1
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Gubič Š, Montalbano A, Sala C, Becchetti A, Hendrickx LA, Van Theemsche KM, Pinheiro-Junior EL, Altadonna GC, Peigneur S, Ilaš J, Labro AJ, Pardo LA, Tytgat J, Tomašič T, Arcangeli A, Peterlin Mašič L. Immunosuppressive effects of new thiophene-based K V1.3 inhibitors. Eur J Med Chem 2023; 259:115561. [PMID: 37454520 DOI: 10.1016/j.ejmech.2023.115561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 06/08/2023] [Accepted: 06/08/2023] [Indexed: 07/18/2023]
Abstract
Voltage-gated potassium channel KV1.3 inhibitors have been shown to be effective in preventing T-cell proliferation and activation by affecting intracellular Ca2+ homeostasis. Here, we present the structure-activity relationship, KV1.3 inhibition, and immunosuppressive effects of new thiophene-based KV1.3 inhibitors with nanomolar potency on K+ current in T-lymphocytes and KV1.3 inhibition on Ltk- cells. The new KV1.3 inhibitor trans-18 inhibited KV1.3 -mediated current in phytohemagglutinin (PHA)-activated T-lymphocytes with an IC50 value of 26.1 nM and in mammalian Ltk- cells with an IC50 value of 230 nM. The KV1.3 inhibitor trans-18 also had nanomolar potency against KV1.3 in Xenopus laevis oocytes (IC50 = 136 nM). The novel thiophene-based KV1.3 inhibitors impaired intracellular Ca2+ signaling as well as T-cell activation, proliferation, and colony formation.
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Affiliation(s)
- Špela Gubič
- University of Ljubljana, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, Aškerčeva cesta 7, 1000, Ljubljana, Slovenia
| | - Alberto Montalbano
- University of Florence, Department of Experimental and Clinical Medicine, I-50134, Florence, Italy
| | - Cesare Sala
- University of Florence, Department of Experimental and Clinical Medicine, I-50134, Florence, Italy
| | - Andrea Becchetti
- University of Milano-Bicocca, Department of Biotechnology and Biosciences, Piazza della Scienza 2, I-20126, Milano, Italy
| | - Louise Antonia Hendrickx
- University of Leuven, Toxicology and Pharmacology, Campus Gasthuisberg, Onderwijs en Navorsing 2, Herestraat 49, PO Box 922, 3000, Leuven, Belgium
| | - Kenny M Van Theemsche
- University of Antwerp, Department of Biomedical Sciences, Campus Drie Eiken, Universiteisplein 1, 2610, Wilrijk, Belgium; Ghent University, Department of Basic and Applied Medical Sciences, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Ernesto Lopes Pinheiro-Junior
- University of Leuven, Toxicology and Pharmacology, Campus Gasthuisberg, Onderwijs en Navorsing 2, Herestraat 49, PO Box 922, 3000, Leuven, Belgium
| | | | - Steve Peigneur
- University of Leuven, Toxicology and Pharmacology, Campus Gasthuisberg, Onderwijs en Navorsing 2, Herestraat 49, PO Box 922, 3000, Leuven, Belgium
| | - Janez Ilaš
- University of Ljubljana, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, Aškerčeva cesta 7, 1000, Ljubljana, Slovenia
| | - Alain J Labro
- Ghent University, Department of Basic and Applied Medical Sciences, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Luis A Pardo
- Max-Planck Institute for Experimental Medicine, AG Oncophysiology, Hermann-Rein-Str. 3, 37075, Göttingen, Germany
| | - Jan Tytgat
- University of Leuven, Toxicology and Pharmacology, Campus Gasthuisberg, Onderwijs en Navorsing 2, Herestraat 49, PO Box 922, 3000, Leuven, Belgium
| | - Tihomir Tomašič
- University of Ljubljana, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, Aškerčeva cesta 7, 1000, Ljubljana, Slovenia
| | - Annarosa Arcangeli
- University of Florence, Department of Experimental and Clinical Medicine, I-50134, Florence, Italy.
| | - Lucija Peterlin Mašič
- University of Ljubljana, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, Aškerčeva cesta 7, 1000, Ljubljana, Slovenia.
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2
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Zhao W, Pan L, Stalin A, Xu J, Wu L, Ke X, Chen Y. Inhibitory Effects of 2-Aminoethoxydiphenyl Borate (2-APB) on Three K V1 Channel Currents. MOLECULES (BASEL, SWITZERLAND) 2023; 28:molecules28020871. [PMID: 36677928 PMCID: PMC9865587 DOI: 10.3390/molecules28020871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/11/2023] [Accepted: 01/12/2023] [Indexed: 01/18/2023]
Abstract
2-Aminoethoxydiphenyl borate (2-APB), a boron-containing compound, is a multitarget compound with potential as a drug precursor and exerts various effects in systems of the human body. Ion channels are among the reported targets of 2-APB. The effects of 2-APB on voltage-gated potassium channels (KV) have been reported, but the types of KV channels that 2-APB inhibits and the inhibitory mechanism remain unknown. In this paper, we discovered that 2-APB acted as an inhibitor of three representative human KV1 channels. 2-APB significantly blocked A-type Kv channel KV1.4 in a concentration-dependent manner, with an IC50 of 67.3 μM, while it inhibited the delayed outward rectifier channels KV1.2 and KV1.3, with IC50s of 310.4 μM and 454.9 μM, respectively. Further studies on KV1.4 showed that V549, T551, A553, and L554 at the cavity region and N-terminal played significant roles in 2-APB's effects on the KV1.4 channel. The results also indicated the importance of fast inactivation gating in determining the different effects of 2-APB on three channels. Interestingly, a current facilitation phenomenon by a short prepulse after 2-APB application was discovered for the first time. The docked modeling revealed that 2-APB could form hydrogen bonds with different sites in the cavity region of three channels, and the inhibition constants showed a similar trend to the experimental results. These findings revealed new molecular targets of 2-APB and demonstrated that 2-APB's effects on KV1 channels might be part of the reason for the diverse bioactivities of 2-APB in the human body and in animal models of human disease.
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Affiliation(s)
- Wei Zhao
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China
- The State Key Laboratory of Subtropical Silviculture, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China
| | - Lanying Pan
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China
- The State Key Laboratory of Subtropical Silviculture, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China
| | - Antony Stalin
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Jianwei Xu
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China
- The State Key Laboratory of Subtropical Silviculture, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China
| | - Liren Wu
- Zhejiang Key Laboratory for Laboratory Animal and Safety Research, Hangzhou Medical College, Hangzhou 311300, China
| | - Xianfu Ke
- Zhejiang Key Laboratory for Laboratory Animal and Safety Research, Hangzhou Medical College, Hangzhou 311300, China
- Correspondence: (X.K.); (Y.C.)
| | - Yuan Chen
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China
- The State Key Laboratory of Subtropical Silviculture, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China
- Correspondence: (X.K.); (Y.C.)
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3
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Montero-Domínguez PA, Mares-Sámano S, Garduño-Juárez R. Insight on the interaction between the scorpion toxin blocker Discrepin on potassium voltage-gated channel Kv4.3 by molecular dynamics simulations. J Biomol Struct Dyn 2022:1-10. [PMID: 35916276 DOI: 10.1080/07391102.2022.2106514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Discrepin is a 38-residue α-toxin extracted from the venom of the Venezuelan scorpion Tityus discrepans, which inhibits ionic transit in the voltage-dependent potassium channels (Kv) of A-type current. The effect of specific residues on the IC50 between Discrepine and Kv4.3, the main component of A-type currents, is known; however, the molecular details of the toxin-channel interaction are not known. In this work, we present interaction models between Discrepin (wt) and two peptide variants (V6K/D20K and K13A) on the pore-forming domain of the Kv4.3 channel obtained from homology, docking, and molecular dynamics modeling techniques. The free energy calculations in these models correspond to the order of the experimentally determined IC50 values. Our studies shed light on the role of the K13 residue as responsible for occluding the Kv4.3 selectivity filter and the importance of the V6K mutation in the approach and stabilization of toxin-channel complex interactions.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
| | - Sergio Mares-Sámano
- CONACYT - Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, México
| | - Ramón Garduño-Juárez
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, México
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Design of New Potent and Selective Thiophene-Based K V1.3 Inhibitors and Their Potential for Anticancer Activity. Cancers (Basel) 2022; 14:cancers14112595. [PMID: 35681571 PMCID: PMC9179341 DOI: 10.3390/cancers14112595] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 05/16/2022] [Accepted: 05/17/2022] [Indexed: 02/04/2023] Open
Abstract
Simple Summary In this article, we describe the discovery of a new class of potent and selective thiophene-based inhibitors of the voltage-gated potassium channel KV1.3 and their potential to induce apoptosis and inhibit proliferation. The KV1.3 channel has only recently emerged as a molecular target in cancer therapy. The most potent KV1.3 inhibitor 44 had an IC50 KV1.3 value of 470 nM (oocytes) and 950 nM (Ltk− cells) and appropriate selectivity for other KV channels. New KV1.3 inhibitors significantly inhibited proliferation of Panc-1 cells and KV1.3 inhibitor 4 induced significant apoptosis in tumor spheroids of Colo-357 cells. Abstract The voltage-gated potassium channel KV1.3 has been recognized as a tumor marker and represents a promising new target for the discovery of new anticancer drugs. We designed a novel structural class of KV1.3 inhibitors through structural optimization of benzamide-based hit compounds and structure-activity relationship studies. The potency and selectivity of the new KV1.3 inhibitors were investigated using whole-cell patch- and voltage-clamp experiments. 2D and 3D cell models were used to determine antiproliferative activity. Structural optimization resulted in the most potent and selective KV1.3 inhibitor 44 in the series with an IC50 value of 470 nM in oocytes and 950 nM in Ltk− cells. KV1.3 inhibitor 4 induced significant apoptosis in Colo-357 spheroids, while 14, 37, 43, and 44 significantly inhibited Panc-1 proliferation.
