C-type Lectin Domain Family Research Articles

Identification of Tetranectin as a Potential Biomarker for Metastatic Oral Cancer

Lymph node involvement is the most important predictor of survival rates in patients with oral squamous cell carcinoma (OSCC). A biomarker that can indicate lymph node metastasis would be valuable to classify patients with OSCC for optimal treatment. In this study, we have performed a serum proteomic analysis of OSCC using 2-D gel electrophoresis and liquid chromatography/tandem mass spectrometry. One of the down-regulated proteins in OSCC was identified as tetranectin, which is a protein encoded by the CLEC3B gene (C-type lectin domain family 3, member B). We further tested the protein level in serum and saliva from patients with lymph-node metastatic and primary OSCC. Tetranectin was found significantly under-expressed in both serum and saliva of metastatic OSCC compared to primary OSCC. Our results suggest that serum or saliva tetranectin may serve as a potential biomarker for metastatic OSCC. Other candidate serum biomarkers for OSCC included superoxide dismutase, ficolin 2, CD-5 antigen-like protein, RalA binding protein 1, plasma retinol-binding protein and transthyretin. Their clinical utility for OSCC detection remains to be further tested in cancer patients.

Genetics of the Autoimmune Polyglandular Syndrome Type 3 Variant

Autoimmune thyroid diseases (AITD) and type 1 diabetes (T1D) are the most common autoimmune endocrine disorders. They occur frequently together in the same individual. This disease combination is denominated as autoimmune polyglandular syndrome type 3 variant (APS3v). This review aims to describe the genetic and pathological background of the syndrome. The joint susceptibility genes for AITD and T1D as well as the underlying pathogenetic mechanisms contributing to the development of autoimmunity are summarized. Family and population studies showed that the APS3v syndrome has a strong genetic background. Whole genome and candidate gene approaches identified several gene variations that are present in both AITD and T1D. Most important common disease susceptibility genes are human leucocyte antigen (chromosome 6), cytotoxic T-lymphocyte-associated antigen 4 (chromosome 2), protein tyrosine phosphatase nonreceptor type 22 (chromosome 1), forkhead box P3 (X chromosome), and the interleukin-2 receptor alpha/CD25 gene region (chromosome 10), all of which contributing to the susceptibility to APS3v. With respect to the underlying pathogenetic mechanisms, these genes are altogether involved in the immune regulation, in particular in the immunological synapse and T-cell activation. In addition to these common genes, there are further candidate genes with joint risk for AITD and T1D, in particular the v-erb-b2 erythroblastic leukemia viral oncogene homolog 3 gene (chromosome 12) and C-type lectin domain family 16 member A gene (chromosome 16). The latter one might be involved in pathogen recognition. AITD and T1D share common susceptibility gene variants that possibly act pleiotropically as risk factors for the development of autoimmunity in APS3v. The functional consequences of the genetic variants as well as their interactions should be explored in greater detail. In particular, the functional consequences of the variants of forkhead box P3 predisposing to APS3v need to be elucidated. Finally, further large-scale genome-wide associations studies of single-nucleotide polymorphism variations capturing many thousand individual genetic profiles are warranted to identify further genes that are linked to the etiology of APS3v.

Dexamethasone synergistically increases secretion of the anti-inflammatory cytokine interleukin(IL)-10 in murine dendritic cells (DCs) upon viral infection: Potential implication to stress-mediated modification of susceptibility to viral infection. (94.4)

