1
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Li Z, Chan KC, Nickels JD, Cheng X. Molecular Dynamics Refinement of Open State Serotonin 5-HT 3A Receptor Structures. J Chem Inf Model 2023; 63:1196-1207. [PMID: 36757760 DOI: 10.1021/acs.jcim.2c01441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Pentameric ligand-gated ion channels play an important role in mediating fast neurotransmissions. As a member of this receptor family, cation-selective 5-HT3 receptors are a clinical target for treating nausea and vomiting associated with chemotherapy and radiation therapy (Thompson and Lummis, 2006). Multiple cryo-electron microscopy (cryo-EM) structures of 5-HT3 receptors have been determined in distinct functional states (e.g., open, closed, etc.) (Basak et al., 2018; Basak et al., 2018; Polovinkin et al., 2018; Zhang et al., 2015). However, recent work has shown that the transmembrane pores of the open 5-HT3 receptor structures rapidly collapse and become artificially asymmetric in molecular dynamics (MD) simulations. To avoid this hydrophobic collapse, Dämgen and Biggin developed an equilibration protocol that led to a stable open state structure of the glycine receptor in MD simulations (Dämgen and Biggin, 2020). However, the protocol failed to yield open-like structures of the 5-HT3 receptor in our simulations. Here, we present a refined equilibration protocol that involves the rearrangement of the transmembrane helices to achieve stable open state structures of the 5-HT3 receptor that allow both water and ion permeation through the channel. Notably, channel gating is mediated through collective movement of the transmembrane helices, involving not only pore lining M2 helices but also their cross-talk with the adjacent M1 and M3 helices. Thus, the successful application of our refined equilibration protocol underscores the importance of the conformational coupling between the transmembrane helices in stabilizing open-like structures of the 5-HT3 receptor.
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Affiliation(s)
- Zoe Li
- Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy at The Ohio State University, Columbus, Ohio 43210, United States
| | - Kevin C Chan
- Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy at The Ohio State University, Columbus, Ohio 43210, United States
| | - Jonathan D Nickels
- Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Xiaolin Cheng
- Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy at The Ohio State University, Columbus, Ohio 43210, United States.,Translational Data Analytics Institute (TDAI) at The Ohio State University, Columbus, Ohio 43210, United States
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2
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Dixon T, MacPherson D, Mostofian B, Dauzhenka T, Lotz S, McGee D, Shechter S, Shrestha UR, Wiewiora R, McDargh ZA, Pei F, Pal R, Ribeiro JV, Wilkerson T, Sachdeva V, Gao N, Jain S, Sparks S, Li Y, Vinitsky A, Zhang X, Razavi AM, Kolossváry I, Imbriglio J, Evdokimov A, Bergeron L, Zhou W, Adhikari J, Ruprecht B, Dickson A, Xu H, Sherman W, Izaguirre JA. Predicting the structural basis of targeted protein degradation by integrating molecular dynamics simulations with structural mass spectrometry. Nat Commun 2022; 13:5884. [PMID: 36202813 PMCID: PMC9537307 DOI: 10.1038/s41467-022-33575-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 09/20/2022] [Indexed: 11/09/2022] Open
Abstract
Targeted protein degradation (TPD) is a promising approach in drug discovery for degrading proteins implicated in diseases. A key step in this process is the formation of a ternary complex where a heterobifunctional molecule induces proximity of an E3 ligase to a protein of interest (POI), thus facilitating ubiquitin transfer to the POI. In this work, we characterize 3 steps in the TPD process. (1) We simulate the ternary complex formation of SMARCA2 bromodomain and VHL E3 ligase by combining hydrogen-deuterium exchange mass spectrometry with weighted ensemble molecular dynamics (MD). (2) We characterize the conformational heterogeneity of the ternary complex using Hamiltonian replica exchange simulations and small-angle X-ray scattering. (3) We assess the ubiquitination of the POI in the context of the full Cullin-RING Ligase, confirming experimental ubiquitinomics results. Differences in degradation efficiency can be explained by the proximity of lysine residues on the POI relative to ubiquitin.
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Affiliation(s)
- Tom Dixon
- Roivant Discovery, New York City, NY, 10036, USA
- Department of Computational Mathematics, Science, and Engineering, Michigan State University, East Lansing, MI, 48824, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA
| | | | | | | | - Samuel Lotz
- Roivant Discovery, New York City, NY, 10036, USA
| | - Dwight McGee
- Roivant Discovery, New York City, NY, 10036, USA
| | | | | | | | | | - Fen Pei
- Roivant Discovery, New York City, NY, 10036, USA
| | - Rajat Pal
- Roivant Discovery, New York City, NY, 10036, USA
| | | | | | | | - Ning Gao
- Roivant Discovery, New York City, NY, 10036, USA
| | - Shourya Jain
- Roivant Discovery, New York City, NY, 10036, USA
| | | | - Yunxing Li
- Roivant Discovery, New York City, NY, 10036, USA
| | | | - Xin Zhang
- Roivant Discovery, New York City, NY, 10036, USA
| | | | | | | | | | | | | | | | | | - Alex Dickson
- Department of Computational Mathematics, Science, and Engineering, Michigan State University, East Lansing, MI, 48824, USA.
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA.
| | - Huafeng Xu
- Roivant Discovery, New York City, NY, 10036, USA.
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3
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Bustamante C, Muskus C, Ochoa R. Rational computational approaches to predict novel drug candidates against leishmaniasis. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 2022. [DOI: 10.1016/bs.armc.2022.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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4
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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: 11] [Impact Index Per Article: 3.7] [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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5
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Kochert M, Nocek BP, Habeeb Mohammad TS, Gild E, Lovato K, Heath TK, Holz RC, Olsen KW, Becker DP. Atomic-Resolution 1.3 Å Crystal Structure, Inhibition by Sulfate, and Molecular Dynamics of the Bacterial Enzyme DapE. Biochemistry 2021; 60:908-917. [PMID: 33721990 DOI: 10.1021/acs.biochem.0c00926] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report the atomic-resolution (1.3 Å) X-ray crystal structure of an open conformation of the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE, EC 3.5.1.18) from Neisseria meningitidis. This structure [Protein Data Bank (PDB) entry 5UEJ] contains two bound sulfate ions in the active site that mimic the binding of the terminal carboxylates of the N-succinyl-l,l-diaminopimelic acid (l,l-SDAP) substrate. We demonstrated inhibition of DapE by sulfate (IC50 = 13.8 ± 2.8 mM). Comparison with other DapE structures in the PDB demonstrates the flexibility of the interdomain connections of this protein. This high-resolution structure was then utilized as the starting point for targeted molecular dynamics experiments revealing the conformational change from the open form to the closed form that occurs when DapE binds l,l-SDAP and cleaves the amide bond. These simulations demonstrated closure from the open to the closed conformation, the change in RMS throughout the closure, and the independence in the movement of the two DapE subunits. This conformational change occurred in two phases with the catalytic domains moving toward the dimerization domains first, followed by a rotation of catalytic domains relative to the dimerization domains. Although there were no targeting forces, the substrate moved closer to the active site and bound more tightly during the closure event.
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Affiliation(s)
- Matthew Kochert
- Department of Chemistry and Biochemistry, Loyola University Chicago, 1032 West Sheridan Road, Chicago, Illinois 60660, United States
| | - Boguslaw P Nocek
- The Center for Structural Genomics of Infectious Diseases, Computation Institute, The University of Chicago, Chicago, Illinois 60637, United States
| | - Thahani S Habeeb Mohammad
- Department of Chemistry and Biochemistry, Loyola University Chicago, 1032 West Sheridan Road, Chicago, Illinois 60660, United States
| | - Elliot Gild
- Department of Chemistry and Biochemistry, Loyola University Chicago, 1032 West Sheridan Road, Chicago, Illinois 60660, United States
| | - Kaitlyn Lovato
- Department of Chemistry and Biochemistry, Loyola University Chicago, 1032 West Sheridan Road, Chicago, Illinois 60660, United States
| | - Tahirah K Heath
- Department of Chemistry and Biochemistry, Loyola University Chicago, 1032 West Sheridan Road, Chicago, Illinois 60660, United States
| | - Richard C Holz
- Department of Chemistry, Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| | - Kenneth W Olsen
- Department of Chemistry and Biochemistry, Loyola University Chicago, 1032 West Sheridan Road, Chicago, Illinois 60660, United States
| | - Daniel P Becker
- Department of Chemistry and Biochemistry, Loyola University Chicago, 1032 West Sheridan Road, Chicago, Illinois 60660, United States
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6
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Gulsevin A. Nicotinic receptor pharmacology in silico: Insights and challenges. Neuropharmacology 2020; 177:108257. [PMID: 32738311 DOI: 10.1016/j.neuropharm.2020.108257] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 07/16/2020] [Accepted: 07/26/2020] [Indexed: 02/07/2023]
Abstract
Nicotinic acetylcholine receptors (nAChR) are homo- or hetero-pentameric ligand-gated ion channels of the Cys-loop superfamily and play important roles in the nervous system and muscles. Studies on nAChR benefit from in silico modeling due to the lack of high-resolution structures for most receptor subtypes and challenges in experiments addressing the complex mechanism of activation involving allosteric sites. Although there is myriad of computational modeling studies on nAChR, the multitude of the methods and parameters used in these studies makes modeling nAChR a daunting task, particularly for the non-experts in the field. To address this problem, the modeling literature on Torpedo nAChR and α7 nAChR were focused on as examples of heteromeric and homomeric nAChR, and the key in silico modeling studies between the years 1995-2019 were concisely reviewed. This was followed by a critical analysis of these studies by comparing the findings with each other and with the emerging experimental and computational data on nAChR. Based on these critical analyses, suggestions were made to guide the future researchers in the field of in silico modeling of nAChR. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.
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Affiliation(s)
- Alican Gulsevin
- Department of Chemistry, Vanderbilt University, Nashville, TN, USA, 37221.
