Bitard Juliette, Daburon Sophie, Duplomb Laurence, Blanchard Frédéric, Vuisio Patricia, Jacques Yannick, Godard Anne, Heath John K, Moreau Jean-François, Taupin Jean-Luc
CNRS UMR 5540, Université de Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux, France.
J Biol Chem. 2003 May 2;278(18):16253-61. doi: 10.1074/jbc.M207193200. Epub 2003 Feb 24.
The leukemia inhibitory factor (LIF) receptor comprises the low affinity binding chain gp190 and the high affinity converter gp130. The ectodomain of gp190 is among the most complex in the hematopoietin receptor family, because it contains two typical cytokine receptor homology domains separated by an immunoglobulin-like (Ig-like) domain. Human and murine gp190 proteins share 76% homology, but murine gp190 binds human LIF with a much higher affinity, a property attributed to the Ig-like domain. Using alanine-scanning mutagenesis of the Ig-like domain, we mapped a LIF binding site at its carboxyl terminus, mainly involving residue Phe-328. Mutation of selected residues into their orthologs in the murine receptor (Q251E and N321D) significantly increased the affinity for human LIF. Interestingly, these residues, although localized at both the amino and carboxyl terminus, make a spatially unique LIF binding site in a structural model of the Ig-like module. These results demonstrate definitively the role of the Ig-like domain in LIF binding and the potential to modulate receptor affinity in this family with very limited amino acid changes.
白血病抑制因子（LIF）受体由低亲和力结合链gp190和高亲和力转换链gp130组成。gp190的胞外结构域是造血因子受体家族中最为复杂的结构域之一，因为它包含两个典型的细胞因子受体同源结构域，中间由一个免疫球蛋白样（Ig样）结构域隔开。人和小鼠的gp190蛋白具有76%的同源性，但小鼠的gp190与人LIF的结合亲和力要高得多，这一特性归因于Ig样结构域。通过对Ig样结构域进行丙氨酸扫描诱变，我们在其羧基末端定位了一个LIF结合位点，主要涉及苯丙氨酸-328残基。将选定残基突变为小鼠受体中的对应残基（Q251E和N321D）显著提高了对人LIF的亲和力。有趣的是，这些残基虽然位于氨基末端和羧基末端，但在Ig样模块的结构模型中形成了一个空间上独特的LIF结合位点。这些结果明确证明了Ig样结构域在LIF结合中的作用，以及通过非常有限的氨基酸变化来调节该家族受体亲和力的潜力。
