The brace helices of MLKL mediate interdomain communication and oligomerisation to regulate cell death by necroptosis
The brace helices of MLKL mediate interdomain communication and oligomerisation to regulate cell death by necroptosis
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DOI：
10.1038/s41418-018-0061-3
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发表时间：
2018-09-01
影响因子：
12.4
通讯作者：
Murphy, James M.
中科院分区：
文献类型：
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作者：
Davies, Katherine A.;Tanzer, Maria C.;Murphy, James M.
程序性细胞死亡途径，坏死性凋亡，依赖于假激酶，混合谱系激酶结构域样（MLKL），用于死亡受体或Toll样受体连接下游的细胞执行。受体相互作用蛋白激酶-3（RIPK 3）介导的MLKL假激酶结构域的磷酸化导致MLKL从惰性状态转换为活化状态，其中N-末端四螺旋束（4 HB）“刽子手”结构域的暴露导致细胞死亡。MLKL活化的精确分子细节，包括低聚物组装的化学计量、膜易位和透化的机制，仍然是一个有争议的问题。在这里，我们剖析了连接4 HB到MLKL的假激酶结构域的两个“支撑”螺旋的功能。除了确定第二支架螺旋的完整性对于小鼠MLKL同源三聚体的组装和细胞死亡至关重要之外，我们还暗示支架螺旋作为将假激酶结构域磷酸化事件传递到N-末端执行器4 HB结构域的装置。使用鼠标：在人MLKL嵌合体中，我们将第一支撑螺旋和相邻环定义为分子开关机制的关键元件，所述分子开关机制将假激酶结构域磷酸化中继到4 HB结构域杀伤活性的激活。此外，我们的嵌合体数据揭示了假激酶结构域在赋予MLKL杀伤功能的宿主特异性方面的重要性，其中小鼠假激酶结构域的融合将人4 HB+支架从小鼠成纤维细胞的无活性转化为组成型杀伤。这些发现说明支撑螺旋在MLKL调节中发挥积极作用，而不是简单地充当4 HB和假激酶结构域之间的系链。
The programmed cell death pathway, necroptosis, relies on the pseudokinase, Mixed Lineage Kinase domain-Like (MLKL), for cellular execution downstream of death receptor or Toll-like receptor ligation. Receptor-interacting protein kinase-3 (RIPK3)-mediated phosphorylation of MLKL's pseudokinase domain leads to MLKL switching from an inert to activated state, where exposure of the N-terminal four-helix bundle (4HB) 'executioner' domain leads to cell death. The precise molecular details of MLKL activation, including the stoichiometry of oligomer assemblies, mechanisms of membrane translocation and permeabilisation, remain a matter of debate. Here, we dissect the function of the two 'brace' helices that connect the 4HB to the pseudokinase domain of MLKL. In addition to establishing that the integrity of the second brace helix is crucial for the assembly of mouse MLKL homotrimers and cell death, we implicate the brace helices as a device to communicate pseudokinase domain phosphorylation event(s) to the N-terminal executioner 4HB domain. Using mouse: human MLKL chimeras, we defined the first brace helix and adjacent loop as key elements of the molecular switch mechanism that relay pseudokinase domain phosphorylation to the activation of the 4HB domain killing activity. In addition, our chimera data revealed the importance of the pseudokinase domain in conferring host specificity on MLKL killing function, where fusion of the mouse pseudokinase domain converted the human 4HB + brace from inactive to a constitutive killer of mouse fibroblasts. These findings illustrate that the brace helices play an active role in MLKL regulation, rather than simply acting as a tether between the 4HB and pseudokinase domains.