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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: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [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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202
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Schmalhofer WA, Calhoun J, Burrows R, Bailey T, Kohler MG, Weinglass AB, Kaczorowski GJ, Garcia ML, Koltzenburg M, Priest BT. ProTx-II, a selective inhibitor of NaV1.7 sodium channels, blocks action potential propagation in nociceptors. Mol Pharmacol 2008; 74:1476-84. [PMID: 18728100 DOI: 10.1124/mol.108.047670] [Citation(s) in RCA: 231] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Voltage-gated sodium (Na(V)1) channels play a critical role in modulating the excitability of sensory neurons, and human genetic evidence points to Na(V)1.7 as an essential contributor to pain signaling. Human loss-of-function mutations in SCN9A, the gene encoding Na(V)1.7, cause channelopathy-associated indifference to pain (CIP), whereas gain-of-function mutations are associated with two inherited painful neuropathies. Although the human genetic data make Na(V)1.7 an attractive target for the development of analgesics, pharmacological proof-of-concept in experimental pain models requires Na(V)1.7-selective channel blockers. Here, we show that the tarantula venom peptide ProTx-II selectively interacts with Na(V)1.7 channels, inhibiting Na(V)1.7 with an IC(50) value of 0.3 nM, compared with IC(50) values of 30 to 150 nM for other heterologously expressed Na(V)1 subtypes. This subtype selectivity was abolished by a point mutation in DIIS3. It is interesting that application of ProTx-II to desheathed cutaneous nerves completely blocked the C-fiber compound action potential at concentrations that had little effect on Abeta-fiber conduction. ProTx-II application had little effect on action potential propagation of the intact nerve, which may explain why ProTx-II was not efficacious in rodent models of acute and inflammatory pain. Mono-iodo-ProTx-II ((125)I-ProTx-II) binds with high affinity (K(d) = 0.3 nM) to recombinant hNa(V)1.7 channels. Binding of (125)I-ProTx-II is insensitive to the presence of other well characterized Na(V)1 channel modulators, suggesting that ProTx-II binds to a novel site, which may be more conducive to conferring subtype selectivity than the site occupied by traditional local anesthetics and anticonvulsants. Thus, the (125)I-ProTx-II binding assay, described here, offers a new tool in the search for novel Na(V)1.7-selective blockers.
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203
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Xiao Y, Bingham JP, Zhu W, Moczydlowski E, Liang S, Cummins TR. Tarantula huwentoxin-IV inhibits neuronal sodium channels by binding to receptor site 4 and trapping the domain ii voltage sensor in the closed configuration. J Biol Chem 2008; 283:27300-13. [PMID: 18628201 DOI: 10.1074/jbc.m708447200] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Peptide toxins with high affinity, divergent pharmacological functions, and isoform-specific selectivity are powerful tools for investigating the structure-function relationships of voltage-gated sodium channels (VGSCs). Although a number of interesting inhibitors have been reported from tarantula venoms, little is known about the mechanism for their interaction with VGSCs. We show that huwentoxin-IV (HWTX-IV), a 35-residue peptide from tarantula Ornithoctonus huwena venom, preferentially inhibits neuronal VGSC subtypes rNav1.2, rNav1.3, and hNav1.7 compared with muscle subtypes rNav1.4 and hNav1.5. Of the five VGSCs examined, hNav1.7 was most sensitive to HWTX-IV (IC(50) approximately 26 nM). Following application of 1 microm HWTX-IV, hNav1.7 currents could only be elicited with extreme depolarizations (>+100 mV). Recovery of hNav1.7 channels from HWTX-IV inhibition could be induced by extreme depolarizations or moderate depolarizations lasting several minutes. Site-directed mutagenesis analysis indicated that the toxin docked at neurotoxin receptor site 4 located at the extracellular S3-S4 linker of domain II. Mutations E818Q and D816N in hNav1.7 decreased toxin affinity for hNav1.7 by approximately 300-fold, whereas the reverse mutations in rNav1.4 (N655D/Q657E) and the corresponding mutations in hNav1.5 (R812D/S814E) greatly increased the sensitivity of the muscle VGSCs to HWTX-IV. Our data identify a novel mechanism for sodium channel inhibition by tarantula toxins involving binding to neurotoxin receptor site 4. In contrast to scorpion beta-toxins that trap the IIS4 voltage sensor in an outward configuration, we propose that HWTX-IV traps the voltage sensor of domain II in the inward, closed configuration.
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Affiliation(s)
- Yucheng Xiao
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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204
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Jarecki BW, Sheets PL, Jackson JO, Cummins TR. Paroxysmal extreme pain disorder mutations within the D3/S4-S5 linker of Nav1.7 cause moderate destabilization of fast inactivation. J Physiol 2008; 586:4137-53. [PMID: 18599537 DOI: 10.1113/jphysiol.2008.154906] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Single-point missense mutations in the peripheral neuronal voltage-gated sodium channel Nav1.7 are implicated in the painful inherited neuropathy paroxysmal extreme pain disorder (PEPD). The Nav1.7 PEPD mutations are located in regions of the channel suggested to play important roles in fast inactivation. PEPD mutations in the putative inactivation gate have been reported to significantly impair fast inactivation, resulting in pronounced persistent currents. However, PEPD mutations in the S4-S5 linker of domain 3 (D3/S4-S5) had not been characterized and the roles of specific residues in this linker in channel gating are unclear. We functionally characterized two of the D3/S4-S5 PEPD mutations (V1298F and V1299F) and compared their effects on gating to an adjacent non-PEPD mutation (V1300F) and the I1461T PEPD mutation, located in the putative inactivation gate. The primary effect of the V1298F and V1299F mutations is to shift the voltage dependence of fast inactivation by approximately 20 mV in the depolarizing direction. We observed a similar effect with the PEPD mutation I1461T. Interestingly, while all three PEPD mutations increased persistent currents, the relative amplitudes (approximately 6% of peak) were much smaller than previously reported for the I1461T mutation. In contrast, the main effect of the V1300F mutation was a depolarizing shift in the voltage dependence of activation. These data demonstrate that (1) mutations within D3/S4-S5 affect inactivation of Nav1.7 in a residue-specific manner and (2) disruption of the fast-inactivated state by PEPD mutations can be more moderate than previously indicated, which has important implications for the pathophysiology of PEPD.
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Affiliation(s)
- Brian W Jarecki
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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205
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Carlin KP, Liu J, Jordan LM. Postnatal Changes in the Inactivation Properties of Voltage-Gated Sodium Channels Contribute to the Mature Firing Pattern of Spinal Motoneurons. J Neurophysiol 2008; 99:2864-76. [DOI: 10.1152/jn.00059.2008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Most mammals are born with the necessary spinal circuitry to produce a locomotor-like pattern of neural activity. However, rodents seldom demonstrate weight-supported locomotor behavior until the second or third postnatal week, possibly due to the inability of the neuromuscular system to produce sufficient force during this early postnatal period. As spinal motoneurons mature they are seen to fire an increasing number of action potentials at an increasing rate, which is a necessary component of greater force production. The mechanisms responsible for this enhanced ability of motoneurons are not completely defined. In the present study we assessed the biophysical properties of the developing voltage-gated sodium current to determine their role in the maturing firing pattern. Using dissociated postnatal lumbar motoneurons in short-term culture (18–24 h) we demonstrate that currents recorded from the most mature postnatal age group (P10–P12) were significantly better able to maintain channels in an available state during repetitive stimulation than were the younger age groups (P1–P3, P4–P6, P7–P9). This ability correlated with the ability of channels to recover more quickly and more completely from an inactivated state. These age-related differences were seen in the absence of changes in the voltage dependence of channel gating. Differences in both closed-state inactivation and slow inactivation were also noted between the age groups. The results indicate that changes in the inactivation properties of voltage-gated sodium channels are important for the development of a mature firing pattern in spinal motoneurons.
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206
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Sheets PL, Heers C, Stoehr T, Cummins TR. Differential Block of Sensory Neuronal Voltage-Gated Sodium Channels by Lacosamide [(2R)-2-(Acetylamino)-N-benzyl-3-methoxypropanamide], Lidocaine, and Carbamazepine. J Pharmacol Exp Ther 2008; 326:89-99. [DOI: 10.1124/jpet.107.133413] [Citation(s) in RCA: 150] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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207
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Chatelier A, Dahllund L, Eriksson A, Krupp J, Chahine M. Biophysical properties of human Na v1.7 splice variants and their regulation by protein kinase A. J Neurophysiol 2008; 99:2241-50. [PMID: 18337362 DOI: 10.1152/jn.01350.2007] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The sodium channel Na(v)1.7 is preferentially expressed in nociceptive neurons and is believed to play a crucial role in pain sensation. Four alternative splice variants are expressed in human dorsal root ganglion neurons, two of which differ in exon 5 by two amino acids in the S3 segment of domain I (exons 5A and 5N). Two others differ in exon 11 by the presence (11L) or absence (11S) of an 11 amino acid sequence in the loop between domains I and II, an important region for PKA regulation. In the present study, we used the whole cell configuration of the patch-clamp technique to investigate the biophysical properties and 8-bromo-cyclic adenosine monophosphate (8Br-cAMP) modulation of these splice variants expressed in tsA201 cells in the presence of the beta(1)-subunit. The alternative splicing of Na(v)1.7 had no effect on most of the biophysical properties of this channel, including activation, inactivation, and recovery from inactivation. However, development of inactivation experiments revealed that the isoform containing exon 5A had slower kinetics of inactivation for negative potentials than that of the variant containing exon 5N. This difference was associated with higher ramp current amplitudes for isoforms containing exon 5A. Moreover, 8Br-cAMP-mediated phosphorylation induced a negative shift of the activation curve of variants containing exon 11S, whereas inactivation properties were unchanged. Isoforms with exon 11L were not modulated by 8Br-cAMP-induced phosphorylation. We conclude that alternative splicing of human Na(v)1.7 can specifically modulate the biophysical properties and cAMP-mediated regulation of this channel. Changing the proportions of these variants may thus influence neuronal excitability and pain sensation.
