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At least 19 recordsLinked to original sources
PubMed2005

Carbohydrate-binding specificities of mouse ficolin A, a splicing variant of ficolin A and ficolin B and their complex formation with MASP-2 and sMAP.

Ficolins are a group of proteins mainly consisting of collagen-like and fibrinogen-like domains and are thought to play a role in innate immunity via their carbohydrate-binding activities. Two types of ficolins have been identified in mice, ficolin A, and ficolin B. However, their structure and function are not fully understood. In this study, we isolated the cDNA encoding a novel variant of ficolin A having a shorter collagen-like domain and a longer gap sequence, which was generated from the ficolin A gene by alternative splicing. We delineated the structure and function of mouse ficolins, including this splicing variant, by preparing the respective recombinants. Recombinant ficolin A, its splicing variant, and ficolin B showed multimeric structures and revealed binding to both N-acetylglucosamine and N-acetylgalactosamine. Interestingly, ficolin B specifically recognized sialic acid residues. Ficolin A and its variant, but not ficolin B, bound to mannose-binding lectin (MBL)-associated serine protease-2 (Masp-2) and small MBL-associated protein (smap), and the resulting complexes showed a potent complement activating capacity. In addition, smap competed with Masp-2 in association with ficolin A and its variant, and inhibited the complement activation by the ficolin A (or ficolin A variant)/MASP-2 complex, indicating its regulatory role in the lectin pathway. These results suggest that ficolin A and its variant function as recognition molecules of the lectin pathway, and ficolin B plays a distinct role through its unique carbohydrate-binding specificity.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Specific binding of L-ficolin and H-ficolin to apoptotic cells leads to complement activation.

The serum lectins mannose-binding lectin (MBL), L-ficolin, and H-ficolin are recognition molecules in the lectin complement pathway, which play an important role in innate immunity. To assess involvement of the lectin pathway in the clearance of apoptotic cells, we used flow cytometry to quantify binding of MBL, L-ficolin, and H-ficolin to apoptotic HL60, U937, and Jurkat cells induced by actinomycin D. When apoptotic cells were incubated with normal human serum, MBL and L-ficolin bound to all three cell lines tested; moreover, H-ficolin bound to apoptotic Jurkat cells only. Subsequently, C4 and C3 were deposited on apoptotic cells of all three cell lines. MBL, L-ficolin, and H-ficolin binding to apoptotic cells was confirmed by the use of purified proteins. Purified C4 added to apoptotic cells that had bound pure L-ficolin was deposited on the cell surfaces. In L-ficolin-depleted serum, C3 deposition on HL60 or Jurkat cells decreased to approximately 50% or 70%, respectively, in comparison to the serum before L-ficolin depletion. We conclude that L-ficolin, in addition to MBL, recognizes apoptotic cells and activates complement via the lectin pathway. We also observed in vitro binding of L-ficolin and H-ficolin to cC1q receptor (C1q receptor specific for the collagenous region of C1q)/calreticulin, a candidate receptor for the collagenous region of MBL and C1q. Thus, L-ficolin and H-ficolin as well as MBL participate in the clearance of apoptotic cells through complement activation.

Apoptosis↗
PubMed2004

Identification of the mouse H-ficolin gene as a pseudogene and orthology between mouse ficolins A/B and human L-/M-ficolins.

Ficolin is a collagenous lectin which plays a crucial role in innate immunity. Three and two ficolins have been identified in human and mice, respectively. To identify the mouse homologue of human H-ficolin and to elucidate the orthology between mouse ficolins A/B and human L-/M-ficolins, the gene structures were explored. The mouse homologue of the H-ficolin gene was identified as a pseudogene on chromosome 4. The mouse ficolin A gene was located far from the ficolin B gene on chromosome 2, whereas the human L-ficolin and M-ficolin genes were close in the region homologous to the ficolin B locus. Together with the exon-intron structures and the phylogenetic tree, these results suggest that ficolin B is the mouse orthologue of M-ficolin and that the genes encoding serum-type ficolins, ficolin A and L-ficolin, were generated independently from the ficolin B/M-ficolin lineage each in mice and primates.

