Electrophysiological activity of a neurotoxic fraction from the venom of box jellyfish Carybdea marsupialis

Carybdea marsupialis is a widely distributed box jellyfish found in the Mediterranean and in the tropical waters of the Caribbean Sea. Its venom is a complex mixture of biologically active compounds that are used to catch prey. In order to evaluate the activity of the neurotoxins in the venom, bioassays were carried out using the marine crab Ocypode quadrata. The proteins with neurotoxic effect were partially purified using low-pressure liquid chromatography techniques. Gel filtration (Sephadex G-50M) was used as the first step and the active fraction in crabs was passed through a QAE Sephadex A-25 column. Finally, the active fraction was run onto a Fractogel EMD SO3− column. No further purification step could be carried out due to the loss of neurotoxic activity. The Fractogel EMD SO3− fraction was analyzed electrophysiologically using the voltage-clamp technique in Xenopus laevis oocytes expressing membrane proteins from rat brain through mRNA injection. The crude venom and a fraction were observed to affect crustaceans and showed at least two types of bioactivity in oocytes expressing brain proteins. The effects were dose-dependent and completely reversible. These results evidence the presence of neurotoxins in Carybdea marsupialis venom that act on membrane proteins of the vertebrate nervous system.