Structural studies of the interaction of gating modifier toxins with voltage-gated sodium channels

Y Jiang, Y Chin and G King

Institute for Molecular Bioscience, The University of Queensland

The human voltage-gated sodium channel NaV1.7 plays a vital role in the amplification of pain signals in sensory neurons. While gain-of-function mutations in the SCN9A gene, which encodes the pore-forming α-subunit of NaV1.7, cause erythermalgia and paroxysmal extreme disorder, loss-of-function mutations in the same gene lead to a congenital indifference to pain. Thus, hNaV1.7 is a promising analgesic target. Numerous spider-venom peptides inhibit hNaV1.7 by binding to the domain II voltage-sensor domain and inhibiting channel activation. We aim to develop a molecular understanding of the interactions between these peptides and hNaV1.7 with a view towards rational design of peptide-based analgesics that selectively this channel. In attempt to obviate the difficulties in producing stable hNaV1.7 for structural studies, we produced a chimeric NaV channel in which the peptide-binding regions of the domain II voltage sensor of NaV1.7 were transplanted into a bacterial sodium channel, NaVRh, which has previously been successfully crystallised. The chimeric NaV channel was successfully expressed and purified, and shown to bind peptides that normally target hNaV1.7.