Creutz C E
J Cell Biol. 1981 Oct;91(1):247-56. doi: 10.1083/jcb.91.1.247.
When isolated chromaffin granules were aggregated by synexin (a Ca2+-binding protein present in chromaffin and other secretory tissues) and then exposed to cis-unsaturated fatty acids at 37 degrees C, they fused together to form large vesicles. The fusion was monitored by phase and electron microscopy and by turbidity measurements on the granule suspension. Arachidonic acid was the most effective fusogen, whereas trans-unsaturated fatty acids, saturated fatty acids, detergents or lysolecithin were inactive. During fusion some of the epinephrine of the granules was released but the soluble core proteins remained trapped in the resulting vesicles. These vesicles swelled to enclose the maximum volume. Although this swelling could be inhibited by increasing the osmotic strength of the medium, it did not appear to depend on the chemiosmotic properties of the granule membranes as it was not influenced by ATP, a proton ionophore, or an anion transport inhibitor. The regulators of this in vitro fusion--Ca2+, synexin, and free, cis-unsaturated fatty acids--may be present in the cytoplasm of the chromaffin cell when it is stimulated to release epinephrine and granule proteins by exocytosis. Therefore, this fusion event may be the same that occurs between chromaffin granules undergoing compound exocytosis.
当分离出的嗜铬颗粒被合胞素（一种存在于嗜铬组织和其他分泌组织中的钙结合蛋白）聚集，然后在37℃下暴露于顺式不饱和脂肪酸时，它们融合在一起形成大囊泡。通过相差显微镜、电子显微镜以及对颗粒悬浮液的浊度测量来监测融合过程。花生四烯酸是最有效的融合剂，而反式不饱和脂肪酸、饱和脂肪酸、去污剂或溶血卵磷脂则没有活性。在融合过程中，颗粒中的一些肾上腺素被释放出来，但可溶性核心蛋白仍被困在形成的囊泡中。这些囊泡膨胀以容纳最大体积。尽管这种膨胀可以通过增加培养基的渗透压强度来抑制，但它似乎并不依赖于颗粒膜的化学渗透特性，因为它不受ATP、质子离子载体或阴离子转运抑制剂的影响。这种体外融合的调节因子——钙离子、合胞素和游离的顺式不饱和脂肪酸——在嗜铬细胞受到刺激通过胞吐作用释放肾上腺素和颗粒蛋白时可能存在于其细胞质中。因此，这种融合事件可能与发生在进行复合胞吐作用的嗜铬颗粒之间的融合事件相同。
