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Guan W, Orellana KG, Stephens RF, Zhorov BS, Spafford JD. A lysine residue from an extracellular turret switches the ion preference in a Cav3 T-Type channel from calcium to sodium ions. J Biol Chem 2022; 298:102621. [PMID: 36272643 PMCID: PMC9694082 DOI: 10.1016/j.jbc.2022.102621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 10/07/2022] [Accepted: 10/10/2022] [Indexed: 11/19/2022] Open
Abstract
Cav3 T-type calcium channels from great pond snail Lymnaea stagnalis have a selectivity-filter ring of five acidic residues, EE(D)DD. Splice variants with exons 12b or 12a spanning the extracellular loop between the outer helix IIS5 and membrane-descending pore helix IIP1 (IIS5-P1) in Domain II of the pore module possess calcium selectivity or dominant sodium permeability, respectively. Here, we use AlphaFold2 neural network software to predict that a lysine residue in exon 12a is salt-bridged to the aspartate residue immediately C terminal to the second-domain glutamate in the selectivity filter. Exon 12b has a similar folding but with an alanine residue in place of lysine in exon 12a. We express LCav3 channels with mutated exons Ala-12b-Lys and Lys-12a-Ala and demonstrate that they switch the ion preference to high sodium permeability and calcium selectivity, respectively. We propose that in the calcium-selective variants, a calcium ion chelated between Domain II selectivity-filter glutamate and aspartate is knocked-out by the incoming calcium ion in the process of calcium permeation, whereas sodium ions are repelled. The aspartate is neutralized by the lysine residue in the sodium-permeant variants, allowing for sodium permeation through the selectivity-filter ring of four negatively charged residues akin to the prokaryotic sodium channels with four glutamates in the selectivity filter. The evolutionary adaptation in invertebrate LCav3 channels highlight the involvement of a key, ubiquitous aspartate, "a calcium beacon" of sorts in the outer pore of Domain II, as determinative for the calcium ion preference over sodium ions through eukaryotic Cav1, Cav2, and Cav3 channels.
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Affiliation(s)
- Wendy Guan
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Kaidy G. Orellana
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Robert F. Stephens
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Boris S. Zhorov
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada,Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia,Almazov National Medical Research Centre, St. Petersburg, Russia
| | - J. David Spafford
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada,For correspondence: J. David Spafford
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2
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Changes in Ion Selectivity Following the Asymmetrical Addition of Charge to the Selectivity Filter of Bacterial Sodium Channels. ENTROPY 2020; 22:e22121390. [PMID: 33316962 PMCID: PMC7764494 DOI: 10.3390/e22121390] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 11/30/2020] [Accepted: 12/07/2020] [Indexed: 12/30/2022]
Abstract
Voltage-gated sodium channels (NaVs) play fundamental roles in eukaryotes, but their exceptional size hinders their structural resolution. Bacterial NaVs are simplified homologues of their eukaryotic counterparts, but their use as models of eukaryotic Na+ channels is limited by their homotetrameric structure at odds with the asymmetric Selectivity Filter (SF) of eukaryotic NaVs. This work aims at mimicking the SF of eukaryotic NaVs by engineering radial asymmetry into the SF of bacterial channels. This goal was pursued with two approaches: the co-expression of different monomers of the NaChBac bacterial channel to induce the random assembly of heterotetramers, and the concatenation of four bacterial monomers to form a concatemer that can be targeted by site-specific mutagenesis. Patch-clamp measurements and Molecular Dynamics simulations showed that an additional gating charge in the SF leads to a significant increase in Na+ and a modest increase in the Ca2+ conductance in the NavMs concatemer in agreement with the behavior of the population of random heterotetramers with the highest proportion of channels with charge -5e. We thus showed that charge, despite being important, is not the only determinant of conduction and selectivity, and we created new tools extending the use of bacterial channels as models of eukaryotic counterparts.
