Tx3-4 a toxin from the venom of spider Phoneutria nigriventer blocks calcium channels associated with exocytosis

• Published in: Neuroscience letters Vol. 439; no. 2; pp. 170 - 172
• Main Authors: de Castro Junior, Célio José, Pinheiro, Ana Cristina N., Guatimosim, Cristina, Cordeiro, Marta N., Souza, Alessandra H., Richardson, Michael, Romano-Silva, Marco A., Prado, Marco Antônio M., Gomez, Marcus V.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 11.07.2008; Elsevier
• Subjects: Animals; Araneae; Biological and medical sciences; Brain - ultrastructure; Calcium Channel Blockers - pharmacology; Calcium channels; Calcium Channels - drug effects; Dose-Response Relationship, Drug; Exocytosis; Exocytosis - drug effects; Fundamental and applied biological sciences. Psychology; Male; Neuropeptides - pharmacology; Neurotoxins - pharmacology; Phoneutria nigriventer; Phoneutria toxin; Potassium Chloride - pharmacology; Rats; Rats, Wistar; Spider Venoms - pharmacology; Synaptosomes; Synaptosomes - drug effects; Vertebrates: nervous system and sense organs; ω-Aga IVA; ω-CgTX GVIA; ω-CgTX MVIIC; ω-Aga IVA; ω-CgTX MVIIC; Calcium channels; ω-CgTX GVIA; Phoneutria toxin; Synaptosomes; Exocytosis; Toxin; Synaptosome; Calcium; Venom; Ionic channel
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/j.neulet.2008.05.019

The purpose of the present work was to investigate the pharmacological action of a calcium channel-blocking toxin from the venom of the spider Phonetic nigriventer, Tx3-4 on calcium channels coupled to exocytosis of synaptic vesicles. Tx3-4 blocked KCl-induced exocytosis of synaptic vesicles with an IC50 of 1.1 nM. To investigate whether the target of Tx3-4 overlaps with known calcium channels that mediate calcium entry and exocytosis, we used ω-toxins that interact selectively with neuronal calcium channels. The results indicate that the main population of voltage-sensitive calcium channels altered by Tx3-4 is P/Q calcium channels. In conclusion, Tx3-4 is a potent inhibitor of calcium channels involved in the KCl-induced exocytosis of synaptic vesicles in brain cortical synaptosomes.