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Affiliation(s)
- Aurélien Chatelier
- Centre de Recherche, Université Laval Robert-Giffard, 2601 chemin de la Canardière, Quebec City, QC, Canada
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208
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Drenth JPH, Waxman SG. Mutations in sodium-channel gene SCN9A cause a spectrum of human genetic pain disorders. J Clin Invest 2008; 117:3603-9. [PMID: 18060017 DOI: 10.1172/jci33297] [Citation(s) in RCA: 252] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The voltage-gated sodium-channel type IX alpha subunit, known as Na(v)1.7 and encoded by the gene SCN9A, is located in peripheral neurons and plays an important role in action potential production in these cells. Recent genetic studies have identified Na(v)1.7 dysfunction in three different human pain disorders. Gain-of-function missense mutations in Na(v)1.7 have been shown to cause primary erythermalgia and paroxysmal extreme pain disorder, while nonsense mutations in Na(v)1.7 result in loss of Na(v)1.7 function and a condition known as channelopathy-associated insensitivity to pain, a rare disorder in which affected individuals are unable to feel physical pain. This review highlights these recent developments and discusses the critical role of Na(v)1.7 in pain sensation in humans.
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Affiliation(s)
- Joost P H Drenth
- Department of Medicine, Division of Gastroenterology and Hepatology, University Medical Center St. Radboud, Nijmegen, The Netherlands.
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209
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Cheng X, Dib-Hajj SD, Tyrrell L, Waxman SG. Mutation I136V alters electrophysiological properties of the Na(v)1.7 channel in a family with onset of erythromelalgia in the second decade. Mol Pain 2008; 4:1. [PMID: 18171466 PMCID: PMC2262064 DOI: 10.1186/1744-8069-4-1] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Accepted: 01/02/2008] [Indexed: 12/19/2022] Open
Abstract
Background Primary erythromelalgia is an autosomal dominant pain disorder characterized by burning pain and skin redness in the extremities, with onset of symptoms during the first decade in the families whose mutations have been physiologically studied to date. Several mutations of voltage-gated Na+ channel NaV1.7 have been linked with primary erythromelalgia. Recently, a new substitution NaV1.7/I136V has been reported in a Taiwanese family, in which pain appeared at later ages (9–22 years, with onset at 17 years of age or later in 5 of 7 family members), with relatively slow progression (8–10 years) to involvement of the hands. The proband reported onset of symptoms first in his feet at the age of 11, which then progressed to his hands at the age of 19. The new mutation is located in transmembrane segment 1 (S1) of domain I (DI) in contrast to all NaV1.7 mutations reported to date, which have been localized in the voltage sensor S4, the linker joining segments S4 and S5 or pore-lining segments S5 and S6 in DI, II and III. Results In this study, we characterized the gating and kinetic properties of I136V mutant channels in HEK293 cells using whole-cell patch clamp. I136V shifts the voltage-dependence of activation by -5.7 mV, a smaller shift in activation than the other erythromelalgia mutations that have been characterized. I136V also decreases the deactivation rate, and generates larger ramp currents. Conclusion The I136V substitution in NaV1.7 alters channel gating and kinetic properties. Each of these changes may contribute to increased excitability of nociceptive dorsal root ganglion neurons, which underlies pain in erythromelalgia. The smaller shift in voltage-dependence of activation of NaV1.7, compared to the other reported cases of inherited erythromelalgia, may contribute to the later age of onset and slower progression of the symptoms reported in association with this mutation.
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Affiliation(s)
- Xiaoyang Cheng
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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210
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Dib‐Hajj SD, Yang Y, Waxman SG. Chapter 4 Genetics and Molecular Pathophysiology of Nav1.7‐Related Pain Syndromes. ADVANCES IN GENETICS 2008; 63:85-110. [DOI: 10.1016/s0065-2660(08)01004-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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211
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Diss JKJ, Calissano M, Gascoyne D, Djamgoz MBA, Latchman DS. Identification and characterization of the promoter region of the Nav1.7 voltage-gated sodium channel gene (SCN9A). Mol Cell Neurosci 2007; 37:537-47. [PMID: 18249135 DOI: 10.1016/j.mcn.2007.12.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Revised: 11/15/2007] [Accepted: 12/06/2007] [Indexed: 12/19/2022] Open
Abstract
The Nav1.7 sodium channel plays an important role in pain and is also upregulated in prostate cancer. To investigate the mechanisms regulating physiological and pathophysiological Nav1.7 expression we identified the core promoter of this gene (SCN9A) in the human genome. In silico genomic analysis revealed a putative SCN9A 5' non-coding exon approximately 64,000 nucleotides from the translation start site, expression of which commenced at three very closely-positioned transcription initiation sites (TISs), as determined by 5' RACE experiments. The genomic region around these TISs possesses numerous core elements of a TATA-less promoter within a well-defined CpG island. Importantly, it acted as a promoter when inserted upstream of luciferase in a fusion construct. Moreover, the activity of the promoter-luciferase construct ostensibly paralleled endogenous Nav1.7 mRNA levels in vitro, with both increased in a quantitatively and qualitatively similar manner by numerous factors (including NGF, phorbol esters, retinoic acid, and Brn-3a transcription factor over-expression).
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Affiliation(s)
- James K J Diss
- Medical Molecular Biology Unit, Institute of Child Health, University College London, Guilford Street, London WC1N 1EH, UK.
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212
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Dib-Hajj SD, Cummins TR, Black JA, Waxman SG. From genes to pain: Nav1.7 and human pain disorders. Trends Neurosci 2007; 30:555-63. [DOI: 10.1016/j.tins.2007.08.004] [Citation(s) in RCA: 206] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Revised: 06/22/2007] [Accepted: 08/08/2007] [Indexed: 12/19/2022]
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213
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Xie M, Lynch DT, Schools GP, Feustel PJ, Kimelberg HK, Zhou M. Sodium channel currents in rat hippocampal NG2 glia: characterization and contribution to resting membrane potential. Neuroscience 2007; 150:853-62. [PMID: 17981402 DOI: 10.1016/j.neuroscience.2007.09.057] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Revised: 09/20/2007] [Accepted: 10/11/2007] [Indexed: 12/19/2022]
Abstract
We have recently reported that most of NG2 glycoprotein expressing glial cells, or NG2 glia, in rat hippocampus persistently express sodium channel currents (I(Na)) during development, but little is known about its function. We report here that hippocampal NG2 glia recorded in either acute slices or freshly isolated preparations from postnatal days (P) 7-21 rats express low density I(Na) (9.5-15.7 pA/pF) that is characterized by a fast activation and rapid inactivation kinetics with a tetrodotoxin (TTX) IC(50) value of 39.3 nM. The I(Na) expression correlated with a approximately 25 mV more depolarized resting membrane potential (RMP) as compared with non-I(Na)-expressing GLAST(+) astrocytes in situ at the same age. In the presence of the sodium channel blocker TTX (0.1 microM), these depolarized RMPs were negatively shifted by an average of 19 mV and 16 mV for I(Na)-expressing glia recordings from in situ and freshly isolated preparations, respectively. The I(Na) expressing glia actually showed a positive RMP (+12 mV) in the absence of potassium conductance that was inhibited to 0 mV by 0.1 microM TTX. Analysis of the I(Na) activation/inactivation curves yields an I(Na) "window current" at -40+/-20 mV, implying a persistent I(Na) component being active around the NG2 glia RMP of approximately -45 mV. According to the constant-field equation analysis, this active I(Na) component leads to a pNa/pK ratio of 0.14 at RMP which is approximately threefold higher than astrocytes (0.05). These results indicate that a TTX sensitive I(Na) component in NG2 glia contributes significantly to the depolarized NG2 glia RMP in the developing brain.
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Affiliation(s)
- M Xie
- Neural and Vascular Biology, Ordway Research Institute, 150 New Scotland Avenue, Albany, NY 12208, USA
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214
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Cummins TR, Sheets PL, Waxman SG. The roles of sodium channels in nociception: Implications for mechanisms of pain. Pain 2007; 131:243-257. [PMID: 17766042 PMCID: PMC2055547 DOI: 10.1016/j.pain.2007.07.026] [Citation(s) in RCA: 351] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 07/20/2007] [Accepted: 07/27/2007] [Indexed: 11/17/2022]
Abstract
Understanding the role of voltage-gated sodium channels in nociception may provide important insights into pain mechanisms. Voltage-gated sodium channels are critically important for electrogenesis and nerve impulse conduction, and a target for important clinically relevant analgesics such as lidocaine. Furthermore, within the last decade studies have shown that certain sodium channel isoforms are predominantly expressed in peripheral sensory neurons associated with pain sensation, and that the expression and functional properties of voltage-gated sodium channels in peripheral sensory neurons can be dynamically regulated following axonal injury or peripheral inflammation. These data suggest that specific voltage-gated sodium channels may play crucial roles in nociception. Experiments with transgenic mice lines have clearly implicated Na(v)1.7, Na(v)1.8 and Na(v)1.9 in inflammatory, and possibly neuropathic, pain. However the most convincing and perhaps most exciting results regarding the role of voltage-gated sodium channels have come out recently from studies on human inherited disorders of nociception. Point mutations in Na(v)1.7 have been identified in patients with two distinct autosomal dominant severe chronic pain syndromes. Electrophysiological experiments indicate that these pain-associated mutations cause small yet significant changes in the gating properties of voltage-gated sodium channels that are likely to contribute substantially to the development of chronic pain. Equally exciting, recent studies indicate that recessive mutations in Na(v)1.7 that eliminate functional current can result in an apparent complete, and possibly specific, indifference to pain in humans, suggesting that isoform specific blockers could be very effective in treating pain. In this review we will examine what is known about the roles of voltage-gated sodium channels in nociception.