Amino Acid Sequence↗
PubMed2005

Ficolin A and ficolin B are expressed in distinct ontogenic patterns and cell types in the mouse.

Ficolins are a group of proteins characterized by the presence of collagen-like and fibrinogen-like domains. Two of three human ficolins, L-ficolin and H-ficolin, are serum lectins that form complexes with mannose-binding lectin-associated serine proteases (MASPs) and play important roles in the lectin complement pathway. The other human ficolin, M-ficolin, is a non-serum-type ficolin that is expressed in monocytes. Little is known about the physiological roles of ficolins. In this study, we delineated the ontogeny and cell types that express ficolins in mice. RT-PCR analysis showed that the expression pattern of ficolin A expression was closely similar to that of Masps, suggesting that these molecules may function in coordination as components of the lectin complement pathway. The cell types that express ficolin A mRNA in both adult liver and spleen were identified as macrophages by in situ hybridization. Ficolin B exhibited a distinct ontogeny pattern that switched from embryonic liver to postnatal bone marrow and spleen. The cells that express ficolin B mRNA were identified as belonging to the myeloid cell lineage by magnetic sorting and by subsequent RT-PCR in bone marrow cells. Thus, the different spatial-temporal expression patterns of ficolins A and B suggest that these molecules play distinct roles in the prenatal and postnatal stages.

Animals↗
PubMed1996

Characterization of ficolins as novel elastin-binding proteins and molecular cloning of human ficolin-1.

A novel elastin-binding protein, EBP-37, was recently identified and purified from human plasma. Its partial amino acid sequences showed significant homology to porcine ficolins, which were originally purified from porcine uterus membranes as multimeric proteins with fibrinogen- and collagen-like domains. Here we report the presence of ficolins in an elastin-binding fraction of porcine plasma and the direct binding of recombinant porcine ficolin-alpha to elastin. In addition, a cDNA encoding a human counterpart of porcine ficolins that is composed of 319 amino acids and is different from EBP-37 was cloned and named human ficolin-1. Northern blotting of various human tissues revealed that human ficolin-1 mRNA is highly expressed in peripheral blood leukocytes. These data suggested that there are at least two kinds of ficolin-related proteins in both pig and human, and they may function as plasma proteins with elastin-binding activities.

Amino Acid Sequence↗
PubMed2005

Effect of capsulation of opportunistic pathogenic bacteria on binding of the pattern recognition molecules mannan-binding lectin, L-ficolin, and H-ficolin.

Mannan-binding lectin (MBL), L-ficolin, and H-ficolin are pattern recognition molecules of the innate immune system. We investigated their ability to bind to different serotypes and noncapsulated variants of two gram-positive bacterial species, Streptococcus pneumoniae and Staphylococcus aureus. MBL did not bind to capsulated S. aureus or capsulated S. pneumoniae but did bind to a noncapsulated S. aureus variant (Wood). L-ficolin bound to some capsulated S. aureus serotypes (serotypes 1, 8, 9, 11, and 12) and capsulated S. pneumoniae serotypes (11A, 11D, and 11F) but not to noncapsulated strains. H-ficolin did not bind to any of the S. pneumoniae and S. aureus serotypes included in this study but did bind to one strain of Aerococcus viridans. The concentrations of the three proteins in 97 plasma samples were estimated. The median concentrations were 0.8 mug per ml for MBL, 3.3 mug per ml for L-ficolin, and 18.4 mug per ml for H-ficolin.

Bacterial Capsules↗
PubMed2005

Human M-ficolin is a secretory protein that activates the lectin complement pathway.

Three types of ficolins have been identified in humans: L-ficolin, M-ficolin, and H-ficolin. Similar to mannose-binding lectin, L-ficolin and H-ficolin are the recognition molecules in the lectin complement pathway. Another human ficolin, M-ficolin, is a nonserum ficolin that is expressed in leukocytes and lung; however, little is known about its physiologic roles. In this study, we report the characterization of M-ficolin in terms of its protein localization and lectin activity. M-ficolin was localized in secretory granules in the cytoplasm of neutrophils, monocytes, and type II alveolar epithelial cells in lung. M-ficolin precipitated with mannose-binding lectin-associated serine proteases (MASP)-1 and MASP-2 in a co-immunoprecipitation assay, indicating that M-ficolin forms complexes with MASP-1 and MASP-2. M-ficolin-MASP complexes activated complement on N-acetylglucosamine (GlcNAc)-coated microplates in a C4 deposition assay. M-ficolin bound to several neoglycoproteins bearing GlcNAc, N-acetylgalactosamine, and sialyl-N-acetyllactosamine, suggesting that M-ficolin can recognize the common carbohydrate residues found in microbes. Indeed, M-ficolin bound to Staphylococcus aureus through GlcNAc. These results indicate that M-ficolin, like its family members, functions as a recognition molecule of the lectin complement pathway and plays an important role in innate immunity.

