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Cristofori-Armstrong B, Budusan E, Smith JJ, Reynaud S, Voll K, Chassagnon IR, Durek T, Rash LD. Revealing molecular determinants governing mambalgin-3 pharmacology at acid-sensing ion channel 1 variants. Cell Mol Life Sci 2024; 81:266. [PMID: 38880807 DOI: 10.1007/s00018-024-05276-2] [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: 01/22/2024] [Revised: 04/19/2024] [Accepted: 05/12/2024] [Indexed: 06/18/2024]
Abstract
Acid-sensing ion channels (ASICs) are trimeric proton-gated cation channels that play a role in neurotransmission and pain sensation. The snake venom-derived peptides, mambalgins, exhibit potent analgesic effects in rodents by inhibiting central ASIC1a and peripheral ASIC1b. Despite their distinct species- and subtype-dependent pharmacology, previous structure-function studies have focussed on the mambalgin interaction with ASIC1a. Currently, the specific channel residues responsible for this pharmacological profile, and the mambalgin pharmacophore at ASIC1b remain unknown. Here we identify non-conserved residues at the ASIC1 subunit interface that drive differences in the mambalgin pharmacology from rat ASIC1a to ASIC1b, some of which likely do not make peptide binding interactions. Additionally, an amino acid variation below the core binding site explains potency differences between rat and human ASIC1. Two regions within the palm domain, which contribute to subtype-dependent effects for mambalgins, play key roles in ASIC gating, consistent with subtype-specific differences in the peptides mechanism. Lastly, there is a shared primary mambalgin pharmacophore for ASIC1a and ASIC1b activity, with certain peripheral peptide residues showing variant-specific significance for potency. Through our broad mutagenesis studies across various species and subtype variants, we gain a more comprehensive understanding of the pharmacophore and the intricate molecular interactions that underlie ligand specificity. These insights pave the way for the development of more potent and targeted peptide analogues required to advance our understating of human ASIC1 function and its role in disease.
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Affiliation(s)
- Ben Cristofori-Armstrong
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Elena Budusan
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia
- Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland
| | - Jennifer J Smith
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
- Genentech, 1 DNA Way, South San Francisco, CA, 94080, United States
| | - Steve Reynaud
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
- In Extenso Innovation Growth, Lyon, France
| | - Kerstin Voll
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
- Boehringer Ingelheim Pharma GmbH & Co. KG, Birkendorfer Str. 65, 88397, Biberach an der Riß, Germany
| | - Irène R Chassagnon
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
- Servatus Ltd. Coolum Beach, Coolum Beach, QLD, Australia
| | - Thomas Durek
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Lachlan D Rash
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia.
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Budusan E, Payne CD, Gonzalez TI, Obergrussberger A, Becker N, Clark RJ, Johan Rosengren K, Rash LD, Cristofori-Armstrong B. The funnel-web spider venom derived single knot peptide Hc3a modulates acid-sensing ion channel 1a desensitisation. Biochem Pharmacol 2024:116175. [PMID: 38552850 DOI: 10.1016/j.bcp.2024.116175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Revised: 03/17/2024] [Accepted: 03/26/2024] [Indexed: 04/07/2024]
Abstract
Acid-sensing ion channel 1a (ASIC1a) is a proton-gated channel involved in synaptic transmission, pain signalling, and several ischemia-associated pathological conditions. The spider venom-derived peptides PcTx1 and Hi1a are two of the most potent ASIC1a inhibitors known and have been instrumental in furthering our understanding of the structure, function, and biological roles of ASICs. To date, homologous spider peptides with different pharmacological profiles at ASIC1a have yet to be discovered. Here we report the characterisation of Hc3a, a single inhibitor cystine knot peptide from the Australian funnel-web spider Hadronyche cerberea with sequence similarity to PcTx1. We show that Hc3a has complex pharmacology and binds different ASIC1a conformational states (closed, open, and desensitised) with different affinities, with the most prominent effect on desensitisation. Hc3a slows the desensitisation kinetics of proton-activated ASIC1a currents across multiple application pHs, and when bound directly to ASIC1a in the desensitised conformation promotes current inhibition. The solution structure of Hc3a was solved, and the peptide-channel interaction examined via mutagenesis studies to highlight how small differences in sequence between Hc3a and PcTx1 can lead to peptides with distinct pharmacology. The discovery of Hc3a expands the pharmacological diversity of spider venom peptides targeting ASIC1a and adds to the toolbox of compounds to study the intricacies of ASIC1 gating.
