Mahling, R.; Hegyi, B.; Cullen, E. R.; Cho, T.; Rodriques, A. R.; Fossier, L.; Yehya, M.; Yang, L.; Chen, B.-X.; Katchman, A. N.; Chakouri, N.; Ji, R.; Wan, E. Y.; Kushner, J. S.; Marx, S. O.; Ovchinnikov, S.; Makinson, C. D.; Bers, D. M.; Ben-Johny, M.

Ion channels orchestrate electrical signaling in excitable cells. In nature, ion channel function is customized by modulatory proteins that have evolved to fulfill distinct physiological needs. Yet, engineering synthetic modulators that precisely tune ion channel function is challenging. One example involves the voltage-gated sodium (NaV) channel that initiates the action potential, and whose dysfunction amplifies late/persistent sodium current (INaL), a commonality that underlies various human diseases including cardiac arrhythmias and epilepsy. Here, using a computational protein design platform, we engineered a de novo peptide modulator, ELIXIR, that binds NaV channels with submicromolar affinity. Functional analysis revealed an unexpected selectivity in inhibiting pathogenic INaL and confirmed its effectiveness in reversing NaV dysfunction linked to both cardiac arrhythmias and epilepsy in cellular and murine models. These findings exemplify the efficacy of de novo protein design for engineering synthetic ion channel modulators and sets the stage for rational design of future therapeutic approaches.