Chiba H, Sano H, Iwaki D, Murakami S, Mitsuzawa H, Takahashi T, Konishi M, Takahashi H, Kuroki Y
Department of Biochemistry, Sapporo Medical University School of Medicine, Chuo-ku, Sapporo 060-8556, Japan.
Infect Immun. 2001 Mar;69(3):1587-92. doi: 10.1128/IAI.69.3.1587-1592.2001.
Lipopolysaccharide (LPS) has been known to induce inflammation by interacting with CD14, which serves as a receptor for LPS. Mannose-binding protein (MBP) belongs to the collectin subgroup of the C-type lectin superfamily, along with surfactant proteins SP-A and SP-D. We have recently demonstrated that SP-A modulates LPS-induced cellular responses by interaction with CD14 (H. Sano, H. Sohma, T. Muta, S. Nomura, D. R. Voelker, and Y. Kuroki, J. Immunol. 163:387-395, 2000) and that SP-D also interacts with CD14 (H. Sano, H. Chiba, D. Iwaki, H. Sohma, D. R. Voelker, and Y. Kuroki, J. Biol. Chem. 275:22442-22451, 2000). In this study, we examined whether MBP, a collectin highly homologous to SP-A and SP-D, could bind CD14. Recombinant rat MBP-A bound recombinant human soluble CD14 in a concentration-dependent manner. Its binding was not inhibited in the presence of excess mannose or EDTA. MBP-A bound deglycosylated CD14 treated with N-glycosidase F, neuraminidase, and O-glycosidase, indicating that MBP-A interacts with the peptide portion of CD14. Since LPS was also a ligand for the collectins, we compared the characteristics of binding of MBP-A to LPS with those of binding to CD14. MBP-A bound to lipid A from Salmonella enterica serovar Minnesota and rough LPS (S. enterica serovar Minnesota Re595 and Escherichia coli J5, Rc), but not to smooth LPS (E. coli O26:B6 and O111:B4). Unlike CD14 binding, EDTA and excess mannose attenuated the binding of MBP-A to rough LPS. From these results, we conclude that CD14 is a novel ligand for MBP-A and that MBP-A utilizes a different mechanism for CD14 recognition from that for LPS.
脂多糖（LPS）已知通过与作为LPS受体的CD14相互作用来诱导炎症。甘露糖结合蛋白（MBP）与表面活性蛋白SP - A和SP - D一样，属于C型凝集素超家族的collectin亚组。我们最近证明，SP - A通过与CD14相互作用调节LPS诱导的细胞反应（H. Sano、H. Sohma、T. Muta、S. Nomura、D. R. Voelker和Y. Kuroki，《免疫学杂志》163:387 - 395，2000年），并且SP - D也与CD14相互作用（H. Sano、H. Chiba、D. Iwaki、H. Sohma、D. R. Voelker和Y. Kuroki，《生物化学杂志》275:22442 - 22451，2000年）。在本研究中，我们检测了与SP - A和SP - D高度同源的collectin——MBP是否能结合CD14。重组大鼠MBP - A以浓度依赖的方式结合重组人可溶性CD14。在存在过量甘露糖或EDTA的情况下，其结合未受抑制。MBP - A结合经N - 糖苷酶F、神经氨酸酶和O - 糖苷酶处理的去糖基化CD14，表明MBP - A与CD14的肽段相互作用。由于LPS也是collectin的配体，我们比较了MBP - A与LPS结合的特性和与CD14结合的特性。MBP - A与肠炎沙门氏菌明尼苏达血清型的脂质A和粗糙LPS（肠炎沙门氏菌明尼苏达血清型Re595和大肠杆菌J5，Rc）结合，但不与光滑LPS（大肠杆菌O26:B6和O111:B4）结合。与CD14结合不同，EDTA和过量甘露糖减弱了MBP - A与粗糙LPS的结合。从这些结果，我们得出结论，CD14是MBP - A的一种新型配体，并且MBP - A对CD14的识别机制与对LPS的识别机制不同。
