Cis and trans interactions between atlastin molecules during membrane fusion
Cis and trans interactions between atlastin molecules during membrane fusion
复制标题
DOI：
10.1073/pnas.1504368112
复制
发表时间：
2015-04-14
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
内质网蛋白（ATL）是一种膜锚定的GT3，介导内质网（ER）膜的同型融合，是形成外周ER管状网络所必需的。ATL究竟是如何介导膜融合的还知之甚少。在这里，我们表明，融合之前的短暂拴系的ATL-含有囊泡所造成的ATL分子在相对的膜的二聚化。拴系需要GTP水解，而不仅仅是GTP结合，因为两个ATL分子在GTP水解的过渡状态下被最强烈地拉在一起。大多数拴系事件是徒劳的，因此成功融合需要多轮GTP水解。支持的脂质双层实验表明，ATL分子坐在同一（顺式）膜也可以进行核苷酸依赖性二聚化。这些结果表明，GTP水解需要解离顺式二聚体，产生ATL单体池，可以与不同（反）膜上的分子二聚化。此外，束缚和融合需要每个膜中多个ATL分子的合作。我们提出了一个全面的模型ATL介导的融合，考虑到徒劳的束缚和竞争之间的顺式和反式相互作用。
Atlastin (ATL), a membrane-anchored GTPase that mediates homotypic fusion of endoplasmic reticulum (ER) membranes, is required for formation of the tubular network of the peripheral ER. How exactly ATL mediates membrane fusion is only poorly understood. Here we show that fusion is preceded by the transient tethering of ATL-containing vesicles caused by the dimerization of ATL molecules in opposing membranes. Tethering requires GTP hydrolysis, not just GTP binding, because the two ATL molecules are pulled together most strongly in the transition state of GTP hydrolysis. Most tethering events are futile, so that multiple rounds of GTP hydrolysis are required for successful fusion. Supported lipid bilayer experiments show that ATL molecules sitting on the same (cis) membrane can also undergo nucleotide-dependent dimerization. These results suggest that GTP hydrolysis is required to dissociate cis dimers, generating a pool of ATL monomers that can dimerize with molecules on a different (trans) membrane. In addition, tethering and fusion require the cooperation of multiple ATL molecules in each membrane. We propose a comprehensive model for ATL-mediated fusion that takes into account futile tethering and competition between cis and trans interactions.