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Estacion M, Liu S, Cheng X, Dib-Hajj S, Waxman SG. Kv7-specific activators hyperpolarize resting membrane potential and modulate human iPSC-derived sensory neuron excitability. Front Pharmacol 2023; 14:1138556. [PMID: 36923357 PMCID: PMC10008904 DOI: 10.3389/fphar.2023.1138556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 02/13/2023] [Indexed: 03/02/2023] Open
Abstract
Chronic pain is highly prevalent and remains a significant unmet global medical need. As part of a search for modulatory genes that confer pain resilience, we have studied two family cohorts where one individual reported much less pain than other family members that share the same pathogenic gain-of-function Nav1.7 mutation that confers hyperexcitability on pain-signaling dorsal root ganglion (DRG) neurons. In each of these kindreds, the pain-resilient individual carried a gain-of-function variant in Kv7.2 or Kv7.3, two potassium channels that stabilize membrane potential and reduce excitability. Our observation in this molecular genetic study that these gain-of-function Kv7.2 and 7.3 variants reduce DRG neuron excitability suggests that agents that activate or open Kv7 channels should attenuate sensory neuron firing. In the present study, we assess the effects on sensory neuron excitability of three Kv7 modulators-retigabine (Kv7.2 thru Kv7.5 activator), ICA-110381 (Kv7.2/Kv7.3 specific activator), and as a comparator ML277 (Kv7.1 specific activator)-in a "human-pain-in-a-dish" model (human iPSC-derived sensory neurons, iPSC-SN). Multi-electrode-array (MEA) recordings demonstrated inhibition of firing with retigabine and ICA-110381 (but not with ML277), with the concentration-response curve indicating that retigabine can achieve a 50% reduction of firing with sub-micromolar concentrations. Current-clamp recording demonstrated that retigabine hyperpolarized iPSC-SN resting potential and increased threshold. This study implicates Kv7.2/Kv7.3 channels as effective modulators of sensory neuron excitability, and suggest that compounds that specifically target Kv7.2/Kv7.3 currents in sensory neurons, including human sensory neurons, might provide an effective approach toward pain relief.
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Affiliation(s)
- Mark Estacion
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Shujun Liu
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Xiaoyang Cheng
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Sulayman Dib-Hajj
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Stephen G. Waxman
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
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Ghovanloo MR, Tyagi S, Zhao P, Kiziltug E, Estacion M, Dib-Hajj SD, Waxman SG. High-throughput combined voltage-clamp/current-clamp analysis of freshly isolated neurons. Cell Rep Methods 2023; 3:100385. [PMID: 36814833 PMCID: PMC9939380 DOI: 10.1016/j.crmeth.2022.100385] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 11/11/2022] [Accepted: 12/15/2022] [Indexed: 01/15/2023]
Abstract
The patch-clamp technique is the gold-standard methodology for analysis of excitable cells. However, throughput of manual patch-clamp is slow, and high-throughput robotic patch-clamp, while helpful for applications like drug screening, has been primarily used to study channels and receptors expressed in heterologous systems. We introduce an approach for automated high-throughput patch-clamping that enhances analysis of excitable cells at the channel and cellular levels. This involves dissociating and isolating neurons from intact tissues and patch-clamping using a robotic instrument, followed by using an open-source Python script for analysis and filtration. As a proof of concept, we apply this approach to investigate the biophysical properties of voltage-gated sodium (Nav) channels in dorsal root ganglion (DRG) neurons, which are among the most diverse and complex neuronal cells. Our approach enables voltage- and current-clamp recordings in the same cell, allowing unbiased, fast, simultaneous, and head-to-head electrophysiological recordings from a wide range of freshly isolated neurons without requiring culturing on coverslips.
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Affiliation(s)
- Mohammad-Reza Ghovanloo
- Department of Neurology, Yale University School of Medicine, New Haven, CT, USA
- Center for Neuroscience & Regeneration Research, Yale University, West Haven, CT, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| | - Sidharth Tyagi
- Department of Neurology, Yale University School of Medicine, New Haven, CT, USA
- Center for Neuroscience & Regeneration Research, Yale University, West Haven, CT, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
- Medical Scientist Training Program, Yale University School of Medicine, New Haven, CT, USA
| | - Peng Zhao
- Department of Neurology, Yale University School of Medicine, New Haven, CT, USA
- Center for Neuroscience & Regeneration Research, Yale University, West Haven, CT, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| | - Emre Kiziltug
- Department of Neurology, Yale University School of Medicine, New Haven, CT, USA
| | - Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, CT, USA
- Center for Neuroscience & Regeneration Research, Yale University, West Haven, CT, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| | - Sulayman D. Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT, USA
- Center for Neuroscience & Regeneration Research, Yale University, West Haven, CT, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
| | - Stephen G. Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, CT, USA
- Center for Neuroscience & Regeneration Research, Yale University, West Haven, CT, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
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Effraim PR, Estacion M, Zhao P, Sosniak D, Waxman SG, Dib-Hajj SD. Fibroblast growth factor homologous factor 2 attenuates excitability of DRG neurons. J Neurophysiol 2022; 128:1258-1266. [PMID: 36222860 PMCID: PMC9909838 DOI: 10.1152/jn.00361.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Fibroblast growth factor homologous factors (FHFs) are cytosolic members of the superfamily of the FGF proteins. Four members of this subfamily (FHF1-4) are differentially expressed in multiple tissues in an isoform-dependent manner. Mutations in FHF proteins have been associated with multiple neurological disorders. FHF proteins bind to the COOH terminus of voltage-gated sodium (Nav) channels and regulate current amplitude and gating properties of these channels. FHF2, which is expressed in dorsal root ganglia (DRG) neurons, has two main splicing isoforms: FHF2A and FHF2B, which differ in the length and sequence of their NH2 termini, have been shown to differentially regulate gating properties of Nav1.7, a channel that is a major driver of DRG neuron firing. FHF2 expression levels are downregulated after peripheral nerve axotomy, which suggests that they may regulate neuronal excitability via an action on Nav channels after injury. We have previously shown that knockdown of FHF2 leads to gain-of-function changes in Nav1.7 gating properties: enhanced repriming, increased current density, and hyperpolarized activation. From this we posited that knockdown of FHF2 might also lead to DRG hyperexcitability. Here we show that knockdown of either FHF2A alone or all isoforms of FHF2 results in increased DRG neuron excitability. In addition, we demonstrate that supplementation of FHF2A and FHF2B reduces DRG neuron excitability. Overexpression of FHF2A or FHF2B also reduced excitability of DRG neurons treated with a cocktail of inflammatory mediators, a model of inflammatory pain. Our data suggest that increased neuronal excitability after nerve injury might be triggered, in part, via a loss of FHF2-Nav1.7 interaction.NEW & NOTEWORTHY FHF2 is known to bind to and modulate the function of Nav1.7. FHF2 expression is also reduced after nerve injury. We demonstrate that knockdown of FHF2 expression increases DRG neuronal excitability. More importantly, overexpression of FHF2 reduces DRG excitability in basal conditions and in the presence of inflammatory mediators (a model of inflammatory pain). These results suggest that FHF2 could potentially be used as a tool to reduce DRG neuronal excitability and to treat pain.
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Affiliation(s)
- Philip R. Effraim
- Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06510
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Peng Zhao
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Daniel Sosniak
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Sulayman D. Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
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Ghovanloo MR, Estacion M, Higerd-Rusli GP, Zhao P, Dib-Hajj S, Waxman SG. Inhibition of sodium conductance by cannabigerol contributes to a reduction of dorsal root ganglion neuron excitability. Br J Pharmacol 2022; 179:4010-4030. [PMID: 35297036 DOI: 10.1111/bph.15833] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 03/02/2022] [Accepted: 03/05/2022] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND AND PURPOSE Cannabigerol (CBG), a non-psychotropic phytocannabinoid and a precursor of ∆9 -tetrahydrocannabinol and cannabidiol, has been suggested to act as an analgesic. A previous study reported that CBG (10 μM) blocks voltage-gated sodium (Nav ) currents in CNS neurons, although the underlying mechanism is not well understood. Genetic and functional studies have validated Nav 1.7 channels as an opportune target for analgesic drug development. The effects of CBG on Nav 1.7 channels, which may contribute to its analgesic properties, have not been previously investigated. EXPERIMENTAL APPROACH To determine the effects of CBG on Nav channels, we used stably transfected HEK cells and primary dorsal root ganglion (DRG) neurons to characterize compound effects using experimental and computational techniques. These included patch-clamp, multielectrode array, and action potential modelling. KEY RESULTS CBG is a ~10-fold state-dependent Nav channel inhibitor (KI -KR : ~2-20 μM) with an average Hill-slope of ~2. We determined that, at lower concentrations, CBG predominantly blocks sodium Gmax and slows recovery from inactivation. However, as the concentration is increased, CBG also induces a hyperpolarizing shift in the half-voltage of inactivation. Our modelling and multielectrode array recordings suggest that CBG attenuates DRG excitability. CONCLUSIONS AND IMPLICATIONS Inhibition of Nav 1.7 channels in DRG neurons may underlie CBG-induced neuronal hypoexcitability. As most Nav 1.7 channels are inactivated at the resting membrane potential of DRG neurons, they are more likely to be inhibited by lower CBG concentrations, suggesting functional selectivity against Nav 1.7 channels, compared with other Nav channels (via Gmax block).
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Affiliation(s)
- Mohammad-Reza Ghovanloo
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA
- Center for Neuroscience and Regeneration Research, Yale University, West Haven, Connecticut, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA
- Center for Neuroscience and Regeneration Research, Yale University, West Haven, Connecticut, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Grant P Higerd-Rusli
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA
- Center for Neuroscience and Regeneration Research, Yale University, West Haven, Connecticut, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Peng Zhao
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA
- Center for Neuroscience and Regeneration Research, Yale University, West Haven, Connecticut, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Sulayman Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA
- Center for Neuroscience and Regeneration Research, Yale University, West Haven, Connecticut, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA
- Center for Neuroscience and Regeneration Research, Yale University, West Haven, Connecticut, USA
- Neuro-Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA
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5
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Higerd-Rusli GP, Alsaloum M, Tyagi S, Sarveswaran N, Estacion M, Akin EJ, Dib-Hajj FB, Liu S, Sosniak D, Zhao P, Dib-Hajj SD, Waxman SG. Depolarizing Na V and Hyperpolarizing K V Channels Are Co-Trafficked in Sensory Neurons. J Neurosci 2022; 42:4794-4811. [PMID: 35589395 PMCID: PMC9188389 DOI: 10.1523/jneurosci.0058-22.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Revised: 05/04/2022] [Accepted: 05/05/2022] [Indexed: 11/21/2022] Open
Abstract
Neuronal excitability relies on coordinated action of functionally distinction channels. Voltage-gated sodium (NaV) and potassium (KV) channels have distinct but complementary roles in firing action potentials: NaV channels provide depolarizing current while KV channels provide hyperpolarizing current. Mutations and dysfunction of multiple NaV and KV channels underlie disorders of excitability, including pain and epilepsy. Modulating ion channel trafficking may offer a potential therapeutic strategy for these diseases. A fundamental question, however, is whether these channels with distinct functional roles are transported independently or packaged together in the same vesicles in sensory axons. We have used Optical Pulse-Chase Axonal Long-distance imaging to investigate trafficking of NaV and KV channels and other axonal proteins from distinct functional classes in live rodent sensory neurons (from male and female rats). We show that, similar to NaV1.7 channels, NaV1.8 and KV7.2 channels are transported in Rab6a-positive vesicles, and that each of the NaV channel isoforms expressed in healthy, mature sensory neurons (NaV1.6, NaV1.7, NaV1.8, and NaV1.9) is cotransported in the same vesicles. Further, we show that multiple axonal membrane proteins with different physiological functions (NaV1.7, KV7.2, and TNFR1) are cotransported in the same vesicles. However, vesicular packaging of axonal membrane proteins is not indiscriminate, since another axonal membrane protein (NCX2) is transported in separate vesicles. These results shed new light on the development and organization of sensory neuron membranes, revealing complex sorting of axonal proteins with diverse physiological functions into specific transport vesicles.SIGNIFICANCE STATEMENT Normal neuronal excitability is dependent on precise regulation of membrane proteins, including NaV and KV channels, and imbalance in the level of these channels at the plasma membrane could lead to excitability disorders. Ion channel trafficking could potentially be targeted therapeutically, which would require better understanding of the mechanisms underlying trafficking of functionally diverse channels. Optical Pulse-chase Axonal Long-distance imaging in live neurons permitted examination of the specificity of ion channel trafficking, revealing co-packaging of axonal proteins with opposing physiological functions into the same transport vesicles. This suggests that additional trafficking mechanisms are necessary to regulate levels of surface channels, and reveals an important consideration for therapeutic strategies that target ion channel trafficking for the treatment of excitability disorders.
