Inhibition of insect calcium channels by huwentoxin V, a neurotoxin from Chinese tarantula Ornithoctonus huwena venom.
The effects of huwentoxin V, an insect neurotoxic peptide from Chinese tarantula Ornithoctonus huwena venom, were studied on neuronal voltage gated ion channels. Whole cell patch clamp configuration indicated that huwentoxin V specifically inhibited high voltage activated calcium channels in adult cockroach dorsal unpaired median neurons (IC(50) approximately 219 nM) while having no evident effect on voltage gated potassium and sodium channels. Omega conotoxin GVIA is a well known neuronal N type calcium channel blocker from the venom of the sea snail Conus geographus and it also can partially block calcium currents in cockroach dorsal unpaired median neurons. In our study, huwentoxin V inhibited omega conotoxin GVIA sensitive, diltiazem sensitive and partial omega conotoxin GVIA and diltiazem resistant calcium currents elicited from insect neurons. Based on the sensitivity of calcium currents to these toxins, insect neuronal HVA calcium channels might be classified into four types: Type I, omega conotoxin GVIA sensitive and huwentoxin V sensitive; type II, diltiazem sensitive and huwentoxin V sensitive; type III, huwentoxin V sensitive but omega conotoxin GVIA and diltiazem resistant; type IV, omega conotoxin GVIA and diltiazem resistant and huwentoxin V resistant. Its specificity, incomplete inhibition and insect toxic effects make it an interesting tool for investigating insect voltage gated calcium channels and development of new insecticidal compounds.
European journal of pharmacology