Vacuolar sequential exocytosis of large dense-core vesicles in adrenal medulla
Vacuolar sequential exocytosis of large dense-core vesicles in adrenal medulla
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DOI：
10.1038/sj.emboj.7600983
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发表时间：
2006-02-22
期刊：
影响因子：
11.4
通讯作者：
Kasai, H
中科院分区：
文献类型：
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作者：
Kishimoto, T;Kimura, R;Kasai, H
通过双光子细胞外极性示踪剂成像观察完整肾上腺髓质的单个胞吐事件。嗜铬小泡的胞吐作用通常以连续的方式发生，首先涉及位于细胞周边的小泡，然后涉及位于细胞质内更深处的小泡。顺序胞吐作用优先发生在面向细胞间隙的质膜区域。化合物囊泡膨胀到其原始体积的五倍以上，并形成空泡胞外腔，作为囊泡内凝胶膨胀的结果，并通过融合孔和狭窄的细胞间隙将其限制在腔中。这种管腔肿胀极大地促进了连续的胞吐作用。SNARE蛋白SNAP 25迅速从质膜迁移到融合囊泡的膜上。这些数据表明，存在于细胞质内更深处的囊泡可以像细胞周边的囊泡一样准备好融合，并且胞外腔的肿胀促进了融合机器的组装。我们认为在Ca（2+）依赖的胞吐作用中存在两种融合就绪态的分子构型.
Individual exocytic events in intact adrenal medulla were visualized by two- photon extracellular polar- tracer imaging. Exocytosis of chromaffin vesicles often occurred in a sequential manner, involving first vesicles located at the cell periphery and then those present deeper within the cytoplasm. Sequential exocytosis occurred preferentially at regions of the plasma membrane facing the intercellular space. The compound vesicles swelled to more than five times their original volume and formed vacuolar exocytic lumens as a result of expansion of intravesicular gels and their confinement within the lumen by the fusion pore and the narrow intercellular space. Such luminal swelling greatly promoted sequential exocytosis. The SNARE protein SNAP25 rapidly migrated from the plasma membrane to the membrane of fused vesicles. These data indicate that vesicles present deeper within the cytoplasm can be fusion ready like those at the cell periphery, and that swelling of exocytic lumens promotes assembly of the fusion machinery. We suggest the existence of two molecular configurations for fusion- ready states in Ca (2+)- dependent exocytosis.