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Affiliation(s)
- Elena Budusan
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia
| | - Colton D Payne
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia
| | - Tye I Gonzalez
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia
| | | | | | - Richard J Clark
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia
| | - K Johan Rosengren
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia.
| | - Lachlan D Rash
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia.
| | - Ben Cristofori-Armstrong
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD, Australia.
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Smallwood TB, Navarro S, Cristofori-Armstrong B, Watkins TS, Tungatt K, Ryan RYM, Haigh OL, Lutzky VP, Mulvenna JP, Rosengren KJ, Loukas A, Miles JJ, Clark RJ. Synthetic hookworm-derived peptides are potent modulators of primary human immune cell function that protect against experimental colitis in vivo. J Biol Chem 2021; 297:100834. [PMID: 34051231 PMCID: PMC8239465 DOI: 10.1016/j.jbc.2021.100834] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 05/21/2021] [Accepted: 05/25/2021] [Indexed: 12/14/2022] Open
Abstract
The prevalence of autoimmune diseases is on the rise globally. Currently, autoimmunity presents in over 100 different forms and affects around 9% of the world's population. Current treatments available for autoimmune diseases are inadequate, expensive, and tend to focus on symptom management rather than cure. Clinical trials have shown that live helminthic therapy can decrease chronic inflammation associated with inflammatory bowel disease and other gastrointestinal autoimmune inflammatory conditions. As an alternative and better controlled approach to live infection, we have identified and characterized two peptides, Acan1 and Nak1, from the excretory/secretory component of parasitic hookworms for their therapeutic activity on experimental colitis. We synthesized Acan1 and Nak1 peptides from the Ancylostoma caninum and Necator americanus hookworms and assessed their structures and protective properties in human cell-based assays and in a mouse model of acute colitis. Acan1 and Nak1 displayed anticolitic properties via significantly reducing weight loss and colon atrophy, edema, ulceration, and necrosis in 2,4,6-trinitrobenzene sulfonic acid-exposed mice. These hookworm peptides prevented mucosal loss of goblet cells and preserved intestinal architecture. Acan1 upregulated genes responsible for the repair and restitution of ulcerated epithelium, whereas Nak1 downregulated genes responsible for epithelial cell migration and apoptotic cell signaling within the colon. These peptides were nontoxic and displayed key immunomodulatory functions in human peripheral blood mononuclear cells by suppressing CD4+ T cell proliferation and inhibiting IL-2 and TNF production. We conclude that Acan1 and Nak1 warrant further development as therapeutics for the treatment of autoimmunity, particularly gastrointestinal inflammatory conditions.
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Affiliation(s)
- Taylor B Smallwood
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, QLD, Australia
| | - Severine Navarro
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia; The Australian Institute of Tropical Health and Medicine, James Cook University, QLD, Australia; Woolworths Centre for Child Nutrition Research, Institute of Health and Biomedical Innovation, Queensland University of Technology, QLD, Australia
| | - Ben Cristofori-Armstrong
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, QLD, Australia
| | - Thomas S Watkins
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia; Centre for Molecular Therapeutics, The Australian Institute of Tropical Health and Medicine, James Cook University, QLD, Australia
| | - Katie Tungatt
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia; Centre for Molecular Therapeutics, The Australian Institute of Tropical Health and Medicine, James Cook University, QLD, Australia; Centre for Tropical Bioinformatics and Molecular Biology, James Cook University, QLD, Australia
| | - Rachael Y M Ryan
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia; The Australian Institute of Tropical Health and Medicine, James Cook University, QLD, Australia; Centre for Molecular Therapeutics, The Australian Institute of Tropical Health and Medicine, James Cook University, QLD, Australia
| | - Oscar L Haigh
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Viviana P Lutzky
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Jason P Mulvenna
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - K Johan Rosengren
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, QLD, Australia
| | - Alex Loukas
- Centre for Molecular Therapeutics, The Australian Institute of Tropical Health and Medicine, James Cook University, QLD, Australia
| | - John J Miles
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia; The Australian Institute of Tropical Health and Medicine, James Cook University, QLD, Australia; Centre for Molecular Therapeutics, The Australian Institute of Tropical Health and Medicine, James Cook University, QLD, Australia; Centre for Tropical Bioinformatics and Molecular Biology, James Cook University, QLD, Australia; Institute of Infection and Immunity, Cardiff University School of Medicine, University Hospital, Cardiff, Wales, United Kingdom.
| | - Richard J Clark
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, QLD, Australia.
