Structure and function of the Smoothened extracellular domain in vertebrate Hedgehog signaling.
Structure and function of the Smoothened extracellular domain in vertebrate Hedgehog signaling.
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DOI：
10.7554/elife.01340
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发表时间：
2013-10-29
期刊：
影响因子：
7.7
通讯作者：
Rohatgi R
中科院分区：
文献类型：
--
作者：
Nachtergaele S;Whalen DM;Mydock LK;Zhao Z;Malinauskas T;Krishnan K;Ingham PW;Covey DF;Siebold C;Rohatgi R
Hedgehog (Hh) 信号由七螺旋蛋白 Smoothened (Smo) 跨膜转导，Smo 是一种发育调节因子、肿瘤蛋白和肿瘤学药物靶点。我们展示了脊椎动物 Smo 胞外富含半胱氨酸结构域 (CRD) 的 2.3 Å 晶体结构，并表明它与氧甾醇（激活 Hh 信号传导的内源脂质）结合。 Smo CRD 中的氧甾醇结合凹槽类似于 Frizzled 8 用于与 Wnt 配体的棕榈油基结合的凹槽，以及与其他 Frizzled 样 CRD 用于结合疏水性配体的类似口袋。 CRD 是响应天然 Hh 配体的信号传导所必需的，这表明它是 Smo 激活的重要调节模块。事实上，氧甾醇启发的小分子靶向 Smo CRD 可以阻断所有已知类别的 Hh 激活剂和临床相关 Smo 突变体的信号传导。 DOI：http://dx.doi.org/10.7554/eLife.01340.001 就在 30 多年前，研究人员发现了一种新的信号分子，在果蝇的发育中发挥着重要作用。缺乏这种分子的胚胎被认为类似于刺猬，最终导致这种细胞间通讯系统被指定为“刺猬”途径。随后该途径被证明参与许多其他动物的发育，以及成年生物体受损组织的修复。异常的刺猬信号传导也与人类出生缺陷以及皮肤癌和脑癌有关。许多此类肿瘤是由一种称为 Smoothened 的膜结合蛋白不受限制的激活驱动的，这导致了阻止 Hedgehog 激活 Smoothened 的小分子的开发和临床使用。现有的抗肿瘤药物都与 Smoothened 受体的同一区域结合，即位于细胞膜内的部分。第二组分子，称为氧甾醇，可以激活 Smoothened，但它们到底如何做到这一点尚不清楚。现在，Nachtergaele 等人。研究表明，氧甾醇与细胞外的 Smoothened 受体区域结合，该区域富含氨基酸半胱氨酸。 Nachtergaele 等人通过解析斑马鱼受体这部分的晶体结构。能够以高分辨率绘制氧甾醇结合位点图。这揭示了该结合位点与属于 Wnt 信号通路的相关受体中的结合位点之间的强烈相似性。删除富含半胱氨酸的结构域会显着损害 Hedgehog 信号传导，专门针对氧甾醇结合位点设计的新型小分子抑制剂也是如此。 Nachtergaele 等人的工作除了提供对 Smoothened 受体的结构和功能的新见解之外。开辟了新型治疗剂的可能性，可用于治疗由异常 Hedgehog 信号传导引起的癌症。 DOI：http://dx.doi.org/10.7554/eLife.01340.002
The Hedgehog (Hh) signal is transduced across the membrane by the heptahelical protein Smoothened (Smo), a developmental regulator, oncoprotein and drug target in oncology. We present the 2.3 Å crystal structure of the extracellular cysteine rich domain (CRD) of vertebrate Smo and show that it binds to oxysterols, endogenous lipids that activate Hh signaling. The oxysterol-binding groove in the Smo CRD is analogous to that used by Frizzled 8 to bind to the palmitoleyl group of Wnt ligands and to similar pockets used by other Frizzled-like CRDs to bind hydrophobic ligands. The CRD is required for signaling in response to native Hh ligands, showing that it is an important regulatory module for Smo activation. Indeed, targeting of the Smo CRD by oxysterol-inspired small molecules can block signaling by all known classes of Hh activators and by clinically relevant Smo mutants. DOI: http://dx.doi.org/10.7554/eLife.01340.001 Just over 30 years ago, researchers identified a new signaling molecule with an important role in the development of fruit flies. Embryos lacking this molecule were thought to resemble a hedgehog, eventually leading to this cell–cell communication system being designated the “Hedgehog” pathway. This pathway has subsequently been shown to be involved in the development of many other animals, as well as in the repair of damaged tissues in adult organisms. Abnormal Hedgehog signaling has also been implicated in both human birth defects and in cancers of the skin and the brain. Many such tumors are driven by the unrestrained activation of a membrane-bound protein called Smoothened, which has led to the development and clinical use of small molecules that prevent Hedgehog from activating Smoothened. The existing anti-tumor drugs all bind to the same region of the Smoothened receptor, namely the part that sits within the cell membrane. A second group of molecules, known as oxysterols, can activate Smoothened, but exactly how they do this has been unclear. Now, Nachtergaele et al. have shown that oxysterols bind to a region of the Smoothened receptor that lies outside the cell, and that is rich in the amino acid cysteine. By solving the crystal structure of this part of the receptor from zebrafish, Nachtergaele et al. were able to map the oxysterol binding site at high resolution. This revealed strong similarities between this binding site and those in related receptors belonging to the Wnt signaling pathway. Deleting the cysteine-rich domain significantly impaired Hedgehog signaling, as did a new class of small molecule inhibitors designed specifically to target the oxysterol binding site. In addition to providing new insights into the structure and function of the Smoothened receptor, the work of Nachtergaele et al. opens up possibilities for novel therapeutic agents that could be used in the treatment of cancers caused by abnormal Hedgehog signaling. DOI: http://dx.doi.org/10.7554/eLife.01340.002