1
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Unwin N. Influence of lipid bilayer on the structure of the muscle-type nicotinic acetylcholine receptor. Proc Natl Acad Sci U S A 2024; 121:e2319913121. [PMID: 38683987 PMCID: PMC11087746 DOI: 10.1073/pnas.2319913121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 03/22/2024] [Indexed: 05/02/2024] Open
Abstract
The muscle-type nicotinic acetylcholine receptor is a transmitter-gated ion channel residing in the plasma membrane of electrocytes and striated muscle cells. It is present predominantly at synaptic junctions, where it effects rapid depolarization of the postsynaptic membrane in response to acetylcholine released into the synaptic cleft. Previously, cryo-EM of intact membrane from Torpedo revealed that the lipid bilayer surrounding the junctional receptor has a uniquely asymmetric and ordered structure, due to a high concentration of cholesterol. It is now shown that this special lipid environment influences the transmembrane (TM) folding of the protein. All five submembrane MX helices of the membrane-intact junctional receptor align parallel to the surface of the cholesterol-ordered lipids in the inner leaflet of the bilayer; also, the TM helices in the outer leaflet are splayed apart. However in the structure obtained from the same protein after extraction and incorporation in nanodiscs, the MX helices do not align to a planar surface, and the TM helices arrange compactly in the outer leaflet. Realignment of the MX helices of the nanodisc-solved structure to a planar surface converts their adjoining TM helices into an obligatory splayed configuration, characteristic of the junctional receptor. Thus, the form of the receptor sustained by the special lipid environment of the synaptic junction is the one that mediates fast synaptic transmission; whereas, the nanodisc-embedded protein may be like the extrajunctional form, existing in a disordered lipid environment.
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Affiliation(s)
- Nigel Unwin
- Medical Research Council Laboratory of Molecular Biology, CambridgeCB2 0QH, United Kingdom
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2
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Sandberg JW, Santiago-McRae E, Ennis J, Brannigan G. The density-threshold affinity: Calculating lipid binding affinities from unbiased coarse-grained molecular dynamics simulations. Methods Enzymol 2024; 701:47-82. [PMID: 39025580 DOI: 10.1016/bs.mie.2024.03.008] [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: 07/20/2024]
Abstract
Many membrane proteins are sensitive to their local lipid environment. As structural methods for membrane proteins have improved, there is growing evidence of direct, specific binding of lipids to protein surfaces. Unfortunately the workhorse of understanding protein-small molecule interactions, the binding affinity for a given site, is experimentally inaccessible for these systems. Coarse-grained molecular dynamics simulations can be used to bridge this gap, and are relatively straightforward to learn. Such simulations allow users to observe spontaneous binding of lipids to membrane proteins and quantify localized densities of individual lipids or lipid fragments. In this chapter we outline a protocol for extracting binding affinities from these localized distributions, known as the "density threshold affinity." The density threshold affinity uses an adaptive and flexible definition of site occupancy that alleviates the need to distinguish between "bound'' lipids and bulk lipids that are simply diffusing through the site. Furthermore, the method allows "bead-level" resolution that is suitable for the case where lipids share binding sites, and circumvents ambiguities about a relevant reference state. This approach provides a convenient and straightforward method for comparing affinities of a single lipid species for multiple sites, multiple lipids for a single site, and/or a single lipid species modeled using multiple forcefields.
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Affiliation(s)
- Jesse W Sandberg
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, United States
| | - Ezry Santiago-McRae
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, United States
| | - Jahmal Ennis
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, United States
| | - Grace Brannigan
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, United States; Department of Physics, Rutgers University, Camden, NJ, United States.
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3
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Dalal V, Arcario MJ, Petroff JT, Tan BK, Dietzen NM, Rau MJ, Fitzpatrick JAJ, Brannigan G, Cheng WWL. Lipid nanodisc scaffold and size alter the structure of a pentameric ligand-gated ion channel. Nat Commun 2024; 15:25. [PMID: 38167383 PMCID: PMC10762164 DOI: 10.1038/s41467-023-44366-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Accepted: 12/11/2023] [Indexed: 01/05/2024] Open
Abstract
Lipid nanodiscs have become a standard tool for studying membrane proteins, including using single particle cryo-electron microscopy (cryo-EM). We find that reconstituting the pentameric ligand-gated ion channel (pLGIC), Erwinia ligand-gated ion channel (ELIC), in different nanodiscs produces distinct structures by cryo-EM. The effect of the nanodisc on ELIC structure extends to the extracellular domain and agonist binding site. Additionally, molecular dynamic simulations indicate that nanodiscs of different size impact ELIC structure and that the nanodisc scaffold directly interacts with ELIC. These findings suggest that the nanodisc plays a crucial role in determining the structure of pLGICs, and that reconstitution of ion channels in larger nanodiscs may better approximate a lipid membrane environment.
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Affiliation(s)
- Vikram Dalal
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Mark J Arcario
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - John T Petroff
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Brandon K Tan
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Noah M Dietzen
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Michael J Rau
- Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO, USA
| | - James A J Fitzpatrick
- Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO, USA
| | - Grace Brannigan
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, USA
- Department of Physics, Rutgers University, Camden, NJ, USA
| | - Wayland W L Cheng
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA.
