Structure-based assessment of disease-related mutations in human voltage-gated sodium channels

Abstract

Voltage-gated sodium (Na_v) channels are essential for the rapid upstroke of action potentials and the propagation of electrical signals in nerves and muscles. Defects of Na_v channels are associated with a variety of channelopathies. More than 1000 disease-related mutations have been identified in Na_v channels, with Na_v1.1 and Na_v1.5 each harboring more than 400 mutations. Na_v channels represent major targets for a wide array of neurotoxins and drugs. Atomic structures of Na_v channels are required to understand their function and disease mechanisms. The recently determined atomic structure of the rabbit voltage-gated calcium (Ca_v) channel Ca_v1.1 provides a template for homology-based structural modeling of the evolutionarily related Na_v channels. In this Resource article, we summarized all the reported disease-related mutations in human Na_v channels, generated a homologous model of human Na_v1.7, and structurally mapped disease-associated mutations. Before the determination of structures of human Na_v channels, the analysis presented here serves as the base framework for mechanistic investigation of Na_v channelopathies and for potential structure-based drug discovery.

Graphical abstract

Keywords

Na_v channels / channelopathy / Na_v1.7 / structure modeling / pain

INTRODUCTION

Voltage-gated sodium (Na_v) channels are essential for the rapid depolarization phase of action potential and play a key role in the electrical signaling in most excitable cells. Structurally, Na_v channels are composed of one α subunit and one or more β subunits. The α subunit contains two functionally distinct structural entities, namely, the voltage-sensing domains (VSDs) and the ion-conducting pore domain (Catterall, 2012b, 2014). The β subunits, which bind to α subunit covalently or non-covalently, modulate membrane trafficking, voltage dependence, and channel gating kinetics (Catterall, 2012b, 2014). In mammals, Na_v channels have nine known α members distributed in different excitable tissues. Specifically, Na_v1.1, Na_v1.2, Na_v1.3, and Na_v1.6 are the primary sodium channels in central nervous system (CNS), Na_v1.4 is primarily expressed in skeletal muscle, Na_v1.5 is mainly expressed in heart, and Na_v1.7, Na_v1.8, and Na_v1.9 are mainly distributed in peripheral nervous system (Plummer and Meisler, 1999; Goldin, 2001; Catterall et al., 2005).

All α subunits share nearly identical structure topology—a canonical voltage-gated ion channel fold with four homologous repeats, each containing six transmembrane segments S1–S6. Specifically, S5–S6 segments form the pore domain that conducts selective sodium filtering, while S1–S4 segments constitute the voltage-sensing domain that controls voltage-dependent gating (Catterall, 2000). The voltage sensors in the VSDs are featured by a number of positively charged amino acids (arginine or lysine) located at every third position in the S4 segment. Upon membrane depolarization, movements of these charged residues in the S4 segment are coupled to the opening of the pore domain and the subsequent influx of sodium ions across cell membrane. The pore domain is structurally organized with a four-fold pseudo-symmetry. The pore (P) loops, which are supported by the P1 helix (corresponding to the P helix in potassium channel) and P2 helix between S5 and S6 segments in each repeat, constitute the selectivity filter (SF) (Corry and Thomas, 2012). Four amino acid residues (aspartate, glutamate, lysine, and alanine, DEKA, in repeats I, II, III, and IV, respectively) in the P loops are crucial for sodium selectivity. Mutating these residues to glutamates confers calcium selectivity, suggesting that the side chains of these amino acids are likely to interact directly with the sodium ions to determine ion selectivity (Heinemann et al., 1992; Sun et al., 1997).

Na_v channels inactivate rapidly. A cluster of hydrophobic amino acids (isoleucine, phenylalanine, methionine, and threonine), namely the IFMT motif, located in the cytosolic regions of domain III and domain IV, are required for rapid inactivation. This is demonstrated by the fact that rapid inactivation could be achieved by titrating small peptides containing the IFMT motif (Vassilev et al., 1988; West et al., 1992).

Sodium channelopathies are a group of diseases caused by defective Na_v channels, either, in most cases, of congenital nature or acquired nature (Tables 1, 2, 3, 4, 5, 6, 7, 8, 9, 10) (George, 2005; Catterall, 2012a; Kim, 2014). For example, Na_v1.1 is primarily expressed in the soma of neuronal cells in the CNS, and mutations of Na_v1.1 cause GEFS+2 (generalized epilepsy with febrile seizures plus 2)(Catterall et al., 2010). Moreover, mutations of Na_v1.1 are also the main causes of EIEE6 (epileptic encephalopathy, early infantile, 6) and ICEGTC (intractable childhood epilepsy with generalized tonic-clonic seizures) (Escayg and Goldin, 2010). Na_v1.5 is the major sodium channel expressed in heart. Na_v1.5 mutations may lead to various cardiac diseases such as LQT3 (long QT syndrome 3), BRGDA1(Brugada syndrome 1), and SSS1 (sick sinus syndrome 1)(Olson et al., 2005; Song and Shou, 2012; Veerman et al., 2015). Na_v1.7 is preferentially expressed in the sympathetic neurons, olfactory epithelium, and dorsal root ganglion sensory neurons, and plays a cardinal role in pain transmission (Djouhri et al., 2003; Dib-Hajj et al., 2013). Gain-of-function mutations of Na_v1.7 are implicated in two distinct paroxysmal pain syndromes—IEM (primary erythermalgia) and PEPD (paroxysmal extreme pain disorder), while loss-of-function mutations of Na_v1.7 inflict people with CIP (indifference to pain, congenital, autosomal recessive)(Lampert et al., 2010; Dib-Hajj et al., 2013). In all, Na_v channel mutations play a central role in the pathophysiology of sodium channelopathies. Pharmacologic modulation of Na_v channels may thereby represent a viable therapeutic approach for the treatment of many neurological disorders such as epilepsy, arrhythmia, and pain.

