Jackson Verity A, Mehmood Shahid, Chavent Matthieu, Roversi Pietro, Carrasquero Maria, Del Toro Daniel, Seyit-Bremer Goenuel, Ranaivoson Fanomezana M, Comoletti Davide, Sansom Mark S P, Robinson Carol V, Klein Rüdiger, Seiradake Elena
Department of Biochemistry, Oxford University, Oxford OX1 3QU, UK.
Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK.
Nat Commun. 2016 Apr 19;7:11184. doi: 10.1038/ncomms11184.
Latrophilin adhesion-GPCRs (Lphn1-3 or ADGRL1-3) and Unc5 cell guidance receptors (Unc5A-D) interact with FLRT proteins (FLRT1-3), thereby promoting cell adhesion and repulsion, respectively. How the three proteins interact and function simultaneously is poorly understood. We show that Unc5D interacts with FLRT2 in cis, controlling cell adhesion in response to externally presented Lphn3. The ectodomains of the three proteins bind cooperatively. Crystal structures of the ternary complex formed by the extracellular domains reveal that Lphn3 dimerizes when bound to FLRT2:Unc5, resulting in a stoichiometry of 1:1:2 (FLRT2:Unc5D:Lphn3). This 1:1:2 complex further dimerizes to form a larger 'super-complex' (2:2:4), using a previously undescribed binding motif in the Unc5D TSP1 domain. Molecular dynamics simulations, point-directed mutagenesis and mass spectrometry demonstrate the stability and molecular properties of these complexes. Our data exemplify how receptors increase their functional repertoire by forming different context-dependent higher-order complexes.
促胃液素释放肽受体黏附型G蛋白偶联受体（Lphn1 - 3或ADGRL1 - 3）和Unc5细胞导向受体（Unc5A - D）与FLRT蛋白（FLRT1 - 3）相互作用，分别促进细胞黏附和排斥。这三种蛋白如何同时相互作用并发挥功能，目前还知之甚少。我们发现，Unc5D与FLRT2顺式相互作用，响应细胞外呈现的Lphn3来控制细胞黏附。这三种蛋白的胞外域协同结合。由细胞外域形成的三元复合物的晶体结构表明，Lphn3与FLRT2:Unc5结合时会二聚化，形成1:1:2（FLRT2:Unc5D:Lphn3）的化学计量比。这种1:1:2复合物利用Unc5D TSP1结构域中一个此前未描述的结合基序进一步二聚化，形成更大的“超级复合物”（2:2:4）。分子动力学模拟、定点诱变和质谱分析证明了这些复合物的稳定性和分子特性。我们的数据例证了受体如何通过形成不同的、依赖于环境的高阶复合物来增加其功能组合。