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4
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Lan YJ, Cheng CC, Chu SC, Chiang YW. A gating mechanism of the BsYetJ calcium channel revealed in an endoplasmic reticulum lipid environment. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184153. [PMID: 36948481 DOI: 10.1016/j.bbamem.2023.184153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 02/22/2023] [Accepted: 03/14/2023] [Indexed: 03/24/2023]
Abstract
The transmembrane BAX inhibitor-1-containing motif 6 (TMBIM6) is suggested to modulate apoptosis by regulating calcium homeostasis in the endoplasmic reticulum (ER). However, the precise molecular mechanism underlying this calcium regulation remains poorly understood. To shed light on this issue, we investigated all negatively charged residues in BsYetJ, a bacterial homolog of TMBIM6, using mutagenesis and fluorescence-based functional assays. We reconstituted BsYetJ in membrane vesicles with a lipid composition similar to that of the ER. Our results show that the charged residues E49 and R205 work together as a major gate, regulating calcium conductance in these ER-like lipid vesicles. However, these residues become largely inactive when reconstituted in other lipid environments. In addition, we found that D195 acts as a minor filter compared to the E49-R205 dyad. Our study uncovers a previously unknown function of BsYetJ/TMBIM6 in the calcium-dependent inactivation of BsYetJ, providing a framework for the development of a lipid-dependent mechanistic model of BsYetJ that will facilitate our understanding of calcium-dependent apoptosis.
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Affiliation(s)
- Yu-Jing Lan
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Chu-Chun Cheng
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Shu-Chi Chu
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan.
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5
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Umebayashi M, Takemoto S, Reymond L, Sundukova M, Hovius R, Bucci A, Heppenstall PA, Yokota H, Johnsson K, Riezman H. A covalently linked probe to monitor local membrane properties surrounding plasma membrane proteins. J Cell Biol 2022; 222:213783. [PMID: 36571579 PMCID: PMC9802683 DOI: 10.1083/jcb.202206119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 09/21/2022] [Accepted: 12/09/2022] [Indexed: 12/27/2022] Open
Abstract
Functional membrane proteins in the plasma membrane are suggested to have specific membrane environments that play important roles to maintain and regulate their function. However, the local membrane environments of membrane proteins remain largely unexplored due to the lack of available techniques. We have developed a method to probe the local membrane environment surrounding membrane proteins in the plasma membrane by covalently tethering a solvatochromic, environment-sensitive dye, Nile Red, to a GPI-anchored protein and the insulin receptor through a flexible linker. The fluidity of the membrane environment of the GPI-anchored protein depended upon the saturation of the acyl chains of the lipid anchor. The local environment of the insulin receptor was distinct from the average plasma membrane fluidity and was quite dynamic and heterogeneous. Upon addition of insulin, the local membrane environment surrounding the receptor specifically increased in fluidity in an insulin receptor-kinase dependent manner and on the distance between the dye and the receptor.
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Affiliation(s)
- Miwa Umebayashi
- https://ror.org/01swzsf04Department of Biochemistry and National Centre for Competence in Research in Chemical Biology, Sciences II, University of Geneva, Geneva, Switzerland,Myoridge Co. Ltd., Kyoto, Japan
| | - Satoko Takemoto
- Image Processing Research Team, RIKEN Centre for Advanced Photonics, Wako, Japan
| | - Luc Reymond
- Ecole Polytechnique Fédérale de Lausanne, Institute of Chemical Sciences and Engineering (ISIC), Institute of Bioengineering, National Centre of Competence in Research (NCCR) in Chemical Biology, Lausanne, Switzerland
| | - Mayya Sundukova
- Epigenetics and Neurobiology Unit, European Molecular Biology Laboratory Rome, Monterotondo, Italy,https://ror.org/000xsnr85Instituto Biofisika (UPV/EHU, CSIC), University of the Basque Country, Leioa, Spain,Fundación Biofísica Bizkaia/Biofisika Bizkaia Fundazioa (FBB), Leioa, Spain
| | - Ruud Hovius
- Ecole Polytechnique Fédérale de Lausanne, Institute of Chemical Sciences and Engineering (ISIC), Institute of Bioengineering, National Centre of Competence in Research (NCCR) in Chemical Biology, Lausanne, Switzerland
| | - Annalisa Bucci
- Epigenetics and Neurobiology Unit, European Molecular Biology Laboratory Rome, Monterotondo, Italy
| | - Paul A. Heppenstall
- Epigenetics and Neurobiology Unit, European Molecular Biology Laboratory Rome, Monterotondo, Italy
| | - Hideo Yokota
- Image Processing Research Team, RIKEN Centre for Advanced Photonics, Wako, Japan
| | - Kai Johnsson
- Department of Chemical Biology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Howard Riezman
- https://ror.org/01swzsf04Department of Biochemistry and National Centre for Competence in Research in Chemical Biology, Sciences II, University of Geneva, Geneva, Switzerland,Correspondence to Howard Riezman:
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6
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Ho PS, Kao TY, Li CC, Lan YJ, Lai YC, Chiang YW. Nanodisc Lipids Exhibit Singular Behaviors Implying Critical Phenomena. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:15372-15383. [PMID: 36454955 DOI: 10.1021/acs.langmuir.2c02596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Nanodiscs are broadly used for characterization of membrane proteins as they are generally assumed to provide a near-native environment. In fact, it is an open question whether the physical properties of lipids in nanodiscs and membrane vesicles of the same lipid composition are identical. Here, we investigate the properties of lipids (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dilauroyl-sn-glycero-3-phosphocholine, and their mixtures) in two different sample types, nanodiscs and multilamellar vesicles, by means of spin-label electron spin resonance techniques. Our results provide a quantitative description of lipid dynamics and ordering, elucidating the molecular details of how lipids in the two sample types behave differently in response to temperature and lipid composition. We show that the properties of lipids are altered in nanodiscs such that the dissimilarity of the fluid and gel lipid phases is reduced, and the first-order phase transitions are largely abolished in nanodiscs. We unveil that the ensemble of lipids in the middle of a nanodisc bilayer, as probed by the end-chain spin-label 16-PC, is promoted to a state close to a miscibility critical point, thereby rendering the phase transitions continuous. Critical phenomena have recently been proposed to explain features of the heterogeneity in native cell membranes. Our results lay the groundwork for how to establish a near-native environment in nanodiscs with simple organization of lipid components.