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Novel conorfamides from Conus austini venom modulate both nicotinic acetylcholine receptors and acid-sensing ion channels. Biochem Pharmacol 2019; 164:342-348. [PMID: 31028742 DOI: 10.1016/j.bcp.2019.04.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 04/22/2019] [Indexed: 01/06/2023]
Abstract
Conorfamides are a poorly studied family of cone snail venom peptides with broad biological activities, including inhibition of glutamate receptors, acid-sensing ion channels, and voltage-gated potassium channels. The aim of this study was to characterize the pharmacological activity of two novel linear conorfamides (conorfamide_As1a and conorfamide_As2a) and their non-amidated counterparts (conopeptide_As1b and conopeptide_As2b) that were isolated from the venom of the Mexican cone snail Conus austini. Although As1a, As2a, As1b and As2b were identified by activity-guided fractionation using a high-throughput fluorescence imaging plate reader (FLIPR) assay assessing α7 nAChR activity, sequence determination revealed activity associated with four linear peptides of the conorfamide rather than the anticipated α-conotoxin family. Pharmacological testing revealed that the amidated peptide variants altered desensitization of acid-sensing ion channels (ASICs) 1a and 3, and the native lysine to arginine mutation differentiating As1a and As1b from As2a and As2b introduced ASIC1a peak current potentiation. Surprisingly, these conorfamides also inhibited α7 and muscle-type nicotinic acetylcholine receptors (nAChR) at nanomolar concentrations. This is the first report of conorfamides with dual activity, with the nAChR activity being the most potent molecular target of any conorfamide discovered to date.
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Cristofori-Armstrong B, Saez NJ, Chassagnon IR, King GF, Rash LD. The modulation of acid-sensing ion channel 1 by PcTx1 is pH-, subtype- and species-dependent: Importance of interactions at the channel subunit interface and potential for engineering selective analogues. Biochem Pharmacol 2019; 163:381-390. [PMID: 30849303 DOI: 10.1016/j.bcp.2019.03.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 03/04/2019] [Indexed: 01/13/2023]
Abstract
Acid-sensing ion channels (ASICs) are primary acid sensors in the mammalian nervous system that are activated by protons under conditions of local acidosis. They have been implicated in a range of pathologies including ischemic stroke (ASIC1a subtype) and peripheral pain (ASIC1b and ASIC3). Although the spider venom peptide PcTx1 is the best-studied ASIC modulator and is neuroprotective in rodent models of ischemic stroke, little experimental work has been done to examine its molecular interaction with human ASIC1a or the off-target ASIC1b. The complementary face of the acidic pocket binding site of PcTx1 is where these channels differ in sequence. We show here that although PcTx1 is 10-fold less potent at human ASIC1a than the rat channel, the apparent affinity for the two channels is comparable. We examined the pharmacophore of PcTx1 for human ASIC1a and rat ASIC1b, and show that inhibitory and stimulatory effects at each ASIC1 variant is driven mostly by a shared set of core peptide pharmacophore residues that bind to the thumb domain, while peptide residues that interact with the complementary face of the biding site underlie species and subtype-dependent differences in activity that may allow manipulation of ASIC1 variant selectivity. Finally, the stimulatory effect of PcTx1 on rat ASIC1a when applied under mildly alkaline pH correlates with low receptor occupancy. These new insights into the interactions between PcTx1 with ASIC1 subtypes demonstrates the complexity of its mechanism of action, and highlights important implications to consider when using PcTx1 as a pharmacological tool to study ASIC function.
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Affiliation(s)
- Ben Cristofori-Armstrong
- School of Biomedical Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia; Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Natalie J Saez
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Irène R Chassagnon
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Lachlan D Rash
- School of Biomedical Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia.
