Fig. 1

Regulation of the Catsper channel: Sperm specific K⁺ channel (SLO₃) maintains flagellar membrane potential. Sperm Na⁺/H⁺ exchangers (NHEs) through cyclic adenosine monophosphate (cAMP) play a role on sperm fertility, while cAMP is generated in the process that bicarbonate (HCO3) activates atypical soluble adenylate cyclase (sAC). The Catsper channel is triggered by increasing intracellular PHi, which depends on sNHE and Voltage-gated H+ channel 1 (Hv1) channel pumping H⁺ out of sperm. Calcium balance in the sperm is maintained by Na⁺/Ca²⁺ exchanger and Ca²⁺ATPase exchanger. The Na⁺/Ca²⁺ exchanger exports one Ca²⁺ ion out of sperm and allows the entry of three Na⁺ ion, however, Ca²⁺ATPase is a Ca²⁺/H⁺ exchanger that removes intracellular Ca²⁺ and permits H⁺ entry into the sperm cell. Both sNHE and Hv1 channels are positive regulator of the Catsper channel, while Ca²⁺ATPase is a negative regulator of the Catsper channel