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Affiliation(s)
- Pei-Shan Ho
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Te-Yu Kao
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Chieh-Chin Li
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Yu-Jing Lan
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
| | - Yei-Chen Lai
- Department of Chemistry, National Chung Hsing University, Taichung 402-002, Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry, National Tsing Hua University, Hsinchu 300-044, Taiwan
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7
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Petroff JT, Dietzen NM, Santiago-McRae E, Deng B, Washington MS, Chen LJ, Trent Moreland K, Deng Z, Rau M, Fitzpatrick JAJ, Yuan P, Joseph TT, Hénin J, Brannigan G, Cheng WWL. Open-channel structure of a pentameric ligand-gated ion channel reveals a mechanism of leaflet-specific phospholipid modulation. Nat Commun 2022; 13:7017. [PMID: 36385237 PMCID: PMC9668969 DOI: 10.1038/s41467-022-34813-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 11/08/2022] [Indexed: 11/18/2022] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs) mediate synaptic transmission and are sensitive to their lipid environment. The mechanism of phospholipid modulation of any pLGIC is not well understood. We demonstrate that the model pLGIC, ELIC (Erwinia ligand-gated ion channel), is positively modulated by the anionic phospholipid, phosphatidylglycerol, from the outer leaflet of the membrane. To explore the mechanism of phosphatidylglycerol modulation, we determine a structure of ELIC in an open-channel conformation. The structure shows a bound phospholipid in an outer leaflet site, and structural changes in the phospholipid binding site unique to the open-channel. In combination with streamlined alchemical free energy perturbation calculations and functional measurements in asymmetric liposomes, the data support a mechanism by which an anionic phospholipid stabilizes the activated, open-channel state of a pLGIC by specific, state-dependent binding to this site.
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Affiliation(s)
- John T Petroff
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Noah M Dietzen
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Ezry Santiago-McRae
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, USA
| | - Brett Deng
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Maya S Washington
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Lawrence J Chen
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - K Trent Moreland
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Zengqin Deng
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
| | - Michael Rau
- Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO, USA
| | - James A J Fitzpatrick
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Neuroscience, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Biomedical Engineering, Washington University School of Medicine, Saint Louis, MO, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
| | - Thomas T Joseph
- Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Jérôme Hénin
- Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, Université Paris Cité, CNRS UPR 9080, Paris, France
| | - Grace Brannigan
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, USA
- Department of Physics, Rutgers University, Camden, NJ, USA
| | - Wayland W L Cheng
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA.
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8
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Alanazi M, Arafa WA, Althobaiti IO, Altaleb HA, Bakr RB, Elkanzi NAA. Green Design, Synthesis, and Molecular Docking Study of Novel Quinoxaline Derivatives with Insecticidal Potential against Aphis craccivora. ACS OMEGA 2022; 7:27674-27689. [PMID: 35967065 PMCID: PMC9366785 DOI: 10.1021/acsomega.2c03332] [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: 05/28/2022] [Accepted: 07/15/2022] [Indexed: 06/15/2023]
Abstract
An efficient and environmentally friendly method was established for designing novel 3-amino-1,4-dihydroquinoxaline-2-carbonitrile (1) via the reaction of bromomalononitrile and benzene-1,2-diamine under microwave irradiation in an excellent yield (93%). This targeted amino derivative was utilized for the construction of a series of Schiff bases (8-13). A new series of thiazolidinone derivatives (15-20) were synthesized in high yields (89-96%) via treatment of thioglycolic acid with Schiff bases (8-13) under microwave irradiation in high yields (89-96%). Moreover, new pyrimidine derivatives (26-30 and 35-38) were prepared by treatment of compound 1 with arylidenes (21-25) and/or alkylidenemalononitriles (31-34) using piperidine as a basic catalyst under microwave conditions. Based on elemental analyses and spectral data, the structures of the new assembled compounds were determined. The newly synthesized quinoxaline derivatives were screened and studied as an insecticidal agent against Aphis craccivora. The obtained results indicate that compound 16 is the most toxicological agent against nymphs of cowpea aphids (Aphis craccivora) compared to the other synthesized pyrimidine and thiazolidinone derivatives. The molecular docking study of the new quinoxaline derivatives registered that compound 16 had the highest binding score (-10.54 kcal/mol) and the thiazolidinone moiety formed hydrogen bonds with Trp143.
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Affiliation(s)
- Mariam
Azzam Alanazi
- Chemistry
Department, College of Science, Jouf University, P.O. Box 2014, Sakaka 2014, Saudi Arabia
| | - Wael A.A. Arafa
- Chemistry
Department, College of Science, Jouf University, P.O. Box 2014, Sakaka 2014, Saudi Arabia
- Chemistry
Department, Faculty of Science, Fayoum University, P.O. Box 63514, Fayoum 63514, Egypt
| | - Ibrahim O. Althobaiti
- Department
of Chemistry, College of Science and Arts, Jouf University, Sakaka 42421, Saudi Arabia
| | - Hamud A. Altaleb
- Department
of Chemistry, Faculty of Science, Islamic
University of Madinah, Madinah 42351, Saudi Arabia
| | - Rania B. Bakr
- Department
of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Beni-Suef University, Beni-Suef 62514, Egypt
| | - Nadia A. A. Elkanzi
- Chemistry
Department, College of Science, Jouf University, P.O. Box 2014, Sakaka 2014, Saudi Arabia
- Chemistry
Department, Faculty of Science, Aswan University, P.O. Box 81528, Aswan 81528, Egypt
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9
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Tucholski T, Ge Y. Fourier-transform ion cyclotron resonance mass spectrometry for characterizing proteoforms. MASS SPECTROMETRY REVIEWS 2022; 41:158-177. [PMID: 32894796 PMCID: PMC7936991 DOI: 10.1002/mas.21653] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 08/26/2020] [Accepted: 08/26/2020] [Indexed: 05/05/2023]
Abstract
Proteoforms contribute functional diversity to the proteome and aberrant proteoforms levels have been implicated in biological dysfunction and disease. Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), with its ultrahigh mass-resolving power, mass accuracy, and versatile tandem MS capabilities, has empowered top-down, middle-down, and native MS-based approaches for characterizing proteoforms and their complexes in biological systems. Herein, we review the features which make FT-ICR MS uniquely suited for measuring proteoform mass with ultrahigh resolution and mass accuracy; obtaining in-depth proteoform sequence coverage with expansive tandem MS capabilities; and unambiguously identifying and localizing post-translational and noncovalent modifications. We highlight examples from our body of work in which we have quantified and comprehensively characterized proteoforms from cardiac and skeletal muscle to better understand conditions such as chronic heart failure, acute myocardial infarction, and sarcopenia. Structural characterization of monoclonal antibodies and their proteoforms by FT-ICR MS and emerging applications, such as native top-down FT-ICR MS and high-throughput top-down FT-ICR MS-based proteomics at 21 T, are also covered. Historically, the information gleaned from FT-ICR MS analyses have helped provide biological insights. We predict FT-ICR MS will continue to enable the study of proteoforms of increasing size from increasingly complex endogenous mixtures and facilitate the benchmarking of sensitive and specific assays for clinical diagnostics. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.