Abstract Glucocorticoids (GC) are end-products of the HPA axis, which play central roles in stress response, including pathogen infection, and are widely used as therapeutic agents for inflammatory diseases. It is known that stressed condition altered the susceptibility to viral infection. Since it is not known how GC influence the function of DCs upon viral infection, we infected murine DC with Newcastle disease virus (NDV) in the presence of glucocorticoid receptor (GR) ligand dexamethasone (Dex), and examined mRNA expression of 84 genes, which play various roles in the TLR signaling cascade. We found that NDV infection potently induced mRNA expression of 24 genes. Among them, 7 genes (interferon (IFN)-γ, interleukin (IL)-6, IL-10, lymphotoxin A, C-type lectin domain family 4, nuclear factor of κ light chain gene enhancer in B cell inhibitor β and prostaglandin-endoperoxidase synthase 2) were further up- or down-regulated by Dex pre-treatment. Particularly on IL-10, Dex synergistically up-regulated NDV-induced mRNA by 7-fold. The Dex effect was mediated by GR, as inhibitor RU 486 abolished the effect. In contrast to IFN-γ and IL-6, which are Th1 cytokines and response at early time point (6 h), kinetics of IL-10 mRNA showed the highest synergistic effect of NDV and Dex at a later time point (24 h). ELISA results showed consistent results with mRNA expression. Taken together, our study indicates that GC modulate host immunity, altering TLR-related gene expression in DCs.

A Novel Functional Variant in the Stem Cell Growth Factor Promoter Protects against Severe Malarial Anemia

Plasmodium falciparum malaria is a leading global cause of infectious disease burden. In areas in which P. falciparum transmission is holoendemic, such as western Kenya, severe malarial anemia (SMA) results in high rates of pediatric morbidity and mortality. Although the pathophysiological basis of SMA is multifactorial, we recently discovered that suppression of unexplored hematopoietic growth factors that promote erythroid and myeloid colony development, such as stem cell growth factor (SCGF) (C-type lectin domain family member 11A [CLEC11A]), was associated with enhanced development of SMA and reduced erythropoietic responses. To extend these investigations, the relationships between a novel SCGF promoter variant (-539C/T, rs7246355), SMA (hemoglobin [Hb] < 6.0 g/dl), and reduced erythropoietic responses (reticulocyte production index [RPI], <2.0) were investigated with Kenyan children (n = 486) with falciparum malaria from western Kenya. Circulating SCGF was positively correlated with hemoglobin levels (r = 0.251; P = 0.022) and the reticulocyte production index (RPI) (r = 0.268; P = 0.025). Children with SMA also had lower SCGF levels than those in the non-SMA group (P = 0.005). Multivariate logistic regression analyses controlling for covariates demonstrated that individuals with the homologous T allele were protected against SMA (odds ratio, 0.57; 95% confidence interval [95% CI] 0.34 to 0.94; P = 0.027) relative to CC (wild-type) carriers. Carriers of the TT genotype also had higher SCGF levels in circulation (P = 0.018) and in peripheral blood mononuclear cell culture supernatants (P = 0.041), as well as an elevated RPI (P = 0.005) relative to individuals with the CC genotype. The results presented here demonstrate that homozygous T at -539 in the SCGF promoter is associated with elevated SCGF production, enhanced erythropoiesis, and protection against the development of SMA in children with falciparum malaria.

C-type lectin domain family 7 member A (CLEC7A; DECTIN1)

C-type lectin domain family 7 member A (CLEC7A; DECTIN1)

Single nucleotide polymorphism of TAG-1 influences IVIg responsiveness of Japanese patients with CIDP

Chronic inflammatory demyelinating polyneuropathy (CIDP) is characterized by immune-mediated peripheral demyelination. Although corticosteroid, IV immunoglobulin (IVIg) and plasma exchange have been established as the most effective therapeutics, subpopulations of patients show little or no response to either of these therapies. In this study, we examined whether particular genetic factors influence the therapeutic responsiveness of patients with CIDP. One hundred Japanese patients categorized as responders or nonresponders to IVIg therapy participated in our study. We performed an association analysis with single nucleotide polymorphisms (SNPs) and haplotype studies between the IVIg responders and nonresponders. Two separate SNPs, corresponding to TAG-1 (transient axonal glycoprotein 1) and CLEC10A (C-type lectin domain family 10, member A), showed strong significant differences between responders and nonresponders. Haplotype analysis of a series of expanded SNPs, from TAG-1 or CLEC10A, showed that only TAG-1 included a significant haplotype within 1 linkage disequilibrium block, which accommodates IVIg responsiveness. Diplotype analysis of TAG-1 also supported this observation. Transient axonal glycoprotein 1 is a crucial molecule involved in IV immunoglobulin responsiveness in Japanese patients with chronic inflammatory demyelinating polyneuropathy.