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Genomic Structure of Two Kv1.3 Channel Blockers from Scorpion Mesobuthus eupeus and Sea Anemone Stichodactyla haddoni and Construction of their Chimeric Peptide as a Novel Blocker. Biochem Genet 2021; 60:504-526. [PMID: 34286408 DOI: 10.1007/s10528-021-10109-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 07/06/2021] [Indexed: 10/20/2022]
Abstract
Different toxins acting on Kv1.3 channel have been isolated from animal venom. MeuKTX toxin from Mesobuthus eupeus phillipsi scorpion and shtx-k toxin from Stichodactyla haddoni sea anemone have been identified as two effective Kv1.3 channel blockers. In this work, we characterized the genomic organization of both toxins. MeuKTX gene contains one intron and two exons, similar to the most scorpion toxins. There are a few reports of genomic structure of sea anemone toxins acting on Kv channels. The sequence encoding mature peptide of shtx-k was located in an exon separated by an intron from the coding exon of the propeptide and signal region. In order to make a peptide with more affinity for Kv1.3 channel and greater stability, the shtx-k/ MeuKTX chimeric peptide was designed and constructed using splicing by overlap extension-PCR (SOE-PCR) method. MeuKTX, shtx-k, and shtx-k/MeuKTX were cloned and the expression of the soluble proteins in E. coli was determined. Molecular docking studies indicated more inhibitory effect of shtx-k/MeuKTX on Kv1.3 channel compared to shtx-k and MeuKTX toxins. Key amino acids binding channel from both toxins, also involved in interaction of chimeric peptide with channel. Our results showed that the fusion peptide, shtx-k/MeuKTX could be an effective agent to target Kv1.3 channel.
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Gubič Š, Hendrickx LA, Toplak Ž, Sterle M, Peigneur S, Tomašič T, Pardo LA, Tytgat J, Zega A, Mašič LP. Discovery of K V 1.3 ion channel inhibitors: Medicinal chemistry approaches and challenges. Med Res Rev 2021; 41:2423-2473. [PMID: 33932253 PMCID: PMC8252768 DOI: 10.1002/med.21800] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 03/03/2021] [Accepted: 03/19/2021] [Indexed: 12/12/2022]
Abstract
The KV 1.3 voltage-gated potassium ion channel is involved in many physiological processes both at the plasma membrane and in the mitochondria, chiefly in the immune and nervous systems. Therapeutic targeting KV 1.3 with specific peptides and small molecule inhibitors shows great potential for treating cancers and autoimmune diseases, such as multiple sclerosis, type I diabetes mellitus, psoriasis, contact dermatitis, rheumatoid arthritis, and myasthenia gravis. However, no KV 1.3-targeted compounds have been approved for therapeutic use to date. This review focuses on the presentation of approaches for discovering new KV 1.3 peptide and small-molecule inhibitors, and strategies to improve the selectivity of active compounds toward KV 1.3. Selectivity of dalatazide (ShK-186), a synthetic derivate of the sea anemone toxin ShK, was achieved by chemical modification and has successfully reached clinical trials as a potential therapeutic for treating autoimmune diseases. Other peptides and small-molecule inhibitors are critically evaluated for their lead-like characteristics and potential for progression into clinical development. Some small-molecule inhibitors with well-defined structure-activity relationships have been optimized for selective delivery to mitochondria, and these offer therapeutic potential for the treatment of cancers. This overview of KV 1.3 inhibitors and methodologies is designed to provide a good starting point for drug discovery to identify novel effective KV 1.3 modulators against this target in the future.
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Affiliation(s)
- Špela Gubič
- Faculty of PharmacyUniversity of LjubljanaLjubljanaSlovenia
| | - Louise A. Hendrickx
- Toxicology and PharmacologyUniversity of Leuven, Campus GasthuisbergLeuvenBelgium
| | - Žan Toplak
- Faculty of PharmacyUniversity of LjubljanaLjubljanaSlovenia
| | - Maša Sterle
- Faculty of PharmacyUniversity of LjubljanaLjubljanaSlovenia
| | - Steve Peigneur
- Faculty of PharmacyUniversity of LjubljanaLjubljanaSlovenia
| | | | - Luis A. Pardo
- AG OncophysiologyMax‐Planck Institute for Experimental MedicineGöttingenGermany
| | - Jan Tytgat
- Toxicology and PharmacologyUniversity of Leuven, Campus GasthuisbergLeuvenBelgium
| | - Anamarija Zega
- Faculty of PharmacyUniversity of LjubljanaLjubljanaSlovenia
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7
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Zheng Q, Na R, Yang L, Yu H, Zhao X, Huang X. The binding process of BmKTX and BmKTX-D33H toward to Kv1.3 channel: a molecular dynamics simulation study. J Biomol Struct Dyn 2020; 39:2788-2797. [PMID: 32329410 DOI: 10.1080/07391102.2020.1760135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The potassium channel Kv1.3 is an important pharmacological target and the Kaliotoxin-type toxins (α-KTX-3 family) are its specific blockers. Here, we study the binding process of two kinds of Kaliotoxin-type toxins:BmKTX and its mutant (BmKTX-D33H) toward to Kv1.3 channel using MD simulation and umbrella sampling simulation, respectively. The calculated binding free energies are -27 kcal/mol and -34 kcal/mol for BmKTX and BmKTX-D33H, respectively, which are consistent with experimental results. The further analysis indicate that the characteristic of electrostatic potential of the α-KTX-3 have important effect on their binding modes with Kv1.3 channel; the residue 33 in BmKTX or BmKTX-D33H plays a key role in determine their binding orientations toward to Kv1.3 channel; when residue 33 (or 34) has negative electrostatic potential, the anti-parallel β-sheet domain of α-KTX-3 toxin peptide will keep away from the filter region of Kv1.3 channel, as BmKTX; when residue 33(or 34) has positive electrostatic potential, the anti-parallel β-sheet domain of α-KTX-3 toxin peptide will interact with the filter region of Kv1.3 channel, as BmKTX-D33H. Above all, electrostatic potential differences on toxin surfaces and correlations motions within the toxins will determine the toxin-potassium channel interaction model. In addition, the hydrogen bond interaction is the pivotal factor for the Kv1.3-Kaliotoxin association. Understanding the binding mechanism of toxin-potassium channel will facilitate the rational development of new toxin analogue.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Qiancheng Zheng
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, China
| | - Risong Na
- College of Plant Protection, Henan Agricultural University, Zhengzhou, P.R China
| | - Lianjuan Yang
- Department of Mycology, Shanghai Dermatology Hospital, Shanghai, China
| | - Hui Yu
- College of Science, Beihua Univesrity, Jilin, China
| | - Xi Zhao
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, China
| | - Xuri Huang
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, China
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8
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Iwakawa N, Baxter NJ, Wai DCC, Fowler NJ, Morales RAV, Sugase K, Norton RS, Williamson MP. Conformational exchange in the potassium channel blocker ShK. Sci Rep 2019; 9:19307. [PMID: 31848433 PMCID: PMC6917819 DOI: 10.1038/s41598-019-55806-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Accepted: 11/21/2019] [Indexed: 11/25/2022] Open
Abstract
ShK is a 35-residue disulfide-linked polypeptide produced by the sea anemone Stichodactyla helianthus, which blocks the potassium channels Kv1.1 and Kv1.3 with pM affinity. An analogue of ShK has been developed that blocks Kv1.3 > 100 times more potently than Kv1.1, and has completed Phase 1b clinical trials for the treatment of autoimmune diseases such as psoriasis and rheumatoid arthritis. Previous studies have indicated that ShK undergoes a conformational exchange that is critical to its function, but this has proved difficult to characterise. Here, we have used high hydrostatic pressure as a tool to increase the population of the alternative state, which is likely to resemble the active form that binds to the Kv1.3 channel. By following changes in chemical shift with pressure, we have derived the chemical shift values of the low- and high-pressure states, and thus characterised the locations of structural changes. The main difference is in the conformation of the Cys17-Cys32 disulfide, which is likely to affect the positions of the critical Lys22-Tyr23 pair by twisting the 21–24 helix and increasing the solvent exposure of the Lys22 sidechain, as indicated by molecular dynamics simulations.
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Affiliation(s)
- Naoto Iwakawa
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku Katsura, Nishikyo-Ku, Kyoto, 615-8510, Japan.,Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | - Nicola J Baxter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | - Dorothy C C Wai
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, 3052, Australia
| | - Nicholas J Fowler
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | - Rodrigo A V Morales
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, 3052, Australia.,CSL Limited (Bio21), 30 Flemington Road, Parkville, Victoria, 3010, Australia
| | - Kenji Sugase
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku Katsura, Nishikyo-Ku, Kyoto, 615-8510, Japan
| | - Raymond S Norton
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, 3052, Australia. .,ARC Centre for Fragment-Based Design, Monash University, Parkville, Victoria, 3052, Australia.
| | - Mike P Williamson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
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9
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Zhao Y, Chen Z, Cao Z, Li W, Wu Y. Diverse Structural Features of Potassium Channels Characterized by Scorpion Toxins as Molecular Probes. Molecules 2019; 24:molecules24112045. [PMID: 31146335 PMCID: PMC6600638 DOI: 10.3390/molecules24112045] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 05/15/2019] [Accepted: 05/26/2019] [Indexed: 12/21/2022] Open
Abstract
Scorpion toxins are well-known as the largest potassium channel peptide blocker family. They have been successfully proven to be valuable molecular probes for structural research on diverse potassium channels. The potassium channel pore region, including the turret and filter regions, is the binding interface for scorpion toxins, and structural features from different potassium channels have been identified using different scorpion toxins. According to the spatial orientation of channel turrets with differential sequence lengths and identities, conformational changes and molecular surface properties, the potassium channel turrets can be divided into the following three states: open state with less hindering effects on toxin binding, half-open state or half-closed state with certain effects on toxin binding, and closed state with remarkable effects on toxin binding. In this review, we summarized the diverse structural features of potassium channels explored using scorpion toxin tools and discuss future work in the field of scorpion toxin-potassium channel interactions.