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Affiliation(s)
- Trisha Tucholski
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706
| | - Ying Ge
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI, 53706
- Human Proteomics Program, University of Wisconsin-Madison, Madison, WI, 53705
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10
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Dietzen NM, Arcario MJ, Chen LJ, Petroff JT, Moreland KT, Krishnan K, Brannigan G, Covey DF, Cheng WW. Polyunsaturated fatty acids inhibit a pentameric ligand-gated ion channel through one of two binding sites. eLife 2022; 11:74306. [PMID: 34982031 PMCID: PMC8786314 DOI: 10.7554/elife.74306] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 12/31/2021] [Indexed: 01/01/2023] Open
Abstract
Polyunsaturated fatty acids (PUFAs) inhibit pentameric ligand-gated ion channels (pLGICs) but the mechanism of inhibition is not well understood. The PUFA, docosahexaenoic acid (DHA), inhibits agonist responses of the pLGIC, ELIC, more effectively than palmitic acid, similar to the effects observed in the GABAA receptor and nicotinic acetylcholine receptor. Using photo-affinity labeling and coarse-grained molecular dynamics simulations, we identified two fatty acid binding sites in the outer transmembrane domain (TMD) of ELIC. Fatty acid binding to the photolabeled sites is selective for DHA over palmitic acid, and specific for an agonist-bound state. Hexadecyl-methanethiosulfonate modification of one of the two fatty acid binding sites in the outer TMD recapitulates the inhibitory effect of PUFAs in ELIC. The results demonstrate that DHA selectively binds to multiple sites in the outer TMD of ELIC, but that state-dependent binding to a single intrasubunit site mediates DHA inhibition of ELIC.
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Affiliation(s)
- Noah M Dietzen
- Department of Anesthesiology, Washington University in St. Louis, St Louis, United States
| | - Mark J Arcario
- Department of Anesthesiology, Washington University in St. Louis, St Louis, United States
| | - Lawrence J Chen
- Department of Anesthesiology, Washington University in St. Louis, St Louis, United States
| | - John T Petroff
- Department of Anesthesiology, Washington University in St. Louis, St Louis, United States
| | - K Trent Moreland
- Department of Anesthesiology, Washington University in St. Louis, St Louis, United States
| | - Kathiresan Krishnan
- Department of Developmental Biology, Washington University in St. Louis, St Louis, United States
| | - Grace Brannigan
- Center for the Computational and Integrative Biology, Rutgers University, Camden, United States.,Department of Physics, Rutgers University, Camden, United States
| | - Douglas F Covey
- Department of Anesthesiology, Washington University in St. Louis, St Louis, United States.,Department of Developmental Biology, Washington University in St. Louis, St Louis, United States.,Department of Psychiatry, Washington University in St. Louis, St. Louis, United States.,Taylor Institute for Innovative Psychiatric Research, Washington University in St. Louis, St. Louis, United States
| | - Wayland Wl Cheng
- Department of Anesthesiology, Washington University in St. Louis, St Louis, United States
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11
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Şterbuleac D. Molecular dynamics: a powerful tool for studying the medicinal chemistry of ion channel modulators. RSC Med Chem 2021; 12:1503-1518. [PMID: 34671734 PMCID: PMC8459385 DOI: 10.1039/d1md00140j] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Accepted: 07/21/2021] [Indexed: 01/10/2023] Open
Abstract
Molecular dynamics (MD) simulations allow researchers to investigate the behavior of desired biological targets at ever-decreasing costs with ever-increasing precision. Among the biological macromolecules, ion channels are remarkable transmembrane proteins, capable of performing special biological processes and revealing a complex regulatory matrix, including modulation by small molecules, either endogenous or exogenous. Recently, given the developments in ion channel structure determination and accessibility of bio-computational techniques, MD and related tools are becoming increasingly popular in the intense research area regarding ligand-channel interactions. This review synthesizes and presents the most important fields of MD involvement in investigating channel-molecule interactions, including, but not limited to, deciphering the binding modes of ligands to their ion channel targets and the mechanisms through which chemical compounds exert their effect on channel function. Special attention is devoted to the importance of more elaborate methods, such as free energy calculations, while principles regarding drug design and discovery are highlighted. Several technical aspects involving the creation and simulation of channel-molecule MD systems (ligand parameterization, proper membrane setup, system building, etc.) are also presented.