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7
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Dong C, Kern NR, Anderson KR, Zhang XF, Miwa JM, Im W. Dynamics and Interactions of GPI-Linked lynx1 Protein with/without Nicotinic Acetylcholine Receptor in Membrane Bilayers. J Phys Chem B 2020; 124:4017-4025. [PMID: 32208709 DOI: 10.1021/acs.jpcb.0c00159] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) participate in diverse biological processes, such as mood, learning, and addiction. Glycosylphosphatidylinositol-linked lynx1 is an allosteric modulator of nAChR function, including shifts in agonist sensitivity, reduced desensitization, and slower recovery from desensitization. This modulation is thought to be achieved by lynx1's interaction with nAChR subunits, particularly at the α4:α4 interface. In this study, we used molecular modeling and simulation to study the structure, dynamics, and interactions of lynx1 when bound to nAChRs, as well as unbound, monomeric lynx1 in membranes. Though lynx1 structures are similar in both states, its dynamics is more restricted in the bound state than in the unbound one. When bound, interactions between lynx1 and nAChR are observed to be maintained throughout the simulations. Of particular note, lynx1 demonstrates prolonged interactions with the receptor C-loop in one of the nAChR α4 subunits, a region important for agonist binding and possibly the transition between open/closed states. During interactions with lynx1, an α4 C-loop tends to be restricted in either a closed or open state, whereas the C-loop state transitions are more evident when lynx1 is unbound. Interestingly, the conformational change of the C-loop is stochastic, suggesting that lynx1 can influence nAChR (critical for its multimodal action), for instance, by shifting its agonist sensitivity and recovery from desensitization.
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Affiliation(s)
- Chuqiao Dong
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Nathan R Kern
- Department of Computer Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Kristin R Anderson
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - X Frank Zhang
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, United States.,Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Julie M Miwa
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Wonpil Im
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015, United States.,Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States.,Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
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8
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Gulsevin A, Papke RL, Horenstein N. In Silico Modeling of the α7 Nicotinic Acetylcholine Receptor: New Pharmacological Challenges Associated with Multiple Modes of Signaling. Mini Rev Med Chem 2020; 20:841-864. [PMID: 32000651 PMCID: PMC8719523 DOI: 10.2174/1389557520666200130105256] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Revised: 11/06/2019] [Accepted: 11/07/2019] [Indexed: 12/13/2022]
Abstract
The α7 nicotinic acetylcholine receptor is a homopentameric ion-channel of the Cys-loop superfamily characterized by its low probability of opening, high calcium permeability, and rapid desensitization. The α7 receptor has been targeted for the treatment of the cognitive symptoms of schizophrenia, depression, and Alzheimer's disease, but it is also involved in inflammatory modulation as a part of the cholinergic anti-inflammatory pathway. Despite its functional importance, in silico studies of the α7 receptor cannot produce a general model explaining the structural features of receptor activation, nor predict the mode of action for various ligand classes. Two particular problems in modeling the α7 nAChR are the absence of a high-resolution structure and the presence of five potentially nonequivalent orthosteric ligand binding sites. There is wide variability regarding the templates used for homology modeling, types of ligands investigated, simulation methods, and simulation times. However, a systematic survey focusing on the methodological similarities and differences in modeling α7 has not been done. In this work, we make a critical analysis of the modeling literature of α7 nAChR by comparing the findings of computational studies with each other and with experimental studies under the main topics of structural studies, ligand binding studies, and comparisons with other nAChR. In light of our findings, we also summarize current problems in the field and make suggestions for future studies concerning modeling of the α7 receptor.
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Affiliation(s)
- Alican Gulsevin
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, United States
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610, United States
| | - Nicole Horenstein
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, United States
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9
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Terejko K, Kaczor PT, Michałowski MA, Dąbrowska A, Mozrzymas JW. The C loop at the orthosteric binding site is critically involved in GABA A receptor gating. Neuropharmacology 2019; 166:107903. [PMID: 31972511 DOI: 10.1016/j.neuropharm.2019.107903] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 11/15/2019] [Accepted: 12/02/2019] [Indexed: 02/02/2023]
Abstract
GABAA receptors (GABAARs) play a crucial role in mammalian adult brain inhibition. The dysfunction of GABAergic drive is related to such disorders as epilepsy, schizophrenia, and depression. Substantial progress has recently been made in describing the static structure of GABAARs, but the molecular mechanisms that underlie the activation process remain elusive. The C loop of the GABAAR structure shows the largest movement upon ligand binding to the orthosteric binding site, a phenomenon that is referred to as "capping." The C loop is known to be involved in agonist binding, but its role in the gating of Cys-loop receptors is still debated. Herein, we investigated this issue by analyzing the impact of a β2F200 residue mutation of the C loop on gating properties of α1β2γ2 GABAARs. Extensive analyses and the modeling of current responses to saturating agonist application demonstrated that this mutation strongly affected preactivation, opening, closing and desensitization, i.e. all considered gating steps. Single-channel analysis revealed that the β2F200 mutation slowed all shut time components, and open times were shortened. Model fitting of these single-channel data further confirmed that the β2F200 mutation strongly affected all of the gating characteristics. We also found that this mutation altered receptor sensitivity to the benzodiazepine flurazepam, which was attributable to a change in preactivation kinetics. In silico analysis indicated that the β2F200 mutation resulted in distortion of the C loop structure, causing the movement of its tip from the binding site. Altogether, we provide the first evidence that C loop critically controls GABAAR gating.
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Affiliation(s)
- Katarzyna Terejko
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland.
| | - Przemysław T Kaczor
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland
| | - Michał A Michałowski
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland; Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335, Wrocław, Poland
| | - Agnieszka Dąbrowska
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland; Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335, Wrocław, Poland.
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10
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Xu X, Liang J, Zhang Z, Jiang T, Yu R. Blockade of Human α7 Nicotinic Acetylcholine Receptor by α-Conotoxin ImI Dendrimer: Insight from Computational Simulations. Mar Drugs 2019; 17:md17050303. [PMID: 31126085 PMCID: PMC6563025 DOI: 10.3390/md17050303] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 05/10/2019] [Accepted: 05/17/2019] [Indexed: 12/22/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that are involved in fast synaptic transmission and mediated physiological activities in the nervous system. α-Conotoxin ImI exhibits subtype-specific blockade towards homomeric α7 and α9 receptors. In this study, we established a method to build a 2×ImI-dendrimer/h (human) α7 nAChR model, and based on this model, we systematically investigated the molecular interactions between the 2×ImI-dendrimer and hα7 nAChR. Our results suggest that the 2×ImI-dendrimer possessed much stronger potency towards hα7 nAChR than the α-ImI monomer and demonstrated that the linker between α-ImI contributed to the potency of the 2×ImI-dendrimer by forming a stable hydrogen-bond network with hα7 nAChR. Overall, this study provides novel insights into the binding mechanism of α-ImI dendrimer to hα7 nAChR, and the methodology reported here opens an avenue for the design of more selective dendrimers with potential usage as drug/gene carriers, macromolecular drugs, and molecular probes.
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Affiliation(s)
- Xiaoxiao Xu
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China.
- Laboratory for Marine Drugs and Bioproducts of Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.
| | - Jiazhen Liang
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China.
- Laboratory for Marine Drugs and Bioproducts of Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.
| | - Zheyu Zhang
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China.
| | - Tao Jiang
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China.
- Laboratory for Marine Drugs and Bioproducts of Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.
| | - Rilei Yu
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China.
- Laboratory for Marine Drugs and Bioproducts of Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.
- Innovation Center for Marine Drug Screening & Evaluation, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.
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11
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Tripathy S, Zheng W, Auerbach A. A single molecular distance predicts agonist binding energy in nicotinic receptors. J Gen Physiol 2019; 151:452-464. [PMID: 30635370 PMCID: PMC6445573 DOI: 10.1085/jgp.201812212] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 11/07/2018] [Accepted: 12/11/2018] [Indexed: 11/20/2022] Open
Abstract
Agonists turn on receptors because they bind more strongly to active (R*) versus resting (R) conformations of their target sites. Here, to explore how agonists activate neuromuscular acetylcholine receptors, we built homology models of R and R* neurotransmitter binding sites, docked ligands to those sites, ran molecular dynamics simulations to relax ("equilibrate") the structures, measured binding site structural parameters, and correlated them with experimental agonist binding energies. Each binding pocket is a pyramid formed by five aromatic amino acids and covered partially by loop C. We found that in R* versus R, loop C is displaced outward, the pocket is smaller and skewed, the agonist orientation is reversed, and a key nitrogen atom in the agonist is closer to the pocket center (distance dx) and a tryptophan pair but farther from αY190. Of these differences, the change in dx shows the largest correlation with experimental binding energy and provides a good estimate of agonist affinity, efficacy, and efficiency. Indeed, concentration-response curves can be calculated from just dx values. The contraction and twist of the binding pocket upon activation resemble gating rearrangements of the extracellular domain of related receptors at a smaller scale.
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Affiliation(s)
- Sushree Tripathy
- Department of Physics, State University of New York, Buffalo, Buffalo, NY
| | - Wenjun Zheng
- Department of Physics, State University of New York, Buffalo, Buffalo, NY
| | - Anthony Auerbach
- Department of Physiology and Biophysics, State University of New York, Buffalo, Buffalo, NY
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12
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Chiodo L, Malliavin TE, Giuffrida S, Maragliano L, Cottone G. Closed-Locked and Apo-Resting State Structures of the Human α7 Nicotinic Receptor: A Computational Study. J Chem Inf Model 2018; 58:2278-2293. [PMID: 30359518 DOI: 10.1021/acs.jcim.8b00412] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nicotinic acetylcholine receptors, belonging to the Cys-loop superfamily of ligand-gated ion channels (LGICs), are membrane proteins present in neurons and at neuromuscular junctions. They are responsible for signal transmission, and their function is regulated by neurotransmitters, agonists, and antagonists drugs. A detailed knowledge of their conformational transition in response to ligand binding is critical to understanding the basis of ligand-receptor interaction, in view of new pharmacological approaches to control receptor activity. However, the scarcity of experimentally derived structures of human channels makes this perspective extremely challenging. To contribute overcoming this issue, we have recently reported structural models for the open and the desensitized states of the human α7 nicotinic receptor. Here, we provide all-atom structural models of the same receptor in two different nonconductive states. The first structure, built via homology modeling and relaxed with extensive Molecular Dynamics simulations, represents the receptor bound to the natural antagonist α-conotoxin ImI. After comparison with available experimental data and computational models of other eukaryotic LGICs, we deem it consistent with the "closed-locked" state. The second model, obtained with simulations from the spontaneous relaxation of the open, agonist-bound α7 structure after ligand removal, recapitulates the characteristics of the apo-resting state of the receptor. These results add to our previous work on the active and desensitized state conformations, contributing to the structural characterization of the conformational landscape of the human α7 receptor and suggesting benchmarks to discriminate among conformations found in experiments or in simulations of LGICs. In particular key interactions at the interface between the extracellular domain and the transmembrane domain are identified, that could be critical to the α7 receptor function.
