scholarly journals Entropic forces drive clustering and spatial localization of influenza A M2 during viral budding

2018 ◽  
Vol 115 (37) ◽  
pp. E8595-E8603 ◽  
Author(s):  
Jesper J. Madsen ◽  
John M. A. Grime ◽  
Jeremy S. Rossman ◽  
Gregory A. Voth
Keyword(s):  
Host Cell ◽  
Influenza A ◽  
Lipid Membrane ◽  
Transmembrane Protein ◽  
Membrane Curvature ◽  
Coarse Grained ◽  
Membrane Remodeling ◽  
Viral Budding ◽  
Virion Release ◽  
Liquid Ordered

The influenza A matrix 2 (M2) transmembrane protein facilitates virion release from the infected host cell. In particular, M2 plays a role in the induction of membrane curvature and/or in the scission process whereby the envelope is cut upon virion release. Here we show using coarse-grained computer simulations that various M2 assembly geometries emerge due to an entropic driving force, resulting in compact clusters or linearly extended aggregates as a direct consequence of the lateral membrane stresses. Conditions under which these protein assemblies will cause the lipid membrane to curve are explored, and we predict that a critical cluster size is required for this to happen. We go on to demonstrate that under the stress conditions taking place in the cellular membrane as it undergoes large-scale membrane remodeling, the M2 protein will, in principle, be able to both contribute to curvature induction and sense curvature to line up in manifolds where local membrane line tension is high. M2 is found to exhibit linactant behavior in liquid-disordered–liquid-ordered phase-separated lipid mixtures and to be excluded from the liquid-ordered phase, in near-quantitative agreement with experimental observations. Our findings support a role for M2 in membrane remodeling during influenza viral budding both as an inducer and a sensor of membrane curvature, and they suggest a mechanism by which localization of M2 can occur as the virion assembles and releases from the host cell, independent of how the membrane curvature is produced.

scholarly journals Entropic Forces Drive Clustering and Spatial Localization of Influenza A M2 During Viral Budding

2018 ◽  
Author(s):  
Jesper J. Madsen ◽  
John M. A. Grime ◽  
Jeremy S. Rossman ◽  
Gregory A. Voth
Keyword(s):  
Host Cell ◽  
Influenza A ◽  
Spatial Localization ◽  
Membrane Curvature ◽  
Infected Host ◽  
Membrane Remodeling ◽  
Infected Host Cell ◽  
Viral Budding ◽  
Virion Release ◽  
Liquid Ordered

ABSTRACTThe influenza A matrix 2 (M2) transmembrane protein facilitates virion release from the infected host cell. In particular, M2 plays a role in the induction of membrane curvature and/or in the scission process whereby the envelope is cut upon virion release. Here we show using coarse-grained computer simulations that various M2 assembly geometries emerge due to an entropic driving force, resulting in compact clusters or linearly extended aggregates as a direct consequence of the lateral membrane stresses. Conditions under which these protein assemblies will cause the lipid membrane to curve are explored and we predict that a critical cluster size is required for this to happen. We go on to demonstrate that under the stress conditions taking place in the cellular membrane as it undergoes large-scale membrane remodeling, the M2 protein will in principle be able to both contribute to curvature induction and sense curvature in order to line up in manifolds where local membrane line tension is high. M2 is found to exhibit linactant behavior in liquid-disordered/liquid-ordered phase-separated lipid mixtures and to be excluded from the liquid-ordered phase, in near-quantitative agreement with experimental observations. Our findings support a role for M2 in membrane remodeling during influenza viral budding both as an inducer and a sensor of membrane curvature, and they suggest a mechanism by which localization of M2 can occur as the virion assembles and releases from the host cell, independent of how the membrane curvature is produced.SIGNIFICANCE STATEMENTFor influenza virus to release from the infected host cell, controlled viral budding must finalize with membrane scission of the viral envelope. Curiously, influenza carries its own protein, M2, which can sever the membrane of the constricted budding neck. Here we elucidate the physical mechanism of clustering and spatial localization of the M2 scission proteins through a combined computational and experimental approach. Our results provide fundamental insights into how M2 clustering and localization interplays with membrane curvature, membrane lateral stresses, and lipid bilayer phase behavior during viral budding in order to contribute to virion release.