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Affiliation(s)
- Daniel Şterbuleac
- Department of Health and Human Development, "Ştefan cel Mare" University of Suceava Str. Universităţii 13, 720229, E Building Suceava Romania
- Department of Forestry and Environmental Protection, "Ştefan cel Mare" University of Suceava Str. Universităţii 13, 720229, E Building Suceava Romania
- Integrated Center for Research, Development and Innovation in Advanced Materials, Nanotechnologies and Distributed Systems for Fabrication and Control (MANSiD), "Ştefan cel Mare" University of Suceava Str. Universităţii 13 720229 Suceava Romania
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12
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Rovšnik U, Zhuang Y, Forsberg BO, Carroni M, Yvonnesdotter L, Howard RJ, Lindahl E. Dynamic closed states of a ligand-gated ion channel captured by cryo-EM and simulations. Life Sci Alliance 2021; 4:e202101011. [PMID: 34210687 PMCID: PMC8326787 DOI: 10.26508/lsa.202101011] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 06/10/2021] [Accepted: 06/11/2021] [Indexed: 11/25/2022] Open
Abstract
Ligand-gated ion channels are critical mediators of electrochemical signal transduction across evolution. Biophysical and pharmacological characterization of these receptor proteins relies on high-quality structures in multiple, subtly distinct functional states. However, structural data in this family remain limited, particularly for resting and intermediate states on the activation pathway. Here, we report cryo-electron microscopy (cryo-EM) structures of the proton-activated Gloeobacter violaceus ligand-gated ion channel (GLIC) under three pH conditions. Decreased pH was associated with improved resolution and side chain rearrangements at the subunit/domain interface, particularly involving functionally important residues in the β1-β2 and M2-M3 loops. Molecular dynamics simulations substantiated flexibility in the closed-channel extracellular domains relative to the transmembrane ones and supported electrostatic remodeling around E35 and E243 in proton-induced gating. Exploration of secondary cryo-EM classes further indicated a low-pH population with an expanded pore. These results allow us to define distinct protonation and activation steps in pH-stimulated conformational cycling in GLIC, including interfacial rearrangements largely conserved in the pentameric channel family.
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Affiliation(s)
- Urška Rovšnik
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Yuxuan Zhuang
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Björn O Forsberg
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Marta Carroni
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Linnea Yvonnesdotter
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Rebecca J Howard
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Erik Lindahl
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
- Department of Applied Physics, Science for Life Laboratory, Kungliga Tekniska Högskolan Royal Institute of Technology, Solna, Sweden
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13
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Jodaitis L, van Oene T, Martens C. Assessing the Role of Lipids in the Molecular Mechanism of Membrane Proteins. Int J Mol Sci 2021; 22:7267. [PMID: 34298884 PMCID: PMC8306737 DOI: 10.3390/ijms22147267] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/30/2021] [Accepted: 07/01/2021] [Indexed: 02/06/2023] Open
Abstract
Membrane proteins have evolved to work optimally within the complex environment of the biological membrane. Consequently, interactions with surrounding lipids are part of their molecular mechanism. Yet, the identification of lipid-protein interactions and the assessment of their molecular role is an experimental challenge. Recently, biophysical approaches have emerged that are compatible with the study of membrane proteins in an environment closer to the biological membrane. These novel approaches revealed specific mechanisms of regulation of membrane protein function. Lipids have been shown to play a role in oligomerization, conformational transitions or allosteric coupling. In this review, we summarize the recent biophysical approaches, or combination thereof, that allow to decipher the role of lipid-protein interactions in the mechanism of membrane proteins.
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Affiliation(s)
| | | | - Chloé Martens
- Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, 1050 Brussels, Belgium; (L.J.); (T.v.O.)
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14
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Elephants in the Dark: Insights and Incongruities in Pentameric Ligand-gated Ion Channel Models. J Mol Biol 2021; 433:167128. [PMID: 34224751 DOI: 10.1016/j.jmb.2021.167128] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 06/25/2021] [Accepted: 06/25/2021] [Indexed: 02/06/2023]
Abstract
The superfamily of pentameric ligand-gated ion channels (pLGICs) comprises key players in electrochemical signal transduction across evolution, including historic model systems for receptor allostery and targets for drug development. Accordingly, structural studies of these channels have steadily increased, and now approach 250 depositions in the protein data bank. This review contextualizes currently available structures in the pLGIC family, focusing on morphology, ligand binding, and gating in three model subfamilies: the prokaryotic channel GLIC, the cation-selective nicotinic acetylcholine receptor, and the anion-selective glycine receptor. Common themes include the challenging process of capturing and annotating channels in distinct functional states; partially conserved gating mechanisms, including remodeling at the extracellular/transmembrane-domain interface; and diversity beyond the protein level, arising from posttranslational modifications, ligands, lipids, and signaling partners. Interpreting pLGIC structures can be compared to describing an elephant in the dark, relying on touch alone to comprehend the many parts of a monumental beast: each structure represents a snapshot in time under specific experimental conditions, which must be integrated with further structure, function, and simulations data to build a comprehensive model, and understand how one channel may fundamentally differ from another.
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15
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Structure and function at the lipid-protein interface of a pentameric ligand-gated ion channel. Proc Natl Acad Sci U S A 2021; 118:2100164118. [PMID: 34083441 DOI: 10.1073/pnas.2100164118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Although it has long been proposed that membrane proteins may contain tightly bound lipids, their identity, the structure of their binding sites, and their functional and structural relevance have remained elusive. To some extent, this is because tightly bound lipids are often located at the periphery of proteins, where the quality of density maps is usually poorer, and because they may be outcompeted by detergent molecules used during standard purification procedures. As a step toward characterizing natively bound lipids in the superfamily of pentameric ligand-gated ion channels (pLGICs), we applied single-particle cryogenic electron microscopy to fragments of native membrane obtained in the complete absence of detergent-solubilization steps. Because of the heterogeneous lipid composition of membranes in the secretory pathway of eukaryotic cells, we chose to study a bacterial pLGIC (ELIC) expressed in Escherichia coli's inner membrane. We obtained a three-dimensional reconstruction of unliganded ELIC (2.5-Å resolution) that shows clear evidence for two types of tightly bound lipid at the protein-bulk-membrane interface. One of them was consistent with a "regular" diacylated phospholipid, in the cytoplasmic leaflet, whereas the other one was consistent with the tetra-acylated structure of cardiolipin, in the periplasmic leaflet. Upon reconstitution in E. coli polar-lipid bilayers, ELIC retained the functional properties characteristic of members of this superfamily, and thus, the fitted atomic model is expected to represent the (long-debated) unliganded-closed, "resting" conformation of this ion channel. Notably, the addition of cardiolipin to phosphatidylcholine membranes restored the ion-channel activity that is largely lost in phosphatidylcholine-only bilayers.
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16
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Sharp L, Brannigan G. Spontaneous lipid binding to the nicotinic acetylcholine receptor in a native membrane. J Chem Phys 2021; 154:185102. [PMID: 34241006 DOI: 10.1063/5.0046333] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The nicotinic acetylcholine receptor (nAChR) and other pentameric ligand-gated ion channels are native to neuronal membranes with an unusual lipid composition. While it is well-established that these receptors can be significantly modulated by lipids, the underlying mechanisms have been primarily studied in model membranes with few lipid species. Here, we use coarse-grained molecular dynamics simulation to probe specific binding of lipids in a complex quasi-neuronal membrane. We ran a total of 50 μs of simulations of a single nAChR in a membrane composed of 36 species of lipids. Competition between multiple lipid species produces a complex distribution. We find that overall, cholesterol selects for concave inter-subunit sites and polyunsaturated fatty acids select for convex M4 sites, while monounsaturated and saturated lipids are unenriched in the nAChR boundary. We propose the "density-threshold affinity" as a metric calculated from continuous density distributions, which reduces to a standard affinity in two-state binding. We find that the density-threshold affinity for M4 weakens with chain rigidity, which suggests that flexible chains may help relax packing defects caused by the conical protein shape. For any site, PE headgroups have the strongest affinity of all phospholipid headgroups, but anionic lipids still yield moderately high affinities for the M4 sites as expected. We observe cooperative effects between anionic headgroups and saturated chains at the M4 site in the inner leaflet. We also analyze affinities for individual anionic headgroups. When combined, these insights may reconcile several apparently contradictory experiments on the role of anionic phospholipids in modulating nAChR.
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Affiliation(s)
- Liam Sharp
- Center for Computational and Integrative Biology, Rutgers University-Camden, Camden, New Jersey 08102, USA
| | - Grace Brannigan
- Center for Computational and Integrative Biology, Rutgers University-Camden, Camden, New Jersey 08102, USA
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17
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Signal transduction through Cys-loop receptors is mediated by the nonspecific bumping of closely apposed domains. Proc Natl Acad Sci U S A 2021; 118:2021016118. [PMID: 33785596 DOI: 10.1073/pnas.2021016118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
One of the most fundamental questions in the field of Cys-loop receptors (pentameric ligand-gated ion channels, pLGICs) is how the affinity for neurotransmitters and the conductive/nonconductive state of the transmembrane pore are correlated despite the ∼60-Å distance between the corresponding domains. Proposed mechanisms differ, but they all converge into the idea that interactions between wild-type side chains across the extracellular-transmembrane-domain (ECD-TMD) interface are crucial for this phenomenon. Indeed, the successful design of fully functional chimeras that combine intact ECD and TMD modules from different wild-type pLGICs has commonly been ascribed to the residual conservation of sequence that exists at the level of the interfacial loops even between evolutionarily distant parent channels. Here, using mutagenesis, patch-clamp electrophysiology, and radiolabeled-ligand binding experiments, we studied the effect of eliminating this residual conservation of sequence on ion-channel function and cell-surface expression. From our results, we conclude that proper state interconversion ("gating") does not require conservation of sequence-or even physicochemical properties-across the ECD-TMD interface. Wild-type ECD and TMD side chains undoubtedly interact with their surroundings, but the interactions between them-straddling the interface-do not seem to be more important for gating than those occurring elsewhere in the protein. We propose that gating of pLGICs requires, instead, that the overall structure of the interfacial loops be conserved, and that their relative orientation and distance be the appropriate ones for changes in one side to result in changes in the other, in a phenomenon akin to the nonspecific "bumping" of closely apposed domains.
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18
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Rao S, Klesse G, Lynch CI, Tucker SJ, Sansom MSP. Molecular Simulations of Hydrophobic Gating of Pentameric Ligand Gated Ion Channels: Insights into Water and Ions. J Phys Chem B 2021; 125:981-994. [PMID: 33439645 PMCID: PMC7869105 DOI: 10.1021/acs.jpcb.0c09285] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 12/13/2020] [Indexed: 12/30/2022]
Abstract
Ion channels are proteins which form gated nanopores in biological membranes. Many channels exhibit hydrophobic gating, whereby functional closure of a pore occurs by local dewetting. The pentameric ligand gated ion channels (pLGICs) provide a biologically important example of hydrophobic gating. Molecular simulation studies comparing additive vs polarizable models indicate predictions of hydrophobic gating are robust to the model employed. However, polarizable models suggest favorable interactions of hydrophobic pore-lining regions with chloride ions, of relevance to both synthetic carriers and channel proteins. Electrowetting of a closed pLGIC hydrophobic gate requires too high a voltage to occur physiologically but may inform designs for switchable nanopores. Global analysis of ∼200 channels yields a simple heuristic for structure-based prediction of (closed) hydrophobic gates. Simulation-based analysis is shown to provide an aid to interpretation of functional states of new channel structures. These studies indicate the importance of understanding the behavior of water and ions within the nanoconfined environment presented by ion channels.
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Affiliation(s)
- Shanlin Rao
- Department
of Biochemistry, University of Oxford, Oxford, U.K.
| | - Gianni Klesse
- Clarendon
Laboratory, Department of Physics, University
of Oxford, Oxford, U.K.
| | | | - Stephen J. Tucker
- Clarendon
Laboratory, Department of Physics, University
of Oxford, Oxford, U.K.
