Interaction properties of human mannan-binding lectin (MBL)-associated serine proteases-1 and -2, MBL-associated protein 19, and MBL

被引:109
作者
Thielens, NM
Cseh, S
Thiel, S
Vorup-Jensen, T
Rossi, V
Jensenius, JC
Arlaud, GJ
机构
[1] Commiss Energie Atom, Inst Biol Struct Jean Pierre Ebel, Lab Enzymol Mol, CNRS, F-38027 Grenoble 1, France
[2] Univ Aarhus, Dept Med Microbiol & Immunol, Aarhus, Denmark
关键词
D O I
10.4049/jimmunol.166.8.5068
中图分类号
R392 [医学免疫学]; Q939.91 [免疫学];
学科分类号
100102 ;
摘要
The mannan-binding lectin (MBL) activation pathway of complement plays an important role in the innate immune defense against pathogenic microorganisms. In human serum, two MBL-associated serine proteases (MASP-1, MASP-2) and MBL-associated protein 19 (MAp19) were found to be associated with MBL. With a view to investigate the interaction properties of these proteins, human MASP-1, MASP-2, MAp19, as well as the N-terminal complement subcomponents C1r/C1s, Uegf, and bone morphogenetic protein-1-epidermal growth factor (CUB-EGF) segments of MASP-1 and MASP-2, were expressed in insect or human kidney cells, and MBL was isolated from human serum. Sedimentation velocity analysis indicated that the MASP-1 and MASP-2 CUB-EGF segments and the homologous protein MAp19 all behaved as homodimers (2.8-3.2 S) in the presence of Ca2+. Although the latter two dimers were not dissociated by EDTA, their physical properties were affected. In contrast, the MASP-1 CUB-EGF homodimer was not sensitive to EDTA. The three proteins and full-length MASP-1 and MASP-2 showed no interaction with each other as judged by gel filtration and surface plasmon resonance spectroscopy. Using the latter technique, MASP-1, MASP-2, their CUB-EGF segments, and MAp19 were each shown to bind to immobilized MBL, with K-D values of 0.8 nM (MASP-2),1.4 nM (MASP-1), 13.0 nM (MAp19 and MASP-2 CUB-EGF), and 25.7 nM (MASP-1 CUB-EGF). The binding was Ca2+-dependent and fully sensitive to EDTA in all cases. These data indicate that MASP-1, MASP-2, and MAp19 each associate as homodimers, and individually form Ca2+-dependent complexes with MBL through the CUB-EGF pair of each protein. This suggests that distinct MBL/MASP complexes may be involved in the activation or regulation of the MBL pathway. The Journal of Immunology, 2001.
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页码:5068 / 5077
页数:10
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