Sea Anemone-Derived Toxin Avd3i Inhibited Sodium Channel Nav1.4.

Ion channels regulate ion transport across cell or organelle membranes, playing an important role in various biological processes. Sodium channel Nav1.4 is critical to initiating and propagating action potentials in skeletal muscles, and its dysfunction is associated with a variety of diseases, such as non-dystrophic myotonias. In this study, U-actitoxin-Avd3i (Avd3i), a Kunitz-type toxin derived from , was expressed in prokaryotic systems and was subsequently purified via high-pressure liquid chromatography. Patch clamp recording showed that Avd3i inhibited Nav1.4 in a concentration-dependent manner, with an IC of 25.43 μM. However, the toxin exerted no inhibitory activity in Nav1.5/Nav1.7 channels or Kv1.1/Kv1.3/Kv1.4/Kv4.2 potassium channels. Our study found that the sea anemone-derived toxin Avd3i inhibited sodium channel Nav1.4, providing a novel molecule that can act on the channel.