Egg coat proteins activate calcium entry into mouse sperm via CATSPER channels

During mammalian fertilization, the contact between sperm and egg triggers increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) in sperm. Voltage-gated Ca(2+) channels (Ca(V)s) are believed to mediate the initial phase of [Ca(2+)](i) increases in sperm induced by egg coat (zona pellucida [ZP]) glycoproteins, while store depletion-activated Ca(2+) entry is thought to mediate the sustained phase. Using patch-clamp recording and Ca(2+) imaging, we show herein that Ca(V) channel currents, while found in spermatogenic cells, are not detectable in epididymal sperm and are not essential for the ZP-induced [Ca(2+)](i) changes. Instead, CATSPER channels localized in the distal portion of sperm (the principal piece) are required for the ZP-induced [Ca(2+)](i) increases. Furthermore, the ZP-induced [Ca(2+)](i) increase starts from the sperm tail and propagates toward the head.