Saxiphilin neutralizes saxitoxin in mice

Researchers at the University of California, San Francisco (UCSF) led by Daniel Minor have discovered that a naturally occurring protein called saxiphilin, found in bullfrogs and other frogs, can neutralize saxitoxin (STX), a potent neurotoxin responsible for paralytic shellfish poisoning (PSP). In a study published July 16 in Nature Communications, saxiphilin acted as a molecular sponge, binding tightly to STX in the bloodstream and preventing it from reaching nerve and muscle cells. In mouse models, saxiphilin prevented poisoning when administered before or alongside STX, and rescued nearly all mice when given after exposure, mimicking real-world scenarios of accidental ingestion. The protein distributed throughout the body, including the brain, heart, and muscles. This discovery closes a century-old scientific mystery initiated by UCSF researcher Hermann Sommer in the 1920s-30s, who observed frog resistance to shellfish poison. Saxiphilin binds multiple STX variants, making it a promising broad-spectrum antidote. The research was funded by the United States — United States Department of Defense and the United States — National Institutes of Health, and involved collaboration with Stanford University chemist Justin Du Bois. Future work aims to engineer smaller versions of saxiphilin for improved protection and to develop faster shellfish testing methods.