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Affiliation(s)
- Yonghui Zhao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
| | - Zongyun Chen
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
- Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, College of Basic Medicine, Hubei University of Medicine, Shiyan 442000, China.
| | - Zhijian Cao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
- Biodrug Research Center, Wuhan University, Wuhan 430072, China.
| | - Wenxin Li
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
- Biodrug Research Center, Wuhan University, Wuhan 430072, China.
| | - Yingliang Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
- Biodrug Research Center, Wuhan University, Wuhan 430072, China.
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10
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Oliveira IS, Ferreira IG, Alexandre-Silva GM, Cerni FA, Cremonez CM, Arantes EC, Zottich U, Pucca MB. Scorpion toxins targeting Kv1.3 channels: insights into immunosuppression. J Venom Anim Toxins Incl Trop Dis 2019; 25:e148118. [PMID: 31131004 PMCID: PMC6483409 DOI: 10.1590/1678-9199-jvatitd-1481-18] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 10/17/2018] [Indexed: 01/26/2023] Open
Abstract
Scorpion venoms are natural sources of molecules that have, in addition to their
toxic function, potential therapeutic applications. In this source the
neurotoxins can be found especially those that act on potassium channels.
Potassium channels are responsible for maintaining the membrane potential in the
excitable cells, especially the voltage-dependent potassium channels (Kv),
including Kv1.3 channels. These channels (Kv1.3) are expressed by various types
of tissues and cells, being part of several physiological processes. However,
the major studies of Kv1.3 are performed on T cells due its importance on
autoimmune diseases. Scorpion toxins capable of acting on potassium channels
(KTx), mainly on Kv1.3 channels, have gained a prominent role for their possible
ability to control inflammatory autoimmune diseases. Some of these toxins have
already left bench trials and are being evaluated in clinical trials, presenting
great therapeutic potential. Thus, scorpion toxins are important natural
molecules that should not be overlooked in the treatment of autoimmune and other
diseases.
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Affiliation(s)
- Isadora S Oliveira
- School of Pharmaceutical Sciences of Ribeirão Preto, Department of Physics and Chemistry, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Isabela G Ferreira
- School of Pharmaceutical Sciences of Ribeirão Preto, Department of Physics and Chemistry, University of São Paulo, Ribeirão Preto, SP, Brazil
| | | | - Felipe A Cerni
- Ribeirão Preto Medical School, Department of Biochemistry and Immunology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Caroline M Cremonez
- School of Pharmaceutical Sciences of Ribeirão Preto, Department of Physics and Chemistry, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Eliane C Arantes
- School of Pharmaceutical Sciences of Ribeirão Preto, Department of Physics and Chemistry, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Umberto Zottich
- Medical School, Federal University of Roraima, Boa Vista, RR, Brazil
| | - Manuela B Pucca
- Medical School, Federal University of Roraima, Boa Vista, RR, Brazil
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11
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Du C, Li J, Shao Z, Mwangi J, Xu R, Tian H, Mo G, Lai R, Yang S. Centipede KCNQ Inhibitor SsTx Also Targets K V1.3. Toxins (Basel) 2019; 11:toxins11020076. [PMID: 30717088 PMCID: PMC6409716 DOI: 10.3390/toxins11020076] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 01/25/2019] [Accepted: 01/27/2019] [Indexed: 12/19/2022] Open
Abstract
It was recently discovered that Ssm Spooky Toxin (SsTx) with 53 residues serves as a key killer factor in red-headed centipede’s venom arsenal, due to its potent blockage of the widely expressed KCNQ channels to simultaneously and efficiently disrupt cardiovascular, respiratory, muscular, and nervous systems, suggesting that SsTx is a basic compound for centipedes’ defense and predation. Here, we show that SsTx also inhibits KV1.3 channel, which would amplify the broad-spectrum disruptive effect of blocking KV7 channels. Interestingly, residue R12 in SsTx extends into the selectivity filter to block KV7.4, however, residue K11 in SsTx replaces this ploy when toxin binds on KV1.3. Both SsTx and its mutant SsTx_R12A inhibit cytokines production in T cells without affecting the level of KV1.3 expression. The results further suggest that SsTx is a key molecule for defense and predation in the centipedes’ venoms and it evolves efficient strategy to disturb multiple physiological targets.
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Affiliation(s)
- Canwei Du
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - Jiameng Li
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - Zicheng Shao
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - James Mwangi
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Yunnan Province, Kunming Institute of Zoology, Kunming 650223, Yunnan, China.
- University of Chinese Academy of Sciences, Beijing 100009, China.
| | - Runjia Xu
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - Huiwen Tian
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - Guoxiang Mo
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - Ren Lai
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Yunnan Province, Kunming Institute of Zoology, Kunming 650223, Yunnan, China.
- Sino-African Joint Research Center, Chinese Academy of Science, Wuhan 430074, Hubei, China.
| | - Shilong Yang
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Yunnan Province, Kunming Institute of Zoology, Kunming 650223, Yunnan, China.
- Sino-African Joint Research Center, Chinese Academy of Science, Wuhan 430074, Hubei, China.
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12
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On-chip membrane protein cell-free expression enables development of a direct binding assay: A curious case of potassium channel KcsA-Kv1.3. Anal Biochem 2018; 556:70-77. [DOI: 10.1016/j.ab.2018.06.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 06/19/2018] [Accepted: 06/19/2018] [Indexed: 01/30/2023]
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13
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Liao Q, Gong G, Siu SWI, Wong CTT, Yu H, Tse YC, Rádis-Baptista G, Lee SMY. A Novel ShK-Like Toxic Peptide from the Transcriptome of the Cnidarian Palythoa caribaeorum Displays Neuroprotection and Cardioprotection in Zebrafish. Toxins (Basel) 2018; 10:toxins10060238. [PMID: 29895785 PMCID: PMC6024583 DOI: 10.3390/toxins10060238] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 06/07/2018] [Accepted: 06/08/2018] [Indexed: 12/25/2022] Open
Abstract
Palythoa caribaeorum (class Anthozoa) is a zoantharian which, together with other cnidarians, like jellyfishes, hydra, and sea anemones, possesses specialized structures in its tissues, the cnidocytes, which deliver an array of toxins in order to capture prey and deter predators. The whole transcriptome of P. caribaeroum was deep sequenced, and a diversity of toxin-related peptide sequences were identified, and some retrieved for functional analysis. In this work, a peptide precursor containing a ShK domain, named PcShK3, was analyzed by means of computational processing, comprising structural phylogenetic analysis, model prediction, and dynamics simulation of peptide-receptor interaction. The combined data indicated that PcShK3 is a distinct peptide which is homologous to a cluster of peptides belonging to the ShK toxin family. In vivo, PcShK3 distributed across the vitelline membrane and accumulated in the yolk sac stripe of zebrafish larvae. Notably, it displayed a significant cardio-protective effect in zebrafish in concentrations inferior to the IC50 (<43.53 ± 6.45 µM), while in high concentrations (>IC50), it accumulated in the blood and caused pericardial edema, being cardiotoxic to zebrafish larvae. Remarkably, PcShK3 suppressed the 6-OHDA-induced neurotoxicity on the locomotive behavior of zebrafish. The present results indicated that PcShK3 is a novel member of ShK toxin family, and has the intrinsic ability to induce neuro- and cardio-protective effects or cause cardiac toxicity, according to its effective concentration.
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Affiliation(s)
- Qiwen Liao
- State Key Laboratory of Quality Research in Chinese Medicine and Institute of Chinese Medical Sciences, University of Macau, Macau, China.
| | - Guiyi Gong
- State Key Laboratory of Quality Research in Chinese Medicine and Institute of Chinese Medical Sciences, University of Macau, Macau, China.
| | - Shirley Weng In Siu
- Department of Computer and Information Science, Faculty of Science and Technology, University of Macau, Macau, China.
| | | | - Huidong Yu
- Shenzhen Rongxin Biotechnology Co., Ltd., Shenzhen 518054, China.
| | - Yu Chung Tse
- Department of Biology, South University of Science and Technology of China, Shenzhen 518055, China.
| | - Gandhi Rádis-Baptista
- Laboratory of Biochemistry and Biotechnology, Institute for Marine Sciences, Federal University of Ceará, Fortaleza 60165-081, Brazil.
| | - Simon Ming-Yuen Lee
- State Key Laboratory of Quality Research in Chinese Medicine and Institute of Chinese Medical Sciences, University of Macau, Macau, China.
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14
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Krishnarjuna B, MacRaild CA, Sunanda P, Morales RAV, Peigneur S, Macrander J, Yu HH, Daly M, Raghothama S, Dhawan V, Chauhan S, Tytgat J, Pennington MW, Norton RS. Structure, folding and stability of a minimal homologue from Anemonia sulcata of the sea anemone potassium channel blocker ShK. Peptides 2018; 99:169-178. [PMID: 28993277 DOI: 10.1016/j.peptides.2017.10.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 10/03/2017] [Accepted: 10/05/2017] [Indexed: 01/01/2023]
Abstract
Peptide toxins elaborated by sea anemones target various ion-channel sub-types. Recent transcriptomic studies of sea anemones have identified several novel candidate peptides, some of which have cysteine frameworks identical to those of previously reported sequences. One such peptide is AsK132958, which was identified in a transcriptomic study of Anemonia sulcata and has a cysteine framework similar to that of ShK from Stichodactyla helianthus, but is six amino acid residues shorter. We have determined the solution structure of this novel peptide using NMR spectroscopy. The disulfide connectivities and structural scaffold of AsK132958 are very similar to those of ShK but the structure is more constrained. Toxicity assays were performed using grass shrimp (Palaemonetes sp) and Artemia nauplii, and patch-clamp electrophysiology assays were performed to assess the activity of AsK132958 against a range of voltage-gated potassium (KV) channels. AsK132958 showed no activity against grass shrimp, Artemia nauplii, or any of the KV channels tested, owing partly to the absence of a functional Lys-Tyr dyad. Three AsK132958 analogues, each containing a Tyr in the vicinity of Lys19, were therefore generated in an effort to restore binding, but none showed activity against any of KV channels tested. However, AsK132958 and its analogues are less susceptible to proteolysis than that of ShK. Our structure suggests that Lys19, which might be expected to occupy the pore of the channel, is not sufficiently accessible for binding, and therefore that AsK132958 must have a distinct functional role that does not involve KV channels.
