Both RyRs and TPCs are required for NAADP-induced intracellular Ca²⁺ release.

Intracellular Ca(2+) release is mostly mediated by inositol trisphosphate, but intracellular cyclic-ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP) are important messengers in many systems. Whereas cADPR generally activates type 2 ryanodine receptors (RyR2s), the NAADP-activated Ca(2+) release mechanism is less clear. Using knockouts and antibodies against RyRs and Two-Pore Channels (TPCs), we have compared their relative importance for NAADP-induced Ca(2+) release from two-photon permeabilized pancreatic acinar cells. In these cells, cholecystokinin-elicited Ca(2+) release is mediated by NAADP. TPC2-KO reduced NAADP-induced Ca(2+) release by 64%, but the combination of TPC2-KO and an antibody against TPC1, significantly reduced Ca(2+) release by 86% (64% vs. 86%, p<0.0002). In RyR3-KO, NAADP-evoked Ca(2+) release reduced by ∼50% but, when combined with antibodies against RyR1, responses were 90% inhibited. Antibodies against RyR2 had practically no effect on NAADP-evoked Ca(2+) release, but reduced release in response to cADPR by 55%. Antibodies to RyR1 inhibited NAADP-induced Ca(2+) liberation by 81%, but only reduced cADPR responses by 30%. We conclude that full NAADP-mediated Ca(2+) release requires both TPCs and RyRs. The sequence of relative importance for NAADP-elicited Ca(2+) release from the all stores is RyR1>TPC2>RyR3>TPC1>>RyR2. However, when assessing NAADP-induced Ca(2+) release solely from the acidic stores (granules/endosomes/lysosomes), antibodies against TPC2 and TPC1 virtually abolished the Ca(2+) liberation as did antibodies against RyR1 and RyR3. Our results indicate that the primary, but very small, NAADP-elicited Ca(2+) release via TPCs from endosomes/lysosomes triggers the detectable Ca(2+)-induced Ca(2+) release via RyR1 and RyR3 occurring from the granules and the ER.

Gerasimenko JV ，Charlesworth RM ，Sherwood MW ，Ferdek PE ，Mikoshiba K ，Parrington J ，Petersen OH ，Gerasimenko OV ... -  《-》

Cyclic adenosine diphosphate ribose activates ryanodine receptors, whereas NAADP activates two-pore domain channels.

Ogunbayo OA ，Zhu Y ，Rossi D ，Sorrentino V ，Ma J ，Zhu MX ，Evans AM ... -  《-》

Calcium signaling via two-pore channels: local or global, that is the question.

Zhu MX ，Ma J ，Parrington J ，Calcraft PJ ，Galione A ，Evans AM ... -  《-》

NAADP mobilizes calcium from acidic organelles through two-pore channels.

Calcraft PJ ，Ruas M ，Pan Z ，Cheng X ，Arredouani A ，Hao X ，Tang J ，Rietdorf K ，Teboul L ，Chuang KT ，Lin P ，Xiao R ，Wang C ，Zhu Y ，Lin Y ，Wyatt CN ，Parrington J ，Ma J ，Evans AM ，Galione A ，Zhu MX ... -  《-》

Transient receptor potential mucolipin 1 (TRPML1) and two-pore channels are functionally independent organellar ion channels.

Yamaguchi S ，Jha A ，Li Q ，Soyombo AA ，Dickinson GD ，Churamani D ，Brailoiu E ，Patel S ，Muallem S ... -  《-》