A mutant of the Buthus martensii Karsch antitumor-analgesic peptide exhibits reduced inhibition to hNav1.4 and hNav1.5 channels while retaining analgesic activity

Abstract

Scorpion toxins can kill other animals by inducing paralysis and arrhythmia, which limits the potential applications of these agents in the clinical management of diseases. Antitumor-analgesic peptide (AGAP), purified from Karsch, has been proved to possess analgesic and antitumor activities. Trp, a conserved aromatic residue of AGAP, might play an important role in mediating AGAP activities according to the sequence and homology-modeling analyses. Therefore, an AGAP mutant, W38G, was generated, and effects of both AGAP and the mutant W38G were examined by whole-cell patch clamp techniques on the sodium channels hNa1.4 and hNa1.5, which were closely associated with the biotoxicity of skeletal and cardiac muscles, respectively. The data showed that both W38G and AGAP inhibited the peak currents of hNa1.4 and hNa1.5; however, W38G induced a much weaker inhibition of both channels than AGAP. Accordingly, W38G exhibited much less toxic effect on both skeletal and cardiac muscles than AGAP The analgesic activity of W38G and AGAP were verified as well, and W38G retained analgesic activity similar to AGAP. Inhibition to both Na1.7 and Na1.8 was involved in the analgesic mechanism of AGAP and W38G. These findings indicated that Trp was a key amino acid involved in the biotoxicity of AGAP, and the AGAP mutant W38G might be a safer alternative for clinical application because it retains the analgesic efficacy with less toxicity to skeletal and cardiac muscles.

Scorpion toxin inhibits the voltage‐gated proton channel using a Zn2+‐like long‐range conformational coupling mechanism

“…These data suggested that rAGAP was successfully produced and correctly refolded in E. coli. Previously, it has been indicated that the W38G mutation in AGAP reduced its activity on Na V 1.4–1.5 channels (Xu et al, ). In our experiment, W38, as well as two other residues (K10 and R58) in AGAP, were mutated, and the effect of the mutations on toxin activity was evaluated.…”

The Pivotal Potentials of Scorpion Buthus Martensii Karsch-Analgesic‐Antitumor Peptide in Pain Management and Cancer

“…AGAP is an ion channel regulator with diverse activities on a variation of neuronal ion channels such as high-voltage-activated (HVA), low-voltage-activated (LVA) calcium channels as well as tetrodotoxin-resistant (TTX-R) sodium channels [ 16 ]. A total of nine genes (Na v 1.1–Na v 1.9) have been recognized to encode practical sodium channel isoforms [ 8 ]. Na v 1.4 encoded by SCN4A was primarily secreted by skeletal muscle.…”

“…It was necessary for the initiation as well as propagation of the action potential necessary for skeletal muscle contraction. On the other hand, Na v 1.3, Na v 1.7, Na v 1.8, and Na v 1.9 have been recognized as potential targets for analgesics [ 8 ].…”

“…Studies further showed that Na v 1.7 was linked with erythromelalgia, paroxysmal life-threatening pain disorder, and congenital insensitivity to pain [ 27 , 28 ]. Xu et al demonstrated that AGAP potently blocked the action of both hNa v 1.7 and hNa v 1.8, signifying that both channel isoforms were involved in the analgesic mechanisms of AGAP [ 8 ].…”

“…Studies demonstrated that AGAP may be a Na + -channel specific inhibitor because it was capable of inhibiting mRNA transcription of voltage-gated sodium channels (Na v ) [ 6 , 7 ]. Electrophysiological studies using hNa v 1.4, hNa v 1.5, hNa v 1.7, and hNa v 1.8 revealed that AGAP is possibly a β -type scorpion toxin rather than an α -type toxin [ 8 ].…”