scholarly journals Bending of the BST-2 coiled-coil during viral budding

2017 ◽  
Author(s):  
Kadir A. Ozcan ◽  
Christopher E. Berndsen
Keyword(s):  
Cell Membrane ◽  
Host Cell ◽  
Transmembrane Protein ◽  
Coiled Coil ◽  
Membrane Anchor ◽  
Mouse Homolog ◽  
Host Cell Membrane ◽  
Structural Mechanism ◽  
Viral Budding ◽  
Hiv 1

AbstractBST-2/tetherin is a human extracellular transmembrane protein that serves as a host defense factor against HIV-1 and other viruses by inhibiting viral spreading. Structurally, BST-2 is a homodimeric coiled-coil that is connected to the host cell membrane by N and C terminal transmembrane anchors. The C-terminal membrane anchor of BST-2 is inserted into the budding virus while the N-terminal membrane anchor remains in the host cell membrane creating a viral tether. The structural mechanism of viral budding and tethering as mediated by BST-2 is not clear. To more fully describe the mechanism of viral tethering, we created a model of BST-2 embedded in a membrane and used steered molecular dynamics to simulate the transition from the host cell membrane associated BST-2 and the cell-virus membrane bridging form. We observed that BST-2 did not transition as a rigid structure, but instead bent at sites with a reduced interface between the helices of the coiled-coil. The simulations for the human BST-2 were then compared with simulations on the mouse homolog, which has a more stable coiled-coil. We observed that the mouse homolog spread the bending across the ectodomain, rather than breaking at discrete points as observed with the human homolog. These simulations support previous biochemical and cellular work suggesting some flexibility in the coiled-coil is necessary for viral tethering, while also highlighting how subtle changes in protein sequence can influence the dynamics and stability of proteins with overall similar structure.

scholarly journals Membrane-mediated forces can stabilize tubular assemblies of I-Bar proteins

2020 ◽  
Author(s):  
Z. Jarin ◽  
A. J. Pak ◽  
P. Bassereau ◽  
G. A. Voth
Keyword(s):  
Computational Models ◽  
Large Body ◽  
Membrane Curvature ◽  
Coarse Grained ◽  
Membrane Remodeling ◽  
Membrane Composition ◽  
Membrane Structures ◽  
Bar Domain ◽  
Cellular Environment ◽  
Bar Domains

AbstractCollective action by Inverse-BAR (I-BAR) domains drive micron-scale membrane remodeling. The macroscopic curvature sensing and generation behavior of I-BAR domains is well characterized, and computational models have suggested various mechanisms on simplified membrane systems, but there remain missing connections between the complex environment of the cell and the models proposed thus far. Here, we show a connection between the role of protein curvature and lipid clustering in the stabilization of large membrane deformations. We find lipid clustering provides a directional membrane-mediated interaction between membrane-bound I-BAR domains. Lipid clusters stabilize I-BAR domain aggregates that would not arise through membrane fluctuation-based or curvature-based interactions. Inside of membrane protrusions, lipid cluster-mediated interaction draws long side-by-side aggregates together resulting in more cylindrical protrusions as opposed to bulbous, irregularly shaped protrusions.Statement of SignificanceMembrane remodeling occurs throughout the cell and is crucial to proper cellular function. In the cellular environment, I-BAR proteins are responsible for sensing membrane curvature and initiating the formation of protrusions outward from the cell. Additionally, there is a large body of evidence that I-BAR domains are sufficient to reshape the membrane on scales much larger than any single domain. The mechanism by which I-BAR domains can remodel the membrane is uncertain. However, experiments show that membrane composition and most notably negatively-charge lipids like PIP2 play a role in the onset of tubulation. Using coarse-grained models, we show that I-BAR domains can cluster negatively charge lipids and clustered PIP2-like membrane structures facilitate a directional membrane-mediated interaction between I-BAR domains.

