Ca2+-dependent activator protein for secretion 1 is critical for constitutive and regulated exocytosis but not for loading of transmitters into dense core vesicles
Ca2+-dependent activator protein for secretion 1 is critical for constitutive and regulated exocytosis but not for loading of transmitters into dense core vesicles
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DOI：
10.1074/jbc.m703699200
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发表时间：
2007-07-20
影响因子：
4.8
通讯作者：
Sugita, Shuzo
中科院分区：
文献类型：
--
作者：
Fujita, Yoshihito;Xu, Ainan;Sugita, Shuzo
尽管CAPS1最初被鉴定为一种可溶性因子，可从透化的神经内分泌细胞中重建Ca2+依赖性分泌，但其在完整哺乳动物细胞中的确切功能仍存在争议。在这里，我们研究CAPS1的作用，通过产生稳定的细胞系，其中CAPS1是强烈下调。在这些细胞中，Ca2+依赖性分泌强烈减少不仅儿茶酚胺，但也转染的神经肽。这些分泌缺陷通过输注含有CAPS1的脑胞液或通过转染介导的CAPS1表达来挽救。全细胞膜片钳记录显示，在敲低的细胞中，胞吐的缓慢爆发和持续释放组分显著减少。出乎意料的是，它们也积累了更高的内源性和外源性递质，这是由于组成性分泌减少。电子显微镜没有发现异常的致密核心囊泡的数量或对接。我们的研究结果表明，CAPS1起着至关重要的作用，不仅在Ca 2+依赖，调节胞吐，但也在组成胞吐下游的囊泡对接。然而，他们不支持CAPS1的作用，在加载到致密的核心囊泡的发射机。
Although CAPS1 was originally identified as a soluble factor that reconstitutes Ca2+ -dependent secretion from permeabilized neuroendocrine cells, its exact function in intact mammalian cells remains controversial. Here we investigate the role for CAPS1 by generating stable cell lines in which CAPS1 is strongly down-regulated. In these cells, Ca2+ -dependent secretion was strongly reduced not only of catecholamine but also of a transfected neuropeptide. These secretion defects were rescued by infusion of CAPS1-containing brain cytosol or by transfection-mediated expression of CAPS1. Whole cell patch clamp recording revealed significant reductions in slow burst and sustained release components of exocytosis in the knockdown cells. Unexpectedly, they also accumulated higher amounts of endogenous and exogenous transmitters, which were attributable to reductions in constitutive secretion. Electron microscopy did not reveal abnormalities in the number or docking of dense core vesicles. Our results indicate that CAPS1 plays critical roles not only in Ca2+ -dependent, regulated exocytosis but also in constitutive exocytosis downstream of vesicle docking. However, they do not support the role for CAPS1 in loading transmitters into dense core vesicles.