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Affiliation(s)
- Letizia Chiodo
- Department of Engineering , Campus Bio-Medico University of Rome , Via Á. del Portillo 21 , 00128 Rome , Italy
| | - Thérèse E Malliavin
- Institut Pasteur and CNRS UMR 3528, Unité de Bioinformatique Structurale , 25-28 rue du Dr Roux , 75015 Paris , France.,Centre de Bioinformatique, Biostatistique et Biologie Intégrative , Institut Pasteur and CNRS USR 3756 , 25-28 rue du Dr Roux , 75015 Paris , France
| | - Sergio Giuffrida
- Department of Physics and Chemistry , University of Palermo , Viale delle Scienze Ed. 17 , 90128 Palermo , Italy
| | - Luca Maragliano
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe) , Istituto Italiano di Tecnologia , Largo Rosanna Benzi, 10 , 16132 Genoa , Italy.,IRCCS Ospedale Policlinico San Martino , Largo Rosanna Benzi 10 , 16132 Genoa , Italy
| | - Grazia Cottone
- Department of Physics and Chemistry , University of Palermo , Viale delle Scienze Ed. 17 , 90128 Palermo , Italy
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13
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Ayan M, Essiz S. The neural γ 2α 1β 2α 1β 2 gamma amino butyric acid ion channel receptor: structural analysis of the effects of the ivermectin molecule and disulfide bridges. J Mol Model 2018; 24:206. [PMID: 30008086 DOI: 10.1007/s00894-018-3739-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 06/27/2018] [Indexed: 12/21/2022]
Abstract
While ~30% of the human genome encodes membrane proteins, only a handful of structures of membrane proteins have been resolved to high resolution. Here, we studied the structure of a member of the Cys-loop ligand gated ion channel protein superfamily of receptors, human type A γ2α1β2α1β2 gamma amino butyric acid receptor complex in a lipid bilayer environment. Studying the correlation between the structure and function of the gamma amino butyric acid receptor may enhance our understanding of the molecular basis of ion channel dysfunctions linked with epilepsy, ataxia, migraine, schizophrenia and other neurodegenerative diseases. The structure of human γ2α1β2α1β2 has been modeled based on the X-ray structure of the Caenorhabditis elegans glutamate-gated chloride channel via homology modeling. The template provided the first inhibitory channel structure for the Cys-loop superfamily of ligand-gated ion channels. The only available template structure before this glutamate-gated chloride channel was a cation selective channel which had very low sequence identity with gamma aminobutyric acid receptor. Here, our aim was to study the effect of structural corrections originating from modeling on a more reliable template structure. The homology model was analyzed for structural properties via a 100 ns molecular dynamics (MD) study. Due to the structural shifts and the removal of an open channel potentiator molecule, ivermectin, from the template structure, helical packing changes were observed in the transmembrane segment. Namely removal of ivermectin molecule caused a closure around the Leu 9 position along the ion channel. In terms of the structural shifts, there are three potential disulfide bridges between the M1 and M3 helices of the γ2 and 2 α1 subunits in the model. The effect of these disulfide bridges was investigated via monitoring the differences in root mean square fluctuations (RMSF) of individual amino acids and principal component analysis of the MD trajectory of the two homology models-one with the disulfide bridge and one with protonated Cys residues. In all subunit types, RMSF of the transmembrane domain helices are reduced in the presence of disulfide bridges. Additionally, loop A, loop F and loop C fluctuations were affected in the extracellular domain. In cross-correlation analysis of the trajectory, the two model structures displayed different coupling in between the M2-M3 linker region, protruding from the membrane, and the β1-β2/D loop and cys-loop regions in the extracellular domain. Correlations of the C loop, which collapses directly over the bound ligand molecule, were also affected by differences in the packing of transmembrane helices. Finally, more localized correlations were observed in the transmembrane helices when disulfide bridges were present in the model. The differences observed in this study suggest that dynamic coupling at the interface of extracellular and ion channel domains differs from the coupling introduced by disulfide bridges in the transmembrane region. We hope that this hypothesis will be tested experimentally in the near future.
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Affiliation(s)
- Meral Ayan
- Bioinformatics and Genetics Department, Faculty of Engineering and Natural Sciences, Kadir Has University, 34083, Fatih, Istanbul, Turkey
| | - Sebnem Essiz
- Bioinformatics and Genetics Department, Faculty of Engineering and Natural Sciences, Kadir Has University, 34083, Fatih, Istanbul, Turkey.
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14
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Molecular mechanism of GPCR-mediated arrestin activation. Nature 2018; 557:452-456. [PMID: 29720655 DOI: 10.1038/s41586-018-0077-3] [Citation(s) in RCA: 137] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 03/06/2018] [Indexed: 12/26/2022]
Abstract
Despite intense interest in discovering drugs that cause G-protein-coupled receptors (GPCRs) to selectively stimulate or block arrestin signalling, the structural mechanism of receptor-mediated arrestin activation remains unclear1,2. Here we reveal this mechanism through extensive atomic-level simulations of arrestin. We find that the receptor's transmembrane core and cytoplasmic tail-which bind distinct surfaces on arrestin-can each independently stimulate arrestin activation. We confirm this unanticipated role of the receptor core, and the allosteric coupling between these distant surfaces of arrestin, using site-directed fluorescence spectroscopy. The effect of the receptor core on arrestin conformation is mediated primarily by interactions of the intracellular loops of the receptor with the arrestin body, rather than the marked finger-loop rearrangement that is observed upon receptor binding. In the absence of a receptor, arrestin frequently adopts active conformations when its own C-terminal tail is disengaged, which may explain why certain arrestins remain active long after receptor dissociation. Our results, which suggest that diverse receptor binding modes can activate arrestin, provide a structural foundation for the design of functionally selective ('biased') GPCR-targeted ligands with desired effects on arrestin signalling.
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15
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King MD, Long T, Pfalmer DL, Andersen TL, McDougal OM. SPIDR: small-molecule peptide-influenced drug repurposing. BMC Bioinformatics 2018; 19:138. [PMID: 29661129 PMCID: PMC5902895 DOI: 10.1186/s12859-018-2153-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Accepted: 04/09/2018] [Indexed: 11/20/2022] Open
Abstract
Background Conventional de novo drug design is costly and time consuming, making it accessible to only the best resourced research organizations. An emergent approach to new drug development is drug repurposing, in which compounds that have already gone through some level of clinical testing are examined for efficacy against diseases divergent than their original application. Repurposing of existing drugs circumvents the time and considerable cost of early stages of drug development, and can be accelerated by using software to screen existing chemical databases to identify suitable drug candidates. Results Small-molecule Peptide-Influenced Drug Repurposing (SPIDR) was developed to identify small molecule drugs that target a specific receptor by exploring the conformational binding space of peptide ligands. SPIDR was tested using the potent and selective 16-amino acid peptide α-conotoxin MII ligand and the α3β2-nicotinic acetylcholine receptor (nAChR) isoform. SPIDR incorporates a genetic algorithm-based, heuristic search procedure, which was used to explore the ligand binding domain of the α3β2-nAChR isoform using a library consisting of 640,000 α-conotoxin MII peptide analogs. The peptides that exhibited the highest affinity for α3β2-nAChR were used as models for a small-molecule structure similarity search of the PubChem Compound database. SPIDR incorporates the SimSearcher utility, which generates shape distribution signatures of molecules and employs multi-level K-means clustering to insure fast database queries. SPIDR identified non-peptide drugs with estimated binding affinities nearly double that of the native α-conotoxin MII peptide. Conclusions SPIDR has been generalized and integrated into DockoMatic v 2.1. This software contains an intuitive graphical interface for peptide mutant screening workflow and facilitates mapping, clustering, and searching of local molecular databases, making DockoMatic a valuable tool for researchers in drug design and repurposing. Electronic supplementary material The online version of this article (10.1186/s12859-018-2153-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Matthew D King
- Department of Chemistry and Biochemistry, Boise State University, Boise, USA
| | - Thomas Long
- Department of Computer Science, Boise State University, Boise, USA
| | - Daniel L Pfalmer
- Biomolecular Sciences Ph.D. Program, Boise State University, Boise, USA
| | | | - Owen M McDougal
- Department of Chemistry and Biochemistry, Boise State University, Boise, USA.
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16
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Competitive docking model for prediction of the human nicotinic acetylcholine receptor α7 binding of tobacco constituents. Oncotarget 2018; 9:16899-16916. [PMID: 29682193 PMCID: PMC5908294 DOI: 10.18632/oncotarget.24458] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 02/01/2018] [Indexed: 12/21/2022] Open
Abstract
The detrimental health effects associated with tobacco use constitute a major public health concern. The addiction associated with nicotine found in tobacco products has led to difficulty in quitting among users. Nicotinic acetylcholine receptors (nAChRs) are the targets of nicotine and are responsible for addiction to tobacco products. However, it is unknown if the other >8000 tobacco constituents are addictive. Since it is time-consuming and costly to experimentally assess addictive potential of such larger number of chemicals, computationally predicting human nAChRs binding is important for in silico evaluation of addiction potential of tobacco constituents and needs structures of human nAChRs. Therefore, we constructed three-dimensional structures of the ligand binding domain of human nAChR α7 subtype and then developed a predictive model based on the constructed structures to predict human nAChR α7 binding activity of tobacco constituents. The predictive model correctly predicted 11 out of 12 test compounds to be binders of nAChR α7. The model is a useful tool for high-throughput screening of potential addictive tobacco constituents. These results could inform regulatory science research by providing a new validated predictive tool using cutting-edge computational methodology to high-throughput screen tobacco additives and constituents for their binding interaction with the human α7 nicotinic receptor. The tool represents a prediction model capable of screening thousands of chemicals found in tobacco products for addiction potential, which improves the understanding of the potential effects of additives.
