1
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Kashnik AS, Baranov DS, Dzuba SA. Spatial Arrangement of the Drug Ibuprofen in a Model Membrane in the Presence of Lipid Rafts. J Phys Chem B 2024; 128:3652-3661. [PMID: 38576273 DOI: 10.1021/acs.jpcb.4c01507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
Many pharmaceutical drugs are known to interact with lipid membranes through nonspecific molecular interactions, which affect their therapeutic effect. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) and one of the most commonly prescribed. In the presence of cholesterol, lipid bilayers can separate into nanoscale liquid-disordered and liquid-ordered structures, the latter known as lipid rafts. Here, we study spin-labeled ibuprofen (ibuprofen-SL) in the model membrane consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol in the molar ratio of (0.5-0.5xchol)/(0.5-0.5xchol)/xchol. Electron paramagnetic resonance (EPR) spectroscopy is employed, along with its pulsed version of double electron-electron resonance (DEER, also known as PELDOR). The data obtained indicate lateral lipid-mediated clustering of ibuprofen-SL molecules with a local surface density noticeably larger than that expected for random lateral distribution. In the absence of cholesterol, the data can be interpreted as indicating alternating clustering in two opposing leaflets of the bilayer. In the presence of cholesterol, for xchol ≥ 20 mol %, the results show that ibuprofen-SL molecules have a quasi-regular lateral distribution, with a "superlattice" parameter of ∼3.0 nm. This regularity can be explained by the entrapment of ibuprofen-SL molecules by lipid rafts known to exist in this system with the additional assumption that lipid rafts have a nanoscale substructure.
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Affiliation(s)
- Anna S Kashnik
- Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Denis S Baranov
- Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Sergei A Dzuba
- Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
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2
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Simeral ML, Demers SME, Sheth K, Hafner JH. A Raman spectral marker for the iso-octyl chain structure of cholesterol. ANALYTICAL SCIENCE ADVANCES 2024; 5:2300057. [PMID: 38828085 PMCID: PMC11142391 DOI: 10.1002/ansa.202300057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2023] [Accepted: 11/17/2023] [Indexed: 06/05/2024]
Abstract
Raman spectroscopy provides label-free, specific analysis of biomolecular structure and interactions. It could have a greater impact with improved characterization of complex fingerprint vibrations. Many Raman peaks have been assigned to cholesterol, for example, but the molecular vibrations associated with those peaks are not known. In this report, time-dependent density functional theory calculations of the Raman spectrum of cholesterol are compared to measurements on microcrystalline powder to identify 23 peaks in the Raman spectrum. Among them, a band of six peaks is found to be sensitive to the conformational structure of cholesterol's iso-octyl chain. Calculations on 10 conformers in this spectral band are fit to experimental spectra to probe the cholesterol chain structure in purified powder and in phospholipid vesicles. In vesicles, the chain is found to bend perpendicular to the steroid rings, supporting the case that the chain is a dynamic structure that contributes to lipid condensation and other effects of cholesterol in biomembranes. Statement of Significance: Here we use density functional theory to identify a band of six peaks in cholesterol's Raman spectrum that is sensitive to the conformational structure of cholesterol's chain. Raman spectra were analyzed to show that in fluid-phase lipid membranes, about half of the cholesterol chains point perpendicular to the steroid rings. This new method of label-free structural analysis could make significant contributions to our understanding of cholesterol's critical role in biomembrane structure and function. More broadly, the results show that computational quantum chemistry Raman spectroscopy can make significant new contributions to molecular structure when spectra are interpreted with computational quantum chemistry.
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Affiliation(s)
| | | | - Kyle Sheth
- Department of Physics and AstronomyRice UniversityHoustonTexasUSA
| | - Jason H. Hafner
- Department of Physics and AstronomyRice UniversityHoustonTexasUSA
- Department of ChemistryRice UniversityHoustonTexasUSA
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3
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Della Ripa LA, Courtney JM, Phinney SM, Borcik CG, Burke MD, Rienstra CM, Pogorelov TV. Segmental Dynamics of Membranous Cholesterol are Coupled. J Am Chem Soc 2023; 145:15043-15048. [PMID: 37410392 PMCID: PMC10638920 DOI: 10.1021/jacs.3c01775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/07/2023]
Abstract
Cholesterol promotes the structural integrity of the fluid cell membrane and interacts dynamically with many membrane proteins to regulate function. Understanding site-resolved cholesterol structural dynamics is thus important. This long-standing challenge has thus far been addressed, in part, by selective isotopic labeling approaches. Here we present a new 3D solid-state NMR (SSNMR) experiment utilizing scalar 13C-13C polarization transfer and recoupling of the 1H-13C interactions in order to determine average dipolar couplings for all 1H-13C vectors in uniformly 13C-enriched cholesterol. The experimentally determined order parameters (OP) agree exceptionally well with molecular dynamics (MD) trajectories and reveal coupling among several conformational degrees of freedom in cholesterol molecules. Quantum chemistry shielding calculations further support this conclusion and specifically demonstrate that ring tilt and rotation are coupled to changes in tail conformation and that these coupled segmental dynamics dictate the orientation of cholesterol. These findings advance our understanding of physiologically relevant dynamics of cholesterol, and the methods that revealed them have broader potential to characterize how structural dynamics of other small molecules impact their biological functions.