Despite significant advancement in the understanding of Na_v channel functions and their relevance to diseases, structural characterization of mammalian Na_v channels at atomic level has been challenging, partly due to the substantial technical hurdles in producing mammalian Na_v channel proteins in sufficient amount with acceptable purity. The two published bacterial Na_v channel crystal structures, Na_vAb (Payandeh et al., 2011) and Na_vRh (Zhang et al., 2012), in their full-length have greatly improved our understanding of how those channels conduct and select sodium ions on a structural basis. This is further enhanced by the recently published cryo-electron microscopy (cryo-EM) structure of the rabbit voltage-gated calcium (Ca_v) channel Ca_v1.1 (Wu et al., 2015; Wu et al., 2016), which, given the significant similarities between Ca_v and Na_v channels, provides an excellent base model for studying the structure and function of the mammalian Na_v channels in lieu of the elusive Na_v channel structure (Wu et al., 2015; Wu et al., 2016). In this Resource article, we have built a structure model of the human sodium channel Na_v1.7 based on the Ca_v1.1 cryo-EM structure (PDB code: 5GJV). Disease-related mutations of various Na_v channels are systematically mapped onto this Na_v1.7 structural model. As expected, most mutations are located in the VSDs and the pore domain, which corroborate the functional disturbance associated with the various conditions. The human Na_v1.7 structure model may also provide a useful tool for the structure-based design of drugs that are able to therapeutically target the Na_v channels.

STRUCTURE MODEL OF HUMAN SODIUM CHANNEL NA_V1.7

Homology models of the mammalian Na_v channels have been previously constructed based on the crystal structures of the eukaryotic potassium channels or the prokaryotic sodium channels (Tikhonov and Zhorov, 2012; Yang et al., 2012). However, the relevance of such models has been in question, since the eukaryotic sodium channels are known to be heterotetrameric while the prokaryotic sodium channels and the potassium channels are of homotetrameric nature.

We sought to build a homology-based structural model for human Na_v1.7 because of the tremendous interest in drug development targeting this channel. The sequence identity and similarity between human Na_v1.7 and rabbit Ca_v1.1 are 21 and 35%, respectively (Please refer to the online Supplementary Fig. 2 of Wu et al., 2016). Importantly, the key amino acids within the VSDs and the pore domains are highly conserved (Wu et al., 2015; Wu et al., 2016). The cryo-EM structure of rabbit Ca_v1.1 was then used as the template for homology modeling of human Na_v1.7. The primary sequence of human Na_v1.7 was aligned with rabbit Ca_v1.1 in MOE with manual adjustment when necessary. The structure model of human Na_v1.7 was created with the Homology Model module in MOE using the GB/VI scoring function with AMBER12: EHT force field (MOE, 2016).

The human Na_v1.7 model structure resembles the structure of rCa_v1.1 in general (Fig. 1A). However, the model exhibits pronounced differences from the calcium channel and bacterial sodium channels particularly in selectivity filter. The SF of Na_v1.7 consists of four different amino acid residues DEKA (Fig. 1B). In contrast, the Ca_v1.1 SF is constituted by four repeated essential glutamic acids, EEEE, while Na_vAb and Na_vRh contain TLESWS or TLSSWE in each protomer, respectively. This human Na_v1.7 structure model represents the first one-chain sodium channel model with asymmetric repeats and is expected to shed new light on the mammalian sodium channel functions.

MAPPING OF DISEASE-RELEVANT MUTATIONS ONTO THE NA_V1.7 STRUCTURE MODEL

Human Na_v1.7 sodium channel is preferentially expressed in the sensory neurons of dorsal root ganglia and sympathetic ganglia neurons, particularly within the nociceptors, which is essential for perceiving pain (Djouhri et al., 2003; Dib-Hajj et al., 2013). To date, about 60 mutations of Na_v1.7 have been found to cause human pain syndromes including IEM, PEPD, CIP, SFN (small fiber neuropathy), DS (Dravet syndrome), and FEB (febrile seizure) (Fig. 2 and Table 1). We mapped all the reported Na_v1.7 mutations onto this Na_v1.7 structure model (Fig. 2). Nineteen out of 22 IEM mutations are located in the highly conserved regions of VSDs and the pore domain except for the Q10R, P610T, and G616R mutations (Fig. 2). Electrophysiology study showed that IEM mutations cause a prominent shift of the activation voltage toward a more negative region or delay deactivation, which results in neuron hyperexcitability (Choi et al., 2006; Lampert et al., 2006; Choi et al., 2009; Lampert et al., 2010). For example, mutation of A1643 within the S5 segment of domain IV to glycine (A1643G) generates a significant hyperpolarizing shift (Yang et al., 2016). Our structural analysis shows that only two IEM mutations F216S and L834R are located in the S4 positively charged segment that is directly responsible for transmembrane voltage sensing and channel activation. How other IEM mutations influence voltage sensing and channel functions is yet to be elucidated.

