'Two-pore channel's: This small family of 2 members putatively forms cation-selective ion channels. They are predicted to contain two KV-style six-transmembrane domains, suggesting they form a dimer in the membrane. These channels are closely related to CatSper channels and, more distantly, to TRP channels.
TCP channels are found in both animal and plant cells. In mammalian cells, recent evidence has identified the two-pore channels (TPCs) within the endolysosomal system as NAADP-regulated Ca(2+) channels that release organellar Ca(2+) in response to NAADP. The TPCN genes are distinct from the KCNK genes encoding the Tandem pore domain potassium channels.