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4
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van Aalst EJ, McDonald CJ, Wylie BJ. Cholesterol Biases the Conformational Landscape of the Chemokine Receptor CCR3: A MAS SSNMR-Filtered Molecular Dynamics Study. J Chem Inf Model 2023; 63:3068-3085. [PMID: 37127541 PMCID: PMC10208230 DOI: 10.1021/acs.jcim.2c01546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Indexed: 05/03/2023]
Abstract
Cholesterol directs the pathway of ligand-induced G protein-coupled receptor (GPCR) signal transduction. The GPCR C-C motif chemokine receptor 3 (CCR3) is the principal chemotactic receptor for eosinophils, with roles in cancer metastasis and autoinflammatory conditions. Recently, we discovered a direct correlation between bilayer cholesterol and increased agonist-triggered CCR3 signal transduction. However, the allosteric molecular mechanism escalating ligand affinity and G protein coupling is unknown. To study cholesterol-guided CCR3 conformational selection, we implement comparative, objective measurement of protein architectures by scoring shifts (COMPASS) to grade model structures from molecular dynamics simulations. In this workflow, we scored predicted chemical shifts against 2-dimensional solid-state NMR 13C-13C correlation spectra of U-15N,13C-CCR3 samples prepared with and without cholesterol. Our analysis of trajectory model structures uncovers that cholesterol induces site-specific conformational restraint of extracellular loop (ECL) 2 and conserved motion in transmembrane helices and ECL3 not observed in simulations of bilayers with only phosphatidylcholine lipids. PyLipID analysis implicates direct cholesterol agency in CCR3 conformational selection and dynamics. Residue-residue contact scoring shows that cholesterol biases the conformational selection of the orthosteric pocket involving Y411.39, Y1133.32, and E2877.39. Lastly, we observe contact remodeling in activation pathway residues centered on the initial transmission switch, Na+ pocket, and R3.50 in the DRY motif. Our observations have unique implications for understanding of CCR3 ligand recognition and specificity and provide mechanistic insight into how cholesterol functions as an allosteric regulator of CCR3 signal transduction.
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Affiliation(s)
- Evan J. van Aalst
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock, Texas 79415, United States
| | - Corey J. McDonald
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock, Texas 79415, United States
| | - Benjamin J. Wylie
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock, Texas 79415, United States
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5
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Bach D, Wachtel E. Cholesterol solubility in mixed DMPE/DMPC bilayers as determined by small angle X-ray scattering. Biophys Chem 2023; 297:107014. [PMID: 37027969 DOI: 10.1016/j.bpc.2023.107014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 03/30/2023] [Accepted: 03/30/2023] [Indexed: 04/03/2023]
Abstract
Small angle X-ray scattering measurements under ambient conditions (T ≈ 294 K) provide evidence for the formation of separate domains in a ternary, mixed phospholipid ([DMPE]/[DMPC] = 3/1) / cholesterol model bilayer membrane. As we interpret these results, the domains contain cholesterol and DMPC, with which cholesterol is known to preferentially interact in a binary model membrane (solubility limit, mol fraction cholesterol 0.5), as compared to DMPE (solubility limit, mol fraction cholesterol 0.45). The solubility limit for the ternary system is mol fraction cholesterol 0.2-0.3. Although literature EPR spectra find that non-crystalline, cholesterol bilayer domains may be present even prior to the observation of cholesterol crystal diffraction, X-ray scattering cannot detect their presence.
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Affiliation(s)
- Diana Bach
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Ellen Wachtel
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel.
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6
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Trollmann MFW, Böckmann RA. mRNA lipid nanoparticle phase transition. Biophys J 2022; 121:3927-3939. [PMID: 36045573 PMCID: PMC9674992 DOI: 10.1016/j.bpj.2022.08.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 08/06/2022] [Accepted: 08/25/2022] [Indexed: 11/28/2022] Open
Abstract
Crucial for mRNA-based vaccines are the composition, structure, and properties of lipid nanoparticles (LNPs) as their delivery vehicle. Using all-atom molecular dynamics simulations as a computational microscope, we provide an atomistic view of the structure of the Comirnaty vaccine LNP, its molecular organization, physicochemical properties, and insight in its pH-driven phase transition enabling mRNA release at atomistic resolution. At physiological pH, our simulations suggest an oil-like LNP core that is composed of the aminolipid ALC-0315 and cholesterol (ratio 72:28). It is surrounded by a lipid monolayer formed by distearoylphosphatidylcholine, ALC-0315, PEGylated lipids, and cholesterol at a ratio of 22:9:6:63. Protonated aminolipids enveloping mRNA formed inverted micellar structures that provide a shielding and likely protection from environmental factors. In contrast, at low pH, the Comirnaty lipid composition instead spontaneously formed lipid bilayers that display a high degree of elasticity. These pH-dependent lipid phases suggest that a change in pH of the environment upon LNP transfer to the endosome likely acts as trigger for cargo release from the LNP core by turning aminolipids inside out, thereby destabilizing both the LNP shell and the endosomal membrane.
