Abstact

Acid sensing is essential for various biological processes in animals, yet it exhibits species-specific characteristics. In this study, we identified a proton-dissociation-permeated sodium channel (PDPNaC1) in the antennal sensory neurons of the centipede Scolopendra subspinipes mutilans. PDPNaC1, which is permeable to monovalent cations, assembles as a homotrimer. Unlike most proton-gated channels, where proton binding induces currents, PDPNaC1's transient ion-permeable state is triggered by proton dissociation. By resolving the high-resolution cryo-electron microscopy (cryo-EM) structure of PDPNaC1, combined with mutagenesis and electrophysiological analyses, we identified Gly378, rather than the Gly-Ala-Ser tract, as a key determinant of ion selectivity. Furthermore, Ser376, located in the ion-permeable pathway, likely serves as a proton-binding site, leading to an H+-blocking effect that results in proton-dissociated currents. Thus, the identification of PDPNaC1 suggests the remarkable diversity of proton responses and molecular mechanisms in DEG/ENaC family.