Carbohydrate-binding specificities of mouse ficolin A, a splicing variant of ficolin A and ficolin B and their complex formation with MASP-2 and sMAP
Carbohydrate-binding specificities of mouse ficolin A, a splicing variant of ficolin A and ficolin B and their complex formation with MASP-2 and sMAP
复制标题
DOI：
10.1007/s00251-005-0058-1
复制
发表时间：
2005-12-01
期刊：
影响因子：
3.2
通讯作者：
Matsushita, M
中科院分区：
文献类型：
--
作者：
Endo, Y;Nakazawa, N;Matsushita, M
纤维蛋白是一组主要由胶原样结构域和纤维蛋白原样结构域组成的蛋白质，被认为通过其碳水化合物结合活性在先天免疫中发挥作用。在小鼠中已鉴定出两种类型的ficolin， ficolin A和ficolin b。然而，它们的结构和功能尚不完全清楚。在这项研究中，我们分离了一种新的具有较短的胶原样结构域和较长的间隙序列的ficolin a基因的cDNA，该基因是由ficolin a基因通过选择性剪接产生的。通过制备相应的重组体，我们描绘了小鼠ficolins的结构和功能，包括这种剪接变体。重组ficolin A及其剪接变体和ficolin B显示多聚体结构，并显示与n -乙酰氨基葡萄糖和n -乙酰半乳糖胺结合。有趣的是，ficolin B特异性识别唾液酸残基。Ficolin A及其变体与甘露糖结合凝集素（MBL）相关丝氨酸蛋白酶-2 （Masp-2）和MBL相关小蛋白（smap）结合，产生的复合物显示出强大的补体激活能力，而不是Ficolin B。此外，smap在与ficolin A及其变体相关的情况下与Masp-2竞争，抑制了ficolin A（或ficolin A变体）/ Masp-2复合物的补体激活，表明其在凝集素途径中具有调节作用。这些结果表明，ficolin A及其变体是凝集素途径的识别分子，而ficolin B通过其独特的碳水化合物结合特异性发挥着独特的作用。
Ficolins are a group of proteins mainly consisting of collagen-like and fibrinogen-like domains and are thought to play a role in innate immunity via their carbohydrate-binding activities. Two types of ficolins have been identified in mice, ficolin A, and ficolin B. However, their structure and function are not fully understood. In this study, we isolated the cDNA encoding a novel variant of ficolin A having a shorter collagen-like domain and a longer gap sequence, which was generated from the ficolin A gene by alternative splicing. We delineated the structure and function of mouse ficolins, including this splicing variant, by preparing the respective recombinants. Recombinant ficolin A, its splicing variant, and ficolin B showed multimeric structures and revealed binding to both N-acetylglucosamine and N-acetylgalactosamine. Interestingly, ficolin B specifically recognized sialic acid residues. Ficolin A and its variant, but not ficolin B, bound to mannose-binding lectin (MBL)-associated serine protease-2 (Masp-2) and small MBL-associated protein (smap), and the resulting complexes showed a potent complement activating capacity. In addition, smap competed with Masp-2 in association with ficolin A and its variant, and inhibited the complement activation by the ficolin A (or ficolin A variant)/MASP-2 complex, indicating its regulatory role in the lectin pathway. These results suggest that ficolin A and its variant function as recognition molecules of the lectin pathway, and ficolin B plays a distinct role through its unique carbohydrate-binding specificity.