Ancient MAPK ERK7 is regulated by an unusual inhibitory scaffold required for Toxoplasma apical complex biogenesis
Ancient MAPK ERK7 is regulated by an unusual inhibitory scaffold required for Toxoplasma apical complex biogenesis
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DOI：
10.1073/pnas.1921245117
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发表时间：
2020-06-02
影响因子：
11.1
通讯作者：
Reese, Michael L.
中科院分区：
文献类型：
--
作者：
Back, Peter S.;O'Shaughnessy, William J.;Reese, Michael L.
顶复门寄生虫使用一种称为顶复体的特殊纤毛结构来组织它们的分泌细胞器和入侵机器。顶端复合体与寄生虫质膜和称为内膜复合体（IMC）的中间丝细胞骨架整体相关。虽然顶端复合体是必不可少的寄生生活方式，很少有人知道顶端复合体生物发生的调节。在这里，我们确定AC 9（顶端帽蛋白9），弓形虫IMC的主要内在无序的组成部分，顶端复杂的发展，因此宿主细胞的入侵和出口是必不可少的。缺乏AC 9的寄生虫不能成功地组装其顶端复合物的富含微管蛋白的核心，称为圆锥体。我们使用邻近生物素化来识别AC 9相互作用网络，其中包括激酶细胞外信号调节激酶7（ERK 7）。与AC 9一样，ERK 7是顶端复合体生物发生所必需的。我们证明AC 9通过保守的C-末端基序直接结合ERK 7，这种相互作用对于ERK 7在顶帽的定位和功能是必不可少的。ERK 7-AC 9复合物的晶体结构表明，AC 9不仅是一种支架，而且通过一组不寻常的接触来抑制ERK 7，该接触从激酶活性位点置换核苷酸。ERK 7是丝裂原活化激酶（MAPK）家族的一个古老的自活化成员，其调节在所有生物体中知之甚少。我们认为AC 9通过支架和将其集中在其作用位点，同时保持其处于“关闭”状态，直到与真正的底物特异性结合来双重调节ERK 7。
Apicomplexan parasites use a specialized cilium structure called the apical complex to organize their secretory organelles and invasion machinery. The apical complex is integrally associated with both the parasite plasma membrane and an intermediate filament cytoskeleton called the inner-membrane complex (IMC). While the apical complex is essential to the parasitic lifestyle, little is known about the regulation of apical complex biogenesis. Here, we identify AC9 (apical cap protein 9), a largely intrinsically disordered component of the Toxoplasma gondii IMC, as essential for apical complex development, and therefore for host cell invasion and egress. Parasites lacking AC9 fail to successfully assemble the tubulin-rich core of their apical complex, called the conoid. We use proximity biotinylation to identify the AC9 interaction network, which includes the kinase extracellular signal-regulated kinase 7 (ERK7). Like AC9, ERK7 is required for apical complex biogenesis. We demonstrate that AC9 directly binds ERK7 through a conserved C-terminal motif and that this interaction is essential for ERK7 localization and function at the apical cap. The crystal structure of the ERK7-AC9 complex reveals that AC9 is not only a scaffold but also inhibits ERK7 through an unusual set of contacts that displaces nucleotide from the kinase active site. ERK7 is an ancient and autoactivating member of the mitogen-activated kinase (MAPK) family and its regulation is poorly understood in all organisms. We propose that AC9 dually regulates ERK7 by scaffolding and concentrating it at its site of action while maintaining it in an "off" state until the specific binding of a true substrate.