Orai-STIM-mediated Ca2+ release from secretory granules revealed by a targeted Ca2+ and pH probe.

ABSTRACT: Secretory granules (SGs) sequester significant calcium. Understanding roles for this calcium and potential mechanisms of release is hampered by the difficulty of measuring SG calcium directly in living cells. We adapted the Förster resonance energy transfer-based D1-endoplasmic reticulum (ER) probe to develop a unique probe (D1-SG) to measure calcium and pH in secretory granules. It significantly localizes to SGs and reports resting free Ca(2+) of 69 ± 15 μM and a pH of 5.8. Application of extracellular ATP to activate P2Y receptors resulted in a slow monotonic decrease in SG Ca(2+) temporally correlated with the occurrence of store-operated calcium entry (SOCE). Further investigation revealed a unique receptor-mediated mechanism of calcium release from SGs that involves SG store-operated

SUBMITTER: Dickson EJ 

PROVIDER: S-EPMC3529049 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature