1
|
Lafarge E, Marques CM, Schmutz M, Muller P, Schroder AP. Thickness determination of hydroperoxidized lipid bilayers from medium-resolution cryo-TEM images. Methods Enzymol 2024; 700:329-348. [PMID: 38971605 DOI: 10.1016/bs.mie.2024.02.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2024]
Abstract
As the primary products of lipid oxidation, lipid hydroperoxides constitute an important class of lipids generated by aerobic metabolism. However, despite several years of effort, the structure of the hydroperoxidized bilayer has not yet been observed under electron microscopy. Here we use a 200 kV Cryo-TEM to image small unilamellar vesicles (SUVs) made (i) of pure POPC or SOPC, (ii) of their pure hydroperoxidized form, and (iii) of their equimolar mixtures. We show that the challenges posed by the determination of the thickness of the hydroperoxidized bilayers under these observation conditions can be addressed by an image analysis method that we developed and describe here.
Collapse
Affiliation(s)
- Eulalie Lafarge
- Institut Charles Sadron, CNRS UPR22-University of Strasbourg, Strasbourg, France
| | | | - Marc Schmutz
- Institut Charles Sadron, CNRS UPR22-University of Strasbourg, Strasbourg, France
| | - Pierre Muller
- Institut Charles Sadron, CNRS UPR22-University of Strasbourg, Strasbourg, France
| | | |
Collapse
|
2
|
Souce M, Tfayli A, Rosilio V, Nicolis I, Kasselouri A. Photosensitizers incorporation in SOPC films at different hydration levels. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184077. [PMID: 36302493 DOI: 10.1016/j.bbamem.2022.184077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 09/29/2022] [Accepted: 10/18/2022] [Indexed: 11/06/2022]
Abstract
In the present work, two photosensitizing drugs, Temoporfin and Verteporfin have been studied. Both have regular approval in Europe, Temoporfin for the treatment of head and neck cancers and Verteporfin for the treatment of age-related macular degeneration (AMD). The treatment modality, known as "Photodynamic Therapy" (PDT), involves drug activation with visible light in the presence of oxygen and production of reactive oxygen species (ROS) to destroy the pathological tissues. Both drugs are inactive in the absence of light, presenting only few side effects. The incorporation of the two drugs into a SOPC bilayer -used as a model membrane- was studied by ATR-FTIR. An original approach was applied, involving lyotropic transitions and a very slow dehydration rate of the sample. In low water content and dry film, Temoporfin highly affects stretching vibrations of SOPC chains and polar groups, showing that Temoporfin is inserted into the bilayer in both apolar and polar regions. In fully hydrated layers, Temoporfin - SOPC interactions still take place but only impact Temoporfin vibration bands. Verteporfin shows smaller effect on both chain and polar groups' vibrations of SOPC, with the exception of choline group, suggesting that Verteporfin is inserted into the bilayer to a lesser extent and remains at the bilayer polar interface. These results can be used to better understand drugs behavior in biological media.
Collapse
Affiliation(s)
- Martin Souce
- Lip(Sys)(2), Chimie Analytique Pharmaceutique, Université Paris-Saclay, F-92290 Châtenay-Malabry cedex, France
| | - Ali Tfayli
- Lip(Sys)(2), Chimie Analytique Pharmaceutique, Université Paris-Saclay, F-92290 Châtenay-Malabry cedex, France
| | - Véronique Rosilio
- Institut Galien Paris Sud, CNRS, Université Paris-Saclay, F-92290 Châtenay-Malabry cedex, France
| | - Ioannis Nicolis
- UR 7537 - BioSTM « Biostatistique, Traitement et Modélisation des données biologiques » Université Paris Cité, F-75270 Paris cedex 06, France
| | - Athena Kasselouri
- Lip(Sys)(2), Chimie Analytique Pharmaceutique, Université Paris-Saclay, F-92290 Châtenay-Malabry cedex, France.
| |
Collapse
|
3
|
Heller WT. Small-Angle Neutron Scattering for Studying Lipid Bilayer Membranes. Biomolecules 2022; 12:1591. [PMID: 36358941 PMCID: PMC9687511 DOI: 10.3390/biom12111591] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 10/18/2022] [Accepted: 10/26/2022] [Indexed: 09/23/2023] Open
Abstract
Small-angle neutron scattering (SANS) is a powerful tool for studying biological membranes and model lipid bilayer membranes. The length scales probed by SANS, being from 1 nm to over 100 nm, are well-matched to the relevant length scales of the bilayer, particularly when it is in the form of a vesicle. However, it is the ability of SANS to differentiate between isotopes of hydrogen as well as the availability of deuterium labeled lipids that truly enable SANS to reveal details of membranes that are not accessible with the use of other techniques, such as small-angle X-ray scattering. In this work, an overview of the use of SANS for studying unilamellar lipid bilayer vesicles is presented. The technique is briefly presented, and the power of selective deuteration and contrast variation methods is discussed. Approaches to modeling SANS data from unilamellar lipid bilayer vesicles are presented. Finally, recent examples are discussed. While the emphasis is on studies of unilamellar vesicles, examples of the use of SANS to study intact cells are also presented.
Collapse
Affiliation(s)
- William T Heller
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| |
Collapse
|
4
|
Global Increases in Human Immunodeficiency Virus Neutralization Sensitivity Due to Alterations in the Membrane-Proximal External Region of the Envelope Glycoprotein Can Be Minimized by Distant State 1-Stabilizing Changes. J Virol 2022; 96:e0187821. [PMID: 35289647 DOI: 10.1128/jvi.01878-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Binding to the receptor, CD4, drives the pretriggered, "closed" (State-1) conformation of the human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimer ([gp120/gp41]3) into more "open" conformations. HIV-1 Env on the viral membrane is maintained in a State-1 conformation that resists binding and neutralization by commonly elicited antibodies. Premature triggering of Env before the virus engages a target cell typically leads to increased susceptibility to spontaneous inactivation or ligand-induced neutralization. Here, we showed that single amino acid substitutions in the gp41 membrane-proximal external region (MPER) of a primary HIV-1 strain resulted in viral phenotypes indicative of premature triggering of Env to downstream conformations. Specifically, the MPER changes reduced viral infectivity and globally increased virus sensitivity to poorly neutralizing antibodies, soluble CD4, a CD4-mimetic compound, and exposure to cold. In contrast, the MPER mutants exhibited decreased sensitivity to the State 1-preferring inhibitor, BMS-806, and to the PGT151 broadly neutralizing antibody. Depletion of cholesterol from virus particles did not produce the same State 1-destabilizing phenotypes as MPER alterations. Notably, State 1-stabilizing changes in Env distant from the MPER could minimize the phenotypic effects of MPER alteration but did not affect virus sensitivity to cholesterol depletion. Thus, membrane-proximal gp41 elements contribute to the maintenance of the pretriggered Env conformation. The conformationally disruptive effects of MPER changes can be minimized by distant State 1-stabilizing Env modifications, a strategy that may be useful in preserving the native pretriggered state of Env. IMPORTANCE The pretriggered shape of the human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) is a major target for antibodies that can neutralize many strains of the virus. An effective HIV-1 vaccine may need to raise these types of antibodies, but this goal has proven difficult. One reason is that the pretriggered shape of Env is unstable and dependent on interactions near the viral membrane. Here, we showed that the membrane-proximal external region (MPER) of Env plays an important role in maintaining Env in a pretriggered shape. Alterations in the MPER resulted in global changes in Env conformation that disrupted its pretriggered shape. We also found that these disruptive effects of MPER changes could be minimized by distant Env modifications that stabilized the pretriggered shape. These modifications may be useful for preserving the native shape of Env for structural and vaccine studies.
Collapse
|
5
|
Tang Y, Hu L, Liu Y, Zhou B, Qin X, Ye J, Shen M, Wu Z, Zhang P. Possible mechanisms of cholesterol elevation aggravating COVID-19. Int J Med Sci 2021; 18:3533-3543. [PMID: 34522180 PMCID: PMC8436106 DOI: 10.7150/ijms.62021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Accepted: 08/04/2021] [Indexed: 12/23/2022] Open
Abstract
Importance: Despite the availability of a vaccine against the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), humans will have to live with this virus and the after-effects of the coronavirus disease 2019 (COVID-19) infection for a long time. Cholesterol plays an important role in the infection and prognosis of SARS-CoV-2, and the study of its mechanism is of great significance not only for the treatment of COVID-19 but also for research on generic antiviral drugs. Observations: Cholesterol promotes the development of atherosclerosis by activating NLR family pyrin domain containing 3 (NLRP3), and the resulting inflammatory environment indirectly contributes to COVID-19 infection and subsequent deterioration. In in vitro studies, membrane cholesterol increased the number of viral entry sites on the host cell membrane and the number of angiotensin-converting enzyme 2 (ACE2) receptors in the membrane fusion site. Previous studies have shown that the fusion protein of the virus interacts with cholesterol, and the spike protein of SARS-CoV-2 also requires cholesterol to enter the host cells. Cholesterol in blood interacts with the spike protein to promote the entry of spike cells, wherein the scavenger receptor class B type 1 (SR-B1) plays an important role. Because of the cardiovascular protective effects of lipid-lowering therapy and the additional anti-inflammatory effects of lipid-lowering drugs, it is currently recommended to continue lipid-lowering therapy for patients with COVID-19, but the safety of extremely low LDL-C is questionable. Conclusions and Relevance: Cholesterol can indirectly increase the susceptibility of patients to SARS-CoV-2 and increase the risk of death from COVID-19, which are mediated by NLRP3 and atherosclerotic plaques, respectively. Cholesterol present in the host cell membrane, virus, and blood may also directly participate in the virus cell entry process, but the specific mechanism still needs further study. Patients with COVID-19 are recommended to continue lipid-lowering therapy.
