Identification of voltage-dependent Ca2+ channels in sea urchin sperm

Functional evidence indicates that voltage-dependent Ca2+ (Ca-v) channels participate in sea urchin sperm motility and the acrosome reaction (AR), however, their molecular identity remains unknown. We have identified transcripts for two Ca2+ channel alpha 1 subunits in sea urchin testis similar in sequence to Ca(v)1.2 and Ca(v)2.3. Antibodies against rat Ca(v)1.2 and Ca(v)2.3 channels differentially label proteins in the flagella and acrosome of mature sea urchin sperm. The Cav channel antagonists nifedipine and nimodipine, which inhibit the AR, diminish the intracellular Ca2+ elevation induced by a K+-induced depolarization in valinomycin-treated sperm. These findings reveal that Ca(v)1.2 and Ca(v)2.3 channels could participate in motility and/or the AR in sea urchin sperm. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.