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Affiliation(s)
- Theodore R Cummins
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, 950 West Walnut Street, R2 468, Indianapolis, IN 46202, United States Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, United States Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, United States Rehabilitation Research Center, Veterans Administration Connecticut Healthcare System, West Haven, CT 06516, United States
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215
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Sage D, Salin P, Alcaraz G, Castets F, Giraud P, Crest M, Mazet B, Clerc N. Nav1.7 and Nav1.3 are the only tetrodotoxin-sensitive sodium channels expressed by the adult guinea pig enteric nervous system. J Comp Neurol 2007; 504:363-78. [PMID: 17663442 DOI: 10.1002/cne.21450] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The types of sodium channels that are expressed by neurons shape the rising phase of action potentials and influence patterns of action potential discharge. With regard to the enteric nervous system (ENS), there is uncertainty about which channels are expressed, and in particular it is unknown whether Na(v)1.7 is present. We designed specific probes for the guinea pig Na(v)1.7 alpha subunit as well as for the other tetrodotoxin (TTX)-sensitive alpha subunits (Na(v)1.1, Na(v)1.2, Na(v)1.3, and Na(v)1.6) in order to perform in situ hybridization (ISH) histochemistry on guinea pig myenteric ganglia. We established that only Na(v)1.7 mRNA and Na(v)1.3 mRNA are expressed in these ganglia. The ISH signal for Na(v)1.7 transcripts was found in seemingly all the myenteric neurons. The expression of the Na(v)1.3 alpha subunit was confirmed by immunohistochemistry in a large proportion (62%) of the myenteric neuron population. This population included enteric sensory neurons. Na(v)1.6 immunoreactivity, absent from myenteric neurons, was detected in glial cells only when a high anti-Na(v)1.6 antibody concentration was used. This suggests that the Na(v)1.6 alpha subunit and mRNA are present only at low levels, which is consistent with the fact that no Na(v)1.6 mRNA could be detected in the ENS by ISH. The fact that adult myenteric neurons are endowed with only two TTX-sensitive alpha subunits, namely, Na(v)1.3 and Na(v)1.7, emphasizes the singularity of the ENS. Both these subunits, known to have slow-inactivation kinetics, are well adapted for generating action potentials from slow excitatory postsynaptic potentials, a mode of synaptic transmission that applies to all ENS neuron types.
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Affiliation(s)
- D Sage
- Laboratoire Neurophysiologie Cellulaire, UMR 6150 Centre National de la Recherche Scientifique (CNRS)/Université de la Méditerranée, Institut Fédératif de Recherche Jean Roche, Faculté de Médecine, 13916 Marseille, France
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Patrick Harty T, Waxman SG. Inactivation properties of sodium channel Nav1.8 maintain action potential amplitude in small DRG neurons in the context of depolarization. Mol Pain 2007; 3:12. [PMID: 17540018 PMCID: PMC1892009 DOI: 10.1186/1744-8069-3-12] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Accepted: 05/31/2007] [Indexed: 11/10/2022] Open
Abstract
Background Small neurons of the dorsal root ganglion (DRG) express five of the nine known voltage-gated sodium channels. Each channel has unique biophysical characteristics which determine how it contributes to the generation of action potentials (AP). To better understand how AP amplitude is maintained in nociceptive DRG neurons and their centrally projecting axons, which are subjected to depolarization within the dorsal horn, we investigated the dependence of AP amplitude on membrane potential, and how that dependence is altered by the presence or absence of sodium channel Nav1.8. Results In small neurons cultured from wild type (WT) adult mouse DRG, AP amplitude decreases as the membrane potential is depolarized from -90 mV to -30 mV. The decrease in amplitude is best fit by two Boltzmann equations, having V1/2 values of -73 and -37 mV. These values are similar to the V1/2 values for steady-state fast inactivation of tetrodotoxin-sensitive (TTX-s) sodium channels, and the tetrodotoxin-resistant (TTX-r) Nav1.8 sodium channel, respectively. Addition of TTX eliminates the more hyperpolarized V1/2 component and leads to increasing AP amplitude for holding potentials of -90 to -60 mV. This increase is substantially reduced by the addition of potassium channel blockers. In neurons from Nav1.8(-/-) mice, the voltage-dependent decrease in AP amplitude is characterized by a single Boltzmann equation with a V1/2 value of -55 mV, suggesting a shift in the steady-state fast inactivation properties of TTX-s sodium channels. Transfection of Nav1.8(-/-) DRG neurons with DNA encoding Nav1.8 results in a membrane potential-dependent decrease in AP amplitude that recapitulates WT properties. Conclusion We conclude that the presence of Nav1.8 allows AP amplitude to be maintained in DRG neurons and their centrally projecting axons even when depolarized within the dorsal horn.
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Affiliation(s)
- T Patrick Harty
- Department of Neurology and 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 and 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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Affiliation(s)
- Donald J Kyle
- Discovery Research, Purdue Pharma L.P., 6 Cedar Brook Drive, Cranbury, New Jersey 08512, USA.
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218
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Xiao Y, Li J, Deng M, Dai C, Liang S. Characterization of the excitatory mechanism induced by Jingzhaotoxin-I inhibiting sodium channel inactivation. Toxicon 2007; 50:507-17. [PMID: 17618665 DOI: 10.1016/j.toxicon.2007.04.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2007] [Revised: 04/15/2007] [Accepted: 04/23/2007] [Indexed: 10/23/2022]
Abstract
We have recently isolated a peptide neurotoxin, Jingzhaotoxin-I (JZTX-I), from Chinese tarantula Chilobrachys jingzhao venom that preferentially inhibits cardiac sodium channel inactivation and may define a new subclass of spider sodium channel toxins. In this study, we found that in contrast to other spider sodium channel toxins acting presynaptically rather than postsynaptically, JZTX-I augmented frog end-plate potential amplitudes and caused an increase in both nerve mediated and unmediated muscle twitches. Although JZTX-I does not negatively shift sodium channel activation threshold, an evident increase in muscle fasciculation was detected. In adult rat dorsal root ganglion neurons JZTX-I (1 microM) induced a significant sustained tetrodotoxin-sensitive (TTX-S) current that did not decay completely during 500 ms and was inhibited by 0.1 microM TTX or depolarization due to voltage-dependent acceleration of toxin dissociation. Moreover, JZTX-I decreased closed-state inactivation and increased the rate of recovery of sodium channels, which led to an augmentation in TTX-S ramp currents and decreasing the amount of inactivation in a use-dependant manner. Together, these data suggest that JZTX-I acted both presynaptically and postsynaptically and facilitated the neurotransmitter release by biasing the activities of sodium channels towards open state. These actions are similar to those of scorpion alpha-toxin Lqh II.
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Affiliation(s)
- Yucheng Xiao
- Life Sciences College, Hunan Normal University, Changsha, Hunan 410081, PR China
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219
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Sheets PL, Jackson JO, Waxman SG, Dib-Hajj SD, Cummins TR. A Nav1.7 channel mutation associated with hereditary erythromelalgia contributes to neuronal hyperexcitability and displays reduced lidocaine sensitivity. J Physiol 2007; 581:1019-31. [PMID: 17430993 PMCID: PMC2170829 DOI: 10.1113/jphysiol.2006.127027] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mutations in the TTX-sensitive voltage-gated sodium channel subtype Nav1.7 have been implicated in the painful inherited neuropathy, hereditary erythromelalgia. Hereditary erythromelalgia can be difficult to treat and, although sodium channels are targeted by local anaesthetics such as lidocaine (lignocaine), some patients do not respond to treatment with local anaesthetics. This study examined electrophysiological differences in Nav1.7 caused by a hereditary erythromelalgia mutation (N395K) that lies within the local anaesthetic binding site of the channel. The N395K mutation produced a hyperpolarized voltage dependence of activation, slower kinetics of deactivation, and impaired steady-state slow inactivation. Computer simulations indicate that the shift in activation is the major determinant of the hyperexcitability induced by erythromelalgia mutations in sensory neurons, but that changes in slow inactivation can modulate the overall impact on excitability. This study also investigated lidocaine inhibition of the Nav1.7-N395K channel. We show that the N395K mutation attenuates the inhibitory effects of lidocaine on both resting and inactivated Nav1.7. The IC50 for lidocaine was estimated at 500 microM for inactivated wild-type Nav1.7 and 2.8 mM for inactivated Nav1.7-N395K. The N395K mutation also significantly reduced use-dependent inhibition of lidocaine on Nav1.7 current. In contrast, a different hereditary erythromelalgia mutation (F216S), not located in the local anaesthetic binding site, had no effect on lidocaine inhibition of Nav1.7 current. Our observation of reduced lidocaine inhibition on Nav1.7-N395K shows that the residue N395 is critical for lidocaine binding to Nav1.7 and suggests that the response of individuals with hereditary erythromelalgia to lidocaine treatment may be determined, at least in part, by their specific genotype.