Collapse
Affiliation(s)
- Yan Tang
- Department of Cardiology, Heart Center, Zhujiang Hospital, Southern Medical University, 235 Industrial Avenue, Guangzhou, 510282, Guangdong, People's Republic of China
- Zhujiang Hospital, Southern Medical University/The Second School of Clinical Medicine, Southern Medical University, No. 6, Chenggui Road, East District, Zhongshan, 528403, Guangdong, People's Republic of China
| | - Longtai Hu
- Department of Cardiology, Heart Center, Zhujiang Hospital, Southern Medical University, 235 Industrial Avenue, Guangzhou, 510282, Guangdong, People's Republic of China
- School of Traditional Chinese Medicine, Southern Medical University, No. 6, Chenggui Road, East District, Zhongshan, 528403, Guangdong, People's Republic of China
| | - Yi Liu
- Department of Cardiology, Heart Center, Zhujiang Hospital, Southern Medical University, 235 Industrial Avenue, Guangzhou, 510282, Guangdong, People's Republic of China
- Zhujiang Hospital, Southern Medical University/The Second School of Clinical Medicine, Southern Medical University, No. 6, Chenggui Road, East District, Zhongshan, 528403, Guangdong, People's Republic of China
| | - Bangyi Zhou
- Department of Cardiology, Heart Center, Zhujiang Hospital, Southern Medical University, 235 Industrial Avenue, Guangzhou, 510282, Guangdong, People's Republic of China
- Zhujiang Hospital, Southern Medical University/The Second School of Clinical Medicine, Southern Medical University, No. 6, Chenggui Road, East District, Zhongshan, 528403, Guangdong, People's Republic of China
| | - Xiaohuan Qin
- Department of Cardiology, Heart Center, Zhujiang Hospital, Southern Medical University, 235 Industrial Avenue, Guangzhou, 510282, Guangdong, People's Republic of China
- Zhujiang Hospital, Southern Medical University/The Second School of Clinical Medicine, Southern Medical University, No. 6, Chenggui Road, East District, Zhongshan, 528403, Guangdong, People's Republic of China
| | - Jujian Ye
- Department of Cardiology, Heart Center, Zhujiang Hospital, Southern Medical University, 235 Industrial Avenue, Guangzhou, 510282, Guangdong, People's Republic of China
- Zhujiang Hospital, Southern Medical University/The Second School of Clinical Medicine, Southern Medical University, No. 6, Chenggui Road, East District, Zhongshan, 528403, Guangdong, People's Republic of China
| | - Maoze Shen
- Department of Cardiology, Raoping County People's Hospital, 161 Caichang Street, Huanggang Town, Chaozhou, 515700, Guangdong, People's Republic of China
| | - Zhijian Wu
- Department of Cardiology, Affiliated Boai Hospital of Zhongshan, Southern Medical University, No. 6, Chenggui Road, East District, Zhongshan, 528403, Guangdong, People's Republic of China
| | - Peidong Zhang
- Department of Cardiology, Heart Center, Zhujiang Hospital, Southern Medical University, 235 Industrial Avenue, Guangzhou, 510282, Guangdong, People's Republic of China
| |
Collapse
|
6
|
Loney RW, Brandner B, Dagan MP, Smith PN, Roche M, Fritz JR, Hall SB, Tristram-Nagle SA. Changes in membrane elasticity caused by the hydrophobic surfactant proteins correlate poorly with adsorption of lipid vesicles. SOFT MATTER 2021; 17:3358-3366. [PMID: 33630985 PMCID: PMC8016726 DOI: 10.1039/d0sm02223c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
To establish how the hydrophobic surfactant proteins, SP-B and SP-C, promote adsorption of lipids to an air/water interface, we used X-ray diffuse scattering (XDS) to determine an order parameter of the lipid chains (Sxray) and the bending modulus of the lipid bilayers (KC). Samples contained different amounts of the proteins with two sets of lipids. Dioleoylphosphatidylcholine (DOPC) provided a simple, well characterized model system. The nonpolar and phospholipids (N&PL) from extracted calf surfactant provided the biological mix of lipids. For both systems, the proteins produced changes in Sxray that correlated well with KC. The dose-response to the proteins, however, differed. Small amounts of protein generated large decreases in Sxray and KC for DOPC that progressed monotonically. The changes for the surfactant lipids were erratic. Our studies then tested whether the proteins produced correlated effects on adsorption. Experiments measured the initial fall in surface tension during adsorption to a constant surface area, and then expansion of the interface during adsorption at a constant surface tension of 40 mN m-1. The proteins produced a sigmoidal increase in the rate of adsorption at 40 mN m-1 for both lipids. The results correlated poorly with the changes in Sxray and KC in both cases. Disordering of the lipid chains produced by the proteins, and the softening of the bilayers, fail to explain how the proteins promote adsorption of lipid vesicles.
Collapse
Affiliation(s)
- Ryan W Loney
- Pulmonary and Critical Care Medicine, Oregon Health & Science University, Portland, Oregon 97239, USA.
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Kwon B, Mandal T, Elkins MR, Oh Y, Cui Q, Hong M. Cholesterol Interaction with the Trimeric HIV Fusion Protein gp41 in Lipid Bilayers Investigated by Solid-State NMR Spectroscopy and Molecular Dynamics Simulations. J Mol Biol 2020; 432:4705-4721. [PMID: 32592698 PMCID: PMC7781112 DOI: 10.1016/j.jmb.2020.06.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 06/07/2020] [Accepted: 06/18/2020] [Indexed: 12/13/2022]
Abstract
HIV-1 entry into cells is mediated by the fusion protein gp41. Cholesterol plays an important role in this virus-cell fusion, but molecular structural information about cholesterol-gp41 interaction is so far absent. Here, we present experimental and computational data about cholesterol complexation with gp41 in lipid bilayers. We focus on the C-terminal region of the protein, which comprises a membrane-proximal external region (MPER) and the transmembrane domain (TMD). We measured peptide-cholesterol contacts in virus-mimetic lipid bilayers using solid-state NMR spectroscopy, and augmented these experimental data with all-atom molecular dynamics simulations. 2D 19F NMR spectra show correlation peaks between MPER residues and the cholesterol isooctyl tail, indicating that cholesterol is in molecular contact with the MPER-TMD trimer. 19F-13C distance measurements between the peptide and 13C-labeled cholesterol show that C17 on the D ring and C9 at the intersection of B and C rings are ~7.0 Å from the F673 side-chain 4-19F. At high peptide concentrations in the membrane, the 19F-13C distance data indicate three cholesterol molecules bound near F673 in each trimer. Mutation of a cholesterol recognition amino acid consensus motif did not change these distances, indicating that cholesterol binding does not require this sequence motif. Molecular dynamics simulations further identify two hotspots for cholesterol interactions. Taken together, these experimental data and simulations indicate that the helix-turn-helix conformation of the MPER-TMD is responsible for sequestering cholesterol. We propose that this gp41-cholesterol interaction mediates virus-cell fusion by recruiting gp41 to the boundary of the liquid-disordered and liquid-ordered phases to incur membrane curvature.
Collapse
Affiliation(s)
- Byungsu Kwon
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, USA
| | - Taraknath Mandal
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA
| | - Matthew R Elkins
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, USA
| | - Younghoon Oh
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA
| | - Qiang Cui
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA; Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA; Department of Biomedical Engineering, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, USA.
| |
Collapse
|
8
|
Munusamy S, Conde R, Bertrand B, Munoz-Garay C. Biophysical approaches for exploring lipopeptide-lipid interactions. Biochimie 2020; 170:173-202. [PMID: 31978418 PMCID: PMC7116911 DOI: 10.1016/j.biochi.2020.01.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 01/19/2020] [Indexed: 02/07/2023]
Abstract
In recent years, lipopeptides (LPs) have attracted a lot of attention in the pharmaceutical industry due to their broad-spectrum of antimicrobial activity against a variety of pathogens and their unique mode of action. This class of compounds has enormous potential for application as an alternative to conventional antibiotics and for pest control. Understanding how LPs work from a structural and biophysical standpoint through investigating their interaction with cell membranes is crucial for the rational design of these biomolecules. Various analytical techniques have been developed for studying intramolecular interactions with high resolution. However, these tools have been barely exploited in lipopeptide-lipid interactions studies. These biophysical approaches would give precise insight on these interactions. Here, we reviewed these state-of-the-art analytical techniques. Knowledge at this level is indispensable for understanding LPs activity and particularly their potential specificity, which is relevant information for safe application. Additionally, the principle of each analytical technique is presented and the information acquired is discussed. The key challenges, such as the selection of the membrane model are also been briefly reviewed. A brief overview of topics to understand the generalities of lipopeptide (LP) science. Main analytical techniques used to reveal the interaction and the distorting effect of LP on artificial membranes. Guidelines for selecting of the most adequate membrane models for the given analytical technique.
