1
|
Cardoso FC, Schmit M, Kuiper MJ, Lewis RJ, Tuck KL, Duggan PJ. Inhibition of N-type calcium ion channels by tricyclic antidepressants - experimental and theoretical justification for their use for neuropathic pain. RSC Med Chem 2022; 13:183-195. [PMID: 35308021 PMCID: PMC8864487 DOI: 10.1039/d1md00331c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 12/20/2021] [Indexed: 11/21/2022] Open
Abstract
A number of tricyclic antidepressants (TCAs) are commonly prescribed off-label for the treatment of neuropathic pain. The blockade of neuronal calcium ion channels is often invoked to partially explain the analgesic activity of TCAs, but there has been very limited experimental or theoretical evidence reported to support this assertion. The N-type calcium ion channel (CaV2.2) is a well-established target for the treatment of neuropathic pain and in this study a series of eleven TCAs and two closely related drugs were shown to be moderately effective inhibitors of this channel when endogenously expressed in the SH-SY5Y neuroblastoma cell line. A homology model of the channel, which matches closely a recently reported Cryo-EM structure, was used to investigate via docking and molecular dynamics experiments the possible mode of inhibition of CaV2.2 channels by TCAs. Two closely related binding modes, that occur in the channel cavity that exists between the selectivity filter and the internal gate, were identified. The TCAs are predicted to position themselves such that their ammonium side chains interfere with the selectivity filter, with some, such as amitriptyline, also appearing to hinder the channel's ability to open. This study provides the most comprehensive evidence to date that supports the notion that the blockade of neuronal calcium ion channels by TCAs is at least partially responsible for their analgesic effect.
Collapse
Affiliation(s)
- Fernanda C Cardoso
- Institute for Molecular Bioscience, The University of Queensland St Lucia QLD 4072 Australia
| | - Matthieu Schmit
- School of Chemistry, Monash University Victoria 3800 Australia
- CSIRO Manufacturing Research Way Clayton Victoria 3168 Australia
| | | | - Richard J Lewis
- Institute for Molecular Bioscience, The University of Queensland St Lucia QLD 4072 Australia
| | - Kellie L Tuck
- School of Chemistry, Monash University Victoria 3800 Australia
| | - Peter J Duggan
- CSIRO Manufacturing Research Way Clayton Victoria 3168 Australia
- College of Science and Engineering, Flinders University Adelaide South Australia 5042 Australia
| |
Collapse
|
2
|
Sameera, Shah FA, Rashid S. Conformational ensembles of non-peptide ω-conotoxin mimetics and Ca +2 ion binding to human voltage-gated N-type calcium channel Ca v2.2. Comput Struct Biotechnol J 2020; 18:2357-2372. [PMID: 32994894 PMCID: PMC7498737 DOI: 10.1016/j.csbj.2020.08.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 08/24/2020] [Accepted: 08/26/2020] [Indexed: 02/07/2023] Open
Abstract
Chronic neuropathic pain is the most complex and challenging clinical problem of a population that sets a major physical and economic burden at the global level. Ca2+-permeable channels functionally orchestrate the processing of pain signals. Among them, N-type voltage-gated calcium channels (VGCC) hold prominent contribution in the pain signal transduction and serve as prime targets for synaptic transmission block and attenuation of neuropathic pain. Here, we present detailed in silico analysis to comprehend the underlying conformational changes upon Ca2+ ion passage through Cav2.2 to differentially correlate subtle transitions induced via binding of a conopeptide-mimetic alkylphenyl ether-based analogue MVIIA. Interestingly, pronounced conformational changes were witnessed at the proximal carboxyl-terminus of Cav2.2 that attained an upright orientation upon Ca+2 ion permeability. Moreover, remarkable changes were observed in the architecture of channel tunnel. These findings illustrate that inhibitor binding to Cav2.2 may induce more narrowing in the pore size as compared to Ca2+ binding through modulating the hydrophilicity pattern at the selectivity region. A significant reduction in the tunnel volume at the selectivity filter and its enhancement at the activation gate of Ca+2-bound Cav2.2 suggests that ion binding modulates the outward splaying of pore-lining S6 helices to open the voltage gate. Overall, current study delineates dynamic conformational ensembles in terms of Ca+2 ion and MVIIA-associated structural implications in the Cav2.2 that may help in better therapeutic intervention to chronic and neuropathic pain management.
