Morlot Cecile, Thielens Nicole M, Ravelli Raimond B G, Hemrika Wieger, Romijn Roland A, Gros Piet, Cusack Stephen, McCarthy Andrew A
European Molecular Biology Laboratory, 6 Rue Jules Horowitz, BP 181, 38042 Grenoble, France.
Proc Natl Acad Sci U S A. 2007 Sep 18;104(38):14923-8. doi: 10.1073/pnas.0705310104. Epub 2007 Sep 11.
Slits are large multidomain leucine-rich repeat (LRR)-containing proteins that provide crucial guidance cues in neuronal and vascular development. More recently, Slits have been implicated in heart morphogenesis, angiogenesis, and tumor metastasis. Slits are ligands for the Robo (Roundabout) receptors, which belong to the Ig superfamily of transmembrane signaling molecules. The Slit-Robo interaction is mediated by the second LRR domain of Slit and the two N-terminal Ig domains of Robo, but the molecular details of this interaction and how it induces signaling remain unclear. Here we describe the crystal structures of the second LRR domain of human Slit2 (Slit2 D2), the first two Ig domains of its receptor Robo1 (Ig1-2), and the minimal complex between these proteins (Slit2 D2-Robo1 Ig1). Slit2 D2 binds with its concave surface to the side of Ig1 with electrostatic and hydrophobic contact regions mediated by residues that are conserved in other family members. Surface plasmon resonance experiments and a mutational analysis of the interface confirm that Ig1 is the primary domain for binding Slit2. These structures provide molecular insight into Slit-Robo complex formation and will be important for the development of novel cancer therapeutics.
Slit是一类含有多个结构域且富含亮氨酸重复序列（LRR）的蛋白质，在神经元和血管发育过程中提供关键的导向信号。最近，Slit还与心脏形态发生、血管生成和肿瘤转移有关。Slit是Roundabout（Robo）受体的配体，Robo受体属于跨膜信号分子的免疫球蛋白超家族。Slit与Robo的相互作用由Slit的第二个LRR结构域和Robo的两个N端免疫球蛋白结构域介导，但这种相互作用的分子细节以及它如何诱导信号传导仍不清楚。在此，我们描述了人Slit2的第二个LRR结构域（Slit2 D2）、其受体Robo1的前两个免疫球蛋白结构域（Ig1-2）以及这些蛋白之间的最小复合物（Slit2 D2-Robo1 Ig1）的晶体结构。Slit2 D2通过其凹面与Ig1的侧面结合，通过其他家族成员中保守的残基介导静电和疏水接触区域。表面等离子体共振实验和界面的突变分析证实Ig1是与Slit2结合的主要结构域。这些结构为Slit-Robo复合物的形成提供了分子层面的见解，对新型癌症治疗药物的开发具有重要意义。
