Understanding Signaling by Non-Canonical Receptor Tyrosine Kinases

米拉更新申请中提出的研究试图了解跨膜的机制 受体酪氨酸激酶(RTK)超家族成员和其他受体样激酶的信号- 这并不符合解释大多数RTK的“规则”。这一组中的非典型受体在 人类疾病--从神经发育障碍到骨骼疾病、癌症和先天性 畸形。传统的RTK信号模型涉及配体诱导的受体二聚化，这是 促进受体的酪氨酸自动磷酸化和下游信号分子的募集。AS 我们对58个人类RTK有了更多的了解，很明显，这个机制只适用于大约 他们中的一半。例如，10%的人类RTK连接到WNT信令，并且必须以不同的方式发挥作用 因为它们的胞内区通常只有催化不活跃的“假激酶”结构域。还有其他 RTK(如ALK)具有独特的胞外区，其配体结合和受体调节是 人们对此知之甚少。我们在理解细胞外和细胞内方面取得了重大进展 WNT调控的假激酶RTKs的结构。它们的胞外WNT结合模块明显不同 与参与WNT信号转导的蛋白质中的同种蛋白质不同，其方式表明 这些RTK如何与Frizzleed受体共同参与b-连环蛋白的假说 独立的WNT信令。RTK的细胞内假激酶结构域在结构上类似于 胰岛素受体激酶的非活性构象，对其结构动力学的分析表明 它们可以经历与正常酪氨酸相同的“类非活性”到“类活性”构象转变 激活域。事实上，我们已经发现，小分子激酶可以促进这些转变。 抑制物类分子，尽管分离的假激酶域不与ATP结合。在下一个 在这个项目的5-10年里，我们建议测试WNT诱导的受体复合体组装的假设 其结合了伪激酶RTK，阐明了它们对WNT特异性依赖和对WNT酰化的依赖， 通过结晶学和EM获得高分辨率的结构图，并分析它们的信号特性。 我们将测试假说，假性激活域是如何影响信号传递的--或者通过获取激活素 活动或作为变构可切换的交互平台，在其他 假性肌动蛋白和催化活性的肌动蛋白，如极光A。 探索PTK7、ROR1、ROR2、PTK7、ROR2、 和RYK，它们都与许多疾病有牵连。总之，这些研究将提供重要的 对RTK或WNT受体不符合正常模式的受体信号的新见解。新的 经验教训也应该适用于与疾病有关的其他类别的受体样激酶，开启了新的 潜在治疗抑制的途径。

The research proposed in this MIRA renewal application seeks to understand mechanisms of transmembrane signaling by members of the receptor tyrosine kinase (RTK) superfamily – and other receptor-like kinases – that do not fit the ‘rules’ that explain most RTKs. Non-canonical receptors in this group play important roles in human disease – from neurodevelopmental disorders, to bone diseases, cancers, and congenital malformations. The traditional model for RTK signaling involves ligand-induced receptor dimerization, which promotes tyrosine autophosphorylation of the receptor and recruitment of downstream signaling molecules. As we understand more about the 58 human RTKs, it has become clear that this mechanism only applies to about half of them. For example, 10% of human RTKs are linked to WNT signaling, and must function differently because their intracellular regions often have only catalytically inactive ‘pseudokinase’ domains. Still other RTKs (such as ALK) have unique extracellular regions for which ligand binding and receptor regulation are poorly understood. We have made significant progress in understanding extracellular and intracellular structures of WNT-regulated pseudokinase RTKs. Their extracellular WNT-binding modules differ significantly from their counterparts in proteins involved in ‘canonical’ WNT signaling, in ways that suggest well-defined hypotheses for how these RTKs might participate as co-receptors with Frizzled receptors in b-catenin independent WNT signaling. The intracellular pseudokinase domains of the RTKs structurally resemble the insulin receptor kinase in its ‘inactive’ conformation, and analysis of their structural dynamics suggests that they can undergo the same ‘inactive-like’ to ‘active-like’ conformational transitions seen for normal tyrosine kinase domains. Indeed, we have found that these transitions can be promoted by small molecule kinase inhibitor-like molecules, despite the fact that the isolated pseudokinase domains do not bind ATP. In the next 5-10 years of this project, we propose to test hypotheses for WNT-induced assembly of receptor complexes that incorporate pseudokinase RTKs, elucidate their specific WNT dependence and reliance on WNT acylation, gain high resolution structural views through crystallography and EM, and analyze their signaling properties. We will test hypotheses for how the pseudokinase domains contribute to signaling – either by acquiring kinase activity or by functioning as allosterically switchable interaction platforms, with precedents in other pseudokinases and in catalytically active kinases such as Aurora A. In parallel with these efforts, we will investigate new opportunities for therapeutic targeting of pseudokinase RTKs such as PTK7, ROR1, ROR2, and RYK, which have all been implicated in numerous diseases. Together, these studies will provide important new insight into signaling by receptors that do not fit normal paradigms for RTKs or WNT receptors. The new lessons should also be applicable to other classes of receptor-like kinases implicated in disease, opening new avenues for potential therapeutic inhibition.