From the Department of Medical Genome Science, School of Frontier Sciences, and.
From the Department of Medical Genome Science, School of Frontier Sciences, and; The Institute of Medical Science, The University of Tokyo, Kashiwa 277-8562 and.
J Biol Chem. 2011 Mar 11;286(10):8085-8093. doi: 10.1074/jbc.M110.152561. Epub 2010 Dec 7.
Human interleukin-11 (hIL-11) is a pleiotropic cytokine administered to patients with low platelet counts. From a structural point of view hIL-11 belongs to the long-helix cytokine superfamily, which is characterized by a conserved core motif consisting of four α-helices. We have investigated the region of hIL-11 that does not belong to the α-helical bundle motif, and that for the purpose of brevity we have termed "non-core region." The primary sequence of the interleukin was altered at various locations within the non-core region by introducing glycosylation sites. Functional consequences of these modifications were examined in cell-based as well as biophysical assays. Overall, the data indicated that the non-core region modulates the function of hIL-11 in two ways. First, the majority of muteins displayed enhanced cell-stimulatory properties (superagonist behavior) in a glycosylation-dependent manner, suggesting that the non-core region is biologically designed to limit the full potential of hIL-11. Second, specific modification of a predicted mini α-helix led to cytokine inactivation, demonstrating that this putative structural element belongs to site III engaging a second copy of cell-receptor gp130. These findings have unveiled new and unexpected elements modulating the biological activity of hIL-11, which may be exploited to develop more versatile medications based on this important cytokine.
人白细胞介素-11（hIL-11）是一种用于治疗血小板计数低的患者的多效细胞因子。从结构角度来看，hIL-11 属于长螺旋细胞因子超家族，其特征是由四个α螺旋组成的保守核心基序。我们研究了不属于α螺旋束基序的 hIL-11 区域，为了简洁起见，我们将其称为“非核心区域”。在非核心区域的各个位置通过引入糖基化位点改变了白细胞介素的一级序列。在基于细胞的和生物物理测定中检查了这些修饰的功能后果。总体而言，数据表明，非核心区域以两种方式调节 hIL-11 的功能。首先，大多数无义突变显示出增强的细胞刺激特性（超级激动剂行为），这表明非核心区域在生物学上被设计用来限制 hIL-11 的全部潜力。其次，对预测的小型α螺旋的特定修饰导致细胞因子失活，表明该假定的结构元件属于与细胞受体 gp130 的第二个拷贝结合的第三位点。这些发现揭示了调节 hIL-11 生物学活性的新的和意外的因素，这可能被利用来开发基于这种重要细胞因子的更通用的药物。
