Sending and receiving Hedgehog and Wnt signals

项目总结 Hedgehog(HH)和Wnt信号通路对于胚胎发育、成体干细胞是必不可少的 他们与癌症和出生缺陷有很深的关系。这两条通路都是由脂质激活的- 修饰的分泌配体：HH配体用棕榈酸酯和胆固醇修饰，而WNT配体用棕榈酸酯和胆固醇修饰 用棕榈酸酯修饰。脂化作用对于HH和WNT配体的功能是必不可少的，但它使它们粘在一起 它们强烈地扩散到膜上，引发了它们是如何从产生细胞扩散的问题。 我们发现HH是通过与专用载体形成稳定的络合物而从细胞中释放出来的 蛋白质，Scube，一个由被调度的膜转运蛋白催化的过程，它使用 质膜钠梯度。然后，Scube将HH传递给它的受体，即肿瘤抑制膜 蛋白质补丁，触发特定的细胞反应。我们发现，令人惊讶的是，Scube阻止了HH的结合 这引发了Scube-HH复合体如何激活信号的问题。我们发现有三个 细胞表面蛋白Cdon、Boc和Gas1是HH的共同受体，对Scube- HH。具体地说，我们证明了HH共受体定义了一种新的序列途径，通过这种途径，Cdon和 BOC将Scube-HH募集到细胞表面，之后Gas1催化HH从Scube到Patted的转移。我们 还用冷冻电子显微镜确定了Dispatted-HH和Gas1-HH-Patch的结构 络合物，分别在释放和释放过程中捕获HH。最后，我们发现了两个 作为WNTs载体的分泌蛋白家族，解释WNTs是如何以可溶性形式释放的 和主动形式。 我们的发现揭示了关于HH和WNT信号的几个关键问题。我们建议将 生物化学、结构、化学和细胞生物学，以实现以下目标： 1)确定Dispatted和Scube如何合作释放HH配体 2)阐明Gas1如何催化HH补丁复合体的形成，触发HH信号转导 3)阐明Wnt配体是如何分泌并递送到反应细胞的 这些研究之所以重要，是因为以下原因：a)它们将促进对HH的理解 和Wnt途径，通过阐明控制配体的关键途径；B)它们将识别新的靶点 阻断癌症中的信号，基于HH和Wnt配体释放和传递的机制；以及C)OUR 新型化学探针将广泛应用于研究胆固醇和脂肪酸对健康和疾病的影响。

Project summary The Hedgehog (Hh) and Wnt signaling pathways are essential for embryogenesis, adult stem cell maintenance, and are deeply involved in cancer and birth defects. Both pathways are activated by lipid- modified secreted ligands: Hh ligands are modified with palmitate and cholesterol, while Wnt ligands are modified with palmitate. Lipidation is essential for the function of Hh and Wnt ligands, but it makes them stick strongly to membranes, raising the question of how they spread from producing cells. We discovered that Hh is released from cells by forming a stable complex with a dedicated carrier protein, Scube, a process catalyzed by the membrane transporter Dispatched, which uses the energy of the plasma membrane sodium gradient. Scube then delivers Hh to its receptor, the tumor suppressor membrane protein Patched, triggering specific cellular responses. We found that, surprisingly, Scube blocks binding of Hh to Patched, raising the question of how the Scube-Hh complex activates signaling. We discovered that three cell surface proteins Cdon, Boc and Gas1, known as co-receptors for Hh, are essential for signaling by Scube- Hh. Specifically, we showed that the Hh co-receptors define a novel sequential pathway whereby Cdon and Boc recruit Scube-Hh to the cell surface, after which Gas1 catalyzes Hh transfer from Scube to Patched. We also used cryo-electron microscopy to determine the structure of Dispatched-Hh and Gas1-Hh-Patched complexes, which capture Hh in the process of release and delivery, respectively. Finally, we discovered two families of secreted proteins that function as carriers for Wnts, explaining how Wnts are released in soluble and active form. Our findings open several critical questions about Hh and Wnt signaling. We propose combining biochemistry, structural, chemical and cell biology to accomplish the following aims: 1) To determine how Dispatched and Scube cooperate to release Hh ligands 2) To elucidate how Gas1 catalyzes formation of the Hh-Patched complex, to trigger Hh signaling 3) To elucidate how Wnt ligands are secreted and then delivered to responding cells These studies are important for the following reasons: A) They will advance understanding of the Hh and Wnt pathways, by elucidating critical pathways controlling the ligands; B) They will identify novel targets for blocking signaling in cancer, based on the mechanisms of Hh and Wnt ligand release and delivery; and C) Our novel chemical probes will be broadly applicable to study cholesterol and fatty acids in health and in disease.