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Rojas V, Ortiz YY, Rodríguez S, Araque V, Rodríguez-Acosta A, Figarella K, Uzcátegui NL. Rhinella marina oocytes: a suitable alternative expression system for functional characterization of aquaglyceroporins. Sci Rep 2019; 9:18. [PMID: 30631140 PMCID: PMC6328568 DOI: 10.1038/s41598-018-37069-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 11/29/2018] [Indexed: 01/25/2023] Open
Abstract
Amphibian oocytes have been extensively used for heterologous expression of membrane proteins for studying their biochemical and biophysical properties. So far, Xenopus laevis is the main amphibian used as oocytes source to express aquaglyceroporins in order to assess water and solutes permeability. However, this well-established amphibian model represents a threat to the biodiversity in many countries, especially in those from tropical regions. For that reason, the import of Xenopus laevis is subjected to strict control, which essentially has restricted its use in these regions. Therefore, a wider variety of expression systems for aquaglyceroporins is needed. Rhinella marina is extensively distributed in the Americas and its native range spreads from South America to Texas, US. Here we report the use of Rhinella marina oocytes as an alternative expression system for aquaglyceroporins and demonstrated its suitability to determine the permeability to water and non-ionic solutes. Rhinella marina oocytes were able to functionally express channels from human and the protozoan pathogen Trypanosoma brucei, two very distant organisms on the evolutionary scale. Permeability values obtained from Rhinella marina oocytes expressing members of aquaporin family were similar and comparable to those values reported in the literature for the same channels expressed in Xenopus laevis oocytes.
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Affiliation(s)
- Vania Rojas
- Laboratorio de Inmunoquímica y Ultraestructura, Instituto Anatómico "José Izquierdo", Universidad Central de Venezuela, Caracas, Venezuela
| | - Yulexi Y Ortiz
- Laboratorio de Inmunoquímica y Ultraestructura, Instituto Anatómico "José Izquierdo", Universidad Central de Venezuela, Caracas, Venezuela
| | - Sheridan Rodríguez
- Laboratorio de Inmunoquímica y Ultraestructura, Instituto Anatómico "José Izquierdo", Universidad Central de Venezuela, Caracas, Venezuela
| | - Vladimir Araque
- Laboratorio de Inmunoquímica y Ultraestructura, Instituto Anatómico "José Izquierdo", Universidad Central de Venezuela, Caracas, Venezuela
| | - Alexis Rodríguez-Acosta
- Laboratorio de Inmunoquímica y Ultraestructura, Instituto Anatómico "José Izquierdo", Universidad Central de Venezuela, Caracas, Venezuela
| | - Katherine Figarella
- Institute of Physiology, Department of Neurophysiology, Eberhard Karls University of Tübingen, Tübingen, Germany
| | - Néstor L Uzcátegui
- Laboratorio de Inmunoquímica y Ultraestructura, Instituto Anatómico "José Izquierdo", Universidad Central de Venezuela, Caracas, Venezuela.
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Abstract
The Xenopus oocyte is a specialized single cell of colossal size (>1 mm diameter) that is highly amenable for microinjection and a stalwart model for heterologous expression. Oocytes are easily obtainable, robust in vitro, and faithfully express injected constructs. Their large size translational capacity provides a huge canvas for observing and recording integrated cellular responses-from studies of single molecules within single cells to medium-throughput drug-screening applications. Most eukaryotic promoters suffice for Xenopus expression, and the oocyte can functionally express proteins from many diverse organisms. This protocol provides a basic introduction for scientists keen to perform nuclear microinjections of cDNA constructs. These are easy methods to master, do not require elaborate equipment, and make accessible a wonderful model cell system for studying signaling, transport, cell architecture, and protein function.
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Kabutomori J, Beloto-Silva O, Geyer RR, Musa-Aziz R. Lithobates catesbeianus (American Bullfrog) oocytes: a novel heterologous expression system for aquaporins. Biol Open 2018. [PMID: 29530931 PMCID: PMC5936062 DOI: 10.1242/bio.031880] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Xenopus laevis oocytes are a valuable tool for investigating the function of membrane proteins. However, regulations around the world, specifically in Brazil, render the import of Xenopus laevis frogs impractical, and, in some cases, impossible. Here, as an alternative, we evaluate the usefulness of the North American aquatic bullfrog Lithobates catesebeianus, which is commercially available in Brazil, for the heterologous expression of aquaporin (AQP) proteins. We have developed a method that combines a brief collagenase treatment and mechanical defolliculation for isolating individual oocytes from Lithobates ovaries. We find that they have a similar size, shape, and appearance to Xenopus oocytes and can tolerate and survive following injections with cRNA or water. Furthermore, surface biotinylation, western blot analysis, and measurements of osmotic water permeability (Pf) show that Lithobates oocytes can express AQPs to the plasma membrane and significantly increase the Pf of the oocytes. In fact, the Pf values are similar to historical values gathered from Xenopus oocytes. Due to the presence of a mercury sensitive cysteine (Cys or C) in the throat of the water channel, the Pf of oocytes expressing human (h) AQP1, hAQP1FLAG [FLAG, short protein tag (DYKDDDDK) added to the N-terminus of AQP1], hAQP8, and rat (r) AQP9 was inhibited with the mercurial compound p-chloromercuribenzene sulfonate (pCMBS), whereas AQPs lacking this Cys - hAQP1C189S mutant [residue Cys 189 was replaced by a serine (Ser or S)] and hAQP7 - were mercury insensitive. Contrary to previous studies with Xenopus oocytes, rAQP3 was also found to be insensitive to mercury, which is consistent with the mercury-sensitive Cys (Cys 11) being located intracellularly. Thus, we consider Lithobates oocytes to be a readily accessible system for the functional expression and study of membrane proteins for international researchers who do not currently have access to Xenopus oocytes.
