Overview
- Blagbrough, I.S. et al. (1994) Tetra. Lett. 35, 2057.
- Moya, E. et al. (1994) Tetra. Lett. 35, 2061.
- Norris, T.M. et al. (1996) Mol. Pharmacol. 50, 939.
Alomone Labs sFTX-3.3 blocks P-type Ca2+ currents in Xenopus oocytes.A. Time course of P-type channel (CaV2.1+a2d1+b1a) activity before and during applications of 500 μM sFTX-3.3 (#F-130), and upon wash. Holding potential was -80 mV and currents were elicited every 10 seconds by 100 ms step to 0 mV. B. Superimposed current traces of P-type channels, before and during applications of 500 μM sFTX-3.3 (taken from the experiment described in A).
Polyamine amide spider toxins inhibit neuronal voltage-activated Ca2+ currents. A terminal arginine group is an important feature of these Ca2+ channel antagonists1-2.
FTX is a polyamine component of the venom of the American funnel web spider Agelenopsis aperta, and has been described as a selective antagonist of P-type voltage-dependent Ca2+ channels3-4. However, it has been demonstrated that FTX has actions at other sites including NMDA and GABA receptors and also on T-type calcium channels5.
sFTX-3.3, a synthetic funnel web spider toxin6-7, is a polyamine amide analogue of FTX. The structures of these polyamine containing compounds are not identical: sFTX-3.3 contains an amide carbonyl oxygen that is absent from the predicted structure of native FTX8. sFTX-3.3 has been shown to block P-type calcium channels in rat cerebellar Purkinje cells8 and antagonizes P-, N-, and L-type calcium channels in mammalian Purkinje and superior cervical ganglia neurons with similar potencies. Its IC50 against P-, N-, and L-type channels are ~0.24 mM, ~0.7 mM and ~0.7 mM, respectively9.
