Zinc is a key regulator of the sperm-specific K+ channel (Slo3) function

The voltage- and pH-gated Slo3 potassium channel is exclusively expressed in mammalian spermatozoa. Its sensitivity to both voltage and alkalization plays a crucial role in sperm fertility, which is tightly coupled to the capacitation process. Here, we show that sperm-enriched divalent cation Zn 2+ undergoes dynamic alteration in spermatozoa during capacitation. We also found that intracellular Zn 2+ regulates alkalinization-induced hyperpolarization in mouse spermatozoa, which is mediated by the Slo3 channel. Further examination of zinc regulation in mouse Slo3 (mSlo3) revealed that, in the Xenopus oocyte expression system , intracellular zinc directly inhibits mouse Slo3 currents in a dose-dependent manner at micromolar concentrations, with exceptionally slow dissociation. By combining MD simulations and electrophysiology, we also identified amino acid residues contributing to the Zn 2+ slow dissociation from Slo3 channels. Our studies uncover the importance of intracellular zinc dynamics and its regulatory role in ion channels during sperm capacitation.