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Characterising ion channel structure and dynamics using fluorescence spectroscopy techniques. Biochem Soc Trans 2022; 50:1427-1445. [DOI: 10.1042/bst20220605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 09/21/2022] [Accepted: 10/04/2022] [Indexed: 11/17/2022]
Abstract
Ion channels undergo major conformational changes that lead to channel opening and ion conductance. Deciphering these structure-function relationships is paramount to understanding channel physiology and pathophysiology. Cryo-electron microscopy, crystallography and computer modelling provide atomic-scale snapshots of channel conformations in non-cellular environments but lack dynamic information that can be linked to functional results. Biophysical techniques such as electrophysiology, on the other hand, provide functional data with no structural information of the processes involved. Fluorescence spectroscopy techniques help bridge this gap in simultaneously obtaining structure-function correlates. These include voltage-clamp fluorometry, Förster resonance energy transfer, ligand binding assays, single molecule fluorescence and their variations. These techniques can be employed to unearth several features of ion channel behaviour. For instance, they provide real time information on local and global rearrangements that are inherent to channel properties. They also lend insights in trafficking, expression, and assembly of ion channels on the membrane surface. These methods have the advantage that they can be carried out in either native or heterologous systems. In this review, we briefly explain the principles of fluorescence and how these have been translated to study ion channel function. We also report several recent advances in fluorescence spectroscopy that has helped address and improve our understanding of the biophysical behaviours of different ion channel families.
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Colom-Casasnovas A, Garay E, Cisneros-Mejorado A, Aguilar MB, Lazcano-Pérez F, Arellano RO, Sánchez-Rodríguez J. Sea anemone Bartholomea annulata venom inhibits voltage-gated Na+ channels and activates GABAA receptors from mammals. Sci Rep 2022; 12:5352. [PMID: 35354863 PMCID: PMC8967859 DOI: 10.1038/s41598-022-09339-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 03/17/2022] [Indexed: 11/18/2022] Open
Abstract
Toxin production in nematocysts by Cnidaria phylum represents an important source of bioactive compounds. Using electrophysiology and, heterologous expression of mammalian ion channels in the Xenopus oocyte membrane, we identified two main effects produced by the sea anemone Bartholomea annulata venom. Nematocysts isolation and controlled discharge of their content, revealed that venom had potent effects on both voltage-dependent Na+ (Nav) channels and GABA type A channel receptors (GABAAR), two essential proteins in central nervous system signaling. Unlike many others sea anemone toxins, which slow the inactivation rate of Nav channels, B. annulata venom potently inhibited the neuronal action potential and the Na+ currents generated by distinct Nav channels opening, including human TTX-sensitive (hNav1.6) and TTX-insensitive Nav channels (hNav1.5). A second effect of B. annulata venom was an agonistic action on GABAAR that activated distinct receptors conformed by either α1β2γ2, α3β2γ1 or, ρ1 homomeric receptors. Since GABA was detected in venom samples by ELISA assay at low nanomolar range, it was excluded that GABA from nematocysts directly activated the GABAARs. This revealed that substances in B. annulata nematocysts generated at least two potent and novel effects on mammalian ion channels that are crucial for nervous system signaling.
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Alp M, Pamuk Algi M, Algi F. Tb(III)-DO3A and BODIPY dyad as multimode responsive hypochlorite probe. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 264:120310. [PMID: 34474222 DOI: 10.1016/j.saa.2021.120310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/16/2021] [Accepted: 08/19/2021] [Indexed: 06/13/2023]
Abstract
A multimode responsive hypochlorite probe 1, based on Terbium (III)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (Tb(III)-DO3A) and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY), is described. We have shown that probe 1 can detect ClO- by absorption, fluorescence, and phosphorescence simultaneously. The multimode response makes probe 1 a versatile ClO- probe for practical applications. We have found that probe 1 can be used in naked-eye colorimetric and fluorogenic detection of NaOCl in solution. Also, we have constructed a colorimetric test paper for visual sensing of NaOCl. Furthermore, fluorescence imaging studies indicated that probe 1 was a versatile tool for in vitro imaging of NaOCl in living cells. Thus, to the best of our knowledge, probe 1 represents one of the rare examples of multimode responsive ClO- probes.
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Affiliation(s)
- Meltem Alp
- Department of Biotechnology & ASUBTAM Memduh Bilmez BioNanoTech Lab. Aksaray University, TR-68100 Aksaray, Turkey
| | - Melek Pamuk Algi
- Department of Chemistry & ASUBTAM Memduh Bilmez BioNanoTech Lab. Aksaray University, TR-68100 Aksaray, Turkey
| | - Fatih Algi
- Department of Biotechnology & ASUBTAM Memduh Bilmez BioNanoTech Lab. Aksaray University, TR-68100 Aksaray, Turkey.