Complement Activation↗
PubMed2003

Expression and secretion of ficolin beta by porcine neutrophils.

Ficolins are collagenous lectins that bind N-acetylglucosamine (GlcNAc) as well as some bacterial surfaces, and may have opsonic and complement-activating functions. Ficolin alpha in porcine plasma binds Actinobacillus pleuropneumoniae serotype 5 (APP) in a GlcNAc-dependent manner. In the present study, we discovered that porcine neutrophils, but not platelets or mononuclear cells, contained a different ficolin that migrated as a 39-kDa band on SDS-PAGE and resembled a minor component of plasma ficolins that binds APP. However, neutrophil ficolins (pI range 6.4-7.4) were readily distinguished from plasma ficolin alpha (pI 5.2-5.8) by 2D PAGE. Neutrophil ficolin was consistent with ficolin beta by pI and peptide mass fingerprinting with matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. Porcine neutrophils expressed ficolin beta, but not ficolin alpha, as determined by RT-PCR. Ficolin beta was present in the membrane and cytoplasmic fractions of nonactivated neutrophils, but the majority of ficolin beta was secreted upon activation with PMA. Ficolin alpha readily bound to intact APP, but ficolin beta did not under the same conditions. These studies demonstrate that neutrophils express ficolin beta and secrete it when activated; however, ficolin beta may have different binding functions than ficolin alpha.

Amino Acid Sequence↗
PubMed2003

No strong relationship between mannan binding lectin or plasma ficolins and chemotherapy-related infections.

Chemotherapy causes neutropenia and an increased susceptibility to infection. Recent reports indicate that mannan-binding lectin (MBL) insufficiency is associated with an increased duration of febrile neutropenia and incidence of serious infections following chemotherapy for haematological malignancies. We aimed to confirm or refute this finding and to extend the investigation to the plasma ficolins, P35 (L-ficolin) and the Hakata antigen (H-ficolin). MBL, L-ficolin and H-ficolin were measured in 128 patients with haematological malignancies treated by chemotherapy alone or combined with bone marrow transplantation. Protein concentrations were related to clinical data retrieved from medical records. MBL concentrations were elevated compared with healthy controls in patients who received chemotherapy, while L-ficolin concentrations were decreased and H-ficolin levels were unchanged. There was no correlation between MBL, L-ficolin or H-ficolin concentration and febrile neutropenia expressed as the proportion of neutropenic periods in which patients experienced fever, and there was no relation between abnormally low (deficiency) levels of MBL, L-ficolin or H-ficolin and febrile neutropenia so expressed. Patients with MBL < or =0.1 microg/ml had significantly more major infections than no infections within the follow-up period (P<0.05), but overall most patients had signs or symptoms of minor infections irrespective of MBL concentration. Neither L-ficolin nor H-ficolin deficiencies were associated with infections individually, in combination or in combination with MBL deficiency. MBL, L-ficolin and H-ficolin, independently or in combination, did not have a major influence on susceptibility to infection in these patients rendered neutropenic by chemotherapy. These results cast doubt on the potential value of MBL replacement therapy in this clinical context.

Adolescent↗
PubMed1996

Biosynthesis of human ficolin, an Escherichia coli-binding protein, by monocytes: comparison with the synthesis of two macrophage-specific proteins, C1q and the mannose receptor.