scholarly journals Phospholipase Cβ1 induces membrane tubulation and is involved in caveolae formation

2016 ◽  
Vol 113 (28) ◽  
pp. 7834-7839 ◽  
Author(s):  
Takehiko Inaba ◽  
Takuma Kishimoto ◽  
Motohide Murate ◽  
Takuya Tajima ◽  
Shota Sakai ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Lipid Membrane ◽  
Membrane Curvature ◽  
Membrane Remodeling ◽  
Ph Domain ◽  
Dynamic Membrane ◽  
C Terminus ◽  
Inositol Phospholipids ◽  
Membrane Tubulation ◽  
Hydrolysis Of

Lipid membrane curvature plays important roles in various physiological phenomena. Curvature-regulated dynamic membrane remodeling is achieved by the interaction between lipids and proteins. So far, several membrane sensing/sculpting proteins, such as Bin/amphiphysin/Rvs (BAR) proteins, are reported, but there remains the possibility of the existence of unidentified membrane-deforming proteins that have not been uncovered by sequence homology. To identify new lipid membrane deformation proteins, we applied liposome-based microscopic screening, using unbiased-darkfield microscopy. Using this method, we identified phospholipase Cβ1 (PLCβ1) as a new candidate. PLCβ1 is well characterized as an enzyme catalyzing the hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2). In addition to lipase activity, our results indicate that PLCβ1 possessed the ability of membrane tubulation. Lipase domains and inositol phospholipids binding the pleckstrin homology (PH) domain of PLCβ1 were not involved, but the C-terminal sequence was responsible for this tubulation activity. Computational modeling revealed that the C terminus displays the structural homology to the BAR domains, which is well known as a membrane sensing/sculpting domain. Overexpression of PLCβ1 caused plasma membrane tubulation, whereas knockdown of the protein reduced the number of caveolae and induced the evagination of caveolin-rich membrane domains. Taken together, our results suggest a new function of PLCβ1: plasma membrane remodeling, and in particular, caveolae formation.

scholarly journals Lipid membrane-mediated attraction between curvature inducing objects

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Casper van der Wel ◽  
Afshin Vahid ◽  
Anđela Šarić ◽  
Timon Idema ◽  
Doris Heinrich ◽  
...  
Keyword(s):  
Colloidal Particles ◽  
Lipid Membrane ◽  
Numerical Study ◽  
Particle Diameter ◽  
Interaction Force ◽  
Membrane Curvature ◽  
Coarse Grained ◽  
Cellular Transport ◽  
Curvature Energy ◽  
Membrane Deformations

Abstract The interplay of membrane proteins is vital for many biological processes, such as cellular transport, cell division, and signal transduction between nerve cells. Theoretical considerations have led to the idea that the membrane itself mediates protein self-organization in these processes through minimization of membrane curvature energy. Here, we present a combined experimental and numerical study in which we quantify these interactions directly for the first time. In our experimental model system we control the deformation of a lipid membrane by adhering colloidal particles. Using confocal microscopy, we establish that these membrane deformations cause an attractive interaction force leading to reversible binding. The attraction extends over 2.5 times the particle diameter and has a strength of three times the thermal energy (−3.3 kBT). Coarse-grained Monte-Carlo simulations of the system are in excellent agreement with the experimental results and prove that the measured interaction is independent of length scale. Our combined experimental and numerical results reveal membrane curvature as a common physical origin for interactions between any membrane-deforming objects, from nanometre-sized proteins to micrometre-sized particles.

scholarly journals Curvature induction and sensing of the F-BAR protein Pacsin1 on lipid membranes via molecular dynamics simulations

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Md. Iqbal Mahmood ◽  
Hiroshi Noguchi ◽  
Kei-ichi Okazaki
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Lipid Membranes ◽  
Lipid Membrane ◽  
Complex Structure ◽  
Membrane Curvature ◽  
Coarse Grained ◽  
Lateral Interaction ◽  
Bar Domain ◽  
Dynamics Simulations