Collapse
Affiliation(s)
- Sameera
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan
| | - Fawad Ali Shah
- Riphah Institute of Pharmaceutical Sciences, Riphah International University, Islamabad, Pakistan
| | - Sajid Rashid
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan
| |
Collapse
|
3
|
Morales Duque H, Campos Dias S, Franco OL. Structural and Functional Analyses of Cone Snail Toxins. Mar Drugs 2019; 17:md17060370. [PMID: 31234371 PMCID: PMC6628382 DOI: 10.3390/md17060370] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 06/16/2019] [Accepted: 06/17/2019] [Indexed: 12/12/2022] Open
Abstract
Cone snails are marine gastropod mollusks with one of the most powerful venoms in nature. The toxins, named conotoxins, must act quickly on the cone snails´ prey due to the fact that snails are extremely slow, reducing their hunting capability. Therefore, the characteristics of conotoxins have become the object of investigation, and as a result medicines have been developed or are in the trialing process. Conotoxins interact with transmembrane proteins, showing specificity and potency. They target ion channels and ionotropic receptors with greater regularity, and when interaction occurs, there is immediate physiological decompensation. In this review we aimed to evaluate the structural features of conotoxins and the relationship with their target types.
Collapse
Affiliation(s)
- Harry Morales Duque
- Centro de Análises Proteômicas e Bioquímicas, Programa de Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília-DF 70.790-160, Brazil.
| | - Simoni Campos Dias
- Centro de Análises Proteômicas e Bioquímicas, Programa de Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília-DF 70.790-160, Brazil.
| | - Octávio Luiz Franco
- Centro de Análises Proteômicas e Bioquímicas, Programa de Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília-DF 70.790-160, Brazil.
- S-inova Biotech, Programa de Pós-Graduação em Biotecnologia, Universidade Católica Dom Bosco, Campo Grande-MS 79.117-900, Brazil.
| |
Collapse
|
4
|
Mansbach RA, Travers T, McMahon BH, Fair JM, Gnanakaran S. Snails In Silico: A Review of Computational Studies on the Conopeptides. Mar Drugs 2019; 17:E145. [PMID: 30832207 PMCID: PMC6471681 DOI: 10.3390/md17030145] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 02/21/2019] [Accepted: 02/22/2019] [Indexed: 12/26/2022] Open
Abstract
Marine cone snails are carnivorous gastropods that use peptide toxins called conopeptides both as a defense mechanism and as a means to immobilize and kill their prey. These peptide toxins exhibit a large chemical diversity that enables exquisite specificity and potency for target receptor proteins. This diversity arises in terms of variations both in amino acid sequence and length, and in posttranslational modifications, particularly the formation of multiple disulfide linkages. Most of the functionally characterized conopeptides target ion channels of animal nervous systems, which has led to research on their therapeutic applications. Many facets of the underlying molecular mechanisms responsible for the specificity and virulence of conopeptides, however, remain poorly understood. In this review, we will explore the chemical diversity of conopeptides from a computational perspective. First, we discuss current approaches used for classifying conopeptides. Next, we review different computational strategies that have been applied to understanding and predicting their structure and function, from machine learning techniques for predictive classification to docking studies and molecular dynamics simulations for molecular-level understanding. We then review recent novel computational approaches for rapid high-throughput screening and chemical design of conopeptides for particular applications. We close with an assessment of the state of the field, emphasizing important questions for future lines of inquiry.
