Two-pore channels (TPCs): current controversies

Bioessays. 2014 Feb;36(2):173-83. doi: 10.1002/bies.201300118. Epub 2013 Nov 26.


Much excitement surrounded the proposal that a family of endo-lysosomal channels, the two-pore channels (TPCs) were the long sought after targets of the Ca(2+) -mobilising messenger, nicotinic acid adenine dinucleotide phosphate (NAADP). However, the role of TPCs in NAADP signalling may be more complex than originally envisaged. First, NAADP may not bind directly to TPCs but via an accessory protein. Second, two papers recently challenged the notion that TPCs are NAADP-regulated Ca(2+) channels by suggesting that they are highly selective Na(+) channels regulated by the lipid phosphatidylinositol 3,5-bisphosphate and by ATP. This paper aims critically to evaluate the evidence for TPCs as NAADP targets and to discuss how the new findings fit in with what we know about endo-lysosomal Ca(2+) stores.

Keywords: Ca2+; NAADP; TPC; channel; lysosome.

MeSH terms

  • Animals
  • Calcium / metabolism
  • Calcium Channels / metabolism*
  • Humans
  • Lysosomes / metabolism
  • NADP / analogs & derivatives
  • NADP / metabolism


  • Calcium Channels
  • NADP
  • Calcium