C-type lectin domain family 7, member A (CLEC7; DECTIN1); C-type lectin domain family 6, member A (CLEC6; DECTIN2)

C-type lectin domain family 7, member A (CLEC7; DECTIN1); C-type lectin domain family 6, member A (CLEC6; DECTIN2)

Suppression of a Novel Hematopoietic Mediator in Children with Severe Malarial Anemia

In areas of holoendemic Plasmodium falciparum transmission, severe malarial anemia (SMA) is a leading cause of pediatric morbidity and mortality. Although many soluble mediators regulate erythropoiesis, it is unclear how these factors contribute to development of SMA. Investigation of novel genes dysregulated in response to malarial pigment (hemozoin [PfHz]) revealed that stem cell growth factor (SCGF; also called C-type lectin domain family member 11A [CLEC11A]), a hematopoietic growth factor important for development of erythroid and myeloid progenitors, was one of the most differentially expressed genes. Additional experiments with cultured peripheral blood mononuclear cells (PBMCs) demonstrated that PfHz decreased SCGF/CLEC11A transcriptional expression in a time-dependent manner. Circulating SCGF levels were then determined for Kenyan children (n = 90; aged 3 to 36 months) presenting at a rural hospital with various severities of malarial anemia. SCGF levels in circulation (P = 0.001) and in cultured PBMCs (P = 0.004) were suppressed in children with SMA. Circulating SCGF also correlated positively with hemoglobin levels (r = 0.241; P = 0.022) and the reticulocyte production index (RPI) (r = 0.280; P = 0.029). In addition, SCGF was decreased in children with reduced erythropoiesis (RPI of <2) (P < 0.001) and in children with elevated levels of naturally acquired monocytic PfHz (P = 0.019). Thus, phagocytosis of PfHz promotes a decrease in SCGF gene products, which may contribute to reduced erythropoiesis in children with SMA.

Cytoplasmic Proteome and Secretome Profiles of Differently Stimulated Human Dendritic Cells

Dendritic cells (DCs), the most potent and specialized antigen-presenting cells, play a key role in the regulation of the adaptive immunity. Immature DCs were generated by in vitro culturing of peripheral blood monocytes and functionally activated with the classical pathogen-associated molecular pattern lipopolysaccharide (LPS). Alternative activation resulting in Th-2 polarization was induced with lipid oxidation products derived from 1-palmitoyl-2-arachidoyl-sn-glycerol-3-phosphorylcholin (OxPAPC). Tolerogenic cells were obtained by treating DCs with human rhinovirus (HRV). The aim of this study was the identification of proteome profiles related to the functionally different dendritic cell phenotypes. Cytoplasmic proteins were analyzed by shotgun proteomics resulting in the identification of 1690 proteins. While mature and alternatively activated DCs displayed highly distinct protein expression profiles, HRV-treated DCs showed minor proteome alterations. As DCs exert many specific functions via secretion, we investigated the secretomes by a combination of 2D-PAGE and shotgun proteomics. We successfully identified a broad variety of cytokines (e.g., GM-CSF, TNF-alpha, interleukin-1beta, 6, 12 beta, 28B and 29), chemokines (e.g., CCL3, 5, 8, 17, 18, 19, 24, CXCL1, 2, 9 and 10) and growth factors (growth/differentiation factor 8, C-type lectin domain family 11 member A). The relative composition of secretome profiles, although comprising much less proteins, was found to be much more affected by functional alteration of cells than the cytoplasmic protein composition. In conclusion, we demonstrate that functional distinct subsets of DCs display distinct proteome profiles which comprise biomarker candidates. These proteins may prove useful for the interpretation of complex clinical proteomics data.

