Voltage-gated calcium channel that plays a central role in calcium-dependent physiological responses essential for successful fertilization, such as sperm hyperactivation, acrosome reaction and chemotaxis towards the oocyte. The CatSper calcium channel is indirectly activated by extracellular progesterone and prostaglandins following the sequence: progesterone > PGF1-alpha = PGE1 > PGA1 > PGE2 >> PGD2 (PubMed:21412338, PubMed:21412339, PubMed:26989199). The CatSper calcium channel is directly inhibited by endocannabinoid 2-arachidonoylglycerol (2AG) (PubMed:26989199). Indirect activation by progesterone takes place via the following mechanism: progesterone binds and activates the acylglycerol lipase ABHD2, which in turn mediates hydrolysis of 2AG inhibitor, relieving inhibition of the CatSper channel (PubMed:26989199). The primary effect of progesterone activation is to shift voltage dependence towards more physiological, negative membrane potentials; it is not mediated by metabotropic receptors and second messengers (PubMed:21412338, PubMed:21412339). Sperm capacitation enhances the effect of progesterone by providing additional negative shift. Also activated by the elevation of intracellular pH (PubMed:21412338, PubMed:21412339). Component of the CatSper complex or CatSpermasome composed of the core pore-forming members CATSPER1, CATSPER2, CATSPER3 and CATSPER4 as well as auxiliary members CATSPERB, CATSPERG, CATSPERD, CATSPERE, CATSPERZ, C2CD6/CATSPERT, TMEM249, TMEM262 and EFCAB9 (By similarity). HSPA1 may be an additional auxiliary complex member (By similarity). The core complex members CATSPER1, CATSPER2, CATSPER3 and CATSPER4 form a heterotetrameric channel (By similarity). The auxiliary CATSPERB, CATSPERG, CATSPERD and CATSPERE subunits form a pavilion-like structure over the pore which stabilizes the complex through interactions with CATSPER4, CATSPER3, CATSPER1 and CATSPER2 respectively (By similarity). TMEM262/CATSPERH interacts with CATSPERB, further stabilizing the complex. C2CD6/CATSPERT interacts at least with CATSPERD and is required for targeting the CatSper complex in the flagellar membrane (By similarity). Interacts with Ca(v)3.3/CACNA1I, leading to suppression of T-type calcium channel activity (PubMed:16740636). Specifically located in the principal piece of the sperm tail. Testis-specific. Expressed meiotically and post-meiotically. Down-regulated in patients lacking sperm motility. The disease is caused by variants affecting the gene represented in this entry. Belongs to the cation channel sperm-associated (TC 1.A.1.19) family. In mouse, Slco6c1 is an additional auxiliary subunit of the CatSper complex. It is unclear if the related SLCO6A1 protein performs the same role in non-rodent species.