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Updated: Feb 16, 2026

Single-Cell Calcium Imaging for Studying the Activation of Calcium Ion Channels
Published on: December 13, 2024
Activation of the inositol 1,4,5-trisphosphate receptor by the calcium storage protein chromogranin A
Edwin C Thrower1, Hee Yun Park, Seung Ho So
1Department of Pharmacology, Yale University, New Haven, Connecticut 06520, USA. edwin.thrower@yale.edu
Abstract:
Secretory granules of neuroendocrine cells are inositol 1,4,5-trisphosphate (InsP(3))-sensitive Ca(2+) stores in which the Ca(2+) storage protein, chromogranin A (CGA), couples with InsP(3)-gated Ca(2+) channels (InsP(3)R) located in the granule membrane. The functional aspect of this coupling has been investigated via release studies and planar lipid bilayer experiments in the presence and absence of CGA. CGA drastically increased the release activity of the InsP(3)R by increasing the channel open probability by 9-fold and the mean open time by 12-fold. Our results show that CGA-coupled InsP(3)Rs are more sensitive to activation than uncoupled receptors. This modulation of InsP(3)R channel activity by CGA appears to be an essential component in the control of intracellular Ca(2+) concentration by secretory granules and may regulate the rate of vesicle fusion and exocytosis.
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