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19
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Valentine ML, Waterland MK, Fathizadeh A, Elber R, Baiz CR. Interfacial Dynamics in Lipid Membranes: The Effects of Headgroup Structures. J Phys Chem B 2021; 125:1343-1350. [DOI: 10.1021/acs.jpcb.0c08755] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Mason L. Valentine
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712-1224, United States
| | - Maya K. Waterland
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712-1224, United States
| | - Arman Fathizadeh
- Oden Institute for Computational Science and Engineering, Austin, Texas 78712, United States
| | - Ron Elber
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712-1224, United States
- Oden Institute for Computational Science and Engineering, Austin, Texas 78712, United States
| | - Carlos R. Baiz
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712-1224, United States
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20
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Yuvaraj JK, Roberts RE, Sonntag Y, Hou XQ, Grosse-Wilde E, Machara A, Zhang DD, Hansson BS, Johanson U, Löfstedt C, Andersson MN. Putative ligand binding sites of two functionally characterized bark beetle odorant receptors. BMC Biol 2021; 19:16. [PMID: 33499862 PMCID: PMC7836466 DOI: 10.1186/s12915-020-00946-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 12/22/2020] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Bark beetles are major pests of conifer forests, and their behavior is primarily mediated via olfaction. Targeting the odorant receptors (ORs) may thus provide avenues towards improved pest control. Such an approach requires information on the function of ORs and their interactions with ligands, which is also essential for understanding the functional evolution of these receptors. Hence, we aimed to identify a high-quality complement of ORs from the destructive spruce bark beetle Ips typographus (Coleoptera, Curculionidae, Scolytinae) and analyze their antennal expression and phylogenetic relationships with ORs from other beetles. Using 68 biologically relevant test compounds, we next aimed to functionally characterize ecologically important ORs, using two systems for heterologous expression. Our final aim was to gain insight into the ligand-OR interaction of the functionally characterized ORs, using a combination of computational and experimental methods. RESULTS We annotated 73 ORs from an antennal transcriptome of I. typographus and report the functional characterization of two ORs (ItypOR46 and ItypOR49), which are responsive to single enantiomers of the common bark beetle pheromone compounds ipsenol and ipsdienol, respectively. Their responses and antennal expression correlate with the specificities, localizations, and/or abundances of olfactory sensory neurons detecting these enantiomers. We use homology modeling and molecular docking to predict their binding sites. Our models reveal a likely binding cleft lined with residues that previously have been shown to affect the responses of insect ORs. Within this cleft, the active ligands are predicted to specifically interact with residues Tyr84 and Thr205 in ItypOR46. The suggested importance of these residues in the activation by ipsenol is experimentally supported through site-directed mutagenesis and functional testing, and hydrogen bonding appears key in pheromone binding. CONCLUSIONS The emerging insight into ligand binding in the two characterized ItypORs has a general importance for our understanding of the molecular and functional evolution of the insect OR gene family. Due to the ecological importance of the characterized receptors and widespread use of ipsenol and ipsdienol in bark beetle chemical communication, these ORs should be evaluated for their potential use in pest control and biosensors to detect bark beetle infestations.
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Affiliation(s)
- Jothi K Yuvaraj
- Department of Biology, Lund University, SE-223 62, Lund, Sweden
| | | | - Yonathan Sonntag
- Division of Biochemistry and Structural Biology, Department of Chemistry, Lund University, SE-223 62, Lund, Sweden
| | - Xiao-Qing Hou
- Department of Biology, Lund University, SE-223 62, Lund, Sweden
| | - Ewald Grosse-Wilde
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, 07745, Jena, Germany
- Present address: Faculty of Forestry & Wood Sci, Excellent Team for Mitigation, Czech University Life Sci Prague, Kamycka 129, Prague 6, 16521, Suchdol, Czech Republic
| | - Aleš Machara
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Gilead Sciences and IOCB Research Center, Flemingovo n. 2, 166 10, Prague 6, Czech Republic
| | - Dan-Dan Zhang
- Department of Biology, Lund University, SE-223 62, Lund, Sweden
| | - Bill S Hansson
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, 07745, Jena, Germany
| | - Urban Johanson
- Division of Biochemistry and Structural Biology, Department of Chemistry, Lund University, SE-223 62, Lund, Sweden
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21
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Yuvaraj JK, Roberts RE, Sonntag Y, Hou XQ, Grosse-Wilde E, Machara A, Zhang DD, Hansson BS, Johanson U, Löfstedt C, Andersson MN. Putative ligand binding sites of two functionally characterized bark beetle odorant receptors. BMC Biol 2021. [PMID: 33499862 DOI: 10.1101/2020.03.07.980797] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023] Open
Abstract
BACKGROUND Bark beetles are major pests of conifer forests, and their behavior is primarily mediated via olfaction. Targeting the odorant receptors (ORs) may thus provide avenues towards improved pest control. Such an approach requires information on the function of ORs and their interactions with ligands, which is also essential for understanding the functional evolution of these receptors. Hence, we aimed to identify a high-quality complement of ORs from the destructive spruce bark beetle Ips typographus (Coleoptera, Curculionidae, Scolytinae) and analyze their antennal expression and phylogenetic relationships with ORs from other beetles. Using 68 biologically relevant test compounds, we next aimed to functionally characterize ecologically important ORs, using two systems for heterologous expression. Our final aim was to gain insight into the ligand-OR interaction of the functionally characterized ORs, using a combination of computational and experimental methods. RESULTS We annotated 73 ORs from an antennal transcriptome of I. typographus and report the functional characterization of two ORs (ItypOR46 and ItypOR49), which are responsive to single enantiomers of the common bark beetle pheromone compounds ipsenol and ipsdienol, respectively. Their responses and antennal expression correlate with the specificities, localizations, and/or abundances of olfactory sensory neurons detecting these enantiomers. We use homology modeling and molecular docking to predict their binding sites. Our models reveal a likely binding cleft lined with residues that previously have been shown to affect the responses of insect ORs. Within this cleft, the active ligands are predicted to specifically interact with residues Tyr84 and Thr205 in ItypOR46. The suggested importance of these residues in the activation by ipsenol is experimentally supported through site-directed mutagenesis and functional testing, and hydrogen bonding appears key in pheromone binding. CONCLUSIONS The emerging insight into ligand binding in the two characterized ItypORs has a general importance for our understanding of the molecular and functional evolution of the insect OR gene family. Due to the ecological importance of the characterized receptors and widespread use of ipsenol and ipsdienol in bark beetle chemical communication, these ORs should be evaluated for their potential use in pest control and biosensors to detect bark beetle infestations.