Abstract F-Bin/Amphiphysin/Rvs (F-BAR) domain proteins play essential roles in biological processes that involve membrane remodelling, such as endocytosis and exocytosis. It has been shown that such proteins transform the lipid membrane into tubes. Notably, Pacsin1 from the Pacsin/Syndapin subfamily has the ability to transform the membrane into various morphologies: striated tubes, featureless wide and thin tubes, and pearling vesicles. The molecular mechanism of this interesting ability remains elusive. In this study, we performed all-atom (AA) and coarse-grained (CG) molecular dynamics simulations to investigate the curvature induction and sensing mechanisms of Pacsin1 on a membrane. From AA simulations, we show that Pacsin1 has internal structural flexibility. In CG simulations with parameters tuned from the AA simulations, spontaneous assembly of two Pacsin1 dimers through lateral interaction is observed. Based on the complex structure, we show that the regularly assembled Pacsin1 dimers bend a tensionless membrane. We also show that a single Pacsin1 dimer senses the membrane curvature, binding to a buckled membrane with a preferred curvature. These results provide molecular insights into polymorphic membrane remodelling.

scholarly journals Influenza A H1 and H3 Transmembrane Domains Interact Differently with Each Other and with Surrounding Membrane Lipids

Viruses ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 1461
Author(s):  
Szymon Kubiszewski-Jakubiak ◽  
Remigiusz Worch
Keyword(s):  
Host Cell ◽  
Influenza A ◽  
Transmembrane Domain ◽  
Membrane Lipids ◽  
Transmembrane Protein ◽  
Accessible Surface Area ◽  
Amino Acid Sequences ◽  
Viral Envelope ◽  
Phylogenetic Groups ◽  
Host Cell Membrane

Hemagglutinin (HA) is a class I viral membrane fusion protein, which is the most abundant transmembrane protein on the surface of influenza A virus (IAV) particles. HA plays a crucial role in the recognition of the host cell, fusion of the viral envelope and the host cell membrane, and is the major antigen in the immune response during the infection. Mature HA organizes in homotrimers consisting of a sequentially highly variable globular head and a relatively conserved stalk region. Every HA monomer comprises a hydrophilic ectodomain, a pre-transmembrane domain (pre-TMD), a hydrophobic transmembrane domain (TMD), and a cytoplasmic tail (CT). In recent years the effect of the pre-TMD and TMD on the structure and function of HA has drawn some attention. Using bioinformatic tools we analyzed all available full-length amino acid sequences of HA from 16 subtypes across various host species. We calculated several physico-chemical parameters of HA pre-TMDs and TMDs including accessible surface area (ASA), average hydrophobicity (Hav), and the hydrophobic moment (µH). Our data suggests that distinct differences in these parameters between the two major phylogenetic groups, represented by H1 and H3 subtypes, could have profound effects on protein–lipid interactions, trimer formation, and the overall HA ectodomain orientation and antigen exposure.

scholarly journals Alterations of membrane curvature during influenza virus budding

2014 ◽  
Vol 42 (5) ◽  
pp. 1425-1428 ◽  
Author(s):  
Agnieszka Martyna ◽  
Jeremy Rossman
Keyword(s):  
Lipid Raft ◽  
Influenza A ◽  
Matrix Protein ◽  
Membrane Curvature ◽  
Influenza Viruses ◽  
Apical Plasma Membrane ◽  
Lipid Phase ◽  
Influenza A Viruses ◽  
Enveloped Virus ◽  
Virion Release

Influenza A virus belongs to the Orthomyxoviridae family. It is an enveloped virus that contains a segmented and negative-sense RNA genome. Influenza A viruses cause annual epidemics and occasional major pandemics, are a major cause of morbidity and mortality worldwide, and have a significant financial impact on society. Assembly and budding of new viral particles are a complex and multi-step process involving several host and viral factors. Influenza viruses use lipid raft domains in the apical plasma membrane of polarized epithelial cells as sites of budding. Two viral glycoproteins, haemagglutinin and neuraminidase, concentrate in lipid rafts, causing alterations in membrane curvature and initiation of the budding process. Matrix protein 1 (M1), which forms the inner structure of the virion, is then recruited to the site followed by incorporation of the viral ribonucleoproteins and matrix protein 2 (M2). M1 can alter membrane curvature and progress budding, whereas lipid raft-associated M2 stabilizes the site of budding, allowing for proper assembly of the virion. In the later stages of budding, M2 is localized to the neck of the budding virion at the lipid phase boundary, where it causes negative membrane curvature, leading to scission and virion release.

