Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California, USA.
Nat Immunol. 2012 Dec;13(12):1187-95. doi: 10.1038/ni.2449. Epub 2012 Oct 28.
Interleukin 15 (IL-15) and IL-2 have distinct immunological functions even though both signal through the receptor subunit IL-2Rβ and the common γ-chain (γ(c)). Here we found that in the structure of the IL-15-IL-15Rα-IL-2Rβ-γ(c) quaternary complex, IL-15 binds to IL-2Rβ and γ(c) in a heterodimer nearly indistinguishable from that of the IL-2-IL-2Rα-IL-2Rβ-γ(c) complex, despite their different receptor-binding chemistries. IL-15Rα substantially increased the affinity of IL-15 for IL-2Rβ, and this allostery was required for IL-15 trans signaling. Consistent with their identical IL-2Rβ-γ(c) dimer geometries, IL-2 and IL-15 showed similar signaling properties in lymphocytes, with any differences resulting from disparate receptor affinities. Thus, IL-15 and IL-2 induced similar signals, and the cytokine specificity of IL-2Rα versus IL-15Rα determined cellular responsiveness. Our results provide new insights for the development of specific immunotherapeutics based on IL-15 or IL-2.
白细胞介素 15(IL-15)和白细胞介素 2(IL-2)具有不同的免疫学功能,尽管它们都通过受体亚基 IL-2Rβ和共同的 γ 链(γ(c))发出信号。在这里,我们发现,在 IL-15-IL-15Rα-IL-2Rβ-γ(c) 四元复合物的结构中,IL-15 与 IL-2Rβ和 γ(c)结合的方式与 IL-2-IL-2Rα-IL-2Rβ-γ(c)复合物几乎无法区分,尽管它们的受体结合化学性质不同。IL-15Rα 大大增加了 IL-15 与 IL-2Rβ 的亲和力,这种变构作用对于 IL-15 的跨信号传递是必需的。与它们相同的 IL-2Rβ-γ(c)二聚体几何形状一致,IL-2 和 IL-15 在淋巴细胞中表现出相似的信号转导特性,任何差异都源于受体亲和力的不同。因此,IL-15 和 IL-2 诱导相似的信号,而 IL-2Rα 与 IL-15Rα 的细胞因子特异性决定了细胞的反应性。我们的研究结果为基于 IL-15 或 IL-2 的特异性免疫治疗的发展提供了新的见解。