Peptide toxins isolated from spider venom that modulate gating of voltage-dependent K+ channels

Spider venom, like snake, bee and scorpion venom, is a rich source of ion c hannel modulators. Spider toxins that block Ca2+ channels and glutamate rec eptor-operated channels have been described. Recently, two new families of toxins that block K+ channels were isolated from spider venom. Hanatoxins, isolated from the venom of the Chilean tarantula Grammostola spatulata, inh ibit Kv2.1 and Kv4.2. Kv2.1 is a Shab-related voltage activated K+ channel isolated from rat brain; Kv4.2 is a Shal-related K+ channel responsible for the transient outward K+ current (I-to) that initiates repolarization of c ardiac and neural action potentials. Three toxins (heteropodotoxins) isolat ed from the venom of a free-living spider, Heteropoda venatoria, also inhib it Kv4.2. Because spider venom is logistically difficult to obtain, much le ss is known about spider venoms than snake and scorpion venoms. It is likel y that development of this resource in reserve will yield many more interes ting and useful ion channel modulators.