Collapse
Affiliation(s)
- Rachael A Mansbach
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
| | - Timothy Travers
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
| | - Benjamin H McMahon
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
| | - Jeanne M Fair
- Biosecurity and Public Health Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
| | - S Gnanakaran
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
| |
Collapse
|
5
|
Dong M, Wang F, Yan Z, Yu S, Wei J, Wu Q, Liu Z, Tang Y, Ding J, Dai Q. Structure-Activity Analysis of N-Type Calcium Channel Inhibitor SO-3. Biochemistry 2018; 57:6349-6355. [PMID: 30281282 DOI: 10.1021/acs.biochem.8b00803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
As an ω-conopeptide originally discovered from Conus striatus, SO-3 contains 25 amino acid residues and three disulfide bridges. Our previous study has shown that this peptide possesses potent analgesic activity in rodent pain models (mouse and rat), and it specifically inhibits an N-type calcium ion channel (Cav2.2). In the study presented here, we investigated the key amino acid residues for their inhibitory activity against Cav2.2 expressed in HEK 293 cells and analgesic activity in mice. To improve the inhibitory activity of SO-3, we also evaluated the effects of some amino acid residues derived from the corresponding residues of ω-peptide MVIIA, CVID, or GVIA. Our data reveal that Lys6, Ile11, and Asn14 are the important functional amino acid residues for SO-3. The replacement of some amino acid residues of SO-3 in loop 1 with the corresponding residues of CVID and GVIA improved the inhibitory activity of SO-3. The binding mode of Cav2.2 with SO-3 amino acids in loop 1 and loop 2 may be somewhat different from that of MVIIA. This study expanded our knowledge of the structure-activity relationship of ω-peptides and provided a new strategy for improving the potency of Cav2.2 inhibitors.
Collapse
Affiliation(s)
- Minxing Dong
- Beijing Institute of Biotechnology , Beijing 100071 , China
| | - Fei Wang
- Beijing Institute of Biotechnology , Beijing 100071 , China
| | - Zhenzhen Yan
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Shuo Yu
- Beijing Institute of Biotechnology , Beijing 100071 , China
| | - Juanjuan Wei
- Beijing Institute of Biotechnology , Beijing 100071 , China
| | - Qiaoling Wu
- Beijing Institute of Biotechnology , Beijing 100071 , China
| | - Zhuguo Liu
- Beijing Institute of Biotechnology , Beijing 100071 , China
| | - Yifei Tang
- Beijing Institute of Biotechnology , Beijing 100071 , China
| | - Jiuping Ding
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Qiuyun Dai
- Beijing Institute of Biotechnology , Beijing 100071 , China
| |
Collapse
|
6
|
Chen F, Huang W, Jiang T, Yu R. Determination of the μ-Conotoxin PIIIA Specificity Against Voltage-Gated Sodium Channels from Binding Energy Calculations. Mar Drugs 2018; 16:E153. [PMID: 29735899 PMCID: PMC5983284 DOI: 10.3390/md16050153] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 04/25/2018] [Accepted: 04/28/2018] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium (NaV) channels generate and propagate action potentials in excitable cells, and several NaV subtypes have become important targets for pain management. The μ-conotoxins inhibit subtypes of the NaV with varied specificity but often lack of specificity to interested subtypes. Engineering the selectivity of the μ-conotoxins presents considerable complexity and challenge, as it involves the optimization of their binding affinities to multiple highly conserved NaV subtypes. In this study, a model of NaV1.4 bound with μ-conotoxin PIIIA complex was constructed using homology modeling, docking, molecular dynamic simulations and binding energy calculations. The accuracy of this model was confirmed based on the experimental mutagenesis data. The complex models of PIIIA bound with varied subtypes of NaV1.x (x = 1, 2, 3, 5, 6, 7, 8, or 9) were built using NaV1.4/PIIIA complex as a template, and refined using molecular dynamic simulations. The binding affinities of PIIIA to varied subtypes of NaV1.x (x = 1 to 9) were calculated using the Molecular Mechanics Generalized Born/Surface Area (MMGB/SA) and umbrella sampling, and were compared with the experimental values. The binding affinities calculated using MMGB/SA and umbrella sampling are correlated with the experimental values, with the former and the latter giving correlation coefficient of 0.41 (R²) and 0.68 (R²), respectively. Binding energy decomposition suggests that conserved and nonconserved residues among varied NaV subtypes have a synergistic effect on the selectivity of PIIIA.