C-type lectin domain family 9, member A (CLEC9A; DNGR1)

C-type lectin domain family 9, member A (CLEC9A; DNGR1)

Matrilysin (MMP‐7) cleaves C‐type lectin domain family 3 member A (CLEC3A) on tumor cell surface and modulates its cell adhesion activity

Matrilysin (MMP-7) plays important roles in tumor progression. Previous studies have suggested that MMP-7 binds to tumor cell surface and promotes their metastatic potential. In this study, we identified C-type lectin domain family 3 member A (CLEC3A) as a membrane-bound substrate of MMP-7. Although this protein is known to be expressed specifically in cartilage, its message was found in normal breast and breast cancer tissues as well as breast and colon cancer cell lines. Because few studies have been done on CLEC3A, we overexpressed its recombinant protein in human cancer cells. CLEC3A was found in the cell membrane, extracellular matrix (ECM), and culture medium of the CLEC3A-expressing cells. CLEC3A has a basic sequence in the NH(2)-terminal domain and showed a strong heparin-binding activity. MMP-7 cleaved the 20-kDa CLEC3A protein, dividing it to a 15-kDa COOH-terminal fragment and an NH(2)-terminal fragment with the basic sequence. The 15-kDa fragment no longer had heparin-binding activity. Treatment of the CLEC3A-expressing cells with MMP-7 released the 15-kDa CLEC3A into the culture supernatant. Furthermore, the 20-kDa CLEC3A promoted cell adhesion to laminin-332 and fibronectin substrates, but this activity was abrogated by the cleavage by MMP-7. These results suggest that CLEC3A binds to heparan sulfate proteoglycans on cell surface, leading to the enhancement of cell adhesion to integrin ligands on ECM. It can be speculated that the cleavage of CLEC3A by MMP-7 weakens the stable adhesion of tumor cells to the matrix and promotes their migration in tumor microenvironments.

Expression and functional role of MDL-1 (CLEC5A) in mouse myeloid lineage cells

Myeloid DNAX activation protein 12 (DAP12)-associating lectin-1 (MDL-1), also known as C-type lectin domain family 5, member A, is a type II transmembrane protein belonging to the C-type lectin family and associates with DAP12 (also called KARAP or TYROBP). It has been reported that two isoforms of MDL-1-long form (MDL-1L) and short form (MDL-1S)-exist in mice. Previously, we observed the marked induction of MDL-1 mRNA expression during the pulmonary mycobacterial infection in mice. The data suggested that the MDL-1-expressing cells were involved in immune responses against mycobacterial infection; however, little is known about the function of MDL-1 as yet. In this study, we demonstrated the significant protein expression of MDL-1L and MDL-1S in mouse neutrophils and macrophages. MDL-1L was highly glycosylated by N-linked glycan and sialic acid. Interestingly, the expression pattern of MDL-1 was different between neutrophils and macrophages. MDL-1 expression was notably induced during the differentiation of the mouse myeloid cell line 32Dcl3 into neutrophils. Additionally, we observed that MDL-1 stimulation induced a significant amount of RANTES and macrophage-derived chemokine production in 32Dcl3 cells in cooperation with signaling through TLR. MDL-1 stimulation also up-regulated CD11b expression and maintained cell survival. Our findings indicate that MDL-1, therefore, plays an important role in immune defense as a result of an innate immunity, which involves neutrophils and macrophages.

C-type lectin domain family 4, member E (CLEC4E; MINCLE)

C-type lectin domain family 4, member E (CLEC4E; MINCLE)

CLEC5A is critical for dengue-virus-induced lethal disease

Dengue haemorrhagic fever and dengue shock syndrome, the most severe responses to dengue virus (DV) infection, are characterized by plasma leakage (due to increased vascular permeability) and low platelet counts. CLEC5A (C-type lectin domain family 5, member A; also known as myeloid DAP12-associating lectin (MDL-1)) contains a C-type lectin-like fold similar to the natural-killer T-cell C-type lectin domains and associates with a 12-kDa DNAX-activating protein (DAP12) on myeloid cells. Here we show that CLEC5A interacts with the dengue virion directly and thereby brings about DAP12 phosphorylation. The CLEC5A-DV interaction does not result in viral entry but stimulates the release of proinflammatory cytokines. Blockade of CLEC5A-DV interaction suppresses the secretion of proinflammatory cytokines without affecting the release of interferon-alpha, supporting the notion that CLEC5A acts as a signalling receptor for proinflammatory cytokine release. Moreover, anti-CLEC5A monoclonal antibodies inhibit DV-induced plasma leakage, as well as subcutaneous and vital-organ haemorrhaging, and reduce the mortality of DV infection by about 50% in STAT1-deficient mice. Our observation that blockade of CLEC5A-mediated signalling attenuates the production of proinflammatory cytokines by macrophages infected with DV (either alone or complexed with an enhancing antibody) offers a promising strategy for alleviating tissue damage and increasing the survival of patients suffering from dengue haemorrhagic fever and dengue shock syndrome, and possibly even other virus-induced inflammatory diseases.

