Triggered Ca2+ influx is required for extended synaptotagmin 1-induced ER-plasma membrane tethering
Triggered Ca2+ influx is required for extended synaptotagmin 1-induced ER-plasma membrane tethering
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DOI：
10.15252/embj.201591565
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发表时间：
2015-09-02
期刊：
影响因子：
11.4
通讯作者：
De Camilli, Pietro
中科院分区：
文献类型：
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作者：
Idevall-Hagren, Olof;Lue, Alice;De Camilli, Pietro
延伸突触结合蛋白 (E-Syts) 是 ER 蛋白，充当 ER 和质膜 (PM) 之间 Ca2+ 调节的系链，并在两膜之间的脂质转运中发挥推定作用。 Ca2+对其束缚功能的调节，以及其不同结构域在这种功能中的相互作用，仍然知之甚少。通过将半完整细胞暴露于不同 Ca2+ 浓度的缓冲液中，我们发现 E-Syt1 与富含 PI(4,5)P-2 的 PM 的结合关键需要其 C2C 和 C2E 结构域，并且这种结合的 EC50 在低微摩尔 Ca2+ 范围内。因此，E-Syt1 在 ER-PM 接触位点的积累仅在已知通过其从细胞外介质流入达到这些 Ca2+ 水平的实验操作下发生，例如成纤维细胞中的储存操作的 Ca2+ 进入和细胞中的膜去极化。我们还表明，尽管它们的生理功能非常不同，但 E-Syt1（ER 到 PM）和突触结合蛋白（分泌囊泡到 PM）的膜束缚经历了质膜脂质和胞质 Ca2+ 的类似调节。
The extended synaptotagmins (E-Syts) are ER proteins that act as Ca2+-regulated tethers between the ER and the plasma membrane (PM) and have a putative role in lipid transport between the two membranes. Ca2+ regulation of their tethering function, as well as the interplay of their different domains in such function, remains poorly understood. By exposing semi-intact cells to buffers of variable Ca2+ concentrations, we found that binding of E-Syt1 to the PI(4,5)P-2-rich PM critically requires its C2C and C2E domains and that the EC50 of such binding is in the low micromolar Ca2+ range. Accordingly, E-Syt1 accumulation at ER-PM contact sites occurred only upon experimental manipulations known to achieve these levels of Ca2+ via its influx from the extracellular medium, such as store-operated Ca2+ entry in fibroblasts and membrane depolarization in -cells. We also show that in spite of their very different physiological functions, membrane tethering by E-Syt1 (ER to PM) and by synaptotagmin (secretory vesicles to PM) undergo a similar regulation by plasma membrane lipids and cytosolic Ca2+.