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Affiliation(s)
- Jessica Kabutomori
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Olivia Beloto-Silva
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil.,Department of Health Sciences, Paulista University (UNIP), Sao Paulo 06542-001, Brazil
| | - R Ryan Geyer
- Department of Biochemistry, Institute of Chemistry, University of Sao Paulo, Sao Paulo 05513-970, Brazil
| | - Raif Musa-Aziz
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
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Lee JYP, Saez NJ, Cristofori-Armstrong B, Anangi R, King GF, Smith MT, Rash LD. Inhibition of acid-sensing ion channels by diminazene and APETx2 evoke partial and highly variable antihyperalgesia in a rat model of inflammatory pain. Br J Pharmacol 2018; 175:2204-2218. [PMID: 29134638 DOI: 10.1111/bph.14089] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 10/22/2017] [Accepted: 10/31/2017] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND PURPOSE Acid-sensing ion channels (ASICs) are primary acid sensors in mammals, with the ASIC1b and ASIC3 subtypes being involved in peripheral nociception. The antiprotozoal drug diminazene is a moderately potent ASIC inhibitor, but its analgesic activity has not been assessed. EXPERIMENTAL APPROACH We determined the ASIC subtype selectivity of diminazene and the mechanism by which it inhibits ASICs using voltage-clamp electrophysiology of Xenopus oocytes expressing ASICs 1-3. Its peripheral analgesic activity was then assessed relative to APETx2, an ASIC3 inhibitor, and morphine, in a Freund's complete adjuvant (FCA)-induced rat model of inflammatory pain. KEY RESULTS Diminazene inhibited homomeric rat ASICs with IC50 values of ~200-800 nM, via an open channel and subtype-dependent mechanism. In rats with FCA-induced inflammatory pain in one hindpaw, diminazene and APETx2 evoked more potent peripheral antihyperalgesia than morphine, but the effect was partial for APETx2. APETx2 potentiated rat ASIC1b at concentrations 30-fold to 100-fold higher than the concentration inhibiting ASIC3, which may have implications for its use in in vivo experiments. CONCLUSIONS AND IMPLICATIONS Diminazene and APETx2 are moderately potent ASIC inhibitors, both inducing peripheral antihyperalgesia in a rat model of chronic inflammatory pain. APETx2 has a more complex ASIC pharmacology, which must be considered when it is used as a supposedly selective ASIC3 inhibitor in vivo. Our use of outbred rats revealed responders and non-responders when ASIC inhibition was used to alleviate inflammatory pain, which is aligned with the concept of number-needed-to-treat in human clinical studies. LINKED ARTICLES This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.
