The sperm acrosome reaction is a Ca(2+)-dependent secretory event required for fertilization. Adhesion to the egg's zona pellucida promotes Ca2+ influx through voltage-sensitive channels, thereby initiating secretion. We used potentiometric fluorescent probes to determine the role of sperm membrane potential in regulating Ca2+ entry. ZP3, the glycoprotein agonist of the zona pellucida, depolarizes sperm membranes by activating a pertussis toxin-insensitive mechanism with the characteristics of a poorly selective cation channel. ZP3 also activates a pertussis toxin-sensitive pathway that produces a transient rise in internal pH. The concerted effects of depolarization and alkalinization open voltage-sensitive Ca2+ channels. These observations suggest that mammalian sperm utilize membrane potential-dependent signal transduction mechanisms and that a depolarization pathway is an upstream transducing element coupling adhesion to secretion during fertilization.
ZP3-dependent activation of sperm cation channels regulates acrosomal secretion during mammalian fertilization.
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C Arnoult, Y Zeng, H M Florman; ZP3-dependent activation of sperm cation channels regulates acrosomal secretion during mammalian fertilization.. J Cell Biol 1 August 1996; 134 (3): 637–645. doi: https://doi.org/10.1083/jcb.134.3.637
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