toward maximization of interfilament contacts, manifesting as nascent filaments or elongation of broken filaments along pre-existing filaments that act as scaffolds, as well as reparation of broken filaments. Based on these results, we hypothesize about a novel mechanism by which lateral interactions between ESCRT-III filaments drive constriction of the assemblies in order to induce membrane deformation