Scorpion toxins interact with nicotinic acetylcholine receptors.

Neurotoxins are among the main components of scorpion and snake venoms. Scorpion neurotoxins affect voltage-gated ion channels, while most snake neurotoxins target ligand-gated ion channels, mainly nicotinic acetylcholine receptors (nAChRs). We report that scorpion venoms inhibit alpha-bungarotoxin binding to both muscle-type nAChR from Torpedo californica and neuronal human alpha 7 nAChR. Toxins inhibiting nAChRs were identified as OSK-1 (alpha-KTx family) from Orthochirus scrobiculosus and HelaTx1 (kappa-KTx family) from Heterometrus laoticus, both being blockers of voltage-gated potassium channels. With an IC50 of 1.6 mu m, OSK1 inhibits acetylcholine-induced current through mouse muscle-type nAChR heterologously expressed in Xenopus oocytes. Other well-characterized scorpion toxins from these families also bind to Torpedo nAChR with micromolar affinities. Our results indicate that scorpion neurotoxins present target promiscuity.