Subcellular distribution of chromogranins A and B in bovine adrenal chromaffin cells

The major secretory granule proteins chromogranins A (CGA) and B (CGB) have recently been shown to play critical roles in inositol 1,4,5-trisphosphate-dependent intracellular Ca2+ mobilizations. We determined here the subcellular distribution of CGA and CGB based on 3D-images of chromaffin cells, and found that similar to 95% of cellular CGA was present in secretory granules while similar to 5% was in the endoplasmic reticulum (ER), whereas similar to 57% of cellular CGB was in secretory granules while similar to 24% and similar to 19% were in the ER and nucleus, respectively. These results suggest that chromogranins are at the center of intracellular Ca2+ homeostasis in secretory cells. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.