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Affiliation(s)
- Grant P Higerd-Rusli
- MD/PhD Program
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Matthew Alsaloum
- MD/PhD Program
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Sidharth Tyagi
- MD/PhD Program
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Nivedita Sarveswaran
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Mark Estacion
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Elizabeth J Akin
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Fadia B Dib-Hajj
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Shujun Liu
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Daniel Sosniak
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Peng Zhao
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Sulayman D Dib-Hajj
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Stephen G Waxman
- Center for Neuroscience and Regeneration Research and
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
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6
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Ghovanloo MR, Estacion M, Zhao P, Dib-Hajj S, Waxman SG. Cannabigerol inhibits sodium conductance to reduce neuronal dorsal root ganglion excitability. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.2240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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7
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Labau JIR, Alsaloum M, Estacion M, Tanaka B, Dib-Hajj FB, Lauria G, Smeets HJM, Faber CG, Dib-Hajj S, Waxman SG. Lacosamide Inhibition of Na V1.7 Channels Depends on its Interaction With the Voltage Sensor Domain and the Channel Pore. Front Pharmacol 2022; 12:791740. [PMID: 34992539 PMCID: PMC8724789 DOI: 10.3389/fphar.2021.791740] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 12/02/2021] [Indexed: 12/14/2022] Open
Abstract
Lacosamide, developed as an anti-epileptic drug, has been used for the treatment of pain. Unlike typical anticonvulsants and local anesthetics which enhance fast-inactivation and bind within the pore of sodium channels, lacosamide enhances slow-inactivation of these channels, suggesting different binding mechanisms and mode of action. It has been reported that lacosamide's effect on NaV1.5 is sensitive to a mutation in the local anesthetic binding site, and that it binds with slow kinetics to the fast-inactivated state of NaV1.7. We recently showed that the NaV1.7-W1538R mutation in the voltage-sensing domain 4 completely abolishes NaV1.7 inhibition by clinically-achievable concentration of lacosamide. Our molecular docking analysis suggests a role for W1538 and pore residues as high affinity binding sites for lacosamide. Aryl sulfonamide sodium channel blockers are also sensitive to substitutions of the W1538 residue but not of pore residues. To elucidate the mechanism by which lacosamide exerts its effects, we used voltage-clamp recordings and show that lacosamide requires an intact local anesthetic binding site to inhibit NaV1.7 channels. Additionally, the W1538R mutation does not abrogate local anesthetic lidocaine-induced blockade. We also show that the naturally occurring arginine in NaV1.3 (NaV1.3-R1560), which corresponds to NaV1.7-W1538R, is not sufficient to explain the resistance of NaV1.3 to clinically-relevant concentrations of lacosamide. However, the NaV1.7-W1538R mutation conferred sensitivity to the NaV1.3-selective aryl-sulfonamide blocker ICA-121431. Together, the W1538 residue and an intact local anesthetic site are required for lacosamide's block of NaV1.7 at a clinically-achievable concentration. Moreover, the contribution of W1538 to lacosamide inhibitory effects appears to be isoform-specific.
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Affiliation(s)
- Julie I R Labau
- Department of Neurology, Yale University School of Medicine, New Haven, CT, United States.,Center for Neuroscience and Regeneration Research, Yale University, West Haven, CT, United States.,Rehabilitation Research Center, Veteran Affairs Connecticut Healthcare System, West Haven, CT, United States.,Department of Toxicogenomics, Clinical Genomics, Maastricht University Medical Centre+, Maastricht, Netherlands.,School of Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands
| | - Matthew Alsaloum
- Department of Neurology, Yale University School of Medicine, New Haven, CT, United States.,Center for Neuroscience and Regeneration Research, Yale University, West Haven, CT, United States.,Rehabilitation Research Center, Veteran Affairs Connecticut Healthcare System, West Haven, CT, United States.,Yale Medical Scientist Training Program, Yale School of Medicine, New Haven, CT, United States.,Interdepartmental Neuroscience Program, Yale School of Medicine, New Haven, CT, United States
| | - Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, CT, United States.,Center for Neuroscience and Regeneration Research, Yale University, West Haven, CT, United States.,Rehabilitation Research Center, Veteran Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Brian Tanaka
- Department of Neurology, Yale University School of Medicine, New Haven, CT, United States.,Center for Neuroscience and Regeneration Research, Yale University, West Haven, CT, United States.,Rehabilitation Research Center, Veteran Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Fadia B Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT, United States.,Center for Neuroscience and Regeneration Research, Yale University, West Haven, CT, United States.,Rehabilitation Research Center, Veteran Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Giuseppe Lauria
- Neuroalgology Unit, IRCCS Foundation, "Carlo Besta" Neurological Institute, Milan, Italy.,Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - Hubert J M Smeets
- Department of Toxicogenomics, Clinical Genomics, Maastricht University Medical Centre+, Maastricht, Netherlands.,School of Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands
| | - Catharina G Faber
- Department of Neurology, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, Netherlands
| | - Sulayman Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT, United States.,Center for Neuroscience and Regeneration Research, Yale University, West Haven, CT, United States.,Rehabilitation Research Center, Veteran Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, CT, United States.,Center for Neuroscience and Regeneration Research, Yale University, West Haven, CT, United States.,Rehabilitation Research Center, Veteran Affairs Connecticut Healthcare System, West Haven, CT, United States
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8
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Yuan JH, Estacion M, Mis MA, Tanaka BS, Schulman BR, Chen L, Liu S, Dib-Hajj FB, Dib-Hajj SD, Waxman SG. KCNQ variants and pain modulation: a missense variant in Kv7.3 contributes to pain resilience. Brain Commun 2021; 3:fcab212. [PMID: 34557669 PMCID: PMC8454204 DOI: 10.1093/braincomms/fcab212] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 07/13/2021] [Accepted: 07/29/2021] [Indexed: 12/02/2022] Open
Abstract
There is a pressing need for understanding of factors that confer resilience to pain. Gain-of-function mutations in sodium channel Nav1.7 produce hyperexcitability of dorsal root ganglion neurons underlying inherited erythromelalgia, a human genetic model of neuropathic pain. While most individuals with erythromelalgia experience excruciating pain, occasional outliers report more moderate pain. These differences in pain profiles in blood-related erythromelalgia subjects carrying the same pain-causative Nav1.7 mutation and markedly different pain experience provide a unique opportunity to investigate potential genetic factors that contribute to inter-individual variability in pain. We studied a patient with inherited erythromelalgia and a Nav1.7 mutation (c.4345T>G, p. F1449V) with severe pain as is characteristic of most inherited erythromelalgia patients, and her mother who carries the same Nav1.7 mutation with a milder pain phenotype. Detailed six-week daily pain diaries of pain episodes confirmed their distinct pain profiles. Electrophysiological studies on subject-specific induced pluripotent stem cell-derived sensory neurons from each of these patients showed that the excitability of these cells paralleled their pain phenotype. Whole-exome sequencing identified a missense variant (c.2263C>T, p. D755N) in KCNQ3 (Kv7.3) in the pain resilient mother. Voltage-clamp recordings showed that co-expression of Kv7.2-wild type (WT)/Kv7.3-D755N channels produced larger M-currents than that of Kv7.2-WT/Kv7.3-WT. The difference in excitability of the patient-specific induced pluripotent stem cell-derived sensory neurons was mimicked by modulating M-current levels using the dynamic clamp and a model of the mutant Kv7.2-WT/Kv7.3-D755N channels. These results show that a 'pain-in-a-dish' model can be used to explicate genetic contributors to pain, and confirm that KCNQ variants can confer pain resilience via an effect on peripheral sensory neurons.
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Affiliation(s)
- Jun-Hui Yuan
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Malgorzata A Mis
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Brian S Tanaka
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Betsy R Schulman
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Lubin Chen
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Shujun Liu
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Fadia B Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06520, USA
- Center for Rehabilitation Research, VA Connecticut Healthcare System, West Haven, CT 06516, USA
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9
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Chen L, Wimalasena NK, Shim J, Han C, Lee SI, Gonzalez-Cano R, Estacion M, Faber CG, Lauria G, Dib-Hajj SD, Woolf CJ, Waxman SG. Two independent mouse lines carrying the Nav1.7 I228M gain-of-function variant display dorsal root ganglion neuron hyperexcitability but a minimal pain phenotype. Pain 2021; 162:1758-1770. [PMID: 33323889 PMCID: PMC8119301 DOI: 10.1097/j.pain.0000000000002171] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 11/23/2020] [Indexed: 01/26/2023]
Abstract
ABSTRACT Small-fiber neuropathy (SFN), characterized by distal unmyelinated or thinly myelinated fiber loss, produces a combination of sensory dysfunction and neuropathic pain. Gain-of-function variants in the sodium channel Nav1.7 that produce dorsal root ganglion (DRG) neuron hyperexcitability are present in 5% to 10% of patients with idiopathic painful SFN. We created 2 independent knock-in mouse lines carrying the Nav1.7 I228M gain-of-function variant, found in idiopathic SFN. Whole-cell patch-clamp and multielectrode array recordings show that Nav1.7 I228M knock-in DRG neurons are hyperexcitable compared with wild-type littermate-control neurons, but despite this, Nav1.7 I228M mice do not display mechanical or thermal hyperalgesia or intraepidermal nerve fiber loss in vivo. Therefore, although these 2 Nav1.7 I228M knock-in mouse lines recapitulate the DRG neuron hyperexcitability associated with gain-of-function mutations in Nav1.7, they do not recapitulate the pain or neuropathy phenotypes seen in patients. We suggest that the relationship between hyperexcitability in sensory neurons and the pain experienced by these patients may be more complex than previously appreciated and highlights the challenges in modelling channelopathy pain disorders in mice.
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Affiliation(s)
- Lubin Chen
- Department of Neurology, Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Neuroscience and Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut
Healthcare System, West Haven, CT 06516, USA
| | - Nivanthika K. Wimalasena
- FM Kirby Neurobiology Center, Boston Children’s
Hospital, Harvard Medical school, Boston, MA 02115, USA
- Department of Neurobiology, Harvard Medical school, Boston,
MA 02115, USA
| | - Jaehoon Shim
- FM Kirby Neurobiology Center, Boston Children’s
Hospital, Harvard Medical school, Boston, MA 02115, USA
- Department of Neurobiology, Harvard Medical school, Boston,
MA 02115, USA
| | - Chongyang Han
- Department of Neurology, Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Neuroscience and Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut
Healthcare System, West Haven, CT 06516, USA
| | - Seong-il Lee
- Department of Neurology, Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Neuroscience and Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut
Healthcare System, West Haven, CT 06516, USA
| | - Rafael Gonzalez-Cano
- FM Kirby Neurobiology Center, Boston Children’s
Hospital, Harvard Medical school, Boston, MA 02115, USA
- Department of Neurobiology, Harvard Medical school, Boston,
MA 02115, USA
| | - Mark Estacion
- Department of Neurology, Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Neuroscience and Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut
Healthcare System, West Haven, CT 06516, USA
| | - Catharina G. Faber
- Department of Neurology, School of Mental Health and
Neuroscience, Maastricht University Medical Center, Maastricht, The
Netherlands
| | - Giuseppe Lauria
- Neuroalgology Unit, IRCCS Foundation, “Carlo
Besta” Neurological Institute, Milan, Italy
- Department of Biomedical and Clinical Sciences
“Luigi Sacco”, University of Milan, Italy
| | - Sulayman D. Dib-Hajj
- Department of Neurology, Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Neuroscience and Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut
Healthcare System, West Haven, CT 06516, USA
| | - Clifford J. Woolf
- FM Kirby Neurobiology Center, Boston Children’s
Hospital, Harvard Medical school, Boston, MA 02115, USA
- Department of Neurobiology, Harvard Medical school, Boston,
MA 02115, USA
| | - Stephen G. Waxman
- Department of Neurology, Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Neuroscience and Regeneration Research, Yale
University School of Medicine, New Haven, CT 06510, USA
- Center for Rehabilitation Research, VA Connecticut
Healthcare System, West Haven, CT 06516, USA
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10
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Labau JIR, Estacion M, Tanaka BS, de Greef BTA, Hoeijmakers JGJ, Geerts M, Gerrits MM, Smeets HJM, Faber CG, Merkies ISJ, Lauria G, Dib-Hajj SD, Waxman SG. Differential effect of lacosamide on Nav1.7 variants from responsive and non-responsive patients with small fibre neuropathy. Brain 2020; 143:771-782. [PMID: 32011655 PMCID: PMC7089662 DOI: 10.1093/brain/awaa016] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 11/13/2019] [Accepted: 12/06/2019] [Indexed: 12/20/2022] Open
Abstract
Small fibre neuropathy is a common pain disorder, which in many cases fails to respond to treatment with existing medications. Gain-of-function mutations of voltage-gated sodium channel Nav1.7 underlie dorsal root ganglion neuronal hyperexcitability and pain in a subset of patients with small fibre neuropathy. Recent clinical studies have demonstrated that lacosamide, which blocks sodium channels in a use-dependent manner, attenuates pain in some patients with Nav1.7 mutations; however, only a subgroup of these patients responded to the drug. Here, we used voltage-clamp recordings to evaluate the effects of lacosamide on five Nav1.7 variants from patients who were responsive or non-responsive to treatment. We show that, at the clinically achievable concentration of 30 μM, lacosamide acts as a potent sodium channel inhibitor of Nav1.7 variants carried by responsive patients, via a hyperpolarizing shift of voltage-dependence of both fast and slow inactivation and enhancement of use-dependent inhibition. By contrast, the effects of lacosamide on slow inactivation and use-dependence in Nav1.7 variants from non-responsive patients were less robust. Importantly, we found that lacosamide selectively enhances fast inactivation only in variants from responders. Taken together, these findings begin to unravel biophysical underpinnings that contribute to responsiveness to lacosamide in patients with small fibre neuropathy carrying select Nav1.7 variants.
