Mechanism and Regulation of STRIPAKâSLMAP in Hippo Signaling

项目摘要 动态的蛋白质磷酸化几乎调节了所有的生物过程。选择性去磷酸化 特定底物或特定底物上的特定位置对关键细胞事件至关重要。我们最近的研究表明 发现了一个不寻常的由多亚基Striatin相互作用的位点特异性去磷酸化的例子 磷酸酶和激酶复合体称为STRIPAK，控制河马途径的激活。河马小路 对多细胞生物体的组织稳态和肿瘤抑制至关重要。这一途径的失调 在苍蝇、小鼠和人类体内导致肿瘤形成。通过细胞表面受体和细胞骨架复合体 (例如，NF2)，细胞外信号，包括细胞-细胞接触，激活河马形成的核心激酶级联 蛋白激酶MST1/2、NDR家族蛋白LATS1/2以及接头蛋白SAV1和MOB1。已激活 LATS1/2磷酸化并阻止转录因子YAP/TAZ的核积聚。当 河马途径关闭，YAP/TAZ转位到细胞核，形成功能性杂交转录因子 促进增殖和促进生存基因转录的TEADS。MST1/2激活启动河马 信号转导，需要在T-环(MST2 T180)中反式自动磷酸化。我们最近已经表明， PP2A复合体STRIPAK通过反馈抑制阻断MST2的激活。活性MST2自动磷酸化 链接器中有多个站点。STRIPAK中的接头蛋白SLMAP与磷酸化连接物结合并促进 MST2 pT180去磷酸化，从而确保低稳态MST2激活。SAV1促进MST2 通过抑制STRIPAKSLMAP介导的MST2 pT180去磷酸化而激活。生理学 STRIPAKSLMAP的功能、调控和作用机制尚不清楚。我们假设 STRIPAKSLMAP通过SAV1集成上游输入，以控制MST1/2激活。因为 STRIPAKSLMAP同时含有一种激酶和一种磷酸酶，在相反的催化作用之间的微妙平衡 同一复合体中两种酶的活性可能在切换酶的激活状态中起关键作用 河马信号。因此，了解STRIPAKSLMAP的体系结构、组装机制和调节 对于最终理解核心河马通路是如何受上游信号调控至关重要的。这 该提案旨在确定这一对立调控的分子机制和结构基础 河马通过SAV1和STRIPAKSLMAP激活MST1/2，并对MST1/2的结构、组装机制和 在河马信号背景下对STRIPAKSLMAP的调节。这项研究将大大推进我们的 对河马信令网络的调节有基本的了解，并可能发现 利用河马通路中的缺陷来治疗人类疾病。

Project Summary Dynamic protein phosphorylation regulates virtually all biological processes. Selective dephosphorylation of specific substrates or specific sites on a given substrate is critical for key cellular events. Our recent studies have uncovered an unusual example of site-specific dephosphorylation by the multi-subunit Striatin-interacting phosphatase and kinase complex called STRIPAK, which controls Hippo pathway activation. The Hippo pathway is critical for tissue homeostasis and tumor suppression in multicellular organisms. Dysregulation of this pathway drives tumor formation in flies, mice, and humans. Through cell-surface receptors and cytoskeletal complexes (e.g. NF2), extracellular signals, including cell-cell contact, activate a core kinase cascade formed by the Hippo kinases MST1/2, the NDR family kinases LATS1/2, and the adaptor proteins SAV1 and MOB1. Activated LATS1/2 phosphorylate and prevent the nuclear accumulation of the transcription factors YAP/TAZ. When the Hippo pathway is off, YAP/TAZ translocate to the nucleus and form functional hybrid transcriptional factors with TEADs to promote the transcription of proliferative and pro-survival genes. Activation of MST1/2 initiates Hippo signaling and requires trans-autophosphorylation in the T-loop (MST2 T180). We have recently shown that the PP2A complex STRIPAK blocks MST2 activation through feedback inhibition. Active MST2 auto-phosphorylates multiple sites in the linker. The adaptor protein SLMAP in STRIPAK binds the phospho-linker and promotes MST2 pT180 dephosphorylation, thus ensuring low steady-state MST2 activation. SAV1 promotes MST2 activation by suppressing STRIPAKSLMAP-mediated dephosphorylation of MST2 pT180. The physiological function, regulation, and mechanism of action of STRIPAKSLMAP remain unresolved. We hypothesize that STRIPAKSLMAP integrates upstream inputs through SAV1 to control MST1/2 activation. Because STRIPAKSLMAP contains both a kinase and a phosphatase, the delicate balance between the opposite catalytic activities of the two enzymes in the same complex may play a critical role in toggling the activation status of Hippo signaling. Thus, understanding the architecture, assembly mechanism, and regulation of STRIPAKSLMAP is crucial to the eventual understanding of how the core Hippo pathway is regulated by upstream signals. This proposal aims to determine the molecular mechanism and structural basis of this opposing regulation of the Hippo kinases MST1/2 by SAV1 and STRIPAKSLMAP, and to dissect the architecture, assembly mechanism, and regulation of STRIPAKSLMAP in the context of Hippo signaling. This research will significantly advance our fundamental understanding of the regulation of the Hippo signaling network and may uncover novel ways of exploiting defects in the Hippo pathway to treat human diseases.