Gorr S U, Shioi J, Cohn D V
Department of Oral Health, University of Louisville, Kentucky 40292.
Am J Physiol. 1989 Aug;257(2 Pt 1):E247-54. doi: 10.1152/ajpendo.1989.257.2.E247.
Secretory granules of endocrine cells contain one or more of the acidic secretory proteins chromogranin A (secretory protein-I), chromogranin B (secretogranin I), and secretogranin II (chromogranin C). It has been proposed that these proteins play a role in the packaging of secretory products. In the present study, lysates of purified porcine adrenal chromaffin granules containing chromogranins A and B and a putative chromogranin B fragment bound calcium and formed aggregates in the presence of 10-20 mM calcium at pH 5-6 and at 100 mM or less KCl, NaCl, or norepinephrine. The precipitates contained virtually all of the chromogranin B and the chromogranin B fragment and about one-third of the chromogranin A. The aggregates did not form or were dissociated at the pH and salt concentration of the extracellular fluid. Calcium precipitated purified chromogranin A and chromogranin B from pure solution to the same extent as from the granule lysates. Parathormone, added to the lysates, was incorporated in the precipitates, whereas the acidic secretory protein ovalbumin and norepinephrine were not. These findings suggest that secretory protein-I and secretogranin can exist in situ as aggregates that may include selected secretory products.
内分泌细胞的分泌颗粒含有一种或多种酸性分泌蛋白，即嗜铬粒蛋白A（分泌蛋白-I）、嗜铬粒蛋白B（分泌粒蛋白I）和分泌粒蛋白II（嗜铬粒蛋白C）。有人提出这些蛋白质在分泌产物的包装过程中发挥作用。在本研究中，含有嗜铬粒蛋白A和B以及一种假定的嗜铬粒蛋白B片段的纯化猪肾上腺嗜铬颗粒裂解物在pH值为5 - 6、10 - 20 mM钙以及100 mM或更低的氯化钾、氯化钠或去甲肾上腺素存在的情况下结合钙并形成聚集体。沉淀物几乎包含了所有的嗜铬粒蛋白B和嗜铬粒蛋白B片段以及约三分之一的嗜铬粒蛋白A。在细胞外液的pH值和盐浓度下，聚集体不会形成或会解离。钙从纯溶液中沉淀纯化的嗜铬粒蛋白A和嗜铬粒蛋白B的程度与从颗粒裂解物中沉淀的程度相同。添加到裂解物中的甲状旁腺激素会掺入沉淀物中，而酸性分泌蛋白卵清蛋白和去甲肾上腺素则不会。这些发现表明，分泌蛋白-I和分泌粒蛋白可以以聚集体的形式原位存在，这些聚集体可能包含特定的分泌产物。
