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Sex-dependent influence of LMAN1 on allergen-induced airway hyperresponsiveness.

Allergic asthma is a chronic inflammatory disease of the airways characterized by a type 2-high adaptive immune response towards common aeroantigens such as dust mite, pollen, and animal dander. Despite the advances made toward translation of various biologics into the clinic, the limited efficacy of these therapies in certain populations, combined with the ineligibility of some patients for treatment (clinically or economically), have led to the continued need for the development of more widely effective allergic asthma therapies. Our lab previously identified lectin mannose-binding 1 (LMAN1) as a novel receptor for house dust mite (HDM) and showed that in vitro, LMAN1 downregulated inflammatory NF-κB signaling in DCs in response to HDM. In this follow-up work, we investigated the in vivo relevance of LMAN1 by subjecting LMAN1 knockout (KO) mice and wild type (WT) littermate controls to a model of HDM-induced allergic asthma. Surprisingly, we discovered that loss of LMAN1 led to opposing effects on airway hyperresponsiveness (AHR), which were dependent on the sex of the mice. HDM-treated female LMAN1 KO mice showed increased AHR, while HDM-treated male KO mice showed decreased AHR, compared with their WT counterparts. We further identified the features of HDM-induced asthma which may account for the gender-biased effects of LMAN1 on lung function. This work not only highlights the complexity of the loss of LMAN1 in vivo but also suggests that such sex-dependent responses should be taken into consideration when pursuing LMAN1 as a therapeutic target for treatment of allergic asthma.

Animals↗

The chemical characterization of favin, a lectin isolated from Vicia faba.

We have determined the subunit structure of the glucose- and mannose-binding lectin favin, from Vicia faba. The molecule is composed of two nonidentical polypeptide chains held together by noncovalent interactions. We have determined the complete amino acid sequence of the smaller alpha chain (Mr = 5,571) and shown that it is homologous to the alpha chain of the lectins from lentil and pea and to residues 72 to 120 of concanavalin A (Con A). The larger beta chain (Mr = 20,000) contains carbohydrate and is homologous to the beta chain of lentil, pea, soybean, peanut, and red kidney bean lectins and is homologous to a portion of the Con A molecule beginning at residue 122. Favin also contains a minor component, beta' (Mr = 18,700), that closely resembles the beta chain but lacks carbohydrate and may, on the basis of apparent molecular weight, lack some part of the COOH-terminal region of the polypeptide chain. Although favin is similar to Con A, it, like the lentil and pea lectins, appears to lack residues corresponding to positions 1 to 71 of Con A. Because these residues contribute significantly to the carbohydrate binding site of Con A, the lack of this region in the otherwise homologous lectin favin suggests that the carbohydrate binding site of favin differs from that of Con A or that the region represented by residues 1 to 71 of Con A is located in a different portion (i.e. in the beta chain) of the favin molecule.

Amino Acid Sequence↗

Qingfei Dayuan granules alleviate the inflammatory response in lipopolysaccharide-induced acute lung injury mice by inhibiting the Nf-κB signaling pathway and regulating the complement pathway.

OBJECTIVES: The study aimed to explore the effects and mechanisms by which Qingfei Dayuan granules (QFDY) mitigate pulmonary inflammation in lipopolysaccharide (LPS)-induced acute lung injury (ALI). METHODS: We established an ALI mouse model by intraperitoneal injection of LPS. HE, Transmission electron microscopy, ELISA assay of inflammatory cytokines, and immunohistochemistry (IHC) were used to assess the degree of lung injury and inflammation. Utilizing network analysis and proteomics analysis, the potential targets and pathways of QFDY were identified. Western blot, IHC, and qRT-PCR analysis were used to evaluate the potential mechanism of QFDY. Additionally, the chemical composition of QFDY were performed using UPLC-MS/MS. KEY FINDINGS: QFDY reduced the pathologic changes and inflammatory cell infiltration in lung tissue inflammation. Network and proteomic analysis showed that the mechanism of QFDY protection against ALI is closely related to the Nuclear factor-kappa B (NF-κB) signaling pathway and complement pathway. Animal experiments showed that Qingfei Dayuan granules (QFDY) significantly reduced the levels of IL-1β, IL-6, TNF-α, and lung tissue F4/80-positive alveolar macrophages. Additionally, western blot and qRT-PCR analyses showed the inhibition of the NF-κB pathway. Notably, the levels of mannose-binding lectin (MBL2) were significantly increased, while complement C3a and complement C5a proteins were reduced in the QFDY group compared to the LPS group. CONCLUSIONS: QFDY suppressed the inflammation in LPS-induced ALI by inhibiting the NF-κB and complement pathway.

