Mechanism and Regulation of STRIPAKâSLMAP in Hippo Signaling

项目摘要 动态蛋白质磷酸化调节几乎所有的生物过程。选择性去磷酸化 特定底物或给定底物上的特定位点对于关键细胞事件是关键的。我们最近的研究 发现了一个不寻常的例子，位点特异性去磷酸化的多亚基纹状体相互作用 磷酸酶和激酶复合物，称为STRIPAK，其控制Hippo途径激活。hippo途径 对于多细胞生物体中的组织稳态和肿瘤抑制至关重要。该途径的失调 在苍蝇、老鼠和人类体内形成肿瘤。通过细胞表面受体和细胞骨架复合体 (e.g. NF2），细胞外信号，包括细胞-细胞接触，激活由Hippo 激酶MST 1/2、NDR家族激酶LATS 1/2和衔接蛋白SAV1和MOB 1。激活 LATS 1/2磷酸化并阻止转录因子雅普/TAZ的核积累。当 当Hippo通路关闭时，雅普/TAZ易位到细胞核中并与细胞核形成功能性杂合转录因子。 TEAD促进增殖和促存活基因的转录。MST1/2的激活启动Hippo 信号传导并需要T环中的反式自磷酸化（MST2 T180）。我们最近发现， PP 2A复合物STRIPAK通过反馈抑制来阻断MST 2激活。活性MST 2自磷酸化 连接器中的多个位点。STRIPAK中的接头蛋白SLMAP结合磷酸连接体并促进 MST2 pT180去磷酸化，从而确保低稳态MST2活化。SAV1促进MST2 通过抑制STRIPAKSLMAP介导的MST2 pT180的去磷酸化来激活。生理 STRIPAKSLMAP的功能、调节和作用机制尚未解决。我们假设 STRIPAKSLMAP通过SAV1集成上游输入，以控制MST 1/2激活。因为 STRIPAKSLMAP含有激酶和磷酸酶，在相反的催化作用之间保持微妙的平衡。 同一复合物中两种酶的活性可能在切换激活状态中起关键作用。 河马信号。因此，了解STRIPAKSLMAP的结构、组装机制和调控， 对于最终理解核心Hippo通路如何受上游信号调节至关重要。这 该提案旨在确定这种相反调节的分子机制和结构基础， 通过SAV1和STRIPAKSLMAP分析海马激酶MST1/2，并分析其结构、组装机制和 在Hippo信号传导的背景下调节STRIPAKSLMAP。这项研究将大大促进我们的 对Hippo信号网络调节的基本理解，并可能揭示新的方法， 利用Hippo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.