The PEPD mutations are mostly characterized (nine out of 11) within the S4 segment, S4-S5 linker region, and the cytosolic regions of domain III and domain IV of Na_v1.7 except for R185H and R1007C (Fig. 2A and Table 1). Specifically, I1472T, F1473V, and T1475I are within the IFMT motif (Fig. 2A), indicating that they may disturb channel inactivation. Indeed, IFMT mutations usually impair fast inactivation with consequently persistent currents (Fertleman et al., 2006). The V1309D, V1309F, and V1310F mutations are located in the S4-S5 linker region of domain III and they have been shown to cause moderate destabilization of fast inactivation (Jarecki et al., 2008). The G1618R mutation, located within the S4 segment of domain IV, impairs inactivation and retains a persistent current compared to the wild-type(WT) channel (Choi et al., 2011), while another domain IV S4 segment mutation, L1623P, significantly increases ramp current and shortens recovery time from inactivation(Suter et al., 2015). Moreover, electrophysiology study showed that M1638K mutation (within the S5 segment of domain IV) generates faster recovery from inactivation than the WTchannel, producing greater currents and reducing the threshold with increased number of action potentials(Fertleman et al., 2006; Dib-Hajj et al., 2008). Another PEPD mutation, A1643E, also located in the S5 segment of domain IV, impedes channel full inactivation, which results in persistent inward currents (Estacion et al., 2008).

The CIP patients, characterized by lack of nociceptive perception, are mostly inflicted by Na_v1.7 nonsense mutations, which result in premature protein truncations and inability to produce functional sodium channels. Only three mutations of Na_v1.7, namely R907Q, A1247E, and W1786R, have been reported to be associated with CIP (Fig. 2 and Table 1). Diseases such as DS, SFN, and FEB are also known to be caused by Na_v1.7 mutations (Fig. 2 and Table 1). For example, all eight SFN mutations have been characterized. Specifically, I228M, I731K, I750V, and M1543I mutations impair slow inactivation, D623N impedes slow and fast inactivation, while R185H, M943L, and V1002L mutations enhance resurgent currents (Faber et al., 2012a). On the other hand, Na_v1.7 mutations that are associated with DS (nine mutations) and FEB (six mutations) have not been well characterized.

MAPPING OF OTHER HUMAN SODIUM CHANNEL DISEASE-RELATED MUTATIONS ONTO THE NA_V1.7 STRUCTURE MODEL

Members of the human Na_v channel family share high sequence similarity and mutations of these Na_v channels are known to cause a vast variety of channelopathies. In order to better understand the role of those mutations in disturbing normal channel functions on a structural level, we mapped the disease-related mutations of other human Na_v channels onto the Na_v1.7 structure model based on the sequence alignment reported in Wu et al., 2016(Fig. 3).

Among all the nine Na_v channels, Na_v1.1 and Na_v1.5 have the largest numbers of reported mutations (more than 400 each) (Fig. 3A and 3E), while Na_v1.3, Na_v1.8, and Na_v1.9 have the least numbers (less than 10 each) (Fig. 3C, 3H, and 3I). Notably, mutations in Na_v1.1, Na_v1.2, Na_v1.3, and Na_v1.6 mainly cause epilepsies; those in Na_v1.4 are related to myopathies; in Na_v1.5 result in cardiac channelopathies; and in Na_v1.7, Na_v1.8, and Na_v1.9 are associated with pain-related diseases (Fig. 3 and Tables 1, 2, 3, 4, 5, 6, 7, 8, 9, 10). Mapping of all Na_v channel mutations onto the Na_v1.7 structure model revealed that more than 80% of mutations are located in the VSDs and pore domains (Fig. 4A and 4B). Notably, disease-causing mutations are somewhat equally distributed in all four Na_v channel domains, which account for more than 20 sodium channelopathies (Fig. 4C). Furthermore, mutations are also distributed in various regions of the pore domains, suggesting that they may disturb Na_v channel functions by altering sodium ion selectivity and conductivity (Fig. 4D).

Na_v1.2 mutations are largely associated with various epilepsy diseases, including BFIS3 (seizures, benign familial infantile 3), EIEE11 (epileptic encephalopathy, early infantile, 11), and DS (Fig. 3B and Table 3). More than 30 Na_v1.2 mutations have been discovered and some of them are now functionally characterized. Interestingly, electrophysiological studies showed that Na_v1.2 mutations can either be loss-of-function(R1319Q and L1330F) or gain-of-function (M252V, V261M, L1563V, and Y1579C) (Misra et al., 2008; Liao et al., 2010; Lauxmann et al., 2013). It is noted that BFIS3 mutations in Na_v1.2 create less pronounced changes in the activation and inactivation potentials than the EIEE11 mutations (Shi et al., 2012).

Only six missense mutations of Na_v1.3 have so far been identified in patients with cryptogenic partial epilepsy(Fig. 3C and Table 4). Five of them, namely K354Q, R357Q, D815N, E1160K, and M1372V, have been characterized, all of which are gain-of-function mutations, consistent with the neuronal hyperexcitability phenotype (Estacion et al., 2010; Vanoye et al., 2014).