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A Selectivity Filter Gate Controls Voltage-Gated Calcium Channel Calcium-Dependent Inactivation. Neuron 2019; 101:1134-1149.e3. [DOI: 10.1016/j.neuron.2019.01.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 11/12/2018] [Accepted: 12/31/2018] [Indexed: 11/22/2022]
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Smith CL, Abdallah S, Wong YY, Le P, Harracksingh AN, Artinian L, Tamvacakis AN, Rehder V, Reese TS, Senatore A. Evolutionary insights into T-type Ca 2+ channel structure, function, and ion selectivity from the Trichoplax adhaerens homologue. J Gen Physiol 2017; 149:483-510. [PMID: 28330839 PMCID: PMC5379919 DOI: 10.1085/jgp.201611683] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Accepted: 02/07/2017] [Indexed: 12/31/2022] Open
Abstract
The role of T-type calcium channels in animals without nervous systems is unknown. Smith et al. characterize TCav3 from Trichoplax adhaerens, finding expression in neurosecretory-like cells and preference for Ca2+ over Na+ via strong extracellular Ca2+ block, despite low selectivity for Ca2+ in the pore. Four-domain voltage-gated Ca2+ (Cav) channels play fundamental roles in the nervous system, but little is known about when or how their unique properties and cellular roles evolved. Of the three types of metazoan Cav channels, Cav1 (L-type), Cav2 (P/Q-, N- and R-type) and Cav3 (T-type), Cav3 channels are optimized for regulating cellular excitability because of their fast kinetics and low activation voltages. These same properties permit Cav3 channels to drive low-threshold exocytosis in select neurons and neurosecretory cells. Here, we characterize the single T-type calcium channel from Trichoplax adhaerens (TCav3), an early diverging animal that lacks muscle, neurons, and synapses. Co-immunolocalization using antibodies against TCav3 and neurosecretory cell marker complexin labeled gland cells, which are hypothesized to play roles in paracrine signaling. Cloning and in vitro expression of TCav3 reveals that, despite roughly 600 million years of divergence from other T-type channels, it bears the defining structural and biophysical features of the Cav3 family. We also characterize the channel’s cation permeation properties and find that its pore is less selective for Ca2+ over Na+ compared with the human homologue Cav3.1, yet it exhibits a similar potent block of inward Na+ current by low external Ca2+ concentrations (i.e., the Ca2+ block effect). A comparison of the permeability features of TCav3 with other cloned channels suggests that Ca2+ block is a locus of evolutionary change in T-type channel cation permeation properties and that mammalian channels distinguish themselves from invertebrate ones by bearing both stronger Ca2+ block and higher Ca2+ selectivity. TCav3 is the most divergent metazoan T-type calcium channel and thus provides an evolutionary perspective on Cav3 channel structure–function properties, ion selectivity, and cellular physiology.
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Affiliation(s)
- Carolyn L Smith
- National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Salsabil Abdallah
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Yuen Yan Wong
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Phuong Le
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | | | | | | | | | - Thomas S Reese
- National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Adriano Senatore
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
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5
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Bidaux G, Sgobba M, Lemonnier L, Borowiec AS, Noyer L, Jovanovic S, Zholos AV, Haider S. Functional and Modeling Studies of the Transmembrane Region of the TRPM8 Channel. Biophys J 2016; 109:1840-51. [PMID: 26536261 DOI: 10.1016/j.bpj.2015.09.027] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 09/18/2015] [Accepted: 09/28/2015] [Indexed: 12/15/2022] Open
Abstract
Members of the transient receptor potential (TRP) ion channel family act as polymodal cellular sensors, which aid in regulating Ca(2+) homeostasis. Within the TRP family, TRPM8 is the cold receptor that forms a nonselective homotetrameric cation channel. In the absence of TRPM8 crystal structure, little is known about the relationship between structure and function. Inferences of TRPM8 structure have come from mutagenesis experiments coupled to electrophysiology, mainly regarding the fourth transmembrane helix (S4), which constitutes a moderate voltage-sensing domain, and about cold sensor and phosphatidylinositol 4,5-bisphosphate binding sites, which are both located in the C-terminus of TRPM8. In this study, we use a combination of molecular modeling and experimental techniques to examine the structure of the TRPM8 transmembrane and pore helix region including the conducting conformation of the selectivity filter. The model is consistent with a large amount of functional data and was further tested by mutagenesis. We present structural insight into the role of residues involved in intra- and intersubunit interactions and their link with the channel activity, sensitivity to icilin, menthol and cold, and impact on channel oligomerization.