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Affiliation(s)
- Bankala Krishnarjuna
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Christopher A MacRaild
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Punnepalli Sunanda
- NMR Research Centre, Indian Institute of Science, Bangalore 560012, India
| | - Rodrigo A V Morales
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Steve Peigneur
- Toxicology and Pharmacology, University of Leuven, O&N 2, Herestraat 49, P.O. Box 922, 3000, Leuven, Belgium
| | - Jason Macrander
- Department of Evolution, Ecology, Organismal Biology, Ohio State University, 1315 Kinnear Rd, Columbus, OH 43212, USA; Department of Biology, University of North Carolina at Charlotte, 9201 University City Blvd, Charlotte, NC 28223, USA
| | - Heidi H Yu
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, VIC 3800, Australia
| | - Marymegan Daly
- Department of Evolution, Ecology, Organismal Biology, Ohio State University, 1315 Kinnear Rd, Columbus, OH 43212, USA
| | | | - Vikas Dhawan
- Peptides International, Louisville, KY 40299, USA
| | | | - Jan Tytgat
- Toxicology and Pharmacology, University of Leuven, O&N 2, Herestraat 49, P.O. Box 922, 3000, Leuven, Belgium
| | | | - Raymond S Norton
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia.
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15
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Renauld S, Cortes S, Bersch B, Henry X, De Waard M, Schaack B. Functional reconstitution of cell-free synthesized purified Kv channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2373-2380. [DOI: 10.1016/j.bbamem.2017.09.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 08/29/2017] [Accepted: 09/05/2017] [Indexed: 12/11/2022]
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16
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Yuan S, Gao B, Zhu S. Molecular Dynamics Simulation Reveals Specific Interaction Sites between Scorpion Toxins and K v1.2 Channel: Implications for Design of Highly Selective Drugs. Toxins (Basel) 2017; 9:toxins9110354. [PMID: 29104247 PMCID: PMC5705969 DOI: 10.3390/toxins9110354] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 10/15/2017] [Accepted: 10/19/2017] [Indexed: 01/06/2023] Open
Abstract
The Kv1.2 channel plays an important role in the maintenance of resting membrane potential and the regulation of the cellular excitability of neurons, whose silencing or mutations can elicit neuropathic pain or neurological diseases (e.g., epilepsy and ataxia). Scorpion venom contains a variety of peptide toxins targeting the pore region of this channel. Despite a large amount of structural and functional data currently available, their detailed interaction modes are poorly understood. In this work, we choose four Kv1.2-targeted scorpion toxins (Margatoxin, Agitoxin-2, OsK-1, and Mesomartoxin) to construct their complexes with Kv1.2 based on the experimental structure of ChTx-Kv1.2. Molecular dynamics simulation of these complexes lead to the identification of hydrophobic patches, hydrogen-bonds, and salt bridges as three essential forces mediating the interactions between this channel and the toxins, in which four Kv1.2-specific interacting amino acids (D353, Q358, V381, and T383) are identified for the first time. This discovery might help design highly selective Kv1.2-channel inhibitors by altering amino acids of these toxins binding to the four channel residues. Finally, our results provide new evidence in favor of an induced fit model between scorpion toxins and K+ channel interactions.
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Affiliation(s)
- Shouli Yuan
- Group of Peptide Biology and Evolution, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Bin Gao
- Group of Peptide Biology and Evolution, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
| | - Shunyi Zhu
- Group of Peptide Biology and Evolution, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
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17
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Molecular Simulations of Disulfide-Rich Venom Peptides with Ion Channels and Membranes. Molecules 2017; 22:molecules22030362. [PMID: 28264446 PMCID: PMC6155311 DOI: 10.3390/molecules22030362] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 02/23/2017] [Accepted: 02/24/2017] [Indexed: 12/12/2022] Open
Abstract
Disulfide-rich peptides isolated from the venom of arthropods and marine animals are a rich source of potent and selective modulators of ion channels. This makes these peptides valuable lead molecules for the development of new drugs to treat neurological disorders. Consequently, much effort goes into understanding their mechanism of action. This paper presents an overview of how molecular simulations have been used to study the interactions of disulfide-rich venom peptides with ion channels and membranes. The review is focused on the use of docking, molecular dynamics simulations, and free energy calculations to (i) predict the structure of peptide-channel complexes; (ii) calculate binding free energies including the effect of peptide modifications; and (iii) study the membrane-binding properties of disulfide-rich venom peptides. The review concludes with a summary and outlook.
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18
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Fung-Leung WP, Edwards W, Liu Y, Ngo K, Angsana J, Castro G, Wu N, Liu X, Swanson RV, Wickenden AD. T Cell Subset and Stimulation Strength-Dependent Modulation of T Cell Activation by Kv1.3 Blockers. PLoS One 2017; 12:e0170102. [PMID: 28107393 PMCID: PMC5249144 DOI: 10.1371/journal.pone.0170102] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 12/29/2016] [Indexed: 12/28/2022] Open
Abstract
Kv1.3 is a voltage-gated potassium channel expressed on T cells that plays an important role in T cell activation. Previous studies have shown that blocking Kv1.3 channels in human T cells during activation results in reduced calcium entry, cytokine production, and proliferation. The aim of the present study was to further explore the effects of Kv1.3 blockers on the response of different human T cell subsets under various stimulation conditions. Our studies show that, unlike the immune suppressor cyclosporine A, the inhibitory effect of Kv1.3 blockers was partial and stimulation strength dependent, with reduced inhibitory efficacy on T cells under strengthened anti-CD3/CD28 stimulations. T cell responses to allergens including house dust mites and ragweed were partially reduced by Kv1.3 blockers. The effect of Kv1.3 inhibition was dependent on T cell subsets, with stronger effects on CCR7- effector memory compared to CCR7+ central memory CD4 T cells. Calcium entry studies also revealed a population of CD4 T cells resistant to Kv1.3 blockade. Activation of CD4 T cells was accompanied with an increase in Kv1.3 currents but Kv1.3 transcripts were found to be reduced, suggesting a posttranscriptional mechanism in the regulation of Kv1.3 activities. In summary, Kv1.3 blockers inhibit T cell activation in a manner that is highly dependent on the T cell identity and stimulation strength, These findings suggest that Kv1.3 blockers inhibit T cells in a unique, conditional manner, further refining our understanding of the therapeutic potential of Kv1.3 blockers.
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Affiliation(s)
- Wai-Ping Fung-Leung
- Janssen Research & Development, L.L.C., San Diego, California, United States of America
- * E-mail:
| | - Wilson Edwards
- Janssen Research & Development, L.L.C., San Diego, California, United States of America
| | - Yi Liu
- Janssen Research & Development, L.L.C., San Diego, California, United States of America
| | - Karen Ngo
- Janssen Research & Development, L.L.C., San Diego, California, United States of America
| | - Julianty Angsana
- Janssen Research & Development, L.L.C., San Diego, California, United States of America
| | - Glenda Castro
- Janssen Research & Development, L.L.C., San Diego, California, United States of America
| | - Nancy Wu
- Janssen Research & Development, L.L.C., San Diego, California, United States of America
| | - Xuejun Liu
- Janssen Research & Development, L.L.C., San Diego, California, United States of America
| | - Ronald V. Swanson
- Janssen Research & Development, L.L.C., San Diego, California, United States of America
| | - Alan D. Wickenden
- Janssen Research & Development, L.L.C., San Diego, California, United States of America
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19
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Schwartz AB, Kapur A, Wang W, Huang Z, Fardone E, Palui G, Mattoussi H, Fadool DA. Margatoxin-bound quantum dots as a novel inhibitor of the voltage-gated ion channel Kv1.3. J Neurochem 2016; 140:404-420. [PMID: 27861889 DOI: 10.1111/jnc.13891] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Revised: 10/24/2016] [Accepted: 10/31/2016] [Indexed: 01/01/2023]
Abstract
Venom-derived ion channel inhibitors have strong channel selectivity, potency, and stability; however, tracking delivery to their target can be challenging. Herein, we utilized luminescent quantum dots (QDs) conjugated to margatoxin (MgTx) as a traceable vehicle to target a voltage-dependent potassium channel, Kv1.3, which has a select distribution and well-characterized role in immunity, glucose metabolism, and sensory ability. We screened both unconjugated (MgTx) and conjugated MgTx (QD-MgTx) for their ability to inhibit Shaker channels Kv1.1 to Kv1.7 using patch-clamp electrophysiology in HEK293 cells. Our data indicate that MgTx inhibits 79% of the outward current in Kv1.3-transfected cells and that the QD-MgTx conjugate is able to achieve a similar level of block, albeit a slightly reduced efficacy (66%) and at a slower time course (50% block by 10.9 ± 1.1 min, MgTx; vs. 15.3 ± 1.2 min, QD-MgTx). Like the unbound peptide, the QD-MgTx conjugate inhibits both Kv1.3 and Kv1.2 at a 1 nM concentration, whereas it does not inhibit other screened Shaker channels. We tested the ability of QD-MgTx to inhibit native Kv1.3 expressed in the mouse olfactory bulb (OB). In brain slices of the OB, the conjugate acted similarly to MgTx to inhibit Kv1.3, causing an increased action potential firing frequency attributed to decreased intraburst duration rather than interspike interval. Our data demonstrate a retention of known biophysical properties associated with block of the vestibule of Kv1.3 by QD-MgTx conjugate compared to that of MgTx, inferring QDs could provide a useful tool to deliver ion channel inhibitors to targeted tissues in vivo.