Na_v1.4 is essential for controlling the muscle action potential and consequently crucial for skeletal muscle contraction. Mutations of Na_v1.4 are related with various neuromuscular disorders including PMC (paramyotonia congenita of von Eulenburg), HOKPP2 (periodic paralysis hypokalemic 2), HYPP (periodic paralysis hyperkalemic), NKPP (periodic paralysis normokalemic), MYOSCN4A(myotonia SCN4A-related), and CMS16 (myasthenic syndrome, congenital, 16) (Fig. 3D and Table 5). Different disease- causing mutations alter the Na_v1.4 channel function through distinct mechanisms. For example, CMS16 mutations R104H, P382T, and C1209F completely abolish the Na_v1.4 channel’s ability to conduct sodium ion, while other mutations such as M203K, R225W, and D1069N cause reduced action potential amplitude, leading to impaired channel function (Zaharieva et al., 2016). Compared to the WT channel, a CMS16 voltage sensor mutant R1457H requires longer hyperpolarization to recover which results in increased fast inactivation (Arnold et al., 2015). On the other hand, a HOKPP2 mutation R1135H (the third arginine in the domain III voltage sensor) exhibits increased depolarization, suggesting that R1135H mutation be gain-of-function(Groome et al., 2014). A MYOSCN4A mutation I582V shows a hyperpolarizing shift of 6 mV, indicating the nature of this mutation be also gain-of-function (Corrochano et al., 2014).

Na_v1.6 is one of the sodium channels expressed in human brain and mutations of Na_v1.6 cause EIEE13(epileptic encephalopathy, early infantile, 13) (Fig. 3F and Table 7). More than 40 Na_v1.6 mutations have been discovered since 2012 (Fig. 3F and Table 7), and seven of them have been studied in the functional assays. Specifically, five Na_v1.6 mutations, namely T767I, N984K, T1716I, N1768D, and R1872W/R1872Q/R1872L, are characterized as gain-of-function, which cause hyperpolarizing shift of inactivation voltage or increased persistent current (Veeramah et al., 2012; Estacion et al., 2014; Wagnon et al., 2016), while the other two mutations, R223G and G1451S, are loss-of-function(de Kovel et al., 2014; Blanchard et al., 2015).

Five Na_v1.8 mutations are associated with SFN, a condition that is clinically characterized by autonomic dysfunction and burning pain in the distal extremities (Fig. 3H and Table 8). Electrophysiology study has shown that Na_v1.8 mutations, specifically L554P, A1304T, G1662S, and I1706V, accelerate inactivation recovery and enhance activation, which result in hyperexcitability (Faber et al., 2012b; Huang et al., 2013; Han et al., 2014). However, another SFN Na_v1.8 mutation M650K causes reduced excitability of C fibers (Kist et al., 2016).

FEPS3 (episodic pain syndrome, familial, 3) and HSAN7(neuropathy, hereditary sensory and autonomic, 7) are thought to be caused by the nine missense gain-of-function mutations of Na_v1.9 (Fig. 3I and Table 9). Specifically, compared to the WT channel, R225C and A808G mutations induce hyperexcitability of the DRG neurons (Zhang et al., 2013), G699R enhances activation (Han et al., 2015), L811P significantly increases current density (Leipold et al., 2013), L1158P enhances spontaneous firing (Huang et al., 2014), and V1184A alters the channel voltage dependence that results in channel opening in response to hyperpolarized potentials (Leipold et al., 2015).

DISEASE-RELATED MUTATIONS IN SODIUM CHANNELS NA_V1.1 AND NA_V1.5

Mutations of Na_v1.1 are associated with several neurological disorders including GEFS+2, EIEE6, ICEGTC, FHM3 (migraine, familial hemiplegic, 3), and FEB3A (febrile seizures, familial, 3A) (Table 2 and Table 10). More than 400 mutations of Na_v1.1 have been identified, approximately 10% account for GEFS+2 while 80% for EIEE6 (Fig. 5A and Table 2). By mapping the Na_v1.1-related mutations to the Na_v1.7 structure model, we identified that most mutations are located in the VSDs and the pore domain (Fig. 5A). For example, mutations of the four positively charged residues, R1639G, R1642S, R1645Q, and R1648C, are present in the domain IV S4 segment (Table 2), suggesting that these EIEE6 mutations may alter the voltage sensing behavior of the channel. In addition, it is noteworthy that Na_v1.1 mutations can be either loss-of-function or gain-of-function (Catterall et al., 2010; Escayg and Goldin, 2010). For example, two GEFS+2 mutations W1204R and R1648H increase the level of persistent current through gain-of-function (Lossin et al., 2002), while the loss-of-function M145T mutation in FEB3A decreases 60% of the current density (Mantegazza et al., 2005).

Na_v1.5 is the primary sodium channel in the heart and is essential for the cardiac action potential initiation. More than 400 Na_v1.5 mutations have been discovered and they are implicated in a wide variety of cardiac diseases—including PFHB1A (progressive familial heart block 1A), LQT3, BRGDA1, SSS1, VF1 (familial paroxysmal ventricular fibrillation 1), SIDS (sudden infant death syndrome), ATRST1(atrial standstill 1), CMD1E (cardiomyopathy, dilated 1E), ATFB10 (atrial fibrillation, familial, 10), and MEPPC (multifocal ectopic Purkinje-related premature contractions)(Fig. 5B and Table 6). By mapping all the Na_v1.5 mutations onto the Na_v1.7 structure model, it shows that most mutations are located in the transmembrane regions of the channel, suggesting that these mutations might disturb voltage sensing or sodium conduction (Fig. 5B). Furthermore, about 50% of the Na_v1.5 mutations account for BRGDA1, while 30% for LQT3. Similar to the case of Na_v1.1, mutations in Na_v1.5 can be either loss-of-function or gain-of-function. For example, loss-of-function mutations are associated with BRGDA1, CMD1E, SSS1, and ATFB10 (Tan et al., 2001; Smits et al., 2005; Makiyama et al., 2008; Laurent et al., 2012), while gain-of-function mutations of Na_v1.5 are responsible for LQT3 (Remme et al., 2006), CMD1E, and ATFB10 (Olson et al., 2005), and most recently MEPPC (Swan et al., 2014).

