Inhibition of high voltage-activated calcium channels by spider toxin PnTx3-6.

Abstract

Animal peptide toxins have become powerful tools to study structure-function relationships and physiological roles of voltage-activated Ca(2+) channels. In the present study, we investigated the effects of PnTx3-6, a neurotoxin purified from the venom of the spider Phoneutria nigriventer on cloned mammalian Ca(2+) channels expressed in human embryonic kidney 293 cells and endogenous Ca(2+) channels in N18 neuroblastoma cells. Whole-cell patch-clamp measurements indicate that PnTx3-6 reversibly inhibited L-(alpha(1C)/Ca(v)1.2), N-(alpha(1B)/Ca(v)2.2), P/Q-(alpha(1A)/Ca(v)2.1), and R-(alpha(1E)/Ca(v)2.3) type channels with varying potency (alpha(1B) > alpha(1E) > alpha(1A) > alpha(1C)) and IC(50) values of 122, 136, 263, and 607 nM, respectively. Inhibition occurred without alteration of the kinetics or the voltage dependence of the exogenously expressed Ca(2+) channels. In N18 cells, PnTx3-6 exhibited highest potency against N-type (conotoxin-GVIA-sensitive) current. In contrast to its effects on high voltage-activated Ca(2+) channels subtypes, application of 1 microM PnTx3-6 did not affect alpha(1G)/Ca(v)3.1 T-type Ca(2+) channels. Based on our study, we suggest that PnTx3-6 acts as a omega-toxin that targets high voltage-activated Ca(2+) channels, with a preference for the Ca(v)2 subfamily (N-, P/Q-, and R-types).

• Authors: Luciene B Vieira, Christopher Kushmerick, Michael E Hildebrand, Esperanza Garcia, Antony Stea, Marta N Cordeiro, Michael Richardson, Marcus Vinicius Gomez, Terrance P Snutch
• Journal: The Journal of pharmacology and experimental therapeutics (J Pharmacol Exp Ther) Vol. 314 Issue 3 Pg. 1370-7 (Sep 2005) ISSN: 0022-3565 [Print] United States
• PMID: 15933156 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Calcium Channel Blockers
• Calcium Channels, N-Type
• Neuropeptides
• Neurotoxins
• Spider Venoms
• Tx3 neurotoxin

Topics

• Amino Acid Sequence
• Animals
• Calcium Channel Blockers (pharmacology)
• Calcium Channels, N-Type (drug effects)
• Cell Line
• Humans
• Molecular Sequence Data
• Neuropeptides (chemistry, isolation & purification, pharmacology)
• Neurotoxins (pharmacology)
• Spider Venoms (pharmacology)