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17
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Miller H, Zhou Z, Shepherd J, Wollman AJM, Leake MC. Single-molecule techniques in biophysics: a review of the progress in methods and applications. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:024601. [PMID: 28869217 DOI: 10.1088/1361-6633/aa8a02] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Single-molecule biophysics has transformed our understanding of biology, but also of the physics of life. More exotic than simple soft matter, biomatter lives far from thermal equilibrium, covering multiple lengths from the nanoscale of single molecules to up to several orders of magnitude higher in cells, tissues and organisms. Biomolecules are often characterized by underlying instability: multiple metastable free energy states exist, separated by levels of just a few multiples of the thermal energy scale k B T, where k B is the Boltzmann constant and T absolute temperature, implying complex inter-conversion kinetics in the relatively hot, wet environment of active biological matter. A key benefit of single-molecule biophysics techniques is their ability to probe heterogeneity of free energy states across a molecular population, too challenging in general for conventional ensemble average approaches. Parallel developments in experimental and computational techniques have catalysed the birth of multiplexed, correlative techniques to tackle previously intractable biological questions. Experimentally, progress has been driven by improvements in sensitivity and speed of detectors, and the stability and efficiency of light sources, probes and microfluidics. We discuss the motivation and requirements for these recent experiments, including the underpinning mathematics. These methods are broadly divided into tools which detect molecules and those which manipulate them. For the former we discuss the progress of super-resolution microscopy, transformative for addressing many longstanding questions in the life sciences, and for the latter we include progress in 'force spectroscopy' techniques that mechanically perturb molecules. We also consider in silico progress of single-molecule computational physics, and how simulation and experimentation may be drawn together to give a more complete understanding. Increasingly, combinatorial techniques are now used, including correlative atomic force microscopy and fluorescence imaging, to probe questions closer to native physiological behaviour. We identify the trade-offs, limitations and applications of these techniques, and discuss exciting new directions.
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Affiliation(s)
- Helen Miller
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU, United Kingdom
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18
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Dai L, Flechsig H, Yu J. Deciphering Intrinsic Inter-subunit Couplings that Lead to Sequential Hydrolysis of F 1-ATPase Ring. Biophys J 2017; 113:1440-1453. [PMID: 28978438 PMCID: PMC5627347 DOI: 10.1016/j.bpj.2017.08.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 07/31/2017] [Accepted: 08/04/2017] [Indexed: 11/05/2022] Open
Abstract
Rotary sequential hydrolysis of the metabolic machine F1-ATPase is a prominent manifestation of high coordination among multiple chemical sites in ring-shaped molecular machines, and it is also functionally essential for F1 to tightly couple chemical reactions and central γ-shaft rotation. High-speed AFM experiments have identified that sequential hydrolysis is maintained in the F1 stator ring even in the absence of the γ-rotor. To explore the origins of intrinsic sequential performance, we computationally investigated essential inter-subunit couplings on the hexameric ring of mitochondrial and bacterial F1. We first reproduced in stochastic Monte Carlo simulations the experimentally determined sequential hydrolysis schemes by kinetically imposing inter-subunit couplings and following subsequent tri-site ATP hydrolysis cycles on the F1 ring. We found that the key couplings to support the sequential hydrolysis are those that accelerate neighbor-site ADP and Pi release upon a certain ATP binding or hydrolysis reaction. The kinetically identified couplings were then examined in atomistic molecular dynamics simulations at a coarse-grained level to reveal the underlying structural mechanisms. To do that, we enforced targeted conformational changes of ATP binding or hydrolysis to one chemical site on the F1 ring and monitored the ensuing conformational responses of the neighboring sites using structure-based simulations. Notably, we found asymmetrical neighbor-site opening that facilitates ADP release upon enforced ATP binding. We also captured a complete charge-hopping process of the Pi release subsequent to enforced ATP hydrolysis in the neighbor site, confirming recent single-molecule analyses with regard to the role of ATP hydrolysis in F1. Our studies therefore elucidate both the coordinated chemical kinetics and structural dynamics mechanisms underpinning the sequential operation of the F1 ring.
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Affiliation(s)
- Liqiang Dai
- Complex System Research Division, Beijing Computational Science Research Center, Beijing, China
| | - Holger Flechsig
- Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Hiroshima, Japan
| | - Jin Yu
- Complex System Research Division, Beijing Computational Science Research Center, Beijing, China.
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19
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A possible desensitized state conformation of the human α 7 nicotinic receptor: A molecular dynamics study. Biophys Chem 2017; 229:99-109. [DOI: 10.1016/j.bpc.2017.06.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 06/22/2017] [Accepted: 06/22/2017] [Indexed: 11/18/2022]
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20
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Ma Q, Tae HS, Wu G, Jiang T, Yu R. Exploring the Relationship between Nicotinic Acetylcholine Receptor Ligand Size, Efficiency, Efficacy, and C-Loop Opening. J Chem Inf Model 2017; 57:1947-1956. [PMID: 28718646 DOI: 10.1021/acs.jcim.7b00152] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels mediating fundamental physiological activities in the nervous system and have become important targets for drug design. For a long time, the acetylcholine binding protein (AChBP) has been used as a surrogate to study the nAChR structure-function. Taking advantage of more than 100 AChBP crystal structures in the Protein DataBank (PDB), we explored the relationship between the size, efficiency, and efficacy of nAChR ligands and the C-loop movement. We found that the size of the ligand is correlated with the opening of the C-loop, which can be used in selecting AChBP crystal structures with appropriate C-loop opening to be used for nAChR ligand docking. Ligand size and C-loop opening are reversely correlated with the ligand efficiency rather than the binding affinity. Ligand efficiency could be accurately predicted using simple computational docking, giving a correlation coefficients (R2) up to 0.73. The efficacy of nAChR ligands might be related to ligand size, C-loop opening, and ligand efficiency. Results from this study are useful for engineering the binding affinity and efficacy of nAChR ligands.
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Affiliation(s)
- Qianyun Ma
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China , Qingdao 266003, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266003, China
| | - Han-Shen Tae
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong , Wollongong, New South Wales 2522, Australia
| | - Guanzhao Wu
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China , Qingdao 266003, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266003, China
| | - Tao Jiang
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China , Qingdao 266003, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266003, China
| | - Rilei Yu
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China , Qingdao 266003, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266003, China
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21
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Tabassum N, Ma Q, Wu G, Jiang T, Yu R. Exploring the binding energy profiles of full agonists, partial agonists, and antagonists of the α7 nicotinic acetylcholine receptor. J Mol Model 2017; 23:251. [PMID: 28770361 DOI: 10.1007/s00894-017-3419-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 07/13/2017] [Indexed: 02/02/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) belong to the Cys-loop receptor family and are important drug targets for the treatment of neurological diseases. However, the precise determinants of the binding efficacies of ligands for these receptors are unclear. Therefore, in this study, the binding energy profiles of various ligands (full agonists, partial agonists, and antagonists) were quantified by docking those ligands with structural ensembles of the α7 nAChR exhibiting different degrees of C-loop closure. This approximate treatment of interactions suggested that full agonists, partial agonists, and antagonists of the α7 nAChR possess distinctive binding energy profiles. Results from docking revealed that ligand binding efficacy may be related to the capacity of the ligand to stabilize conformational states with a closed C loop.
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Affiliation(s)
- Nargis Tabassum
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao, 266003, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266003, China
| | - Qianyun Ma
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao, 266003, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266003, China
| | - Guanzhao Wu
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao, 266003, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266003, China
| | - Tao Jiang
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao, 266003, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266003, China
| | - Rilei Yu
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao, 266003, China. .,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266003, China.
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22
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King MD, Long T, Andersen T, McDougal OM. Genetic Algorithm Managed Peptide Mutant Screening: Optimizing Peptide Ligands for Targeted Receptor Binding. J Chem Inf Model 2016; 56:2378-2387. [PMID: 28024403 DOI: 10.1021/acs.jcim.6b00095] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
This study demonstrates the utility of genetic algorithms to search exceptionally large and otherwise intractable mutant libraries for sequences with optimal binding affinities for target receptors. The Genetic Algorithm Managed Peptide Mutant Screening (GAMPMS) program was used to search an α-conotoxin (α-CTx) MII mutant library of approximately 41 billion possible peptide sequences for those exhibiting the greatest binding affinity for the α3β2-nicotinic acetylcholine receptor (nAChR) isoform. A series of top resulting peptide ligands with high sequence homology was obtained, with each mutant having an estimated ΔGbind approximately double that of the potent native α-CTx MII ligand. A consensus sequence from the top GAMPMS results was subjected to more rigorous binding free energy calculations by molecular dynamics and compared to α-CTx MII and other related variants for binding with α3β2-nAChR. In this study, the efficiency of GAMPMS to substantially reduce the sample population size through evolutionary selection criteria to produce ligands with higher predicted binding affinity is demonstrated.
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Affiliation(s)
- Matthew D King
- Department of Chemistry and Biochemistry and ‡Department of Computer Science, Boise State University , 1910 University Drive, Boise, Idaho 83725, United States
| | - Thomas Long
- Department of Chemistry and Biochemistry and ‡Department of Computer Science, Boise State University , 1910 University Drive, Boise, Idaho 83725, United States
| | - Timothy Andersen
- Department of Chemistry and Biochemistry and ‡Department of Computer Science, Boise State University , 1910 University Drive, Boise, Idaho 83725, United States
| | - Owen M McDougal
- Department of Chemistry and Biochemistry and ‡Department of Computer Science, Boise State University , 1910 University Drive, Boise, Idaho 83725, United States
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23
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Wu S. Loop-driven conformational transition between the alternative and collapsed form of prethrombin-2: targeted molecular dynamics study. J Biomol Struct Dyn 2016; 35:119-127. [PMID: 27471844 DOI: 10.1080/07391102.2015.1134347] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Two distinct crystal structures of prethrombin-2, the alternative and collapsed forms, are elucidated by X-ray crystallogrphy. We analyzed the conformational transition from the alternative to the collapsed form employing targeted molecular dynamics (TMD) simulation. Despite small RMSD difference in the two X-ray crystal structures, some hydrophobic residues (W60d, W148, W215, and F227) show a significant difference between the two conformations. TMD simulation shows that the four hydrophobic residues undergo concerted movement from dimer to trimer transition via tetramer state in the conformational change from the alternative to the collapsed form. We reveal that the concerted movement of the four hydrophobic residues is controlled by movement of specific loop regions behind. In this paper, we propose a sequential scenario for the conformational transition from the alternative form to the collapsed form, which is partially supported by the mutant W148A simulation.