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Affiliation(s)
- Julie I R Labau
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA.,Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA.,Department of Neurology, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands.,Department of Genetics and Cell Biology, Clinical Genomics Unit, Maastricht University, Maastricht, The Netherlands
| | - Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA.,Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Brian S Tanaka
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA.,Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Bianca T A de Greef
- Department of Neurology, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands.,Department of Clinical Epidemiology and Medical Technology Assessment (KEMTA), Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Janneke G J Hoeijmakers
- Department of Neurology, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Margot Geerts
- Department of Neurology, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Monique M Gerrits
- Department of Clinical Genetics, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Hubert J M Smeets
- Department of Genetics and Cell Biology, Clinical Genomics Unit, Maastricht University, Maastricht, The Netherlands
| | - Catharina G Faber
- Department of Neurology, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Ingemar S J Merkies
- Department of Neurology, School of Mental Health and Neuroscience, Maastricht University Medical Center, Maastricht, The Netherlands.,Department of Neurology, St. Elisabeth Hospital, Willemstad, Curaçao
| | - Giuseppe Lauria
- Neuroalgology Unit, IRCCS Foundation, "Carlo Besta" Neurological Institute, Milan, Italy.,Department of Biomedical and Clinical Sciences "Luigi Sacco", University of Milan, Italy
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA.,Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA.,Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA
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11
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Alsaloum M, Estacion M, Almomani R, Gerrits MM, Bönhof GJ, Ziegler D, Malik R, Ferdousi M, Lauria G, Merkies IS, Faber CG, Dib-Hajj S, Waxman SG. A gain-of-function sodium channel β2-subunit mutation in painful diabetic neuropathy. Mol Pain 2020; 15:1744806919849802. [PMID: 31041876 PMCID: PMC6510061 DOI: 10.1177/1744806919849802] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Diabetes mellitus is a global challenge with many diverse health sequelae, of which diabetic peripheral neuropathy is one of the most common. A substantial number of patients with diabetic peripheral neuropathy develop chronic pain, but the genetic and epigenetic factors that predispose diabetic peripheral neuropathy patients to develop neuropathic pain are poorly understood. Recent targeted genetic studies have identified mutations in α-subunits of voltage-gated sodium channels (Navs) in patients with painful diabetic peripheral neuropathy. Mutations in proteins that regulate trafficking or functional properties of Navs could expand the spectrum of patients with Nav-related peripheral neuropathies. The auxiliary sodium channel β-subunits (β1–4) have been reported to increase current density, alter inactivation kinetics, and modulate subcellular localization of Nav. Mutations in β-subunits have been associated with several diseases, including epilepsy, cancer, and diseases of the cardiac conducting system. However, mutations in β-subunits have never been shown previously to contribute to neuropathic pain. We report here a patient with painful diabetic peripheral neuropathy and negative genetic screening for mutations in SCN9A, SCN10A, and SCN11A—genes encoding sodium channel α-subunit that have been previously linked to the development of neuropathic pain. Genetic analysis revealed an aspartic acid to asparagine mutation, D109N, in the β2-subunit. Functional analysis using current-clamp revealed that the β2-D109N rendered dorsal root ganglion neurons hyperexcitable, especially in response to repetitive stimulation. Underlying the hyperexcitability induced by the β2-subunit mutation, as evidenced by voltage-clamp analysis, we found a depolarizing shift in the voltage dependence of Nav1.7 fast inactivation and reduced use-dependent inhibition of the Nav1.7 channel.
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Affiliation(s)
- Matthew Alsaloum
- 1 Department of Neurology, Yale University School of Medicine, New Haven, CT, USA.,2 Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT, USA.,3 Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT, USA
| | - Mark Estacion
- 1 Department of Neurology, Yale University School of Medicine, New Haven, CT, USA.,2 Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT, USA
| | - Rowida Almomani
- 4 Department of Clinical Genomics, University Medical Center Maastricht, Maastricht, the Netherlands.,5 Department of Medical Laboratory Sciences, Jordan University of Science and Technology, Irbid, Jordan
| | - Monique M Gerrits
- 4 Department of Clinical Genomics, University Medical Center Maastricht, Maastricht, the Netherlands.,6 Department of Neurology, University Medical Centre Maastricht, Maastricht, the Netherlands
| | - Gidon J Bönhof
- 7 Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany
| | - Dan Ziegler
- 7 Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.,1 8German Center for Diabetes Research, München-Neuherberg, Germany.,9 Division of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
| | - Rayaz Malik
- 10 Weill Cornell Medicine-Qatar, Doha, Qatar.,11 Division of Diabetes, Endocrinology and Gastroenterology, Institute of Human Development, University of Manchester, Manchester, UK
| | - Maryam Ferdousi
- 11 Division of Diabetes, Endocrinology and Gastroenterology, Institute of Human Development, University of Manchester, Manchester, UK
| | - Giuseppe Lauria
- 12 Neuroalgology Unit, IRCCS Foundation "Carlo Besta" Neurological Institute, Milan, Italy.,13 Department of Biomedical and Clinical Sciences "Luigi Sacco," University of Milan, Milan, Italy
| | - Ingemar Sj Merkies
- 6 Department of Neurology, University Medical Centre Maastricht, Maastricht, the Netherlands.,14 Department of Neurology, St. Elisabeth Hospital, Willemstad, Curaçao
| | - Catharina G Faber
- 6 Department of Neurology, University Medical Centre Maastricht, Maastricht, the Netherlands
| | - Sulayman Dib-Hajj
- 1 Department of Neurology, Yale University School of Medicine, New Haven, CT, USA.,2 Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT, USA
| | - Stephen G Waxman
- 1 Department of Neurology, Yale University School of Medicine, New Haven, CT, USA.,2 Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT, USA
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12
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Sizova DV, Huang J, Akin EJ, Estacion M, Gomis-Perez C, Waxman SG, Dib-Hajj SD. A 49-residue sequence motif in the C terminus of Nav1.9 regulates trafficking of the channel to the plasma membrane. J Biol Chem 2020. [DOI: 10.1016/s0021-9258(17)49917-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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13
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Sizova DV, Huang J, Akin EJ, Estacion M, Gomis-Perez C, Waxman SG, Dib-Hajj SD. A 49-residue sequence motif in the C terminus of Nav1.9 regulates trafficking of the channel to the plasma membrane. J Biol Chem 2019; 295:1077-1090. [PMID: 31822564 DOI: 10.1074/jbc.ra119.011424] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 12/06/2019] [Indexed: 12/18/2022] Open
Abstract
Genetic and functional studies have confirmed an important role for the voltage-gated sodium channel Nav1.9 in human pain disorders. However, low functional expression of Nav1.9 in heterologous systems (e.g. in human embryonic kidney 293 (HEK293) cells) has hampered studies of its biophysical and pharmacological properties and the development of high-throughput assays for drug development targeting this channel. The mechanistic basis for the low level of Nav1.9 currents in heterologous expression systems is not understood. Here, we implemented a multidisciplinary approach to investigate the mechanisms that govern functional Nav1.9 expression. Recombinant expression of a series of Nav1.9-Nav1.7 C-terminal chimeras in HEK293 cells identified a 49-amino-acid-long motif in the C terminus of the two channels that regulates expression levels of these chimeras. We confirmed the critical role of this motif in the context of a full-length channel chimera, Nav1.9-Ct49aaNav1.7, which displayed significantly increased current density in HEK293 cells while largely retaining the characteristic Nav1.9-gating properties. High-resolution live microscopy indicated that the newly identified C-terminal motif dramatically increases the number of channels on the plasma membrane of HEK293 cells. Molecular modeling results suggested that this motif is exposed on the cytoplasmic face of the folded C terminus, where it might interact with other channel partners. These findings reveal that a 49-residue-long motif in Nav1.9 regulates channel trafficking to the plasma membrane.
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Affiliation(s)
- Daria V Sizova
- Department of Neurology, Yale University, New Haven, Connecticut 06510.,Center for Neuroscience and Regeneration Research, Yale University, New Haven, Connecticut 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Jianying Huang
- Department of Neurology, Yale University, New Haven, Connecticut 06510.,Center for Neuroscience and Regeneration Research, Yale University, New Haven, Connecticut 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Elizabeth J Akin
- Department of Neurology, Yale University, New Haven, Connecticut 06510.,Center for Neuroscience and Regeneration Research, Yale University, New Haven, Connecticut 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Mark Estacion
- Department of Neurology, Yale University, New Haven, Connecticut 06510.,Center for Neuroscience and Regeneration Research, Yale University, New Haven, Connecticut 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Carolina Gomis-Perez
- Department of Neurology, Yale University, New Haven, Connecticut 06510.,Center for Neuroscience and Regeneration Research, Yale University, New Haven, Connecticut 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Stephen G Waxman
- Department of Neurology, Yale University, New Haven, Connecticut 06510 .,Center for Neuroscience and Regeneration Research, Yale University, New Haven, Connecticut 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University, New Haven, Connecticut 06510 .,Center for Neuroscience and Regeneration Research, Yale University, New Haven, Connecticut 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
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14
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Huang J, Estacion M, Zhao P, Dib-Hajj FB, Schulman B, Abicht A, Kurth I, Brockmann K, Waxman SG, Dib-Hajj SD. A Novel Gain-of-Function Nav1.9 Mutation in a Child With Episodic Pain. Front Neurosci 2019; 13:918. [PMID: 31551682 PMCID: PMC6733892 DOI: 10.3389/fnins.2019.00918] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 08/16/2019] [Indexed: 12/22/2022] Open
Abstract
Voltage-gated sodium channel Nav1.9 is a threshold channel that regulates action potential firing. Nav1.9 is preferentially expressed in myenteric neurons, and small-diameter dorsal root ganglion (DRG) and trigeminal ganglion neurons including nociceptors. Recent studies have demonstrated a monogenic Mendelian link of Nav1.9 to human pain disorders. Gain-of-function variants in Nav1.9, which cause smaller depolarizations of RMP, have been identified in patients with familial episodic pain type 3 (FEPS3) and the more common pain disorder small fiber neuropathy. To explore the phenotypic spectrum of Nav1.9 channelopathy, here we report a new Nav1.9 mutation, N816K, in a child with early-onset episodic pain in both legs, episodic abdominal pain, and chronic constipation. Sequencing of further selected pain genes was normal. N816K alters a residue at the N-terminus of loop 2, proximal to the cytoplasmic terminus of transmembrane segment 6 in domain II. Voltage-clamp recordings demonstrate that Nav1.9-N816K significantly increases current density and hyperpolarizes voltage-dependence of activation by 10 mV, enabling a larger window current. Current-clamp recordings in DRG neurons shows that N816K channels depolarize RMP of small DRG neurons by 7 mV, reduce current threshold of firing an action potential and render DRG neurons hyperexcitable. Taken together these data demonstrate gain-of-function attributes of the newly described N816K mutation at the channel and cellular levels, which are consistent with a pain phenotype in the carrier of this mutation.
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Affiliation(s)
- Jianying Huang
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Mark Estacion
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Peng Zhao
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Fadia B Dib-Hajj
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Betsy Schulman
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Angela Abicht
- Medizinisch Genetisches Zentrum, Munich, Germany.,Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University of Munich, Munich, Germany
| | - Ingo Kurth
- Medical Faculty, Institute of Human Genetics, RWTH Aachen University, Aachen, Germany
| | - Knut Brockmann
- Department of Pediatrics and Pediatric Neurology, Georg August University, Göttingen, Germany
| | - Stephen G Waxman
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Sulayman D Dib-Hajj
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, United States.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
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15
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Adi T, Estacion M, Schulman BR, Vernino S, Dib-Hajj SD, Waxman SG. A novel gain-of-function Na v1.7 mutation in a carbamazepine-responsive patient with adult-onset painful peripheral neuropathy. Mol Pain 2018; 14:1744806918815007. [PMID: 30392441 PMCID: PMC6856981 DOI: 10.1177/1744806918815007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Voltage-gated sodium channel Nav1.7 is a threshold channel in
peripheral dorsal root ganglion (DRG), trigeminal ganglion, and sympathetic
ganglion neurons. Gain-of-function mutations in Nav1.7 have been
shown to increase excitability in DRG neurons and have been linked to rare
Mendelian and more common pain disorders. Discovery of Nav1.7
variants in patients with pain disorders may expand the spectrum of painful
peripheral neuropathies associated with a well-defined molecular target, thereby
providing a basis for more targeted approaches for treatment. We screened the
genome of a patient with adult-onset painful peripheral neuropathy characterized
by severe burning pain and report here the new Nav1.7-V810M variant.
Voltage-clamp recordings were used to assess the effects of the mutation on
biophysical properties of Nav1.7 and the response of the mutant
channel to treatment with carbamazepine (CBZ), and multi-electrode array (MEA)
recordings were used to assess the effects of the mutation on the excitability
of neonatal rat pup DRG neurons. The V810M variant increases current density,
shifts activation in a hyperpolarizing direction, and slows kinetics of
deactivation, all gain-of-function attributes. We also show that DRG neurons
that express the V810M variant become hyperexcitable. The patient responded to
treatment with CBZ. Although CBZ did not depolarize activation of the mutant
channel, it enhanced use-dependent inhibition. Our results demonstrate the
presence of a novel gain-of-function variant of Nav1.7 in a patient
with adult-onset painful peripheral neuropathy and the responsiveness of that
patient to treatment with CBZ, which is likely due to the classical mechanism of
use-dependent inhibition.