CONCLUDING REMARKS

The Na_v family of sodium channels are important drug targets for the pharmaceutical industry. However, no atomic structure of any mammalian Na_v channels is currently available, preventing the establishment of an in-depth structure-function relationship for this important group of sodium channels and application of structure-based approach to rationally design compounds that are able to modulate the functions of those Na_v channels in a disease relevant manner. Using the recently published cryo-EM structure of a rabbit Ca_v channel Ca_v1.1, we established an atomic level heterotetrameric structure model for the human Na_v channel Na_v1.7. Disease-related mutations of Na_v1.7 and other members of the Na_v family, which are largely responsible for many neurological disorders like epilepsies, pains, and myopathies, are mapped onto the structure model. Taken together the available functional data, we attempted to establish a rudimentary structure-function relationship for human Na_v1.7 and other members of the Na_v channel family. It is noticeable that sodium channelopathies can be attributed to both loss-of-function and gain-of-function mutations.

However, we must realize that the current Na_v1.7 structural model has its limitation and the atomic resolution mammalian Na_v channel structure is urgently needed. In recent years, cryo-EM technology is becoming a mainstream technology for structural biology, which is able to potentially overcome the significant technical hurdles in producing challenging proteins such as mammalian Na_v channels in sufficient quality and the necessity of crystallization for structural elucidation. Detailed mechanisms of how the Na_v channels sense voltage changes and conduct sodium ions can only be answered when such atomic resolution structures become available. We hope the Na_v1.7 structure model presented here is a temporary surrogate to help understand the Na_v channel functions, particularly those relevant to the various neurological diseases, at atomic level, and contributes to the structure-based rational design of the next generation Na_v channel modulators.

SUMMARY OF DISEASE-RELATED MUTATIONS FOR SODIUM CHANNELS

Most of the Na_v channel disease-related mutations are extracted from the UNIPROT websites:

http://www.uniprot.org/uniprot/P35498 (Na_v1.1);

http://www.uniprot.org/uniprot/Q99250 (Na_v1.2);

http://www.uniprot.org/uniprot/P35499 (Na_v1.4);

http://www.uniprot.org/uniprot/Q14524 (Na_v1.5);

http://www.uniprot.org/uniprot/Q9UQD0 (Na_v1.6);

http://www.uniprot.org/uniprot/Q15858 (Na_v1.7);

http://www.uniprot.org/uniprot/Q9Y5Y9 (Na_v1.8);

http://www.uniprot.org/uniprot/Q9UI33 (Na_v1.9).

In the UNIPROT websites, there are no mutations described for Na_v1.3. During literatures searching, we found that six mutations of Na_v1.3 are associated with cryptogenic partial epilepsy. Except for the present mutations in the UNIPROT websites, we found additional mutations of Na_v channels in literatures. All mutations are summarized in Tables 1, 2, 3, 4, 5, 6, 7, 8, 9. However, we recognize that our summary may not contain all Na_v channel disease-related mutations owing to abundant literatures reporting Na_v channel disease-related mutations and increasing volume of work describing new findings.

References

[1] Arnold WD, Feldman DH, Ramirez S, He L, Kassar D, Quick A, Klassen TL, Lara M, Nguyen J, Kissel JT et al (2015) Defective fast inactivation recovery of Nav 1.4 in congenital myasthenic syndrome. Ann Neurol 77:840–850

[2] Blanchard MG, Willemsen MH, Walker JB, Dib-Hajj SD, Waxman SG, Jongmans MC, Kleefstra T, van de Warrenburg BP, Praamstra P, Nicolai J et al (2015) De novo gain-of-function and loss-of-function mutations of SCN8A in patients with intellectual disabilities and epilepsy. J Med Genet 52:330–337

[3] Catterall WA (2000) From ionic currents to molecular mechanisms: the structure and function of voltage-gated sodium channels. Neuron 26:13–25

[4] Catterall WA (2012a) Sodium channel mutations and epilepsy. In: Noebels JL, Avoli M, Rogawski MA, Olsen RW, Delgado-Escueta AV (eds) Jasper’s basic mechanisms of the epilepsies. National Center for Biotechnology Information (US), Bethesda

[5] Catterall WA (2012b) Voltage-gated sodium channels at 60: structure, function and pathophysiology. J Physiol 590:2577–2589

[6] Catterall WA (2014) Structure and function of voltage-gated sodium channels at atomic resolution. Exp Physiol 99:35–51

[7] Catterall WA, Goldin AL, Waxman SG (2005) International Union of Pharmacology. XLVII. Nomenclature and structure-function relationships of voltage-gated sodium channels. Pharmacol Rev 57:397–409

[8] Catterall WA, Kalume F, Oakley JC (2010) NaV1.1 channels and epilepsy. J Physiol 588:1849–1859

[9] Choi JS, Dib-Hajj SD, Waxman SG (2006) Inherited erythermalgia: limb pain from an S4 charge-neutral Na channelopathy. Neurology 67:1563–1567

[10] Choi JS, Zhang L, Dib-Hajj SD, Han C, Tyrrell L, Lin Z, Wang X, Yang Y, Waxman SG (2009) Mexiletine-responsive erythromelalgia due to a new Na(v)1.7 mutation showing use-dependent current fall-off. Exp Neurol 216:383–389