Proinflammatory Response of Immature Human Dendritic Cells is Mediated by Dectin‐1 after Exposure toAspergillus fumigatusGerm Tubes

Invasive fungal infections caused by Aspergillus fumigatus represent a great challenge for immunocompromised patients. Pathogen detection is mediated by different receptors, including Toll-like receptors (TLRs), C-type lectins, and pentraxines. However, little is known about their relevance for immature human dendritic cells (iDCs). The gene expression pattern of iDCs after exposure to A. fumigatus germ tubes was studied by use of whole genome microarray analysis and real-time polymerase chain reaction. Fungal receptors were targeted by means of short interfering RNAs (siRNAs), which were used to knock down expression of TLR2, TLR4, DC-SIGN (dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin), PTX3 (pentraxin-related gene), dectin-1 (C-type lectin domain family 7, member A), and CARD9 (caspase recruitment domain family, member 9). Exposure to A. fumigatus induced expression of cytokines, chemokines, costimulatory molecules, and genes involved in prostaglandin synthesis, as well as genes related to fungal recognition and phagocytosis. Silencing of dectin-1 resulted in reduced expression of proinflammatory cytokines (tumor necrosis factor-alpha and interleukin-12), which was also reduced by anti-Dectin-1 antibody treatment prior to exposure to A. fumigatus, zymosan, or Candida albicans. Dectin-1 was identified as an important receptor for A. fumigatus and C. albicans on human iDCs and was found to be involved in the induction of a proinflammatory cytokine response.

CLEC2A: a novel, alternatively spliced and skin-associated member of the NKC-encoded AICL–CD69–LLT1 family

The human natural killer gene complex (NKC) encodes for numerous C-type lectin-like receptors (CTLR), which are expressed on various immune cells including natural killer (NK) cells and myeloid cells. Certain activation-induced, NKC-encoded CTLR are grouped into the C-type lectin domain family 2 (CLEC2 family) which, in humans, comprises AICL (CLEC2B), CD69 (CLEC2C), and LLT1 (CLEC2D). In this paper, we characterize a novel member of the CLEC2 family, the human orphan gene CLEC2A. The C-type lectin-like domain (CTLD) of CLEC2A is most similar to the CTLD of LLT1 ( approximately 60% similarity). Like mouse CLEC2 family members Clr-b and Clr-g, CLEC2A lacks two highly conserved cysteines (Cys4 and Cys5), which form an intramolecular bond in the CTLD of most CTLR. Alternative splicing of exon 2 and of two distinct terminal exons (exon 5A/B), respectively, gives rise to four CLEC2A variants differing in the usage of the transmembrane domain and/or in the carboxyterminal portion of the CTLD. CLEC2A transcripts were detected primarily in myeloid cell lines, but not in epithelial cell lines. In tissues, CLEC2A is selectively expressed in the skin and, at lower abundance, in hematopoietic and gonadal tissues. Finally, we show that the CLEC2A1 variant is readily expressed at the cell surface, where it may serve as a ligand for NKC-encoded NK receptors.

