Elsevier

Biochimie

Volume 82, Issues 9–10, 10 September 2000, Pages 883-892
Biochimie

Molecular mechanisms of neurotoxin action on voltage-gated sodium channels

https://doi.org/10.1016/S0300-9084(00)01174-3Get rights and content

Abstract

Voltage-gated sodium channels are the molecular targets for a broad range of neurotoxins that act at six or more distinct receptor sites on the channel protein. These toxins fall into three groups. Both hydrophilic low molecular mass toxins and larger polypeptide toxins physically block the pore and prevent sodium conductance. Alkaloid toxins and related lipid-soluble toxins alter voltage-dependent gating of sodium channels via an allosteric mechanism through binding to intramembranous receptor sites. In contrast, polypeptide toxins alter channel gating by voltage sensor trapping through binding to extracellular receptor sites. The results of recent studies that define the receptor sites and mechanisms of action of these diverse toxins are reviewed here.

Introduction

Sodium channels are transmembrane proteins responsible for the voltage-dependent increase in sodium permeability that initiates action potentials [1]. Sodium channels consist of a pore forming α subunit of 260 kDa associated with auxiliary subunits: β1, β2 and β3 [2], [3], [4], [5]. The α subunit consists of four homologous domains (I–IV), each containing six transmembrane segments (S1–S6), and one reentrant segment (SS1/SS2) connected by internal and external polypeptide loops (figure 1A) [2], [6]. The S4 segments are positively charged and serve as voltage sensors to initiate the voltage-dependent activation of sodium channels by moving outward under the influence of the electric field (figure 1A) [7], [8], [9]. Inactivation is mediated by the short intracellular loop connecting domains III and IV (figure 1A) [8], [10], [11]. The membrane-reentrant loops between S5 and S6 (SS1-SS2) form the ion selectivity filter and the outer region of the pore (figure 1A) [12], [13], [14].

Sodium channels are the molecular target for several groups of neurotoxins, which strongly alter channel function by binding to specific receptor sites. Due to their high affinity and specificity, neurotoxins represent powerful tools to study the structure and the function of sodium channels, affecting both permeation and gating properties of the channel. Therefore, localization of the neurotoxin receptor sites gives unique information on the structure-function relationships of the sodium channel. Six different receptor sites have been identified on voltage-dependent sodium channels using different neurotoxins. Here, we have reviewed the sites and mechanisms of action of six different classes of neurotoxins that act on sodium channels.

Section snippets

Neurotoxin receptor sites

Early pharmacological studies of sodium channels led to the conclusion that neurotoxins act at four distinct receptor sites and have primary effects on either ion permeation or voltage-dependent gating (table I) [15], [16]. Subsequent studies provided evidence for site 5 [17], [18] and site 6 [19]. The receptor sites at which neurotoxins affect gating were found to be allosterically coupled, suggesting that conformational changes induced by neurotoxin binding alter the equilibrium between the

Pore-blocking toxins

Receptor site 1 on sodium channels is occupied by two different groups of toxins: the water soluble heterocyclic guanidines tetrodotoxin (TTX) and saxitoxin (STX) and the peptidic μ-contoxins. All of these toxins act from the extracellular side of the membrane. TTX is isolated from the tissues of at least 40 species of puffer fish [21], but it is also found in molluscs, crabs, octopus, and Central American frogs [22], [23], [24]. STX is produced by the marine dinoflagellate Gonyaulax catenella

Neurotoxin receptor site 2

Lipid-soluble grayanotoxins (found in rhododendron and other plants of the family Ericaceae), the alkaloids veratridine (from of Liliaceae), acotinine (from the plant Acotinum napellus) and batrachotoxin (from the skin of the Colombian frog Phyllobates aurotaenia) bind to receptor site 2. These toxins bind preferentially to the activated state of sodium channels and cause persistent activation at resting membrane potential via an allosteric mechanism that leads to block of sodium channel

Neurotoxin receptor site 3

Neurotoxin receptor site 3 of sodium channels is occupied by several groups of polypeptide toxins: α-scorpion toxins, sea-anemone toxins and some spider toxins. These toxins slow or block sodium channel inactivation [30], [57], [58], [59], [60], [61], [62], [63], [64], [65], [66].