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Affiliation(s)
- Talia Adi
- 1 Department of Neurology, Yale University School of Medicine, New Haven, CT, USA.,2 Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT, USA
| | - Mark Estacion
- 1 Department of Neurology, Yale University School of Medicine, New Haven, CT, USA.,2 Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT, USA
| | - Betsy R Schulman
- 1 Department of Neurology, Yale University School of Medicine, New Haven, CT, USA.,2 Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT, USA
| | - Steven Vernino
- 3 Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, TX, USA
| | - Sulayman D Dib-Hajj
- 1 Department of Neurology, Yale University School of Medicine, New Haven, CT, USA.,2 Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT, USA
| | - Stephen G Waxman
- 1 Department of Neurology, Yale University School of Medicine, New Haven, CT, USA.,2 Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT, USA
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16
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Han C, Themistocleous AC, Estacion M, Dib-Hajj FB, Blesneac I, Macala L, Fratter C, Bennett DL, Waxman SG, Dib-Hajj SD. The Novel Activity of Carbamazepine as an Activation Modulator Extends from Na V1.7 Mutations to the Na V1.8-S242T Mutant Channel from a Patient with Painful Diabetic Neuropathy. Mol Pharmacol 2018; 94:1256-1269. [PMID: 30135145 DOI: 10.1124/mol.118.113076] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 08/20/2018] [Indexed: 01/24/2023] Open
Abstract
Neuropathic pain in patients carrying sodium channel gain-of-function mutations is generally refractory to pharmacotherapy. However, we have shown that pretreatment of cells with clinically achievable concentration of carbamazepine (CBZ; 30 μM) depolarizes the voltage dependence of activation in some NaV1.7 mutations such as S241T, a novel CBZ mode of action of this drug. CBZ reduces the excitability of dorsal root ganglion (DRG) neurons expressing NaV1.7-S241T mutant channels, and individuals carrying the S241T mutation respond to treatment with CBZ. Whether the novel activation-modulating activity of CBZ is specific to NaV1.7, and whether this pharmacogenomic approach can be extended to other sodium channel subtypes, are not known. We report here the novel NaV1.8-S242T mutation, which corresponds to the NaV1.7-S241T mutation, in a patient with neuropathic pain and diabetic peripheral neuropathy. Voltage-clamp recordings demonstrated hyperpolarized and accelerated activation of NaV1.8-S242T. Current-clamp recordings showed that NaV1.8-S242T channels render DRG neurons hyperexcitable. Structural modeling shows that despite a substantial difference in the primary amino acid sequence of NaV1.7 and NaV1.8, the S242 (NaV1.8) and S241 (NaV1.7) residues have similar position and orientation in the domain I S4-S5 linker of the channel. Pretreatment with a clinically achievable concentration of CBZ corrected the voltage dependence of activation of NaV1.8-S242T channels and reduced DRG neuron excitability as predicted from our pharmacogenomic model. These findings extend the novel activation modulation mode of action of CBZ to a second sodium channel subtype, NaV1.8.
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Affiliation(s)
- Chongyang Han
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Center for restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom (A.C.T., I.B., D.L.B.); Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.C.T.); and Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom (C.F.)
| | - Andreas C Themistocleous
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Center for restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom (A.C.T., I.B., D.L.B.); Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.C.T.); and Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom (C.F.)
| | - Mark Estacion
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Center for restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom (A.C.T., I.B., D.L.B.); Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.C.T.); and Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom (C.F.)
| | - Fadia B Dib-Hajj
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Center for restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom (A.C.T., I.B., D.L.B.); Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.C.T.); and Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom (C.F.)
| | - Iulia Blesneac
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Center for restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom (A.C.T., I.B., D.L.B.); Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.C.T.); and Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom (C.F.)
| | - Lawrence Macala
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Center for restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom (A.C.T., I.B., D.L.B.); Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.C.T.); and Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom (C.F.)
| | - Carl Fratter
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Center for restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom (A.C.T., I.B., D.L.B.); Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.C.T.); and Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom (C.F.)
| | - David L Bennett
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Center for restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom (A.C.T., I.B., D.L.B.); Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.C.T.); and Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom (C.F.)
| | - Stephen G Waxman
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Center for restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom (A.C.T., I.B., D.L.B.); Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.C.T.); and Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom (C.F.)
| | - Sulayman D Dib-Hajj
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Center for restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut (C.H., M.E., F.B.D.-H., L.M., S.G.W., S.D.D.-H.); Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom (A.C.T., I.B., D.L.B.); Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.C.T.); and Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom (C.F.)
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17
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Huang J, Mis MA, Tanaka B, Adi T, Estacion M, Liu S, Walker S, Dib-Hajj SD, Waxman SG. Atypical changes in DRG neuron excitability and complex pain phenotype associated with a Na v1.7 mutation that massively hyperpolarizes activation. Sci Rep 2018; 8:1811. [PMID: 29379075 PMCID: PMC5788866 DOI: 10.1038/s41598-018-20221-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 01/16/2018] [Indexed: 02/06/2023] Open
Abstract
Sodium channel Nav1.7 plays a central role in pain-signaling: gain-of-function Nav1.7 mutations usually cause severe pain and loss-of-function mutations produce insensitivity to pain. The Nav1.7 I234T gain-of-function mutation, however, is linked to a dual clinical presentation of episodic pain, together with absence of pain following fractures, and corneal anesthesia. How a Nav1.7 mutation that produces gain-of-function at the channel level causes clinical loss-of-function has remained enigmatic. We show by current-clamp that expression of I234T in dorsal root ganglion (DRG) neurons produces a range of membrane depolarizations including a massive shift to >−40 mV that reduces excitability in a small number of neurons. Dynamic-clamp permitted us to mimic the heterozygous condition via replacement of 50% endogenous wild-type Nav1.7 channels by I234T, and confirmed that the I234T conductance could drastically depolarize DRG neurons, resulting in loss of excitability. We conclude that attenuation of pain sensation by I234T is caused by massively depolarized membrane potential of some DRG neurons which is partly due to enhanced overlap between activation and fast-inactivation, impairing their ability to fire. Our results demonstrate how a Nav1.7 mutation that produces channel gain-of-function can contribute to a dual clinical presentation that includes loss of pain sensation at the clinical level.
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Affiliation(s)
- Jianying Huang
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA, 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA, 06516
| | - Malgorzata A Mis
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA, 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA, 06516
| | - Brian Tanaka
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA, 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA, 06516
| | - Talia Adi
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA, 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA, 06516
| | - Mark Estacion
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA, 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA, 06516
| | - Shujun Liu
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA, 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA, 06516
| | - Suellen Walker
- Developmental Neurosciences Program, Department of Anaesthesia and Pain Medicine, UCL Great Ormond Street Hospital, London, WC1N 1EH, UK
| | - Sulayman D Dib-Hajj
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA, 06510.,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA, 06516
| | - Stephen G Waxman
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT, USA, 06510. .,Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA, 06516.
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18
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Geha P, Yang Y, Estacion M, Schulman BR, Tokuno H, Apkarian AV, Dib-Hajj SD, Waxman SG. Pharmacotherapy for Pain in a Family With Inherited Erythromelalgia Guided by Genomic Analysis and Functional Profiling. JAMA Neurol 2017; 73:659-67. [PMID: 27088781 DOI: 10.1001/jamaneurol.2016.0389] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
IMPORTANCE There is a need for more effective pharmacotherapy for chronic pain, including pain in inherited erythromelalgia (IEM) in which gain-of-function mutations of sodium channel NaV1.7 make dorsal root ganglion (DRG) neurons hyperexcitable. OBJECTIVE To determine whether pain in IEM can be attenuated via pharmacotherapy guided by genomic analysis and functional profiling. DESIGN, SETTING, AND PARTICIPANTS Pain in 2 patients with IEM due to the NaV1.7 S241T mutation, predicted by structural modeling and functional analysis to be responsive to carbamazepine, was assessed in a double-blind, placebo-controlled study conducted from September 2014 to April 21, 2015. Functional magnetic resonance imaging assessed patterns of brain activity associated with pain during treatment with placebo or carbamazepine. Multielectrode array technology was used to assess the effect of carbamazepine on firing of DRG neurons carrying S241T mutant channels. MAIN OUTCOMES AND MEASURES Behavioral assessment of pain; functional magnetic resonance imaging; and assessment of firing in DRG neurons carrying S241T mutant channels. RESULTS This study included 2 patients from the same family with IEM and the S241T NaV1.7 mutation. We showed that, as predicted by molecular modeling, thermodynamic analysis, and functional profiling, carbamazepine attenuated pain in patients with IEM due to the S241T NaV1.7 mutation. Patient 1 reported a reduction in mean time in pain (TIP) per day during the 15-day maintenance period, from 424 minutes while taking placebo to 231.9 minutes while taking carbamazepine (400 mg/day), and a reduction in total TIP over the 15-day maintenance period, from 6360 minutes while taking placebo to 3015 minutes while taking carbamazepine. Patient 2 reported a reduction in mean TIP per day during the maintenance period, from 61 minutes while taking placebo to 9.1 minutes while taking carbamazepine (400 mg then 200 mg/day), and a reduction in total TIP, from 915 minutes while taking placebo over the 15-day maintenance period to 136 minutes while taking carbamazepine. Patient 1 reported a reduction of mean episode duration, from 615 minutes while taking placebo to 274.1 minutes while taking carbamazepine, while patient 2 reported a reduction of the mean episode duration from 91.5 minutes while taking placebo to 45.3 minutes while taking carbamazepine. Patient 1, who had a history of night awakenings from pain, reported 101 awakenings owing to pain while taking placebo during the maintenance period and 32 awakenings while taking carbamazepine. Attenuation of pain was paralleled by a shift in brain activity from valuation and pain areas to primary and secondary somatosensory, motor, and parietal attention areas. Firing of DRG neurons expressing the S241T NaV1.7 mutant channel in response to physiologically relevant thermal stimuli was reduced by carbamazepine. CONCLUSIONS AND RELEVANCE Our results demonstrate that pharmacotherapy guided by genomic analysis, molecular modeling, and functional profiling can attenuate neuropathic pain in patients carrying the S241T mutation.
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Affiliation(s)
- Paul Geha
- Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut2The John B. Pierce Laboratory, New Haven, Connecticut
| | - Yang Yang
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut4Neurorehabilitation Research Center, Department of Neurology, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut4Neurorehabilitation Research Center, Department of Neurology, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Betsy R Schulman
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut4Neurorehabilitation Research Center, Department of Neurology, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Hajime Tokuno
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut4Neurorehabilitation Research Center, Department of Neurology, Veterans Affairs Medical Center, West Haven, Connecticut
| | - A Vania Apkarian
- Department of Physiology, Northwestern University, Chicago, Illinois
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut4Neurorehabilitation Research Center, Department of Neurology, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut4Neurorehabilitation Research Center, Department of Neurology, Veterans Affairs Medical Center, West Haven, Connecticut
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19
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Estacion M, Waxman SG. Nonlinear effects of hyperpolarizing shifts in activation of mutant Na v1.7 channels on resting membrane potential. J Neurophysiol 2017; 117:1702-1712. [PMID: 28148645 DOI: 10.1152/jn.00898.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 01/11/2017] [Accepted: 01/26/2017] [Indexed: 01/16/2023] Open
Abstract
The Nav1.7 sodium channel is preferentially expressed within dorsal root ganglion (DRG) and sympathetic ganglion neurons. Gain-of-function mutations that cause the painful disorder inherited erythromelalgia (IEM) shift channel activation in a hyperpolarizing direction. When expressed within DRG neurons, these mutations produce a depolarization of resting membrane potential (RMP). The biophysical basis for the depolarized RMP has to date not been established. To explore the effect on RMP of the shift in activation associated with a prototypical IEM mutation (L858H), we used dynamic-clamp models that represent graded shifts that fractionate the effect of the mutation on activation voltage dependence. Dynamic-clamp recording from DRG neurons using a before-and-after protocol for each cell made it possible, even in the presence of cell-to-cell variation in starting RMP, to assess the effects of these graded mutant models. Our results demonstrate a nonlinear, progressively larger effect on RMP as the shift in activation voltage dependence becomes more hyperpolarized. The observed differences in RMP were predicted by the "late" current of each mutant model. Since the depolarization of RMP imposed by IEM mutant channels is known, in itself, to produce hyperexcitability of DRG neurons, the development of pharmacological agents that normalize or partially normalize activation voltage dependence of IEM mutant channels merits further study.NEW & NOTEWORTHY Inherited erythromelalgia (IEM), the first human pain disorder linked to a sodium channel, is widely regarded as a genetic model of neuropathic pain. IEM is produced by Nav1.7 mutations that hyperpolarize activation. These mutations produce a depolarization of resting membrane potential (RMP) in dorsal root ganglion neurons. Using dynamic clamp to explore the effect on RMP of the shift in activation, we demonstrate a nonlinear effect on RMP as the shift in activation voltage dependence becomes more hyperpolarized.
