We describe the identification in aphids of a unique heterodimeric voltage-gated sodium channel which has an atypical ion selectivity filter and, unusually for insect channels, is highly insensitive to tetrodotoxin. We demonstrate that this channel has most likely arisen by adaptation (gene fission or duplication) of an invertebrate ancestral mono(hetero)meric channel. This is the only identifi...

Voltage-gated sodium channels are essential for the generation and propagation of action potentials in most excitable cells. They are the target sites of several classes of insecticides and acaricides. Isolation of full-length sodium channel cDNA is a critical and often difficult step toward an understanding of insecticide and acaricide resistance. We previously cloned and sequenced two overlap...

A regulatory mechanism for neuronal excitability consists in controlling sodium channel density at the plasma membrane. In cultured fetal neurons, activation of sodium channels by neurotoxins, e.g., veratridine and alpha-scorpion toxin (alpha-ScTx) that enhance the channel open state probability induced a rapid down-regulation of surface channels. Evidence that the initial step of activity-indu...

In many mammalian neurons, dense clusters of ion channels at the axonal initial segment and nodes of Ranvier underlie action potential generation and rapid conduction. Axonal clustering of mammalian voltage-gated sodium and KCNQ (Kv7) potassium channels is based on linkage to the actin-spectrin cytoskeleton, which is mediated by the adaptor protein ankyrin-G. We identified key steps in the evol...

A B S X R A C T Gating current (I~) has been studied in relation to inactivation of the Na channels. No component of lg has the time course of inactivation; apparent ly little or no charge movement is associated with this step. Inactivation nonetheless affects Ig by immobilizing about two-thirds of gating charge. Immobilization can be followed by measuring ON charge movement dur ing a pulse and...

A B S X R A C T Gating current (I~) has been studied in relation to inactivation of the Na channels. No component of lg has the time course of inactivation; apparent ly little or no charge movement is associated with this step. Inactivation nonetheless affects Ig by immobilizing about two-thirds of gating charge. Immobilization can be followed by measuring ON charge movement dur ing a pulse and...

A B S X R A C T Gating current (I~) has been studied in relation to inactivation of the Na channels. No component of lg has the time course of inactivation; apparent ly little or no charge movement is associated with this step. Inactivation nonetheless affects Ig by immobilizing about two-thirds of gating charge. Immobilization can be followed by measuring ON charge movement dur ing a pulse and...

OBJECTIVES To define a new type of dominant myotonic muscle disorder and to identify the gene lesion. DESIGN Case series, clinical examination and electromyography, measurements of grip force and relaxation time, and DNA analysis to probe for mutation in the gene for the skeletal muscle sodium channel. SETTING Outpatient clinic and home. PATIENTS Three families studied; all together, 17 a...