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Affiliation(s)
- Austin B Schwartz
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, USA
| | - Anshika Kapur
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, USA
| | - Wentao Wang
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, USA
| | - Zhenbo Huang
- Program in Neuroscience, Florida State University, Tallahassee, Florida, USA
| | - Erminia Fardone
- Program in Neuroscience, Florida State University, Tallahassee, Florida, USA.,Department of Biological Science, Florida State University, Tallahassee, Florida, USA
| | - Goutam Palui
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, USA
| | - Hedi Mattoussi
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, USA
| | - Debra Ann Fadool
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, USA.,Program in Neuroscience, Florida State University, Tallahassee, Florida, USA.,Department of Biological Science, Florida State University, Tallahassee, Florida, USA
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20
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Ye F, Hu Y, Yu W, Xie Z, Hu J, Cao Z, Li W, Wu Y. The Scorpion Toxin Analogue BmKTX-D33H as a Potential Kv1.3 Channel-Selective Immunomodulator for Autoimmune Diseases. Toxins (Basel) 2016; 8:115. [PMID: 27104568 PMCID: PMC4848641 DOI: 10.3390/toxins8040115] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Revised: 04/11/2016] [Accepted: 04/12/2016] [Indexed: 01/23/2023] Open
Abstract
The Kv1.3 channel-acting scorpion toxins usually adopt the conserved anti-parallel β-sheet domain as the binding interface, but it remains challenging to discover some highly selective Kv1.3 channel-acting toxins. In this work, we investigated the pharmacological profile of the Kv1.3 channel-acting BmKTX-D33H, a structural analogue of the BmKTX scorpion toxin. Interestingly, BmKTX-D33H, with its conserved anti-parallel β-sheet domain as a Kv1.3 channel-interacting interface, exhibited more than 1000-fold selectivity towards the Kv1.3 channel as compared to other K+ channels (including Kv1.1, Kv1.2, Kv1.7, Kv11.1, KCa2.2, KCa2.3, and KCa3.1). As expected, BmKTX-D33H was found to inhibit the cytokine production and proliferation of both Jurkat cells and human T cells in vitro. It also significantly improved the delayed-type hypersensitivity (DTH) responses, an autoreactive T cell-mediated inflammation in rats. Amino acid sequence alignment and structural analysis strongly suggest that the “evolutionary” Gly11 residue of BmKTX-D33H interacts with the turret domain of Kv1 channels; it appears to be a pivotal amino acid residue with regard to the selectivity of BmKTX-D33H towards the Kv1.3 channel (in comparison with the highly homologous scorpion toxins). Together, our data indicate that BmKTX-D33H is a Kv1.3 channel–specific blocker. Finally, the remarkable selectivity of BmKTX-D33H highlights the great potential of evolutionary-guided peptide drug design in future studies.
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Affiliation(s)
- Fang Ye
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
| | - Youtian Hu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
| | - Weiwei Yu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
| | - Zili Xie
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
| | - Jun Hu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
| | - Zhijian Cao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
| | - Wenxin Li
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
| | - Yingliang Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
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21
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Novoseletsky VN, Volyntseva AD, Shaitan KV, Kirpichnikov MP, Feofanov AV. Modeling of the Binding of Peptide Blockers to Voltage-Gated Potassium Channels: Approaches and Evidence. Acta Naturae 2016; 8:35-46. [PMID: 27437138 PMCID: PMC4947987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Indexed: 11/13/2022] Open
Abstract
Modeling of the structure of voltage-gated potassium (KV) channels bound to peptide blockers aims to identify the key amino acid residues dictating affinity and provide insights into the toxin-channel interface. Computational approaches open up possibilities for in silico rational design of selective blockers, new molecular tools to study the cellular distribution and functional roles of potassium channels. It is anticipated that optimized blockers will advance the development of drugs that reduce over activation of potassium channels and attenuate the associated malfunction. Starting with an overview of the recent advances in computational simulation strategies to predict the bound state orientations of peptide pore blockers relative to KV-channels, we go on to review algorithms for the analysis of intermolecular interactions, and then take a look at the results of their application.
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Affiliation(s)
- V. N. Novoseletsky
- M.V.Lomonosov Moscow State University, Faculty of Biology, Leninskie Gory 1, bldg. 12, 119992 , Moscow, Russia
| | - A. D. Volyntseva
- M.V.Lomonosov Moscow State University, Faculty of Biology, Leninskie Gory 1, bldg. 12, 119992 , Moscow, Russia
| | - K. V. Shaitan
- M.V.Lomonosov Moscow State University, Faculty of Biology, Leninskie Gory 1, bldg. 12, 119992 , Moscow, Russia
| | - M. P. Kirpichnikov
- M.V.Lomonosov Moscow State University, Faculty of Biology, Leninskie Gory 1, bldg. 12, 119992 , Moscow, Russia
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho- Maklaya str. 16/10, 117997, Moscow, Russia
| | - A. V. Feofanov
- M.V.Lomonosov Moscow State University, Faculty of Biology, Leninskie Gory 1, bldg. 12, 119992 , Moscow, Russia
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho- Maklaya str. 16/10, 117997, Moscow, Russia
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22
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Peptidomimetic Star Polymers for Targeting Biological Ion Channels. PLoS One 2016; 11:e0152169. [PMID: 27007701 PMCID: PMC4805292 DOI: 10.1371/journal.pone.0152169] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 03/09/2016] [Indexed: 11/19/2022] Open
Abstract
Four end-functionalized star polymers that could attenuate the flow of ionic currents across biological ion channels were first de novo designed computationally, then synthesized and tested experimentally on mammalian K+ channels. The 4-arm ethylene glycol conjugate star polymers with lysine or a tripeptide attached to the end of each arm were specifically designed to mimic the action of scorpion toxins on K+ channels. Molecular dynamics simulations showed that the lysine side chain of the polymers physically occludes the pore of Kv1.3, a target for immuno-suppression therapy. Two of the compounds tested were potent inhibitors of Kv1.3. The dissociation constants of these two compounds were computed to be 0.1 μM and 0.7 μM, respectively, within 3-fold to the values derived from subsequent experiments. These results demonstrate the power of computational methods in molecular design and the potential of star polymers as a new infinitely modifiable platform for ion channel drug discovery.
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23
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Deplazes E, Davies J, Bonvin AMJJ, King GF, Mark AE. Combination of Ambiguous and Unambiguous Data in the Restraint-driven Docking of Flexible Peptides with HADDOCK: The Binding of the Spider Toxin PcTx1 to the Acid Sensing Ion Channel (ASIC) 1a. J Chem Inf Model 2015; 56:127-38. [PMID: 26642380 DOI: 10.1021/acs.jcim.5b00529] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Peptides that bind to ion channels have attracted much interest as potential lead molecules for the development of new drugs and insecticides. However, the structure determination of large peptide-channel complexes using experimental methods is challenging. Thus structural models are often derived from combining experimental information with restraint-driven docking approaches. Using the complex formed by the venom peptide PcTx1 and the acid sensing ion channel (ASIC) 1a as a case study, we have examined the effect of different combinations of restraints and input structures on the statistical likelihood of (a) correctly predicting the structure of the binding interface and (b) the ability to predict which residues are involved in specific pairwise peptide-channel interactions. For this, we have analyzed over 200,000 water-refined docked structures obtained with various amounts and types of restraints of the peptide-channel complex predicted using the docking program HADDOCK. We found that increasing the number of restraints or even the use of pairwise interaction data resulted in only a modest improvement in the likelihood of finding a structure within a given accuracy. This suggests that shape complementarity and the force field make a large contribution to the accuracy of the predicted structure. The results also showed that there are large variations in the accuracy of the predicted structure depending on the precise combination of residues used as restraints. Finally, we reflect on the limitations of relying on geometric criteria such as root-mean square deviations to assess the accuracy of docking procedures. We propose that in addition to currently used measures, the likelihood of finding a structure within a given level of accuracy should be also used to evaluate docking methods.
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Affiliation(s)
- Evelyne Deplazes
- Institute for Molecular Bioscience, The University of Queensland , St. Lucia, Queensland 4072, Australia.,School of Chemistry & Molecular Biosciences, The University of Queensland , St. Lucia, Queensland 4072, Australia
| | - Josephine Davies
- School of Chemistry & Molecular Biosciences, The University of Queensland , St. Lucia, Queensland 4072, Australia
| | - Alexandre M J J Bonvin
- Bijvoet Center for Biomolecular Research, Faculty of Science - Chemistry, Utrecht University , 3584 CH Utrecht, The Netherlands
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland , St. Lucia, Queensland 4072, Australia
| | - Alan E Mark
- School of Chemistry & Molecular Biosciences, The University of Queensland , St. Lucia, Queensland 4072, Australia
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24
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Computational Studies of Venom Peptides Targeting Potassium Channels. Toxins (Basel) 2015; 7:5194-211. [PMID: 26633507 PMCID: PMC4690127 DOI: 10.3390/toxins7124877] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 11/13/2015] [Accepted: 11/20/2015] [Indexed: 01/18/2023] Open
Abstract
Small peptides isolated from the venom of animals are potential scaffolds for ion channel drug discovery. This review article mainly focuses on the computational studies that have advanced our understanding of how various toxins interfere with the function of K+ channels. We introduce the computational tools available for the study of toxin-channel interactions. We then discuss how these computational tools have been fruitfully applied to elucidate the mechanisms of action of a wide range of venom peptides from scorpions, spiders, and sea anemone.