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Affiliation(s)
- Mark Estacion
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and.,Rehabilitation Research Center, Department of Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Stephen G Waxman
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and .,Rehabilitation Research Center, Department of Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
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20
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Alexandrou AJ, Brown AR, Chapman ML, Estacion M, Turner J, Mis MA, Wilbrey A, Payne EC, Gutteridge A, Cox PJ, Doyle R, Printzenhoff D, Lin Z, Marron BE, West C, Swain NA, Storer RI, Stupple PA, Castle NA, Hounshell JA, Rivara M, Randall A, Dib-Hajj SD, Krafte D, Waxman SG, Patel MK, Butt RP, Stevens EB. Subtype-Selective Small Molecule Inhibitors Reveal a Fundamental Role for Nav1.7 in Nociceptor Electrogenesis, Axonal Conduction and Presynaptic Release. PLoS One 2016; 11:e0152405. [PMID: 27050761 PMCID: PMC4822888 DOI: 10.1371/journal.pone.0152405] [Citation(s) in RCA: 131] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 03/14/2016] [Indexed: 01/08/2023] Open
Abstract
Human genetic studies show that the voltage gated sodium channel 1.7 (Nav1.7) is a key molecular determinant of pain sensation. However, defining the Nav1.7 contribution to nociceptive signalling has been hampered by a lack of selective inhibitors. Here we report two potent and selective arylsulfonamide Nav1.7 inhibitors; PF-05198007 and PF-05089771, which we have used to directly interrogate Nav1.7’s role in nociceptor physiology. We report that Nav1.7 is the predominant functional TTX-sensitive Nav in mouse and human nociceptors and contributes to the initiation and the upstroke phase of the nociceptor action potential. Moreover, we confirm a role for Nav1.7 in influencing synaptic transmission in the dorsal horn of the spinal cord as well as peripheral neuropeptide release in the skin. These findings demonstrate multiple contributions of Nav1.7 to nociceptor signalling and shed new light on the relative functional contribution of this channel to peripheral and central noxious signal transmission.
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Affiliation(s)
- Aristos J. Alexandrou
- Pfizer Neusentis, The Portway Buiding, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - Adam R. Brown
- Pfizer Neusentis, The Portway Buiding, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - Mark L. Chapman
- Pfizer Neusentis, 4222 Emperor Boulevard, Durham, North Carolina, 27703, United States of America
| | - Mark Estacion
- Center for Neuroscience & Regeneration Research, Yale Medical School and Veterans Affairs Hospital, West Haven, CT, 06516, United States of America
| | - Jamie Turner
- Pfizer Neusentis, The Portway Buiding, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - Malgorzata A. Mis
- Pfizer Neusentis, The Portway Buiding, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - Anna Wilbrey
- Pfizer Neusentis, The Portway Buiding, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - Elizabeth C. Payne
- Pfizer Neusentis, The Portway Buiding, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - Alex Gutteridge
- Pfizer Neusentis, The Portway Buiding, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - Peter J. Cox
- Pfizer Neusentis, The Portway Buiding, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - Rachel Doyle
- Pfizer Global R&D, Ramsgate Road, Sandwich, Kent, CT13 9NJ, United Kingdom
| | - David Printzenhoff
- Pfizer Neusentis, 4222 Emperor Boulevard, Durham, North Carolina, 27703, United States of America
| | - Zhixin Lin
- Pfizer Neusentis, 4222 Emperor Boulevard, Durham, North Carolina, 27703, United States of America
| | - Brian E. Marron
- Pfizer Neusentis, 4222 Emperor Boulevard, Durham, North Carolina, 27703, United States of America
| | - Christopher West
- Pfizer Neusentis, 4222 Emperor Boulevard, Durham, North Carolina, 27703, United States of America
| | - Nigel A. Swain
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - R. Ian Storer
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - Paul A. Stupple
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
| | - Neil A. Castle
- Pfizer Neusentis, 4222 Emperor Boulevard, Durham, North Carolina, 27703, United States of America
| | - James A. Hounshell
- Dept. Anesthesiology, University of Virginia Health System, Charlottesville, Virginia, 22911, United States of America
| | - Mirko Rivara
- Dept. Anesthesiology, University of Virginia Health System, Charlottesville, Virginia, 22911, United States of America
| | - Andrew Randall
- Medical School, Hatherly Building, University of Exeter, Prince of Wales Road, Exeter, EX4 4PS, United Kingdom
| | - Sulayman D. Dib-Hajj
- Center for Neuroscience & Regeneration Research, Yale Medical School and Veterans Affairs Hospital, West Haven, CT, 06516, United States of America
| | - Douglas Krafte
- Pfizer Neusentis, 4222 Emperor Boulevard, Durham, North Carolina, 27703, United States of America
| | - Stephen G. Waxman
- Center for Neuroscience & Regeneration Research, Yale Medical School and Veterans Affairs Hospital, West Haven, CT, 06516, United States of America
| | - Manoj K. Patel
- Dept. Anesthesiology, University of Virginia Health System, Charlottesville, Virginia, 22911, United States of America
| | - Richard P. Butt
- Pfizer Neusentis, The Portway Buiding, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
- * E-mail: (EBS); (RPB)
| | - Edward B. Stevens
- Pfizer Neusentis, The Portway Buiding, Granta Park, Great Abington, Cambridge, CB21 6GS, United Kingdom
- * E-mail: (EBS); (RPB)
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21
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Estacion M, Vohra BPS, Liu S, Hoeijmakers J, Faber CG, Merkies ISJ, Lauria G, Black JA, Waxman SG. Ca2+ toxicity due to reverse Na+/Ca2+ exchange contributes to degeneration of neurites of DRG neurons induced by a neuropathy-associated Nav1.7 mutation. J Neurophysiol 2015; 114:1554-64. [PMID: 26156380 DOI: 10.1152/jn.00195.2015] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 07/06/2015] [Indexed: 12/19/2022] Open
Abstract
Gain-of-function missense mutations in voltage-gated sodium channel Nav1.7 have been linked to small-fiber neuropathy, which is characterized by burning pain, dysautonomia and a loss of intraepidermal nerve fibers. However, the mechanistic cascades linking Nav1.7 mutations to axonal degeneration are incompletely understood. The G856D mutation in Nav1.7 produces robust changes in channel biophysical properties, including hyperpolarized activation, depolarized inactivation, and enhanced ramp and persistent currents, which contribute to the hyperexcitability exhibited by neurons containing Nav1.8. We report here that cell bodies and neurites of dorsal root ganglion (DRG) neurons transfected with G856D display increased levels of intracellular Na(+) concentration ([Na(+)]) and intracellular [Ca(2+)] following stimulation with high [K(+)] compared with wild-type (WT) Nav1.7-expressing neurons. Blockade of reverse mode of the sodium/calcium exchanger (NCX) or of sodium channels attenuates [Ca(2+)] transients evoked by high [K(+)] in G856D-expressing DRG cell bodies and neurites. We also show that treatment of WT or G856D-expressing neurites with high [K(+)] or 2-deoxyglucose (2-DG) does not elicit degeneration of these neurites, but that high [K(+)] and 2-DG in combination evokes degeneration of G856D neurites but not WT neurites. Our results also demonstrate that 0 Ca(2+) or blockade of reverse mode of NCX protects G856D-expressing neurites from degeneration when exposed to high [K(+)] and 2-DG. These results point to [Na(+)] overload in DRG neurons expressing mutant G856D Nav1.7, which triggers reverse mode of NCX and contributes to Ca(2+) toxicity, and suggest subtype-specific blockade of Nav1.7 or inhibition of reverse NCX as strategies that might slow or prevent axon degeneration in small-fiber neuropathy.
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Affiliation(s)
- M Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; Center for Neuroscience and Regeneration Research, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - B P S Vohra
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; Center for Neuroscience and Regeneration Research, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - S Liu
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; Center for Neuroscience and Regeneration Research, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - J Hoeijmakers
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
| | - C G Faber
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
| | - I S J Merkies
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands; Department of Neurology, Spaarne Hospital, Hoofddorp, the Netherlands; and
| | - G Lauria
- Neuroalgology Unit IRCCS Foundation "Carlo Besta" Neurological Institute, Milan, Italy
| | - J A Black
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; Center for Neuroscience and Regeneration Research, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - S G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; Center for Neuroscience and Regeneration Research, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut;
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Han C, Estacion M, Huang J, Vasylyev D, Zhao P, Dib-Hajj SD, Waxman SG. Human Na(v)1.8: enhanced persistent and ramp currents contribute to distinct firing properties of human DRG neurons. J Neurophysiol 2015; 113:3172-85. [PMID: 25787950 DOI: 10.1152/jn.00113.2015] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 03/13/2015] [Indexed: 12/19/2022] Open
Abstract
Although species-specific differences in ion channel properties are well-documented, little has been known about the properties of the human Nav1.8 channel, an important contributor to pain signaling. Here we show, using techniques that include voltage clamp, current clamp, and dynamic clamp in dorsal root ganglion (DRG) neurons, that human Na(v)1.8 channels display slower inactivation kinetics and produce larger persistent current and ramp current than previously reported in other species. DRG neurons expressing human Na(v)1.8 channels unexpectedly produce significantly longer-lasting action potentials, including action potentials with half-widths in some cells >10 ms, and increased firing frequency compared with the narrower and usually single action potentials generated by DRG neurons expressing rat Na(v)1.8 channels. We also show that native human DRG neurons recapitulate these properties of Na(v)1.8 current and the long-lasting action potentials. Together, our results demonstrate strikingly distinct properties of human Na(v)1.8, which contribute to the firing properties of human DRG neurons.
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Affiliation(s)
- Chongyang Han
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Jianying Huang
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Dymtro Vasylyev
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Peng Zhao
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut; and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, Connecticut
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de Kovel CGF, Meisler MH, Brilstra EH, van Berkestijn FMC, van 't Slot R, van Lieshout S, Nijman IJ, O'Brien JE, Hammer MF, Estacion M, Waxman SG, Dib-Hajj SD, Koeleman BPC. Characterization of a de novo SCN8A mutation in a patient with epileptic encephalopathy. Epilepsy Res 2014; 108:1511-8. [PMID: 25239001 DOI: 10.1016/j.eplepsyres.2014.08.020] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 05/19/2014] [Accepted: 08/26/2014] [Indexed: 10/24/2022]
Abstract
OBJECTIVE Recently, de novo SCN8A missense mutations have been identified as a rare dominant cause of epileptic encephalopathies (EIEE13). Functional studies on the first described case demonstrated gain-of-function effects of the mutation. We describe a novel de novo mutation of SCN8A in a patient with epileptic encephalopathy, and functional characterization of the mutant protein. DESIGN Whole exome sequencing was used to discover the variant. We generated a mutant cDNA, transfected HEK293 cells, and performed Western blotting to assess protein stability. To study channel functional properties, patch-clamp experiments were carried out in transfected neuronal ND7/23 cells. RESULTS The proband exhibited seizure onset at 6 months of age, diffuse brain atrophy, and more profound developmental impairment than the original case. The mutation p.Arg233Gly in the voltage sensing transmembrane segment D1S4 was present in the proband and absent in both parents. This mutation results in a temperature-sensitive reduction in protein expression as well as reduced sodium current amplitude and density and a relative increased response to a slow ramp stimulus, though this did not result in an absolute increased current at physiological temperatures. CONCLUSION The new de novo SCN8A mutation is clearly deleterious, resulting in an unstable protein with reduced channel activity. This differs from the gain-of-function attributes of the first SCN8A mutation in epileptic encephalopathy, pointing to heterogeneity of mechanisms. Since Nav1.6 is expressed in both excitatory and inhibitory neurons, a differential effect of a loss-of-function of Nav1.6 Arg223Gly on inhibitory interneurons may underlie the epilepsy phenotype in this patient.
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Affiliation(s)
- Carolien G F de Kovel
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands.
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA; Department of Neurology, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | - Eva H Brilstra
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Ruben van 't Slot
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Stef van Lieshout
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Isaac J Nijman
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Janelle E O'Brien
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | - Michael F Hammer
- Arizona Research Laboratories, Division of Biotechnology, University of Arizona, Tucson, AZ 85721, USA
| | - Mark Estacion
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA; Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Stephen G Waxman
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA; Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Sulayman D Dib-Hajj
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA; Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Bobby P C Koeleman
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
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Persson AK, Estacion M, Ahn H, Liu S, Stamboulian-Platel S, Waxman SG, Black JA. Contribution of sodium channels to lamellipodial protrusion and Rac1 and ERK1/2 activation in ATP-stimulated microglia. Glia 2014; 62:2080-95. [PMID: 25043721 DOI: 10.1002/glia.22728] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 06/11/2014] [Accepted: 07/08/2014] [Indexed: 12/19/2022]
Abstract
Microglia are motile resident immune cells of the central nervous system (CNS) that continuously explore their territories for threats to tissue homeostasis. Following CNS insult (e.g., cellular injury, infection, or ischemia), microglia respond to signals such as ATP, transform into an activated state, and migrate towards the threat. Directed migration is a complex and highly-coordinated process involving multiple intersecting cellular pathways, including signal transduction, membrane adhesion and retraction, cellular polarization, and rearrangement of cytoskeletal elements. We previously demonstrated that the activity of sodium channels contributes to ATP-induced migration of microglia. Here we show that TTX-sensitive sodium channels, specifically NaV 1.6, participate in an initial event in the migratory process, i.e., the formation in ATP-stimulated microglia of polymerized actin-rich membrane protrusions, lamellipodia, containing accumulations of Rac1 and phosphorylated ERK1/2. We also examined Ca(2+) transients in microglia and found that blockade of sodium channels with TTX produced a downward shift in the level of [Ca(2+) ]i during the delayed, slower recovery of [Ca(2+) ]i following ATP stimulation. These observations demonstrate a modulatory role of sodium channels on Ca(2+) transients in microglia that are likely to affect down-stream signaling cascades. Consistent with these observations, we demonstrate that ATP-induced microglial migration is mediated via Rac1 and ERK1/2, but not p38α/β and JNK, dependent pathways, and that activation of both Rac1 and ERK1/2 is modulated by sodium channel activity. Our results provide evidence for a direct link between sodium channel activity and modulation of Rac1 and ERK1/2 activation in ATP-stimulated microglia, possibly by regulating Ca(2+) transients.