Alpha-scorpion toxins are a family of structurally and functionally related polypeptides neurotoxins, each containing 60 to 70 amino acid residues cross-linked by four disulfide bonds [67], [68]. They have been

Molecular mechanisms of neurotoxin action on ion channels

From the extensive studies reviewed above, the molecular mechanisms of action of neurotoxins on sodium channels can be divided into three classes: pore block, indirect allosteric modulation of gating, and voltage-sensor trapping. These three mechanisms are considered below.

References (111)

  • Y Ohizumi et al.

    Geographutoxin II, a peptide sodium channel blocker that selectively inhibits [3H] saxitoxin binding to muscle and nerve sodium channels

    J. Biol. Chem.

    (1986)
  • Y Yanagawa et al.

    Blockade of [3H] lysine-tetrodotoxin binding to sodium channel proteins by conotoxin GIII

    Neurosci. Lett.

    (1986)
  • S.C.J.R Dudley et al.

    A μ-conotoxin-insensitive Na+ channel mutant: possible localization of a binding site at the outer vestibule

    Biophys. J.

    (1995)
  • M Chahine et al.

    Extrapore residues of the S5-S6 loop of domain 2 of the voltage-gated skeletal muscle sodium channel (rSkM1) contribute to the mu-conotoxin GIIIA binding site

    Biophys. J.

    (1998)
  • V.L Trainer et al.

    Site of covalent labeling by a photoreactive batrachotoxin derivative near transmembrane segment IS6 of the sodium channel alpha subunit

    J. Biol. Chem.

    (1996)
  • S.Y Wang et al.

    Batrachotoxin-resistant Na+ channels derived from point mutations in transmembrane segment D4-S6

    Biophys. J.

    (1999)
  • T Kimura et al.

    On site of action of grayanotoxin in domain 4 segment 6 of rat skeletal muscle sodium channel

    FEBS Lett.

    (2000)
  • E Benoit et al.

    Effects of ciguatoxin on current and voltage clamped frog myelinated nerve fibre

    Toxicon

    (1986)
  • A Lombet et al.

    Ciguatoxin and brevetoxins share a common receptor site on the neuronal voltage-dependent Na+ channel

    FEBS Lett.

    (1987)
  • C.J Bergman et al.

    Decreased rate of sodium conductance inactivation in the nodes of Ranvier induced by polypeptide toxin from sea anemone

    Biochim. Biophys. Acta

    (1976)
  • D Pauron et al.

    The voltage-dependent Na+ channel of insect nervous system identified by receptor sites for tetrodotoxin, and scorpion and sea anemone toxins

    Biochem. Biophys. Res. Commun.

    (1985)
  • P Delori et al.

    Scorpion venoms and neurotoxins: an immunological study

    Toxicon

    (1981)
  • F Couraud et al.

    Binding of scorpion and sea anemone neurotoxins to a common site related to the action potential Na+ ionophore in neuroblastoma cells

    Biochem. Biophys. Res. Commun.

    (1978)
  • D Gordon et al.

    Binding of an α scorpion toxin to insect sodium channels is not dependent on membrane potential

    FEBS Lett.

    (1993)
  • S Cestèle et al.

    Toxin III from Leiurus quinquestriatus quinquestriatus: a specific probe for receptor site 3 on insect sodium channels

    Insect Biochem. Mol. Biol.

    (1997)
  • R Ray et al.

    Binding of scorpion toxin to receptor sites associated with voltage-sensitive sodium channels in synaptic nerve ending particles

    J. Biol. Chem.

    (1978)
  • E Jover et al.