Collapse
Affiliation(s)
- Fangling Chen
- 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.
| | - Wenxin Huang
- 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.
| |
Collapse
|
7
|
Schilling R, Fink RHA, Fischer WB. Interaction of ions with the luminal sides of wild-type and mutated skeletal muscle ryanodine receptors. J Mol Model 2016; 22:37. [PMID: 26781665 DOI: 10.1007/s00894-015-2906-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 12/28/2015] [Indexed: 12/22/2022]
Abstract
Ryanodine receptors (RyRs) are the largest known ion channels, and are of central importance for the release of Ca(2+) from the sarco/endoplasmic reticulum (SR/ER) in a variety of cells. In cardiac and skeletal muscle cells, contraction is triggered by the release of Ca(2+) into the cytoplasm and thus depends crucially on correct RyR function. In this work, in silico mutants of the RyR pore were generated and MD simulations were conducted to examine the impact of the mutations on the Ca(2+) distribution. The Ca(2+) distribution pattern on the luminal side of the RyR was most affected by G4898R, D4899Q, E4900Q, R4913E, and D4917A mutations. MD simulations with our wild-type model and various ion species showed a preference for Ca(2+) over other cations at the luminal pore entrance. This Ca(2+)-accumulating characteristic of the luminal RyR side may be essential to the conductance properties of the channel.
Collapse
Affiliation(s)
- Roman Schilling
- Medical Biophysics Group, Institute of Physiology and Pathophysiology, University of Heidelberg, 69120, Heidelberg, Germany
| | - Rainer H A Fink
- Medical Biophysics Group, Institute of Physiology and Pathophysiology, University of Heidelberg, 69120, Heidelberg, Germany
| | - Wolfgang B Fischer
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, 155, Li-Non St., Sec. 2, Taipei, 112, Taiwan.
- Biophotonics & Molecular Imaging Research Center (BMIRC), National Yang-Ming University, Taipei, 112, Taiwan.
| |
Collapse
|
8
|
Yu R, Tabassum N, Jiang T. Investigation of α-conotoxin unbinding using umbrella sampling. Bioorg Med Chem Lett 2016; 26:1296-300. [PMID: 26796065 DOI: 10.1016/j.bmcl.2016.01.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 01/05/2016] [Accepted: 01/07/2016] [Indexed: 11/15/2022]
Abstract
α-Conotoxins, a class of short and disulfide rich peptide toxins, specifically and potently block nicotinic acetylcholine receptors (nAChRs). In this study umbrella sampling was performed to study the unbinding pathways and potential of mean force (PMF) of α-conotoxin ImI and PNIA(A10L,D14K). Our results suggest that (i) the unbinding pathways of ImI and PNIA(A10L,D14K) are similar despite of their different disulfide framework and structure, and (ii) α-conotoxin unbinding requires large conformation perturbation of the C-loop and the backbone flexibility of the C-loop can affect the binding or unbinding kinetics of the α-conotoxins. In addition, (iii) umbrella sampling gave correct ranking of the binding affinities of ImI and PNIA(A10L,D14K) indicating its efficacy on prediction of the binding affinities of α-conotoxins and implicating its potential application in design of more potent α-conotoxin analogs.
