Alveolar type II cells express a high-affinity receptor for pulmonary surfactant protein A.
Alveolar type II cells express a high-affinity receptor for pulmonary surfactant protein A.
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II 型肺泡细胞表达肺表面活性蛋白 A 的高亲和力受体。
DOI：
10.1073/pnas.85.15.5566
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发表时间：
1988
影响因子：
11.1
通讯作者：
Voelker,DR
中科院分区：
文献类型：
--
作者：
Kuroki,Y;Mason,RJ;Voelker,DR
原代培养的大鼠肺泡II型细胞与放射性标记的肺表面活性物质蛋白A(SP-A)具有高亲和力。~(125)I标记的SP-A的结合是时间和温度依赖的，并且不伴随显著的降解。在低浓度的SP-A(5微克/毫升)下，结合过程是饱和的，未标记的SP-A很容易与标记的SP-A竞争细胞结合部位。结合后，可以根据在0℃下对胰酶的敏感性来鉴定两个与细胞相关的125I标记的SP-A池。很可能胰酶敏感的池包括与细胞表面结合的125I标记的SP-A，而不敏感的池包括内化的蛋白质。对SP-A在0.1-10微克/毫升的细胞表面结合力的Scatchard分析表明，在0.1-1微克/毫升的浓度范围内有正的协同作用，Hill图显示NH=1.34+/-0.08，表观解离常数K‘d=1.02+/-0.32微克/毫升(假设低聚SP-A的天然分子质量为1.6 mda，则为0.64+/-0.19 nM)。SP-A与II型细胞的结合显示出对钙的绝对需求。推测的SP-A受体不受多种蛋白酶和N-葡聚糖酶处理的II型细胞的影响(EC 3.5.1.52)。肺泡巨噬细胞也表现出与SP-A的高亲和力结合，而大鼠肺成纤维细胞和肺泡上皮细胞株L2仅表现出非特异性结合。
Primary cultures of rat alveolar type II cells bind radiolabeled pulmonary surfactant protein A (SP-A) with high affinity. The binding of 125I-labeled SP-A is time- and temperature-dependent and is not accompanied by significant degradation. The binding process is saturable at low concentrations of SP-A (5 micrograms/ml), and unlabeled SP-A readily competes with labeled SP-A for cellular binding sites. Subsequent to binding, two pools of cell-associated 125I-labeled SP-A can be identified based upon sensitivity to trypsin at 0 degrees C. It is likely that the trypsin-sensitive pool comprises 125I-labeled SP-A bound to the cell surface and the trypsin-insensitive pool comprises the internalized protein. Scatchard analysis of cell surface binding of SP-A at 0.1-10 micrograms/ml shows positive cooperativity at concentrations between 0.1 and 1 micrograms/ml. Hill plots give nH = 1.34 +/- 0.08 with an apparent dissociation constant K'd = 1.02 +/- 0.32 micrograms/ml (which is 0.64 +/- 0.19 nM if the native molecular mass of oligomeric SP-A is assumed to be 1.6 MDa). The binding of SP-A to type II cells shows an absolute requirement for Ca2+. The putative receptor for SP-A is unaffected by treatment of type II cells with a variety of proteases and N-Glycanase (EC 3.5.1.52). Alveolar macrophages also exhibit high-affinity binding of SP-A, but rat lung fibroblasts and the alveolar epithelial cell line L2 exhibit only nonspecific binding.