Calcium-dependent phospholipid scrambling by TMEM16F
Calcium-dependent phospholipid scrambling by TMEM16F
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DOI：
10.1038/nature09583
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发表时间：
2010-12-09
期刊：
影响因子：
64.8
通讯作者：
Nagata, Shigekazu
中科院分区：
文献类型：
--
作者：
Suzuki, Jun;Umeda, Masato;Nagata, Shigekazu
在所有动物细胞中，磷脂不对称地分布在质膜的外小叶和内小叶之间（1）。这种不对称的磷脂分布在各种生物系统中被破坏。例如，当血小板被激活时，它们暴露磷脂酰丝氨酸（PtdSer）以触发凝血系统（2，3）。PtdSer暴露被认为是由双向转运磷脂的Ca 2+依赖性磷脂乱序酶介导的（1，4），但其分子机制仍不清楚。在这里，我们表明，TMEM 16 F（跨膜蛋白16 F）是一个必不可少的组成部分的钙依赖性暴露的PtdSer的细胞表面。当小鼠B细胞系Ba/F3在低钙条件下用Ca 2+离子载体处理时，它可逆地暴露PtdSer。利用这一特性，我们建立了Ba/F3亚系，通过重复荧光激活细胞分选强烈暴露PtdSer。从该亚系构建互补DNA文库，并通过表达克隆鉴定了导致Ba/F3自发暴露PtdSer的cDNA。cDNA编码TMEM 16 F的组成型活性突变体，TMEM 16 F是一种具有八个跨膜片段的蛋白质（5）。野生型TMEM 16 F位于质膜上，并赋予磷脂的Ca 2+依赖性扰乱。发现一名患有斯科特综合征（6，7）的患者在编码TMEM 16 F的基因的剪接受体位点携带突变，导致蛋白质的过早终止，该综合征是由磷脂扰乱活性缺陷引起的（8，9）。
In all animal cells, phospholipids are asymmetrically distributed between the outer and inner leaflets of the plasma membrane(1). This asymmetrical phospholipid distribution is disrupted in various biological systems. For example, when blood platelets are activated, they expose phosphatidylserine (PtdSer) to trigger the clotting system(2,3). The PtdSer exposure is believed to be mediated by Ca2+-dependent phospholipid scramblases that transport phospholipids bidirectionally(1,4), but its molecular mechanism is still unknown. Here we show that TMEM16F (transmembrane protein 16F) is an essential component for the Ca2+-dependent exposure of PtdSer on the cell surface. When a mouse B-cell line, Ba/F3, was treated with a Ca2+ ionophore under low-Ca2+ conditions, it reversibly exposed PtdSer. Using this property, we established a Ba/F3 subline that strongly exposed PtdSer by repetitive fluorescence-activated cell sorting. A complementary DNA library was constructed from the subline, and a cDNA that caused Ba/F3 to expose PtdSer spontaneously was identified by expression cloning. The cDNA encoded a constitutively active mutant of TMEM16F, a protein with eight transmembrane segments(5). Wild-type TMEM16F was localized on the plasma membrane and conferred Ca2+-dependent scrambling of phospholipids. A patient with Scott syndrome(6,7), which results from a defect in phospholipid scrambling activity(8,9), was found to carry a mutation at a splice-acceptor site of the gene encoding TMEM16F, causing the premature termination of the protein.