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Affiliation(s)
- Sangwook Wu
- a Department of Physics , Pukyong National University , Busan 608-737 , Republic of Korea
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24
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Ochoa R, Watowich SJ, Flórez A, Mesa CV, Robledo SM, Muskus C. Drug search for leishmaniasis: a virtual screening approach by grid computing. J Comput Aided Mol Des 2016; 30:541-52. [DOI: 10.1007/s10822-016-9921-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 06/25/2016] [Indexed: 02/05/2023]
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25
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Comitani F, Limongelli V, Molteni C. The Free Energy Landscape of GABA Binding to a Pentameric Ligand-Gated Ion Channel and Its Disruption by Mutations. J Chem Theory Comput 2016; 12:3398-406. [PMID: 27228114 DOI: 10.1021/acs.jctc.6b00303] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pentameric ligand-gated ion channels (pLGICs) of the Cys-loop superfamily are important neuroreceptors that mediate fast synaptic transmission. They are activated by the binding of a neurotransmitter, but the details of this process are still not fully understood. As a prototypical pLGIC, here we choose the insect resistance to dieldrin (RDL) receptor involved in resistance to insecticides and investigate the binding of the neurotransmitter GABA to its extracellular domain at the atomistic level. We achieve this by means of μ-sec funnel-metadynamics simulations, which efficiently enhance the sampling of bound and unbound states by using a funnel-shaped restraining potential to limit the exploration in the solvent. We reveal the sequence of events in the binding process from the capture of GABA from the solvent to its pinning between the charged residues Arg111 and Glu204 in the binding pocket. We characterize the associated free energy landscapes in the wild-type RDL receptor and in two mutant forms, where the key residues Arg111 and Glu204 are mutated to Ala. Experimentally these mutations produce nonfunctional channels, which is reflected in the reduced ligand binding affinities due to the loss of essential interactions. We also analyze the dynamical behavior of the crucial loop C, whose opening allows the access of GABA to the binding site and closure locks the ligand into the protein. The RDL receptor shares structural and functional features with other pLGICs; hence, our work outlines a valuable protocol to study the binding of ligands to pLGICs beyond conventional docking and molecular dynamics techniques.
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Affiliation(s)
- Federico Comitani
- Department of Physics, King's College London , Strand, London WC2R 2LS, United Kingdom
| | - Vittorio Limongelli
- Universitá della Svizzera Italiana (USI) , Faculty of Informatics, Institute of Computational Science - Center for Computational Medicine in Cardiology, via G. Buffi 13, CH-6900 Lugano, Switzerland.,Department of Pharmacy, University of Naples "Federico II" , via D. Montesano 49, I-80131 Naples, Italy
| | - Carla Molteni
- Department of Physics, King's College London , Strand, London WC2R 2LS, United Kingdom
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26
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Study on the Application of the Combination of TMD Simulation and Umbrella Sampling in PMF Calculation for Molecular Conformational Transitions. Int J Mol Sci 2016; 17:ijms17050692. [PMID: 27171075 PMCID: PMC4881518 DOI: 10.3390/ijms17050692] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 04/26/2016] [Accepted: 04/26/2016] [Indexed: 11/16/2022] Open
Abstract
Free energy calculations of the potential of mean force (PMF) based on the combination of targeted molecular dynamics (TMD) simulations and umbrella samplings as a function of physical coordinates have been applied to explore the detailed pathways and the corresponding free energy profiles for the conformational transition processes of the butane molecule and the 35-residue villin headpiece subdomain (HP35). The accurate PMF profiles for describing the dihedral rotation of butane under both coordinates of dihedral rotation and root mean square deviation (RMSD) variation were obtained based on the different umbrella samplings from the same TMD simulations. The initial structures for the umbrella samplings can be conveniently selected from the TMD trajectories. For the application of this computational method in the unfolding process of the HP35 protein, the PMF calculation along with the coordinate of the radius of gyration (Rg) presents the gradual increase of free energies by about 1 kcal/mol with the energy fluctuations. The feature of conformational transition for the unfolding process of the HP35 protein shows that the spherical structure extends and the middle α-helix unfolds firstly, followed by the unfolding of other α-helices. The computational method for the PMF calculations based on the combination of TMD simulations and umbrella samplings provided a valuable strategy in investigating detailed conformational transition pathways for other allosteric processes.
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27
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Xu X, Yan C, Kossmann BR, Ivanov I. Secondary Interaction Interfaces with PCNA Control Conformational Switching of DNA Polymerase PolB from Polymerization to Editing. J Phys Chem B 2016; 120:8379-88. [PMID: 27109703 DOI: 10.1021/acs.jpcb.6b02082] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Replicative DNA polymerases (Pols) frequently possess two distinct DNA processing activities: DNA synthesis (polymerization) and proofreading (3'-5' exonuclease activity). The polymerase and exonuclease reactions are performed alternately and are spatially separated in different protein domains. Thus, the growing DNA primer terminus has to undergo dynamic conformational switching between two distinct functional sites on the polymerase. Furthermore, the transition from polymerization (pol) mode to exonuclease (exo) mode must occur in the context of a DNA Pol holoenzyme, wherein the polymerase is physically associated with processivity factor proliferating cell nuclear antigen (PCNA) and primer-template DNA. The mechanism of this conformational switching and the role that PCNA plays in it have remained obscure, largely due to the dynamic nature of ternary Pol/PCNA/DNA assemblies. Here, we present computational models of ternary assemblies for archaeal polymerase PolB. We have combined all available structural information for the binary complexes with electron microscopy data and have refined atomistic models for ternary PolB/PCNA/DNA assemblies in pol and exo modes using molecular dynamics simulations. In addition to the canonical PIP-box/interdomain connector loop (IDCL) interface of PolB with PCNA, contact analysis of the simulation trajectories revealed new secondary binding interfaces, distinct between the pol and exo states. Using targeted molecular dynamics, we explored the conformational transition from pol to exo mode. We identified a hinge region between the thumb and palm domains of PolB that is critical for conformational switching. With the thumb domain anchored onto the PCNA surface, the neighboring palm domain executed rotational motion around the hinge, bringing the core of PolB down toward PCNA to form a new interface with the clamp. A helix from PolB containing a patch of arginine residues was involved in the binding, locking the complex in the exo mode conformation. Together, these results provide a structural view of how the transition between the pol and exo states of PolB is coordinated through PCNA to achieve efficient proofreading.
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Affiliation(s)
- Xiaojun Xu
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University , Atlanta, Georgia 30302, United States
| | - Chunli Yan
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University , Atlanta, Georgia 30302, United States
| | - Bradley R Kossmann
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University , Atlanta, Georgia 30302, United States
| | - Ivaylo Ivanov
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University , Atlanta, Georgia 30302, United States
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28
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Grazioso G, Sgrignani J, Capelli R, Matera C, Dallanoce C, De Amici M, Cavalli A. Allosteric Modulation of Alpha7 Nicotinic Receptors: Mechanistic Insight through Metadynamics and Essential Dynamics. J Chem Inf Model 2015; 55:2528-39. [PMID: 26569022 DOI: 10.1021/acs.jcim.5b00459] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Increasing attention has recently been devoted to allosteric modulators, as they can provide inherent advantages over classic receptor agonists. In the field of nicotinic receptors (nAChRs), the main advantage is that allosteric modulators can trigger pharmacological responses, limiting receptor desensitization. Most of the known allosteric ligands are "positive allosteric modulators" (PAMs), which increase both sensitivity to receptor agonists and current amplitude. Intriguingly, some allosteric modulators are also able to activate the α7 receptor (α7-nAChR) even in the absence of orthosteric agonists. These compounds have been named "ago-allosteric modulators" and GAT107 has been studied in depth because of its unique mechanism of action. We here investigate by molecular dynamics simulations, metadynamics, and essential dynamics the activation mechanism of α7-nAChR, in the presence of different nicotinic modulators. We determine the free energy profiles associated with the closed-to-open motion of the loop C, and we highlight mechanistic differences observed in the presence of different modulators. In particular, we demonstrate that GAT107 triggers conformational motions and cross-talk similar to those observed when the α7-nACh receptor is in complex with both an agonist and an allosteric modulator.
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Affiliation(s)
- Giovanni Grazioso
- Dipartimento di Scienze Farmaceutiche, Sezione di Chimica Farmaceutica "Pietro Pratesi", Università degli Studi di Milano , Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Jacopo Sgrignani
- Institute of Research in Biomedicine (IRB) , Via Vincenzo Vela 6, 6500 Bellinzona, Switzerland
| | - Romina Capelli
- Dipartimento di Scienze Farmaceutiche, Sezione di Chimica Farmaceutica "Pietro Pratesi", Università degli Studi di Milano , Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Carlo Matera
- Dipartimento di Scienze Farmaceutiche, Sezione di Chimica Farmaceutica "Pietro Pratesi", Università degli Studi di Milano , Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Clelia Dallanoce
- Dipartimento di Scienze Farmaceutiche, Sezione di Chimica Farmaceutica "Pietro Pratesi", Università degli Studi di Milano , Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Marco De Amici
- Dipartimento di Scienze Farmaceutiche, Sezione di Chimica Farmaceutica "Pietro Pratesi", Università degli Studi di Milano , Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Andrea Cavalli
- Drug Discovery and Development-Computation, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genoa, Italy.,Department of Pharmacy and Biotecnology, University of Bologna , Via Belmeloro 6, 40126 Bologna, Italy
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29
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Di Maio D, Chandramouli B, Brancato G. Pathways and Barriers for Ion Translocation through the 5-HT3A Receptor Channel. PLoS One 2015; 10:e0140258. [PMID: 26465896 PMCID: PMC4605793 DOI: 10.1371/journal.pone.0140258] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 09/12/2015] [Indexed: 11/29/2022] Open
Abstract
Pentameric ligand gated ion channels (pLGICs) are ionotropic receptors that mediate fast intercellular communications at synaptic level and include either cation selective (e.g., nAChR and 5-HT3) or anion selective (e.g., GlyR, GABAA and GluCl) membrane channels. Among others, 5-HT3 is one of the most studied members, since its first cloning back in 1991, and a large number of studies have successfully pinpointed protein residues critical for its activation and channel gating. In addition, 5-HT3 is also the target of a few pharmacological treatments due to the demonstrated benefits of its modulation in clinical trials. Nonetheless, a detailed molecular analysis of important protein features, such as the origin of its ion selectivity and the rather low conductance as compared to other channel homologues, has been unfeasible until the recent crystallization of the mouse 5-HT3A receptor. Here, we present extended molecular dynamics simulations and free energy calculations of the whole 5-HT3A protein with the aim of better understanding its ion transport properties, such as the pathways for ion permeation into the receptor body and the complex nature of the selectivity filter. Our investigation unravels previously unpredicted structural features of the 5-HT3A receptor, such as the existence of alternative intersubunit pathways for ion translocation at the interface between the extracellular and the transmembrane domains, in addition to the one along the channel main axis. Moreover, our study offers a molecular interpretation of the role played by an arginine triplet located in the intracellular domain on determining the characteristic low conductance of the 5-HT3A receptor, as evidenced in previous experiments. In view of these results, possible implications on other members of the superfamily are suggested.