[11] Choi JS, Boralevi F, Brissaud O, Sanchez-Martin J, Te Morsche RH, Dib-Hajj SD, Drenth JP, Waxman SG (2011) Paroxysmal extreme pain disorder: a molecular lesion of peripheral neurons. Nat Rev Neurol 7:51–55

[12] Corrochano S, Mannikko R, Joyce PI, McGoldrick P, Wettstein J, Lassi G, Raja Rayan DL, Blanco G, Quinn C, Liavas A et al(2014) Novel mutations in human and mouse SCN4A implicate AMPK in myotonia and periodic paralysis. Brain 137:3171–3185

[13] Corry B, Thomas M (2012) Mechanism of ion permeation and selectivity in a voltage gated sodium channel. J Am Chem Soc 134:1840–1846

[14] de Kovel CG, Meisler MH, Brilstra EH, van Berkestijn FM, van’t Slot R, van Lieshout S, Nijman IJ, O’Brien JE, Hammer MF, Estacion M et al (2014) Characterization of a de novo SCN8A mutation in a patient with epileptic encephalopathy. Epilepsy Res 108:1511–1518

[15] Dib-Hajj SD, Estacion M, Jarecki BW, Tyrrell L, Fischer TZ, Lawden M, Cummins TR, Waxman SG (2008) Paroxysmal extreme pain disorder M1627K mutation in human Na_v1.7 renders DRG neurons hyperexcitable. Mol Pain 4:37

[16] Dib-Hajj SD, Yang Y, Black JA, Waxman SG (2013) The Na(V)1.7 sodium channel: from molecule to man. Nat Rev Neurosci 14:49–62

[17] Djouhri L, Newton R, Levinson SR, Berry CM, Carruthers B, Lawson SN (2003) Sensory and electrophysiological properties of guinea-pig sensory neurones expressing Nav 1.7 (PN1) Na+ channel alpha subunit protein. J Physiol 546:565–576

[18] Escayg A, Goldin AL (2010) Sodium channel SCN1A and epilepsy: mutations and mechanisms. Epilepsia 51:1650–1658

[19] Estacion M, Dib-Hajj SD, Benke PJ, Te Morsche RH, Eastman EM, Macala LJ, Drenth JP, Waxman SG (2008) NaV1.7 gain-of-function mutations as a continuum: A1632E displays physiological changes associated with erythromelalgia and paroxysmal extreme pain disorder mutations and produces symptoms of both disorders. J Neurosci 28:11079–11088

[20] Estacion M, Gasser A, Dib-Hajj SD, Waxman SG (2010) A sodium channel mutation linked to epilepsy increases ramp and persistent current of Nav1.3 and induces hyperexcitability in hippocampal neurons. Exp Neurol 224:362–368

[21] Estacion M, O’Brien JE, Conravey A, Hammer MF, Waxman SG, Dib-Hajj SD, Meisler MH (2014) A novel de novo mutation of SCN8A (Nav1.6) with enhanced channel activation in a child with epileptic encephalopathy. Neurobiol Dis 69:117–123

[22] Faber CG, Hoeijmakers JG, Ahn HS, Cheng X, Han C, Choi JS, Estacion M, Lauria G, Vanhoutte EK, Gerrits MM et al (2012a) Gain of function Nanu1.7 mutations in idiopathic small fiber neuropathy. Ann Neurol 71:26–39

[23] Faber CG, Lauria G, Merkies IS, Cheng X, Han C, Ahn HS, Persson AK, Hoeijmakers JG, Gerrits MM, Pierro T et al (2012b) Gain-of-function Nav1.8 mutations in painful neuropathy. Proc Natl Acad Sci USA 109:19444–19449

[24] Fertleman CR, Baker MD, Parker KA, Moffatt S, Elmslie FV, Abrahamsen B, Ostman J, Klugbauer N, Wood JN, Gardiner RM et al (2006) SCN9A mutations in paroxysmal extreme pain disorder: allelic variants underlie distinct channel defects and phenotypes. Neuron 52:767–774

[25] George AL (2005) Inherited disorders of voltage-gated sodium channels. J Clin Invest 115:1990–1999

[26] Goldin AL (2001) Resurgence of sodium channel research. Annu Rev Physiol 63:871–894

[27] Groome JR, Lehmann-Horn F, Fan C, Wolf M, Winston V, Merlini L, Jurkat-Rott K (2014) NaV1.4 mutations cause hypokalaemic periodic paralysis by disrupting IIIS4 movement during recovery. Brain 137:998–1008

[28] Han C, Vasylyev D, Macala LJ, Gerrits MM, Hoeijmakers JG, Bekelaar KJ, Dib-Hajj SD, Faber CG, Merkies IS, Waxman SG(2014) The G1662S NaV1.8 mutation in small fibre neuropathy: impaired inactivation underlying DRG neuron hyperexcitability. J Neurol Neurosurg Psychiatry 85:499–505

[29] Han C, Yang Y, de Greef BT, Hoeijmakers JG, Gerrits MM, Verhamme C, Qu J, Lauria G, Merkies IS, Faber CG et al(2015) The domain II S4-S5 linker in Nav1.9: a missense mutation enhances activation, impairs fast inactivation, and produces human painful neuropathy. Neuromol Med 17:158–169

[30] Heinemann SH, Terlau H, Stuhmer W, Imoto K, Numa S (1992) Calcium channel characteristics conferred on the sodium channel by single mutations. Nature 356:441–443