Collapse
Affiliation(s)
- Sathishkumar Munusamy
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Mexico
| | - Renaud Conde
- Centro de Investigación Sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Cuernavaca, Morelos, Mexico
| | - Brandt Bertrand
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Mexico
| | - Carlos Munoz-Garay
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210, Cuernavaca, Mexico.
| |
Collapse
|
9
|
Salimi H, Johnson J, Flores MG, Zhang MS, O'Malley Y, Houtman JC, Schlievert PM, Haim H. The lipid membrane of HIV-1 stabilizes the viral envelope glycoproteins and modulates their sensitivity to antibody neutralization. J Biol Chem 2019; 295:348-362. [PMID: 31757809 DOI: 10.1074/jbc.ra119.009481] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 11/19/2019] [Indexed: 11/06/2022] Open
Abstract
The envelope glycoproteins (Envs) of HIV-1 are embedded in the cholesterol-rich lipid membrane of the virus. Chemical depletion of cholesterol from HIV-1 particles inactivates their infectivity. We observed that diverse HIV-1 strains exhibit a range of sensitivities to such treatment. Differences in sensitivity to cholesterol depletion could not be explained by variation in Env components known to interact with cholesterol, including the cholesterol-recognition motif and cytoplasmic tail of gp41. Using antibody-binding assays, measurements of virus infectivity, and analyses of lipid membrane order, we found that depletion of cholesterol from HIV-1 particles decreases the conformational stability of Env. It enhances exposure of partially cryptic epitopes on the trimer and increases sensitivity to structure-perturbing treatments such as antibodies and cold denaturation. Substitutions in the cholesterol-interacting motif of gp41 induced similar effects as depletion of cholesterol. Surface-acting agents, which are incorporated into the virus lipid membrane, caused similar effects as disruption of the Env-cholesterol interaction. Furthermore, substitutions in gp120 that increased structural stability of Env (i.e. induced a "closed" conformation of the trimer) increased virus resistance to cholesterol depletion and to the surface-acting agents. Collectively, these results indicate a critical contribution of the viral membrane to the stability of the Env trimer and to neutralization resistance against antibodies. Our findings suggest that the potency of poorly neutralizing antibodies, which are commonly elicited in vaccinated individuals, may be markedly enhanced by altering the lipid composition of the viral membrane.
Collapse
Affiliation(s)
- Hamid Salimi
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Jacklyn Johnson
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Manuel G Flores
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Michael S Zhang
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Yunxia O'Malley
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Jon C Houtman
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Patrick M Schlievert
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Hillel Haim
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242.
| |
Collapse
|
10
|
Kumagai A, Dupuy FG, Arsov Z, Elhady Y, Moody D, Ernst RK, Deslouches B, Montelaro RC, Peter Di Y, Tristram-Nagle S. Elastic behavior of model membranes with antimicrobial peptides depends on lipid specificity and d-enantiomers. SOFT MATTER 2019; 15:1860-1868. [PMID: 30702120 PMCID: PMC7485610 DOI: 10.1039/c8sm02180e] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
In an effort to provide new treatments for the global crisis of bacterial resistance to current antibiotics, we have used a rational approach to design several new antimicrobial peptides (AMPs). The present study focuses on 24-mer WLBU2 and its derivative, D8, with the amino acid sequence, RRWVRRVRRWVRRVVRVVRRWVRR. In D8, all of the valines are the d-enantiomer. We use X-ray low- and wide-angle diffuse scattering data to measure elasticity and lipid chain order. We show a good correlation between in vitro bacterial killing efficiency and both bending and chain order behavior in bacterial lipid membrane mimics; our results suggest that AMP-triggered domain formation could be the mechanism of bacterial killing in both Gram-positive and Gram-negative bacteria. In red blood cell lipid mimics, D8 stiffens and orders the membrane, while WLBU2 softens and disorders it, which correlate with D8's harmless vs. WLBU2's toxic behavior in hemolysis tests. These results suggest that elasticity and chain order behavior can be used to predict mechanisms of bactericidal action and toxicity of new AMPs.
Collapse
Affiliation(s)
- Akari Kumagai
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Fantini J, Epand RM, Barrantes FJ. Cholesterol-Recognition Motifs in Membrane Proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1135:3-25. [PMID: 31098808 DOI: 10.1007/978-3-030-14265-0_1] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The impact of cholesterol on the structure and function of membrane proteins was recognized several decades ago, but the molecular mechanisms underlying these effects have remained elusive. There appear to be multiple mechanisms by which cholesterol interacts with proteins. A complete understanding of cholesterol-sensing motifs is still undergoing refinement. Initially, cholesterol was thought to exert only non-specific effects on membrane fluidity. It was later shown that this lipid could specifically interact with membrane proteins and affect both their structure and function. In this article, we have summarized and critically analyzed our evolving understanding of the affinity, specificity and stereoselectivity of the interactions of cholesterol with membrane proteins. We review the different computational approaches that are currently used to identify cholesterol binding sites in membrane proteins and the biochemical logic that governs each type of site, including CRAC, CARC, SSD and amphipathic helix motifs. There are physiological implications of these cholesterol-recognition motifs for G-protein coupled receptors (GPCR) and ion channels, in membrane trafficking and membrane fusion (SNARE) proteins. There are also pathological implications of cholesterol binding to proteins involved in neurological disorders (Alzheimer, Parkinson, Creutzfeldt-Jakob) and HIV fusion. In each case, our discussion is focused on the key molecular aspects of the cholesterol and amino acid motifs in membrane-embedded regions of membrane proteins that define the physiologically relevant crosstalk between the two. Our understanding of the factors that determine if these motifs are functional in cholesterol binding will allow us enhanced predictive capabilities.
Collapse
Affiliation(s)
- Jacques Fantini
- INSERM UMR_S 1072, Marseille, France. .,Aix-Marseille Université, Marseille, France.
| | - Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, Hamilton, ON, Canada
| | - Francisco J Barrantes
- Laboratory of Molecular Neurobiology, Biomedical Research Institute (BIOMED), UCA-CONICET, Buenos Aires, Argentina
| |
Collapse
|
12
|
Molugu TR, Brown MF. Cholesterol Effects on the Physical Properties of Lipid Membranes Viewed by Solid-state NMR Spectroscopy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:99-133. [PMID: 30649757 DOI: 10.1007/978-3-030-04278-3_5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In this chapter, we review the physical properties of lipid/cholesterol mixtures involving studies of model membranes using solid-state NMR spectroscopy. The approach allows one to quantify the average membrane structure, fluctuations, and elastic deformation upon cholesterol interaction. Emphasis is placed on understanding the membrane structural deformation and emergent fluctuations at an atomistic level. Lineshape measurements using solid-state NMR spectroscopy give equilibrium structural properties, while relaxation time measurements study the molecular dynamics over a wide timescale range. The equilibrium properties of glycerophospholipids, sphingolipids, and their binary and tertiary mixtures with cholesterol are accessible. Nonideal mixing of cholesterol with other lipids explains the occurrence of liquid-ordered domains. The entropic loss upon addition of cholesterol to sphingolipids is less than for glycerophospholipids, and may drive formation of lipid rafts. The functional dependence of 2H NMR spin-lattice relaxation (R 1Z) rates on segmental order parameters (S CD) for lipid membranes is indicative of emergent viscoelastic properties. Addition of cholesterol shows stiffening of the bilayer relative to the pure lipids and this effect is diminished for lanosterol. Opposite influences of cholesterol and detergents on collective dynamics and elasticity at an atomistic scale can potentially affect lipid raft formation in cellular membranes.
Collapse
Affiliation(s)
- Trivikram R Molugu
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA. .,Department of Physics, University of Arizona, Tucson, AZ, USA.
| |
Collapse
|
13
|
Britt HM, Mosely JA, Sanderson JM. The influence of cholesterol on melittin lipidation in neutral membranes. Phys Chem Chem Phys 2019; 21:631-640. [DOI: 10.1039/c8cp06661b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cholesterol inclusion in membranes influences the rate and selectivity of acyl transfer from lipids to a membrane-embedded peptide.
