Salvati A L, Lahm A, Paonessa G, Ciliberto G, Toniatti C
Department of Genetics, Istituto di Ricerche di Biologia Molecolare P. Angeletti, Rome, Italy.
J Biol Chem. 1995 May 19;270(20):12242-9. doi: 10.1074/jbc.270.20.12242.
Interleukin-6 (IL-6) triggers the formation of a high affinity receptor complex constituted by the ligand-binding subunit IL-6 receptor alpha (IL-6R alpha) and the signal-transducing beta chain gp130. Since the cytoplasmic region of IL-6R alpha is not required for signal transduction, soluble forms of IL-6R alpha (sIL-6R alpha) show agonistic properties because they are still able to originate IL-6.sIL-6R alpha complexes, which in turn associate with gp130. A three-dimensional model of the human IL-6.IL-6R alpha.gp130 complex has been constructed and verified by site-directed mutagenesis of regions in shIL-6R alpha (where "h" is human) anticipated to contact hgp130, with the final goal of generating receptor variants with antagonistic properties. In good agreement with our structural model, substitutions at Asn-230, His-280, and Asp-281 selectively impaired the capability of shIL-6R alpha to associate with hgp130 both in vitro and on the cell surface, without affecting its affinity for hIL-6. Moreover, the multiple substitution mutant A228D/N230D/H280S/D281V expressed as a soluble protein partially antagonized hIL-6 bioactivity on hepatoma cells.
白细胞介素-6（IL-6）触发由配体结合亚基白细胞介素-6受体α（IL-6Rα）和信号转导β链gp130构成的高亲和力受体复合物的形成。由于信号转导不需要IL-6Rα的胞质区域，可溶性形式的IL-6Rα（sIL-6Rα）具有激动特性，因为它们仍然能够形成IL-6.sIL-6Rα复合物，进而与gp130结合。已构建人IL-6.IL-6Rα.gp130复合物的三维模型，并通过对预计与hgp130接触的shIL-6Rα（“h”代表人）区域进行定点诱变进行了验证，最终目标是生成具有拮抗特性的受体变体。与我们的结构模型高度一致，Asn-230、His-280和Asp-281处的取代在体外和细胞表面均选择性地损害了shIL-6Rα与hgp130结合的能力，而不影响其对hIL-6的亲和力。此外，作为可溶性蛋白表达的多取代突变体A228D/N230D/H280S/D281V部分拮抗了hIL-6对肝癌细胞的生物活性。
