Sano H, Chiba H, Iwaki D, Sohma H, Voelker D R, Kuroki Y
Department of Biochemistry, Sapporo Medical University School of Medicine, Sapporo, Japan.
J Biol Chem. 2000 Jul 21;275(29):22442-51. doi: 10.1074/jbc.M001107200.
Surfactant proteins A (SP-A) and D (SP-D) are lung collectins that are constituents of the innate immune system of the lung. Recent evidence (Sano, H., Sohma, H., Muta, T., Nomura, S., Voelker, D. R., and Kuroki, Y. (1999) J. Immunol. 163, 387-395) demonstrates that SP-A modulates lipopolysaccharide (LPS)-induced cellular responses by direct interaction with CD14. In this report we examined the structural elements of the lung collectins involved in CD14 recognition and the consequences for CD14/LPS interaction. Rat SP-A and SP-D bound CD14 in a concentration-dependent manner. Mannose and EDTA inhibited SP-D binding to CD14 but did not decrease SP-A binding. The SP-A binding to CD14 was completely blocked by a monoclonal antibody that binds to the SP-A neck domain but only partially blocked by an antibody that binds to the SP-A lectin domain. SP-A but not SP-D bound to deglycosylated CD14. SP-D decreased CD14 binding to both smooth and rough LPS, whereas SP-A enhanced CD14 binding to rough LPS and inhibited binding to smooth LPS. SP-A also altered the migration profile of LPS on a sucrose density gradient in the presence of CD14. From these results, we conclude that 1) lung collectins bind CD14, 2) the SP-A neck domain and SP-D lectin domain participate in CD14 binding, 3) SP-A recognizes a peptide component and SP-D recognizes a carbohydrate moiety of CD14, and 4) lung collectins alter LPS/CD14 interactions.
表面活性蛋白A（SP-A）和表面活性蛋白D（SP-D）是肺凝集素，是肺固有免疫系统的组成部分。最近的证据（佐野浩、宗间浩、武田哲、野村幸、沃尔克·D·R和黑木洋（1999年）《免疫学杂志》163卷，387 - 395页）表明，SP-A通过与CD14直接相互作用来调节脂多糖（LPS）诱导的细胞反应。在本报告中，我们研究了参与CD14识别的肺凝集素的结构元件以及对CD14/LPS相互作用的影响。大鼠SP-A和SP-D以浓度依赖的方式结合CD14。甘露糖和乙二胺四乙酸（EDTA）抑制SP-D与CD14的结合，但不降低SP-A的结合。与SP-A颈部结构域结合的单克隆抗体完全阻断了SP-A与CD14的结合，但与SP-A凝集素结构域结合的抗体仅部分阻断了这种结合。SP-A而非SP-D与去糖基化的CD14结合。SP-D降低了CD14与光滑型和粗糙型LPS的结合，而SP-A增强了CD14与粗糙型LPS的结合并抑制了与光滑型LPS的结合。在存在CD14的情况下，SP-A还改变了LPS在蔗糖密度梯度上的迁移图谱。从这些结果中，我们得出以下结论：1）肺凝集素结合CD14；2）SP-A颈部结构域和SP-D凝集素结构域参与CD14的结合；3）SP-A识别CD14的肽成分，SP-D识别CD14的碳水化合物部分；4）肺凝集素改变LPS/CD14相互作用。