Ficolin is characterized by the presence of both collagen-like and fibrinogen-like sequences, and potentially has a similar overall structure as the complement protein C1q and the collectins. Previous studies have reported the presence of human ficolin mRNA predominantly in peripheral blood leucocytes. In the present study, the cellular origin of human ficolin was investigated in further detail. Preliminary studies using reverse transcriptase-polymerase chain reaction (RT-PCR) showed that ficolin mRNA was synthesized by U937 cells, a human monocyte cell line. This finding suggested that blood monocytes also normally synthesize human ficolin. Peripheral blood monocytes from adult human donors were harvested at serial time-points (0-20 hr) after adhesion to tissue culture plates, and total RNA was isolated and assayed for ficolin mRNA by RT-PCR. Ficolin mRNA was highly expressed in monocytes throughout the first 20 hr of adhesion. In contrast, C1q and mannose receptor mRNA were not detectable during the first 8 hr of adhesion, but were highly expressed by 20 hr. Cells were harvested at longer time intervals (1, 2, 4, 6 and 8 days) to determine whether ficolin expression was temporally regulated at later stages of monocyte differentiation. Ficolin mRNA levels decreased sharply from day 1 to day 6. In contrast, the levels of both C1q and mannose receptor mRNA showed no changing trend. These results are consistent with the absence of ficolin expression in many macrophage-rich tissues previously reported. The origin of ficolin from monocytes, together with its structural similarity to C1q and the collectins, raises the possibility that ficolin may be another plasma protein capable of binding to surface structures of micro-organisms. Escherichia coli was therefore incubated with human serum, and bound proteins, after elution with sugars, were analysed by Western blotting using an antiserum raised against a synthetic ficolin peptide. The antiserum identified a polypeptide of approximately 42000 MW, which is similar in size to that of ficolin as predicted from its cDNA-derived sequence.

Blotting, Western↗
PubMed2003

Characterization of porcine plasma ficolins that bind Actinobacillus pleuropneumoniae serotype 5B.

Ficolins are collagenous lectins implicated in resistance to infection by some micro-organisms with surfaces containing N-acetylglucosamine residues. Pigs have two known ficolin genes, alpha and beta, but ficolins in pig plasma appear in various electrophoretic forms, the origin and function of which are unclear. In this investigation the forms of ficolin in pig plasma that bind to the pneumonic pathogen Actinobacillus pleuropneumoniae serotype 5b (APP5) were compared with affinity-purified porcine plasma ficolins. APP5-bound ficolins consisted of two distinct multimeric (non-denatured) forms composed of subunits that migrated as multiple 38,40 and 42 kDa forms (apparent MW) with pI range 5.2-6.0. The APPS-binding forms of ficolin were consistent with ficolin alpha and were indistinguishable from affinity-purified plasma ficolins by peptide mass fingerprint analysis. Subunit bands separated by 2D-PAGE were consistent with porcine ficolin alpha. Affinity-purified plasma ficolins had a major subunit mass of 35081 Da by MALDI-TOF MS. Affinity-purified ficolins digested with N-glycosidase F retained APP5-binding activity and migrated faster as a single band of 38 kDa. These studies indicate that ficolin alpha is the major APPS-binding form in porcine plasma and suggest that N-glycosylation contributes to the apparent electrophoretic heterogeneity of porcine ficolins but is not required for APP5-binding activity.

Actinobacillus pleuropneumoniae↗
PubMed2005

M-ficolin, an innate immune defence molecule, binds patterns of acetyl groups and activates complement.

Ficolins play a role in the innate immune defence as pathogen-associated molecular pattern recognition molecules. Three ficolins are found in humans: H-ficolin, L-ficolin and M-ficolin. L-ficolin and H-ficolin circulate in blood in complexes with mannan-binding lectin-associated serine proteases (MASPs) and are capable of activating the complement system. L-ficolin shows affinity for acetylated compounds and binds to various capsulated strains of bacteria. H-ficolin has been shown to bind Aerococcus viridans. Less is known about M-ficolin, but it is thought to be present only on monocytes. We have synthesized recombinant M-ficolin and find that it, in a manner similar to L-ficolin, is able to bind to acetylated compounds and to associate with recombinant MASP-2. Upon binding to M-ficolin ligands, the associated MASP-2 zymogen is activated and cleaves C4, thus triggering the complement system. We developed a monoclonal rat anti-human-M/L-ficolin antibody and verified by flow cytometric analysis the presence of ficolin on the surface of peripheral blood monocytes.

