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Updated: Jul 3, 2026
07:17
Single-Cell Calcium Imaging for Studying the Activation of Calcium Ion Channels
Published on: December 13, 2024
Two-pore channel-2 controls calmodulin-dependent STIM1 inactivation
Subo Lee1, Raphael Néré2, Kyoung Sun Park1
1Department of Physiology and Global Medical Science, Organelle Medicine Research Center, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea.
Nature Communications
|July 1, 2026
Summary
Lysosomal TPC2 channels regulate cellular calcium by inhibiting store-operated calcium entry (SOCE). This involves calcium-calmodulin-dependent inactivation of STIM1, impacting fundamental cellular processes.
Area of Science:
- Cellular Biology
- Molecular Physiology
- Calcium Signaling
Background:
- Lysosomal two-pore channels (TPC) release calcium (Ca2+) from the endoplasmic reticulum (ER).
- ER Ca2+ depletion activates STIM1-gated store-operated Ca2+ entry (SOCE) channels, crucial for cellular processes.
- The integration of TPC channels and STIM1 with cellular cues remains unclear.
Purpose of the Study:
- To investigate how TPC channels and STIM1 integrate intracellular and extracellular signals.
- To elucidate the mechanism by which TPC2 activation influences SOCE.
Main Methods:
- Utilized TPC2 activators (NAADP, TPC2-A1-N) in multiple cell lines.
- Assessed STIM1-Orai1 channel activity and STIM1 clustering using RFP-STIM1.
- Employed thapsigargin to induce store depletion and analyzed Ca2+ dynamics.
- Investigated the role of Calmodulin (CaM) and cytosolic Ca2+ using inhibitors and chelators.
- Examined STIM1 mutants truncated after the SOAR domain.
Main Results:
- TPC2 activation inhibited SOCE by promoting rapid, persistent Ca2+-CaM-dependent inactivation of the STIM-Orai activating region (SOAR).
- TPC2 activators enhanced the slow Ca2+ dependent inactivation (SCDI) of STIM1-gated Orai1 channels.
- TPC2 engagement triggered lysosomal Ca2+ release, mobilized ER Ca2+ stores, but prevented STIM1 recruitment and disassembled STIM1 clusters, acutely reversing SOCE.
- These TPC2-mediated effects persisted in SOAR mutants and were dependent on CaM and cytosolic Ca2+.
Conclusions:
- TPC2 channels, upon activation, inhibit SOCE through Ca2+- and CaM-dependent inactivation of STIM1.
- Released Ca2+ from lysosomes by TPC2 channels acts as a key regulator of STIM1 inactivation.
- This mechanism provides insight into how TPC channels and STIM1 coordinate cellular Ca2+ signaling.
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