Collapse
|
14
|
Chang EH, Huang J, Lin Z, Brown AC. Catechin-mediated restructuring of a bacterial toxin inhibits activity. Biochim Biophys Acta Gen Subj 2018; 1863:191-198. [PMID: 30342156 DOI: 10.1016/j.bbagen.2018.10.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 10/12/2018] [Accepted: 10/15/2018] [Indexed: 10/28/2022]
Abstract
BACKGROUND Catechins, polyphenols derived from tea leaves, have been shown to have antibacterial properties, through direct killing of bacteria as well as through inhibition of bacterial toxin activity. In particular, certain catechins have been shown to have bactericidal effects on the oral bacterium, Aggregatibacter actinomycetemcomitans, as well as the ability to inhibit a key virulence factor of this organism, leukotoxin (LtxA). The mechanism of catechin-mediated inhibition of LtxA has not been shown. METHODS In this work, we studied the ability of six catechins to inhibit LtxA-mediated cytotoxicity in human white blood cells, using Trypan blue staining, and investigated the mechanism of action using a combination of techniques, including fluorescence and circular dichroism spectroscopy, confocal microscopy, and surface plasmon resonance. RESULTS We found that all the catechins except (-)-catechin inhibited the activity of this protein, with the galloylated catechins having the strongest effect. Pre-incubation of the toxin with the catechins increased the inhibitory action, indicating that the catechins act on the protein, rather than the cell. The secondary structure of LtxA was dramatically altered in the presence of catechin, which resulted in an inhibition of toxin binding to cholesterol, an important initial step in the cytotoxic mechanism of the toxin. CONCLUSIONS These results demonstrate that the catechins inhibit LtxA activity by altering its structure to prevent interaction with specific molecules present on the host cell surface. GENERAL SIGNIFICANCE Galloylated catechins modify protein toxin structure, inhibiting the toxin from binding to the requisite molecules on the host cell surface.
Collapse
Affiliation(s)
- En Hyung Chang
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Joanne Huang
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Zixiang Lin
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Angela C Brown
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA.
| |
Collapse
|
15
|
Rout AK, Wu X, Starich MR, Strub MP, Hammer JA, Tjandra N. The Structure of Melanoregulin Reveals a Role for Cholesterol Recognition in the Protein's Ability to Promote Dynein Function. Structure 2018; 26:1373-1383.e4. [PMID: 30174147 DOI: 10.1016/j.str.2018.07.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 06/12/2018] [Accepted: 07/24/2018] [Indexed: 01/24/2023]
Abstract
Melanoregulin (Mreg) is a small, highly charged, multiply palmitoylated protein present on the membrane of melanosomes. Mreg is implicated in the transfer of melanosomes from melanocytes to keratinocytes, and in promoting the microtubule minus end-directed transport of these organelles. The possible molecular function of Mreg was identified by solving its structure using nuclear magnetic resonance (NMR) spectroscopy. Mreg contains six α helices forming a fishhook-like fold in which positive and negative charges occupy opposite sides of the protein's surface and sandwich a putative, cholesterol recognition sequence (CRAC motif). Mreg containing a point mutation within its CRAC motif still targets to late endosomes/lysosomes, but no longer promotes their microtubule minus end-directed transport. Moreover, wild-type Mreg does not promote the microtubule minus end-directed transport of late endosomes/lysosomes in cells transiently depleted of cholesterol. Finally, reversing the charge of three clustered acidic residues partially inhibits Mreg's ability to drive these organelles to microtubule minus ends.
Collapse
Affiliation(s)
- Ashok K Rout
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Xufeng Wu
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Mary R Starich
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Marie-Paule Strub
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - John A Hammer
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Nico Tjandra
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
16
|
Abstract
This review summarizes over a decade of investigations into how membrane-binding proteins from the HIV-1 virus interact with lipid membrane mimics various HIV and host T-cell membranes. The goal of the work was to characterize at the molecular level both the elastic and structural changes that occur due to HIV protein/membrane interactions, which could lead to new drugs to thwart the HIV virus. The main technique used to study these interactions is diffuse X-ray scattering, which yields the bending modulus, KC, as well as structural parameters such as membrane thickness, area/lipid and position of HIV peptides (parts of HIV proteins) in the membrane. Our methods also yield information about lipid chain order or disorder caused by the peptides. This review focuses on three stages of the HIV-1 life cycle: 1) infection, 2) Tat membrane transport, and 3) budding. In the infection stage, our lab studied three different parts of HIV-1 gp41 (glycoprotein 41 fusion protein): 1) FP23, the N-terminal 23 amino acids that interact non-specifically with the T-cell host membrane to cause fusion of two membranes, and its trimer version, 2) CRAC (cholesterol recognition amino acid consensus sequence), on the MPER (membrane proximal external region) near the membrane-spanning domain, and 3) LLP2 (lentiviral lytic peptide 2) on the CTT (cytoplasmic C-terminal tail). For Tat transport, we used membrane mimics of the T-cell nuclear membrane as well as simpler models that varied charge and negative curvature. For membrane budding, we varied the myristoylation of the MA31 peptide as well as the negatively charged lipid. These studies show that HIV peptides with different roles in the HIV life cycle affect differently the relevant membrane mimics. In addition, the membrane lipid composition plays an important role in the peptides' effects.
Collapse
|
17
|
Doktorova M, Harries D, Khelashvili G. Determination of bending rigidity and tilt modulus of lipid membranes from real-space fluctuation analysis of molecular dynamics simulations. Phys Chem Chem Phys 2018. [PMID: 28627570 DOI: 10.1039/c7cp01921a] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We have recently developed a novel computational methodology (termed RSF for Real-Space Fluctuations) to quantify the bending rigidity and tilt modulus of lipid membranes from real-space analysis of fluctuations in the tilt and splay degrees of freedom as sampled in molecular dynamics (MD) simulations. In this article, we present a comprehensive study that combines results from the application of the RSF method to a wide range of lipid bilayer systems that encompass membranes of different fluidities and sizes, including lipids with saturated and unsaturated lipid tails, single and multi-component lipid systems, as well as non-standard lipids such as the four-tailed cardiolipin. By comparing the material properties calculated with the RSF method to those obtained from experimental data and from other computational methodologies, we rigorously demonstrate the validity of our approach and show its robustness. This should allow for future applications of even more complex lipidic assemblies, whose material properties are not tractable by other computational techniques. In addition, we discuss the relationship between different definitions of the tilt modulus appearing in current literature to address some important unresolved discrepancies in the field.
Collapse
Affiliation(s)
- M Doktorova
- Tri-Institutional PhD Program in Computational Biology and Medicine, Weill Cornell Medical College, 1300 York Avenue, New York, NY 10065, USA
| | | | | |
Collapse
|
18
|
DeLeon O, Hodis H, O’Malley Y, Johnson J, Salimi H, Zhai Y, Winter E, Remec C, Eichelberger N, Van Cleave B, Puliadi R, Harrington RD, Stapleton JT, Haim H. Accurate predictions of population-level changes in sequence and structural properties of HIV-1 Env using a volatility-controlled diffusion model. PLoS Biol 2017; 15:e2001549. [PMID: 28384158 PMCID: PMC5383018 DOI: 10.1371/journal.pbio.2001549] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 03/06/2017] [Indexed: 01/08/2023] Open
Abstract
The envelope glycoproteins (Envs) of HIV-1 continuously evolve in the host by random mutations and recombination events. The resulting diversity of Env variants circulating in the population and their continuing diversification process limit the efficacy of AIDS vaccines. We examined the historic changes in Env sequence and structural features (measured by integrity of epitopes on the Env trimer) in a geographically defined population in the United States. As expected, many Env features were relatively conserved during the 1980s. From this state, some features diversified whereas others remained conserved across the years. We sought to identify “clues” to predict the observed historic diversification patterns. Comparison of viruses that cocirculate in patients at any given time revealed that each feature of Env (sequence or structural) exists at a defined level of variance. The in-host variance of each feature is highly conserved among individuals but can vary between different HIV-1 clades. We designate this property “volatility” and apply it to model evolution of features as a linear diffusion process that progresses with increasing genetic distance. Volatilities of different features are highly correlated with their divergence in longitudinally monitored patients. Volatilities of features also correlate highly with their population-level diversification. Using volatility indices measured from a small number of patient samples, we accurately predict the population diversity that developed for each feature over the course of 30 years. Amino acid variants that evolved at key antigenic sites are also predicted well. Therefore, small “fluctuations” in feature values measured in isolated patient samples accurately describe their potential for population-level diversification. These tools will likely contribute to the design of population-targeted AIDS vaccines by effectively capturing the diversity of currently circulating strains and addressing properties of variants expected to appear in the future. HIV-1 is the causative agent of the global AIDS pandemic. The envelope glycoproteins (Envs) of HIV-1 constitute a primary target for antibody-based vaccines. However, the diversity of Envs in the population limits the potential efficacy of this approach. Accurate estimates of the range of variants that currently infect patients and those expected to appear in the future will likely contribute to the design of population-targeted immunogens. We found that different properties (features) of Env have different propensities for small “fluctuations” in their values among viruses that infect patients at any given time point. This propensity of each feature for in-host variance, which we designate “volatility”, is conserved among patients. We apply this parameter to model the evolution of features (in patients and population) as a diffusion process driven by their “diffusion coefficients” (volatilities). Using volatilities measured from a few patient samples from the 1980s, we accurately predict properties of viruses that evolved in the population over the course of 30 years. The diffusion-based model described here efficiently captures evolution of phenotypes in biological systems controlled by a dominant random component.