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MESH Headings
- Action Potentials/drug effects
- Anesthetics, Local/metabolism
- Anesthetics, Local/pharmacology
- Anesthetics, Local/therapeutic use
- Binding Sites
- Cell Line
- Computer Simulation
- Dose-Response Relationship, Drug
- Erythromelalgia/drug therapy
- Erythromelalgia/genetics
- Erythromelalgia/metabolism
- Ganglia, Spinal/cytology
- Ganglia, Spinal/drug effects
- Ganglia, Spinal/metabolism
- Humans
- Ion Channel Gating/drug effects
- Kinetics
- Lidocaine/metabolism
- Lidocaine/pharmacology
- Lidocaine/therapeutic use
- Models, Neurological
- Mutation
- NAV1.7 Voltage-Gated Sodium Channel
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Neurons, Afferent/drug effects
- Neurons, Afferent/metabolism
- Sodium Channel Blockers/metabolism
- Sodium Channel Blockers/pharmacology
- Sodium Channel Blockers/therapeutic use
- Sodium Channels/drug effects
- Sodium Channels/genetics
- Sodium Channels/metabolism
- Transfection
- Voltage-Gated Sodium Channel beta-2 Subunit
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Affiliation(s)
- Patrick L Sheets
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, 950 West Walnut St, R2 468, Indianapolis, IN 46202, USA
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Smith JJ, Cummins TR, Alphy S, Blumenthal KM. Molecular Interactions of the Gating Modifier Toxin ProTx-II with Nav1.5. J Biol Chem 2007; 282:12687-97. [PMID: 17339321 DOI: 10.1074/jbc.m610462200] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated Na(+) channels are critical components in the generation of action potentials in excitable cells, but despite numerous structure-function studies on these proteins, their gating mechanism remains unclear. Peptide toxins often modify channel gating, thereby providing a great deal of information about these channels. ProTx-II is a 30-amino acid peptide toxin from the venom of the tarantula, Thrixopelma pruriens, that conforms to the inhibitory cystine knot motif and which modifies activation kinetics of Na(v) and Ca(v), but not K(v), channels. ProTx-II inhibits current by shifting the voltage dependence of activation to more depolarized potentials and, therefore, differs from the classic site 4 toxins that shift voltage dependence of activation in the opposite direction. Despite this difference in functional effects, ProTx-II has been proposed to bind to neurotoxin site 4 because it modifies activation. Here, we investigate the bioactive surface of ProTx-II by alanine-scanning the toxin and analyzing the interactions of each mutant with the cardiac isoform, Na(v)1.5. The active face of the toxin is largely composed of hydrophobic and cationic residues, joining a growing group of predominantly K(v) channel gating modifier toxins that are thought to interact with the lipid environment. In addition, we performed extensive mutagenesis of Na(v)1.5 to locate the receptor site with which ProTx-II interacts. Our data establish that, contrary to prior assumptions, ProTx-II does not bind to the previously characterized neurotoxin site 4, thus making it a novel probe of activation gating in Na(v) channels with potential to shed new light on this process.
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Affiliation(s)
- Jaime J Smith
- Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York 14214, USA
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221
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Waxman SG. Channel, neuronal and clinical function in sodium channelopathies: from genotype to phenotype. Nat Neurosci 2007; 10:405-9. [PMID: 17387329 DOI: 10.1038/nn1857] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
What is the relationship between sodium channel function, neuronal function and clinical status in channelopathies of the nervous system? Given the central role of sodium channels in the generation of neuronal activity, channelopathies involving sodium channels might be expected to cause either enhanced sodium channel function and neuronal hyperexcitability associated with positive clinical manifestations such as seizures, or attenuated channel function and neuronal hypoexcitability associated with negative clinical manifestations such as paralysis. In this article, I review observations showing that changes in neuronal function and clinical status associated with channelopathies are not necessarily predictable solely from the altered physiological properties of the mutated channel itself. I discuss evidence showing that cell background acts as a filter that can strongly influence the effects of ion channel mutations.
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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, Connecticut 06510, USA.
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Abstract
Neuropathic pain remains a large unmet medical need. A number of therapeutic options exist, but efficacy and tolerability are less than satisfactory. Based on animal models and limited data from human patients, the pain and hypersensitivity that characterize neuropathic pain are associated with spontaneous discharges of normally quiescent nociceptors. Sodium channel blockers inhibit this spontaneous activity, reverse nerve injury-induced pain behavior in animals and alleviate neuropathic pain in humans. Several sodium channel subtypes are expressed primarily in sensory neurons and may contribute to the efficacy of sodium channel blockers. In this report, the authors review the current understanding of the role of sodium channels and of specific sodium channel subtypes in neuropathic pain signaling.
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Affiliation(s)
- Birgit T Priest
- Merck Research Laboratories, Department of Ion Channels, Rahway, NJ 07065, USA.
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223
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Temperature dependence of erythromelalgia mutation L858F in sodium channel Nav1.7. Mol Pain 2007; 3:3. [PMID: 17239250 PMCID: PMC1781932 DOI: 10.1186/1744-8069-3-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Accepted: 01/19/2007] [Indexed: 01/05/2023] Open
Abstract
Background The disabling chronic pain syndrome erythromelalgia (also termed erythermalgia) is characterized by attacks of burning pain in the extremities induced by warmth. Pharmacological treatment is often ineffective, but the pain can be alleviated by cooling of the limbs. Inherited erythromelalgia has recently been linked to mutations in the gene SCN9A, which encodes the voltage-gated sodium channel Nav1.7. Nav1.7 is preferentially expressed in most nociceptive DRG neurons and in sympathetic ganglion neurons. It has recently been shown that several disease-causing erythromelalgia mutations alter channel-gating behavior in a manner that increases DRG neuron excitability. Results Here we tested the effects of temperature on gating properties of wild type Nav1.7 and mutant L858F channels. Whole-cell voltage-clamp measurements on wild type or L858F channels expressed in HEK293 cells revealed that cooling decreases current density, slows deactivation and increases ramp currents for both mutant and wild type channels. However, cooling differentially shifts the midpoint of steady-state activation in a depolarizing direction for L858F but not for wild type channels. Conclusion The cooling-dependent shift of the activation midpoint of L858F to more positive potentials brings the threshold of activation of the mutant channels closer to that of wild type Nav1.7 at lower temperatures, and is likely to contribute to the alleviation of painful symptoms upon cooling in affected limbs in patients with this erythromelalgia mutation.
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224
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Cox JJ, Reimann F, Nicholas AK, Thornton G, Roberts E, Springell K, Karbani G, Jafri H, Mannan J, Raashid Y, Al-Gazali L, Hamamy H, Valente EM, Gorman S, Williams R, McHale DP, Wood JN, Gribble FM, Woods CG. An SCN9A channelopathy causes congenital inability to experience pain. Nature 2007; 444:894-8. [PMID: 17167479 PMCID: PMC7212082 DOI: 10.1038/nature05413] [Citation(s) in RCA: 1070] [Impact Index Per Article: 62.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Accepted: 11/03/2006] [Indexed: 12/13/2022]
Abstract
The complete inability to sense pain in an otherwise healthy individual is a very rare phenotype. In three consanguineous families from northern Pakistan, we mapped the condition as an autosomal-recessive trait to chromosome 2q24.3. This region contains the gene SCN9A, encoding the alpha-subunit of the voltage-gated sodium channel, Na(v)1.7, which is strongly expressed in nociceptive neurons. Sequence analysis of SCN9A in affected individuals revealed three distinct homozygous nonsense mutations (S459X, I767X and W897X). We show that these mutations cause loss of function of Na(v)1.7 by co-expression of wild-type or mutant human Na(v)1.7 with sodium channel beta(1) and beta(2) subunits in HEK293 cells. In cells expressing mutant Na(v)1.7, the currents were no greater than background. Our data suggest that SCN9A is an essential and non-redundant requirement for nociception in humans. These findings should stimulate the search for novel analgesics that selectively target this sodium channel subunit.
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Affiliation(s)
- James J Cox
- Department of Medical Genetics, Cambridge Institute for Medical Research, Wellcome/MRC Building, Addenbrooke's Hospital, Cambridge CB2 0XY, UK
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Dick IE, Brochu RM, Purohit Y, Kaczorowski GJ, Martin WJ, Priest BT. Sodium channel blockade may contribute to the analgesic efficacy of antidepressants. THE JOURNAL OF PAIN 2006; 8:315-24. [PMID: 17175203 DOI: 10.1016/j.jpain.2006.10.001] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Revised: 09/11/2006] [Accepted: 10/08/2006] [Indexed: 11/16/2022]
Abstract
UNLABELLED Sodium channel blockers such as lidocaine, lamotrigine, and carbamazepine can be effective in the treatment of neuropathic pain. Though not approved for neuropathic pain indications, tricyclic antidepressants are often considered first-line treatment for conditions such as post-herpetic neuralgia and diabetic neuropathy. Several tricyclic antidepressants have been shown to block peripheral nerve sodium channels, which may contribute to their antihyperalgesic efficacy. In this study, we compared the sodium channel-blocking potency of a number of antidepressants, including tricyclic antidepressants and selective serotonin reuptake inhibitors. All compounds tested inhibited Na(V)1.7 in a state- and use-dependent manner, with affinities for the inactivated state ranging from 0.24 micromol/L for amitriptyline to 11.6 micromol/L for zimelidine. The tricyclic antidepressants were more potent blockers of Na(V)1.7. Moreover, IC(50)s for block of the inactivated state for amitriptyline, nortriptyline, imipramine, desipramine, and maprotiline were in the range of therapeutic plasma concentrations for both the treatment of depression as well as neuropathic pain. By contrast, fluoxetine, paroxetine, mianserine, and zimelidine had IC(50)s for Na(V)1.7 outside their therapeutic concentration ranges and generally were not efficacious against post-herpetic neuralgia or diabetic neuropathy. These results suggest that block of peripheral nerve sodium channels may contribute to the antihyperalgesic efficacy of certain antidepressants. PERSPECTIVE Tricyclic antidepressants are often considered first-line treatment for neuropathic pain. Some tricyclic antidepressants block sodium channels, which may contribute to their antihyperalgesic efficacy. In the current study, we compared the potency of peripheral sodium channel blockade for several tricyclic antidepressants and selective serotonin reuptake inhibitors with their therapeutic efficacy.