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Affiliation(s)
- Marius F W Trollmann
- Computational Biology, Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany; Erlangen National Center for High-Performance Computing (NHR@FAU), Erlangen, Germany
| | - Rainer A Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany; Erlangen National Center for High-Performance Computing (NHR@FAU), Erlangen, Germany.
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7
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Li Y, Feng R, Liu M, Guo Y, Zhang Z. Mechanism by Which Cholesterol Induces Sphingomyelin Conformational Changes at an Air/Water Interface. J Phys Chem B 2022; 126:5481-5489. [PMID: 35839485 DOI: 10.1021/acs.jpcb.2c03127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work investigates the interactions in cholesterol and sphingomyelin monolayers at the molecular level by high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS). The SFG spectra of natural egg sphingomyelin (ESM) as a function of cholesterol concentration are obtained at an air/water interface under different polarization combinations. The analysis of the spectra shows that cholesterol can induce sphingomyelin conformational changes at an air/water interface. The mechanism is proposed. When cholesterol is inserted into the ESM monolayer, the inherent intramolecular hydrogen bonds between the phosphate moiety and 3OH in the sphingosine backbones are destroyed. During this process, the sphingosine backbones become more ordered, while the conformation of the N-linked long acid chain remains unaltered. The OH of the cholesterol head group can bind to the -PO-2 of the ESM molecule, and the orientation of the -PO-2 in the head groups changes to be more parallel to the interface.
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Affiliation(s)
- Yiyi Li
- Beijing National Laboratory for Molecular Sciences, Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Rongjuan Feng
- Beijing National Laboratory for Molecular Sciences, Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Minghua Liu
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yuan Guo
- Beijing National Laboratory for Molecular Sciences, Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhen Zhang
- Beijing National Laboratory for Molecular Sciences, Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
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8
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Grusky DS, Moss FR, Boxer SG. Recombination between 13C and 2H to Form Acetylide ( 13C 22H -) Probes Nanoscale Interactions in Lipid Bilayers via Dynamic Secondary Ion Mass Spectrometry: Cholesterol and GM 1 Clustering. Anal Chem 2022; 94:9750-9757. [PMID: 35759338 PMCID: PMC10075087 DOI: 10.1021/acs.analchem.2c01336] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although it is thought that there is lateral heterogeneity of lipid and protein components within biological membranes, probing this heterogeneity has proven challenging. The difficulty in such experiments is due to both the small length scale over which such heterogeneity can occur, and the significant perturbation resulting from fluorescent or spin labeling on the delicate interactions within bilayers. Atomic recombination during dynamic nanoscale secondary ion imaging mass spectrometry (NanoSIMS) is a non-perturbative method for examining nanoscale bilayer interactions. Atomic recombination is a variation on conventional NanoSIMS imaging, whereby an isotope on one molecule combines with a different isotope on another molecule during the ionization process, forming an isotopically enriched polyatomic ion in a distance-dependent manner. We show that the recombinant ion, 13C22H-, is formed in high yield from 13C- and 2H-labeled lipids. The low natural abundance of triply labeled acetylide also makes it an ideal ion to probe GM1 clusters in model membranes and the effects of cholesterol on lipid-lipid interactions. We find evidence supporting the cholesterol condensation effect as well as the presence of nanoscale GM1 clusters in model membranes.
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Affiliation(s)
- Dashiel S Grusky
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Frank R Moss
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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9
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Sutherland M, Tran N, Hong M. Clustering of tetrameric influenza M2 peptides in lipid bilayers investigated by 19F solid-state NMR. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183909. [PMID: 35276226 DOI: 10.1016/j.bbamem.2022.183909] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 02/08/2022] [Accepted: 03/05/2022] [Indexed: 11/19/2022]
Abstract
The influenza M2 protein forms a drug-targeted tetrameric proton channel to mediate virus uncoating, and carries out membrane scission to enable virus release. While the proton channel function of M2 has been extensively studied, the mechanism by which M2 catalyzes membrane scission is still not well understood. Previous fluorescence and electron microscopy studies indicated that M2 tetramers concentrate at the neck of the budding virus in the host plasma membrane. However, molecular evidence for this clustering is scarce. Here, we use 19F solid-state NMR to investigate M2 clustering in phospholipid bilayers. By mixing equimolar amounts of 4F-Phe47 labeled M2 peptide and CF3-Phe47 labeled M2 peptide and measuring F-CF3 cross peaks in 2D 19F19F correlation spectra, we show that M2 tetramers form nanometer-scale clusters in lipid bilayers. This clustering is stronger in cholesterol-containing membranes and phosphatidylethanolamine (PE) membranes than in cholesterol-free phosphatidylcholine and phosphatidylglycerol membranes. The observed correlation peaks indicate that Phe47 sidechains from different tetramers are less than ~2 nm apart. 1H19F correlation peaks between lipid chain protons and fluorinated Phe47 indicate that Phe47 is more deeply inserted into the lipid bilayer in the presence of cholesterol than in its absence, suggesting that Phe47 preferentially interacts with cholesterol. Static 31P NMR spectra indicate that M2 induces negative Gaussian curvature in the PE membrane. These results suggest that M2 tetramers cluster at cholesterol- and PE-rich regions of cell membranes to cause membrane curvature, which in turn can facilitate membrane scission in the last step of virus budding and release.