[31] Huang J, Yang Y, Zhao P, Gerrits MM, Hoeijmakers JG, Bekelaar K, Merkies IS, Faber CG, Dib-Hajj SD, Waxman SG (2013) Small-fiber neuropathy Nav1.8 mutation shifts activation to hyperpolarized potentials and increases excitability of dorsal root ganglion neurons. J Neurosci 33:14087–14097

[32] Huang J, Han C, Estacion M, Vasylyev D, Hoeijmakers JG, Gerrits MM, Tyrrell L, Lauria G, Faber CG, Dib-Hajj SD et al (2014) Gain-of-function mutations in sodium channel Na(v)1.9 in painful neuropathy. Brain 137:1627–1642

[33] Jarecki BW, Sheets PL, Jackson JO, Cummins TR (2008) Paroxysmal extreme pain disorder mutations within the D3/S4-S5 linker of Nav1.7 cause moderate destabilization of fast inactivation. J Physiol 586:4137–4153

[34] Kim JB (2014) Channelopathies. Korean J Pediatr 57:1–18

[35] Kist AM, Sagafos D, Rush AM, Neacsu C, Eberhardt E, Schmidt R, Lunden LK, Orstavik K, Kaluza L, Meents J et al (2016) SCN10A mutation in a patient with erythromelalgia enhances C-fiber activity dependent slowing. PLoS One 11:e0161789

[36] Lampert A, Dib-Hajj SD, Tyrrell L, Waxman SG (2006) Size matters: erythromelalgia mutation S241T in Nav1.7 alters channel gating. J Biol Chem 281:36029–36035

[37] Lampert A, O’Reilly AO, Reeh P, Leffler A (2010) Sodium channelopathies and pain. Pflugers Arch 460:249–263

[38] Laurent G, Saal S, Amarouch MY, Beziau DM, Marsman RF, Faivre L, Barc J, Dina C, Bertaux G, Barthez O et al (2012) Multifocal ectopic Purkinje-related premature contractions: a new SCN5A-related cardiac channelopathy. J Am Coll Cardiol 60:144–156

[39] Lauxmann S, Boutry-Kryza N, Rivier C, Mueller S, Hedrich UB, Maljevic S, Szepetowski P, Lerche H, Lesca G(2013) An SCN2A mutation in a family with infantile seizures from Madagascar reveals an increased subthreshold Na(+) current. Epilepsia 54:e117–e121

[40] Leipold E, Liebmann L, Korenke GC, Heinrich T, Giesselmann S, Baets J, Ebbinghaus M, Goral RO, Stodberg T, Hennings JC et al(2013) A de novo gain-of-function mutation in SCN11A causes loss of pain perception. Nat Genet 45:1399–1404

[41] Leipold E, Hanson-Kahn A, Frick M, Gong P, Bernstein JA, Voigt M, Katona I, OliverGoral R, Altmuller J, Nurnberg P et al (2015) Cold-aggravated pain in humans caused by a hyperactive NaV1.9 channel mutant. Nat Commun 6:10049

[42] Liao Y, Deprez L, Maljevic S, Pitsch J, Claes L, Hristova D, Jordanova A, Ala-Mello S, Bellan-Koch A, Blazevic D et al (2010) Molecular correlates of age-dependent seizures in an inherited neonatal-infantile epilepsy. Brain 133:1403–1414

[43] Lossin C, Wang DW, Rhodes TH, Vanoye CG, George AL (2002) Molecular basis of an inherited epilepsy. Neuron 34:877–884

[44] Makiyama T, Akao M, Shizuta S, Doi T, Nishiyama K, Oka Y, Ohno S, Nishio Y, Tsuji K, Itoh H et al (2008) A novel SCN5A gain-of-function mutation M1875T associated with familial atrial fibrillation. J Am Coll Cardiol 52:1326–1334

[45] Mantegazza M, Gambardella A, Rusconi R, Schiavon E, Annesi F, Cassulini RR, Labate A, Carrideo S, Chifari R, Canevini MP et al(2005) Identification of an Nav1.1 sodium channel (SCN1A) loss-of-function mutation associated with familial simple febrile seizures. Proc Natl Acad Sci USA 102:18177–18182

[46] Misra SN, Kahlig KM, George AL (2008) Impaired NaV1.2 function and reduced cell surface expression in benign familial neonatal-infantile seizures. Epilepsia 49:1535–1545

[47] MOE (2016) Molecular operating environment (MOE), 2013.08. Chemical Computing Group Inc, Montreal

[48] Olson TM, Michels VV, Ballew JD, Reyna SP, Karst ML, Herron KJ, Horton SC, Rodeheffer RJ, Anderson JL (2005) Sodium channel mutations and susceptibility to heart failure and atrial fibrillation. JAMA 293:447–454

[49] Payandeh J, Scheuer T, Zheng N, Catterall WA (2011) The crystal structure of a voltage-gated sodium channel. Nature 475:353–358

[50] Plummer NW, Meisler MH (1999) Evolution and diversity of mammalian sodium channel genes. Genomics 57:323–331

[51] Remme CA, Verkerk AO, Nuyens D, van Ginneken AC, van Brunschot S, Belterman CN, Wilders R, van Roon MA, Tan HL, Wilde AA et al (2006) Overlap syndrome of cardiac sodium channel disease in mice carrying the equivalent mutation of human SCN5A-1795insD. Circulation 114:2584–2594

[52] Shi X, Yasumoto S, Kurahashi H, Nakagawa E, Fukasawa T, Uchiya S, Hirose S (2012) Clinical spectrum of SCN2A mutations. Brain Dev 34:541–545