Collapse
Affiliation(s)
- Orlando DeLeon
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Hagit Hodis
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Yunxia O’Malley
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Jacklyn Johnson
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Hamid Salimi
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Yinjie Zhai
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Elizabeth Winter
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Claire Remec
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Noah Eichelberger
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Brandon Van Cleave
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Ramya Puliadi
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Robert D. Harrington
- Center for AIDS Research (CFAR) at the University of Washington, Seattle, Washington, United States of America
| | - Jack T. Stapleton
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
- Veterans Affairs Medical Center, Iowa City, Iowa, United States of America
| | - Hillel Haim
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
| |
Collapse
|
19
|
Carrillo JMY, Katsaras J, Sumpter BG, Ashkar R. A Computational Approach for Modeling Neutron Scattering Data from Lipid Bilayers. J Chem Theory Comput 2017; 13:916-925. [DOI: 10.1021/acs.jctc.6b00968] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
| | - John Katsaras
- Department
of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | | | | |
Collapse
|
20
|
Koufos E, Chang EH, Rasti ES, Krueger E, Brown AC. Use of a Cholesterol Recognition Amino Acid Consensus Peptide To Inhibit Binding of a Bacterial Toxin to Cholesterol. Biochemistry 2016; 55:4787-97. [PMID: 27504950 DOI: 10.1021/acs.biochem.6b00430] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Recognition of and binding to cholesterol on the host cell membrane is an initial step in the mechanism of numerous pathogens, including viruses, bacteria, and bacterial toxins; however, a viable method of inhibiting this interaction has not yet been uncovered. Here, we describe the mechanism by which a cholesterol recognition amino acid consensus peptide interacts with cholesterol and inhibits the activity of a cholesterol-binding bacterial leukotoxin (LtxA). Using a series of biophysical techniques, we have shown that the peptide recognizes the hydroxyl group of cholesterol with nanomolar affinity and does not disrupt membrane packing, suggesting that it sits primarily near the membrane surface. As a result, LtxA is unable to bind to cholesterol or subsequently become internalized in host cells. Additionally, because cholesterol is not being removed from the cell membrane, the peptide-treated target cells remain viable over extended periods of time. We have demonstrated the use of this peptide in the inhibition of toxin activity for an antivirulence approach to the treatment of bacterial disease, and we anticipate that this approach might have broad utility in the inhibition of viral and bacterial pathogenesis.
Collapse
Affiliation(s)
- Evan Koufos
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - En Hyung Chang
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - Elnaz S Rasti
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - Eric Krueger
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - Angela C Brown
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| |
Collapse
|
21
|
Oliva R, Emendato A, Vitiello G, De Santis A, Grimaldi M, D'Ursi AM, Busi E, Del Vecchio P, Petraccone L, D'Errico G. On the microscopic and mesoscopic perturbations of lipid bilayers upon interaction with the MPER domain of the HIV glycoprotein gp41. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1904-13. [DOI: 10.1016/j.bbamem.2016.05.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 05/04/2016] [Accepted: 05/09/2016] [Indexed: 12/15/2022]
|
22
|
West A, Brummel BE, Braun AR, Rhoades E, Sachs JN. Membrane remodeling and mechanics: Experiments and simulations of α-Synuclein. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1858:1594-609. [PMID: 26972046 PMCID: PMC5081225 DOI: 10.1016/j.bbamem.2016.03.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 03/05/2016] [Accepted: 03/07/2016] [Indexed: 01/24/2023]
Abstract
We review experimental and simulation approaches that have been used to determine curvature generation and remodeling of lipid bilayers by membrane-bending proteins. Particular emphasis is placed on the complementary approaches used to study α-Synuclein (αSyn), a major protein involved in Parkinson's disease (PD). Recent cellular and biophysical experiments have shown that the protein 1) deforms the native structure of mitochondrial and model membranes; and 2) inhibits vesicular fusion. Today's advanced experimental and computational technology has made it possible to quantify these protein-induced changes in membrane shape and material properties. Collectively, experiments, theory and multi-scale simulation techniques have established the key physical determinants of membrane remodeling and rigidity: protein binding energy, protein partition depth, protein density, and membrane tension. Despite the exciting and significant progress made in recent years in these areas, challenges remain in connecting biophysical insights to the cellular processes that lead to disease. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov.
Collapse
Affiliation(s)
- Ana West
- Department of Biomedical Engineering, University of Minnesota, 312 Church St. SE, Minneapolis, MN 55455, USA
| | - Benjamin E Brummel
- Department of Biomedical Engineering, University of Minnesota, 312 Church St. SE, Minneapolis, MN 55455, USA
| | - Anthony R Braun
- Department of Neuroscience, University of Minnesota, 321 Church St. SE, Minneapolis, MN 55455, USA
| | - Elizabeth Rhoades
- Department of Chemistry, University of Pennsylvania, 231 S 34th St., Philadelphia, PA 19104, USA
| | - Jonathan N Sachs
- Department of Biomedical Engineering, University of Minnesota, 312 Church St. SE, Minneapolis, MN 55455, USA.
| |
Collapse
|
23
|
In Vivo Analysis of Infectivity, Fusogenicity, and Incorporation of a Mutagenic Viral Glycoprotein Library Reveals Determinants for Virus Incorporation. J Virol 2016; 90:6502-14. [PMID: 27147747 DOI: 10.1128/jvi.00804-16] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 04/27/2016] [Indexed: 12/14/2022] Open
Abstract
UNLABELLED Enveloped viruses utilize transmembrane surface glycoproteins to gain entry into target cells. Glycoproteins from diverse viral families can be incorporated into nonnative viral particles in a process termed pseudotyping; however, the molecular mechanisms governing acquisition of these glycoproteins are poorly understood. For murine leukemia virus envelope (MLV Env) glycoprotein, incorporation into foreign viral particles has been shown to be an active process, but it does not appear to be caused by direct interactions among viral proteins. In this study, we coupled in vivo selection systems with Illumina next-generation sequencing (NGS) to test hundreds of thousands of MLV Env mutants for the ability to be enriched in viral particles and to perform other glycoprotein functions. NGS analyses on a subset of these mutants predicted that the residues important for incorporation are in the membrane-proximal external region (MPER), particularly W127 and W137, and the residues in the membrane-spanning domain (MSD) and also immediately flanking it (T140 to L163). These predictions were validated by directly measuring the impact of mutations in these regions on fusogenicity, infectivity, and incorporation. We suggest that these two regions dictate pseudotyping through interactions with specific lipid environments formed during viral assembly. IMPORTANCE Researchers from numerous fields routinely exploit the ability to manipulate viral tropism by swapping viral surface proteins. However, this process, termed pseudotyping, is poorly understood at the molecular level. For murine leukemia virus envelope (MLV Env) glycoprotein, incorporation into foreign viral particles is an active process, but it does not appear to occur through direct viral protein-protein interactions. In this study, we tested hundreds of thousands of MLV Env mutants for the ability to be enriched in viral particles as well as perform other glycoprotein functions. Our analyses on a subset of these mutants predict that the glycoprotein regions embedded in and immediately flanking the viral membrane dictate active incorporation into viral particles. We suggest that pseudotyping occurs through specific lipid-protein interactions at the viral assembly site.
Collapse
|
24
|
Molugu TR, Brown MF. Cholesterol-induced suppression of membrane elastic fluctuations at the atomistic level. Chem Phys Lipids 2016; 199:39-51. [PMID: 27154600 DOI: 10.1016/j.chemphyslip.2016.05.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 04/29/2016] [Accepted: 05/02/2016] [Indexed: 12/14/2022]
Abstract
Applications of solid-state NMR spectroscopy for investigating the influences of lipid-cholesterol interactions on membrane fluctuations are reviewed in this paper. Emphasis is placed on understanding the energy landscapes and fluctuations at an emergent atomistic level. Solid-state (2)H NMR spectroscopy directly measures residual quadrupolar couplings (RQCs) due to individual C-(2)H labeled segments of the lipid molecules. Moreover, residual dipolar couplings (RDCs) of (13)C-(1)H bonds are obtained in separated local-field NMR spectroscopy. The distributions of RQC or RDC values give nearly complete profiles of the order parameters as a function of acyl segment position. Measured equilibrium properties of glycerophospholipids and sphingolipids including their binary and tertiary mixtures with cholesterol show unequal mixing associated with liquid-ordered domains. The entropic loss upon addition of cholesterol to sphingolipids is less than for glycerophospholipids and may drive the formation of lipid rafts. In addition relaxation time measurements enable one to study the molecular dynamics over a wide time-scale range. For (2)H NMR the experimental spin-lattice (R1Z) relaxation rates follow a theoretical square-law dependence on segmental order parameters (SCD) due to collective slow dynamics over mesoscopic length scales. The functional dependence for the liquid-crystalline lipid membranes is indicative of viscoelastic properties as they emerge from atomistic-level interactions. A striking decrease in square-law slope upon addition of cholesterol denotes stiffening relative to the pure lipid bilayers that is diminished in the case of lanosterol. Measured equilibrium properties and relaxation rates infer opposite influences of cholesterol and detergents on collective dynamics and elasticity at an atomistic scale that potentially affects lipid raft formation in cellular membranes.