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Affiliation(s)
- Danilo Di Maio
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
| | | | - Giuseppe Brancato
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- * E-mail:
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30
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GC JB, Gerstman BS, Chapagain PP. The Role of the Interdomain Interactions on RfaH Dynamics and Conformational Transformation. J Phys Chem B 2015; 119:12750-9. [DOI: 10.1021/acs.jpcb.5b05681] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jeevan B. GC
- Department of Physics, Florida International University, Miami, Florida 33199, United States
| | - Bernard S. Gerstman
- Department of Physics, Florida International University, Miami, Florida 33199, United States
| | - Prem P. Chapagain
- Department of Physics, Florida International University, Miami, Florida 33199, United States
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31
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Zhang Q, Du Y, Zhang J, Xu X, Xue F, Guo C, Huang Y, Lukas RJ, Chang Y. Functional Impact of 14 Single Nucleotide Polymorphisms Causing Missense Mutations of Human α7 Nicotinic Receptor. PLoS One 2015; 10:e0137588. [PMID: 26340537 PMCID: PMC4560414 DOI: 10.1371/journal.pone.0137588] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 08/18/2015] [Indexed: 01/17/2023] Open
Abstract
The α7nicotinic receptor (nAChR) is a major subtype of the nAChRs in the central nervous system, and the receptor plays an important role in brain function. In the dbSNP database, there are 55 single nucleotide polymorphisms (SNPs) that cause missense mutations of the human α7nAChR in the coding region. In this study, we tested the impact of 14 SNPs that cause missense mutations in the agonist binding site or the coupling region between binding site and channel gate on the receptor function. The wild type or mutant receptors were expressed or co-expressed in Xenopus oocytes, and the agonist-induced currents were tested using two-electrode voltage clamp. Our results demonstrated that 6 mutants were nonfunctional, 4 mutants had reduced current expression, and 1 mutants altered ACh and nicotine efficacy in the opposite direction, and one additional mutant had slightly reduced agonist sensitivity. Interestingly, the function of most of these nonfunctional mutants could be rescued by α7nAChR positive allosteric modulator PNU-120596 and agonist-PAM 4BP-TQS. Finally, when coexpressed with the wild type, the nonfunctional mutants could also influence the receptor function. These changes of the receptor properties by the mutations could potentially have an impact on the physiological function of the α7nAChR-mediated cholinergic synaptic transmission and anti-inflammatory effects in the human SNP carriers. Rescuing the nonfunctional mutants could provide a novel way to treat the related disorders.
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Affiliation(s)
- Qinhui Zhang
- Department of Zoology, College of Life Sciences, Sichuan University, Chengdu, Sichuan Province, 610064, China
- Chengdu institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, China
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona 85013, United States of America
| | - Yingjie Du
- University of California Los Angeles, Henry Samueli School of Engineering and Applied Science, Los Angeles, California 90095, United States of America
| | - Jianliang Zhang
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona 85013, United States of America
- Department of Neurobiology, Beijing Institute of Brain Disorders, Capital Medical University, Key Laboratory for Neurodegenerative Disease of the Ministry of Education, Beijing Center of Neural Regeneration and Repair, Beijing Key Laboratory of Brain Major Disorders; State Key Lab Incubation Base, Beijing Neuroscience Disciplines, Beijing 100069, China
| | - Xiaojun Xu
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona 85013, United States of America
| | - Fenqin Xue
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona 85013, United States of America
- Core Facilities for Electrophysiology, Core Facilities Center, Capital Medical University, Beijing 100069, China
| | - Cong Guo
- Department of Zoology, College of Life Sciences, Sichuan University, Chengdu, Sichuan Province, 610064, China
- Chengdu institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, China
| | - Yao Huang
- Department of Obstetrics and Gynecology, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona 85013, United States of America
| | - Ronald J. Lukas
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona 85013, United States of America
| | - Yongchang Chang
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona 85013, United States of America
- * E-mail:
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32
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Yoluk Ö, Lindahl E, Andersson M. Conformational gating dynamics in the GluCl anion-selective chloride channel. ACS Chem Neurosci 2015; 6:1459-67. [PMID: 25992588 DOI: 10.1021/acschemneuro.5b00111] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Cys-loop receptors are central to propagation of signals in the nervous system. The gating of the membrane-spanning pore is triggered by structural rearrangements in the agonist-binding site, located some 50 Å away from the pore. A sequential conformational change, propagating from the ligand-binding site to the pore, has been proposed to govern gating in all Cys-loop receptors. Here, we identify structural and dynamic components of the conformational gating in the eukaryotic glutamate-gated chloride channel (GluCl) by means of molecular dynamics (MD) simulations with and without the l-glutamate agonist bound. A significant increase in pore opening and accompanying hydration is observed in the presence of glutamate. Potential of mean force calculations reveal that the barrier for ion passage drops from 15 kcal/mol to 5-10 kcal/mol with the agonist bound. This appears to be explained by agonist binding that leads to significant changes in the intersubunit hydrogen-bonding pattern, which induce a slight tilt of the extracellular domain relative to the transmembrane domain in the simulations. This rearrangement is subtle, but correspond to the direction of the quaternary twist observed as a key difference between open and closed X-ray structures. While the full reversible gating is still a much slower process, the observed structural dynamics sheds new light on the early stages of how the agonist influences the extracellular domain, how the extracellular domain interacts with the transmembrane domain, and how changes in the transmembrane domain alter the free energy of ion passage.
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Affiliation(s)
- Özge Yoluk
- Science for Life Laboratory, Stockholm and Uppsala, 171 21 Stockholm, Sweden
- Theoretical and Computational Biophysics, Department of Theoretical Physics, KTH Royal Institute of Technology, 106 91 Stockholm, Sweden
| | - Erik Lindahl
- Science for Life Laboratory, Stockholm and Uppsala, 171 21 Stockholm, Sweden
- Theoretical and Computational Biophysics, Department of Theoretical Physics, KTH Royal Institute of Technology, 106 91 Stockholm, Sweden
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 114 18 Stockholm, Sweden
| | - Magnus Andersson
- Science for Life Laboratory, Stockholm and Uppsala, 171 21 Stockholm, Sweden
- Theoretical and Computational Biophysics, Department of Theoretical Physics, KTH Royal Institute of Technology, 106 91 Stockholm, Sweden
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33
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Chiodo L, Malliavin TE, Maragliano L, Cottone G, Ciccotti G. A Structural Model of the Human α7 Nicotinic Receptor in an Open Conformation. PLoS One 2015; 10:e0133011. [PMID: 26208301 PMCID: PMC4514475 DOI: 10.1371/journal.pone.0133011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 06/22/2015] [Indexed: 11/20/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAchRs) are ligand-gated ion channels that regulate chemical transmission at the neuromuscular junction. Structural information is available at low resolution from open and closed forms of an eukaryotic receptor, and at high resolution from other members of the same structural family, two prokaryotic orthologs and an eukaryotic GluCl channel. Structures of human channels however are still lacking. Homology modeling and Molecular Dynamics simulations are valuable tools to predict structures of unknown proteins, however, for the case of human nAchRs, they have been unsuccessful in providing a stable open structure so far. This is due to different problems with the template structures: on one side the homology with prokaryotic species is too low, while on the other the open eukaryotic GluCl proved itself unstable in several MD studies and collapsed to a dehydrated, non-conductive conformation, even when bound to an agonist. Aim of this work is to obtain, by a mixing of state-of-the-art homology and simulation techniques, a plausible prediction of the structure (still unknown) of the open state of human α7 nAChR complexed with epibatidine, from which it is possible to start structural and functional test studies. To prevent channel closure we employ a restraint that keeps the transmembrane pore open, and obtain in this way a stable, hydrated conformation. To further validate this conformation, we run four long, unbiased simulations starting from configurations chosen at random along the restrained trajectory. The channel remains stable and hydrated over the whole runs. This allows to assess the stability of the putative open conformation over a cumulative time of 1 μs, 800 ns of which are of unbiased simulation. Mostly based on the analysis of pore hydration and size, we suggest that the obtained structure has reasonable chances to be (at least one of the possible) structures of the channel in the open conformation.
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Affiliation(s)
- Letizia Chiodo
- Center for Life Nano Science @Sapienza, Istituto Italiano di Tecnologia, Rome, Italy
| | - Thérèse E. Malliavin
- Institut Pasteur and CNRS UMR 3528, Unité de Bioinformatique Structurale, Paris, France
| | - Luca Maragliano
- Center for Synaptic Neuroscience, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Grazia Cottone
- Department of Physics and Chemistry, University of Palermo, Palermo, Italy
- School of Physics, University College Dublin, Dublin, Ireland
| | - Giovanni Ciccotti
- School of Physics, University College Dublin, Dublin, Ireland
- Department of Physics, University of Roma “La Sapienza”, Rome, Italy
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34
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Identification of the Conformational transition pathway in PIP2 Opening Kir Channels. Sci Rep 2015; 5:11289. [PMID: 26063437 PMCID: PMC4462750 DOI: 10.1038/srep11289] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 04/29/2015] [Indexed: 11/08/2022] Open
Abstract
The gating of Kir channels depends critically on phosphatidylinositol 4,5-bisphosphate (PIP2), but the detailed mechanism by which PIP2 regulates Kir channels remains obscure. Here, we performed a series of Targeted molecular dynamics simulations on the full-length Kir2.1 channel and, for the first time, were able to achieve the transition from the closed to the open state. Our data show that with the upward motion of the cytoplasmic domain (CTD) the structure of the C-Linker changes from a loop to a helix. The twisting of the C-linker triggers the rotation of the CTD, which induces a small downward movement of the CTD and an upward motion of the slide helix toward the membrane that pulls the inner helix gate open. At the same time, the rotation of the CTD breaks the interaction between the CD- and G-loops thus releasing the G-loop. The G-loop then bounces away from the CD-loop, which leads to the opening of the G-loop gate and the full opening of the pore. We identified a series of interaction networks, between the N-terminus, CD loop, C linker and G loop one by one, which exquisitely regulates the global conformational changes during the opening of Kir channels by PIP2.
