Lung surfactant apoprotein SP-A (26-36 kDa) binds with high affinity to isolated alveolar type II cells.
Lung surfactant apoprotein SP-A (26-36 kDa) binds with high affinity to isolated alveolar type II cells.
复制标题
肺表面活性剂脱辅基蛋白 SP-A (26-36 kDa) 以高亲和力与分离的 II 型肺泡细胞结合。
DOI：
10.1073/pnas.86.14.5410
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发表时间：
1989
影响因子：
11.1
通讯作者：
Hawgood,S
中科院分区：
文献类型：
--
作者：
Wright,JR;Borchelt,JD;Hawgood,S
肺表面活性物质是由肺泡II型细胞合成和分泌的。这些细胞通过内化过程循环表面活性物质脂类，这种内化过程在体外被分子质量为26-36 kDa的表面活性蛋白(SP-A)所增强。SP-A还抑制II型细胞的脂质分泌。这些结果表明，SP-A可能在表面活性物质池大小的反馈调节中起作用，并与II型细胞表面有SP-A受体的假设一致。本研究的目的是研究放射性碘标记的SP-A与分离的大鼠II型细胞的结合情况。在4℃时，SP-A与II型细胞的结合具有大约5×10(-10)M的K1/2，是饱和的，并被过量的未标记SP-A抑制。结合依赖于钙，并通过SP-A的热处理而减少。胶原酶处理产生的SP-A的蛋白水解性片段的结合被过量的未标记的SP-A减少。过量的未标记SP-A不会抑制该片段与巨噬细胞和肺成纤维细胞的结合。II型细胞表面的胰酶作用减少了完整的SP-A和胶原酶抗性片段的结合。这些结果表明，SP-A以高亲和力与II型细胞结合，提示这些细胞具有识别SP-A的羧基末端结构域的受体。
Pulmonary surfactant is synthesized and secreted by alveolar type II cells. These cells recycle surfactant lipids by an internalization process that is enhanced in vitro by the surfactant proteins with molecular masses of 26-36 kDa (SP-A). SP-A also inhibits the secretion of lipid by type II cells. These results suggest that SP-A may play a role in feedback regulation of surfactant pool size and are consistent with the hypothesis that the type II cell surface has receptors for SP-A. The goal of this study is to characterize the binding of radioiodinated SP-A to isolated rat type II cells. Binding of SP-A to type II cells at 4 degrees C has a K1/2 of approximately 5 X 10(-10) M, is saturable, and is inhibited by excess unlabeled SP-A. Binding is dependent on calcium and is reduced by heat treatment of SP-A. The binding of a proteolytic fragment of SP-A that is produced by collagenase treatment is reduced by excess unlabeled SP-A. The binding of the fragment to macrophages and lung fibroblasts is not inhibited by excess unlabeled SP-A. Trypsinization of the type II cell surface reduces the binding of both intact SP-A and the collagenase-resistant fragment. These results show that SP-A binds to type II cells with high affinity and suggest that these cells have receptors that recognize the carboxyl-terminal domain of SP-A.