Collapse
Affiliation(s)
- Trivikram R Molugu
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA; Department of Physics, University of Arizona, Tucson, AZ 85721, USA.
| |
Collapse
|
25
|
Janoudi A, Shamoun FE, Kalavakunta JK, Abela GS. Cholesterol crystal induced arterial inflammation and destabilization of atherosclerotic plaque. Eur Heart J 2015; 37:1959-67. [PMID: 26705388 DOI: 10.1093/eurheartj/ehv653] [Citation(s) in RCA: 146] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 11/16/2015] [Indexed: 01/14/2023] Open
Abstract
Evolution of plaque that is prone to rupture is characterized by inflammation and physical changes. Accumulation of low-density lipoprotein in the sub-intima provides esterified cholesterol (ESC) to macrophages and smooth muscle cells that convert it into free cholesterol (FRC) by cholesteryl ester hydrolases (CEHs). Membrane-bound cholesterol carriers transport FRC to high-density lipoprotein (HDL). Impaired HDL transport function and altered composition can lead to extracellular accumulation of FRC, whereas impaired membrane carrier activity can lead to intracellular FRC accumulation. Saturation of FRC can result in cholesterol crystallization with cell death and intimal injury. Disequilibrium between ESC and FRC can impact foam cell and cholesterol crystal (CC) formation. Cholesterol crystals initiate inflammation via NLRP3 inflammasome leading to interleukin-1β (IL-1β) production inducing C-reactive protein. Eventually, crystals growing from within the plaque and associated inflammation destabilize the plaque. Thus, inhibition of inflammation by antagonists to IL-1β or agents that dissolve or prevent CC formation may stabilize vulnerable plaques.
Collapse
Affiliation(s)
- Abed Janoudi
- Department of Medicine, Division of Cardiology, Michigan State University, East Lansing, MI, USA
| | - Fadi E Shamoun
- Division of Cardiovascular Diseases, Mayo Clinic, Phoenix, AZ, USA
| | - Jagadeesh K Kalavakunta
- Department of Medicine, Division of Cardiology, Michigan State University, East Lansing, MI, USA Borgess Hospital, Kalamazoo, MI, USA
| | - George S Abela
- Department of Medicine, Division of Cardiology, Michigan State University, East Lansing, MI, USA Department of Physiology, Division of Pathology, Michigan State University, East Lansing, MI, USA
| |
Collapse
|
26
|
Tristram-Nagle S. Use of X-Ray and Neutron Scattering Methods with Volume Measurements to Determine Lipid Bilayer Structure and Number of Water Molecules/Lipid. Subcell Biochem 2015; 71:17-43. [PMID: 26438260 DOI: 10.1007/978-3-319-19060-0_2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In this chapter I begin with a historical perspective of membrane models, starting in the early twentieth century. As these membrane models evolved, so did experiments to characterize the structure and water content of purified lipid bilayers. The wide-spread use of the X-ray gravimetric, or Luzzati method, is critically discussed. The main motivation of the gravimetric technique is to determine the number of water molecules/lipid, n(W), and then derive other important structural quantities, such as area/lipid, A(L). Subsequent experiments from the Nagle/Tristram-Nagle laboratory using X-ray and neutron scattering, first determine A(L) and then calculate n(W), using molecular lipid V(L) and water V(W) volumes. This chapter describes the details of our volume experiments to carefully measure V(L). Our results also determine n(W)', the steric water associated with the lipid headgroup, and how our calculated value compares to many literature values of tightly-associated headgroup water.
Collapse
Affiliation(s)
- Stephanie Tristram-Nagle
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
| |
Collapse
|
27
|
Apellániz B, Nieva JL. Fusion-competent state induced by a C-terminal HIV-1 fusion peptide in cholesterol-rich membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1014-22. [PMID: 25617671 DOI: 10.1016/j.bbamem.2015.01.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 12/15/2014] [Accepted: 01/14/2015] [Indexed: 11/17/2022]
Abstract
The replicative cycle of the human immunodeficiency virus type-1 begins after fusion of the viral and target-cell membranes. The envelope glycoprotein gp41 transmembrane subunit contains conserved hydrophobic domains that engage and perturb the merging lipid bilayers. In this work, we have characterized the fusion-committed state generated in vesicles by CpreTM, a synthetic peptide derived from the sequence connecting the membrane-proximal external region (MPER) and the transmembrane domain (TMD) of gp41. Pre-loading cholesterol-rich vesicles with CpreTM rendered them competent for subsequent lipid-mixing with fluorescently-labeled target vesicles. Highlighting the physiological relevance of the lasting fusion-competent state, the broadly neutralizing antibody 4E10 bound to the CpreTM-primed vesicles and inhibited lipid-mixing. Heterotypic fusion assays disclosed dependence on the lipid composition of the vesicles that acted either as virus or cell membrane surrogates. Lipid-mixing exhibited above all a critical dependence on the cholesterol content in those experiments. We infer that the fusion-competent state described herein resembles bona-fide perturbations generated by the pre-hairpin MPER-TMD connection within the viral membrane.
Collapse
Affiliation(s)
- Beatriz Apellániz
- Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain.
| | - José L Nieva
- Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain.
| |
Collapse
|
28
|
Bending rigidity of phosphatidylserine-containing lipid bilayers in acidic aqueous solutions. Colloids Surf A Physicochem Eng Asp 2014. [DOI: 10.1016/j.colsurfa.2013.12.059] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
29
|
Boscia AL, Akabori K, Benamram Z, Michel JA, Jablin MS, Steckbeck JD, Montelaro RC, Nagle JF, Tristram-Nagle S. Membrane structure correlates to function of LLP2 on the cytoplasmic tail of HIV-1 gp41 protein. Biophys J 2014; 105:657-66. [PMID: 23931314 DOI: 10.1016/j.bpj.2013.06.042] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 06/18/2013] [Accepted: 06/24/2013] [Indexed: 11/30/2022] Open
Abstract
Mutation studies previously showed that the lentivirus lytic peptide (LLP2) sequence of the cytoplasmic C-terminal tail of the HIV-1 gp41 envelope protein inhibited viral-initiated T-cell death and T-cell syncytium formation, at which time in the HIV life cycle the gp41 protein is embedded in the T-cell membrane. In striking contrast, the mutants did not affect virion infectivity, during which time the gp41 protein is embedded in the HIV envelope membrane. To examine the role of LLP2/membrane interactions, we applied synchrotron x-radiation to determine structure of hydrated membranes. We focused on WT LLP2 peptide (+3 charge) and MX2 mutant (-1 charge) with membrane mimics for the T-cell and the HIV-1 membranes. To investigate the influence of electrostatics, cholesterol content, and peptide palmitoylation, we also studied three other LLP2 variants and HIV-1 mimics without negatively charged lipids or cholesterol as well as extracted HIV-1 lipids. All LLP2 peptides bound strongly to T-cell membrane mimics, as indicated by changes in membrane structure and bending. In contrast, none of the weakly bound LLP2 variants changed the HIV-1 membrane mimic structure or properties. This correlates well with, and provides a biophysical basis for, previously published results that reported lack of a mutant effect in HIV virion infectivity in contrast to an inhibitory effect in T-cell syncytium formation. It shows that interaction of LLP2 with the T-cell membrane modulates biological function.
Collapse
Affiliation(s)
- Alexander L Boscia
- Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Steckbeck JD, Kuhlmann AS, Montelaro RC. C-terminal tail of human immunodeficiency virus gp41: functionally rich and structurally enigmatic. J Gen Virol 2012; 94:1-19. [PMID: 23079381 PMCID: PMC3542723 DOI: 10.1099/vir.0.046508-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) pandemic is amongst the most important current worldwide public health threats. While much research has been focused on AIDS vaccines that target the surface viral envelope (Env) protein, including gp120 and the gp41 ectodomain, the C-terminal tail (CTT) of gp41 has received relatively little attention. Despite early studies highlighting the immunogenicity of a particular CTT sequence, the CTT has been classically portrayed as a type I membrane protein limited to functioning in Env trafficking and virion incorporation. Recent studies demonstrate, however, that the Env CTT has other important functions. The CTT has been shown to additionally modulate Env ectodomain structure on the cell and virion surface, affect Env reactivity and viral sensitivity to conformation-dependent neutralizing antibodies, and alter cell–cell and virus–cell fusogenicity of Env. This review provides an overview of the Env structure and function with a particular emphasis on the CTT and recent studies that highlight its functionally rich nature.