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Affiliation(s)
- Jia Yu Peppermint Lee
- UQ Centre for Clinical Research, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia
| | - Natalie J Saez
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | | | - Raveendra Anangi
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Maree T Smith
- UQ Centre for Clinical Research, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia.,School of Pharmacy, The University of Queensland, St Lucia, QLD, Australia
| | - Lachlan D Rash
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia.,School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia
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Lei N, Mellem JE, Brockie PJ, Madsen DM, Maricq AV. NRAP-1 Is a Presynaptically Released NMDA Receptor Auxiliary Protein that Modifies Synaptic Strength. Neuron 2017; 96:1303-1316.e6. [DOI: 10.1016/j.neuron.2017.11.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 10/20/2017] [Accepted: 11/14/2017] [Indexed: 12/19/2022]
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Acid-sensing ion channel (ASIC) structure and function: Insights from spider, snake and sea anemone venoms. Neuropharmacology 2017; 127:173-184. [PMID: 28457973 DOI: 10.1016/j.neuropharm.2017.04.042] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Revised: 04/07/2017] [Accepted: 04/27/2017] [Indexed: 01/14/2023]
Abstract
Acid-sensing ion channels (ASICs) are proton-activated cation channels that are expressed in a variety of neuronal and non-neuronal tissues. As proton-gated channels, they have been implicated in many pathophysiological conditions where pH is perturbed. Venom derived compounds represent the most potent and selective modulators of ASICs described to date, and thus have been invaluable as pharmacological tools to study ASIC structure, function, and biological roles. There are now ten ASIC modulators described from animal venoms, with those from snakes and spiders favouring ASIC1, while the sea anemones preferentially target ASIC3. Some modulators, such as the prototypical ASIC1 modulator PcTx1 have been studied in great detail, while some of the newer members of the club remain largely unstudied. Here we review the current state of knowledge on venom derived ASIC modulators, with a particular focus on their molecular interaction with ASICs, what they have taught us about channel structure, and what they might still reveal about ASIC function and pathophysiological roles. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Rash LD. Acid-Sensing Ion Channel Pharmacology, Past, Present, and Future …. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2017; 79:35-66. [PMID: 28528673 DOI: 10.1016/bs.apha.2017.02.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
pH is one of the most strictly controlled parameters in mammalian physiology. An extracellular pH of ~7.4 is crucial for normal physiological processes, and perturbations to this have profound effects on cell function. Acidic microenvironments occur in many physiological and pathological conditions, including inflammation, bone remodeling, ischemia, trauma, and intense synaptic activity. Cells exposed to these conditions respond in different ways, from tumor cells that thrive to neurons that are either suppressed or hyperactivated, often fatally. Acid-sensing ion channels (ASICs) are primary pH sensors in mammals and are expressed widely in neuronal and nonneuronal cells. There are six main subtypes of ASICs in rodents that can form homo- or heteromeric channels resulting in many potential combinations. ASICs are present and activated under all of the conditions mentioned earlier, suggesting that they play an important role in how cells respond to acidosis. Compared to many other ion channel families, ASICs were relatively recently discovered-1997-and there is a substantial lack of potent, subtype-selective ligands that can be used to elucidate their structural and functional properties. In this chapter I cover the history of ASIC channel pharmacology, which began before the proteins were even identified, and describe the current arsenal of tools available, their limitations, and take a glance into the future to predict from where new tools are likely to emerge.
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Affiliation(s)
- Lachlan D Rash
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia.
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Er SY, Cristofori-Armstrong B, Escoubas P, Rash LD. Discovery and molecular interaction studies of a highly stable, tarantula peptide modulator of acid-sensing ion channel 1. Neuropharmacology 2017; 127:185-195. [PMID: 28327374 DOI: 10.1016/j.neuropharm.2017.03.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 03/05/2017] [Accepted: 03/17/2017] [Indexed: 12/17/2022]
Abstract
Acute pharmacological inhibition of acid-sensing ion channel 1a (ASIC1a) is efficacious in rodent models in alleviating symptoms of neurological diseases such as stroke and multiple sclerosis. Thus, ASIC1a is a promising therapeutic target and selective ligands that modulate it are invaluable research tools and potential therapeutic leads. Spider venoms have provided an abundance of voltage-gated ion channel modulators, however, only one ASIC modulator (PcTx1) has so far been isolated from this source. Here we report the discovery, characterization, and chemical stability of a second spider venom peptide that potently modulates ASIC1a and ASIC1b, and investigate the molecular basis for its subtype selectivity. π-TRTX-Hm3a (Hm3a) is a 37-amino acid peptide isolated from Togo starburst tarantula (Heteroscodra maculata) venom with five amino acid substitutions compared to PcTx1, and is also three residues shorter at the C-terminus. Hm3a pH-dependently inhibited ASIC1a with an IC50 of 1-2 nM and potentiated ASIC1b with an EC50 of 46.5 nM, similar to PcTx1. Using ASIC1a to ASIC1b point mutants in rat ASIC1a revealed that Glu177 and Arg175 in the palm region opposite α-helix 5 play an important role in the Hm3a-ASIC1 interaction and contribute to the subtype-dependent effects of the peptide. Despite its high sequence similarity with PcTx1, Hm3a showed higher levels of stability over 48 h. Overall, Hm3a represents a potent, highly stable tool for the study of ASICs and will be particularly useful when stability in biological fluids is required, for example in long term in vitro cell-based assays and in vivo experiments. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- Sing Yan Er
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia
| | | | - Pierre Escoubas
- VenomeTech, 473 Route des Dolines, Villa 3, 06560 Valbonne, France
| | - Lachlan D Rash
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia; School of Biomedical Sciences, The University of Queensland, St Lucia, QLD 4072, Australia.
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