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Affiliation(s)
- Madeleine Sutherland
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States of America
| | - Nhi Tran
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States of America
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States of America.
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10
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Borcik C, Eason IR, Vanderloop B, Wylie BJ. 2H, 13C-Cholesterol for Dynamics and Structural Studies of Biological Membranes. ACS OMEGA 2022; 7:17151-17160. [PMID: 35647452 PMCID: PMC9134247 DOI: 10.1021/acsomega.2c00796] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 04/08/2022] [Indexed: 05/19/2023]
Abstract
We present a cost-effective means of 2H and 13C enrichment of cholesterol. This method exploits the metabolism of 2H,13C-acetate into acetyl-CoA, the first substrate in the mevalonate pathway. We show that growing the cholesterol producing strain RH6827 of Saccharomyces cerevisiae in 2H,13C-acetate-enriched minimal media produces a skip-labeled pattern of deuteration. We characterize this cholesterol labeling pattern by mass spectrometry and solid-state nuclear magnetic resonance spectroscopy. It is confirmed that most 2H nuclei retain their original 2H-13C bonds from acetate throughout the biosynthetic pathway. We then quantify the changes in 13C chemical shifts brought by deuteration and the impact upon 13C-13C spin diffusion. Finally, using adiabatic rotor echo short pulse irradiation cross-polarization (RESPIRATIONCP), we acquire the 2H-13C correlation spectra to site specifically quantify cholesterol dynamics in two model membranes as a function of temperature. These measurements show that cholesterol acyl chains at physiological temperatures in mixtures of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), sphingomyelin, and cholesterol are more dynamic than cholesterol in POPC. However, this overall change in motion is not uniform across the cholesterol molecule. This result establishes that this cholesterol labeling pattern will have great utility in reporting on cholesterol dynamics and orientation in a variety of environments and with different membrane bilayer components, as well as monitoring the mevalonate pathway product interactions within the bilayer. Finally, the flexibility and universality of acetate labeling will allow this technique to be widely applied to a large range of lipids and other natural products.
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11
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Barbera N, Granados ST, Vanoye CG, Abramova TV, Kulbak D, Ahn SJ, George AL, Akpa BS, Levitan I. Cholesterol-induced suppression of Kir2 channels is mediated by decoupling at the inter-subunit interfaces. iScience 2022; 25:104329. [PMID: 35602957 PMCID: PMC9120057 DOI: 10.1016/j.isci.2022.104329] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/29/2022] [Accepted: 04/26/2022] [Indexed: 12/29/2022] Open
Abstract
Cholesterol is a major regulator of multiple types of ion channels. Although there is increasing information about cholesterol binding sites, the molecular mechanisms through which cholesterol binding alters channel function are virtually unknown. In this study, we used a combination of Martini coarse-grained simulations, a network theory-based analysis, and electrophysiology to determine the effect of cholesterol on the dynamic structure of the Kir2.2 channel. We found that increasing membrane cholesterol reduced the likelihood of contact between specific regions of the cytoplasmic and transmembrane domains of the channel, most prominently at the subunit-subunit interfaces of the cytosolic domains. This decrease in contact was mediated by pairwise interactions of specific residues and correlated to the stoichiometry of cholesterol binding events. The predictions of the model were tested by site-directed mutagenesis of two identified residues-V265 and H222-and high throughput electrophysiology.
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Affiliation(s)
- Nicolas Barbera
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Sara T. Granados
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Carlos Guillermo Vanoye
- Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Tatiana V. Abramova
- Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Danielle Kulbak
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Sang Joon Ahn
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Alfred L. George
- Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Belinda S. Akpa
- Division of Biosciences, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA
- Molecular Biomedical Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Irena Levitan
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
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12
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Medeiros-Silva J, Somberg NH, Wang HK, McKay MJ, Mandala VS, Dregni AJ, Hong M. pH- and Calcium-Dependent Aromatic Network in the SARS-CoV-2 Envelope Protein. J Am Chem Soc 2022; 144:6839-6850. [PMID: 35380805 DOI: 10.1021/jacs.2c00973] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The envelope (E) protein of the SARS-CoV-2 virus is a membrane-bound viroporin that conducts cations across the endoplasmic reticulum Golgi intermediate compartment (ERGIC) membrane of the host cell to cause virus pathogenicity. The structure of the closed state of the E transmembrane (TM) domain, ETM, was recently determined using solid-state NMR spectroscopy. However, how the channel pore opens to mediate cation transport is unclear. Here, we use 13C and 19F solid-state NMR spectroscopy to investigate the conformation and dynamics of ETM at acidic pH and in the presence of calcium ions, which mimic the ERGIC and lysosomal environment experienced by the E protein in the cell. Acidic pH and calcium ions increased the conformational disorder of the N- and C-terminal residues and also increased the water accessibility of the protein, indicating that the pore lumen has become more spacious. ETM contains three regularly spaced phenylalanine (Phe) residues in the center of the peptide. 19F NMR spectra of para-fluorinated Phe20 and Phe26 indicate that both residues exhibit two sidechain conformations, which coexist within each channel. These two Phe conformations differ in their water accessibility, lipid contact, and dynamics. Channel opening by acidic pH and Ca2+ increases the population of the dynamic lipid-facing conformation. These results suggest an intricate aromatic network that regulates the opening of the ETM channel pore. This aromatic network may be a target for E inhibitors against SARS-CoV-2 and related coronaviruses.