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35
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Wang B, Weng J, Wang W. Substrate binding accelerates the conformational transitions and substrate dissociation in multidrug efflux transporter AcrB. Front Microbiol 2015; 6:302. [PMID: 25918513 PMCID: PMC4394701 DOI: 10.3389/fmicb.2015.00302] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 03/27/2015] [Indexed: 11/25/2022] Open
Abstract
The tripartite efflux pump assembly AcrAB-TolC is the major multidrug resistance transporter in E. coli. The inner membrane transporter AcrB is a homotrimer, energized by the proton movement down the transmembrane electrochemical gradient. The asymmetric crystal structures of AcrB with three monomers in distinct conformational states [access (A), binding (B) and extrusion (E)] support a functional rotating mechanism, in which each monomer of AcrB cycles among the three states in a concerted way. However, the relationship between the conformational changes during functional rotation and drug translocation has not been totally understood. Here, we explored the conformational changes of the AcrB homotrimer during the ABE to BEA transition in different substrate-binding states using targeted MD simulations. It was found that the dissociation of substrate from the distal binding pocket of B monomer is closely related to the concerted conformational changes in the translocation pathway, especially the side chain reorientation of Phe628 and Tyr327. A second substrate binding at the proximal binding pocket of A monomer evidently accelerates the conformational transitions as well as substrate dissociation in B monomer. The acceleration effect of the multi-substrate binding mode provides a molecular explanation for the positive cooperativity observed in the kinetic studies of substrate efflux and deepens our understanding of the functional rotating mechanism of AcrB.
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Affiliation(s)
- Beibei Wang
- Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University Shanghai, China
| | - Jingwei Weng
- Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University Shanghai, China
| | - Wenning Wang
- Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University Shanghai, China ; Institutes of Biomedical Sciences, Fudan University Shanghai, China
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36
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Belfield WJ, Cole DJ, Martin IL, Payne MC, Chau PL. Constrained geometric simulation of the nicotinic acetylcholine receptor. J Mol Graph Model 2014; 52:1-10. [PMID: 24955489 DOI: 10.1016/j.jmgm.2014.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 05/01/2014] [Accepted: 05/02/2014] [Indexed: 10/25/2022]
Abstract
Constrained geometric simulations have been performed for the recently published closed-channel state of the nicotinic acetylcholine receptor. These simulations support the theory that correlated motion in the flexible β-sheet structure of the extracellular domain helps to communicate a "conformational wave", spreading from the acetylcholine binding pocket. Furthermore, we have identified key residues that act at the interface between subunits and between domains that could potentially facilitate rapid communication between the binding site and the transmembrane gate.
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Affiliation(s)
- William J Belfield
- Theory of Condensed Matter Group, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Daniel J Cole
- Theory of Condensed Matter Group, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom; Department of Chemistry, Yale University, New Haven, CT 06520-8107, United States
| | - Ian L Martin
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Mike C Payne
- Theory of Condensed Matter Group, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - P-L Chau
- Bioinformatique Structurale, CNRS UMR 3528, Institut Pasteur, 75724 Paris, France.
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37
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Mohammad Hosseini Naveh Z, Malliavin TE, Maragliano L, Cottone G, Ciccotti G. Conformational changes in acetylcholine binding protein investigated by temperature accelerated molecular dynamics. PLoS One 2014; 9:e88555. [PMID: 24551117 PMCID: PMC3923797 DOI: 10.1371/journal.pone.0088555] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 01/07/2014] [Indexed: 11/19/2022] Open
Abstract
Despite the large number of studies available on nicotinic acetylcholine receptors, a complete account of the mechanistic aspects of their gating transition in response to ligand binding still remains elusive. As a first step toward dissecting the transition mechanism by accelerated sampling techniques, we study the ligand-induced conformational changes of the acetylcholine binding protein (AChBP), a widely accepted model for the full receptor extracellular domain. Using unbiased Molecular Dynamics (MD) and Temperature Accelerated Molecular Dynamics (TAMD) simulations we investigate the AChBP transition between the apo and the agonist-bound state. In long standard MD simulations, both conformations of the native protein are stable, while the agonist-bound structure evolves toward the apo one if the orientation of few key sidechains in the orthosteric cavity is modified. Conversely, TAMD simulations initiated from the native conformations are able to produce the spontaneous transition. With respect to the modified conformations, TAMD accelerates the transition by at least a factor 10. The analysis of some specific residue-residue interactions points out that the transition mechanism is based on the disruption/formation of few key hydrogen bonds. Finally, while early events of ligand dissociation are observed already in standard MD, TAMD accelerates the ligand detachment and, at the highest TAMD effective temperature, it is able to produce a complete dissociation path in one AChBP subunit.
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Affiliation(s)
| | - Therese E. Malliavin
- Institut Pasteur and CNRS UMR 3528, Unité de Bioinformatique Structurale, Paris, France
| | - Luca Maragliano
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Grazia Cottone
- School of Physics, University College Dublin, Dublin, Ireland
- Department of Physics and Chemistry, University of Palermo, Palermo, Italy
- * E-mail:
| | - Giovanni Ciccotti
- School of Physics, University College Dublin, Dublin, Ireland
- Department of Physics, University of Roma “La Sapienza”, Rome, Italy
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38
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Roy A, Perez A, Dill KA, Maccallum JL. Computing the relative stabilities and the per-residue components in protein conformational changes. Structure 2014; 22:168-75. [PMID: 24316402 PMCID: PMC3905753 DOI: 10.1016/j.str.2013.10.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 10/18/2013] [Accepted: 10/21/2013] [Indexed: 11/19/2022]
Abstract
Protein molecules often undergo conformational changes. In order to gain insights into the forces that drive such changes, it would be useful to have a method that computes the per-residue contributions to the conversion free energy. Here, we describe the "confine-convert-release" (CCR) method, which is applicable to large conformational changes. We show that CCR correctly predicts the stable states of several "chameleon" sequences that have previously been challenging for molecular simulations. CCR can often discriminate better from worse predictions of native protein models in critical assessment of protein structure prediction (CASP). We show how the total conversion free energies can be parsed into per-residue free-energy components. Such parsing gives insights into which amino acids are most responsible for given transformations. For example, here we are able to "reverse-engineer" the known design principles of the chameleon proteins. This opens up the possibility for systematic improvements in structure-prediction scoring functions, in the design of protein conformational switches, and in interpreting protein mechanisms at the amino-acid level.
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Affiliation(s)
- Arijit Roy
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Alberto Perez
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Ken A Dill
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA; Department of Physics, Stony Brook University, Stony Brook, NY 11794, USA; Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA.
| | - Justin L Maccallum
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA
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39
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Mori T, Jung J, Sugita Y. Surface-Tension Replica-Exchange Molecular Dynamics Method for Enhanced Sampling of Biological Membrane Systems. J Chem Theory Comput 2013; 9:5629-40. [PMID: 26592297 DOI: 10.1021/ct400445k] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Conformational sampling is fundamentally important for simulating complex biomolecular systems. The generalized-ensemble algorithm, especially the temperature replica-exchange molecular dynamics method (T-REMD), is one of the most powerful methods to explore structures of biomolecules such as proteins, nucleic acids, carbohydrates, and also of lipid membranes. T-REMD simulations have focused on soluble proteins rather than membrane proteins or lipid bilayers, because explicit membranes do not keep their structural integrity at high temperature. Here, we propose a new generalized-ensemble algorithm for membrane systems, which we call the surface-tension REMD method. Each replica is simulated in the NPγT ensemble, and surface tensions in a pair of replicas are exchanged at certain intervals to enhance conformational sampling of the target membrane system. We test the method on two biological membrane systems: a fully hydrated DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine) lipid bilayer and a WALP23-POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) membrane system. During these simulations, a random walk in surface tension space is realized. Large-scale lateral deformation (shrinking and stretching) of the membranes takes place in all of the replicas without collapse of the lipid bilayer structure. There is accelerated lateral diffusion of DPPC lipid molecules compared with conventional MD simulation, and a much wider range of tilt angle of the WALP23 peptide is sampled due to large deformation of the POPC lipid bilayer and through peptide-lipid interactions. Our method could be applicable to a wide variety of biological membrane systems.
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Affiliation(s)
- Takaharu Mori
- RIKEN Quantitative Biology Center, 7-1-26 minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.,RIKEN Theoretical Molecular Science Laboratory, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Jaewoon Jung
- RIKEN Advanced Institute for Computational Science, 7-1-26 minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Yuji Sugita
- RIKEN Quantitative Biology Center, 7-1-26 minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.,RIKEN Theoretical Molecular Science Laboratory, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.,RIKEN Advanced Institute for Computational Science, 7-1-26 minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
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Nys M, Kesters D, Ulens C. Structural insights into Cys-loop receptor function and ligand recognition. Biochem Pharmacol 2013; 86:1042-53. [DOI: 10.1016/j.bcp.2013.07.001] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 07/03/2013] [Accepted: 07/03/2013] [Indexed: 11/28/2022]
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Mallipeddi PL, Pedersen SE, Briggs JM. Interactions of acetylcholine binding site residues contributing to nicotinic acetylcholine receptor gating: role of residues Y93, Y190, K145 and D200. J Mol Graph Model 2013; 44:145-54. [PMID: 23831994 DOI: 10.1016/j.jmgm.2013.05.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 05/24/2013] [Accepted: 05/27/2013] [Indexed: 10/26/2022]
Abstract
The nicotinic acetylcholine receptor exhibits multiple conformational states, resting (channel closed), active (channel open) and desensitized (channel closed). The resting state may be distinguished from the active and desensitized states by the orientation of loop C in the extracellular ligand binding domain (LBD). Homology modeling was used to generate structures of the Torpedo californica α2βδγ nAChR that initially represent the resting state (loop C open) and the desensitized state (loop C closed). Molecular dynamics (MD) simulations were performed on the extracellular LBD on each nAChR conformational state, with and without the agonist anabaseine present in each binding site (the αγ and the αδ sites). Three MD simulations of 10ns each were performed for each of the four conditions. Comparison of dynamics revealed that in the presence of agonist, loop C was drawn inward and attains a more stable conformation. Examination of side-chain interactions revealed that residue αY190 exhibited hydrogen-bonding interactions either with residue αY93 in the ligand binding site or with residue αK145 proximal to the binding site. αK145 also exhibited side chain (salt bridge) interactions with αD200 and main chain interactions with αY93. Residues αW149, αY198, γY116/δT119, γL118/δL121 and γL108/δL111 appear to play the role of stabilizing ligand in the binding site. In MD simulations for the desensitized state, the effect of ligand upon the interactions among αK145, αY190, and αY93 as well as ligand-hydrogen-bonding to αW149 were more pronounced at the αγ interface than at the αδ interface. Differences in affinity for the desensitized state were determined experimentally to be 10-fold. The changes in side chain interactions observed for the two conformations and induced by ligand support a model wherein hydrogen bond interactions between αD200 and αY93 are broken and rearrange to form a salt-bridge between αK145 and αD200 and hydrogen bond interactions between αY93 and αY190 and between αK145 and αY190.
