Monahan J, Siegel N, Keith R, Caparon M, Christine L, Compton R, Cusik S, Hirsch J, Huynh M, Devine C, Polazzi J, Rangwala S, Tsai B, Portanova J
Department of Inflammatory Diseases Research, G. D. Searle & Co., St. Louis, MO 63198, USA.
J Immunol. 1997 Oct 15;159(8):4024-34.
A soluble form of the human IL-5R alpha-chain (IL-5Ra) that contains the extracellular IL-5 binding domain has been evaluated for its effect on IL-5 binding to and activation of human eosinophils and basophils. The truncated receptor was expressed in Escherichia coli and recovered in biologically active form following renaturation and anion exchange chromatography. The soluble receptor formed a 1/1 complex with IL-5 in solution and bound IL-5 with affinity comparable to that of cell-associated IL-5Ra. Soluble IL-5Ra also competed with IL-5 for binding to the native alpha beta IL-5R on human cells and inhibited IL-5-mediated receptor activation and inflammatory mediator production. In this regard, the soluble receptor prevented IL-5-induced tyrosine phosphorylation of JAK2 kinase and IL-5R beta-chain and inhibited IL-5 priming of leukotriene C4 release by human basophils. However, the E. coli-derived receptor failed to inhibit IL-5 in longer term assays, including eosinophil survival and TF-1 cell proliferation, possibly due to its propensity to aggregate in a time- and temperature-dependent manner. In contrast, we observed that a soluble IL-5Ra derived from baculovirus-infected cells was less prone to aggregate and effectively antagonized IL-5-induced cell proliferation and survival. These findings indicate that the extracellular portion of the human IL-5Ra chain can prevent association of IL-5 with cell surface receptors and can attenuate signal transduction, mediator release, and survival of inflammatory cells. As such, soluble IL-5R may be useful in treating diseases such as human asthma, in which pulmonary injury is associated with the activity of IL-5R-bearing cells.
一种包含细胞外白细胞介素-5（IL-5）结合结构域的可溶性人IL-5受体α链（IL-5Ra），已对其在IL-5与人嗜酸性粒细胞和嗜碱性粒细胞结合及激活方面的作用进行了评估。截短的受体在大肠杆菌中表达，并在复性和阴离子交换色谱后以生物活性形式回收。可溶性受体在溶液中与IL-5形成1/1复合物，其与IL-5的结合亲和力与细胞相关的IL-5Ra相当。可溶性IL-5Ra还与IL-5竞争结合人细胞上的天然αβIL-5受体，并抑制IL-5介导的受体激活和炎症介质产生。在这方面，可溶性受体可防止IL-5诱导的JAK2激酶和IL-5Rβ链的酪氨酸磷酸化，并抑制人嗜碱性粒细胞白三烯C4释放的IL-5启动作用。然而，在包括嗜酸性粒细胞存活和TF-1细胞增殖的长期试验中，大肠杆菌来源的受体未能抑制IL-5，这可能是由于其倾向于以时间和温度依赖性方式聚集。相比之下，我们观察到来自杆状病毒感染细胞的可溶性IL-5Ra不太容易聚集，并有效拮抗IL-5诱导细胞增殖和存活。这些发现表明，人IL-5Ra链的细胞外部分可防止IL-5与细胞表面受体结合，并可减弱信号转导、介质释放和炎症细胞存活。因此，可溶性IL-5R可能对治疗如人类哮喘等疾病有用，在这些疾病中，肺损伤与携带IL-5R的细胞活性相关。