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Affiliation(s)
- João Medeiros-Silva
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Noah H Somberg
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Harrison K Wang
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Matthew J McKay
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Venkata S Mandala
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Aurelio J Dregni
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
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13
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Frallicciardi J, Melcr J, Siginou P, Marrink SJ, Poolman B. Membrane thickness, lipid phase and sterol type are determining factors in the permeability of membranes to small solutes. Nat Commun 2022; 13:1605. [PMID: 35338137 PMCID: PMC8956743 DOI: 10.1038/s41467-022-29272-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 03/02/2022] [Indexed: 12/16/2022] Open
Abstract
Cell membranes provide a selective semi-permeable barrier to the passive transport of molecules. This property differs greatly between organisms. While the cytoplasmic membrane of bacterial cells is highly permeable for weak acids and glycerol, yeasts can maintain large concentration gradients. Here we show that such differences can arise from the physical state of the plasma membrane. By combining stopped-flow kinetic measurements with molecular dynamics simulations, we performed a systematic analysis of the permeability of a variety of small molecules through synthetic membranes of different lipid composition to obtain detailed molecular insight into the permeation mechanisms. While membrane thickness is an important parameter for the permeability through fluid membranes, the largest differences occur when the membranes transit from the liquid-disordered to liquid-ordered and/or to gel state, which is in agreement with previous work on passive diffusion of water. By comparing our results with in vivo measurements from yeast, we conclude that the yeast membrane exists in a highly ordered and rigid state, which is comparable to synthetic saturated DPPC-sterol membranes. Membrane permeability of small molecules depends on the composition of the lipid bilayer. Here, authors compare permeability measured on membranes in different physical states and conclude that the yeast membrane exists in a highly ordered phase.
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Affiliation(s)
- Jacopo Frallicciardi
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands
| | - Josef Melcr
- Department of Biophysical Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands
| | - Pareskevi Siginou
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands
| | - Siewert J Marrink
- Department of Biophysical Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands.
| | - Bert Poolman
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands.
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14
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Borcik CG, Eason IR, Yekefallah M, Amani R, Han R, Vanderloop BH, Wylie BJ. A Cholesterol Dimer Stabilizes the Inactivated State of an Inward-Rectifier Potassium Channel. Angew Chem Int Ed Engl 2022; 61:e202112232. [PMID: 34985791 PMCID: PMC8957755 DOI: 10.1002/anie.202112232] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Indexed: 12/15/2022]
Abstract
Cholesterol oligomers reside in multiple membrane protein X-ray crystal structures. Yet, there is no direct link between these oligomers and a biological function. Here we present the structural and functional details of a cholesterol dimer that stabilizes the inactivated state of an inward-rectifier potassium channel KirBac1.1. K+ efflux assays confirm that high cholesterol concentration reduces K+ conductance. We then determine the structure of the cholesterol-KirBac1.1 complex using Xplor-NIH simulated annealing calculations driven by solid-state NMR distance measurements. These calculations identified an α-α cholesterol dimer docked to a cleft formed by adjacent subunits of the homotetrameric protein. We compare these results to coarse grain molecular dynamics simulations. This is one of the first examples of a cholesterol oligomer performing a distinct biological function and structural characterization of a conserved promiscuous lipid binding region.
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Affiliation(s)
- Collin G Borcik
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Isaac R Eason
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Maryam Yekefallah
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Reza Amani
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Ruixian Han
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Boden H Vanderloop
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
| | - Benjamin J Wylie
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
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Borcik CG, Eason IR, Yekefallah M, Amani R, Han R, Vanderloop BH, Wylie BJ. A Cholesterol Dimer Stabilizes the Inactivated State of an Inward‐Rectifier Potassium Channel. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202112232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Collin G. Borcik
- Department of Chemistry and Biochemistry Texas Tech University Lubbock TX 79409 USA
| | - Isaac R. Eason
- Department of Chemistry and Biochemistry Texas Tech University Lubbock TX 79409 USA
| | - Maryam Yekefallah
- Department of Chemistry and Biochemistry Texas Tech University Lubbock TX 79409 USA
| | - Reza Amani
- Department of Chemistry and Biochemistry Texas Tech University Lubbock TX 79409 USA
| | - Ruixian Han
- Department of Biochemistry University of Wisconsin-Madison Madison WI 53706 USA
| | - Boden H. Vanderloop
- Department of Chemistry and Biochemistry Texas Tech University Lubbock TX 79409 USA
| | - Benjamin J. Wylie
- Department of Chemistry and Biochemistry Texas Tech University Lubbock TX 79409 USA
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16
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Pandey S, Xiang Y, Friedrich D, Leng Y, Mao H. Direct Measurement of Intermolecular Mechanical Force for Nonspecific Interactions between Small Molecules. J Phys Chem Lett 2021; 12:11316-11322. [PMID: 34780182 PMCID: PMC8778946 DOI: 10.1021/acs.jpclett.1c03142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Mechanical force can evaluate intramolecular interactions in macromolecules. Because of the rapid motion of small molecules, it is extremely challenging to measure mechanical forces of nonspecific intermolecular interactions. Here, we used optical tweezers to directly examine the intermolecular mechanical force (IMMF) of nonspecific interactions between two cholesterols. We found that IMMFs of dimeric cholesterol complexes were dependent on the orientation of the interaction. The surprisingly high IMMF in cholesterol dimers (∼30 pN) is comparable to the mechanical stability of DNA secondary structures. Using Hess-like cycles, we quantified that changes in free energy of solubilizing cholesterol (ΔGsolubility) by β-cyclodextrin (βCD) and methylated βCD (Me-βCD) were as low as -16 and -27 kcal/mol, respectively. Compared to the ΔGsolubility of cholesterols in water (5.1 kcal/mol), these values indicated that cyclodextrins can easily solubilize cholesterols. Our results demonstrated that the IMMF can serve as a generic and multipurpose variable to dissect nonspecific intermolecular interactions among small molecules into orientational components.
