Chamberlain L H, Burgoyne R D
The Physiological Laboratory, Liverpool University, Liverpool L69 3BX, United Kingdom.
Mol Biol Cell. 1998 Aug;9(8):2259-67. doi: 10.1091/mbc.9.8.2259.
Cysteine string protein (Csp) is essential for neurotransmitter release in Drosophila. It has been suggested that Csp functions by regulating the activity of presynaptic Ca2+ channels, thus controlling exocytosis. We have examined the effect of overexpressing Csp1 in PC12 cells, a neuroendocrine cell line. PC12 cell clones overexpressing Csp1 did not show any changes in morphology, granule number or distribution, or in the levels of other key exocytotic proteins. This overexpression did not affect intracellular Ca2+ signals after depolarization, suggesting that Csp1 has no gross effect on Ca2+ channel activity in PC12 cells. In contrast, we show that Csp1 overexpression enhances the extent of exocytosis from permeabilized cells in response to Ca2+ or GTPgammaS in the absence of Ca2+. Because secretion from permeabilized cells is not influenced by Ca2+ channel activity, this represents the first demonstration that Csp has a direct role in regulated exocytosis.
半胱氨酸串珠蛋白（Csp）对果蝇神经递质的释放至关重要。有人提出，Csp通过调节突触前Ca2+通道的活性发挥作用，从而控制胞吐作用。我们研究了在神经内分泌细胞系PC12细胞中过表达Csp1的影响。过表达Csp1的PC12细胞克隆在形态、颗粒数量或分布以及其他关键胞吐蛋白水平上均未显示任何变化。这种过表达在去极化后不影响细胞内Ca2+信号，表明Csp1对PC12细胞中的Ca2+通道活性没有明显影响。相反，我们发现，在不存在Ca2+的情况下，过表达Csp1会增强通透细胞对Ca2+或GTPγS的胞吐程度。由于通透细胞的分泌不受Ca2+通道活性的影响，这首次证明了Csp在调节性胞吐作用中具有直接作用。
