Sending and receiving Hedgehog signals

项目摘要 Hedgehog细胞-细胞信号传导通路对于胚胎发育、成体干细胞发育和胚胎干细胞发育都是必不可少的。 维持，并深深参与人类癌症和出生缺陷。该通路由 Hedgehog ligand是一种分泌型蛋白质，由两种脂质独特修饰，这两种脂质都是功能所必需的： 脂肪酸和胆固醇。Hedgehog配体从产生细胞扩散到远处的细胞， 它结合其受体的表面，一种称为Patched的肿瘤抑制膜蛋白，从而触发了一种 特定的细胞反应。Hedgehog配体的一个令人困惑的方面是，它在一个特定的位置传播和信号传递。 尽管它的脂质修饰使它强烈地粘附在膜上，但它仍然具有很大的距离。许多关键 Hedgehog配体的某些方面仍然不清楚：我们不知道它是如何从细胞中释放出来的，它如何能够 扩散到细胞外，以及它如何被传递到响应细胞。 我们最近发现Hedgehog配体的释放是通过两种协同作用完成的 包括其胆固醇修饰：一个与膜蛋白调度，第二个与 分泌蛋白Scube。使用新型化学探针，我们发现Dispatched和Scube识别 胆固醇不同，这表明刺猬配体是从调度移交给Scube。我们也 我发现Scube通过Cdon和Boc对配体的接收很重要，这两种蛋白质对Hedgehog至关重要 信号传导;这表明了Hedgehog配体递送的新机制。最后，我们发现Gas 1， 另一种对Hedgehog配体受体重要的蛋白质，以独特的方式与配体相互作用，依赖于 这表明Gas 1使用不同于Cdon和Boc的机制。 我们建议使用生物化学、细胞生物学和化学生物学的组合来完成 以下目标： A）为了精确地阐明Hedgehog配体如何从生产细胞的膜释放， B）为了确定Scube如何通过Cdon和Boc将Hedgehog配体递送至应答细胞 C）阐明Gas 1如何参与Hedgehog配体的接收 这些研究很重要，原因如下：1）它们将促进我们的 通过阐明Hedgehog配体在Hedgehog通路中所采取的途径， 2）他们将根据癌症中的Hedgehog信号传导过程，确定阻断Hedgehog信号传导的新靶点。 Hedgehog配体释放和递送的机制;以及3）我们的新型化学探针将被广泛应用于 适用于研究健康和疾病中的胆固醇和脂肪酸。

Project summary The Hedgehog cell-cell signaling pathway is essential for embryonic development, for adult stem cell maintenance, and is deeply involved in human cancer and birth defects. The pathway is activated by the Hedgehog ligand, a secreted protein uniquely modified with two lipids, which are both essential for function: a fatty acid and cholesterol. From the producing cell, the Hedgehog ligand spreads to distant cells, on the surface of which it binds its receptor, a tumor suppressor membrane protein called Patched, thus triggering a specific set of cellular responses. A puzzling aspect of the Hedgehog ligand is that it spreads and signals at a distance, in spite of the fact that its lipid modifications make it stick strongly to membranes. Many critical aspects of the Hedgehog ligand remain obscure: we do not know how it is released from cells, how it is able to diffuse outside the cell, and how it is delivered to responding cells. We recently discovered that Hedgehog ligand release is accomplished by two synergistic interactions involving its cholesterol modification: one with the membrane protein Dispatched, and the second with the secreted protein Scube. Using novel chemical probes, we found that Dispatched and Scube recognize cholesterol differently, suggesting that the Hedgehog ligand is handed off from Dispatched to Scube. We also discovered that Scube is important for ligand reception, via Cdon and Boc, two proteins critical for Hedgehog signaling; this suggested a novel mechanism for Hedgehog ligand delivery. Finally, we found that Gas1, another protein important for Hedgehog ligand reception, interacts with the ligand in a unique way, dependent on its fatty acid modification; this indicated that Gas1 uses a mechanism distinct from Cdon and Boc. We propose to use a combination of biochemistry, cell biology, and chemical biology to accomplish the following aims: A) To elucidate precisely how the Hedgehog ligand is released form the membrane of producing cells B) To determine how Scube delivers the Hedgehog ligand to responding cells via Cdon and Boc C) To elucidate how Gas1 participates in Hedgehog ligand reception These studies are important to undertake for the following reasons: 1) They will advance our understanding of the Hedgehog pathway, by elucidating the route taken by the Hedgehog ligand during the signaling process; 2) They will identify novel targets for blocking Hedgehog signaling in cancer, based on the mechanisms of Hedgehog ligand release and delivery; and 3) Our novel chemical probes will be broadly applicable to study cholesterol and fatty acids in health and in disease.