Efeito inibitório da rPnTx1 em canais de sódio ativados por voltagem

Abstract

Toxin PnTx1 represents approximately 0.45% of the total protein of the spider Phoneutria nigriventer venoms and was expressed in recombinant form (rPnTx1). Because of its physiological effects similar to PnTx1, rPnTx1 becomes a new interesting tool for study of the molecular physiology of sodium channels. The aim of this study is characterize electrophysiologicaly the effect of rPnTx1 in different isoforms of sodium channels of mammals and arthropods. To measure the sodium current in DRG, the patch clamp technique was used in the modality of whole cell. The inhibition of sodium currents was 38,4 + 6,1% when perfused with solution containing 1,5 M rPnTx1. In Xenopus oocytes, two-electrode voltage clamp recordings were performed. The observed order of potency for rPnTx1 was rNaV1.2 > rNaV1.7 rNaV1.4 > rNaV1.3 > mNaV1.6> hNaV1.8 while no effect was seen on hNav1.5 and arthropod isoforms. The concentration-dependence of rPnTx1 inhibition was compared with that of the native toxin in the isoform NaV1.2 and showed the same maximal effect (PnTx1: 85 + 0,8%; rPnTx1: 83,3 + 1,9%), whereas the IC50 of the recombinant toxin (IC50: 33,7nM) was significantly lower than the IC50 of native toxin (IC50:104,8 nM). For its high relative selectivity to neuronal type sodium channels, rPnTx1 becomes an important tool for structural and pharmacological studies.