Research Article

Molecular basis for pore blockade of human Na+ channel Nav1.2 by the μ-conotoxin KIIIA

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Science  22 Mar 2019:
Vol. 363, Issue 6433, pp. 1309-1313
DOI: 10.1126/science.aaw2999

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Targeting sodium channels

Voltage-gated sodium (Nav) channels have been implicated in cardiac and neurological disorders. There are many subtypes of these channels, making it challenging to develop specific therapeutics. A core α subunit is sufficient for voltage sensing and ion conductance, but function is modulated by β subunits and by natural toxins that can either act as pore blockers or gating modifiers (see the Perspective by Chowdhury and Chanda). Shen et al. present the structures of Nav1.7 in complex with both β1 and β2 subunits and with animal toxins. Pan et al. present the structure of Nav1.2 bound to β2 and a toxic peptide, the µ-conotoxin KIIIA. The structure shows why KIIIA is specific for Nav1.2. These and other recently determined Nav structures provide a framework for targeted drug development.

Science, this issue p. 1303, p. 1309; see also p. 1278

Abstract

The voltage-gated sodium channel Nav1.2 is responsible for the initiation and propagation of action potentials in the central nervous system. We report the cryo–electron microscopy structure of human Nav1.2 bound to a peptidic pore blocker, the μ-conotoxin KIIIA, in the presence of an auxiliary subunit, β2, to an overall resolution of 3.0 angstroms. The immunoglobulin domain of β2 interacts with the shoulder of the pore domain through a disulfide bond. The 16-residue KIIIA interacts with the extracellular segments in repeats I to III, placing Lys7 at the entrance to the selectivity filter. Many interacting residues are specific to Nav1.2, revealing a molecular basis for KIIIA specificity. The structure establishes a framework for the rational design of subtype-specific blockers for Nav channels.

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