Quantitative trait loci influencing low density lipoprotein particle size in African Americans

Genomic regions that influence LDL particle size in African Americans are not known. We performed family-based linkage analyses to identify genomic regions that influence LDL particle size and also exert pleiotropic effects on two closely related lipid traits, high density lipoprotein cholesterol (HDL-C) and triglycerides, in African Americans. Subjects (n = 1,318, 63.0 +/- 9.5 years, 70% women, 79% hypertensive) were ascertained through sibships with two or more individuals diagnosed with essential hypertension before age 60. LDL particle size was measured by polyacrylamide gel electrophoresis, and triglyceride levels were log-transformed to reduce skewness. Genotypes were measured at 366 microsatellite marker loci distributed across the 22 autosomes. Univariate and bivariate linkage analyses were performed using a variance components approach. LDL particle size was highly heritable (h(2) = 0.78) and significantly (P < 0.0001) genetically correlated with HDL-C (rho(G) = 0.32) and log triglycerides (rho(G) = -0.43). Significant evidence of linkage for LDL particle size was present on chromosome 19 [85.3 centimorgan (cM), log of the odds (LOD) = 3.07, P = 0.0001], and suggestive evidence of linkage was present on chromosome 12 (90.8 cM, LOD = 2.02, P = 0.0011). Bivariate linkage analyses revealed tentative evidence for a region with pleiotropic effects on LDL particle size and HDL-C on chromosome 4 (52.9 cM, LOD = 2.06, P = 0.0069). These genomic regions may contain genes that influence interindividual variation in LDL particle size and potentially coronary heart disease susceptibility in African Americans.

Identification and gene expression of the bovine C-type lectin Dectin-1

C-type lectin receptors (CTLR) are cell-surface signalling molecules that recognize a range of highly conserved pathogen molecules and instigate the appropriate immune response. Here, we report the cloning, sequencing, mapping and expression pattern of the bovine C-type lectin domain family 7, member A (CLEC7A; synonyms CLCSF12, Dectin-1). We identified two isoforms, similar to the human system, with a long and short neck. Overall, the organization of the two bovine CLEC7A genes is similar to that of humans and mice. The CLEC7A gene maps on Bos taurus chromosome 5 (BTA5). mRNA transcripts for CLEC7A were detected in bone-marrow cells, monocytes, macrophages and dendritic cells and NK cells, but not in CD4 + T-cells or CD21 + B-cells. The increased knowledge of the genomic organization of the bovine CTLR genes may promote our understanding of their evolution and help in the identification of bovine genes underlying disease-resistance traits.

Tissue-specific expression of Clec2g in mice

Estrogens regulate the proliferation and differentiation of mouse vaginal epithelial cells. We examined the temporal and spatial expression of DDV10, a novel C-type lectin during stratification and cornification of the vaginal epithelium. DDV10 was expressed in vagina but not uterus in ovariectomized mice treated with 17 β-estradiol (E2). In mouse stomach, the expression of DDV10 was detected in pars proventricularis but not in pars glandularis. Furthermore, the DDV10 gene was found to possess two transcripts, a long form (DDV10) and a short form (OCILrP1, osteoclast inhibitory lectin-related protein 1). DDV10 mRNA but not OCILrP1 mRNA was expressed in the stratified and cornified epithelial tissues. DDV10 mRNA was first detected between 12 and 18 h after E2 treatment in the vaginal epithelium, and was detected in the vagina of the neonatally diethylstilbestrol (DES)-treated mouse. Recently, a unified name was registered in GenBank (C-type lectin domain family 2, member g; Clec2 g). Taken together, these data suggest that DDV10 is the long form of Clec2 g (Clec2g-L), and DDV10/Clec2g-L may play a role in the stratification and/or cornification of epithelial cells during differentiation.

Cloning, Mapping, and Genomic Organization of the LSLCL Gene, Encoding a New Lymphocytic Secreted Mucin-like Protein with a C-Type Lectin Domain: A New Model of Exon Shuffling

The lipotoxicity is considered as one of the risk for diabetes. Here we report C-type lectin domain family 11, member A (Clec11a) as a new regulator in islet playing a protective role in lipotoxicity induced dysfunction. Islet transcriptome sequencing was performed using the high-fat diet induced obesity (DIO) mice model. We found a significant decrease of Clec11a expression in islets of DIO mice compared to normal control mice, which was further confirmed by real-time PCR. Immunostaining demonstrated the localization of the Clec11a protein in mouse islets. Administration of recombinant human Clec11a (rClec11a) protein promoted the proliferation of islet cells and rescued the inhibition of fatty acid on cell proliferation, which involved the activation of Erk signaling pathway. We also found that the rClec11a altered the expression of genes involved in lipid metabolism.