[53] Smits JP, Koopmann TT, Wilders R, Veldkamp MW, Opthof T, Bhuiyan ZA, Mannens MM, Balser JR, Tan HL, Bezzina CR et al(2005) A mutation in the human cardiac sodium channel (E161K) contributes to sick sinus syndrome, conduction disease and Brugada syndrome in two families. J Mol Cell Cardiol 38:969–981

[54] Song W, Shou W (2012) Cardiac sodium channel Nav1.5 mutations and cardiac arrhythmia. Pediatr Cardiol 33:943–949

[55] Sun YM, Favre I, Schild L, Moczydlowski E (1997) On the structural basis for size-selective permeation of organic cations through the voltage-gated sodium channel—effect of alanine mutations at the DEKA locus on selectivity, inhibition by Ca2+ and H+, and molecular sieving. J Gen Physiol 110:693–715

[56] Suter MR, Bhuiyan ZA, Laedermann CJ, Kuntzer T, Schaller M, Stauffacher MW, Roulet E, Abriel H, Decosterd I, Wider C (2015) p. L1612P, a novel voltage-gated sodium channel Nav1.7 mutation inducing a cold sensitive paroxysmal extreme pain disorder. Anesthesiology 122:414–423

[57] Swan H, Amarouch MY, Leinonen J, Marjamaa A, Kucera JP, Laitinen-Forsblom PJ, Lahtinen AM, Palotie A, Kontula K, Toivonen L et al (2014) Gain-of-function mutation of the SCN5A gene causes exercise-induced polymorphic ventricular arrhythmias. Circ Cardiovasc Genet 7:771–781

[58] Tan HL, Bink-Boelkens MT, Bezzina CR, Viswanathan PC, Beaufort- Krol GC, van Tintelen PJ, van den Berg MP, Wilde AA, Balser JR(2001) A sodium-channel mutation causes isolated cardiac conduction disease. Nature 409:1043–1047

[59] Tikhonov DB, Zhorov BS (2012) Architecture and pore block of eukaryotic voltage-gated sodium channels in view of NavAb bacterial sodium channel structure. Mol Pharmacol 82:97–104

[60] Vanoye CG, Gurnett CA, Holland KD, George AL, Kearney JA(2014) Novel SCN3A variants associated with focal epilepsy in children. Neurobiol Dis 62:313–322

[61] Vassilev PM, Scheuer T, Catterall WA (1988) Identification of an intracellular peptide segment involved in sodium channel inactivation. Science 241:1658–1661

[62] Veeramah KR, O’Brien JE, Meisler MH, Cheng X, Dib-Hajj SD, Waxman SG, Talwar D, Girirajan S, Eichler EE, Restifo LL et al(2012) De novo pathogenic SCN8A mutation identified by whole-genome sequencing of a family quartet affected by infantile epileptic encephalopathy and SUDEP. Am J Hum Genet 90:502–510

[63] Veerman CC, Wilde AA, Lodder EM (2015) The cardiac sodium channel gene SCN5A and its gene product NaV1.5: role in physiology and pathophysiology. Gene 573:177–187

[64] Wagnon JL, Barker BS, Hounshell JA, Haaxma CA, Shealy A, Moss T, Parikh S, Messer RD, Patel MK, Meisler MH (2016) Pathogenic mechanism of recurrent mutations of SCN8A in epileptic encephalopathy. Ann Clin Transl Neurol 3:114–123

[65] West JW, Patton DE, Scheuer T, Wang Y, Goldin AL, Catterall WA(1992) A cluster of hydrophobic amino acid residues required for fast Na(+)-channel inactivation. Proc Natl Acad Sci USA 89:10910–10914

[66] Wu J, Yan Z, Li Z, Yan C, Lu S, Dong M, Yan N (2015) Structure of the voltage-gated calcium channel Cav1.1 complex. Science 350:aad2395

[67] Wu J, Yan Z, Li Z, Qian X, Lu S, Dong M, Zhou Q, Yan N (2016) Structure of the voltage-gated calcium channel Cav1.1 at 3.6 A resolution. Nature 537:191–196

[68] Yang Y, Dib-Hajj SD, Zhang J, Zhang Y, Tyrrell L, Estacion M, Waxman SG (2012) Structural modelling and mutant cycle analysis predict pharmacoresponsiveness of a Na(V)1.7 mutant channel. Nat Commun 3:1186

[69] Yang Y, Huang J, Mis MA, Estacion M, Macala L, Shah P, Schulman BR, Horton DB, Dib-Hajj SD, Waxman SG (2016) Nav 1.7-A1632G mutation from a family with inherited erythromelalgia: enhanced firing of dorsal root ganglia neurons evoked by thermal stimuli. J Neurosci 36:7511–7522

[70] Zaharieva IT, Thor MG, Oates EC, van Karnebeek C, Hendson G, Blom E, Witting N, Rasmussen M, Gabbett MT, Ravenscroft G et al (2016) Loss-of-function mutations in SCN4A cause severe foetal hypokinesia or ‘classical’ congenital myopathy. Brain 139:674–691

[71] Zhang X, Ren W, DeCaen P, Yan C, Tao X, Tang L, Wang J, Hasegawa K, Kumasaka T, He J et al (2012) Crystal structure of an orthologue of the NaChBac voltage-gated sodium channel. Nature 486:130–134

[72] Zhang XY, Wen J, Yang W, Wang C, Gao L, Zheng LH, Wang T, Ran K, Li Y, Li X et al (2013) Gain-of-function mutations in SCN11A cause familial episodic pain. Am J Hum Genet 93:957–966

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