CATSPER (cationic channel of sperm) is a complex ion channel that mediates Ca2+ entry in sperm flagellum and is required for sperm hyperactivation and male fertility []. The CATSPER channel consists of four CatSper proteins (CatSper1-4) that form a tetramer surrounding a Ca(2+)-selective pore. In addition to the pore-forming proteins, the CATSPER channel contains auxiliary subunits [].All four CatSper proteins are predicted to contain a common coiled-coil protein-protein interaction domain in their C-terminal tail []and all four are required for male fertility and sperm cell hyperactivated motility []. The CatSper channel of human sperm is activated by progesterone [].This entry represents cation channel sperm-associated protein 4 (CatSper4) [].
