The Scribble (Scrib) protein is a conserved cell polarity regulator with anti-tumorigenic properties. Viruses like the Tick-born encephalitis virus (TBEV) target Scribble to establish a cellular environment supporting viral replication, which is ultimately associated with poor prognosis upon infection. The TBEV NS5 protein has been reported to harbour both an internal as well as a C-terminal PDZ binding motif (PBM), however only the internal PBM was shown to be an interactor with Scribble, with the interaction being mediated via the Scribble PDZ4 domain to antagonize host interferon responses. We examined the NS5 PBM motif interactions with all Scribble PDZ domains using isothermal titration calorimetry, which revealed that the proposed internal PBM did not interact with any Scribble PDZ domains. Instead, the C-terminal PBM of NS5 interacted with Scrib PDZ3. We then established the structural basis of these interactions by determining crystal structures of Scrib PDZ3 bound to the NS5 C-terminal PBM. Our findings provide a structural basis for Scribble PDZ domain and TBEV NS5 interactions and provide a platform to dissect the pathogenesis of TBEV and the role of cell polarity signalling using structure guided approaches.

中文翻译：

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Tick Born 脑炎病毒 NS5 介导的顶基底细胞极性信号颠覆的分子基础

Scribble (Scrib) 蛋白是一种保守的细胞极性调节剂，具有抗肿瘤发生特性。蜱传脑炎病毒 (TBEV) 等病毒以 Scribble 为目标，以建立支持病毒复制的细胞环境，这最终与感染后的不良预后有关。据报道，TBEV NS5 蛋白具有内部和 C 端 PDZ 结合基序 (PBM)，但只有内部 PBM 被证明是与 Scribble 的相互作用物，相互作用是通过 Scribble PDZ4 结构域介导的拮抗宿主干扰素反应。我们使用等温滴定量热法检查了 NS5 PBM 基序与所有 Scribble PDZ 域的相互作用，这表明所提出的内部 PBM 不与任何 Scribble PDZ 域相互作用。反而，NS5 的 C 端 PBM 与 Scrib PDZ3 相互作用。然后，我们通过确定与 NS5 C 端 PBM 结合的 Scrib PDZ3 的晶体结构来建立这些相互作用的结构基础。我们的研究结果为 Scribble PDZ 结构域和 TBEV NS5 相互作用提供了结构基础，并为使用结构引导方法剖析 TBEV 的发病机制和细胞极性信号传导的作用提供了一个平台。