Collapse
Affiliation(s)
- Jonathan D. Steckbeck
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Anne-Sophie Kuhlmann
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Ronald C. Montelaro
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| |
Collapse
|
31
|
Oates J, Faust B, Attrill H, Harding P, Orwick M, Watts A. The role of cholesterol on the activity and stability of neurotensin receptor 1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2228-33. [DOI: 10.1016/j.bbamem.2012.04.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 03/15/2012] [Accepted: 04/12/2012] [Indexed: 10/28/2022]
|
32
|
Peters J, Onguri V, Nishimoto SK, Marion TN, Byrne GI. The Chlamydia trachomatis CT149 protein exhibits esterase activity in vitro and catalyzes cholesteryl ester hydrolysis when expressed in HeLa cells. Microbes Infect 2012; 14:1196-204. [PMID: 22940277 DOI: 10.1016/j.micinf.2012.07.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 07/26/2012] [Accepted: 07/30/2012] [Indexed: 11/16/2022]
Abstract
Chlamydia, like other intracellular bacteria, are auxotrophic for a variety of essential metabolites and obtain cholesterol and fatty acids from their eukaryotic host cell, however not many Chlamydia-specific enzymes have been identified that are involved in lipid metabolism. In silico analysis of one candidate Chlamydia trachomatis enzyme, annotated as a conserved putative hydrolase (CT149), identified two lipase/esterase GXSXG motifs, and a potential cholesterol recognition/interaction amino acid consensus (CRAC) sequence. His-tag purified recombinant CT149 exhibited ester hydrolysis activity in a nitrophenyl acetate-based cell-free assay system. When cholesteryl linoleate was used as substrate, ester hydrolysis occurred and production of cholesterol was detected by high performance liquid chromatography. Exogenous expression of transfected CT149 in HeLa cells resulted in a significant decrease of cytoplasmic cholesteryl esters within 48 h. These results demonstrate that CT149 has cholesterol esterase activity and is likely to contribute to the hydrolysis of eukaryotic cholesteryl esters during intracellular chlamydial growth.
Collapse
Affiliation(s)
- Jan Peters
- Department of Microbiology, Immunology & Biochemistry, University of Tennessee Health Science Center, 901 Monroe Ave, Memphis, TN 38163, USA
| | | | | | | | | |
Collapse
|
33
|
Heberle FA, Pan J, Standaert RF, Drazba P, Kučerka N, Katsaras J. Model-based approaches for the determination of lipid bilayer structure from small-angle neutron and X-ray scattering data. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 41:875-90. [PMID: 22588484 DOI: 10.1007/s00249-012-0817-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 03/29/2012] [Accepted: 04/15/2012] [Indexed: 10/28/2022]
Abstract
Some of our recent work has resulted in the detailed structures of fully hydrated, fluid phase phosphatidylcholine (PC) and phosphatidylglycerol (PG) bilayers. These structures were obtained from the joint refinement of small-angle neutron and X-ray data using the scattering density profile (SDP) models developed by Kučerka et al. (Biophys J 95:2356-2367, 2008; J Phys Chem B 116:232-239, 2012). In this review, we first discuss models for the standalone analysis of neutron or X-ray scattering data from bilayers, and assess the strengths and weaknesses inherent to these models. In particular, it is recognized that standalone data do not contain enough information to fully resolve the structure of naturally disordered fluid bilayers, and therefore may not provide a robust determination of bilayer structure parameters, including the much-sought-after area per lipid. We then discuss the development of matter density-based models (including the SDP model) that allow for the joint refinement of different contrast neutron and X-ray data, as well as the implementation of local volume conservation within the unit cell (i.e., ideal packing). Such models provide natural definitions of bilayer thicknesses (most importantly the hydrophobic and Luzzati thicknesses) in terms of Gibbs dividing surfaces, and thus allow for the robust determination of lipid areas through equivalent slab relationships between bilayer thickness and lipid volume. In the final section of this review, we discuss some of the significant findings/features pertaining to structures of PC and PG bilayers as determined from SDP model analyses.
Collapse
Affiliation(s)
- Frederick A Heberle
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6100, USA.
| | | | | | | | | | | |
Collapse
|
34
|
Membrane-proximal external HIV-1 gp41 motif adapted for destabilizing the highly rigid viral envelope. Biophys J 2011; 101:2426-35. [PMID: 22098741 DOI: 10.1016/j.bpj.2011.10.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 10/08/2011] [Accepted: 10/12/2011] [Indexed: 11/20/2022] Open
Abstract
Electron microscopy structural determinations suggest that the membrane-proximal external region (MPER) of glycoprotein 41 (gp41) may associate with the HIV-1 membrane interface. It is further proposed that MPER-induced disruption and/or deformation of the lipid bilayer ensue during viral fusion. However, it is predicted that the cholesterol content of this membrane (∼45 mol %) will act against MPER binding and restructuring activity, in agreement with alternative structural models proposing that the MPER constitutes a gp41 ectodomain component that does not insert into the viral membrane. Here, using MPER-based peptides, we test the hypothesis that cholesterol impedes the membrane association and destabilizing activities of this gp41 domain. To that end, partitioning and leakage assays carried out in lipid vesicles were combined with x-ray reflectivity and grazing-incidence diffraction studies of monolayers. CpreTM, a peptide combining the carboxyterminal MPER sequence with aminoterminal residues of the transmembrane domain, bound and destabilized effectively cholesterol-enriched membranes. Accordingly, virion incubation with this peptide inhibited cell infection potently but nonspecifically. Thus, CpreTM seems to mimic the envelope-perturbing function of the MPER domain and displays antiviral activity. As such, we infer that CpreTM bound to cholesterol-enriched membranes would represent a relevant target for anti-HIV-1 immunogen and inhibitor development.
Collapse
|
35
|
Gallová J, Uhríková D, Kučerka N, Svorková M, Funari SS, Murugova TN, Almásy L, Mazúr M, Balgavý P. Influence of cholesterol and β-sitosterol on the structure of EYPC bilayers. J Membr Biol 2011; 243:1-13. [PMID: 21814861 DOI: 10.1007/s00232-011-9387-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 07/13/2011] [Indexed: 11/28/2022]
Abstract
The influence of cholesterol and β-sitosterol on egg yolk phosphatidylcholine (EYPC) bilayers is compared. Different interactions of these sterols with EYPC bilayers were observed using X-ray diffraction. Cholesterol was miscible with EYPC in the studied concentration range (0-50 mol%), but crystallization of β-sitosterol in EYPC bilayers was observed at X ≥ 41 mol% as detected by X-ray diffraction. Moreover, the repeat distance (d) of the lamellar phase was similar upon addition of the two sterols up to mole fraction 17%, while for X ≥ 17 mol% it became higher in the presence of β-sitosterol compared to cholesterol. SANS data on suspensions of unilamellar vesicles showed that both cholesterol and β-sitosterol similarly increase the EYPC bilayer thickness. Cholesterol in amounts above 33 mol% decreased the interlamellar water layer thickness, probably due to "stiffening" of the bilayer. This effect was not manifested by β-sitosterol, in particular due to the lower solubility of β-sitosterol in EYPC bilayers. Applying the formalism of partial molecular areas, it is shown that the condensing effect of both sterols on the EYPC area at the lipid-water interface is small, if any. The parameters of ESR spectra of spin labels localized in different regions of the EYPC bilayer did not reveal any differences between the effects of cholesterol and β-sitosterol in the range of full miscibility.
Collapse
Affiliation(s)
- Jana Gallová
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University, Odbojárov 10, 832 32 Bratislava, Slovakia.
| | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Stewart SM, Wu WH, Lalime EN, Pekosz A. The cholesterol recognition/interaction amino acid consensus motif of the influenza A virus M2 protein is not required for virus replication but contributes to virulence. Virology 2010; 405:530-8. [PMID: 20655564 PMCID: PMC2923277 DOI: 10.1016/j.virol.2010.06.035] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 08/27/2009] [Accepted: 06/18/2010] [Indexed: 12/21/2022]
Abstract
Influenza A virus particles assemble and bud from plasma membrane domains enriched with the viral glycoproteins but only a small fraction of the total M2 protein is incorporated into virus particles when compared to the other viral glycoproteins. A membrane proximal cholesterol recognition/interaction amino acid consensus (CRAC) motif was previously identified in M2 and suggested to play a role in protein function. We investigated the importance of the CRAC motif on virus replication by generating recombinant proteins and viruses containing amino acid substitutions in this motif. Alteration or completion of the M2 CRAC motif in two different virus strains caused no changes in virus replication in vitro. Viruses lacking an M2 CRAC motif had decreased morbidity and mortality in the mouse model of infection, suggesting that this motif is a virulence determinant which may facilitate virus replication in vivo but is not required for basic virus replication in tissue culture.