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Affiliation(s)
- Jothi K Yuvaraj
- Department of Biology, Lund University, SE-223 62, Lund, Sweden
| | | | - Yonathan Sonntag
- Division of Biochemistry and Structural Biology, Department of Chemistry, Lund University, SE-223 62, Lund, Sweden
| | - Xiao-Qing Hou
- Department of Biology, Lund University, SE-223 62, Lund, Sweden
| | - Ewald Grosse-Wilde
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, 07745, Jena, Germany
- Present address: Faculty of Forestry & Wood Sci, Excellent Team for Mitigation, Czech University Life Sci Prague, Kamycka 129, Prague 6, 16521, Suchdol, Czech Republic
| | - Aleš Machara
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Gilead Sciences and IOCB Research Center, Flemingovo n. 2, 166 10, Prague 6, Czech Republic
| | - Dan-Dan Zhang
- Department of Biology, Lund University, SE-223 62, Lund, Sweden
| | - Bill S Hansson
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, 07745, Jena, Germany
| | - Urban Johanson
- Division of Biochemistry and Structural Biology, Department of Chemistry, Lund University, SE-223 62, Lund, Sweden
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22
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Orädd F, Andersson M. Tracking Membrane Protein Dynamics in Real Time. J Membr Biol 2021; 254:51-64. [PMID: 33409541 PMCID: PMC7936944 DOI: 10.1007/s00232-020-00165-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 12/11/2020] [Indexed: 12/14/2022]
Abstract
Abstract Membrane proteins govern critical cellular processes and are central to human health and associated disease. Understanding of membrane protein function is obscured by the vast ranges of structural dynamics—both in the spatial and time regime—displayed in the protein and surrounding membrane. The membrane lipids have emerged as allosteric modulators of membrane protein function, which further adds to the complexity. In this review, we discuss several examples of membrane dependency. A particular focus is on how molecular dynamics (MD) simulation have aided to map membrane protein dynamics and how enhanced sampling methods can enable observing the otherwise inaccessible biological time scale. Also, time-resolved X-ray scattering in solution is highlighted as a powerful tool to track membrane protein dynamics, in particular when combined with MD simulation to identify transient intermediate states. Finally, we discuss future directions of how to further develop this promising approach to determine structural dynamics of both the protein and the surrounding lipids. Graphic Abstract ![]()
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Affiliation(s)
- Fredrik Orädd
- Department of Chemistry, Umeå University, Umeå, Sweden
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23
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Cholesterol content in the membrane promotes key lipid-protein interactions in a pentameric serotonin-gated ion channel. Biointerphases 2021; 15:061018. [PMID: 33397116 DOI: 10.1116/6.0000561] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs), embedded in the lipid membranes of nerve cells, mediate fast synaptic transmission and are major pharmaceutical targets. Because of their complexity and the limited knowledge of their structure, their working mechanisms have still to be fully unraveled at the molecular level. Over the past few years, evidence that the lipid membrane may modulate the function of membrane proteins, including pLGICs, has emerged. Here, we investigate, by means of molecular dynamics simulations, the behavior of the lipid membrane at the interface with the 5-HT3A receptor (5-HT3AR), a representative pLGIC which is the target of nausea-suppressant drugs, in a nonconductive state. Three lipid compositions are studied, spanning different concentrations of the phospholipids, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine, and of cholesterol, hence a range of viscosities. A variety of lipid interactions and persistent binding events to different parts of the receptor are revealed in the investigated models, providing snapshots of the dynamical environment at the membrane-receptor interface. Some of these events result in lipid intercalation within the transmembrane domain, and others reach out to protein key sections for signal transmission and receptor activation, such as the Cys-loop and the M2-M3 loop. In particular, phospholipids, with their long hydrophobic tails, play an important role in these interactions, potentially providing a bridge between these two structures. A higher cholesterol content appears to promote lipid persistent binding to the receptor.
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24
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Thompson MJ, Baenziger JE. Ion channels as lipid sensors: from structures to mechanisms. Nat Chem Biol 2020; 16:1331-1342. [PMID: 33199909 DOI: 10.1038/s41589-020-00693-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 10/08/2020] [Indexed: 12/18/2022]
Abstract
Ion channels play critical roles in cellular function by facilitating the flow of ions across the membrane in response to chemical or mechanical stimuli. Ion channels operate in a lipid bilayer, which can modulate or define their function. Recent technical advancements have led to the solution of numerous ion channel structures solubilized in detergent and/or reconstituted into lipid bilayers, thus providing unprecedented insight into the mechanisms underlying ion channel-lipid interactions. Here, we describe how ion channel structures have evolved to respond to both lipid modulators and lipid activators to control the electrical activities of cells, highlighting diverse mechanisms and common themes.
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Affiliation(s)
- Mackenzie J Thompson
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada
| | - John E Baenziger
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada.
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25
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Thompson MJ, Baenziger JE. Structural basis for the modulation of pentameric ligand-gated ion channel function by lipids. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183304. [DOI: 10.1016/j.bbamem.2020.183304] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 03/20/2020] [Accepted: 04/05/2020] [Indexed: 10/24/2022]
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