scholarly journals Influenza A matrix protein M1 induces lipid membrane deformation via protein multimerization

2019 ◽  
Vol 39 (8) ◽  
Author(s):  
Ismail Dahmani ◽  
Kai Ludwig ◽  
Salvatore Chiantia
Keyword(s):  
Influenza A ◽  
Matrix Protein ◽  
Lipid Membrane ◽  
Membrane Curvature ◽  
Correlation Spectroscopy ◽  
Dimensional Structure ◽  
Membrane Deformation ◽  
Induced Membrane ◽  
Cellular Models ◽  
Matrix Protein M1

Abstract The matrix protein M1 of the Influenza A virus (IAV) is supposed to mediate viral assembly and budding at the plasma membrane (PM) of infected cells. In order for a new viral particle to form, the PM lipid bilayer has to bend into a vesicle toward the extracellular side. Studies in cellular models have proposed that different viral proteins might be responsible for inducing membrane curvature in this context (including M1), but a clear consensus has not been reached. In the present study, we use a combination of fluorescence microscopy, cryogenic transmission electron microscopy (cryo-TEM), cryo-electron tomography (cryo-ET) and scanning fluorescence correlation spectroscopy (sFCS) to investigate M1-induced membrane deformation in biophysical models of the PM. Our results indicate that M1 is indeed able to cause membrane curvature in lipid bilayers containing negatively charged lipids, in the absence of other viral components. Furthermore, we prove that protein binding is not sufficient to induce membrane restructuring. Rather, it appears that stable M1–M1 interactions and multimer formation are required in order to alter the bilayer three-dimensional structure, through the formation of a protein scaffold. Finally, our results suggest that, in a physiological context, M1-induced membrane deformation might be modulated by the initial bilayer curvature and the lateral organization of membrane components (i.e. the presence of lipid domains).

scholarly journals Influenza A matrix protein M1 is sufficient to induce lipid membrane deformation

2019 ◽  
Author(s):  
Ismail Dahmani ◽  
Kai Ludwig ◽  
Salvatore Chiantia
Keyword(s):  
Influenza A ◽  
Matrix Protein ◽  
Lipid Membrane ◽  
Membrane Curvature ◽  
Correlation Spectroscopy ◽  
Dimensional Structure ◽  
Membrane Deformation ◽  
Induced Membrane ◽  
Cellular Models ◽  
Matrix Protein M1

AbstractThe matrix protein M1 of the Influenza A virus is considered to mediate viral assembly and budding at the plasma membrane (PM) of infected cells. In order for a new viral particle to form, the PM lipid bilayer has to bend into a vesicle towards the extracellular side. Studies in cellular models have proposed that different viral proteins might be responsible for inducing membrane curvature in this context (including M1), but a clear consensus has not been reached. In this study, we use a combination of fluorescence microscopy, cryogenic transmission electron microscopy (cryo-TEM), cryo-electron tomography (cryo-ET) and scanning fluorescence correlation spectroscopy (sFCS) to investigate M1-induced membrane deformation in biophysical models of the PM. Our results indicate that M1 is indeed capable to cause membrane curvature in lipid bilayers containing negatively-charged lipids, in the absence of other viral components. Furthermore, we prove that simple protein binding is not sufficient to induce membrane restructuring. Rather, it appears that stable M1-M1 interactions and multimer formation are required in order to alter the bilayer three-dimensional structure, through the formation of a protein scaffold. Finally, our results suggest that, in a physiological context, M1-induced membrane deformation might be modulated by the initial bilayer curvature and the lateral organization of membrane components (i.e. the presence of lipid domains).

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