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25
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Nikouee A, Khabiri M, Cwiklik L. Scorpion toxins prefer salt solutions. J Mol Model 2015; 21:287. [PMID: 26475740 DOI: 10.1007/s00894-015-2822-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 09/15/2015] [Indexed: 11/26/2022]
Abstract
There is a wide variety of ion channel types with various types of blockers, making research in this field very complicated. To reduce this complexity, it is essential to study ion channels and their blockers independently. Scorpion toxins, a major class of blockers, are charged short peptides with high affinities for potassium channels. Their high selectivity and inhibitory properties make them an important pharmacological tool for treating autoimmune or nervous system disorders. Scorpion toxins typically have highly charged surfaces and-like other proteins-an intrinsic ability to bind ions (Friedman J Phys Chem B 115(29):9213-9223, 1996; Baldwin Biophys J 71(4):2056-2063, 1996; Vrbka et al. Proc Natl Acad Sci USA 103(42):15440-15444, 2006a; Vrbka et al. J Phys Chem B 110(13):7036-43, 2006b). Thus, their effects on potassium channels are usually investigated in various ionic solutions. In this work, computer simulations of protein structures were performed to analyze the structural properties of the key residues (i.e., those that are presumably involved in contact with the surfaces of the ion channels) of 12 scorpion toxins. The presence of the two most physiologically abundant cations, Na(+) and K(+), was considered. The results indicated that the ion-binding properties of the toxin residues vary. Overall, all of the investigated toxins had more stable structures in ionic solutions than in water. We found that both the number and length of elements in the secondary structure varied depending on the ionic solution used (i.e., in the presence of NaCl or KCl). This study revealed that the ionic solution should be chosen carefully before performing experiments on these toxins. Similarly, the influence of these ions should be taken into consideration in the design of toxin-based pharmaceuticals.
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Affiliation(s)
- Azadeh Nikouee
- Institute of Applied Physiology, Ulm University, Ulm, Germany
| | - Morteza Khabiri
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610, Prague 6, Czech Republic.
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA.
| | - Lukasz Cwiklik
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610, Prague 6, Czech Republic
- J. Heyrovský Institute of Physical Chemistry Academy of Sciences of the Czech Republic v.v.i., Dolejskova 3, 18223, Prague 8, Czech Republic
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26
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Chen Z, Hu Y, Wang B, Cao Z, Li W, Wu Y. A single conserved basic residue in the potassium channel filter region controls KCNQ1 insensitivity toward scorpion toxins. Biochem Biophys Rep 2015; 3:62-67. [PMID: 29124168 PMCID: PMC5668678 DOI: 10.1016/j.bbrep.2015.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Revised: 07/05/2015] [Accepted: 07/07/2015] [Indexed: 02/06/2023] Open
Abstract
Although many studies concerning the sensitivity mechanism of scorpion toxin-potassium channel interactions have been reported, few have explored the biochemical insensitivity mechanisms of potassium channel receptors toward natural scorpion toxin peptides, such as the KCNQ1 channel. Here, by sequence alignment analyses of the human KCNQ1 channel and scorpion potassium channel MmKv2, which is completely insensitive to scorpion toxins, we proposed that the insensitivity mechanism of KCNQ1 toward natural scorpion toxins might involve two functional regions, the turret and filter regions. Based on this observation, a series of KCNQ1 mutants were constructed to study molecular mechanisms of the KCNQ1 channel insensitivity toward natural scorpion toxins. Electrophysiological studies of chimera channels showed that the channel filter region controls KCNQ1 insensitivity toward the classical scorpion toxin ChTX. Interestingly, further residue mutant experiments showed that a single basic residue in the filter region determined the insensitivity of KCNQ1 channels toward scorpion toxins. Our present work showed that amino acid residue diversification at common sites controls the sensitivity and insensitivity of potassium channels toward scorpion toxins. The unique insensitivity mechanism of KCNQ1 toward natural scorpion toxins will accelerate the rational design of potent peptide inhibitors toward this channel. Insensitivity mechanism of KCNQ1 towards scorpion toxins was still unclear. A single basic residue in the KCNQ1 filter region controls its insensitivity. Amino acid residue diversification controls KCNQ1 sensitivity and insensitivity. Our work will accelerate rational design of KCNQ1 peptide inhibitors.
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Affiliation(s)
- Zongyun Chen
- Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Hubei University of Medicine, Hubei, China.,State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China
| | - Youtian Hu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China
| | - Bin Wang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China
| | - Zhijian Cao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China
| | - Wenxin Li
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China
| | - Yingliang Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China
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27
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Computational approaches for designing potent and selective analogs of peptide toxins as novel therapeutics. Future Med Chem 2015; 6:1645-58. [PMID: 25406005 DOI: 10.4155/fmc.14.98] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Peptide toxins provide valuable therapeutic leads for many diseases. As they bind to their targets with high affinity, potency is usually ensured. However, toxins also bind to off-target receptors, causing potential side effects. Thus, a major challenge in generating drugs from peptide toxins is ensuring their specificity for their intended targets. Computational methods can play an important role in solving such design problems through construction of accurate models of receptor-toxin complexes and calculation of binding free energies. Here we review the computational methods used for this purpose and their application to toxins targeting ion channels. We describe ShK and HsTX1 toxins, high-affinity blockers of the voltage-gated potassium channel Kv1.3, which could be developed as therapeutic agents for autoimmune diseases.
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28
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Plectasin, first animal toxin-like fungal defensin blocking potassium channels through recognizing channel pore region. Toxins (Basel) 2015; 7:34-42. [PMID: 25568977 PMCID: PMC4303811 DOI: 10.3390/toxins7010034] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 12/24/2014] [Indexed: 12/04/2022] Open
Abstract
The potassium channels were recently found to be inhibited by animal toxin-like human β-defensin 2 (hBD2), the first defensin blocker of potassium channels. Whether there are other defensin blockers from different organisms remains an open question. Here, we reported the potassium channel-blocking plectasin, the first defensin blocker from a fungus. Based on the similar cysteine-stabilized alpha-beta (CSαβ) structure between plectasin and scorpion toxins acting on potassium channels, we found that plectasin could dose-dependently block Kv1.3 channel currents through electrophysiological experiments. Besides Kv1.3 channel, plectasin could less inhibit Kv1.1, Kv1.2, IKCa, SKCa3, hERG and KCNQ channels at the concentration of 1 μΜ. Using mutagenesis and channel activation experiments, we found that outer pore region of Kv1.3 channel was the binding site of plectasin, which is similar to the interacting site of Kv1.3 channel recognized by animal toxin blockers. Together, these findings not only highlight the novel function of plectasin as a potassium channel inhibitor, but also imply that defensins from different organisms functionally evolve to be a novel kind of potassium channel inhibitors.
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29
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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.
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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.
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30
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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.
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31
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Sabogal-Arango A, Barreto GE, Ramírez-Sánchez D, González-Mendoza J, Barreto V, Morales L, González J. Computational Insights of the Interaction among Sea Anemones Neurotoxins and Kv1.3 Channel. Bioinform Biol Insights 2014; 8:73-81. [PMID: 24812496 PMCID: PMC3999815 DOI: 10.4137/bbi.s13403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2013] [Revised: 01/23/2014] [Accepted: 01/24/2014] [Indexed: 12/21/2022] Open
Abstract
Sea anemone neurotoxins are peptides that interact with Na(+) and K(+) channels, resulting in specific alterations on their functions. Some of these neurotoxins (1ROO, 1BGK, 2K9E, 1BEI) are important for the treatment of about 80 autoimmune disorders because of their specificity for Kv1.3 channel. The aim of this study was to identify the common residues among these neurotoxins by computational methods, and establish whether there is a pattern useful for the future generation of a treatment for autoimmune diseases. Our results showed eight new key common residues between the studied neurotoxins interacting with a histidine ring and the selectivity filter of the receptor, thus showing a possible pattern of interaction. This knowledge may serve as an input for the design of more promising drugs for autoimmune treatments.
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Affiliation(s)
- Angélica Sabogal-Arango
- Department of Nutrition and Biochemistry, Faculty of Science, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - George E Barreto
- Department of Nutrition and Biochemistry, Faculty of Science, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - David Ramírez-Sánchez
- Department of Pharmacy, Faculty of Science, Universidad Nacional de Colombia, Bogotá D.C., Colombia
| | - Juan González-Mendoza
- Department of Pharmacy, Faculty of Science, Universidad Nacional de Colombia, Bogotá D.C., Colombia
| | - Viviana Barreto
- Department of Nutrition and Biochemistry, Faculty of Science, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - Ludis Morales
- Department of Nutrition and Biochemistry, Faculty of Science, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - Janneth González
- Department of Nutrition and Biochemistry, Faculty of Science, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
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32
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Luna-Ramírez K, Bartok A, Restano-Cassulini R, Quintero-Hernández V, Coronas FIV, Christensen J, Wright CE, Panyi G, Possani LD. Structure, Molecular Modeling, and Function of the Novel Potassium Channel Blocker Urotoxin Isolated from the Venom of the Australian Scorpion Urodacus yaschenkoi. Mol Pharmacol 2014; 86:28-41. [DOI: 10.1124/mol.113.090183] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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33
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Rashid MH, Kuyucak S. Free Energy Simulations of Binding of HsTx1 Toxin to Kv1 Potassium Channels: the Basis of Kv1.3/Kv1.1 Selectivity. J Phys Chem B 2014; 118:707-16. [DOI: 10.1021/jp410950h] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- M. Harunur Rashid
- School of Physics, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Serdar Kuyucak
- School of Physics, University of Sydney, Sydney, New South Wales 2006, Australia
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34
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Hilder TA, Chung SH. Designing a C84 fullerene as a specific voltage-gated sodium channel blocker. NANOSCALE RESEARCH LETTERS 2013; 8:323. [PMID: 23855749 PMCID: PMC3726465 DOI: 10.1186/1556-276x-8-323] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 07/09/2013] [Indexed: 05/15/2023]
Abstract
Fullerene derivatives demonstrate considerable potential for numerous biological applications, such as the effective inhibition of HIV protease. Recently, they were identified for their ability to indiscriminately block biological ion channels. A fullerene derivative which specifically blocks a particular ion channel could lead to a new set of drug leads for the treatment of various ion channel-related diseases. Here, we demonstrate their extraordinary potential by designing a fullerene which mimics some of the functions of μ-conotoxin, a peptide derived from cone snail venom which potently binds to the bacterial voltage-gated sodium channel (NavAb). We show, using molecular dynamics simulations, that the C84 fullerene with six lysine derivatives uniformly attached to its surface is selective to NavAb over a voltage-gated potassium channel (Kv1.3). The side chain of one of the lysine residues protrudes into the selectivity filter of the channel, while the methionine residues located just outside of the channel form hydrophobic contacts with the carbon atoms of the fullerene. The modified C84 fullerene strongly binds to the NavAb channel with an affinity of 46 nM but binds weakly to Kv1.3 with an affinity of 3 mM. This potent blocker of NavAb may serve as a structural template from which potent compounds can be designed for the targeting of mammalian Nav channels. There is a genuine need to target mammalian Nav channels as a form of treatment of various diseases which have been linked to their malfunction, such as epilepsy and chronic pain.