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Affiliation(s)
- Anna-Karin Persson
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, Connecticut
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Estacion M, O'Brien JE, Conravey A, Hammer MF, Waxman SG, Dib-Hajj SD, Meisler MH. A novel de novo mutation of SCN8A (Nav1.6) with enhanced channel activation in a child with epileptic encephalopathy. Neurobiol Dis 2014; 69:117-23. [PMID: 24874546 DOI: 10.1016/j.nbd.2014.05.017] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 04/21/2014] [Accepted: 05/17/2014] [Indexed: 10/25/2022] Open
Abstract
Rare de novo mutations of sodium channels are thought to be an important cause of sporadic epilepsy. The well established role of de novo mutations of sodium channel SCN1A in Dravet Syndrome supports this view, but the etiology of many cases of epileptic encephalopathy remains unknown. We sought to identify the genetic cause in a patient with early onset epileptic encephalopathy by whole exome sequencing of genomic DNA. The heterozygous mutation c. 2003C>T in SCN8A, the gene encoding sodium channel Nav1.6, was detected in the patient but was not present in either parent. The resulting missense substitution, p.Thr767Ile, alters an evolutionarily conserved residue in the first transmembrane segment of channel domain II. The electrophysiological effects of this mutation were assessed in neuronal cells transfected with mutant or wildtype cDNA. The mutation causes enhanced channel activation, with a 10mV depolarizing shift in voltage dependence of activation as well as increased ramp current. In addition, pyramidal hippocampal neurons expressing the mutant channel exhibit increased spontaneous firing with PDS-like complexes as well as increased frequency of evoked action potentials. The identification of this new gain-of-function mutation of Nav1.6 supports the inclusion of SCN8A as a causative gene in infantile epilepsy, demonstrates a novel mechanism for hyperactivity of Nav1.6, and further expands the role of de novo mutations in severe epilepsy.
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Affiliation(s)
- Mark Estacion
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, CT 06520, USA; The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Janelle E O'Brien
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA
| | | | - Michael F Hammer
- ARL Division of Biotechnology, University of Arizona, Tucson, AZ 85721, USA
| | - Stephen G Waxman
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, CT 06520, USA; The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516, USA
| | - Sulayman D Dib-Hajj
- The Center for Neuroscience & Regeneration Research, Yale School of Medicine, New Haven, CT 06520, USA; The Rehabilitation Research Center, VA Connecticut Healthcare System, West Haven, CT 06516, USA.
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA.
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Huang J, Han C, Estacion M, Vasylyev D, Hoeijmakers JGJ, Gerrits MM, Tyrrell L, Lauria G, Faber CG, Dib-Hajj SD, Merkies ISJ, Waxman SG. Gain-of-function mutations in sodium channel NaV1.9 in painful neuropathy. Brain 2014; 137:1627-42. [DOI: 10.1093/brain/awu079] [Citation(s) in RCA: 197] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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Ahn HS, Vasylyev DV, Estacion M, Macala LJ, Shah P, Faber CG, Merkies IS, Dib-Hajj SD, Waxman SG. Differential effect of D623N variant and wild-type Nav1.7 sodium channels on resting potential and interspike membrane potential of dorsal root ganglion neurons. Brain Res 2013; 1529:165-77. [DOI: 10.1016/j.brainres.2013.07.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 07/02/2013] [Accepted: 07/03/2013] [Indexed: 12/15/2022]
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Yang Y, Estacion M, Dib-Hajj SD, Waxman SG. Molecular architecture of a sodium channel S6 helix: radial tuning of the voltage-gated sodium channel 1.7 activation gate. J Biol Chem 2013; 288:13741-7. [PMID: 23536180 DOI: 10.1074/jbc.m113.462366] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND In-frame deletion mutation (Del-L955) in NaV1.7 sodium channel from a kindred with erythromelalgia hyperpolarizes activation. RESULTS Del-L955 twists the S6 helix, displacing the Phe960 activation gate. Replacement of Phe960 at the correct helical position depolarizes activation. CONCLUSION Radial tuning of the activation gate is critical to the activation of NaV1.7 channel. SIGNIFICANCE Structural modeling guided electrophysiology reveals the functional importance of radial tuning of the S6 segment. Voltage-gated sodium (NaV) channels are membrane proteins that consist of 24 transmembrane segments organized into four homologous domains and are essential for action potential generation and propagation. Although the S6 helices of NaV channels line the ion-conducting pore and participate in channel activation, their functional architecture is incompletely understood. Our recent studies show that a naturally occurring in-frame deletion mutation (Del-L955) of NaV1.7 channel, identified in individuals with a severe inherited pain syndrome (inherited erythromelalgia) causes a substantial hyperpolarizing shift of channel activation. Here we took advantage of this deletion mutation to understand the role of the S6 helix in the channel activation. Based on the recently published structure of a bacterial NaV channel (NaVAb), we modeled the WT and Del-L955 channel. Our structural model showed that Del-L955 twists the DII/S6 helix, shifting location and radial orientation of the activation gate residue (Phe(960)). Hypothesizing that these structural changes produce the shift of channel activation of Del-L955 channels, we restored a phenylalanine in wild-type orientation by mutating Ser(961) (Del-L955/S961F), correcting activation by ∼10 mV. Correction of the displaced Phe(960) (F960S) together with introduction of the rescuing activation gate residue (S961F) produced an additional ∼6-mV restoration of activation of the mutant channel. A simple point mutation in the absence of a twist (L955A) did not produce a radial shift and did not hyperpolarize activation. Our results demonstrate the functional importance of radial tuning of the sodium channel S6 helix for the channel activation.
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Affiliation(s)
- Yang Yang
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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Yang Y, Dib-Hajj SD, Zhang J, Zhang Y, Tyrrell L, Estacion M, Waxman SG. Structural modelling and mutant cycle analysis predict pharmacoresponsiveness of a Na(V)1.7 mutant channel. Nat Commun 2013; 3:1186. [PMID: 23149731 DOI: 10.1038/ncomms2184] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 10/02/2012] [Indexed: 11/09/2022] Open
Abstract
Sodium channel Na(V)1.7 is critical for human pain signalling. Gain-of-function mutations produce pain syndromes including inherited erythromelalgia, which is usually resistant to pharmacotherapy, but carbamazepine normalizes activation of Na(V)1.7-V400M mutant channels from a family with carbamazepine-responsive inherited erythromelalgia. Here we show that structural modelling and thermodynamic analysis predict pharmacoresponsiveness of another mutant channel (S241T) that is located 159 amino acids distant from V400M. Structural modelling reveals that Na(v)1.7-S241T is ~2.4 Å apart from V400M in the folded channel, and thermodynamic analysis demonstrates energetic coupling of V400M and S241T during activation. Atomic proximity and energetic coupling are paralleled by pharmacological coupling, as carbamazepine (30 μM) depolarizes S214T activation, as previously reported for V400M. Pharmacoresponsiveness of S241T to carbamazepine was further evident at a cellular level, where carbamazepine normalized the hyperexcitability of dorsal root ganglion neurons expressing S241T. We suggest that this approach might identify variants that confer enhanced pharmacoresponsiveness on a variety of channels.
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Affiliation(s)
- Yang Yang
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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Estacion M, Yang Y, Dib-Hajj SD, Tyrrell L, Lin Z, Yang Y, Waxman SG. A new Nav1.7 mutation in an erythromelalgia patient. Biochem Biophys Res Commun 2013; 432:99-104. [DOI: 10.1016/j.bbrc.2013.01.079] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Accepted: 01/18/2013] [Indexed: 12/19/2022]
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Abstract
NaV1.3 voltage-gated sodium channels have been shown to be expressed at increased levels within axotomized dorsal root ganglion neurons and within injured axons within neuromas and have been implicated in neuropathic pain. Like a number of other sodium channel isoforms, NaV1.3 channels produce a robust response to slow ramplike stimuli. Here we show that the response of NaV1.3 to ramp stimuli consists of two components: an early component, dependent upon ramp rate, that corresponds to a window current that is dependent upon closed-state inactivation; and a second component at more depolarized potentials that is correlated with persistent current which is detected for many tens of milliseconds after the start of a depolarizing pulse. We also assessed the K354Q NaV1.3 epilepsy-associated mutant channel, which is known to display an enhanced persistent current and demonstrate a strong correlation with the second component of the ramp response. Our results show that a single sodium channel isoform can produce a ramp response with multiple components, reflecting multiple mechanisms, and suggest that the upregulated expression of NaV1.3 in axotomized dorsal root ganglion neurons and enhanced ramp current in K354Q mutant channels can contribute in several ways to hyperexcitability and abnormal spontaneous firing that contribute to hyperexcitability disorders, such as epilepsy and neuropathic pain.
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Affiliation(s)
- Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Stephen G. Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut
- Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
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Estacion M, Han C, Choi JS, Hoeijmakers JGJ, Lauria G, Drenth JPH, Gerrits MM, Dib-Hajj SD, Faber CG, Merkies ISJ, Waxman SG. Intra- and interfamily phenotypic diversity in pain syndromes associated with a gain-of-function variant of NaV1.7. Mol Pain 2011; 7:92. [PMID: 22136189 PMCID: PMC3248882 DOI: 10.1186/1744-8069-7-92] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 12/02/2011] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Sodium channel NaV1.7 is preferentially expressed within dorsal root ganglia (DRG), trigeminal ganglia and sympathetic ganglion neurons and their fine-diamter axons, where it acts as a threshold channel, amplifying stimuli such as generator potentials in nociceptors. Gain-of-function mutations and variants (single amino acid substitutions) of NaV1.7 have been linked to three pain syndromes: Inherited Erythromelalgia (IEM), Paroxysmal Extreme Pain Disorder (PEPD), and Small Fiber Neuropathy (SFN). IEM is characterized clinically by burning pain and redness that is usually focused on the distal extremities, precipitated by mild warmth and relieved by cooling, and is caused by mutations that hyperpolarize activation, slow deactivation, and enhance the channel ramp response. PEPD is characterized by perirectal, periocular or perimandibular pain, often triggered by defecation or lower body stimulation, and is caused by mutations that severely impair fast-inactivation. SFN presents a clinical picture dominated by neuropathic pain and autonomic symptoms; gain-of-function variants have been reported to be present in approximately 30% of patients with biopsy-confirmed idiopathic SFN, and functional testing has shown altered fast-inactivation, slow-inactivation or resurgent current. In this paper we describe three patients who house the NaV1.7/I228M variant. METHODS We have used clinical assessment of patients, quantitative sensory testing and skin biopsy to study these patients, including two siblings in one family, in whom genomic screening demonstrated the I228M NaV1.7 variant. Electrophysiology (voltage-clamp and current-clamp) was used to test functional effects of the variant channel. RESULTS We report three different clinical presentations of the I228M NaV1.7 variant: presentation with severe facial pain, presentation with distal (feet, hands) pain, and presentation with scalp discomfort in three patients housing this NaV1.7 variant, two of which are from a single family. We also demonstrate that the NaV1.7/I228M variant impairs slow-inactivation, and produces hyperexcitability in both trigeminal ganglion and DRG neurons. CONCLUSION Our results demonstrate intra- and interfamily phenotypic diversity in pain syndromes produced by a gain-of-function variant of NaV1.7.
