Wu Zhengliang L, Zhang Lijuan, Yabe Tomio, Kuberan B, Beeler David L, Love Andre, Rosenberg Robert D
Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Biol Chem. 2003 May 9;278(19):17121-9. doi: 10.1074/jbc.M212590200. Epub 2003 Feb 25.
Fibroblast growth factor (FGF) signaling begins with the formation of a ternary complex of FGF, FGF receptor (FGFR), and heparan sulfate (HS). Multiple models have been proposed for the ternary complex. However, major discrepancies exist among those models, and none of these models have evaluated the functional importance of the interacting regions on the HS chains. To resolve the discrepancies, we measured the size and molar ratio of HS in the complex and showed that both FGF1 and FGFR1 simultaneously interact with HS; therefore, a model of 2:2:2 FGF1.HS.FGFR1 was shown to fit the data. Using genetic and biochemical methods, we generated HSs that were defective in FGF1 and/or FGFR1 binding but could form the signaling ternary complex. Both genetically and chemically modified HSs were subsequently assessed in a BaF3 cell mitogenic activity assay. The ability of HS to support the ternary complex formation was found to be required for FGF1-stimulated cell proliferation. Our data also proved that specific critical groups and sites on HS support complex formation. Furthermore, the molar ratio of HS, FGF1, and FGFR1 in the ternary complex was found to be independent of the size of HS, which indicates that the selected model can take place on the cell surface proteoglycans. Finally, a mechanism for the FGF.FGFR signaling complex formation on cell membrane was proposed, where FGF and FGFR have their own binding sites on HS and a distinct ternary complex formation site is directly responsible for mitogenic activity.
成纤维细胞生长因子（FGF）信号传导始于FGF、FGF受体（FGFR）和硫酸乙酰肝素（HS）形成三元复合物。关于该三元复合物已提出多种模型。然而，这些模型之间存在重大差异，且没有一个模型评估过HS链上相互作用区域的功能重要性。为了解决这些差异，我们测量了复合物中HS的大小和摩尔比，结果表明FGF1和FGFR1均能同时与HS相互作用；因此，2:2:2的FGF1.HS.FGFR1模型被证明符合数据。我们使用遗传学和生物化学方法生成了在FGF1和/或FGFR1结合方面存在缺陷但能形成信号三元复合物的HS。随后在BaF3细胞促有丝分裂活性测定中对经过基因和化学修饰的HS进行了评估。发现HS支持三元复合物形成的能力是FGF1刺激细胞增殖所必需的。我们的数据还证明了HS上特定的关键基团和位点支持复合物形成。此外，发现三元复合物中HS、FGF1和FGFR1的摩尔比与HS的大小无关，这表明所选择的模型可以在细胞表面蛋白聚糖上发生。最后，提出了一种细胞膜上FGF.FGFR信号复合物形成的机制，其中FGF和FGFR在HS上有各自的结合位点，一个独特的三元复合物形成位点直接负责促有丝分裂活性。