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Affiliation(s)
- Tamsyn A Hilder
- Computational Biophysics Group, Research School of Biology, Australian National University, ACT 0200 Canberra, Australia
| | - Shin-Ho Chung
- Computational Biophysics Group, Research School of Biology, Australian National University, ACT 0200 Canberra, Australia
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35
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Chen R, Chung SH. Complex structures between the N-type calcium channel (CaV2.2) and ω-conotoxin GVIA predicted via molecular dynamics. Biochemistry 2013; 52:3765-72. [PMID: 23651160 DOI: 10.1021/bi4003327] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The N-type voltage-gated Ca(2+) channel CaV2.2 is one of the important targets for pain management. ω-Conotoxins isolated from venoms of cone snails, which specifically inhibit CaV2.2, are promising scaffolds for novel analgesics. The inhibitory action of ω-conotoxins on CaV2.2 has been examined experimentally, but the modes of binding of the toxins to this and other related subfamilies of Ca(2+) channels are not understood in detail. Here molecular dynamics simulations are used to construct models of ω-conotoxin GVIA in complex with a homology model of the pore domain of CaV2.2. Three different binding modes in which the side chain of Lys2, Arg17, or Lys24 from the toxin protrudes into the selectivity filter of CaV2.2 are considered. In all the modes, the toxin forms a salt bridge with an aspartate residue of subunit II just above the EEEE ring of the selectivity filter. Using the umbrella sampling technique and potential of mean force calculations, the half-maximal inhibitory concentration (IC50) values are calculated to be 1.5 and 0.7 nM for the modes in which Lys2 and Arg17 occlude the ion conduction pathway, respectively. Both IC50 values compare favorably with the values of 0.04-1.0 nM determined experimentally. The similar IC50 values calculated for the different binding modes demonstrate that GVIA can inhibit CaV2.2 with alternative binding modes. Such a multiple-binding mode mechanism may be common for ω-conotoxins.
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Affiliation(s)
- Rong Chen
- Research School of Biology, Australian National University , Canberra, ACT 0200, Australia
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36
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Gordon D, Chen R, Chung SH. Computational methods of studying the binding of toxins from venomous animals to biological ion channels: theory and applications. Physiol Rev 2013; 93:767-802. [PMID: 23589832 PMCID: PMC3768100 DOI: 10.1152/physrev.00035.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The discovery of new drugs that selectively block or modulate ion channels has great potential to provide new treatments for a host of conditions. One promising avenue revolves around modifying or mimicking certain naturally occurring ion channel modulator toxins. This strategy appears to offer the prospect of designing drugs that are both potent and specific. The use of computational modeling is crucial to this endeavor, as it has the potential to provide lower cost alternatives for exploring the effects of new compounds on ion channels. In addition, computational modeling can provide structural information and theoretical understanding that is not easily derivable from experimental results. In this review, we look at the theory and computational methods that are applicable to the study of ion channel modulators. The first section provides an introduction to various theoretical concepts, including force-fields and the statistical mechanics of binding. We then look at various computational techniques available to the researcher, including molecular dynamics, brownian dynamics, and molecular docking systems. The latter section of the review explores applications of these techniques, concentrating on pore blocker and gating modifier toxins of potassium and sodium channels. After first discussing the structural features of these channels, and their modes of block, we provide an in-depth review of past computational work that has been carried out. Finally, we discuss prospects for future developments in the field.
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Affiliation(s)
- Dan Gordon
- Research School of Biology, The Australian National University, Acton, ACT 0200, Australia.
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37
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Computational studies of marine toxins targeting ion channels. Mar Drugs 2013; 11:848-69. [PMID: 23528952 PMCID: PMC3705375 DOI: 10.3390/md11030848] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 01/30/2013] [Accepted: 02/07/2013] [Indexed: 12/18/2022] Open
Abstract
Toxins from marine animals offer novel drug leads for treatment of diseases involving ion channels. Computational methods could be very helpful in this endeavour in several ways, e.g., (i) constructing accurate models of the channel-toxin complexes using docking and molecular dynamics (MD) simulations; (ii) determining the binding free energies of toxins from umbrella sampling MD simulations; (iii) predicting the effect of mutations from free energy MD simulations. Using these methods, one can design new analogs of toxins with improved affinity and selectivity properties. Here we present a review of the computational methods and discuss their applications to marine toxins targeting potassium and sodium channels. Detailed examples from the potassium channel toxins—ShK from sea anemone and κ-conotoxin PVIIA—are provided to demonstrate capabilities of the computational methods to give accurate descriptions of the channel-toxin complexes and the energetics of their binding. An example is also given from sodium channel toxins (µ-conotoxin GIIIA) to illustrate the differences between the toxin binding modes in potassium and sodium channels.
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38
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Mahdavi S, Kuyucak S. Why the Drosophila Shaker K+ channel is not a good model for ligand binding to voltage-gated Kv1 channels. Biochemistry 2013; 52:1631-40. [PMID: 23398369 DOI: 10.1021/bi301257p] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The Drosophila Shaker K(+) channel is the first cloned voltage-gated potassium channel and has, therefore, played an important role in structural and functional studies of those channels. While such a role is well justified for ion permeation, it is not clear whether this also extends to ligand binding. Despite the high degree of homology among Shaker and Kv1 channels, κ-conotoxin PVIIA (κ-PVIIA) binds to Shaker with high affinity but not to Kv1 channels. Here we address this issue by studying binding of κ-PVIIA to Shaker and Kv1 channels using molecular dynamics (MD) simulations. The structures of the channel-toxin complexes are constructed via docking and refinement with MD. The binding mode of each complex is characterized and compared to available mutagenesis data to validate the complex models. The potential of mean force for dissociation of the Shaker-κ-PVIIA complex is calculated from umbrella sampling MD simulations, and the corresponding binding free energy is determined, which provides further validation of the complex structure. Comparison of the Shaker and Kv1 complex models shows that a few mutations in the turret and extended regions are sufficient to abolish the observed sensitivity of Shaker to κ-PVIIA. This study demonstrates that Shaker is not always a good model for Kv1 channels for ligand binding. It also provides insights into the binding of the toxin to potassium channels that will be useful for improving affinity and selectivity properties of Kv1 channels.
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Affiliation(s)
- Somayeh Mahdavi
- School of Physics, University of Sydney, Sydney, New South Wales 2006, Australia
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39
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Hilder TA, Chung SH. Conduction and block of inward rectifier K+ channels: predicted structure of a potent blocker of Kir2.1. Biochemistry 2013; 52:967-74. [PMID: 23320951 DOI: 10.1021/bi301498x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dysfunction of Kir2.1, thought to be the major component of inward currents, I(K1), in the heart, has been linked to various channelopathies, such as short Q-T syndrome. Unfortunately, currently no known blockers of Kir2.x channels exist. In contrast, Kir1.1b, predominantly expressed in the kidney, is potently blocked by an oxidation-resistant mutant of the honey bee toxin tertiapin (tertiapin-Q). Using various computational tools, we show that both channels are closed by a hydrophobic gating mechanism and inward rectification occurs in the absence of divalent cations and polyamines. We then demonstrate that tertiapin-Q binds to the external vestibule of Kir1.1b and Kir2.1 with K(d) values of 11.6 nM and 131 μM, respectively. We find that a single mutation of tertiapin-Q increases the binding affinity for Kir2.1 by 5 orders of magnitude (K(d) = 0.7 nM). This potent blocker of Kir2.1 may serve as a structural template from which potent compounds for the treatment of various diseases mediated by this channel subfamily, such as cardiac arrhythmia, can be developed.
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Affiliation(s)
- Tamsyn A Hilder
- Computational Biophysics Group, Research School of Biology, Australian National University , Canberra, ACT 0200, Australia.
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Gordon D, Chung SH. Extension of Brownian dynamics for studying blockers of ion channels. J Phys Chem B 2012; 116:14285-94. [PMID: 23157405 DOI: 10.1021/jp309751e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present new Brownian dynamics techniques for studying blockers of ion channels. By treating the channel as a fixed body, simulating the blocker molecules using rigid bodies, and using an implicit water force field with explicit ions, we are able to carry out fast simulations that can be used to investigate the dynamics of block and unblock, deduce binding modes, and calculate binding affinities. We test our program using the NavAb bacterial sodium channel, whose structure was recently solved (Payandeh et al. Nature, 2011, 475, 353-358) in conjunction with the μ-conotoxin PIIIA blocker. We derive an ohmic current-voltage relationship for channel permeation, calculate potentials of mean force for blocker unbinding, and deduce multiple binding modes for the blocker. Our results are shown to be compatible with other computational and experimental results. Finally, we discuss future improvements such as the inclusion of flexible side chains. After these improvements are carried out, we anticipate our program will be an extremely useful new tool that could be used to help develop new drugs to treat a range of ion-channel related diseases.
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Affiliation(s)
- Dan Gordon
- Research School of Biology, Building 46, The Australian National University, Canberra, ACT 0200 Australia.
