A Mixed Periodic Paralysis & Myotonia Mutant, P1158S, Imparts pH-Sensitivity in Skeletal Muscle Voltage-gated Sodium Channels

ABSTRACTSkeletal muscle channelopathies, many of which are inherited as autosomal dominant mutations, include both myotonia and periodic paralysis. Myotonia is defined by a delayed relaxation after muscular contraction, whereas periodic paralysis is defined by episodic attacks of weakness. One sub-type of periodic paralysis, known as hypokalemic periodic paralysis (hypoPP), is associated with low potassium levels. Interestingly, the P1158S missense mutant, located in the third domain S4-S5 linker of the ‘‘skeletal muscle’’ voltage-gated sodium channel, Nav1.4, has been implicated in causing both myotonia and hypoPP. A common trigger for these conditions is physical activity. We previously reported that Nav1.4 is relatively insensitive to changes in extracellular pH compared to Nav1.2 and Nav1.5. Given that intense exercise is often accompanied by blood acidosis, we decided to test whether changes in pH would push gating in P1158S towards either phenotype. Our results indicate that, unlike in WT Nav1.4, low pH depolarizes the voltage-dependence of activation and steady-state fast inactivation, decreases current density, and increases late currents in P1185S. Thus, P1185S turns the normally pH-insensitive Nav1.4 into a proton-sensitive channel. Using action potential modeling we also predict a pH-to-phenotype correlation in patients with P1158S. We conclude that activities which alter blood pH may trigger myotonia or periodic paralysis in P1158S patients.SIGNIFICANCE STATEMENTVoltage-gated sodium channels (Nav) contribute to the physiology and pathophysiology of electrical signaling in excitable cells. Nav subtypes are expressed in a tissue-specific manner, thus they respond differently to physiological modulators. For instance, the cardiac subtype, Nav1.5, can be modified by changes in blood pH; however, the skeletal muscle subtype, Nav1.4, is mostly pH-insensitive. Nav1.4 mutants can mostly cause either hyper-or hypo-excitability in skeletal muscles, leading to conditions such as myotonia or periodic paralysis. P1158S uniquely causes both phenotypes. This study investigates pH-sensitivity in P1158S, and describes how physiological pH changes can push P1158S to cause myotonia and periodic paralysis.

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Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac

The Journal of General Physiology ◽

10.1085/jgp.201411210 ◽

2014 ◽

Vol 144 (2) ◽

pp. 147-157 ◽

Cited By ~ 19

Author(s):

Tamer M. Gamal El-Din ◽

Todd Scheuer ◽

William A. Catterall

Keyword(s):

Membrane Potential ◽

Sodium Channel ◽

Sodium Channels ◽

Voltage Dependence ◽

Periodic Paralysis ◽

Membrane Potentials ◽

Structural Basis ◽

Voltage Gated ◽

Voltage Gated Sodium Channels ◽

Gating Charges

Voltage-gated sodium channels mediate the initiation and propagation of action potentials in excitable cells. Transmembrane segment S4 of voltage-gated sodium channels resides in a gating pore where it senses the membrane potential and controls channel gating. Substitution of individual S4 arginine gating charges (R1–R3) with smaller amino acids allows ionic currents to flow through the mutant gating pore, and these gating pore currents are pathogenic in some skeletal muscle periodic paralysis syndromes. The voltage dependence of gating pore currents provides information about the transmembrane position of the gating charges as S4 moves in response to membrane potential. Here we studied gating pore current in mutants of the homotetrameric bacterial sodium channel NaChBac in which individual arginine gating charges were replaced by cysteine. Gating pore current was observed for each mutant channel, but with different voltage-dependent properties. Mutating the first (R1C) or second (R2C) arginine to cysteine resulted in gating pore current at hyperpolarized membrane potentials, where the channels are in resting states, but not at depolarized potentials, where the channels are activated. Conversely, the R3C gating pore is closed at hyperpolarized membrane potentials and opens with channel activation. Negative conditioning pulses revealed time-dependent deactivation of the R3C gating pore at the most hyperpolarized potentials. Our results show sequential voltage dependence of activation of gating pore current from R1 to R3 and support stepwise outward movement of the substituted cysteines through the narrow portion of the gating pore that is sealed by the arginine side chains in the wild-type channel. This pattern of voltage dependence of gating pore current is consistent with a sliding movement of the S4 helix through the gating pore. Through comparison with high-resolution models of the voltage sensor of bacterial sodium channels, these results shed light on the structural basis for pathogenic gating pore currents in periodic paralysis syndromes.