Collapse
Affiliation(s)
- Rilei Yu
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China.
| | - Nargis Tabassum
- 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.
| |
Collapse
|
9
|
Wang F, Yan Z, Liu Z, Wang S, Wu Q, Yu S, Ding J, Dai Q. Molecular basis of toxicity of N-type calcium channel inhibitor MVIIA. Neuropharmacology 2015; 101:137-45. [PMID: 26344359 DOI: 10.1016/j.neuropharm.2015.08.047] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 08/31/2015] [Accepted: 08/31/2015] [Indexed: 10/23/2022]
Abstract
MVIIA (ziconotide) is a specific inhibitor of N-type calcium channel, Cav2.2. It is derived from Cone snail and currently used for the treatment of severe chronic pains in patients unresponsive to opioid therapy. However, MVIIA produces severe side-effects, including dizziness, nystagmus, somnolence, abnormal gait, and ataxia, that limit its wider application. We previously identified a novel inhibitor of Cav2.2, ω-conopeptide SO-3, which possesses similar structure and analgesic activity to MVIIA's. To investigate the key residues for MVIIA toxicity, MVIIA/SO-3 hybrids and MVIIA variants carrying mutations in its loop 2 were synthesized. The substitution of MVIIA's loop 1 with the loop 1 of SO-3 resulted in significantly reduced Cav2.2 binding activity in vitro; the replacement of MVIIA loop 2 by the loop 2 of SO-3 not only enhanced the peptide/Cav2.2 binding but also decreased its toxicity on goldfish, attenuated mouse tremor symptom, spontaneous locomotor activity, and coordinated locomotion function. Further mutation analysis and molecular calculation revealed that the toxicity of MVIIA mainly arose from Met(12) in the loop 2, and this residue inserts into a hydrophobic hole (Ile(300), Phe(302) and Leu(305)) located between repeats II and III of Cav2.2. The combinative mutations of the loop 2 of MVIIA or other ω-conopeptides may be used for future development of more effective Cav2.2 inhibitors with lower side effects.
Collapse
Affiliation(s)
- Fei Wang
- Beijing Institute of Biotechnology, Beijing 100071, China
| | - Zhenzhen Yan
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zhuguo Liu
- Beijing Institute of Biotechnology, Beijing 100071, China
| | - Sheng Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Qiaoling Wu
- Beijing Institute of Biotechnology, Beijing 100071, China
| | - Shuo Yu
- Beijing Institute of Biotechnology, Beijing 100071, China
| | - Jiuping Ding
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
| | - Qiuyun Dai
- Beijing Institute of Biotechnology, Beijing 100071, China.
| |
Collapse
|
10
|
Chen R, Chung SH. Binding modes of two scorpion toxins to the voltage-gated potassium channel kv1.3 revealed from molecular dynamics. Toxins (Basel) 2014; 6:2149-61. [PMID: 25054783 PMCID: PMC4113748 DOI: 10.3390/toxins6072149] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 07/08/2014] [Accepted: 07/10/2014] [Indexed: 12/13/2022] Open
Abstract
Molecular dynamics (MD) simulations are used to examine the binding modes of two scorpion toxins, margatoxin (MgTx) and hongotoxin (HgTx), to the voltage gated K+ channel, Kv1.3. Using steered MD simulations, we insert either Lys28 or Lys35 of the toxins into the selectivity filter of the channel. The MgTx-Kv1.3 complex is stable when the side chain of Lys35 from the toxin occludes the channel filter, suggesting that Lys35 is the pore-blocking residue for Kv1.3. In this complex, Lys28 of the toxin forms one additional salt bridge with Asp449 just outside the filter of the channel. On the other hand, HgTx forms a stable complex with Kv1.3 when the side chain of Lys28 but not Lys35 protrudes into the filter of the channel. A survey of all the possible favorable binding modes of HgTx-Kv1.3 is carried out by rotating the toxin at 3° intervals around the channel axis while the position of HgTx-Lys28 relative to the filter is maintained. We identify two possible favorable binding modes: HgTx-Arg24 can interact with either Asp433 or Glu420 on the vestibular wall of the channel. The dissociation constants calculated from the two binding modes of HgTx-Kv1.3 differ by approximately 20 fold, suggesting that the two modes are of similar energetics.