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Affiliation(s)
- Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
| | - Chongyang Han
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
| | - Jin-Sung Choi
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
- College of Pharmacy, Catholic University of Korea, Bucheon, South Korea
| | - Janneke GJ Hoeijmakers
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
| | - Giuseppe Lauria
- Neuromuscular Diseases Unit, IRCCS Foundation, "Carlo Besta", Milan, Italy
| | - Joost PH Drenth
- Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
| | - Monique M Gerrits
- Department of Clinical Genetics, University Medical Center Maastricht, Maastricht, the Netherlands
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
| | - Catharina G Faber
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
| | - Ingemar SJ Merkies
- Department of Neurology, University Medical Center Maastricht, Maastricht, the Netherlands
- Department of Neurology, Spaarne Hospital, Hoofddorp, the Netherlands
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, and Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06516, USA
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Faber CG, Hoeijmakers JGJ, Ahn HS, Cheng X, Han C, Choi JS, Estacion M, Lauria G, Vanhoutte EK, Gerrits MM, Dib-Hajj S, Drenth JPH, Waxman SG, Merkies ISJ. Gain of function NaV1.7 mutations in idiopathic small fiber neuropathy. Ann Neurol 2011; 71:26-39. [DOI: 10.1002/ana.22485] [Citation(s) in RCA: 394] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 05/10/2011] [Accepted: 05/13/2011] [Indexed: 11/10/2022]
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Estacion M, Waxman SG, Dib-Hajj SD. Effects of ranolazine on wild-type and mutant hNav1.7 channels and on DRG neuron excitability. Mol Pain 2010; 6:35. [PMID: 20529343 PMCID: PMC2898769 DOI: 10.1186/1744-8069-6-35] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Accepted: 06/08/2010] [Indexed: 12/19/2022] Open
Abstract
Background A direct role of sodium channels in pain has recently been confirmed by establishing a monogenic link between SCN9A, the gene which encodes sodium channel Nav1.7, and pain disorders in humans, with gain-of-function mutations causing severe pain syndromes, and loss-of-function mutations causing congenital indifference to pain. Expression of sodium channel Nav1.8 in DRG neurons has also been shown to be essential for the manifestation of mutant Nav1.7-induced neuronal hyperexcitability. These findings have confirmed key roles of Nav1.7 and Nav1.8 in pain and identify these channels as novel targets for pain therapeutic development. Ranolazine preferentially blocks cardiac late sodium currents at concentrations that do not significantly reduce peak sodium current. Ranolazine also blocks wild-type Nav1.7 and Nav1.8 channels in a use-dependent manner. However, ranolazine's effects on gain-of-function mutations of Nav1.7 and on DRG neuron excitability have not been investigated. We used voltage- and current-clamp recordings to evaluate the hypothesis that ranolazine may be effective in regulating Nav1.7-induced DRG neuron hyperexcitability. Results We show that ranolazine produces comparable block of peak and ramp currents of wild-type Nav1.7 and mutant Nav1.7 channels linked to Inherited Erythromelalgia and Paroxysmal Extreme Pain Disorder. We also show that ranolazine, at a clinically-relevant concentration, blocks high-frequency firing of DRG neurons expressing wild-type but not mutant channels. Conclusions Our data suggest that ranalozine can attenuate hyperexcitability of DRG neurons over-expressing wild-type Nav1.7 channels, as occurs in acquired neuropathic and inflammatory pain, and thus merits further study as an alternative to existing non-selective sodium channel blockers.
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Affiliation(s)
- Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA
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Estacion M, Gasser A, Dib-Hajj SD, Waxman SG. A sodium channel mutation linked to epilepsy increases ramp and persistent current of Nav1.3 and induces hyperexcitability in hippocampal neurons. Exp Neurol 2010; 224:362-8. [PMID: 20420834 DOI: 10.1016/j.expneurol.2010.04.012] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Revised: 04/12/2010] [Accepted: 04/16/2010] [Indexed: 01/11/2023]
Abstract
Voltage-gated sodium channelopathies underlie many excitability disorders. Genes SCN1A, SCN2A and SCN9A, which encode pore-forming alpha-subunits Na(V)1.1, Na(V)1.2 and Na(V)1.7, are clustered on human chromosome 2, and mutations in these genes have been shown to underlie epilepsy, migraine, and somatic pain disorders. SCN3A, the gene which encodes Na(V)1.3, is part of this cluster, but until recently was not associated with any mutation. A charge-neutralizing mutation, K345Q, in the Na(V)1.3 DI/S5-6 linker has recently been identified in a patient with cryptogenic partial epilepsy. Pathogenicity of the Na(V)1.3/K354Q mutation has been inferred from the conservation of this residue in all sodium channels and its absence from control alleles, but functional analysis has been limited to the corresponding substitution in the cardiac muscle sodium channel Na(V)1.5. Since identical mutations may produce different effects within different sodium channel isoforms, we assessed the K354Q mutation within its native Na(V)1.3 channel and studied the effect of the mutant Na(V)1.3/K354Q channels on hippocampal neuron excitability. We show here that the K354Q mutation enhances the persistent and ramp currents of Na(V)1.3, reduces current threshold and produces spontaneous firing and paroxysmal depolarizing shift-like complexes in hippocampal neurons. Our data provide a pathophysiological basis for the pathogenicity of the first epilepsy-linked mutation within Na(V)1.3 channels and hippocampal neurons.
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Affiliation(s)
- Mark Estacion
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA.
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Estacion M, Choi JS, Eastman EM, Lin Z, Li Y, Tyrrell L, Yang Y, Dib-Hajj SD, Waxman SG. Can robots patch-clamp as well as humans? Characterization of a novel sodium channel mutation. J Physiol 2010; 588:1915-27. [PMID: 20123784 DOI: 10.1113/jphysiol.2009.186114] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Ion channel missense mutations cause disorders of excitability by changing channel biophysical properties. As an increasing number of new naturally occurring mutations have been identified, and the number of other mutations produced by molecular approaches such as in situ mutagenesis has increased, the need for functional analysis by patch-clamp has become rate limiting. Here we compare a patch-clamp robot using planar-chip technology with human patch-clamp in a functional assessment of a previously undescribed Nav1.7 sodium channel mutation, S211P, which causes erythromelalgia. This robotic patch-clamp device can increase throughput (the number of cells analysed per day) by 3- to 10-fold. Both modes of analysis show that the mutation hyperpolarizes activation voltage dependence (8 mV by manual profiling, 11 mV by robotic profiling), alters steady-state fast inactivation so that it requires an additional Boltzmann function for a second fraction of total current (approximately 20% manual, approximately 40% robotic), and enhances slow inactivation (hyperpolarizing shift--15 mV by human,--13 mV robotic). Manual patch-clamping demonstrated slower deactivation and enhanced (approximately 2-fold) ramp response for the mutant channel while robotic recording did not, possibly due to increased temperature and reduced signal-to-noise ratio on the robotic platform. If robotic profiling is used to screen ion channel mutations, we recommend that each measurement or protocol be validated by initial comparison to manual recording. With this caveat, we suggest that, if results are interpreted cautiously, robotic patch-clamp can be used with supervision and subsequent confirmation from human physiologists to facilitate the initial profiling of a variety of electrophysiological parameters of ion channel mutations.
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Affiliation(s)
- M Estacion
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA
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Estacion M, Harty TP, Choi JS, Tyrrell L, Dib-Hajj SD, Waxman SG. A sodium channel geneSCN9Apolymorphism that increases nociceptor excitability. Ann Neurol 2009; 66:862-6. [DOI: 10.1002/ana.21895] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Sinkins WG, Estacion M, Prasad V, Goel M, Shull GE, Kunze DL, Schilling WP. Maitotoxin converts the plasmalemmal Ca(2+) pump into a Ca(2+)-permeable nonselective cation channel. Am J Physiol Cell Physiol 2009; 297:C1533-43. [PMID: 19794142 DOI: 10.1152/ajpcell.00252.2009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Maitotoxin (MTX) activates Ca(2+)-permeable nonselective cation channels and causes a dramatic increase in cytosolic free Ca(2+) concentration ([Ca(2+)](i)) in every cell examined to date, but the molecular identity of the channels involved remains unknown. A clue came from studies of a structurally related marine toxin called palytoxin (PTX). PTX binds to the plasmalemmal Na(+)-K(+)-ATPase (NKA) and converts the Na(+) pump into a nonselective cation channel. Given the high permeability of the MTX channel for Ca(2+), we considered the possibility that MTX may bind to the plasmalemmal Ca(2+)-ATPase (PMCA) pump, and like PTX, convert the pump into a channel. To test this hypothesis, the PMCA was overexpressed in Spodoptera frugiperda (Sf9) insect cells and in human embryonic kidneys (HEK) 293 cells. In both cell types, enhanced expression of the PMCA was associated with a significant increase in MTX-induced whole cell membrane currents. The effect of MTX on whole cell currents in both wild-type and PMCA overexpressing HEK cells was sensitive to pump ligands including Ca(2+) and ATP. MTX-induced currents were significantly reduced by knockdown of PMCA1 in HEK cells using small interfering RNA or in mouse embryonic fibroblasts from genetically modified mice with the PMCA1(+/-) PMCA4(-/-) genotype. Finally, PMCA catalytic activity (i.e., Ca(2+)-ATPase) in isolated membranes, or in purified PMCA preparations, was inhibited by MTX. Together, these results suggest that MTX binds to and converts the PMCA pump into a Ca(2+)-permeable nonselective cation channel.
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Affiliation(s)
- William G Sinkins
- Department of Physiology, Rammelkamp Center for Education and Research, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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Fischer TZ, Gilmore ES, Estacion M, Eastman E, Taylor S, Melanson M, Dib-Hajj SD, Waxman SG. A novel Nav1.7 mutation producing carbamazepine-responsive erythromelalgia. Ann Neurol 2009; 65:733-41. [PMID: 19557861 DOI: 10.1002/ana.21678] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Human and animal studies have shown that Na(v)1.7 sodium channels, which are preferentially expressed within nociceptors and sympathetic neurons, play a major role in inflammatory and neuropathic pain. Inherited erythromelalgia (IEM) has been linked to gain-of-function mutations of Na(v)1.7. We now report a novel mutation (V400M) in a three-generation Canadian family in which pain is relieved by carbamazepine (CBZ). METHODS We extracted genomic DNA from blood samples of eight members of the family, and the sequence of SCN9A coding exons was compared with the reference Na(v)1.7 complementary DNA. Wild-type Na(v)1.7 and V400M cell lines were then analyzed using whole-cell patch-clamp recording for changes in activation, deactivation, steady-state inactivation, and ramp currents. RESULTS Whole-cell patch-clamp studies of V400M demonstrate changes in activation, deactivation, steady-state inactivation, and ramp currents that can produce dorsal root ganglia neuron hyperexcitability that underlies pain in these patients. We show that CBZ, at concentrations in the human therapeutic range, normalizes the voltage dependence of activation and inactivation of this inherited erythromelalgia mutation in Na(v)1.7 but does not affect these parameters in wild-type Na(v)1.7. INTERPRETATION Our results demonstrate a normalizing effect of CBZ on mutant Na(v)1.7 channels in this kindred with CBZ-responsive inherited erythromelalgia. The selective effect of CBZ on the mutant Na(v)1.7 channel appears to explain the ameliorative response to treatment in this kindred. Our results suggest that functional expression and pharmacological studies may provide mechanistic insights into hereditary painful disorders.
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Affiliation(s)
- Tanya Z Fischer
- Department of Neurology, Yale University School of Medicine, New Haven, CT 16510, USA
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Abstract
We provide here detailed electrophysiological protocols to study voltage-gated sodium channels and to investigate how wild-type and mutant channels influence firing properties of transfected mammalian dorsal root ganglion (DRG) neurons. Whole-cell voltage-clamp recordings permit us to analyze kinetic and voltage-dependence properties of ion channels and to determine the effect and mode of action of pharmaceuticals on specific channel isoforms. They also permit us to analyze the role of individual sodium channels and their mutant derivatives in regulating firing of DRG neurons. Five to ten cells can be recorded daily, depending on the extent of analysis that is required. Because of different internal solutions that are used in voltage-clamp and current-clamp recordings, only limited information can be obtained from recording the same neuron in both modes. These electrophysiological studies help to elucidate the role of specific channels in setting threshold and suprathreshold responses of neurons, under normal and pathological conditions.
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Affiliation(s)
- Theodore R Cummins
- Department of Pharmacology and Toxicology, Stark Neurosciences Institute, Indiana University School of Medicine, Indianapolis, IN, USA
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Dib-Hajj SD, Estacion M, Jarecki BW, Tyrrell L, Fischer TZ, Lawden M, Cummins TR, Waxman SG. Paroxysmal extreme pain disorder M1627K mutation in human Nav1.7 renders DRG neurons hyperexcitable. Mol Pain 2008; 4:37. [PMID: 18803825 PMCID: PMC2556659 DOI: 10.1186/1744-8069-4-37] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Accepted: 09/19/2008] [Indexed: 01/20/2023] Open
Abstract
Background Paroxysmal extreme pain disorder (PEPD) is an autosomal dominant painful neuropathy with many, but not all, cases linked to gain-of-function mutations in SCN9A which encodes voltage-gated sodium channel Nav1.7. Severe pain episodes and skin flushing start in infancy and are induced by perianal probing or bowl movement, and pain progresses to ocular and mandibular areas with age. Carbamazepine has been effective in relieving symptoms, while other drugs including other anti-epileptics are less effective. Results Sequencing of SCN9A coding exons from an English patient, diagnosed with PEPD, has identified a methionine 1627 to lysine (M1627K) substitution in the linker joining segments S4 and S5 in domain IV. We confirm that M1627K depolarizes the voltage-dependence of fast-inactivation without substantially altering activation or slow-inactivation, and inactivates from the open state with slower kinetics. We show here that M1627K does not alter development of closed-state inactivation, and that M1627K channels recover from fast-inactivation faster than wild type channels, and produce larger currents in response to a slow ramp stimulus. Using current-clamp recordings, we also show that the M1627K mutant channel reduces the threshold for single action potentials in DRG neurons and increases the number of action potentials in response to graded stimuli. Conclusion M1627K mutation was previously identified in a sporadic case of PEPD from France, and we now report it in an English family. We confirm the initial characterization of mutant M1627K effect on fast-inactivation of Nav1.7 and extend the analysis to other gating properties of the channel. We also show that M1627K mutant channels render DRG neurons hyperexcitable. Our new data provide a link between altered channel biophysics and pain in PEPD patients.
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Affiliation(s)
- Sulayman D Dib-Hajj
- Deptartment of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA.