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Affiliation(s)
- Shankar Pandey
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH, 44242, USA
| | - Yuan Xiang
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
| | - Dirk Friedrich
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH, 44242, USA
| | - Yongsheng Leng
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
| | - Hanbin Mao
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH, 44242, USA
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17
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Tran N, Oh Y, Sutherland M, Cui Q, Hong M. Cholesterol-Mediated Clustering of the HIV Fusion Protein gp41 in Lipid Bilayers. J Mol Biol 2021; 434:167345. [PMID: 34762895 DOI: 10.1016/j.jmb.2021.167345] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Revised: 10/26/2021] [Accepted: 10/31/2021] [Indexed: 11/16/2022]
Abstract
The envelope glycoprotein (Env) of the human immunodeficient virus (HIV-1) is known to cluster on the viral membrane surface to attach to target cells and cause membrane fusion for HIV-1 infection. However, the molecular structural mechanisms that drive Env clustering remain opaque. Here, we use solid-state NMR spectroscopy and molecular dynamics (MD) simulations to investigate nanometer-scale clustering of the membrane-proximal external region (MPER) and transmembrane domain (TMD) of gp41, the fusion protein component of Env. Using 19F solid-state NMR experiments of mixed fluorinated peptides, we show that MPER-TMD trimers form clusters with interdigitated MPER helices in cholesterol-containing membranes. Inter-trimer 19F-19F cross peaks, which are indicative of spatial contacts within ∼2 nm, are observed in cholesterol-rich virus-mimetic membranes but are suppressed in cholesterol-free model membranes. Water-peptide and lipid-peptide cross peaks in 2D 1H-19F correlation spectra indicate that the MPER is well embedded in model phosphocholine membranes but is more exposed to the surface of the virus-mimetic membrane. These experimental results are reproduced in coarse-grained and atomistic molecular dynamics simulations, which suggest that the effects of cholesterol on gp41 clustering is likely via indirect modulation of the MPER orientation. Cholesterol binding to the helix-turn-helix region of the MPER-TMD causes a parallel orientation of the MPER with the membrane surface, thus allowing MPERs of neighboring trimers to interact with each other to cause clustering. These solid-state NMR data and molecular dynamics simulations suggest that MPER and cholesterol cooperatively govern the clustering of gp41 trimers during virus-cell membrane fusion.
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Affiliation(s)
- Nhi Tran
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, United States
| | - Younghoon Oh
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, United States
| | - Madeleine Sutherland
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, United States
| | - Qiang Cui
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, United States; Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, United States; Department of Biomedical Engineering, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, United States.
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, United States. https://twitter.com/MeiHongLab
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18
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Shcherbakov AA, Medeiros-Silva J, Tran N, Gelenter MD, Hong M. From Angstroms to Nanometers: Measuring Interatomic Distances by Solid-State NMR. Chem Rev 2021; 122:9848-9879. [PMID: 34694769 DOI: 10.1021/acs.chemrev.1c00662] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Internuclear distances represent one of the main structural constraints in molecular structure determination using solid-state NMR spectroscopy, complementing chemical shifts and orientational restraints. Although a large number of magic-angle-spinning (MAS) NMR techniques have been available for distance measurements, traditional 13C and 15N NMR experiments are inherently limited to distances of a few angstroms due to the low gyromagnetic ratios of these nuclei. Recent development of fast MAS triple-resonance 19F and 1H NMR probes has stimulated the design of MAS NMR experiments that measure distances in the 1-2 nm range with high sensitivity. This review describes the principles and applications of these multiplexed multidimensional correlation distance NMR experiments, with an emphasis on 19F- and 1H-based distance experiments. Representative applications of these long-distance NMR methods to biological macromolecules as well as small molecules are reviewed.
