Characterization of the scrambling domain of the TMEM16 family
Characterization of the scrambling domain of the TMEM16 family
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DOI：
10.1073/pnas.1703391114
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发表时间：
2017-06-13
影响因子：
11.1
通讯作者：
Nagata, Shigekazu
中科院分区：
文献类型：
--
作者：
Gyobu, Sayuri;Ishihara, Kenji;Nagata, Shigekazu
TMEM 16蛋白家族有10个成员，每个成员携带10个跨膜片段。TMEM 16 A和16 B是Ca 2+激活的Cl-通道。其他几个成员，包括TMEM 16 F，促进响应细胞内Ca 2+的细胞膜的内外小叶之间的磷脂争夺。然而，TMEM 16蛋白在质膜中转运磷脂的机制仍然难以捉摸。在这里，我们表明，Ca 2+激活，TMEM 16 F支持的磷脂混乱在4 ℃进行。与TMEM 16 F和16 E类似，发现7个TMEM 16家族成员携带跨越第四和第五跨膜区段的结构域（SCRD;加扰结构域），其赋予TMEM 16 A加扰能力。通过将点突变引入TMEM 16 F，我们发现SCRD的第四跨膜段中的赖氨酸以及第三跨膜段中的精氨酸和第六跨膜段中的谷氨酸对于将磷脂酰丝氨酸从内叶暴露到外叶是重要的。然而，它们在内化磷脂中的作用是有限的。我们的研究结果表明，TMEM 16提供了一个裂缝含有亲水性的“垫脚石”的向外易位的磷脂。
The TMEM16 protein family has 10 members, each of which carries 10 transmembrane segments. TMEM16A and 16B are Ca2+-activated Cl- channels. Several other members, including TMEM16F, promote phospholipid scrambling between the inner and outer leaflets of a cell membrane in response to intracellular Ca2+. However, the mechanism by which TMEM16 proteins translocate phospholipids in plasma membranes remains elusive. Here we show that Ca2+-activated, TMEM16F-supported phospholipid scrambling proceeds at 4 degrees C. Similar to TMEM16F and 16E, seven TMEM16 family members were found to carry a domain (SCRD; scrambling domain) spanning the fourth and fifth transmembrane segments that conferred scrambling ability to TMEM16A. By introducing point mutations into TMEM16F, we found that a lysine in the fourth transmembrane segment of the SCRD as well as an arginine in the third and a glutamic acid in the sixth transmembrane segment were important for exposing phosphatidylserine from the inner to the outer leaflet. However, their role in internalizing phospholipids was limited. Our results suggest that TMEM16 provides a cleft containing hydrophilic "stepping stones" for the outward translocation of phospholipids.