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Small mannose-binding lectin-associated protein plays a regulatory role in the lectin complement pathway
Daisuke Iwaki1, Kazuko Kanno, Minoru Takahashi
1Department of Immunology, Fukushima Medical University, 1-Hikariga-oka, Fukushima City 960-1295, Japan.
Journal of Immunology (Baltimore, Md. : 1950)
|December 5, 2006
Summary
Mannose-binding lectin-associated serine protease-2 (MASP-2) is crucial for complement pathway activation. Small MBL-associated protein (sMAP) regulates this process, highlighting its role in innate immunity.
Area of Science:
- Immunology
- Complement System Biology
Background:
- Mannose-binding lectin (MBL) and ficolins are key pattern recognition molecules in innate immunity.
- They initiate the lectin complement pathway via MBL-associated serine proteases (MASPs).
- MASP-2 cleaves C4 and C2, while a truncated form, sMAP, is also present in complexes.
Purpose of the Study:
- To elucidate the function of small MBL-associated protein (sMAP) in the lectin complement pathway.
- To investigate the regulatory role of sMAP in MASP-2-mediated complement activation.
Main Methods:
- Generation of sMAP-deficient (sMAP(-/-)) mice through targeted gene disruption.
- Analysis of MASP-2 expression levels in sMAP(-/-) mice.
- Reconstitution experiments using recombinant sMAP (rsMAP) and recombinant MASP-2 (rMASP-2) in deficient serum.
Main Results:
- sMAP deficiency led to decreased MASP-2 expression.
- Recombinant sMAP and MASP-2 binding to MBL was competitive.
- Recombinant MASP-2 restored C4 cleavage activity, while rsMAP attenuated it.
Conclusions:
- MASP-2 is essential for C4 cleavage and lectin pathway activation.
- sMAP acts as a negative regulator in the lectin complement pathway activation.
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