Collapse
Affiliation(s)
- Shaun M Stewart
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe St Suite 5132, Baltimore MD 21205
- Division of Biology and Biomedical Sciences, Washington University in St. Louis, Campus Box 8226, 660 South Euclid St, St. Louis, MO 63110
| | - Wai-Hong Wu
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe St Suite 5132, Baltimore MD 21205
| | - Erin N Lalime
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe St Suite 5132, Baltimore MD 21205
| | - Andrew Pekosz
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe St Suite 5132, Baltimore MD 21205
| |
Collapse
|
37
|
Marsh D. Molecular volumes of phospholipids and glycolipids in membranes. Chem Phys Lipids 2010; 163:667-77. [DOI: 10.1016/j.chemphyslip.2010.06.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 06/17/2010] [Accepted: 06/17/2010] [Indexed: 12/17/2022]
|
38
|
Mannock DA, Lewis RN, McMullen TP, McElhaney RN. The effect of variations in phospholipid and sterol structure on the nature of lipid–sterol interactions in lipid bilayer model membranes. Chem Phys Lipids 2010; 163:403-48. [DOI: 10.1016/j.chemphyslip.2010.03.011] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 03/13/2010] [Accepted: 03/27/2010] [Indexed: 01/30/2023]
|
39
|
Abstract
Up to now less than a handful of viral cholesterol-binding proteins have been characterized, in HIV, influenza virus and Semliki Forest virus. These are proteins with roles in virus entry or morphogenesis. In the case of the HIV fusion protein gp41 cholesterol binding is attributed to a cholesterol recognition consensus (CRAC) motif in a flexible domain of the ectodomain preceding the trans-membrane segment. This specific CRAC sequence mediates gp41 binding to a cholesterol affinity column. Mutations in this motif arrest virus fusion at the hemifusion stage and modify the ability of the isolated CRAC peptide to induce segregation of cholesterol in artificial membranes.Influenza A virus M2 protein co-purifies with cholesterol. Its proton translocation activity, responsible for virus uncoating, is not cholesterol-dependent, and the transmembrane channel appears too short for integral raft insertion. Cholesterol binding may be mediated by CRAC motifs in the flexible post-TM domain, which harbours three determinants of binding to membrane rafts. Mutation of the CRAC motif of the WSN strain attenuates virulence for mice. Its affinity to the raft-non-raft interface is predicted to target M2 protein to the periphery of lipid raft microdomains, the sites of virus assembly. Its influence on the morphology of budding virus implicates M2 as factor in virus fission at the raft boundary. Moreover, M2 is an essential factor in sorting the segmented genome into virus particles, indicating that M2 also has a role in priming the outgrowth of virus buds.SFV E1 protein is the first viral type-II fusion protein demonstrated to directly bind cholesterol when the fusion peptide loop locks into the target membrane. Cholesterol binding is modulated by another, proximal loop, which is also important during virus budding and as a host range determinant, as shown by mutational studies.
Collapse
Affiliation(s)
- Cornelia Schroeder
- Max Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, D-01307, Dresden, Germany.
| |
Collapse
|
40
|
The oxidized form of cholesterol 3β-hydroxy-5-oxo-5,6-secocholestan-6-al induces structural and thermotropic changes in phospholipid membranes. Chem Phys Lipids 2009; 161:95-102. [DOI: 10.1016/j.chemphyslip.2009.07.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2009] [Accepted: 07/26/2009] [Indexed: 11/17/2022]
|
41
|
Pan J, Tristram-Nagle S, Nagle JF. Effect of cholesterol on structural and mechanical properties of membranes depends on lipid chain saturation. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:021931. [PMID: 19792175 PMCID: PMC2756665 DOI: 10.1103/physreve.80.021931] [Citation(s) in RCA: 252] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Indexed: 05/10/2023]
Abstract
The effects of cholesterol on membrane bending modulus K(C), membrane thickness D(HH), the partial and apparent areas of cholesterol and lipid, and the order parameter S(xray) are shown to depend upon the number of saturated hydrocarbon chains in the lipid molecules. Particularly striking is the result that up to 40% cholesterol does not increase the bending modulus K(C) of membranes composed of phosphatidylcholine lipids with two cis monounsaturated chains, although it does have the expected stiffening effect on membranes composed of lipids with two saturated chains. The B fluctuational modulus in the smectic liquid crystal theory is obtained and used to discuss the interactions between bilayers. Our K(C) results motivate a theory of elastic moduli in the high cholesterol limit and they challenge the relevance of universality concepts. Although most of our results were obtained at 30 degrees C , additional data at other temperatures to allow consideration of a reduced temperature variable do not support universality for the effect of cholesterol on all lipid bilayers. If the concept of universality is to be valid, different numbers of saturated chains must be considered to create different universality classes. The above experimental results were obtained from analysis of x-ray scattering in the low angle and wide angle regions.
Collapse
Affiliation(s)
- Jianjun Pan
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | | | | |
Collapse
|
42
|
Lee DK, Kwon BS, Ramamoorthy A. Freezing point depression of water in phospholipid membranes: a solid-state NMR study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:13598-13604. [PMID: 18991419 PMCID: PMC2649677 DOI: 10.1021/la8023698] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Lipid-water interaction plays an important role in the properties of lipid bilayers, cryoprotectants, and membrane-associated peptides and proteins. The temperature at which water bound to lipid bilayers freezes is lower than that of free water. Here, we report a solid-state NMR investigation on the freezing point depression of water in phospholipid bilayers in the presence and absence of cholesterol. Deuterium NMR spectra at different temperatures ranging from -75 to + 10 degrees C were obtained from fully (2)H2O-hydrated POPC (1-palmitoyl-2-oleoylphosphatidylcholine) multilamellar vesicles (MLVs), prepared with and without cholesterol, to determine the freezing temperature of water and the effect of cholesterol on the freezing temperature of water in POPC bilayers. Our 2H NMR experiments reveal the motional behavior of unfrozen water molecules in POPC bilayers even at temperatures significantly below 0 degrees C and show that the presence of cholesterol further lowered the freezing temperature of water in POPC bilayers. These results suggest that in the presence of cholesterol the fluidity and dynamics of lipid bilayers can be retained even at very low temperatures as exist in the liquid crystalline phase of the lipid. Therefore, bilayer samples prepared with a cryoprotectant like cholesterol should enable the performance of multidimensional solid-state NMR experiments to investigate the structure, dynamics, and topology of membrane proteins at a very low temperature with enhanced sample stability and possibly a better sensitivity. Phosphorus-31 NMR data suggest that lipid bilayers can be aligned at low temperatures, while 15N NMR experiments demonstrate that such aligned samples can be used to enhance the signal-to-noise ratio of is 15N chemical shift spectra of a 37-residue human antimicrobial peptide, LL-37.
Collapse
Affiliation(s)
- Dong-Kuk Lee
- Department of Fine Chemistry, Seoul National University of Technology, Seoul 139-743, Korea.
| | | | | |
Collapse
|
43
|
Bremer CM, Bung C, Kott N, Hardt M, Glebe D. Hepatitis B virus infection is dependent on cholesterol in the viral envelope. Cell Microbiol 2008; 11:249-60. [PMID: 19016777 DOI: 10.1111/j.1462-5822.2008.01250.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The viral and cellular determinants leading to binding and entry of hepatitis B virus (HBV) are still not fully understood. We found that HBV infection of primary hepatocyte cultures is dependent on the presence of cholesterol in the viral envelope. Extraction of cholesterol from HBV purified from plasma of HBV-infected patients with methyl-beta-cyclodextrin (MbetaCD) leads to a strongly reduced level of infection. The cholesterol-depleted virions showed higher buoyant density (1.23 versus 1.17 g ml(-1)), a smaller diameter (39 versus 48 nm), but maintained particle integrity, antigenicity and ability to bind to hepatocytes. Although addition of exogenous cholesterol and cholesterol analogues restored the physical appearance of cholesterol-depleted virions, infectivity was only regained by cholesterol add-back. Infectivity of HBV produced from cell culture in the presence of inhibitors of cholesterol-synthesis is severely impaired. Interestingly, cholesterol extraction from cellular membranes, incubation with filipin and the protein tyrosine kinase inhibitor genistein showed no effect on HBV infection, excluding a role of lipid rafts for the infection process of HBV. In summary, presence of cholesterol within the viral envelope is not important for viral binding, but indispensable for the entry process of HBV and might be important for a later step in viral uptake, e.g. fusion in a yet unknown compartment.
Collapse
Affiliation(s)
- Corinna M Bremer
- Institute of Medical Virology, Justus Liebig University, Frankfurter Str. 107, 35392, Giessen, Germany
| | | | | | | | | |
Collapse
|
44
|
Vishwanathan SA, Thomas A, Brasseur R, Epand RF, Hunter E, Epand RM. Large changes in the CRAC segment of gp41 of HIV do not destroy fusion activity if the segment interacts with cholesterol. Biochemistry 2008; 47:11869-76. [PMID: 18937430 DOI: 10.1021/bi8014828] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The membrane-proximal external region (MPER) of the gp41 fusion protein of HIV is highly conserved among isolates of this virus and is considered a target for vaccine development. This region also appears to play a role in membrane fusion as well as localization of the virus to cholesterol-rich domains in membranes. The carboxyl terminus of MPER has the sequence LWYIK and appears to have an important role in cholesterol interactions. We have tested how amino acid substitutions that would affect the conformational flexibility of this segment could alter its interaction with cholesterol. We studied a family of peptides (all peptides as N-acetyl-peptide amides) with P, G, or A substituting for W and I of the LWYIK sequence. The peptide having the greatest effect on cholesterol distribution in membranes was the most flexible one, LGYGK. The corresponding mutation in gp41 resulted in a protein retaining 72% of the fusion activity of the wild-type protein. Two other peptides were synthesized, also containing two Gly residues, GWGIK and LWGIG, and did not have the ability to sequester cholesterol as efficiently as LGYGK did. Making the corresponding mutants of gp41 showed that these other two double Gly substitutions resulted in proteins that were much less fusogenic, although they were equally well expressed at the cell surface. The study demonstrates that drastic changes can be made in the LWYIK segment with the retention of a significant fraction of the fusogenic activity, as long as the mutant proteins interact with cholesterol.
Collapse
Affiliation(s)
- Sundaram A Vishwanathan
- Emory Vaccine Research Center, Yerkes, Emory University, 954 Gatewood Road, Atlanta, Georgia 30329, USA
| | | | | | | | | | | |
Collapse
|