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Affiliation(s)
- Ivy E Dick
- Department of Ion Channels, Merck Research Laboratories, Rahway, New Jersey 07065-0900, USA
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227
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Rush AM, Cummins TR, Waxman SG. Multiple sodium channels and their roles in electrogenesis within dorsal root ganglion neurons. J Physiol 2006; 579:1-14. [PMID: 17158175 PMCID: PMC2075388 DOI: 10.1113/jphysiol.2006.121483] [Citation(s) in RCA: 315] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Dorsal root ganglion neurons express an array of sodium channel isoforms allowing precise control of excitability. An increasing body of literature indicates that regulation of firing behaviour in these cells is linked to their patterns of expression of specific sodium channel isoforms, which have been discovered to possess distinct biophysical characteristics. The pattern of expression of sodium channels differs in different subclasses of DRG neurons and is not fixed but, on the contrary, changes in response to a variety of disease insults. Moreover, modulation of channels by their environment has been found to play an important role in the response of these neurons to stimuli. In this review we illustrate how excitability can be finely tuned to provide contrasting firing templates in different subclasses of DRG neurons by selective deployment of various sodium channel isoforms, by plasticity of expression of these proteins, and by interactions of these sodium channel isoforms with each other and with other modulatory molecules.
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228
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Lampert A, Dib-Hajj SD, Tyrrell L, Waxman SG. Size Matters: Erythromelalgia Mutation S241T in Nav1.7 Alters Channel Gating. J Biol Chem 2006; 281:36029-35. [PMID: 17008310 DOI: 10.1074/jbc.m607637200] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Nav1.7 sodium channel is preferentially expressed in most nociceptive dorsal root ganglion neurons and in sympathetic neurons. Inherited erythromelalgia (IEM, also known as erythermalgia), an autosomal dominant neuropathy characterized by burning pain in the extremities in response to mild warmth, has been linked to mutations in Nav1.7. Recently, a substitution of Ser-241 by threonine (S241T) in the domain I S4-S5 linker of Nav1.7 was identified in a family with IEM. To investigate the possible causative role of this mutation in the pathophysiology of IEM, we used whole-cell voltage-clamp analysis to study the effects of S241T on Nav1.7 gating in HEK293 cells. We found a hyperpolarizing shift of activation midpoint by 8.4 mV, an accelerated time to peak, slowing of deactivation, and an increase in the current in response to small, slow depolarizations. Additionally, S241T produced an enhancement of slow inactivation, shifting the midpoint by -12.3 mV. Because serine and threonine have similar biochemical properties, the S241T substitution suggested that the size of the side chain at this position affected channel gating. To test this hypothesis, we investigated the effect of S241A and S241L substitutions on the gating properties of Nav1.7. Although S241A did not alter the properties of the channel, S241L mimicked the effects of S241T. We conclude that the linker between S4 and S5 in domain I of Nav1.7 modulates gating of this channel, and that a larger side chain at position 241 interferes with its gating mechanisms.
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Affiliation(s)
- Angelika Lampert
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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229
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Wooltorton JRA, Gaboyard S, Hurley KM, Price SD, Garcia JL, Zhong M, Lysakowski A, Eatock RA. Developmental changes in two voltage-dependent sodium currents in utricular hair cells. J Neurophysiol 2006; 97:1684-704. [PMID: 17065252 DOI: 10.1152/jn.00649.2006] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Two kinds of sodium current (I(Na)) have been separately reported in hair cells of the immature rodent utricle, a vestibular organ. We show that rat utricular hair cells express one or the other current depending on age (between postnatal days 0 and 22, P0-P22), hair cell type (I, II, or immature), and epithelial zone (striola vs. extrastriola). The properties of these two currents, or a mix, can account for descriptions of I(Na) in hair cells from other reports. The patterns of Na channel expression during development suggest a role in establishing the distinct synapses of vestibular hair cells of different type and epithelial zone. All type I hair cells expressed I(Na,1), a TTX-insensitive current with a very negative voltage range of inactivation (midpoint: -94 mV). I(Na,2) was TTX sensitive and had less negative voltage ranges of activation and inactivation (inactivation midpoint: -72 mV). I(Na,1) dominated in the striola at all ages, but current density fell by two-thirds after the first postnatal week. I(Na,2) was expressed by 60% of hair cells in the extrastriola in the first week, then disappeared. In the third week, all type I cells and about half of type II cells had I(Na,1); the remaining cells lacked sodium current. I(Na,1) is probably carried by Na(V)1.5 subunits based on biophysical and pharmacological properties, mRNA expression, and immunoreactivity. Na(V)1.5 was also localized to calyx endings on type I hair cells. Several TTX-sensitive subunits are candidates for I(Na,2).
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Abstract
Our knowledge of the ion channels, receptors and signalling mechanisms involved in pain pathophysiology, and which specific channels play a role in subtypes of pain such as neuropathic and inflammatory pain, has expanded considerably in recent years. It is now clear that in the neuropathic state the expression of certain channels is modified, and that these changes underlie the plasticity of responses that occur to generate inappropriate pain signals from normally trivial inputs. Pain is modulated by a subset of the voltage-gated sodium channels, including Nav1.3, Nav1.7, Nav1.8 and Nav1.9. These isoforms display unique expression patterns within specific tissues, and are either up- or down-regulated upon injury to the nervous system. Here we describe our current understanding of the roles of sodium channels in pain and nociceptive information processing, with a particular emphasis on neuropathic pain and drugs useful for the treatment of neuropathic pain that act through mechanisms involving block of sodium channels. One of the future challenges in the development of novel sodium channel blockers is to design and synthesise isoform-selective channel inhibitors. This should provide substantial benefits over existing pain treatments.
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Affiliation(s)
- Marc Rogers
- Xention Ltd., Iconix Park, Pampisford, Cambridge CB2 4EF, United Kingdom
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231
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232
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Rush AM, Wittmack EK, Tyrrell L, Black JA, Dib-Hajj SD, Waxman SG. Differential modulation of sodium channel Na(v)1.6 by two members of the fibroblast growth factor homologous factor 2 subfamily. Eur J Neurosci 2006; 23:2551-62. [PMID: 16817858 DOI: 10.1111/j.1460-9568.2006.04789.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
FHF2A and FHF2B are two members of the fibroblast growth factor homologous factor 2 (FHF2) subfamily with distinct N termini. Using a generic antibody and electrophysiological methods, we previously showed that FHF2 is expressed in hippocampus and dorsal root ganglion (DRG) neurons and is colocalized with sodium channel Na(v)1.6 at sensory but not motor nodes of Ranvier, and that FHF2B associates with Na(v)1.6, causing an increase in current density and a small depolarizing shift in availability of channels. Using immunolabeling of adult rat tissue, we demonstrate that FHF2A is present within DRG but not in hippocampal or cerebellar neurons or at nodes of Ranvier in sciatic nerve, and that Na(v)1.6 and FHF2A are colocalized in nonmyelinated fibers. We also show that FHF2A binds directly to Na(v)1.6, and that the two proteins coimmunoprecipitate from transfected HEK293 cells. Because Na(v)1.6 has been associated with rapid firing rates, we examined the possible effects of FHF2B and the sister isoform, FHF2A, on electrophysiological properties of this channel in the DRG-derived ND7/23 cell line. We show that FHF2B inhibits accumulation of inactivation in response to trains of stimulation at high frequencies. In marked contrast, FHF2A causes an accumulation of inactivated channels at all frequencies tested due to a slowing of recovery from inactivation. Thus different FHF2 subfamily members have different functional effects on Na(v)1.6 and are differentially distributed in DRG neurons and their axons. This suggests that FHF2A and FHF2B may selectively alter firing behaviour of specific neuronal compartments via differential modulation of Na(v)1.6.
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Affiliation(s)
- Anthony M Rush
- Department of Neurology, Yale School of Medicine, New Haven, CT 06510, USA
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Rush AM, Dib-Hajj SD, Liu S, Cummins TR, Black JA, Waxman SG. A single sodium channel mutation produces hyper- or hypoexcitability in different types of neurons. Proc Natl Acad Sci U S A 2006; 103:8245-50. [PMID: 16702558 PMCID: PMC1472458 DOI: 10.1073/pnas.0602813103] [Citation(s) in RCA: 299] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Disease-producing mutations of ion channels are usually characterized as producing hyperexcitability or hypoexcitability. We show here that a single mutation can produce hyperexcitability in one neuronal cell type and hypoexcitability in another neuronal cell type. We studied the functional effects of a mutation of sodium channel Nav1.7 associated with a neuropathic pain syndrome, erythermalgia, within sensory and sympathetic ganglion neurons, two cell types where Nav1.7 is normally expressed. Although this mutation depolarizes resting membrane potential in both types of neurons, it renders sensory neurons hyperexcitable and sympathetic neurons hypoexcitable. The selective presence, in sensory but not sympathetic neurons, of the Nav1.8 channel, which remains available for activation at depolarized membrane potentials, is a major determinant of these opposing effects. These results provide a molecular basis for the sympathetic dysfunction that has been observed in erythermalgia. Moreover, these findings show that a single ion channel mutation can produce opposing phenotypes (hyperexcitability or hypoexcitability) in the different cell types in which the channel is expressed.