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Affiliation(s)
- Alexander A Shcherbakov
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - João Medeiros-Silva
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Nhi Tran
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Martin D Gelenter
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
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19
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Angles G, Hail A, Dotson RJ, Pias SC. Atomistic simulations modify interpretation of spin-label oximetry data. Part 1: intensified water-lipid interfacial resistances. APPLIED MAGNETIC RESONANCE 2021; 52:1261-1289. [PMID: 37292189 PMCID: PMC10249954 DOI: 10.1007/s00723-021-01398-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 07/14/2021] [Accepted: 07/16/2021] [Indexed: 06/10/2023]
Abstract
The role of membrane cholesterol in cellular function and dysfunction has been the subject of much inquiry. A few studies have suggested that cholesterol may slow oxygen diffusive transport, altering membrane physical properties and reducing oxygen permeability. The primary experimental technique used in recent years to study membrane oxygen transport is saturation-recovery electron paramagnetic resonance (EPR) oximetry, using spin-label probes targeted to specific regions of a lipid bilayer. The technique has been used, in particular, to assess the influence of cholesterol on oxygen transport and membrane permeability. The reliability of such EPR recordings at the water-lipid interface near the phospholipid headgroups has been challenged by all-atom molecular dynamics (MD) simulation data that show substantive agreement with spin-label probe measurements throughout much of the bilayer. This work uses further MD simulations, with an updated oxygen model, to determine the location of the maximum resistance to permeation and the rate-limiting barrier to oxygen permeation in 1-palmitoyl,2-oleoylphosphatidylcholine (POPC) and POPC/cholesterol bilayers at 25 and 35°C. The current simulations show a spike of resistance to permeation in the headgroup region that was not detected by EPR but was predicted in early theoretical work by Diamond and Katz. Published experimental nuclear magnetic resonance (NMR) oxygen measurements provide key validation of the MD models and indicate that the positions and relative magnitudes of the phosphatidylcholine resistance peaks are accurate. Consideration of the headgroup-region resistances predicts bilayer permeability coefficients lower than estimated in EPR studies, giving permeabilities lower than the permeability of unstirred water layers of the same thickness. Here, the permeability of POPC at 35°C is estimated to be 13 cm/s, compared with 10 cm/s for POPC/cholesterol and 118 cm/s for simulation water layers of similar thickness. The value for POPC is 12 times lower than estimated from EPR measurements, while the value for POPC/cholesterol is 5 times lower. These findings underscore the value of atomic resolution models for guiding the interpretation of experimental probe-based measurements.
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Affiliation(s)
| | | | | | - Sally C. Pias
- Corresponding author: , Department of Chemistry, New Mexico Institute of Mining and Technology (New Mexico Tech), 801 Leroy Place, Socorro, NM 87801, USA
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20
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Unguryan VV, Golysheva EA, Dzuba SA. Double Electron-Electron Resonance of Spin-Labeled Cholestane in Model Membranes: Evidence for Substructures inside the Lipid Rafts. J Phys Chem B 2021; 125:9557-9563. [PMID: 34387998 DOI: 10.1021/acs.jpcb.1c05215] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Plasma membranes are assumed to be highly compartmentalized, which is believed to be important for the membrane protein functionality. The liquid ordered-disordered phase segregation in the membranes results in nanoscale liquid-ordered assemblies-lipid rafts. Double electron-electron resonance spectroscopy (DEER, also known as PELDOR) is sensitive to spin-spin dipolar interactions between spin labels at the nanoscale range of distances. Here, DEER is applied to spin-labeled cholestane, 3β-doxyl-5α-cholestane (DChl), diluted in bilayers composed of an equimolar mixture of dioleoyl-glycero-phosphocholine (DOPC) and dipalmitoyl-glycero-phosphocholine (DPPC) phospholipids, with cholesterol (Chol) added. The DEER data allowed us to detect clustering of the DChl molecules. Their lateral distribution in the clusters in the absence of Chol was found to be random, while in the presence of Chol it became quasi-regular. DEER time traces are fairly well simulated within a simple square superlattice model. For the 20 mol % Chol content, for which at physiological temperatures, the lipid rafts are formed, the found superlattice parameter was 3.7 nm. Assuming that lipid rafts are captioned upon shock freezing at the temperature of investigation (80 K), the found regularity of DChl lateral distribution was interpreted by raft substructuring, with the DChl molecules embedded between the substructures.
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Affiliation(s)
- Vasily V Unguryan
- Department of Physics, Novosibirsk State University, Novosibirsk 630090, Russia.,Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Elena A Golysheva
- Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Sergei A Dzuba
- Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
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21
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Interfacial hydration determines orientational and functional dimorphism of sterol-derived Raman tags in lipid-coated nanoparticles. Proc Natl Acad Sci U S A 2021; 118:2105913118. [PMID: 34389679 DOI: 10.1073/pnas.2105913118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Lipid-coated noble metal nanoparticles (L-NPs) combine the biomimetic surface properties of a self-assembled lipid membrane with the plasmonic properties of a nanoparticle (NP) core. In this work, we investigate derivatives of cholesterol, which can be found in high concentrations in biological membranes, and other terpenoids, as tunable, synthetic platforms to functionalize L-NPs. Side chains of different length and polarity, with a terminal alkyne group as Raman label, are introduced into cholesterol and betulin frameworks. The synthesized tags are shown to coexist in two conformations in the lipid layer of the L-NPs, identified as "head-out" and "head-in" orientations, whose relative ratio is determined by their interactions with the lipid-water hydrogen-bonding network. The orientational dimorphism of the tags introduces orthogonal functionalities into the NP surface for selective targeting and plasmon-enhanced Raman sensing, which is utilized for the identification and Raman imaging of epidermal growth factor receptor-overexpressing cancer cells.
