Voltage-gated sodium (Na V ) channels play a fundamental role in normal neurological function, especially via the initiation and propagation of action potentials. The Na V 1.1 subtype is found in inhibitory interneurons of the brain and it is essential for maintaining a balance between excitation and inhibition in neuronal networks ...
Voltage-gated sodium (Na V ) channels play a fundamental role in normal neurological function, especially via the initiation and propagation of action potentials. The Na V 1.1 subtype is found in inhibitory interneurons of the brain and it is essential for maintaining a balance between excitation and inhibition in neuronal networks. Heterozygous loss-of-function mutations of SCN1A , the gene encoding Na V 1.1, underlie Dravet syndrome (DS), a severe pediatric epilepsy. We recently demonstrated that selective inhibition of Na V 1.1 inactivation prevents seizures and premature death in a mouse model of DS. Thus, selective modulators of Na V 1.1 might be useful therapeutics for treatment of DS as they target the underlying molecular deficit. Numerous scorpion-venom peptides have been shown to modulate the activity of Na V channels, but little is known about their activity at Na V 1.1. Here we report the isolation, sequence, three-dimensional structure, recombinant production, and functional characterization of two peptidic modulators of Na V 1.1 from venom of the buthid scorpion Hottentotta jayakari . These peptides, Hj1a and Hj2a, are potent agonists of Na V 1.1 (EC 50 of 17 and 32 nM, respectively), and they present dual α/β activity by modifying both the activation and inactivation properties of the channel. NMR studies of rHj1a indicate that it adopts a cystine-stabilized αβ fold similar to known scorpion toxins. Although Hj1a and Hj2a have only limited selectivity for Na V 1.1, their unusual dual mode of action provides an alternative approach to the development of selective Na V 1.1 modulators for the treatment of DS.
Organizational Affiliation:
Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia.
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