Scorpion toxins that block T-type Ca2+ channels in spermatogenic cells inhibit the sperm acrosome reaction

• Published in: Biochemical and biophysical research communications 2003-01, Vol.300 (2), p.408-414
• Main Authors: López-González, Ignacio, Olamendi-Portugal, Timoteo, De la Vega-Beltrán, José L, Van der Walt, Jurg, Dyason, Karin, Possani, Lourival D, Felix, Ricardo, Darszon, Alberto
• Format: Article
• Language: English
• Subjects: Acrosome Reaction - drug effects; Animals; Calcium Channel Blockers - pharmacology; Calcium Channels, T-Type - physiology; Cells, Cultured; Electric Conductivity; Kinetics; Male; Mice; Neurotoxins - pharmacology; Patch-Clamp Techniques; Scorpion Venoms - pharmacology; Spermatogonia - drug effects; Spermatogonia - physiology; Spermatozoa - drug effects; Spermatozoa - physiology
• ISSN: 0006-291X
• DOI: 10.1016/S0006-291X(02)02859-0

The acrosome reaction (AR) is a Ca(2+)-dependent event required for sperm to fertilize the egg. The activation of T-type voltage-gated Ca(2+) channels plays a key role in the induction of this process. This report describes the actions of two toxins from the scorpion Parabuthus granulatus named kurtoxin-like I and II (KLI and KLII, respectively) on sperm Ca(2+) channels. Both toxins decrease T-type Ca(2+) channel activity in mouse spermatogenic cells and inhibit the AR in mature sperm. Saturating concentrations of the toxins inhibited at most approximately 70% of the whole-cell Ca(2+) current, suggesting the presence of a toxin-resistant component. In addition, both toxins inhibited approximately 60% of the AR, which is consistent with the participation of T-type Ca(2+) channels in the sperm AR.