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22
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Sutherland M, Kwon B, Hong M. Interactions of HIV gp41's membrane-proximal external region and transmembrane domain with phospholipid membranes from 31P NMR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183723. [PMID: 34352242 DOI: 10.1016/j.bbamem.2021.183723] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/22/2021] [Accepted: 07/30/2021] [Indexed: 11/30/2022]
Abstract
HIV-1 entry into cells requires coordinated changes of the conformation and dynamics of both the fusion protein, gp41, and the lipids in the cell membrane and virus envelope. Commonly proposed features of membrane deformation during fusion include high membrane curvature, lipid disorder, and membrane surface dehydration. The virus envelope and target cell membrane contain a diverse set of phospholipids and cholesterol. To dissect how different lipids interact with gp41 to contribute to membrane fusion, here we use 31P solid-state NMR spectroscopy to investigate the curvature, dynamics, and hydration of POPE, POPC and POPS membranes, with and without cholesterol, in the presence of a peptide comprising the membrane proximal external region (MPER) and transmembrane domain (TMD) of gp41. Static 31P NMR spectra indicate that the MPER-TMD induces strong negative Gaussian curvature (NGC) to the POPE membrane but little curvature to POPC and POPC:POPS membranes. The NGC manifests as an isotropic peak in the static NMR spectra, whose intensity increases with the peptide concentration. Cholesterol inhibits the NGC formation and stabilizes the lamellar phase. Relative intensities of magic-angle spinning 31P cross-polarization and direct-polarization spectra indicate that all three phospholipids become more mobile upon peptide binding. Finally, 2D 1H-31P correlation spectra show that the MPER-TMD enhances water 1H polarization transfer to the lipids, indicating that the membrane surfaces become more hydrated. These results suggest that POPE is an essential component of the high-curvature fusion site, and lipid dynamic disorder is a general feature of membrane restructuring during fusion.
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Affiliation(s)
- Madeleine Sutherland
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Byungsu Kwon
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA.
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23
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Markiewicz M, Szczelina R, Milanovic B, Subczynski WK, Pasenkiewicz-Gierula M. Chirality affects cholesterol-oxysterol association in water, a computational study. Comput Struct Biotechnol J 2021; 19:4319-4335. [PMID: 34429850 PMCID: PMC8361299 DOI: 10.1016/j.csbj.2021.07.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 07/18/2021] [Accepted: 07/21/2021] [Indexed: 01/04/2023] Open
Abstract
Cholesterol (Chol) is the most prevalent sterol in the animal kingdom and an indispensable component of mammalian cell membranes. Chol content in the membrane is strictly controlled, although the oxidation of phospholipids may change the relative content of membrane Chol. An excess of it results in the formation of pure Chol microdomains in the membrane. It is likely that some Chol molecules detach from the domains and self-assemble in the aqueous environment. This may promote Chol microcrystallisation, which initiates the development of gallstones and atherosclerotic plaque. In this study, the molecular dynamics, free energy perturbation, umbrella sampling and Voronoi diagram methods are used to reveal the details of self-association of Chol and its oxidised forms (oxChol), namely 7α,β-hydroxycholesterol and 7α,β-hydroperoxycholesterol, in water. In the first part of the study the interactions between a sterol monomer and water over a short and longer timescale as well as the energy of hydration of each sterol are analysed. This helps one to understand Chol-Chol and Chol-OxChol with different chirality self-association in water better, which is analysed in the second part of the study. The Voronoi diagram approach is used to determine the relative arrangement of molecules in the dimer and, most importantly, to analyse the dehydration of the contacting surfaces of the assembling molecules. Free energy calculations indicate that Chol and 7β-hydroxycholesterol associate into the most stable dimer and that Chol-Chol is the next most stable of the five dimers studied. Employing different computational methods enables us to obtain an adequate picture of Chol-sterol self-association in water, which includes dynamic, energetic and temporal aspects of the process.
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Affiliation(s)
- Michal Markiewicz
- Department of Computational Biophysics and Bioinformatics, Faculty of Biochemistry, Biophysics, and Biotechnology, Jagiellonian University, Krakow, Poland
| | - Robert Szczelina
- Division of Computational Mathematics, Faculty of Mathematics and Computer Science, Jagiellonian University, 30-348 Krakow, Poland
| | - Bozena Milanovic
- Department of Computational Biophysics and Bioinformatics, Faculty of Biochemistry, Biophysics, and Biotechnology, Jagiellonian University, Krakow, Poland
| | - Witold K. Subczynski
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Marta Pasenkiewicz-Gierula
- Department of Computational Biophysics and Bioinformatics, Faculty of Biochemistry, Biophysics, and Biotechnology, Jagiellonian University, Krakow, Poland
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