Lectin Pathway of Bony Fish Complement: Identification of Two Homologs of the Mannose-Binding Lectin Associated with MASP2 in the Common Carp (Cyprinus carpio)

Abstract

The lectin pathway of complement is considered to be the most ancient complement pathway as inferred from identification of ancient homologs of mannose-binding lectin (MBL) and MBL-associated serine proteases (MASPs) in some invertebrates. MBL homologs with galactose selectivity and an MASP3-like sequence also occur in bony fish, linking the evolution of the lectin complement pathway from invertebrates to higher vertebrates. However, these cannot be considered authentic complement components until confirmatory functional evidence is obtained. Here, we report the isolation and characterization of two MBL homologs from a cyprinid teleost, the common carp, Cyprinus carpio. One, designated GalBL, corresponds to the MBL-like molecule with the galactose specificity. The other is an authentic MBL with mannose specificity. Both were found to associate with a serine protease that cleaves native human C4 into C4b but not C4i with a hydrolyzed thioester. Molecular cloning and phylogenetic analysis revealed this C4-activating protease to be carp MASP2, indicating that MASP2 arose before the emergence of bony fish. Database mining of MBL-like genes reveals that MBL and GalBL genes are arranged in tandem in the zebrafish genome and that both lectins are conserved in the distantly related puffer fish. These results imply that bony fish have developed a diverged set of MBL homologs that function in the lectin complement pathway.

Mannan-Binding Lectin-Associated Serine Protease (MASP)-1 Is Crucial for Lectin Pathway Activation in Human Serum, whereas neither MASP-1 nor MASP-3 Is Required for Alternative Pathway Function

“…The crucial role of MASP-1 was surprising considering that both birds and fish seem to have lost the MASP-1-encoding exons by secondary genetic events subsequent to expansion of the MASPs (47)(48)(49). Previous results indicating that MASP-2 does not need help for activation have been confounded by the presence of activated MASP-2 in the preparations, for example (4), a problem we identified and then solved through coexpression of MASP-2 with C1 inhibitor.…”

Evolution and Immune Function of Fish Lectins

“…25,75 MBLs were also purified from rohu (L. rohita), rainbow trout (O. mykiss), sea lamprey (Petromyzon marinus), common carp (Cyprinus carpio), fugu (T. rubripes), and turbot (Scophthalmus maximus). [76][77][78][79][80] Moreover, MBL gene from channel catfish (Ictalurus punctatus) was upregulated following the exposure to gram-negative pathogens. 80 In the African catfish, Clarias gariespinus, MBL exhibited antimicrobial activity and in tilapia (O. niloticus), it induced cytochine production.…”

“…The MBL-A/MBL-C duplication was probably an independent event in the mammalian lineage. 77 The three identified and partially characterized rainbow trout MBL homologues represent structural homologues of mammalian MBLs and are expressed in various tissues including the anterior intestine, the liver, and spleen. A rainbow trout MASP-3 homologue was also expressed in partially overlapping tissues.…”

Characterization and bacterial-binding activity of a novel C-type lectin from the red-spotted grouper, Epinephelus akaara

“…The MBL and ficolins have three similar domains: a cysteine-rich N-terminal region, a collagenous region characterized by Gly-X-Y repeats (X and Y stand for any amino acids) (Dodds and Matsushita, 2007), and a neck region. The major differences between them include fewer repeats of Gly-X-Y within ficolin and a fibrinogen-like domain within the C-terminal region of ficolin (Matsushita and Fujita, 2002;Atkinson et al, 2004;Nakao et al, 2006;Runza et al, 2008).…”

“…The lamprey is the most primitive animal found to possess the MBL Dodds and Matsushita, 2007). Two types of the MBL group have been characterized in the bony fish: one has a QPD-type galactose-binding CRD (with Gln-Pro-Asp motif) and is designated GalBL, and the other has an EPN-type mannose-binding CRD and is designated MBL (Vitved et al, 2000;Nakao et al, 2006;Jackson et al, 2007). Previous studies have shown that GalBL was probably mutated from an MBL extra copy and has since acquired galactose-binding capability (Nonaka and Smith, 2000).…”