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Affiliation(s)
- Anthony M. Rush
- *Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare Center, West Haven, CT 06516; and
| | - Sulayman D. Dib-Hajj
- *Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare Center, West Haven, CT 06516; and
| | - Shujun Liu
- *Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare Center, West Haven, CT 06516; and
| | - Theodore R. Cummins
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Joel A. Black
- *Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare Center, West Haven, CT 06516; and
| | - Stephen G. Waxman
- *Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510
- Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare Center, West Haven, CT 06516; and
- To whom correspondence should be addressed at:
Department of Neurology, LCI 707, Yale Medical School, P.O. Box 208018, New Haven, CT 06520. E-mail:
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Han C, Rush AM, Dib-Hajj SD, Li S, Xu Z, Wang Y, Tyrrell L, Wang X, Yang Y, Waxman SG. Sporadic onset of erythermalgia: A gain-of-function mutation in Nav1.7. Ann Neurol 2006; 59:553-8. [PMID: 16392115 DOI: 10.1002/ana.20776] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Inherited erythermalgia (erythromelalgia) is an autosomal dominant disorder in which patients experience severe burning pain in the extremities, in response to mild thermal stimuli and exercise. Although mutations in sodium channel Na(v)1.7 have been shown to underlie erythermalgia in several multigeneration families with the disease that have been investigated to date, the molecular basis of erythermalgia in sporadic cases is enigmatic. We investigated the role of Na(v)1.7 in a sporadic case of erythermalgia in a Chinese family. METHODS Genomic DNA from patients and their asymptomatic family members were sequenced to identify mutations in Na(v)1.7. Whole-cell patch clamp analysis was used to characterize biophysical properties of wild-type and mutant Na(v)1.7 channels in mammalian cells. RESULTS A single amino acid substitution in the DIIS4-S5 linker of Na(v)1.7 was present in two children whose parents were asymptomatic. The asymptomatic father was genetically mosaic for the mutation. This mutation produces a hyperpolarizing shift in channel activation and an increase in amplitude of the response to slow, small depolarizations. INTERPRETATION Founder mutations in Na(v)1.7, which can confer hyperexcitability on peripheral sensory neurons, can underlie sporadic erythermalgia.
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Affiliation(s)
- Chongyang Han
- Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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235
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Chapter 2 History of Ion Channels in the Pain Sensory System. CURRENT TOPICS IN MEMBRANES 2006. [DOI: 10.1016/s1063-5823(06)57001-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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236
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Priestley T, Hunter JC. Voltage-gated sodium channels as molecular targets for neuropathic pain. Drug Dev Res 2006. [DOI: 10.1002/ddr.20100] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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237
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Diss JKJ, Stewart D, Pani F, Foster CS, Walker MM, Patel A, Djamgoz MBA. A potential novel marker for human prostate cancer: voltage-gated sodium channel expression in vivo. Prostate Cancer Prostatic Dis 2005; 8:266-73. [PMID: 16088330 DOI: 10.1038/sj.pcan.4500796] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Functional expression of voltage-gated sodium channel alpha-subunits (VGSCalphas), specifically Nav1.7, is associated with strong metastatic potential in prostate cancer (CaP) in vitro. Furthermore, VGSC activity in vitro directly potentiates processes integral to metastasis. To investigate VGSCalpha expression in CaP in vivo, immunohistochemistry and real-time PCR were performed on human prostate biopsies (n>20). VGSCalpha immunostaining was evident in prostatic tissues and markedly stronger in CaP vs non-CaP patients. Importantly, RT-PCRs identified Nav1.7 as the VGSCalpha most strikingly upregulated (approximately 20-fold) in CaP, and the resultant receiver-operating characteristics curve demonstrated high diagnostic efficacy for the disease. It is concluded that VGSCalpha expression increases significantly in CaP in vivo and that Nav1.7 is a potential functional diagnostic marker.
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Affiliation(s)
- J K J Diss
- Department of Biological Sciences, Neuroscience Solutions to Cancer Research Group, Imperial College London, South Kensington Campus, London, UK
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238
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Leffler A, Herzog RI, Dib-Hajj SD, Waxman SG, Cummins TR. Pharmacological properties of neuronal TTX-resistant sodium channels and the role of a critical serine pore residue. Pflugers Arch 2005; 451:454-63. [PMID: 15981012 DOI: 10.1007/s00424-005-1463-x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Accepted: 04/29/2005] [Indexed: 02/02/2023]
Abstract
Voltage-gated sodium channels can be characterized by their sensitivity to inhibitors. Na(v)1.5 is sensitive to block by cadmium and extracellular QX-314, but relatively insensitive to tetrodotoxin and saxitoxin. Na(v)1.4 is tetrodotoxin- and saxitoxin-sensitive but resistant to cadmium and extracellular QX-314. Na(v)1.8 and Na(v)1.9 generate slowly inactivating (I(TTXr-Slow)) and persistent (I(TTXr-Per)) currents in sensory neurons that are tetrodotoxin-resistant. Tetrodotoxin sensitivity is largely determined by the identity of a single residue; tyrosine 401 in Na(v)1.4, cysteine 374 in Na(v)1.5 and serine 356 and 355 in Na(v)1.8 and Na(v)1.9. We asked whether Na(v)1.8 and Na(v)1.9 share other pharmacological properties as a result of this serine residue. I(TTXr-Slow) and I(TTXr-Per) were saxitoxin-resistant and resistant to internal QX-314. I(TTXr-Slow) was also resistant to external QX-314 and displayed a approximately fourfold higher sensitivity than I(TTXr-Per) to cadmium. The impact of the serine residue was investigated by replacing tyrosine 401 in Na(v)1.4 with serine (Y401S) or cysteine (Y401C). Both mutants were resistant to tetrodotoxin and saxitoxin. Whereas Na(v)1.4-Y401C displayed an increased sensitivity to cadmium and extracellular QX-314, the serine substitution did not alter the sensitivity of Na(v)1.4 to cadmium or QX-314. Our data indicates that while the serine residue determines the sensitivity of I(TTXr-Slow) and I(TTXr-Per) to tetrodotoxin and saxitoxin, it does not determine their insensitivity to QX-314 or their differential sensitivities to cadmium.
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Affiliation(s)
- Andreas Leffler
- Klinik für Anästhesiologie, Friedrich-Alexander-Universität Erlangen-Nuremberg, Krankenhausstr. 12, 91054 Erlangen, Germany
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239
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Dib-Hajj SD, Rush AM, Cummins TR, Hisama FM, Novella S, Tyrrell L, Marshall L, Waxman SG. Gain-of-function mutation in Nav1.7 in familial erythromelalgia induces bursting of sensory neurons. Brain 2005; 128:1847-54. [PMID: 15958509 DOI: 10.1093/brain/awh514] [Citation(s) in RCA: 344] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Erythromelalgia is an autosomal dominant disorder characterized by burning pain in response to warm stimuli or moderate exercise. We describe a novel mutation in a family with erythromelalgia in SCN9A, the gene that encodes the Na(v)1.7 sodium channel. Na(v)1.7 produces threshold currents and is selectively expressed within sensory neurons including nociceptors. We demonstrate that this mutation, which produces a hyperpolarizing shift in activation and a depolarizing shift in steady-state inactivation, lowers thresholds for single action potentials and high frequency firing in dorsal root ganglion neurons. Erythromelalgia is the first inherited pain disorder in which it is possible to link a mutation with an abnormality in ion channel function and with altered firing of pain signalling neurons.
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Affiliation(s)
- S D Dib-Hajj
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, CT 06510, USA
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240
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Cummins TR, Dib-Hajj SD, Herzog RI, Waxman SG. Nav
1.6 channels generate resurgent sodium currents in spinal sensory neurons. FEBS Lett 2005; 579:2166-70. [PMID: 15811336 DOI: 10.1016/j.febslet.2005.03.009] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Revised: 02/15/2005] [Accepted: 03/02/2005] [Indexed: 11/30/2022]
Abstract
The Na(v)1.6 voltage-gated sodium channel has been implicated in the generation of resurgent currents in cerebellar Purkinje neurons. Our data show that resurgent sodium currents are produced by some large diameter dorsal root ganglion (DRG) neurons from wild-type mice, but not from Na(v)1.6-null mice; small DRG neurons do not produce resurgent currents. Many, but not all, DRG neurons transfected with Na(v)1.6 produce resurgent currents. These results demonstrate for the first time the intrinsic ability of Na(v)1.6 to produce a resurgent current, and also show that cell background is critical in permitting the generation of these currents.
