Lipid interaction of the C terminus and association of the transmembrane segments facilitate atlastin-mediated homotypic endoplasmic reticulum fusion
Lipid interaction of the C terminus and association of the transmembrane segments facilitate atlastin-mediated homotypic endoplasmic reticulum fusion
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C 末端的脂质相互作用和跨膜片段的关联促进 atlastin 介导的同型内质网融合
DOI：
10.1073/pnas.1208385109
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发表时间：
2012-08-07
影响因子：
11.1
通讯作者：
Hu, Junjie
中科院分区：
文献类型：
--
作者：
Liu, Tina Y.;Bian, Xin;Hu, Junjie
内质网（ER）膜的同型融合由atlastin（ATL）介导，atlastin由含有GT3模块和三螺旋束的N-末端胞质结构域、随后的两个跨膜（TM）区段和C-末端尾（CT）组成。融合依赖于GTP水解诱导的胞质结构域的构象变化。在这里，我们表明，CT和TM段也需要有效的融合，并提供深入了解他们的机械作用。CT的基本特征是保守的两亲性螺旋。合成肽对应于螺旋，但不是无关的两亲性螺旋，可以肌动蛋白transto恢复无尾ATL的融合活性。CT通过直接与脂质双层相互作用并扰动脂质双层而不引起显著裂解来促进囊泡融合。TM区段不充当胞质结构域的单纯膜锚，而是介导ATL寡聚体的形成。C-末端螺旋或TM中的点突变损害ATL在体内产生和维持ER形态的能力。我们的研究结果表明，蛋白质-脂质和蛋白质-蛋白质相互作用的膜内合作的构象变化的胞质结构域，以实现同型ER膜融合。
The homotypic fusion of endoplasmic reticulum (ER) membranes is mediated by atlastin (ATL), which consists of an N-terminal cytosolic domain containing a GTPase module and a three-helix bundle followed by two transmembrane (TM) segments and a C-terminal tail (CT). Fusion depends on a GTP hydrolysis-induced conformational change in the cytosolic domain. Here, we show that the CT and TM segments also are required for efficient fusion and provide insight into their mechanistic roles. The essential feature of the CT is a conserved amphipathic helix. A synthetic peptide corresponding to the helix, but not to unrelated amphipathic helices, can actin transto restore the fusion activity of tailless ATL. The CT promotes vesicle fusion by interacting directly with and perturbing the lipid bilayer without causing significant lysis. The TM segments do not serve as mere membrane anchors for the cytosolic domain but rather mediate the formation of ATL oligomers. Point mutations in either the C-terminal helix or the TMs impair ATL’s ability to generate and maintain ER morphology in vivo. Our results suggest that protein–lipid and protein–protein interactions within the membrane cooperate with the conformational change of the cytosolic domain to achieve homotypic ER membrane fusion.