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Affiliation(s)
- Gabriel Bidaux
- Inserm, U1003, Laboratoire de Physiologie Cellulaire, Equipe labellisée par la Ligue contre le Cancer, Villeneuve d'Ascq, France; Laboratory of Excellence, Ion Channels Science and Therapeutics, Université de Lille 1, Villeneuve d'Ascq, France; Laboratoire Biophotonique Cellulaire Fonctionnelle. Institut de Recherche Interdisciplinaire, Villeneuve d'Ascq, France
| | - Miriam Sgobba
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, United Kingdom
| | - Loic Lemonnier
- Inserm, U1003, Laboratoire de Physiologie Cellulaire, Equipe labellisée par la Ligue contre le Cancer, Villeneuve d'Ascq, France; Laboratory of Excellence, Ion Channels Science and Therapeutics, Université de Lille 1, Villeneuve d'Ascq, France
| | - Anne-Sophie Borowiec
- Inserm, U1003, Laboratoire de Physiologie Cellulaire, Equipe labellisée par la Ligue contre le Cancer, Villeneuve d'Ascq, France; Laboratory of Excellence, Ion Channels Science and Therapeutics, Université de Lille 1, Villeneuve d'Ascq, France
| | - Lucile Noyer
- Inserm, U1003, Laboratoire de Physiologie Cellulaire, Equipe labellisée par la Ligue contre le Cancer, Villeneuve d'Ascq, France; Laboratory of Excellence, Ion Channels Science and Therapeutics, Université de Lille 1, Villeneuve d'Ascq, France
| | | | - Alexander V Zholos
- Department of Biophysics, Educational and Scientific Centre, "Institute of Biology" Taras Shevchenko, Kiev National University, Kiev, Ukraine.
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Saponara S, Durante M, Spiga O, Mugnai P, Sgaragli G, Huong TT, Khanh PN, Son NT, Cuong NM, Fusi F. Functional, electrophysiological and molecular docking analysis of the modulation of Cav 1.2 channels in rat vascular myocytes by murrayafoline A. Br J Pharmacol 2015; 173:292-304. [PMID: 26493241 DOI: 10.1111/bph.13369] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Revised: 10/01/2015] [Accepted: 10/10/2015] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND AND PURPOSE The carbazole alkaloid murrayafoline A (MuA) enhances contractility and the Ca(2+) currents carried by the Cav 1.2 channels [ICa1.2 ] of rat cardiomyocytes. As only few drugs stimulate ICa1.2 , this study was designed to analyse the effects of MuA on vascular Cav 1.2 channels. EXPERIMENTAL APPROACH Vascular activity was assessed on rat aorta rings mounted in organ baths. Cav 1.2 Ba(2+) current [IBa1.2 ] was recorded in single rat aorta and tail artery myocytes by the patch-clamp technique. Docking at a 3D model of the rat, α1c central pore subunit of the Cav 1.2 channel was simulated in silico. KEY RESULTS In rat aorta rings MuA, at concentrations ≤14.2 μM, increased 30 mM K(+) -induced tone and shifted the concentration-response curve to K(+) to the left. Conversely, at concentrations >14.2 μM, it relaxed high K(+) depolarized rings and antagonized Bay K 8644-induced contraction. In single myocytes, MuA stimulated IBa1.2 in a concentration-dependent, bell-shaped manner; stimulation was stable, incompletely reversible upon drug washout and accompanied by a leftward shift of the voltage-dependent activation curve. MuA docked at the α1C subunit central pore differently from nifedipine and Bay K 8644, although apparently interacting with the same amino acids of the pocket. Neither Bay K 8644-induced stimulation nor nifedipine-induced block of IBa1.2 was modified by MuA. CONCLUSIONS AND IMPLICATIONS Murrayafoline A is a naturally occurring vasoactive agent able to modulate Cav 1.2 channels and dock at the α1C subunit central pore in a manner that differed from that of dihydropyridines.
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Affiliation(s)
- S Saponara
- Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy
| | - M Durante
- Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy
| | - O Spiga
- Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Siena, Italy
| | - P Mugnai
- Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy
| | - G Sgaragli
- Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy
| | - T T Huong
- Institute of Natural Products Chemistry, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | - P N Khanh
- Institute of Natural Products Chemistry, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | - N T Son
- Institute of Natural Products Chemistry, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | - N M Cuong
- Institute of Natural Products Chemistry, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | - F Fusi
- Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy
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Senatore A, Guan W, Boone AN, Spafford JD. T-type channels become highly permeable to sodium ions using an alternative extracellular turret region (S5-P) outside the selectivity filter. J Biol Chem 2014; 289:11952-11969. [PMID: 24596098 DOI: 10.1074/jbc.m114.551473] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
T-type (Cav3) channels are categorized as calcium channels, but invertebrate ones can be highly sodium-selective channels. We illustrate that the snail LCav3 T-type channel becomes highly sodium-permeable through exon splicing of an extracellular turret and descending helix in domain II of the four-domain Cav3 channel. Highly sodium-permeable T-type channels are generated without altering the invariant ring of charged residues in the selectivity filter that governs calcium selectivity in calcium channels. The highly sodium-permeant T-type channel expresses in the brain and is the only splice isoform expressed in the snail heart. This unique splicing of turret residues offers T-type channels a capacity to serve as a pacemaking sodium current in the primitive heart and brain in lieu of Nav1-type sodium channels and to substitute for voltage-gated sodium channels lacking in many invertebrates. T-type channels would also contribute substantially to sodium leak conductances at rest in invertebrates because of their large window currents.