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Spatiotemporal magnetic fields enhance cytosolic Ca 2+ levels and induce actin polymerization via activation of voltage-gated sodium channels in skeletal muscle cells

Biomaterials ◽

10.1016/j.biomaterials.2018.02.031 ◽

2018 ◽

Vol 163 ◽

pp. 174-184 ◽

Cited By ~ 9

Author(s):

Mónica Rubio Ayala ◽

Tatiana Syrovets ◽

Susanne Hafner ◽

Vitalii Zablotskii ◽

Alexandr Dejneka ◽

...

Keyword(s):

Skeletal Muscle ◽

Magnetic Fields ◽

Sodium Channels ◽

Actin Polymerization ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Voltage Gated ◽

Voltage Gated Sodium Channels

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Type B brevetoxins show tissue selectivity for voltage-gated sodium channels: comparison of brain, skeletal muscle and cardiac sodium channels

Toxicon ◽

10.1016/s0041-0101(03)00088-6 ◽

2003 ◽

Vol 41 (7) ◽

pp. 919-927 ◽

Cited By ~ 47

Author(s):

Marie-Yasmine Bottein Dechraoui ◽

John S. Ramsdell

Keyword(s):

Skeletal Muscle ◽

Sodium Channels ◽

Type B ◽

Voltage Gated ◽

Voltage Gated Sodium Channels ◽

Tissue Selectivity ◽

Cardiac Sodium Channels

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Point-Mutations in Skeletal Muscle Voltage-Gated Sodium Channels Confer Resistance to Tetrodotoxin: But at a Cost?

Biophysical Journal ◽

10.1016/j.bpj.2015.11.2354 ◽

2016 ◽

Vol 110 (3) ◽

pp. 436a-437a ◽

Cited By ~ 1

Author(s):

Robert E. del Carlo ◽

Normand Leblanc ◽

Edmund D. Brodie ◽

Chis R. Feldman

Keyword(s):

Skeletal Muscle ◽

Sodium Channels ◽

Point Mutations ◽

Voltage Gated ◽

Voltage Gated Sodium Channels

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Sodium Channelopathies of Skeletal Muscle and Brain

Physiological Reviews ◽

10.1152/physrev.00025.2020 ◽

2021 ◽

Author(s):

Massimo Mantegazza ◽

Sandrine Cestèle ◽

William Catterall

Keyword(s):

Skeletal Muscle ◽

Sodium Channels ◽

Cell Biology ◽

Periodic Paralysis ◽

Mouse Genetics ◽

Ion Conductance ◽

Voltage Gated Sodium Channels ◽

Wide Range ◽

Voltage Dependent ◽

Periodic Paralyses

Voltage-gated sodium channels initiate action potentials in nerve, skeletal muscle, and other electrically excitable cells. Mutations in them cause a wide range of diseases. These channelopathy mutations affect every aspect of sodium channel function, including voltage sensing, voltage-dependent activation, ion conductance, fast and slow inactivation, and both biosynthesis and assembly. Mutations that cause different forms of periodic paralysis in skeletal muscle were discovered first and have provided a template for understanding structure, function, and pathophysiology at the molecular level. More recent work has revealed multiple sodium channelopathies in the brain. Here we review the well-characterized genetics and pathophysiology of the periodic paralyses of skeletal muscle, and then use this information as a foundation for advancing our understanding of mutations in the structurally homologous a subunits of brain sodium channels that cause epilepsy, migraine, autism, and related co-morbidities. We include studies based on molecular and structural biology, cell biology and physiology, pharmacology, and mouse genetics. Our review reveals unexpected connections among these different types of sodium channelopathies.

