Arabidopsis synaptotagmin 1 mediates lipid transport in a lipid composition‐dependent manner
Arabidopsis synaptotagmin 1 mediates lipid transport in a lipid composition‐dependent manner
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DOI：
10.1111/tra.12844
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发表时间：
2022-04
期刊：
影响因子：
4.5
通讯作者：
Tiantian Qian;Chenlu Li;Furong Liu;K. Xu;Chun Wan;Yinghui Liu;Haijia Yu
中科院分区：
文献类型：
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作者：
Tiantian Qian;Chenlu Li;Furong Liu;K. Xu;Chun Wan;Yinghui Liu;Haijia Yu
内质网（ER）-质膜（PM）接触位点（EPCSs）在真核生物中结构保守。富含EPCSs的拟南芥ER锚定突触结合蛋白1（SYT 1）在植物非生物胁迫耐受性中起着关键作用。很明显，SYT 1与PM相互作用以介导ER-PM连接。然而，SYT 1是否在EPCS执行其他功能仍然未知。在这里，我们报告说，SYT 1有效地转移磷脂膜之间。SYT 1的脂质转移活性高度依赖于磷脂酰肌醇4，5-二磷酸[PI（4，5）P2]，这是非生物胁迫下PM处积累的信号脂质。在机械上，虽然SYT 1基本上通过突触结合蛋白样线粒体脂质结合蛋白（SMP）结构域转移脂质，但有效的脂质转运需要C2 A结构域介导的膜束缚。有趣的是，我们观察到Ca 2+可以刺激SYT 1介导的脂质转运。除了PI（4，5）P2之外，Ca 2+活化需要磷脂酰丝氨酸，其是相对膜上的另一种带负电荷的脂质。总之，我们的研究将拟南芥SYT 1鉴定为EPCSs的脂质转移蛋白，并证明它与其他延伸突触结合蛋白具有保守和不同的机制。脂质组成和Ca 2+的关键作用表明，SYT 1介导的脂质转运受到响应非生物胁迫的信号的高度调节。
The endoplasmic reticulum (ER)‐plasma membrane (PM) contact sites (EPCSs) are structurally conserved in eukaryotes. The Arabidopsis ER‐anchored synaptotagmin 1 (SYT1), enriched in EPCSs, plays a critical role in plant abiotic stress tolerance. It has become clear that SYT1 interacts with PM to mediate ER‐PM connectivity. However, whether SYT1 performs additional functions at EPCSs remains unknown. Here, we report that SYT1 efficiently transfers phospholipids between membranes. The lipid transfer activity of SYT1 is highly dependent on phosphatidylinositol 4,5‐bisphosphate [PI(4,5)P2], a signal lipid accumulated at the PM under abiotic stress. Mechanically, while SYT1 transfers lipids fundamentally through the synaptotagmin‐like mitochondrial‐lipid‐binding protein (SMP) domain, the efficient lipid transport requires the C2A domain‐mediated membrane tethering. Interestingly, we observed that Ca2+ could stimulate SYT1‐mediated lipid transport. In addition to PI(4,5)P2, the Ca2+ activation requires the phosphatidylserine, another negatively charged lipid on the opposed membrane. Together, our studies identified Arabidopsis SYT1 as a lipid transfer protein at EPCSs and demonstrated that it takes conserved as well as divergent mechanisms with other extend‐synaptotagmins. The critical role of lipid composition and Ca2+ reveals that SYT1‐mediated lipid transport is highly regulated by signals in response to abiotic stresses.