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Affiliation(s)
- Adriano Senatore
- Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Wendy Guan
- Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Adrienne N Boone
- Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - J David Spafford
- Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
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Dudev T, Lim C. Evolution of Eukaryotic Ion Channels: Principles Underlying the Conversion of Ca2+-Selective to Na+-Selective Channels. J Am Chem Soc 2014; 136:3553-9. [DOI: 10.1021/ja4121132] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Todor Dudev
- Institute
of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Carmay Lim
- Institute
of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
- Department
of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan
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9
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Senatore A, Guan W, Spafford JD. Cav3 T-type channels: regulators for gating, membrane expression, and cation selectivity. Pflugers Arch 2014; 466:645-60. [PMID: 24515291 DOI: 10.1007/s00424-014-1449-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 01/10/2014] [Accepted: 01/12/2014] [Indexed: 12/13/2022]
Abstract
Cav3 T-type channels are low-voltage-gated channels with rapid kinetics that are classified among the calcium-selective Cav1 and Cav2 type channels. Here, we outline the fundamental and unique regulators of T-type channels. An ubiquitous and proximally located "gating brake" works in concert with the voltage-sensor domain and S6 alpha-helical segment from domain II to set the canonical low-threshold and transient gating features of T-type channels. Gene splicing of optional exon 25c (and/or exon 26) in the short III-IV linker provides a developmental switch between modes of activity, such as activating in response to membrane depolarization, to channels requiring hyperpolarization input before being available to activate. Downstream of the gating brake in the I-II linker is a key region for regulating channel expression where alternative splicing patterns correlate with functional diversity of spike patterns, pacemaking rate (especially in the heart), stage of development, and animal size. A small but persistent window conductance depolarizes cells and boosts excitability at rest. T-type channels possess an ion selectivity that can resemble not only the calcium ion exclusive Cav1 and Cav2 channels but also the sodium ion selectivity of Nav1 sodium channels too. Alternative splicing in the extracellular turret of domain II generates highly sodium-permeable channels, which contribute to low-threshold sodium spikes. Cav3 channels are more ubiquitous among multicellular animals and more widespread in tissues than the more brain centric Nav1 sodium channels in invertebrates. Highly sodium-permeant Cav3 channels can functionally replace Nav1 channels in species where they are lacking, such as in Caenorhabditis elegans.
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Affiliation(s)
- A Senatore
- Department of Biology, University of Waterloo, B1-173, Waterloo, ON, N2L 3G1, Canada
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11
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Tikhonov DB, Zhorov BS. Possible roles of exceptionally conserved residues around the selectivity filters of sodium and calcium channels. J Biol Chem 2010; 286:2998-3006. [PMID: 21081490 DOI: 10.1074/jbc.m110.175406] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
In the absence of x-ray structures of sodium and calcium channels their homology models are used to rationalize experimental data and design new experiments. A challenge is to model the outer-pore region that folds differently from potassium channels. Here we report a new model of the outer-pore region of the NaV1.4 channel, which suggests roles of highly conserved residues around the selectivity filter. The model takes from our previous study (Tikhonov, D. B., and Zhorov, B. S. (2005) Biophys. J. 88, 184-197) the general disposition of the P-helices, selectivity filter residues, and the outer carboxylates, but proposes new intra- and inter-domain contacts that support structural stability of the outer pore. Glycine residues downstream from the selectivity filter are proposed to participate in knob-into-hole contacts with the P-helices and S6s. These contacts explain the adapted tetrodotoxin resistance of snakes that feed on toxic prey through valine substitution of isoleucine in the P-helix of repeat IV. Polar residues five positions upstream from the selectivity filter residues form H-bonds with the ascending-limb backbones. Exceptionally conserved tryptophans are engaged in inter-repeat H-bonds to form a ring whose π-electrons would facilitate passage of ions from the outer carboxylates to the selectivity filter. The outer-pore model of CaV1.2 derived from the NaV1.4 model is also stabilized by the ring of exceptionally conservative tryptophans and H-bonds between the P-helices and ascending limbs. In this model, the exceptionally conserved aspartate downstream from the selectivity-filter glutamate in repeat II facilitates passage of calcium ions to the selectivity-filter ring through the tryptophan ring. Available experimental data are discussed in view of the models.
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Affiliation(s)
- Denis B Tikhonov
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 325, Canada
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