The tethering complex HOPS catalyzes assembly of the soluble SNARE Vam7 into fusogenic trans-SNARE complexes.
The tethering complex HOPS catalyzes assembly of the soluble SNARE Vam7 into fusogenic trans-SNARE complexes.
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DOI：
10.1091/mbc.e13-07-0419
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发表时间：
2013-12
影响因子：
3.3
通讯作者：
Wickner W
中科院分区：
文献类型：
--
作者：
Zick M;Wickner W
大型拴系复合物在许多细胞内膜融合事件中起着重要作用，但其作用方式知之甚少。HOPS复合物的一个新的功能被发现在促进液泡融合，特异性募集可溶性SNARE Vam 7的融合trans-SNARE复合物的形成。酵母液泡膜的融合依赖于顺式可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体（SNARE）复合物的拆解和随后的新SNARE复合物的反式重组。顺式SNARE复合物的拆解由Sec 17/Sec 18 p释放可溶性SNARE Vam 7 p从液泡膜。因此，Vam 7 p需要在未来的融合位点被募集到膜上，以形成反式SNARE复合物。多亚基拴系同型融合和液泡蛋白分选（HOPS）复合物，这是必不可少的液泡膜的融合，以前被证明有直接的亲和力Vam 7 p。然而，这种相互作用的功能意义尚不清楚。使用完全重构的体外融合反应，我们现在表明HOPS通过招募Vam 7 p进行融合来促进膜融合。在HOPS的存在下，与其他栓系剂不同，非常低水平的添加的Vam 7 p足以诱导剧烈融合。这是Vam 7 p的特异性募集，而不是通过束缚间接刺激SNARE复合物的形成，因为HOPS不促进与少量可溶形式的另一种空泡SNARE Vti 1 p的融合。我们的研究结果建立了HOPS催化酵母液泡融合的多项任务中的另一项功能。
Large tethering complexes play an essential role in many intracellular membrane fusion events, yet their mode of action is poorly understood. A new function of the HOPS complex is uncovered in facilitating vacuolar fusion, the specific recruitment of the soluble SNARE Vam7 for the formation of fusogenic trans-SNARE complexes. The fusion of yeast vacuolar membranes depends on the disassembly of cis–soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) complexes and the subsequent reassembly of new SNARE complexes in trans. The disassembly of cis-SNARE complexes by Sec17/Sec18p releases the soluble SNARE Vam7p from vacuolar membranes. Consequently, Vam7p needs to be recruited to the membrane at future sites of fusion to allow the formation of trans-SNARE complexes. The multisubunit tethering homotypic fusion and vacuole protein sorting (HOPS) complex, which is essential for the fusion of vacuolar membranes, was previously shown to have direct affinity for Vam7p. The functional significance of this interaction, however, has been unclear. Using a fully reconstituted in vitro fusion reaction, we now show that HOPS facilitates membrane fusion by recruiting Vam7p for fusion. In the presence of HOPS, unlike with other tethering agents, very low levels of added Vam7p suffice to induce vigorous fusion. This is a specific recruitment of Vam7p rather than an indirect stimulation of SNARE complex formation through tethering, as HOPS does not facilitate fusion with a low amount of a soluble form of another vacuolar SNARE, Vti1p. Our findings establish yet another function among the multiple tasks that HOPS performs to catalyze the fusion of yeast vacuoles.