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Affiliation(s)
- Theodore R Cummins
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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241
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Rush AM, Dib-Hajj SD, Waxman SG. Electrophysiological properties of two axonal sodium channels, Nav1.2 and Nav1.6, expressed in mouse spinal sensory neurones. J Physiol 2005; 564:803-15. [PMID: 15760941 PMCID: PMC1464456 DOI: 10.1113/jphysiol.2005.083089] [Citation(s) in RCA: 200] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Sodium channels Na(v)1.2 and Na(v)1.6 are both normally expressed along premyelinated and myelinated axons at different stages of maturation and are also expressed in a subset of demyelinated axons, where coexpression of Na(v)1.6 together with the Na(+)/Ca(2+) exchanger is associated with axonal injury. It has been difficult to distinguish the currents produced by Na(v)1.2 and Na(v)1.6 in native neurones, and previous studies have not compared these channels within neuronal expression systems. In this study, we have characterized and directly compared Na(v)1.2 and Na(v)1.6 in a mammalian neuronal cell background and demonstrate differences in their properties that may affect neuronal behaviour. The Na(v)1.2 channel displays more depolarized activation and availability properties that may permit conduction of action potentials, even with depolarization. However, Na(v)1.2 channels show a greater accumulation of inactivation at higher frequencies of stimulation (20-100 Hz) than Na(v)1.6 and thus are likely to generate lower frequencies of firing. Na(v)1.6 channels produce a larger persistent current that may play a role in triggering reverse Na(+)/Ca(2+) exchange, which can injure demyelinated axons where Na(v)1.6 and the Na(+)/Ca(2+) exchanger are colocalized, while selective expression of Na(v)1.2 may support action potential electrogenesis, at least at lower frequencies, while producing a smaller persistent current.
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Affiliation(s)
- Anthony M Rush
- Department of Neurology, Center for Neuroscience and Regeneration Research, Yale School of Medicine, LCI 707, 333 Cedar Street, New Haven, CT 06510, USA
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242
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Waxman SG, Dib-Hajj SD. Erythromelalgia: A hereditary pain syndrome enters the molecular era. Ann Neurol 2005; 57:785-8. [PMID: 15929046 DOI: 10.1002/ana.20511] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In contrast with acquired pain syndromes, molecular substrates for hereditary pain disorders have been poorly understood. Familial erythromelalgia (Weir Mitchell's disease), also known as primary erythermalgia, is an autosomal dominant disorder characterized by burning pain in the extremities in response to warm stimuli or moderate exercise. The cause of this disorder has been enigmatic, and treatment has been empirical and not very effective. Recent studies, however, have shown that familial erythromelalgia is a channelopathy caused by mutations in the gene encoding the Na(v)1.7 sodium channel which lead to altered channel function. Selective expression of Na(v)1.7 within dorsal root ganglion neurons including nociceptors (in which this channel is targeted to sensory terminals, close to impulse trigger zones) and within sympathetic ganglion neurons explains why patients experience pain but do not suffer from seizures or other manifestations of altered excitability within central nervous system neurons. Erythromelalgia is the first human disorder in which it has been possible to associate an ion channel mutation with chronic neuropathic pain. Identification of mutations within a peripheral neuron-specific sodium channel suggests the possibility of rational therapies that target the affected channel. Moreover, because some other pain syndromes, including acquired disorders, involve altered sodium channel function, erythromelalgia may emerge as a model disease that holds more general lessons about the molecular neurobiology of chronic pain.
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Affiliation(s)
- Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA.
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243
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Abstract
Mibefradil is a T-type Ca2+ channel antagonist with reported cross-reactivity with other classes of ion channels, including K+, Cl-, and Na+ channels. Using whole-cell voltage clamp, we examined mibefradil block of four Na+ channel isoforms expressed in human embryonic kidney cells: Nav1.5 (cardiac), Nav1.4 (skeletal muscle), Nav1.2 (brain), and Nav1.7 (peripheral nerve). Mibefradil blocked Nav1.5 in a use/frequency-dependent manner, indicating preferential binding to states visited during depolarization. Mibefradil blocked currents of all Na+ channel isoforms with similar affinity and a dependence on holding potential, and drug off-rate was slowed at depolarized potentials (k(off) was 0.024/s at -130 mV and 0.007/s at -100 mV for Nav1.5). We further probed the interaction of mibefradil with inactivated Nav1.5 channels. Neither the degree nor the time course of block was dependent on the stimulus duration, which dramatically changed the residency time of channels in the fast-inactivated state. In addition, inhibiting the binding of the fast inactivation lid (Nav1.5 ICM + MTSET) did not alter mibefradil block, confirming that the drug does not preferentially interact with the fast-inactivated state. We also tested whether mibefradil interacted with slow-inactivated state(s). When selectively applied to channels after inducing slow inactivation with a 60-s pulse to -10 mV, mibefradil (1 microM) produced 45% fractional block in Nav1.5 and greater block (88%) in an isoform (Nav1.4) that slow-inactivates more completely. Our results suggest that mibefradil blocks Na+ channels in a state-dependent manner that does not depend on fast inactivation but probably involves interaction with one or more slow-inactivated state(s).
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Affiliation(s)
- Megan M McNulty
- Department of Neurobiology, University of Chicago, Illinois, USA
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244
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Hoffman JF, Dodson A, Wickrema A, Dib-Hajj SD. Tetrodotoxin-sensitive Na+ channels and muscarinic and purinergic receptors identified in human erythroid progenitor cells and red blood cell ghosts. Proc Natl Acad Sci U S A 2004; 101:12370-4. [PMID: 15292511 PMCID: PMC514482 DOI: 10.1073/pnas.0404228101] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
This article concerns the identification of different types of voltage-gated Na(+) channels and of muscarinic and purinergic receptors that are expressed in human erythroid precursor cells and red cell ghosts. We analyzed, by RT-PCR, RNA that was extracted from purified and synchronously growing human erythroid progenitor cells, differentiating from erythroblasts to reticulocytes in 7 to 14 days. These extracts were free of white cell and platelet contamination. Two types of voltage-gated, tetrodotoxin-sensitive Na(+) channels were found. These were Na(v)1.4 and Na(v)1.7, the former known to be present in skeletal muscle and the latter in peripheral nerve. By using a pan Na(+) channel antibody and Western blotting, an immunoreactive channel was detected in ghosts of human red blood cells, consistent with the expression of these two channels. The transcripts for four of the five known subtypes of muscarinic receptors were also identified, including subtypes M2, M3, M4, and M5, whereas subtype M1 was not found. Expression was also detected for the purinergic type receptors P2X(1), P2X(4), P2X(7), and P2Y(1) whereas types P2Y(2), P2Y(4), and P2Y(6) were not found. We also searched for but did not find transcripts for hBNP-1, a type 1b human brain sodium phosphate cotransporter, and cystic fibrosis transmembrane conductance regulator (CFTR). Implications regarding the presence of these different types of channels and receptors in human red blood cells and their functional significance are discussed.
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Affiliation(s)
- Joseph F Hoffman
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520, USA
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245
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Hong S, Morrow TJ, Paulson PE, Isom LL, Wiley JW. Early painful diabetic neuropathy is associated with differential changes in tetrodotoxin-sensitive and -resistant sodium channels in dorsal root ganglion neurons in the rat. J Biol Chem 2004; 279:29341-50. [PMID: 15123645 PMCID: PMC1828032 DOI: 10.1074/jbc.m404167200] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Diabetic neuropathy is a common form of peripheral neuropathy, yet the mechanisms responsible for pain in this disease are poorly understood. Alterations in the expression and function of voltage-gated tetrodotoxin-resistant (TTX-R) sodium channels have been implicated in animal models of neuropathic pain, including models of diabetic neuropathy. We investigated the expression and function of TTX-sensitive (TTX-S) and TTX-R sodium channels in dorsal root ganglion (DRG) neurons and the responses to thermal hyperalgesia and mechanical allodynia in streptozotocin-treated rats between 4-8 weeks after onset of diabetes. Diabetic rats demonstrated a significant reduction in the threshold for escape from innocuous mechanical pressure (allodynia) and a reduction in the latency to withdrawal from a noxious thermal stimulus (hyperalgesia). Both TTX-S and TTX-R sodium currents increased significantly in small DRG neurons isolated from diabetic rats. The voltage-dependent activation and steady-state inactivation curves for these currents were shifted negatively. TTX-S currents induced by fast or slow voltage ramps increased markedly in neurons from diabetic rats. Immunoblots and immunofluorescence staining demonstrated significant increases in the expression of Na(v)1.3 (TTX-S) and Na(v) 1.7 (TTX-S) and decreases in the expression of Na(v) 1.6 (TTX-S) and Na(v)1.8 (TTX-R) in diabetic rats. The level of serine/threonine phosphorylation of Na(v) 1.6 and In Na(v)1.8 increased in response to diabetes. addition, increased tyrosine phosphorylation of Na(v)1.6 and Na(v)1.7 was observed in DRGs from diabetic rats. These results suggest that both TTX-S and TTX-R sodium channels play important roles and that differential phosphorylation of sodium channels involving both serine/threonine and tyrosine sites contributes to painful diabetic neuropathy.
