Related Experiment Video

Updated: May 14, 2026

Myeloid Innate Signaling Pathway Regulation by MALT1 Paracaspase Activity
07:09

Myeloid Innate Signaling Pathway Regulation by MALT1 Paracaspase Activity

Published on: January 7, 2019

The role of MASP-1/3 in complement activation

Hideharu Sekine1, Minoru Takahashi, Daisuke Iwaki

  • 1Department of Immunology, Fukushima Medical University School of Medicine, 1-Hikariga-oka, Fukushima 960-1295, Japan.

Advances in Experimental Medicine and Biology
|February 14, 2013
PubMed

Insights

Mannose-binding lectin-associated serine proteases (MASPs) MASP-1 and MASP-3 are crucial for activating the complement system's alternative pathway. These proteases also appear to play a role in the lectin pathway's activation.

Area of Science:

  • Immunology
  • Complement System Biology

Background:

  • The complement system comprises over 30 proteins, activating via classical, lectin, or alternative pathways for pathogen destruction.
  • Mannose-binding lectin (MBL) and ficolins initiate the lectin pathway, activating MBL-associated serine proteases (MASPs).
  • MASP-2 is essential for C3 convertase assembly, but the roles of MASP-1 and MASP-3 are largely unknown.

Purpose of the Study:

  • To elucidate the physiological functions of MASP-1 and MASP-3 within the complement system.
  • To investigate the involvement of MASP-1 and MASP-3 in the lectin and alternative pathways.

Main Methods:

  • Generation of a MASP-1 and MASP-3 deficient (M1/3 KO) mouse model.
  • In vitro enzymatic assays to assess the activity of MASP-1 and MASP-3 on Factor D and other MASPs.

Main Results:

  • M1/3 KO mice exhibited a complete lack of alternative pathway activation due to inactive Factor D.
  • MASP-1 and MASP-3 demonstrated the ability to activate Factor D proenzyme in vitro.
  • MASP-1 was shown to activate MASP-2 and MASP-3, analogous to C1r's activation of C1s.

Conclusions:

  • MASP-1 and MASP-3 are essential for the activation of the alternative complement pathway.
  • These proteases are implicated in the activation mechanisms of both the lectin and alternative pathways.

More Related Videos

High-resolution Melting PCR for Complement Receptor 1 Length Polymorphism Genotyping: An Innovative Tool for Alzheimer's Disease Gene Susceptibility Assessment07:26

High-resolution Melting PCR for Complement Receptor 1 Length Polymorphism Genotyping: An Innovative Tool for Alzheimer's Disease Gene Susceptibility Assessment

Published on: July 18, 2017

Reconstitution of Msp1 Extraction Activity with Fully Purified Components05:52

Reconstitution of Msp1 Extraction Activity with Fully Purified Components

Published on: August 10, 2021

Related Concept Videos

Complement System01:27

Complement System

The complement system is a group of approximately 20 plasma proteins that strengthen the body's defenses against infections through opsonization, inflammation, and cell lysis. Opsonization involves coating pathogens with complement proteins, making them more recognizable and facilitating phagocyte engulfment. Certain complement proteins induce inflammation that attracts immune cells to the site of infection. Cell lysis involves the destruction of pathogens through the formation of a membrane...
Role of Matrix Metalloproteases in Degradation of ECM01:23

Role of Matrix Metalloproteases in Degradation of ECM

Matrix metalloproteases (MMPs) are enzymes involved in the hydrolysis of proteins and glycoproteins of the extracellular matrix. MMPs are essential for the migration and proliferation of cells through the dense matrix network, throughout embryonic development, and throughout morphogenesis. The first MMP activity discovered was a collagenase in a tadpole's tail undergoing metamorphosis. The active collagen deposition and modifications lead to the morphogenesis of tadpoles into the adult body.
A...
Caspases01:24

Caspases

Caspase, a family of cysteine proteases, serve as effectors in apoptosis. The ced3 gene in C.elegans was first identified to be involved in apoptosis. This gene encodes the ced-3 caspase that is similar to the interleukin-1-beta converting enzyme or ICE in mammals. In addition to apoptosis, caspases also function in the inflammatory response. Inflammatory caspases are essential in activating pro-inflammatory cytokines that recruit immune cells and block the replication of pathogens inside cells.
Antigen Processing Pathways01:31

Antigen Processing Pathways

MHC molecules are key players in the immune response, enabling T cells to recognize and respond to specific antigens. They are present on the surface of all nucleated cells in the body and are instrumental in presenting antigens to T cells and activating them. T cells recognize the MHC-antigen complex and initiate an immune response. MHC class I and MHC class II are two main types of MHC molecules, each associated with a distinct antigen processing pathway.
MHC Class I: Presenting Endogenous...
Antimicrobial Proteins01:23

Antimicrobial Proteins

Antimicrobial proteins are important components of the immune system. They aid the body in combating pathogens by either killing them directly or hindering their replication processes. Four main types of antimicrobial substances are interferons, the complement system, iron-binding proteins, and antimicrobial proteins.
Interferons
Interferons (IFNs) are proteins produced by lymphocytes, macrophages, and fibroblasts infected with viruses. While IFNs cannot prevent viruses from entering and...
MAPK Signaling Cascades01:07

MAPK Signaling Cascades

Mitogen-activated protein kinase, or MAPK pathway, activates three sequential kinases to regulate cellular responses such as proliferation, differentiation, survival, and apoptosis. The canonical MAPK pathway starts with a mitogen or growth factor binding to an RTK. The activated RTKs stimulate Ras, which recruits Raf or MAP3 Kinase (MAPKKK), the first kinase of the MAPK signaling cascade. Raf further phosphorylates and activates MEK or MAP2 Kinases (MAPKK), which in turn phosphorylates MAP...