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Affiliation(s)
- Prema L Mallipeddi
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204, USA
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Hao GF, Yang SG, Yang GF, Zhan CG. Computational gibberellin-binding channel discovery unraveling the unexpected perception mechanism of hormone signal by gibberellin receptor. J Comput Chem 2013; 34:2055-64. [PMID: 23765254 DOI: 10.1002/jcc.23355] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 05/01/2013] [Accepted: 05/23/2013] [Indexed: 11/10/2022]
Abstract
Gibberellins (GAs) are phytohormones essential for many developmental processes in plants. In this work, fundamental mechanism of hormone perception by receptor GID1 has been studied by performing computational simulations, revealing a new GA-binding channel of GID1 and a novel hormone perception mechanism involving only one conformational state of GID1. The novel hormone perception mechanism demonstrated here is remarkably different from the previously proposed/speculated mechanism [Murase et al., Nature 2008, 456, 459] involving two conformational states ("OPEN" and "CLOSED") of GID1. According to the new perception mechanism, GA acts as a "conformational stabilizer," rather than the previously speculated "allosteric inducer," to induce the recognition of protein DELLA by GID1. The novel mechanistic insights obtained in this study provide a new starting point for further studies on the detailed molecular mechanisms of GID1 interacting with DELLA and various hormones and for mechanism-based rational design of novel, potent growth regulators that target crops and ornamental plants.
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Affiliation(s)
- Ge-Fei Hao
- Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, People's Republic of China
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Abstract
During the past five years an increasing number of patients have been diagnosed with congenital myasthenic syndromes (CMS) and a number of novel syndromes have been recognized and investigated. This presentation focuses on the CMS caused by defects in choline acetyltransferase, novel fast-channel syndromes that hinder isomerization of the acetylcholine receptor from the closed to the open state, the consequences of deleterious mutations in the intermediate filament linker plectin, altered neuromuscular transmission in a centronuclear myopathy, and two recently identified CMS caused by congenital defects in glycosylation.
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Affiliation(s)
- Andrew G Engel
- Neuromuscular Research Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.
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Nicotinic acetylcholine receptors: From basic science to therapeutics. Pharmacol Ther 2013; 137:22-54. [DOI: 10.1016/j.pharmthera.2012.08.012] [Citation(s) in RCA: 382] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 08/20/2012] [Indexed: 12/14/2022]
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Maffeo C, Bhattacharya S, Yoo J, Wells D, Aksimentiev A. Modeling and simulation of ion channels. Chem Rev 2012; 112:6250-84. [PMID: 23035940 PMCID: PMC3633640 DOI: 10.1021/cr3002609] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Christopher Maffeo
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Swati Bhattacharya
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Jejoong Yoo
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - David Wells
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Aleksei Aksimentiev
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
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Ashby JA, McGonigle IV, Price KL, Cohen N, Comitani F, Dougherty DA, Molteni C, Lummis SCR. GABA binding to an insect GABA receptor: a molecular dynamics and mutagenesis study. Biophys J 2012. [PMID: 23200041 DOI: 10.1016/j.bpj.2012.10.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
RDL receptors are GABA-activated inhibitory Cys-loop receptors found throughout the insect CNS. They are a key target for insecticides. Here, we characterize the GABA binding site in RDL receptors using computational and electrophysiological techniques. A homology model of the extracellular domain of RDL was generated and GABA docked into the binding site. Molecular dynamics simulations predicted critical GABA binding interactions with aromatic residues F206, Y254, and Y109 and hydrophilic residues E204, S176, R111, R166, S176, and T251. These residues were mutated, expressed in Xenopus oocytes, and their functions assessed using electrophysiology. The data support the binding mechanism provided by the simulations, which predict that GABA forms many interactions with binding site residues, the most significant of which are cation-π interactions with F206 and Y254, H-bonds with E204, S205, R111, S176, T251, and ionic interactions with R111 and E204. These findings clarify the roles of a range of residues in binding GABA in the RDL receptor, and also show that molecular dynamics simulations are a useful tool to identify specific interactions in Cys-loop receptors.
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Du J, Dong H, Zhou HX. Size matters in activation/inhibition of ligand-gated ion channels. Trends Pharmacol Sci 2012; 33:482-93. [PMID: 22789930 DOI: 10.1016/j.tips.2012.06.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 06/07/2012] [Accepted: 06/13/2012] [Indexed: 11/18/2022]
Abstract
Cys loop, glutamate, and P2X receptors are ligand-gated ion channels (LGICs) with 5, 4, and 3 protomers, respectively. There is now growing atomic level understanding of their gating mechanisms. Although each family is unique in the architecture of the ligand-binding pocket, the pathway for motions to propagate from ligand-binding domain to transmembrane domain, and the gating motions of the transmembrane domain, there are common features among the LGICs, which are the focus of the present review. In particular, agonists and competitive antagonists apparently induce opposite motions of the binding pocket. A simple way to control the motional direction is ligand size. Agonists, usually small, induce closure of the binding pocket, leading to opening of the channel pore, whereas antagonists, usually large, induce opening of the binding pocket, thereby stabilizing the closed pore. A cross-family comparison of the gating mechanisms of the LGICs, focusing in particular on the role played by ligand size, provides new insight on channel activation/inhibition and design of pharmacological compounds.
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Affiliation(s)
- Juan Du
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
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Kim HW, McIntosh JM. α6 nAChR subunit residues that confer α-conotoxin BuIA selectivity. FASEB J 2012; 26:4102-10. [PMID: 22751014 DOI: 10.1096/fj.12-204487] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) containing α6 and/or α4 subunits modulate the release of dopamine. However, few compounds can effectively discriminate between ligand-binding sites that contain α6 vs. α4 nAChR subunits. Using a chimeric (α6/α4) subunit, we showed that α-conotoxin BuIA binds the extracellular rat α6β2 vs. α4β2 interface with ∼60,000-fold selectivity. Chimeras containing residues from the α6 subunit were inserted into the homologous position of the α4 subunit to identify critical sequence segments. The region between residues 184 and 207 in the α6 subunit accounted for the potency difference. Chimeras within this region followed by point mutations were constructed for further definition. α6 Lys185, Thr187, and Ile188 form a triad of key residues that influence BuIA binding; when these 3 α6 residues were inserted into the α4 subunit, there was an ∼2000-fold increase in toxin potency. We used a crystal structure of BuIA bound to the acetylcholine-binding protein together with the structure of the Torepedo marmorata nAChR to build a homology model of BuIA bound to the interface between α6 and β2 subunits. The results indicate that the triad of α6 residues lies outside the C loop and is distantly located from bound BuIA (>10 Å). This suggests that alterations in potency are not caused by the direct interaction between the triad and BuIA. Instead, alterations in C-loop 3-dimensional structure and/or flexibility may account for differential potency. Thr198 and Tyr205 also contributed to BuIA potency. In addition, Thr198 caused BuIA potency differences between the closely related α6 and α3 subunits. Together, the findings provide insight into differences between the α6 and other α subunits that may be exploited by α-conotoxins to achieve binding selectivity.
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Affiliation(s)
- Hyun-Woo Kim
- Department of Marine Biology, Pukyong National University, Busan, South Korea.
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Abstract
The synapse is a localized neurohumoral contact between a neuron and an effector cell and may be considered the quantum of fast intercellular communication. Analogously, the postsynaptic neurotransmitter receptor may be considered the quantum of fast chemical to electrical transduction. Our understanding of postsynaptic receptors began to develop about a hundred years ago with the demonstration that electrical stimulation of the vagus nerve released acetylcholine and slowed the heart beat. During the past 50 years, advances in understanding postsynaptic receptors increased at a rapid pace, owing largely to studies of the acetylcholine receptor (AChR) at the motor endplate. The endplate AChR belongs to a large superfamily of neurotransmitter receptors, called Cys-loop receptors, and has served as an exemplar receptor for probing fundamental structures and mechanisms that underlie fast synaptic transmission in the central and peripheral nervous systems. Recent studies provide an increasingly detailed picture of the structure of the AChR and the symphony of molecular motions that underpin its remarkably fast and efficient chemoelectrical transduction.
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Affiliation(s)
- Steven M Sine
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
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Shen XM, Brengman JM, Sine SM, Engel AG. Myasthenic syndrome AChRα C-loop mutant disrupts initiation of channel gating. J Clin Invest 2012; 122:2613-21. [PMID: 22728938 DOI: 10.1172/jci63415] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 04/18/2012] [Indexed: 01/19/2023] Open
Abstract
Congenital myasthenic syndromes (CMSs) are neuromuscular disorders that can be caused by defects in ace-tylcholine receptor (AChR) function. Disease-associated point mutants can reveal the unsuspected functional significance of mutated residues. We identified two pathogenic mutations in the extracellular domain of the AChR α subunit (AChRα) in a patient with myasthenic symptoms since birth: a V188M mutation in the C-loop and a heteroallelic G74C mutation in the main immunogenic region. The G74C mutation markedly reduced surface AChR expression in cultured cells, whereas the V188M mutant was expressed robustly but had severely impaired kinetics. Single-channel patch-clamp analysis indicated that V188M markedly decreased the apparent AChR channel opening rate and gating efficiency. Mutant cycle analysis of energetic coupling among conserved residues within or dispersed around the AChRα C-loop revealed that V188 is functionally linked to Y190 in the C-loop and to D200 in β-strand 10, which connects to the M1 transmembrane domain. Furthermore, V188M weakens inter-residue coupling of K145 in β-strand 7 with Y190 and with D200. Cumulatively, these results indicate that V188 of AChRα is part of an interdependent tetrad that contributes to rearrangement of the C-loop during the initial coupling of agonist binding to channel gating.
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Affiliation(s)
- Xin-Ming Shen
- Neuromuscular Research Laboratory, Department of Neurology, Mayo Clinic, Rochester, MN, USA.
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