Yoo S H
National Creative Research Initiative Center for Secretory Granule Research, Biomedical Research Center, Korea Advanced Institute of Science and Technology, Yu Sung Gu, Dae Jeon, 305-701, Korea.
Trends Neurosci. 2000 Sep;23(9):424-8. doi: 10.1016/s0166-2236(00)01621-0.
The secretory granules of neuroendocrine cells, which function as an inositol (1,4,5)-trisphosphate-sensitive intracellular Ca2+ store, contain both the inositol (1,4,5)-trisphosphate receptor/Ca2+ channel and the high-capacity low-affinity Ca2+ storage proteins, chromogranins A and B. Chromogranins A and B, which exist in approximately 2 mm range in the secretory granules, can bind 50-100 mol of Ca2+/mol with dissociation constants of 2-4 mm. These proteins interact directly with the inositol (1,4,5)-trisphosphate receptor/ Ca2+ channel at the intragranular pH 5.5, not only changing the conformation of the inositol (1,4,5)-trisphosphate receptor/Ca2+ channel but also modulating the channel activity. Given the homo- and heterotetrameric existence of both the inositol (1,4,5)-trisphosphate receptor/Ca2+ channel and chromogranins A and B, these tetrameric proteins appear to interact, thus controlling the intracellular Ca2+ concentration.
神经内分泌细胞的分泌颗粒作为一种对肌醇（1,4,5）-三磷酸敏感的细胞内钙储存库，既含有肌醇（1,4,5）-三磷酸受体/Ca²⁺通道，也含有高容量低亲和力的钙储存蛋白嗜铬粒蛋白A和B。嗜铬粒蛋白A和B在分泌颗粒中的浓度约为2 mM，它们可以以2 - 4 mM的解离常数结合50 - 100 mol的Ca²⁺/mol。这些蛋白质在颗粒内pH 5.5时直接与肌醇（1,4,5）-三磷酸受体/Ca²⁺通道相互作用，不仅改变肌醇（1,4,5）-三磷酸受体/Ca²⁺通道的构象，还调节通道活性。鉴于肌醇（1,4,5）-三磷酸受体/Ca²⁺通道以及嗜铬粒蛋白A和B均存在同四聚体和异四聚体形式，这些四聚体蛋白似乎会相互作用，从而控制细胞内Ca²⁺浓度。
