Activation of sodium channel by a novel α-scorpion toxin, BmK NT2, stimulates ERK1/2 and CERB phosphorylation through a Ca2+ dependent pathway in neocortical neurons

Neuronal excitability controls the expression of a variety of genes and proteins and therefore regulates neurite outgrowth and synapse formation, fundamental physiological processes controlling learning and memory. Scorpion venom contains many neurotoxins which alter ion channel activities that influence neuronal excitability. In this study, a novel scorpion peptide termed BmK NT2 was purified from venom of Chinese scorpion Buthus martensii Karsch by combining mass spectrum mapping and intracellular Ca2+ concentration measurement in primary cultured neocortical neurons. Electrophysiological experiments demonstrated that BmK NT2 concentration-dependently delayed inactivation of voltage-gated sodium channels (VGSCs) with an EC50 value of 0.91 μM, and shifted the steady-state activation and inactivation of VGSCs to hyperpolarized direction. The effects of BmK NT2 on electrophysiological characteristics of VGSCs were similar to that of α-scorpion toxins. BmK NT2 altered Ca2+ dynamics and increased phosphorylation of extracellular-regulated protein kinases (ERK) 1/2 and cAMP-response element binding (CREB) proteins, which were eliminated by the VGSC blocker, tetrodotoxin. These data demonstrate that BmK NT2 is a novel VGSC α-scorpion toxin which is sufficient to increase the phosphorylation of ERK1/2 and CREB proteins, suggesting that modulation of VGSC function by α-scorpion toxin exerts neurotrophic effect in primary cultured neocortical neurons.