Figure 5.

Schematic representation of how KCNQ1 potassium channel regulates human sperm function. When human sperm are treated with chromanol 293B, the K⁺ outflow currents mediated by KCNQ1 are inhibited, which causes a [K⁺]_i increase and the membrane depolarization. V_m changes regulate other voltage-gated channels and affect the electrical driving force for ions. Thus, [Cl⁻]_i increases, while the pH_i and [Ca²⁺]_i decreases. It is generally known that during capacitation, Ca²⁺ and HCO₃⁻ activate soluble adenylate cyclase (sAC) which converts ATP into cAMP. Then PKA can be activated. PKA subsequently activates target proteins and protein tyrosine phosphorylation levels increase. KCNQ1 in human sperm participates in ion homeostasis regulation and affects capacitation.