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Israel MR, Dash TS, Bothe SN, Robinson SD, Deuis JR, Craik DJ, Lampert A, Vetter I, Durek T. Characterization of Synthetic Tf2 as a Na V1.3 Selective Pharmacological Probe. Biomedicines 2020; 8:biomedicines8060155. [PMID: 32545167 PMCID: PMC7345637 DOI: 10.3390/biomedicines8060155] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/02/2020] [Accepted: 06/05/2020] [Indexed: 12/17/2022] Open
Abstract
NaV1.3 is a subtype of the voltage-gated sodium channel family. It has been implicated in the pathogenesis of neuropathic pain, although the contribution of this channel to neuronal excitability is not well understood. Tf2, a β-scorpion toxin previously identified from the venom of Tityus fasciolatus, has been reported to selectively activate NaV1.3. Here, we describe the activity of synthetic Tf2 and assess its suitability as a pharmacological probe for NaV1.3. As described for the native toxin, synthetic Tf2 (1 µM) caused early channel opening, decreased the peak current, and shifted the voltage dependence of NaV1.3 activation in the hyperpolarizing direction by −11.3 mV, with no activity at NaV1.1, NaV1.2, and NaV1.4-NaV1.8. Additional activity was found at NaV1.9, tested using the hNav1.9_C4 chimera, where Tf2 (1 µM) shifted the voltage dependence of activation by −6.3 mV. In an attempt to convert Tf2 into an NaV1.3 inhibitor, we synthetized the analogue Tf2[S14R], a mutation previously described to remove the excitatory activity of related β-scorpion toxins. Indeed, Tf2[S14R](10 µM) had reduced excitatory activity at NaV1.3, although it still caused a small −5.8 mV shift in the voltage dependence of activation. Intraplantar injection of Tf2 (1 µM) in mice caused spontaneous flinching and swelling, which was not reduced by the NaV1.1/1.3 inhibitor ICA-121431 nor in NaV1.9-/- mice, suggesting off-target activity. In addition, despite a loss of excitatory activity, intraplantar injection of Tf2[S14R](10 µM) still caused swelling, providing strong evidence that Tf2 has additional off-target activity at one or more non-neuronal targets. Therefore, due to activity at NaV1.9 and other yet to be identified target(s), the use of Tf2 as a selective pharmacological probe may be limited.
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Affiliation(s)
- Mathilde R. Israel
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia; (M.R.I.); (T.S.D.); (S.D.R.); (J.R.D.); (D.J.C.)
| | - Thomas S. Dash
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia; (M.R.I.); (T.S.D.); (S.D.R.); (J.R.D.); (D.J.C.)
| | - Stefanie N. Bothe
- Institute of Physiology, Medical Faculty, RWTH Aachen University, 52074 Aachen, Germany; (S.N.B.); (A.L.)
- Research Training Group 2416 MultiSenses-MultiScales, RWTH Aachen University, 52074 Aachen, Germany
| | - Samuel D. Robinson
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia; (M.R.I.); (T.S.D.); (S.D.R.); (J.R.D.); (D.J.C.)
| | - Jennifer R. Deuis
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia; (M.R.I.); (T.S.D.); (S.D.R.); (J.R.D.); (D.J.C.)
| | - David J. Craik
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia; (M.R.I.); (T.S.D.); (S.D.R.); (J.R.D.); (D.J.C.)
| | - Angelika Lampert
- Institute of Physiology, Medical Faculty, RWTH Aachen University, 52074 Aachen, Germany; (S.N.B.); (A.L.)
- Research Training Group 2416 MultiSenses-MultiScales, RWTH Aachen University, 52074 Aachen, Germany
- Research Training Group 2415 ME3T, RWTH Aachen University, 52074 Aachen, Germany
| | - Irina Vetter
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia; (M.R.I.); (T.S.D.); (S.D.R.); (J.R.D.); (D.J.C.)
- School of Pharmacy, The University of Queensland, Woolloongabba, QLD 4102, Australia
- Correspondence: (I.V.); (T.D.); Tel.: +61-7-3346-2660 (I.V.); +61-7-3346-2021 (T.D.)
| | - Thomas Durek
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia; (M.R.I.); (T.S.D.); (S.D.R.); (J.R.D.); (D.J.C.)
- Correspondence: (I.V.); (T.D.); Tel.: +61-7-3346-2660 (I.V.); +61-7-3346-2021 (T.D.)