Acetylation↗
PubMed2002

Activation of the lectin complement pathway by H-ficolin (Hakata antigen).

Ficolins are a group of proteins which consist of a collagen-like domain and a fibrinogen-like domain. In human serum, there are two types of ficolins named L-ficolin/P35 and H-ficolin (Hakata Ag), both of which have lectin activity. We recently demonstrated that L-ficolin/P35 is associated with mannose-binding lectin (MBL)-associated serine proteases (MASP) 1 and 2 and small MBL-associated protein (sMAP), and that the complex activates the lectin pathway. In this study, we report the characterization of H-ficolin in terms of its ability to activate complement. Western blotting analysis showed the presence of MASP-1, MASP-2, MASP-3, and sMAP in H-ficolin preparations isolated from Cohn Fraction III. The MASPs in the preparations had proteolytic activities against C4, C2, and C3 in the fluid phase. When H-ficolin preparations were bound to anti-H-ficolin Ab which had been coated on ELISA plates, they activated C4, although no C4 activation was noted when anti-MBL and anti-L-ficolin/P35 were used. H-ficolin binds to PSA, a polysaccharide produced by Aerococcus viridans. C4 was activated by H-ficolin preparations bound to PSA which had been coated on ELISA plates. These results indicate that H-ficolin is a second ficolin which is associated with MASPs and sMAP, and which activates the lectin pathway.

Antibodies, Monoclonal↗
PubMed1998

Oligomeric structure and tissue distribution of ficolins from mouse, pig and human.

Mouse plasma ficolin was purified by GlcNAc affinity and anion-exchange chromatography. Gel-filtration chromatography and gradient sedimentation indicated that mouse plasma ficolin is a 12-mer of approximately 35 kDa subunits, and electron microscopy showed the same parachute-like structure previously characterized for the pig ficolin 12-mer. Whereas the predominant form in pig plasma is a 24-mer, mouse and human plasma ficolin showed only the 12-mer form. We conclude that mouse plasma ficolin corresponds to the recently described ficolin A. We have identified a second mouse ficolin gene, ficolin B, which means that pig and mouse each have two ficolin genes, and human has three. One ficolin gene in all species is expressed in liver and is the primary source of plasma ficolin. Expression of this gene in other tissues, and expression of the second ficolin gene, appears to vary in different species.

Amidohydrolases↗
PubMed2003

Molecular cloning and characterization of novel ficolins from Xenopus laevis.

Ficolins are proteins characterized by the presence of collagen- and fibrinogen-like domains. Two of three human ficolins, L-ficolin and H-ficolin, are serum lectins and are thought to play crucial roles in host defense through opsonization and complement activation. To elucidate the evolution of ficolins and the primordial complement lectin pathway, we cloned four ficolin cDNAs from Xenopus laevis, termed Xenopus ficolin (XeFCN) 1, 2, 3 and 4. The deduced amino acid sequences of the four ficolins revealed the conserved collagen- and fibrinogen-like domains. The full sequences of the four ficolins showed a 42-56% identity to human ficolins, and 60-83% between one another. Northern blots showed that XeFCN1 was expressed mainly in liver, spleen and heart, and XeFCN2 and XeFCN4 mainly in peripheral blood leukocytes, lung and spleen. We isolated ficolin proteins from Xenopus serum by affinity chromatography on N-acetylglucosamine-agarose, followed by ion-exchange chromatography. The final eluate showed polymeric bands composed of two components of 37 and 40 kDa. The N-terminal amino acid sequences and treatment with endoglycosidase F showed that the two bands are the same XeFCN1 protein with different masses of N-linked sugar. The polymeric form of the two types of XeFCN1 specifically recognized GlcNAc and GalNAc residues. These results suggest that like human L-ficolin, XeFCN1 functions in the circulation through its lectin activity.

Amino Acid Sequence↗
PubMed2000

M-ficolin is expressed on monocytes and is a lectin binding to N-acetyl-D-glucosamine and mediates monocyte adhesion and phagocytosis of Escherichia coli.

