Murata Y, Takaki S, Migita M, Kikuchi Y, Tominaga A, Takatsu K
Department of Biology, Kumamoto University Medical School, Japan.
J Exp Med. 1992 Feb 1;175(2):341-51. doi: 10.1084/jem.175.2.341.
Human interleukin 5 (IL-5) plays an important role in proliferation and differentiation of human eosinophils. We report the isolation of cDNA clones from cDNA libraries of human eosinophils by using murine IL-5 receptor alpha chain cDNA as a probe. Analysis of the predicted amino acid sequence indicated that the human IL-5 receptor has approximately 70% amino acid sequence homology with the murine IL-5 receptor and retains features common to the cytokine receptor superfamily. One cDNA clone encodes a glycoprotein of 420 amino acids (Mr 47,670) with an NH2-terminal hydrophobic region (20 amino acids), a glycosylated extracellular domain (324 amino acids), a transmembrane domain (21 amino acids), and a cytoplasmic domain (55 amino acids). Another cDNA encodes only the extracellular domain of this receptor molecule. Other cDNA clones encode molecules having diversified cytoplasmic domains. COS7 cells transfected with the cDNA expressed a approximately 60-kD protein and bound IL-5 with a single class of affinity (Kd = 250-590 pM). The Kd values were similar to that observed in normal human eosinophils. In contrast to the murine 60-kD alpha chain, which binds IL-5 with low affinity (Kd = approximately 10 nM), the human alpha chain homologue can bind IL-5 with much higher affinity by itself. RNA blot analysis of human cells demonstrated two transcripts (approximately 5.3 and 1.4 kb). Both of them were expressed in normal human eosinophils and in erythroleukemic cell line TF-1, which responds to IL-5. The human IL-5 receptor characterized in this paper is essential for signal transduction, because expression of this molecule in murine IL-3-dependent cell line FDC-P1 allowed these cells to proliferate in response to IL-5.
人白细胞介素5（IL-5）在人嗜酸性粒细胞的增殖和分化中起重要作用。我们报道了以鼠IL-5受体α链cDNA为探针，从人嗜酸性粒细胞cDNA文库中分离出cDNA克隆。对预测的氨基酸序列分析表明，人IL-5受体与鼠IL-5受体具有约70%的氨基酸序列同源性，并保留了细胞因子受体超家族的共同特征。一个cDNA克隆编码一个420个氨基酸（Mr 47,670）的糖蛋白，其具有一个NH2末端疏水区域（20个氨基酸）、一个糖基化的细胞外区域（324个氨基酸）、一个跨膜区域（21个氨基酸）和一个细胞质区域（55个氨基酸）。另一个cDNA仅编码该受体分子的细胞外区域。其他cDNA克隆编码具有多样化细胞质区域的分子。用该cDNA转染的COS7细胞表达了一种约60-kD的蛋白质，并以单一亲和力类别结合IL-5（Kd = 250 - 590 pM）。这些Kd值与正常人嗜酸性粒细胞中观察到的值相似。与以低亲和力（Kd = 约10 nM）结合IL-5的鼠60-kDα链不同，人α链同源物自身能以更高的亲和力结合IL-5。对人细胞的RNA印迹分析显示有两种转录本（约5.3和1.4 kb）。它们在正常人嗜酸性粒细胞和对IL-5有反应的红白血病细胞系TF-1中均有表达。本文所表征的人IL-5受体对于信号转导至关重要，因为该分子在鼠IL-3依赖性细胞系FDC-P1中的表达使这些细胞能够对IL-5作出增殖反应。
