Interaction of SP-A (surfactant protein A) with bacterial rough lipopolysaccharide (Re-LPS), and effects of SP-A on the binding of Re-LPS to CD14 and LPS-binding protein
Interaction of SP-A (surfactant protein A) with bacterial rough lipopolysaccharide (Re-LPS), and effects of SP-A on the binding of Re-LPS to CD14 and LPS-binding protein
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DOI：
10.1042/bj20050529
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发表时间：
2005-10-01
影响因子：
4.1
通讯作者：
Casals, S
中科院分区：
文献类型：
--
作者：
García-Verdugo, I;Sánchez-Barbero, F;Casals, S
SP-A（表面活性蛋白A）是一种主要参与先天性肺免疫的脂质结合凝集素。SP-A与细菌粗糙LPS（脂多糖）Re-LPS（来自沙门氏菌的LPS的Re 595突变体）相互作用，但不与光滑LPS相互作用。在本研究中，我们首先研究了人SP-A与Re-LPS相互作用的特征。在存在和不存在SP-A的情况下，FITC标记的Re-LPS的荧光强度和各向异性测量表明，SP-A以不依赖于Ca 2+的方式与溶液中的Re-LPS结合，解离常数为2.8 × 10（-8）M。在钙离子存在下，SP-A和[H-3]Rb-LPS（来自大肠杆菌菌株LCD 25的LPS的Rb突变体）胶束形成高迁移率复合物，如通过蔗糖密度梯度检测的。通过光散射进一步表征由SP-A诱导的Re-LPS聚集。另一方面，人SP-A抑制用Re-LPS或光滑LPS刺激的人巨噬细胞样U937细胞的TNF-α（肿瘤坏死因子-α）分泌。我们进一步研究了人SP-A对Re-LPS与LBP（LPS结合蛋白）和CD 14结合的影响。SP-A降低了Re-LPS与CD 14的结合，但不降低与LBP的结合，如通过I-125-ASD-Re-LPS [I-125-标记的磺基琥珀酰亚胺基-2-（p-叠氮基水杨酰胺基）-1，3-（Re-LPS的二硫代丙酸酯衍生物]的交联实验和FITC-Re-LPS的荧光分析所检测到的。当SP-A、LBP和CD 14一起孵育时，SP-A降低LBP将I-125-ASD-Re-LPS转移至CD 14的能力。这些SP-A效应不是由于SP-A在钙存在下聚集Re-LPS的能力，因为它们在不存在和存在钙的情况下都被观察到。这些研究表明，SP-A可以通过改变LBP-CD 14受体复合物的能力来调节Re-LPS应答。
SP-A (surfactant protein A) is a lipid-binding collectin primarily involved in innate lung immunity. SP-A interacts with the bacterial rough LPS (lipopolysaccharide) Re-LPS (Re595 mutant of LPS from Salmonella minnesota), but not with smooth LPS. In the present study, we first examined the characteristics of the interaction of human SP-A with Re-LPS. Fluorescence intensity and anisotropy measurements of FITC-labelled Re-LPS in the presence and absence of SP-A indicated that SP-A bound to Re-LPS in solution in a Ca2+-independent manner, with a dissociation constant of 2.8 x 10(-8) M. In the presence of calcium, a high-mobility complex of SP-A and [H-3]Rb-LPS (Rb mutant of LPS from Escherichia coli strain LCD 25) micelles was formed, as detected by sucrose density gradients. Re-LPS aggregation induced by SP-A was further characterized by light scattering. On the other hand, human SP-A inhibited TNF-alpha (tumour necrosis factor-a) secretion by human macrophage-like U937 cells stimulated with either Re-LPS or smooth LPS. We further examined the effects of human SP-A on the binding of Re-LPS to LBP (LPS-binding protein) and CD14. SP-A decreased the binding of Re-LPS to CD14, but not to LBP, as detected by cross-linking experiments with I-125-ASD-Re-LPS [I-125-labelled sulphosuccinimidyl-2-(p-azidosalicylamido)-1,3-(dithiopropionate derivative of Re-LPS] and fluorescence analysis with FITC-Re-LPS. When SP-A, LBP and CD 14 were incubated together, SP-A reduced the ability of LBP to transfer I-125-ASD-Re-LPS to CD14. These SP-A effects were not due to the ability of SP-A to aggregate Re-LPS in the presence of calcium, since they were observed in both the absence and the presence of calcium. These studies suggest that SP-A could contribute to modulate Re-LPS responses by altering the competence of the LBP-CD14 receptor complex.