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 1 (CatSper1) [].
This entry represents the T-type voltage-dependent calcium channel alpha-1I subtype, also known as Cav3.3. Sperm-specific CatSper1 and CatSper2 proteins can associate with and modulate the function of this channel, which might be important in the regulation of sperm motility []. It may also play a role in regulating GABAergic neurons [].Voltage-dependent calcium channels (VDCCs) mediate the entry of calcium ions into excitable cells and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, gene expression, cell motility, cell division and cell death. T-type VDCC belongs to low-voltage-activated (LVA) Ca2+ channels, whereas others belong to high-voltage-activated (HVA) Ca2+ channels.VDCCs consist of subunits. The alpha-1 subunit constitute the pore region which determines the fundamental channel properties []. Three types of alpha-1 subunit have been identified in T-type VDCCs molecules: alpha-1G [], alpha-1H [], and alpha-1I []. T-currents generated by the alpha-1I subunit display slow kinetics that differ markedly from the alpha-1G and alpha-1H currents [, , ].
