Syntaxin binding mechanism and disease-causing mutations in Munc18-2
Syntaxin binding mechanism and disease-causing mutations in Munc18-2
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DOI：
10.1073/pnas.1313474110
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发表时间：
2013-11-19
影响因子：
11.1
通讯作者：
Griffiths, Gillian M.
中科院分区：
文献类型：
--
作者：
Hackmann, Yvonne;Graham, Stephen C.;Griffiths, Gillian M.
Syntaxin 11 (Stx11) 或 Munc18-2 的突变会消除细胞毒性 T 淋巴细胞 (CTL) 和自然杀伤细胞 (NK) 的细胞毒性，并引起家族性噬血细胞性淋巴组织细胞增多症（分别为 FHL4 或 FHL5）。尽管已知 Munc18-2 与 Stx11 相互作用，但人们对控制这种相互作用特异性的分子机制或体外 IL-2 激活如何导致 CTL 和 NK 细胞毒性补偿知之甚少。为了了解 Munc18-2 的突变如何引起疾病，我们以 2.6 埃的分辨率解析了人类 Munc18-2 的结构，并绘制了 18 个点突变图。确定的四个表面突变（R39P、L130S、E132A、P334L）专门映射到 Munc18-2 的预测突触融合蛋白和可溶性 N-乙基马来酰亚胺敏感因子辅助蛋白受体结合位点。我们发现 Munc18-2 与 Stx11 N 端肽的结合亲和力比 Stx3 高 20 倍，这表明 Munc18-2 在选择性结合中具有潜在作用。 IL-2 激活后，Stx3 水平增加，当 Stx11 不存在时，有利于 Munc18-2 结合。同样，在 IL-2 激活的 CTL 中表达的 Munc18-1 能够结合 Stx11。这些发现为 IL-2 激活细胞中 Munc18-Stx 功能和细胞毒性的恢复提供了潜在的解释。
Mutations in either syntaxin 11 (Stx11) or Munc18-2 abolish cytotoxic T lymphocytes (CTL) and natural killer cell (NK) cytotoxicity, and give rise to familial hemophagocytic lymphohistiocytosis (FHL4 or FHL5, respectively). Although Munc18-2 is known to interact with Stx11, little is known about the molecular mechanisms governing the specificity of this interaction or how in vitro IL-2 activation leads to compensation of CTL and NK cytotoxicity. To understand how mutations in Munc18-2 give rise to disease, we have solved the structure of human Munc18-2 at 2.6 angstrom resolution and mapped 18 point mutations. The four surface mutations identified (R39P, L130S, E132A, P334L) map exclusively to the predicted syntaxin and soluble N-ethylmaleimide-sensitive factor accessory protein receptor binding sites of Munc18-2. We find that Munc18-2 binds the N-terminal peptide of Stx11 with a similar to 20-fold higher affinity than Stx3, suggesting a potential role in selective binding. Upon IL-2 activation, levels of Stx3 are increased, favoring Munc18-2 binding when Stx11 is absent. Similarly, Munc18-1, expressed in IL-2-activated CTL, is capable of binding Stx11. These findings provide potential explanations for restoration of Munc18-Stx function and cytotoxicity in IL-2-activated cells.