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Carvalho-de-Souza JL, Nag OK, Oh E, Huston AL, Vurgaftman I, Pepperberg DR, Bezanilla F, Delehanty JB. Cholesterol Functionalization of Gold Nanoparticles Enhances Photoactivation of Neural Activity. ACS Chem Neurosci 2019; 10:1478-1487. [PMID: 30589551 DOI: 10.1021/acschemneuro.8b00486] [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] [Indexed: 12/16/2022] Open
Abstract
Gold nanoparticles (AuNPs) attached to the extracellular leaflet of the plasma membrane of neurons can enable the generation of action potentials (APs) in response to brief pulses of light. Recently described techniques to stably bind AuNP bioconjugates directly to membrane proteins (ion channels) in neurons enable robust AP generation mediated by the photoexcited conjugate. However, a strategy that binds the AuNP to the plasma membrane in a non protein-specific manner could represent a simple, single-step means of establishing light-responsiveness in multiple types of excitable neurons contained in the same tissue. On the basis of the ability of cholesterol to insert into the plasma membrane, here we test whether AuNP functionalization with linear dihydrolipoic acid-poly(ethylene) glycol (DHLA-PEG) chains that are distally terminated with cholesterol (AuNP-PEG-Chol) can enable light-induced AP generation in neurons. Dorsal root ganglion (DRG) neurons of rat were labeled with 20 nm diameter spherical AuNP-PEG-Chol conjugates wherein ∼30% of the surface ligands (DHLA-PEG-COOH) were conjugated to PEG-Chol. Voltage recordings under current-clamp conditions showed that DRG neurons labeled in this manner exhibited a capacity for AP generation in response to microsecond and millisecond pulses of 532 nm light, a property attributable to the close tethering of AuNP-PEG-Chol conjugates to the plasma membrane facilitated by the cholesterol moiety. Light-induced AP and subthreshold depolarizing responses of the DRG neurons were similar to those previously described for AuNP conjugates targeted to channel proteins using large, multicomponent immunoconjugates. This likely reflected the AuNP-PEG-Chol's ability, upon plasmonic light absorption and resultant slight and rapid heating of the plasma membrane, to induce a concomitant transmembrane depolarizing capacitive current. Notably, AuNP-PEG-Chol delivered to DRG neurons by inclusion in the buffer contained in the recording pipet/electrode enabled similar light-responsiveness, consistent with the activity of AuNP-PEG-Chol bound to the inner (cytofacial) leaflet of the plasma membrane. Our results demonstrate the ability of AuNP-PEG-Chol conjugates to confer timely stable and direct responsiveness to light in neurons. Further, this strategy represents a general approach for establishing excitable cell photosensitivity that could be of substantial advantage for exploring a given tissue's suitability for AuNP-mediated photocontrol of neural activity.
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Affiliation(s)
- Joao L. Carvalho-de-Souza
- Department of Biochemistry and Molecular Biology and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Okhil K. Nag
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Code 6900, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - Eunkeu Oh
- Optical Sciences Division, Naval Research Laboratory, Code 5600, 4555 Overlook Avenue SW, Washington, DC 20375, United States
- Key W Corporation, Hanover, Maryland 21076, United States
| | - Alan L. Huston
- Optical Sciences Division, Naval Research Laboratory, Code 5600, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - Igor Vurgaftman
- Optical Sciences Division, Naval Research Laboratory, Code 5600, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - David R. Pepperberg
- Lions of Illinois Eye Research Institute, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, United States
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - James B. Delehanty
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Code 6900, 4555 Overlook Avenue SW, Washington, DC 20375, United States
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Martin-Eauclaire MF, Bougis PE, de Lima ME. Ts1 from the Brazilian scorpion Tityus serrulatus: A half-century of studies on a multifunctional beta like-toxin. Toxicon 2018; 152:106-120. [PMID: 30059695 DOI: 10.1016/j.toxicon.2018.07.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 07/18/2018] [Accepted: 07/24/2018] [Indexed: 12/19/2022]
Abstract
The Tityus serrulatus scorpion species represents a serious human health threat to in Brazil because it is among the animals that produces the most dangerous venoms for mammals in South America. Its venom has provided several highly selective ligands that specifically interact with sodium and potassium channels. During the past decades, several international groups published an increasing amount of data on the isolation and the chemical, pharmacological and immunological characterisation of its main β-toxin, Ts1. In this review, we compiled the best available past and recent knowledge on Ts1. Aside from its intricate purification, the state-of-the-art understanding concerning its pharmacological activities is presented. Its solved three-dimensional structure is shown, as well as the possible surface areas of contact between Ts1 and its diverse voltage-gated Na+ channel targets. Organisations of the gene and the precursor encoding Ts1 are also tackled based on available cDNA clones or on information obtained from polymerase chain reactions of stretches of scorpion DNA. At last, the immunological studies complete with Ts1 to set up an efficient immunotherapy against the Tityus serrulatus venom are summarized.
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Affiliation(s)
| | - Pierre E Bougis
- Aix Marseille Univ, CNRS, LNC, UMR 7291, 13003, Marseille, France.
| | - Maria Elena de Lima
- Laboratório de Venenos e Toxinas Animais, Depto de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901, Belo Horizonte, MG, Brazil; Instituto de Ensino e Pesquisa da Santa Casa de Belo Horizonte - IEP/SCBH, 30150-240, Belo Horizonte, MG, Brazil.
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7
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Israel MR, Thongyoo P, Deuis JR, Craik DJ, Vetter I, Durek T. The E15R Point Mutation in Scorpion Toxin Cn2 Uncouples Its Depressant and Excitatory Activities on Human NaV1.6. J Med Chem 2018; 61:1730-1736. [DOI: 10.1021/acs.jmedchem.7b01609] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Mathilde R. Israel
- Institute
for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Panumart Thongyoo
- Institute
for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Jennifer R. Deuis
- Institute
for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - David J. Craik
- Institute
for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Irina Vetter
- Institute
for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
- School
of Pharmacy, The University of Queensland, Woolloongabba, Queensland 4102, Australia
| | - Thomas Durek
- Institute
for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
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