MmTX1 and MmTX2 from coral snake venom potently modulate GABAAreceptor activity

• Published in: Proceedings of the National Academy of Sciences - PNAS 2015-02, Vol.112 (8), p.E891-E900
• Main Authors: Rosso, Jean-Pierre, Schwarz, Jürgen R., Diaz-Bustamante, Marcelo, Céard, Brigitte, Gutiérrez, José M., Kneussel, Matthias, Pongs, Olaf, Bosmans, Frank, Bougis, Pierre E.
• Format: Article
• Language: English
• ISSN: 0027-8424; 1091-6490

GABAAreceptors shape synaptic transmission by modulating Cl⁻ conductance across the cell membrane. Remarkably, animal toxins that specifically target GABAAreceptors have not been identified. Here, we report the discovery of micrurotoxin1 (MmTX1) and MmTX2, two toxins present in Costa Rican coral snake venom that tightly bind to GABAAreceptors at subnanomolar concentrations. Studies with recombinant and synthetic toxin variants on hippocampal neurons and cells expressing common receptor compositions suggest that MmTX1 and MmTX2 allosterically increase GABAAreceptor susceptibility to agonist, thereby potentiating receptor opening as well as desensitization, possibly by interacting with the α⁺/β⁻ interface. Moreover, hippocampal neuron excitability measurements reveal toxin-induced transitory network inhibition, followed by an increase in spontaneous activity. In concert, toxin injections into mouse brain result in reduced basal activity between intense seizures. Altogether, we characterized two animal toxins that enhance GABAAreceptor sensitivity to agonist, thereby establishing a previously unidentified class of tools to study this receptor family.