    Two types of scorpion neurotoxins characterized by their binding to two separate receptor sites on rat brain synaptosomes

    Biochem. Biophys. Res. Commun.

    (1980)
  • S Cestèle et al.

    Alpha-scorpion toxins binding on rat brain and insect sodium channels reveal divergent allosteric modulations by brevetoxin and veratridine

    J. Biol. Chem.

    (1995)
  • W.A Catterall et al.

    Sea anemone toxin and scorpion toxin share a common receptor site associated with the action potential ionophore

    J. Biol. Chem.

    (1978)
  • D Gordon et al.

    Scorpion toxins affecting sodium current inactivation bind to distinct homologous receptor sites on rat brain and insect sodium channels

    J. Biol. Chem.

    (1996)
  • M.J Gallagher et al.

    Importance of the unique cationic residues arginine 12 and lysine 49 in the activity of the cardiotonic polypeptide anthopleurin B

    J. Biol. Chem.

    (1994)
  • J.C Rogers et al.

    Molecular determinants of high affinity binding of alpha-scorpion toxin and sea anemone toxin in the S3-S4 extracellular loop in domain IV of the Na+ channel alpha subunit

    J. Biol. Chem.

    (1996)
  • G.R Benzinger et al.

    A specific interaction between the cardiac sodium channel and site-3 toxin anthopleurin B

    J. Biol. Chem.

    (1998)
  • M.F Sheets et al.

    The Na channel voltage sensor associated with inactivation is localized to the external charged residues of domain IV, S4

    Biophys. J.

    (1999)
  • S Cestèle et al.

    Voltage sensor-trapping: enhanced activation of sodium channels by beta-scorpion toxin bound to the S3-S4 loop in domain II

    Neuron

    (1998)
  • A.L Hodgkin et al.

    A quantitative description of membrane current and its application to conduction and excitation in nerves

    J. Physiol.

    (1952)
  • W.A Catterall

    Cellular and molecular biology of voltage-dependent sodium channels

    Physiol. Rev.

    (1992)
  • L.L Isom et al.

    Primary structure and functional expression of the beta 1 subunit of the rat brain sodium channel

    Science

    (1992)
  • K Morgan et al.

    Beta 3: An additional auxiliary subunit of the voltage-sensitive sodium channel that modulates channel gating with distinct kinetics

    Proc. Natl. Acad. Sci. USA

    (2000)
  • M Noda et al.

    Existence of distinct sodium channel messenger RNAs in rat brain

    Nature

    (1986)
  • C.M Armstrong

    Sodium channels and gating currents

    Physiol. Rev.

    (1981)
  • W Stühmer et al.

    Structural parts involved in activation and inactivation of sodium channel

    Nature

    (1989)
  • P.M Vassilev et al.

    Identification of an intracellular peptide segment involved in sodium channel inactivation

    Science

    (1988)
  • J.W West et al.

    A cluster of hydrophobic amino acid residues required for fast Na+ channel inactivation

    Proc. Natl. Acad. Sci. USA

    (1992)
  • S.H Heinemann et al.

    Calcium channel characteristics conferred on the sodium channel by single mutations

    Nature

    (1992)
  • W.A Catterall

    Neurotoxins that act on voltage-sensitive sodium channels in excitable membranes

    Annu. Rev. Pharmacol. Toxicol.

    (1980)
  • M.F Martin-Eauclaire et al.

    Scorpion neurotoxins: effects and mechanisms

  • W.A Catterall et al.

    Toxin T46 from Ptychodiscus brevis (formely Gymnodinium breve) enhances activation of voltage-sensitive sodium channels by veratridine

    Mol. Pharmacol.

    (1981)
  • M.A Poli et al.

    Brevetoxins, unique activators of voltage-sensitive sodium channels, bind to specific sites in rat vrain synaptosones

    Mol. Pharmacol.

    (1986)
  • F.A Fuhrman

    Tetrodotoxin.

    Sci. Am.

    (1967)
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