Collapse
Affiliation(s)
- Rong Chen
- Research School of Biology, Australian National University, Canberra, ACT 0200, Australia.
| | - Shin-Ho Chung
- Research School of Biology, Australian National University, Canberra, ACT 0200, Australia.
| |
Collapse
|
11
|
Molecular dynamics simulations of scorpion toxin recognition by the Ca(2+)-activated potassium channel KCa3.1. Biophys J 2014; 105:1829-37. [PMID: 24138859 DOI: 10.1016/j.bpj.2013.08.046] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 08/26/2013] [Accepted: 08/30/2013] [Indexed: 02/06/2023] Open
Abstract
The Ca(2+)-activated channel of intermediate-conductance (KCa3.1) is a target for antisickling and immunosuppressant agents. Many small peptides isolated from animal venoms inhibit KCa3.1 with nanomolar affinities and are promising drug scaffolds. Although the inhibitory effect of peptide toxins on KCa3.1 has been examined extensively, the structural basis of toxin-channel recognition has not been understood in detail. Here, the binding modes of two selected scorpion toxins, charybdotoxin (ChTx) and OSK1, to human KCa3.1 are examined in atomic detail using molecular dynamics (MD) simulations. Employing a homology model of KCa3.1, we first determine conduction properties of the channel using Brownian dynamics and ascertain that the simulated results are in accord with experiment. The model structures of ChTx-KCa3.1 and OSK1-KCa3.1 complexes are then constructed using MD simulations biased with distance restraints. The ChTx-KCa3.1 complex predicted from biased MD is consistent with the crystal structure of ChTx bound to a voltage-gated K(+) channel. The dissociation constants (Kd) for the binding of both ChTx and OSK1 to KCa3.1 determined experimentally are reproduced within fivefold using potential of mean force calculations. Making use of the knowledge we gained by studying the ChTx-KCa3.1 complex, we attempt to enhance the binding affinity of the toxin by carrying out a theoretical mutagenesis. A mutant toxin, in which the positions of two amino acid residues are interchanged, exhibits a 35-fold lower Kd value for KCa3.1 than that of the wild-type. This study provides insight into the key molecular determinants for the high-affinity binding of peptide toxins to KCa3.1, and demonstrates the power of computational methods in the design of novel toxins.
Collapse
|
12
|
Schilling R, Fink RH, Fischer WB. MD simulations of the central pore of ryanodine receptors and sequence comparison with 2B protein from coxsackie virus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1122-31. [DOI: 10.1016/j.bbamem.2013.12.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 11/16/2013] [Accepted: 12/12/2013] [Indexed: 02/08/2023]
|
13
|
Mechanism of μ-conotoxin PIIIA binding to the voltage-gated Na+ channel NaV1.4. PLoS One 2014; 9:e93267. [PMID: 24676211 PMCID: PMC3968119 DOI: 10.1371/journal.pone.0093267] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 03/03/2014] [Indexed: 12/19/2022] Open
Abstract
Several subtypes of voltage-gated Na+ (NaV) channels are important targets for pain management. μ-Conotoxins isolated from venoms of cone snails are potent and specific blockers of different NaV channel isoforms. The inhibitory effect of μ-conotoxins on NaV channels has been examined extensively, but the mechanism of toxin specificity has not been understood in detail. Here the known structure of μ-conotoxin PIIIA and a model of the skeletal muscle channel NaV1.4 are used to elucidate elements that contribute to the structural basis of μ-conotoxin binding and specificity. The model of NaV1.4 is constructed based on the crystal structure of the bacterial NaV channel, NaVAb. Six different binding modes, in which the side chain of each of the basic residues carried by the toxin protrudes into the selectivity filter of NaV1.4, are examined in atomic detail using molecular dynamics simulations with explicit solvent. The dissociation constants (Kd) computed for two selected binding modes in which Lys9 or Arg14 from the toxin protrudes into the filter of the channel are within 2 fold; both values in close proximity to those determined from dose response data for the block of NaV currents. To explore the mechanism of PIIIA specificity, a double mutant of NaV1.4 mimicking NaV channels resistant to μ-conotoxins and tetrodotoxin is constructed and the binding of PIIIA to this mutant channel examined. The double mutation causes the affinity of PIIIA to reduce by two orders of magnitude.
Collapse
|