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Affiliation(s)
- Stephen G Waxman
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA.
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Abstract
The plasmalemmal Na(+)-K(+)-ATPase (NKA) pump is the receptor for the potent marine toxin palytoxin (PTX). PTX binds to the NKA and converts the pump into a monovalent cation channel that exhibits a slight permeability to Ca(2+). However, the ability of PTX to directly increase cytosolic free Ca(2+) concentration ([Ca(2+)](i)) via Na(+) pump channels and to initiate Ca(2+) overload-induced oncotic cell death has not been examined. Thus the purpose of this study was to determine the effect of PTX on [Ca(2+)](i) and the downstream events associated with cell death in bovine aortic endothelial cells. PTX (3-100 nM) produced a graded increase in [Ca(2+)](i) that was dependent on extracellular Ca(2+). The increase in [Ca(2+)](i) initiated by 100 nM PTX was blocked by pretreatment with ouabain with an IC(50) < 1 microM. The elevation in [Ca(2+)](i) could be reversed by addition of ouabain at various times after PTX, but this required much higher concentrations of ouabain (0.5 mM). These results suggest that the PTX-induced rise in [Ca(2+)](i) occurs via the Na(+) pump. Subsequent to the rise in [Ca(2+)](i), PTX also caused a concentration-dependent increase in uptake of the vital dye ethidium bromide (EB) but not YO-PRO-1. EB uptake was also blocked by ouabain added either before or after PTX. Time-lapse video microscopy showed that PTX ultimately caused cell lysis as indicated by release of transiently expressed green fluorescent protein (molecular mass 27 kDa) and rapid uptake of propidium iodide. Cell lysis was 1) greatly delayed by removing extracellular Ca(2+) or by adding ouabain after PTX, 2) blocked by the cytoprotective amino acid glycine, and 3) accompanied by dramatic membrane blebbing. These results demonstrate that PTX initiates a cell death cascade characteristic of Ca(2+) overload.
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Affiliation(s)
- William P Schilling
- Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, OH 44109-1998, USA.
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Estacion M, Sinkins WG, Jones SW, Applegate MAB, Schilling WP. Human TRPC6 expressed in HEK 293 cells forms non-selective cation channels with limited Ca2+ permeability. J Physiol 2006; 572:359-77. [PMID: 16439426 PMCID: PMC1779672 DOI: 10.1113/jphysiol.2005.103143] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
TRPC6 is thought to be a Ca(2+)-permeable cation channel activated following stimulation of G-protein-coupled membrane receptors linked to phospholipase C (PLC). TRPC6 current is also activated by exogenous application of 1-oleoyl-acetyl-sn-glycerol (OAG) or by inhibiting 1,2-diacylglycerol (DAG) lipase activity using RHC80267. In the present study, both OAG and RHC80267 increased whole-cell TRPC6 current in cells from a human embryonic kidney cell line (HEK 293) stably expressing TRPC6, but neither compound increased cytosolic free Ca(2+) concentration ([Ca(2+)](i)) when the cells were bathed in high-K(+) buffer to hold the membrane potential near 0 mV. These results suggested that TRPC6 channels have limited Ca(2+) permeability relative to monovalent cation permeability and/or that Ca(2+) influx via TRPC6 is greatly attenuated by depolarization. To evaluate Ca(2+) permeability, TRPC6 currents were examined in extracellular buffer in which Ca(2+) was varied from 0.02 to 20 mm. The results were consistent with a pore-permeation model in which Ca(2+) acts primarily as a blocking ion and contributes only a small percentage ( approximately 4%) to whole-cell currents in the presence of extracellular Na(+). Measurement of single-cell fura-2 fluorescence during perforated-patch recording of TRPC6 currents showed that OAG increased [Ca(2+)](i) 50-100 nm when the membrane potential was clamped at between -50 and -80 mV, but had little or no effect if the membrane potential was left uncontrolled. These results suggest that in cells exhibiting a high input resistance, the primary effect of activating TRPC6 will be membrane depolarization. However, in cells able to maintain a hyperpolarized potential (e.g. cells with a large inwardly rectifying or Ca(2+)-activated K(+) current), activation of TRPC6 will lead to a sustained increase in [Ca(2+)](i). Thus, the contribution of TRPC6 current to both the kinetics and magnitude of the Ca(2+) response will be cell specific and dependent upon the complement of other channel types.
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Affiliation(s)
- Mark Estacion
- Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, OH 44109-1998, USA
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Abstract
It is well established that transient receptor potential (TRP) channels are activated following stimulation of G protein-coupled membrane receptors linked to PLC, but their differential expression in various cells of the renal nephron has not been described. In the present study, immunoprecipitations from rat kidney lysates followed by Western blot analysis using TRPC-specific, affinity-purified antibodies revealed the presence of TRPC1, -C3, and -C6. TRPC4, -C5, and -C7 were nondetectable. TRPC1 immunofluorescence was detected in glomeruli and specific tubular cells of the cortex and outer medulla. TRPC1 colocalized with aquaporin-1, a marker for proximal tubule and thin descending limb, but not with aquaporin-2, a marker for connecting tubule and collecting duct cells. TRPC3 and -C6 immunolabeling was predominantly confined to glomeruli and specific tubular cells of the cortex and both the outer and inner medulla. TRPC3 and -C6 colocalized with aquaporin-2, but not with the Na(+)/Ca(2+) exchanger or peanut lectin. Thus TRPC3 and -C6 proteins are expressed in principle cells of the collecting duct. In polarized cultures of M1 and IMCD-3 collecting duct cells, TRPC3 was localized exclusively to the apical domain, whereas TRPC6 was found in both the basolateral and apical membranes. TRPC3 and TRPC6 were also detected in primary podocyte cultures, whereas TRPC1 was exclusively expressed in mesangial cell cultures. Specific immunopositive labeling for TRPC4, -C5, or -C7 was not observed in kidney sections or cell lines. These results suggest that TRPC1, -C3, and -C6 may play a functional role in PLC-dependent signaling in specific regions of the nephron.
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Affiliation(s)
- Monu Goel
- Rammelkamp Ctr. for Education and Research, Rm. R-322, MetroHealth Medical Ctr., 2500 MetroHealth Dr., Cleveland, OH 44109-1998, USA
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Verhoef PA, Kertesy SB, Estacion M, Schilling WP, Dubyak GR. Maitotoxin induces biphasic interleukin-1beta secretion and membrane blebbing in murine macrophages. Mol Pharmacol 2004. [PMID: 15385641 DOI: 10.1124/mol.66.4.] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Maitotoxin (MTX) is a potent shellfish toxin widely used as an in vitro tool for increasing intracellular Ca2+ and studying Ca2+ -dependent processes. MTX also induces membrane blebbing and nonselective pores similar to those elicited by the P2X7 receptor (P2X7R), an ATP-gated cation channel expressed in inflammatory leukocytes. We therefore tested whether MTX treatment of lipopolysaccharide-primed murine macrophages would mimic the ability of activated P2X7R to induce secretion of the proinflammatory cytokine interleukin-1beta (IL-1beta). MTX at < or = 0.6 nM predominantly induced processing and nonlytic release of mature IL-1beta (mIL-1beta), whereas >0.6 nM of MTX induced cytolytic release of unprocessed proIL-1beta. MTX-dependent release of mIL-1beta (but not cytolysis) was inhibited by the elimination of the trans-plasma membrane K+ gradient. MTX-induced cytokine release and cytolysis were both abrogated in the absence of extracellular Ca2+. On the other hand, extracellular glycine (5 mM) blocked MTX-induced cytolytic release of proIL-1beta without affecting regulated secretion of mIL-1beta. Because MTX has profound effects on plasma membrane permeability, we used time-lapse videography to examine the morphologic response of individual macrophages to MTX. MTX treatment led to biphasic propidium dye uptake and dilated blebbing coincident with cytolysis. Glycine completely blocked the second, lytic phase of dye uptake and prevented MTX-induced bleb dilation. These results indicate that the inflammatory macrophage can assemble the necessary signaling components to initiate both regulated and lytic release of IL-1beta in response to MTX. This suggests that the hyperactivation of proinflammatory cytokine secretion may be a significant component of the in vivo response to MTX during shellfish seafood poisoning.
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Affiliation(s)
- Philip A Verhoef
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106-4970, USA
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Sinkins WG, Goel M, Estacion M, Schilling WP. Association of immunophilins with mammalian TRPC channels. Vol. 279 (2004) 34521–34529. J Biol Chem 2004. [DOI: 10.1016/s0021-9258(20)72708-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Verhoef PA, Kertesy SB, Estacion M, Schilling WP, Dubyak GR. Maitotoxin Induces Biphasic Interleukin-1β Secretion and Membrane Blebbing in Murine Macrophages. Mol Pharmacol 2004. [DOI: 10.1124/mol.66.4.909] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Abstract
Drosophila photoreceptor channels TRP and TRPL are held in a large signalplex by the scaffolding protein, INAD. Immunophilin FKBP59, another member of the signalplex, binds to both INAD and TRPL. Mutation P702Q or P709Q in the highly conserved TRPL sequence (701)LPPPFNVLP(709), eliminates TRPL interaction with FKBP59. The first leucylprolyl (LP) dipeptide in this region is conserved in mammalian TRPC channel proteins. However, the second LP is changed to isoleucylprolyl (IP) in TRPC1, -C4, and -C5, and valylprolyl (VP) in TRPC3, -C6, and -C7. The purpose of the present study was to determine if mammalian FKBP12 or FKBP52 interact with TRPC channel proteins. Using TRPC-specific antibodies, immunoprecipitations from Sf9 cells individually co-expressing each of the TRPC proteins along with the immunophilins showed that TRPC3, -C6, and -C7 interact with FKBP12, whereas TRPC1, -C4, and -C5 interact with FKBP52. The binding of FKBP12 and FKBP52 was specific and could be displaced by the immunosuppressant drug FK506, at concentrations of 0.5 and 10 microm, respectively. To evaluate TRPC-immunophilin interactions in vivo, immunoprecipitations were performed using membrane lysates of rat cerebral cortex. FKBP12 co-immunoprecipitated with TRPC3, -C6, and -C7 from rat brain, whereas FKBP52 was found to associate with TRPC1, -C4, and -C5. The association of immunophilins with the TRPC channels in rat brain lysates could be displaced by FK506. Receptor-mediated activation of TRPC6, stably expressed in HEK cells, was significantly inhibited by FK506, which also disrupted interaction between TRPC6 and the endogenous immunophilin found in HEK cells. Pro to Gln mutations in the first LP dipeptide in the putative FKBP binding domain eliminated FKBP12 and FKBP52 interaction with TRPC3 and -C6, and TRPC1 and -C4, respectively. However, mutual swap of VP and IP in TRPC3 and TRPC5 did not alter the association or the selectivity of the channels for their respective immunophilin binding partner. These results suggest that immunophilins are TRPC channel accessory proteins that play an important role in the mechanism of channel activation following receptor stimulation.
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Affiliation(s)
- William G Sinkins
- Rammelkamp Center for Education and Research, MetroHealth Medical Center, 2500 MetroHealth Drive, Cleveland, OH 44109-1998, USA
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Wisnoskey BJ, Estacion M, Schilling WP. Maitotoxin-induced cell death cascade in bovine aortic endothelial cells: divalent cation specificity and selectivity. Am J Physiol Cell Physiol 2004; 287:C345-56. [PMID: 15044153 DOI: 10.1152/ajpcell.00473.2003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The maitotoxin (MTX)-induced cell death cascade in bovine aortic endothelial cells (BAECs), a model for Ca(2+) overload-induced toxicity, reflects three sequential changes in plasmalemmal permeability. MTX initially activates Ca(2+)-permeable, nonselective cation channels (CaNSC) and causes a massive increase in cytosolic free Ca(2+) concentration ([Ca(2+)](i)). This is followed by the opening of large endogenous cytolytic/oncotic pores (COP) that allow molecules <800 Da to enter the cell. The cells then lyse not by rupture of the plasmalemma but through the activation of a "death" channel that lets large proteins (e.g., 140-160 kDa) leave the cell. These changes in permeability are accompanied by the formation of membrane blebs. In this study, we took advantage of the well-known differences in affinity of various Ca(2+)-binding proteins for Ca(2+) and Sr(2+) vs. Ba(2+) to probe their involvement in each phase of the cell death cascade. Using fluorescence techniques at the cell population level (cuvette-based) and at the single-cell level (time-lapse videomicroscopy), we found that the replacement of Ca(2+) with either Sr(2+) or Ba(2+) delayed both MTX-induced activation of COP, as indicated by the uptake of ethidium bromide, and subsequent cell lysis, as indicated by the uptake of propidium iodide or the release of cell-associated green fluorescent protein. MTX-induced responses were mimicked by ionomycin and were significantly delayed in BAPTA-loaded cells. Experiments at the single-cell level revealed that Ba(2+) not only delayed the time to cell lysis but also caused desynchronization of the lytic phase. Last, membrane blebs, which were numerous and spherical in Ca(2+)-containing solutions, were poorly defined and greatly reduced in number in the presence of Ba(2+). Taken together, these results suggest that intracellular high-affinity Ca(2+)-binding proteins are involved in the MTX-induced changes in plasmalemmal permeability that are responsible for cell demise.
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Affiliation(s)
- Brian J Wisnoskey
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44109-1998, USA
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