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Abstract
Carbon nanotubes offer exciting opportunities for devising highly-sensitive detectors of specific molecules in biology and the environment. Detection limits as low as 10(-11) M have already been achieved using nanotube-based sensors. We propose the design of a biosensor comprised of functionalized carbon nanotube pores embedded in a silicon-nitride or other membrane, fluorofullerene-Fragment antigen-binding (Fab fragment) conjugates, and polymer beads with complementary Fab fragments. We show by using molecular and stochastic dynamics that conduction through the (9, 9) exohydrogenated carbon nanotubes is 20 times larger than through the Ion Channel Switch ICS(TM) biosensor, and fluorofullerenes block the nanotube entrance with a dissociation constant as low as 37 pM. Under normal operating conditions and in the absence of analyte, fluorofullerenes block the nanotube pores and the polymer beads float around in the reservoir. When analyte is injected into the reservoir the Fab fragments attached to the fluorofullerene and polymer bead crosslink to the analyte. The drag of the much larger polymer bead then acts to pull the fluorofullerene from the nanotube entrance, thereby allowing the flow of monovalent cations across the membrane. Assuming a tight seal is formed between the two reservoirs, such a biosensor would be able to detect one channel opening and thus one molecule of analyte making it a highly sensitive detection design.
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Affiliation(s)
- Tamsyn A. Hilder
- Computational Biophysics Group, Research School of Biology, Australian National University, Acton, ACT 0200, Australia; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +61-2-6125-4034; Fax: +61-2-6125-0739
| | - Ron J. Pace
- Biophysical Chemistry, Research School of Chemistry, Australian National University, Acton, ACT 0200, Australia; E-Mail:
| | - Shin-Ho Chung
- Computational Biophysics Group, Research School of Biology, Australian National University, Acton, ACT 0200, Australia; E-Mail:
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Chen R, Chung SH. Structural basis of the selective block of Kv1.2 by maurotoxin from computer simulations. PLoS One 2012; 7:e47253. [PMID: 23071772 PMCID: PMC3468451 DOI: 10.1371/journal.pone.0047253] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 09/12/2012] [Indexed: 12/22/2022] Open
Abstract
The 34-residue polypeptide maurotoxin (MTx) isolated from scorpion venoms selectively inhibits the current of the voltage-gated potassium channel Kv1.2 by occluding the ion conduction pathway. Here using molecular dynamics simulation as a docking method, the binding modes of MTx to three closely related channels (Kv1.1, Kv1.2 and Kv1.3) are examined. We show that MTx forms more favorable electrostatic interactions with the outer vestibule of Kv1.2 compared to Kv1.1 and Kv1.3, consistent with the selectivity of MTx for Kv1.2 over Kv1.1 and Kv1.3 observed experimentally. One salt bridge in the bound complex of MTx-Kv1.2 forms and breaks in a simulation period of 20ns, suggesting the dynamic nature of toxin-channel interactions. The toxin selectivity likely arises from the differences in the shape of the channel outer vestibule, giving rise to distinct orientations of MTx on block. Potential of mean force calculations show that MTx blocks Kv1.1, Kv1.2 and Kv1.3 with an IC50 value of 6 µM, 0.6nM and 18 µM, respectively.
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Affiliation(s)
- Rong Chen
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
- * E-mail: (RC); (S-HC)
| | - Shin-Ho Chung
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
- * E-mail: (RC); (S-HC)
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Conductance properties of the inwardly rectifying channel, Kir3.2: molecular and Brownian dynamics study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:471-8. [PMID: 23022491 DOI: 10.1016/j.bbamem.2012.09.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 09/17/2012] [Accepted: 09/20/2012] [Indexed: 02/08/2023]
Abstract
Using the recently unveiled crystal structure, and molecular and Brownian dynamics simulations, we elucidate several conductance properties of the inwardly rectifying potassium channel, Kir3.2, which is implicated in cardiac and neurological disorders. We show that the pore is closed by a hydrophobic gating mechanism similar to that observed in Kv1.2. Once open, potassium ions move into, but not out of, the cell. The asymmetrical current-voltage relationship arises from the lack of negatively charged residues at the narrow intracellular mouth of the channel. When four phenylalanine residues guarding the intracellular gate are mutated to glutamate residues, the channel no longer shows inward rectification. Inward rectification is restored in the mutant Kir3.2 when it becomes blocked by intracellular Mg(2+). Tertiapin, a polypeptide toxin isolated from the honey bee, is known to block several subtypes of the inwardly rectifying channels with differing affinities. We identify critical residues in the toxin and Kir3.2 for the formation of the stable complex. A lysine residue of tertiapin protrudes into the selectivity filter of Kir3.2, while two other basic residues of the toxin form hydrogen bonds with acidic residues located just outside the channel entrance. The depth of the potential of mean force encountered by tertiapin is -16.1kT, thus indicating that the channel will be half-blocked by 0.4μM of the toxin.
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Chen R, Chung SH. Binding Modes and Functional Surface of Anti-mammalian Scorpion α-Toxins to Sodium Channels. Biochemistry 2012; 51:7775-82. [DOI: 10.1021/bi300776g] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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
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Rashid MH, Kuyucak S. Affinity and selectivity of ShK toxin for the Kv1 potassium channels from free energy simulations. J Phys Chem B 2012; 116:4812-22. [PMID: 22480371 DOI: 10.1021/jp300639x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The voltage-gated potassium channel Kv1.3 is an attractive target for treatment of autoimmune diseases. ShK toxin from sea anemone is one of the most potent blockers of Kv1.3, and therefore ShK and its analogues have been proposed as therapeutic leads for such diseases. Increasing the selectivity of the proposed leads for Kv1.3 over other Kv1 channels is a major issue in this endeavor. Here we study binding of ShK toxin to Kv1 channels using free energy simulation methods. Homology models for Kv1.1 and Kv1.3 channels are constructed using the crystal structure of Kv1.2. The initial poses for the Kv1.x-ShK complexes are obtained using HADDOCK, which are then refined via molecular dynamics simulations. The binding mode in each complex is characterized by identifying the strongly interacting residues, which compare well with available mutagenesis studies. For each complex, the potential of mean force is calculated from umbrella sampling simulations, and the corresponding absolute binding free energy is determined. The computed binding free energies are in good agreement with the experimental data, which increases the confidence on the model complexes. The insights gained on Kv1.x-ShK binding modes will be valuable in the development of new ShK analogues with better selectivity properties.
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Affiliation(s)
- M Harunur Rashid
- School of Physics, University of Sydney , New South Wales 2006, Australia
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Chen R, Chung SH. Conserved functional surface of antimammalian scorpion β-toxins. J Phys Chem B 2012; 116:4796-800. [PMID: 22471309 DOI: 10.1021/jp300127j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Scorpion β-toxins bind to the voltage-sensing domain of voltage-gated sodium (NaV) channels and trap the voltage-sensing domain in the activated state. Two structurally similar β-toxins from scorpions, Css4 and Cn2, selectively target different subtypes of mammalian NaV channels. While the receptor site on the channels is known, the functional surface of the toxins remains to be understood. Here, we predict the binding modes of Css4 and Cn2 to the voltage-sensing domains of NaV1.2 and NaV1.6, respectively, with a molecular docking method and molecular dynamics simulations. The dissociation constants for the predicted toxin-channel complexes derived with umbrella sampling simulations are in accord with experiment. Our calculations suggest that the functional surface of Cn2 and Css4 is primarily formed by the loop between positions 8 and 18, centered on the two charged residues Lys13 and Glu15.
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Affiliation(s)
- Rong Chen
- Research School of Biology, Australian National University , Canberra, ACT 0200, Australia
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Chen R, Chung SH. Engineering a potent and specific blocker of voltage-gated potassium channel Kv1.3, a target for autoimmune diseases. Biochemistry 2012; 51:1976-82. [PMID: 22352687 DOI: 10.1021/bi201811j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A polypeptide toxin extracted from scorpion venom, OSK1, is modified such that its potency is drastically enhanced in blocking one class of voltage-gated potassium channels, Kv1.3, which is a pharmacological target for immunosuppressive therapy. The bound complex of Kv1.3 and OSK1 reveals that one lysine residue of the toxin is in the proximity of another lysine residue on the external vestibule of the channel, just outside of the selectivity filter. This unfavorable electrostatic interaction is eliminated by interchanging the positions of two amino acids in the toxin. The potentials of mean force of the wild-type and mutant OSK1 bound to Kv1.1-Kv1.3 channels are constructed using molecular dynamics, and the half-maximal inhibitory concentration (IC(50)) of each toxin-channel complex is computed. We show that the IC(50) values predicted for three toxins and three channels match closely with experiment. Kv1.3 is half-blocked by 0.2 pM mutant OSK1; it is >10000-fold more specific for this channel than for Kv1.1 and Kv1.2.
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Affiliation(s)
- Rong Chen
- Research School of Biology, Australian National University, Canberra, ACT 0200, Australia.
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Chen R, Chung SH. Binding modes of μ-conotoxin to the bacterial sodium channel (NaVAb). Biophys J 2012; 102:483-8. [PMID: 22325270 DOI: 10.1016/j.bpj.2011.12.041] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 12/14/2011] [Accepted: 12/27/2011] [Indexed: 12/19/2022] Open
Abstract
Polypeptide toxins isolated from the venom of cone snails, known as μ-conotoxins, block voltage-gated sodium channels by physically occluding the ion-conducting pathway. Using molecular dynamics, we show that one subtype of μ-conotoxins, PIIIA, effectively blocks the bacterial voltage-gated sodium channel Na(V)Ab, whose crystal structure has recently been elucidated. The spherically shaped toxin, carrying a net charge of +6 e with six basic residues protruding from its surface, is attracted by the negatively charged residues on the vestibular wall and the selectivity filter of the channel. The side chain of each of these six arginine and lysine residues can wedge into the selectivity filter, whereas the side chains of other basic residues form electrostatic complexes with two acidic residues on the channel. We construct the profile of potential of mean force for the unbinding of PIIIA from the channel, and predict that PIIIA blocks the bacterial sodium channel with subnanomolar affinity.
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Affiliation(s)
- Rong Chen
- Computational Biophysics Group, Research School of Biology, Australian National University, Canberra, Australia.
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