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MASP-3 and its association with distinct complexes of the mannan-binding lectin complement activation pathway

M R Dahl1, S Thiel, M Matsushita

  • 1Department of Medical Microbiology and Immunology, University of Aarhus, DK 8000, Aarhus, Denmark.

Immunity
|August 4, 2001
PubMed

Insights

Mannan-binding lectin-associated serine protease 3 (MASP-3) is a newly identified component of the innate immune system. This protease regulates complement activation by interacting with other MBL-associated serine proteases (MASPs) within MBL complexes.

Area of Science:

  • Immunology
  • Complement system
  • Innate immunity

Background:

  • The mannan-binding lectin (MBL) pathway is crucial for innate immune defense.
  • MBL activation initiates the complement cascade via MBL-associated serine proteases (MASPs).
  • MASPs recruit complement factors C4 and C2 to form the C3 convertase or activate C3 directly.

Purpose of the Study:

  • To identify and characterize a novel member of the MBL complex, MASP-3.
  • To investigate the role of MASP-3 in complement activation pathways.
  • To understand the differential composition and function of MBL oligomers.

Main Methods:

  • Phylogenetic analysis to identify conserved MBL complex members.
  • Gene expression analysis through alternative splicing of the MASP-1/3 gene.
  • Biochemical assays to determine protease activity and MBL oligomer composition.

Main Results:

  • MASP-3, a phylogenetically conserved protease, is generated via alternative splicing of the MASP-1/3 gene.
  • Distinct MBL oligomers exhibit specific MASP compositions and biological activities.
  • MASP-3, found on larger MBL oligomers with MASP-2, downregulates the C4 and C2 cleaving activity of MASP-2.

Conclusions:

  • MASP-3 is a significant regulator within the MBL complement pathway.
  • The composition of MBL oligomers dictates their specific immune functions.
  • MASP-3 plays a key role in modulating complement activation, particularly C4 and C2 cleavage.

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