Cation channels of sperm

The cation channels of sperm also known as Catsper channels or CatSper, are ion channels that are related to the two-pore channels and distantly related to TRP channels. The four members of this family form voltage-gated Ca²⁺ channels that seem to be specific to sperm. As sperm encounter the more alkaline environment of the female reproductive tract, CatSper channels become activated by the altered ion concentration. These channels are required for proper fertilization. The study of these channels has been slow because they do not traffic to the cell membrane in many heterologous systems.

Of the four members of the Catsper family, Catsper1 is found in the primary piece of sperm. Catsper1 plays an important role in evoked Ca2+ entry and regulation of hyperactivation in sperm. Catsper2 is localized in the sperm tail and is responsible for regulation of hyperactivation. Catsper3 and Catsper4 are found in both, the testes and sperm and play an important role in the motility of hyperactivated sperm. Although Catsper seems to play an important role in sperm function, Catspers1-4 null mice have been found to have normal testicular histology, sperm counts and morphology, which is indicative of normal progression of spermatogenesis.