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Affiliation(s)
- Shuangsong Hong
- Department of Internal Medicine and Pharmacology, University of Michigan, Ann Arbor, Michigan 48109, USA
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246
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Gould HJ, England JD, Soignier RD, Nolan P, Minor LD, Liu ZP, Levinson SR, Paul D. Ibuprofen blocks changes in nav 1.7 and 1.8 sodium channels associated with complete freund's adjuvant–induced inflammation in rat. THE JOURNAL OF PAIN 2004; 5:270-80. [PMID: 15219259 DOI: 10.1016/j.jpain.2004.04.005] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2004] [Revised: 04/19/2004] [Accepted: 04/27/2004] [Indexed: 01/04/2023]
Abstract
UNLABELLED Although nerve growth factor plays a role in augmenting sodium channel expression in small dorsal root ganglion (DRG) cells, the cytochemical mediators responsible for enhanced expression in large DRG neurons are unknown. To narrow the search for mediators involved in the increased production of sodium channels in large DRG neurons, we examined the effect of cyclooxygenase inhibition on sodium channel production during inflammation. Thirty minutes before the subcutaneous injection of complete Freund's adjuvant (CFA), rats received ibuprofen (nonselective, cyclooxygenase inhibitor), NS-398 (selective, cyclooxygenase inhibitor), or vehicle. Withdrawal thresholds from thermal and mechanical stimulation were measured before and immediately after CFA injection and at selected hourly intervals after injection for the next 24 hours. Sodium channel up-regulation was then examined in DRG by using site-specific, anti-sodium channel antibodies, Na(v) 1.7 and 1.8. Both ibuprofen and NS-398 provided analgesia during the second phase of inflammatory hyperalgesia that begins 3 hours after CFA injection. The up-regulation, predominantly of Na(v) 1.7 and minimally of Na(v) 1.8 channels, seen in vehicle-treated rats was suppressed by both drugs at 24 hours after injection. By 72 hours after injection, no difference in labeling between the drug- and vehicle-treated animals was observed. Sodium channel labeling in large DRG neurons returned to baseline between 1 and 2 weeks after CFA injection, whereas small cell labeling persisted. The cytochemical signal for sodium channel up-regulation in the large DRG cells that most closely correlates with inflammatory hyperalgesia is mediated at least in part through products of the cyclooxygenase pathway. PERSPECTIVE Expression of sodium channels in dorsal root ganglia increases dramatically during inflammation. The increase in sodium channels is thought to enhance neuronal excitability and to play a role in hyperalgesia and wound vigilance during healing. We provide evidence that prostaglandins play a role in signaling channel augmentation.
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Affiliation(s)
- Harry J Gould
- Department of Neurology, Louisiana State University Health Sciences Center, 533 Bolivar Street, Room 325, New Orleans, LA 70112, USA.
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247
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Black JA, Liu S, Tanaka M, Cummins TR, Waxman SG. Changes in the expression of tetrodotoxin-sensitive sodium channels within dorsal root ganglia neurons in inflammatory pain. Pain 2004; 108:237-247. [PMID: 15030943 DOI: 10.1016/j.pain.2003.12.035] [Citation(s) in RCA: 295] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2003] [Revised: 12/16/2003] [Accepted: 12/22/2003] [Indexed: 12/21/2022]
Abstract
Nociceptive neurons within dorsal root ganglia (DRG) express multiple voltage-gated sodium channels, of which the tetrodotoxin-resistant (TTX-R) channel Na(v)1.8 has been suggested to play a major role in inflammatory pain. Previous work has shown that acute administration of inflammatory mediators, including prostaglandin E2 (PGE2), serotonin, and adenosine, modulates TTX-R current in DRG neurons, producing increased current amplitude and a hyperpolarizing shift of its activation curve. In addition, 4 days following injection of carrageenan into the hind paw, an established model of inflammatory pain, Na(v)1.8 mRNA and slowly-inactivating TTX-R current are increased in DRG neurons projecting to the affected paw. In the present study, the expression of sodium channels Na(v)1.1-Na(v)1.9 in small (< or = 25 micromdiameter) DRG neurons was examined with in situ hybridization, immunocytochemistry, Western blot and whole-cell patch-clamp methods following carrageenan injection into the peripheral projection fields of these cells. The results demonstrate that, following carrageenan injection, there is increased expression of TTX-S channels Na(v)1.3 and Na(v)1.7 and a parallel increase in TTX-S currents. The previously reported upregulation of Na(v)1.8 and slowly-inactivating TTX-R current is not accompanied by upregulation of mRNA or protein for Na(v)1.9, an additional TTX-R channel that is expressed in some DRG neurons. These observations demonstrate that chronic inflammation results in an upregulation in the expression of both TTX-S and TTX-R sodium channels, and suggest that TTX-S sodium channels may also contribute, at least in part, to pain associated with inflammation.
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Affiliation(s)
- Joel A Black
- Department of Neurology and Paralyzed Veterans of America, Eastern Paralyzed Veterans Association Neuroscience Research Center, Yale University School of Medicine, New Haven, CT 06510, USA Rehabilitation Research Center, VA Connecticut Healthcare System, 950 Campbell Ave, West Haven, CT, 06516 USA Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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248
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Kiss T. Evidence for a persistent Na-conductance in identified command neurones of the snail, Helix pomatia. Brain Res 2003; 989:16-25. [PMID: 14519507 DOI: 10.1016/s0006-8993(03)03316-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Neurones RPa3 and LPa3 were identified as 'command' neurones in the Helix parietal ganglia. The physiological role of these cells is the integration of sensory information before triggering withdrawal behaviour. Properties of the Na-channels are poorly understood in these neurones which produce Na(+)-dependent action potentials in Ca(2+)-free solution. Our aim was to describe the kinetic properties and TTX-sensitivity of the Na-channels of these cells, and to provide evidence for the existence of a persistent inward sodium current (I(NaP)) in them. Two-microelectrode voltage- and patch-clamp techniques were used on isolated or semi-isolated neurones. The kinetics and potential dependence of the transient inward sodium current (I(NaT)) agreed well with those obtained on other molluscan neurones. We concluded that I(NaT) present in these neurones is slow and TTX-resistant (k(D)=8 microM of TTX) and has two components with different rates of inactivation. In addition, the presence of an I(NaP) component was revealed. We showed that I(NaP) is neither an artifact nor the contribution of a Ca-channel or a 'window' current. With slow voltage ramp pulses I(NaP) could be activated and separated from I(NaT). Like I(NaT) it appeared to be TTX-resistant and Na-dependent. I(NaP) was upregulated by increased pH (8.0) and decreased by elevated extracellular Mg(2+) concentration parallel with the I(NaT). Our results suggest that I(NaP) originates from the same set of sodium channels that underlie I(NaT).
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Affiliation(s)
- Tibor Kiss
- Department of Zoology, Balaton Limnological Research Institute of the Hungarian Academy of Sciences, Furdotelepi u. 3, H-3287, Tihany, Hungary.
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249
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Herzog RI, Liu C, Waxman SG, Cummins TR. Calmodulin binds to the C terminus of sodium channels Nav1.4 and Nav1.6 and differentially modulates their functional properties. J Neurosci 2003; 23:8261-70. [PMID: 12967988 PMCID: PMC6740705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023] Open
Abstract
Modulation of voltage-gated sodium channels (VGSC) can have a major impact on cell excitability. Analysis of calmodulin (CaM) binding to GST-fusion proteins containing the C-terminal domains of Nav1.1-Nav1.9 indicates that some of the tetrodotoxin-sensitive VGSC isoforms, including NaV1.4 and NaV1.6, are able to bind CaM in a calcium-independent manner. Here we demonstrate that association with CaM is important for functional expression of NaV1.4 and NaV1.6 VGSCs. Disrupting the interaction between CaM and the C terminus of NaV1.4 and NaV1.6 channels reduced current amplitude by 99 and 62%, respectively. Overexpression of CaM increased the current generated by Nav1.4 and Nav1.6 C-terminal mutant constructs that exhibited intermediate current densities and intermediate binding affinities for CaM, demonstrating that this effect on current density was directly dependent on the ability of the C terminus to bind CaM. In addition to the effects on current density, calmodulin also was able to modulate the inactivation kinetics of Nav1.6, but not Nav1.4, currents in a calcium-dependent manner. Our data demonstrate that CaM can regulate the properties of VGSCs via calcium-dependent and calcium-independent mechanisms and suggest that modulation of neuronal sodium channels may play a role in calcium-dependent neuronal plasticity.
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Affiliation(s)
- Raimund I Herzog
- Department of Neurology and Paralyzed Veterans of America/Eastern Paralyzed Veterans Association Neuroscience Research Center, Yale School of Medicine, New Haven, Connecticut 06510, USA
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Loftis JL, King DD, Colbert CM. Kinase-dependent loss of Na+ channel slow-inactivation in rat CA1 hippocampal pyramidal cell dendrites after brief exposure to convulsants. Eur J Neurosci 2003; 18:1029-32. [PMID: 12956702 DOI: 10.1046/j.1460-9568.2003.02832.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Na+ channels in the dendrites of rat CA1 pyramidal neurons display a profound activity-dependent inactivation, termed slow inactivation, that limits excitability in the dendrites even at low physiological rates of firing. The magnitude of this slow inactivation is powerfully modulated by a protein kinase C-dependent process. Because activation of kinases is a rapid and common feature of a number of seizure models, we hypothesized that a loss of slow inactivation of Na+ channels might exacerbate other changes in excitability. Thus, we observed the effects of a brief (5 min) chemical convulsant treatment on Na+ currents and action potentials in hippocampal slices. We found that slow inactivation decreased significantly and remained decreased for at least 30 min after return to control conditions. Pretreatment with either chelerythrine, a protein kinase C inhibitor, or U0126, a mitogen-activated protein kinase/extracellular signal regulated kinase kinase (MEK) inhibitor, blocked this reduction of slow inactivation. These results demonstrate that a brief period of hyperexcitability leads to a rapid, protein kinase-dependent loss of slow inactivation of Na+ channels that would contribute to and perhaps prolong the hyperexcitable state.
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Affiliation(s)
- Jordan L Loftis
- Department of Biology and Biochemistry, University of Houston, 4800 Calhoun Road, Houston, TX 77204-5513, USA
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