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Voltage-sensor movements describe slow inactivation of voltage-gated sodium channels II: A periodic paralysis mutation in NaV1.4 (L689I)

The Journal of General Physiology ◽

10.1085/jgp.201210910 ◽

2013 ◽

Vol 141 (3) ◽

pp. 323-334 ◽

Cited By ~ 16

Author(s):

Jonathan R. Silva ◽

Steve A.N. Goldstein

Keyword(s):

Sodium Channels ◽

Time Course ◽

Slow Component ◽

Companion Paper ◽

Causal Link ◽

Periodic Paralysis ◽

Slow Inactivation ◽

Hyperkalemic Periodic Paralysis ◽

Voltage Gated ◽

Voltage Gated Sodium Channels

In skeletal muscle, slow inactivation (SI) of NaV1.4 voltage-gated sodium channels prevents spontaneous depolarization and fatigue. Inherited mutations in NaV1.4 that impair SI disrupt activity-induced regulation of channel availability and predispose patients to hyperkalemic periodic paralysis. In our companion paper in this issue (Silva and Goldstein. 2013. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201210909), the four voltage sensors in NaV1.4 responsible for activation of channels over microseconds are shown to slowly immobilize over 1–160 s as SI develops and to regain mobility on recovery from SI. Individual sensor movements assessed via attached fluorescent probes are nonidentical in their voltage dependence, time course, and magnitude: DI and DII track SI onset, and DIII appears to reflect SI recovery. A causal link was inferred by tetrodotoxin (TTX) suppression of both SI onset and immobilization of DI and DII sensors. Here, the association of slow sensor immobilization and SI is verified by study of NaV1.4 channels with a hyperkalemic periodic paralysis mutation; L689I produces complex changes in SI, and these are found to manifest directly in altered sensor movements. L689I removes a component of SI with an intermediate time constant (∼10 s); the mutation also impedes immobilization of the DI and DII sensors over the same time domain in support of direct mechanistic linkage. A model that recapitulates SI attributes responsibility for intermediate SI to DI and DII (10 s) and a slow component to DIII (100 s), which accounts for residual SI, not impeded by L689I or TTX.

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Extremely Potent Block of Bacterial Voltage-Gated Sodium Channels by µ-Conotoxin PIIIA

Marine Drugs ◽

10.3390/md17090510 ◽

2019 ◽

Vol 17 (9) ◽

pp. 510 ◽

Cited By ~ 2

Author(s):

Rocio K. Finol-Urdaneta ◽

Jeffrey R. McArthur ◽

Vyacheslav S. Korkosh ◽

Sun Huang ◽

Denis McMaster ◽

...

Keyword(s):

Skeletal Muscle ◽

Sodium Channel ◽

Sodium Channels ◽

Cell Voltage ◽

Hill Coefficient ◽

Dependent Manner ◽

Binding Modes ◽

Voltage Gated ◽

Voltage Gated Sodium Channels ◽

Conducting Pathway

µ-Conotoxin PIIIA, in the sub-picomolar, range inhibits the archetypal bacterial sodium channel NaChBac (NavBh) in a voltage- and use-dependent manner. Peptide µ-conotoxins were first recognized as potent components of the venoms of fish-hunting cone snails that selectively inhibit voltage-gated skeletal muscle sodium channels, thus preventing muscle contraction. Intriguingly, computer simulations predicted that PIIIA binds to prokaryotic channel NavAb with much higher affinity than to fish (and other vertebrates) skeletal muscle sodium channel (Nav 1.4). Here, using whole-cell voltage clamp, we demonstrate that PIIIA inhibits NavBac mediated currents even more potently than predicted. From concentration-response data, with [PIIIA] varying more than 6 orders of magnitude (10−12 to 10−5 M), we estimated an IC50 = ~5 pM, maximal block of 0.95 and a Hill coefficient of 0.81 for the inhibition of peak currents. Inhibition was stronger at depolarized holding potentials and was modulated by the frequency and duration of the stimulation pulses. An important feature of the PIIIA action was acceleration of macroscopic inactivation. Docking of PIIIA in a NaChBac (NavBh) model revealed two interconvertible binding modes. In one mode, PIIIA sterically and electrostatically blocks the permeation pathway. In a second mode, apparent stabilization of the inactivated state was achieved by PIIIA binding between P2 helices and trans-membrane S5s from adjacent channel subunits, partially occluding the outer pore. Together, our experimental and computational results suggest that, besides blocking the channel-mediated currents by directly occluding the conducting pathway, PIIIA may also change the relative populations of conducting (activated) and non-conducting (inactivated) states.

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