A novel Ca2+-mediated cross-talk between endoplasmic reticulum and acidic organelles: Implications for NAADP-dependent Ca2+ signalling

- The Ca2+ response to NAADP activates TRPM4-mediated cation currents in HeLa cells.
- NAADP-evoked Ca2+ signals are impaired by disrupting acidic organelles.
- NAADP-evoked Ca2+ signals are hindered by blocking SERCA, RyRs and InsP3Rs.
- Disrupting Ca2+ uptake by acidic organelles prevents ER Ca2+ loading and vice versa.
- Pharmacological manipulation alone cannot reliably identify NAADP targets.