Ficolins are a group of multimeric proteins that contain collagen-like and fibrinogen-like (FBG) sequences. Three types of ficolins have been characterized: H-, L- and M-ficolins. Both H- and L-ficolins have demonstrated lectin activities. In the present study, the FBG domain of M-ficolin was expressed and shown to bind to N-acetyl-D-glucosamine. M-ficolin mRNA was expressed in monocytes but not in the more differentiated macrophages and dendritic cells. By flow cytometry, surface biotinylation and immunoprecipitation, we showed that M-ficolin was associated with the surface of promonocytic U937 cells. M-ficolin transiently expressed in COS-7 cells was also clearly detected on the cell surface by immunoprecipitation. By flow cytometry, M-ficolin was detected on peripheral blood monocytes but not on lymphocytes or granulocytes. Immobilized rabbit anti-M-ficolin F(ab')2 mediated U937 cell adhesion, and the antibody also inhibited phagocytosis of Escherichia coli K-12 by U937 cells. Therefore, M-ficolin might act as a phagocytic receptor or adaptor on circulating monocytes for micro-organism recognition and may potentially mediate monocyte adhesion.

Acetylglucosamine↗
PubMed1997

Two oligomeric forms of plasma ficolin have differential lectin activity.

Ficolins are plasma proteins with binding activity for carbohydrates, elastin, and corticosteroids. The ficolin polypeptide has a collagen-like domain that presumably brings three subunits together in a triple helical rod, a C-terminal fibrinogen-like domain (fbg) similar to that of tenascin, which presumably has the binding activities, and a small N-terminal domain that we find to be the primary site for forming the ficolin oligomer. By sedimentation equilibrium we determined that the main plasma form, which we call big ficolin, had mass of 827,000 Da, consistent with 24 subunits. Little ficolin, about half this size, was obtained after binding to a GlcNAc affinity column. Electron microscopy of little ficolin showed a parachute-like structure, with a small globe at one end, corresponding to the 12 N-terminal domains, and the fbg domains clustered together at the ends of the collagen rods. Big ficolin was formed by the face to face fusion of the fbg domains of two little ficolins, leaving the rods and N-terminal domains projecting at opposite ends. Little ficolin maintained a high affinity for the GlcNAc column, and big ficolin had a low affinity or none. The binding sites for ligands may be obscured in this big ficolin oligomer, providing a regulation of their activity.

Animals↗
PubMed1993

Molecular cloning and characterization of ficolin, a multimeric protein with fibrinogen- and collagen-like domains.

We have previously identified and purified transforming growth factor-beta 1 (TGF-beta 1)-binding proteins from porcine uterus membranes (Ichijo, H., Rönnstrand, L., Miyagawa, K., Ohashi, H., Heldin, C.-H., and Miyazono, K. (1991) J. Biol. Chem. 266, 22459-22464). One of these TGF-beta 1-binding proteins, with a molecular weight of 40,000, was purified to homogeneity and subjected to amino acid sequence analysis. The amino acid sequences obtained were used to isolate two closely related cDNA clones from a porcine uterus cDNA library. The deduced amino acid sequences revealed that both cDNAs encoded proteins that were mainly composed of fibrinogen-like and collagen-like domains. Therefore, they were denoted ficolin-alpha and ficolin-beta. Expression of ficolin-alpha and -beta cDNA in mammalian cells revealed that ficolin forms dimers, trimers, and several higher order of oligomers, whose molecular weights fit well with those of the purified TGF-beta 1-binding proteins from porcine uterus. Moreover, immunoblotting analysis using a peptide anti-serum against ficolin indicated that the TGF-beta 1-binding proteins identified in porcine uterus are ficolin-alpha, -beta, and their oligomers or closely related molecules. However, recombinant ficolin-alpha and -beta did not bind TGF-beta 1, despite the similarities in molecular weights and immunoreactivity with the material from the natural source. It is possible that a specific posttranslational modification of ficolin or interaction with another component is needed for TGF-beta 1 binding. Analysis by Northern blotting revealed that the expression of ficolin-alpha mRNA is relatively restricted and most abundant in placenta and lung. On the other hand, ficolin-beta was mainly expressed in skeletal muscle. The in vivo functions of ficolin will be discussed.

Amino Acid Sequence↗