Phosphatidic acid induces conformational changes in Sec18 protomers that prevent SNARE priming
Phosphatidic acid induces conformational changes in Sec18 protomers that prevent SNARE priming
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DOI：
10.1074/jbc.ra118.006552
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发表时间：
2019-03-01
影响因子：
4.8
通讯作者：
Fratti, Rutilio A.
中科院分区：
文献类型：
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作者：
Starr, Matthew L.;Sparks, Robert P.;Fratti, Rutilio A.
真核细胞稳态需要细胞器之间的细胞组分的转移，并依赖于由SNARE蛋白催化的膜融合。失活的SNARE束被六聚体N-乙基马来酰亚胺敏感因子重新激活，囊泡融合ATP酶（Sec 18/NSF）驱动的拆卸，使新一轮的膜融合成为可能。我们先前发现磷脂酸（PA）结合Sec 18，从而将其与SNARE隔离，PA去磷酸化使Sec 18从膜上解离，使其与SNARE复合物结合。我们现在报告说，PA还诱导Sec 18的原体和六聚体Sec 18不能结合PA膜的构象变化。分子动力学（MD）分析表明，D1和D2域的Sec 18含有PA结合位点，PA结合所需的残基被掩蔽在六聚体Sec 18。重要的是，这些模拟还公开了在D1和D2结构域之间的接头区域中发生的主要构象变化，这与SNARE引发期间在六聚体Sec 18中发生的构象变化不同。总之，这些发现表明PA通过改变其结构和稳定膜结合Sec 18原聚体来调节Sec 18功能。
Eukaryotic cell homeostasis requires transfer of cellular components among organelles and relies on membrane fusion catalyzed by SNARE proteins. Inactive SNARE bundles are reactivated by hexameric N-ethylmaleimide-sensitive factor, vesicle-fusing ATPase (Sec18/NSF)-driven disassembly that enables a new round of membrane fusion. We previously found that phosphatidic acid (PA) binds Sec18 and thereby sequesters it from SNAREs and that PA dephosphorylation dissociates Sec18 from the membrane, allowing it to engage SNARE complexes. We now report that PA also induces conformational changes in Sec18 protomers and that hexameric Sec18 cannot bind PA membranes. Molecular dynamics (MD) analyses revealed that the D1 and D2 domains of Sec18 contain PA-binding sites and that the residues needed for PA binding are masked in hexameric Sec18. Importantly, these simulations also disclosed that a major conformational change occurs in the linker region between the D1 and D2 domains, which is distinct from the conformational changes that occur in hexameric Sec18 during SNARE priming. Together, these findings indicate that PA regulates Sec18 function by altering its architecture and stabilizing membrane-bound Sec18 protomers.