Animals↗

Purification of immunoprecipitated pemphigus foliaceus antigen fragment and its use in radioimmunoassay.

A major difficulty in biochemical studies of the pemphigus foliaceus (PF) antigen is the lack of a method for its quantitative determination. Immunofluorescence blocking and immunoprecipitation methods are semiquantitative and time consuming. Radioimmunoassay (RIA) methods are quantitative but they require pure and stable antigen preparations that have not been available for PF. The present investigation shows the further purification of a previously described preparation of PF antigen fragment obtained from trypsinization media of mouse skin (Con A Frn) and demonstrates its usefulness in a RIA method for quantitation of the antigen. The major contaminants of the 45-kD tryptic fragment of the PF antigen (tf-PF) in immunoprecipitates of the Con A Frn with PF sera were identified as H and L chains of murine IgG and mannose-binding lectins. The IgG contaminants could be removed by avoidance of blood contamination during preparation of the Con A Frn and/or pre-absorption of the Con A Frn with protein A Sepharose. The lectins could be removed by affinity chromatography of the Con A Frn on asialofetuin column and washing the immunoprecipitates with 0.2 M alpha-methyl-mannoside. Using the purified, labeled Con A Frn in RIA, we showed that standard curves could be established and the amounts of PF antigen could be determined in different extracts without the need for electrophoresis, autoradiography, or scanning. This RIA method is rapid and can be easily used to analyze many samples, e.g., chromatographic fractions and extracts made from different tissues.

Animals↗

Carbohydrate moieties of myelin-associated glycoprotein, major glycoprotein of the peripheral nervous system myelin and other myelin glycoproteins potentially involved in cell adhesion.

The myelin-associated glycoprotein (MAG) and the major glycoprotein of the peripheral nervous system myelin (P0) are two members of the family of cell adhesion molecules (CAMs). A role in cell adhesion of the carbohydrate moiety of these molecules has been attributed to the presence of N-glycans bearing the HNK-1 carbohydrate epitope. On the other hand, it has been suggested that these glycoproteins could be ligands of an endogenous mannose-binding lectin present in myelin, the cerebellar soluble lectin (CSL). In order to further document the heterogeneity of the glycans of these two CAMs, we have used several probes: an anti-carbohydrate antibody of the HNK-1 type, called Elec-39, the plant lectin concanavalin A (ConA), and the endogenous lectin CSL involved in myelin compaction. This study shows that CSL binds to a small proportion of the polypeptide chains of MAG found in adult CNS of rats and man and the polypeptide chains of P0 molecules from adult human and rat sciatic nerve. For MAG from adult rat brain, the binding of CSL is restricted to glycans of polypeptide chains which could be separated from the others according to their solubility properties. These MAG molecular entities react also with the Elec-39 antibody and with ConA. These results confirm that P0 and MAG are heterogeneous in their carbohydrate moieties.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Large-Scale Proteomic Profiling of Incident Heart Failure and Its Subtypes in Older Adults.

BACKGROUND: Heart failure (HF) and its main subtypes, heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF), impose an enormous health burden on elders. Assessment of the circulating proteome to illuminate pathogenesis could open new opportunities for treatment. METHODS: We conducted a plasma proteomics screen of incident HF and its subtypes in 2 older population-based cohorts, the CHS (Cardiovascular Health Study) and the AGES-RS (Aging, Gene/Environment Susceptibility-Reykjavik Study). The 2 studies used SomaLogic platforms, with 4404 aptamers in common. Multivariable Cox models were fit to evaluate individual-protein associations with HF, HFpEF, and HFrEF separately in each cohort, and study-specific associations were combined by fixed-effects meta-analysis. Replication was performed in the ARIC (Atherosclerosis Risk in Communities) cohort. Two-sample Mendelian randomization of HF and its subtypes, along with colocalization analysis, was performed to support causal inference. RESULTS: Among 8599 participants, 1590 experienced incident HF (536 HFpEF, 471 HFrEF). There were 119 proteins associated with HF, 15 proteins with HFpEF, and 11 proteins with HFrEF, at Bonferroni-corrected significance. Among these, 9 have never previously been identified for cardiovascular diseases, and another 61 represent new associations with incident HF or its subtypes. Of these 70 proteins, 55 of the 66 available replicated externally. Mendelian randomization analysis revealed 7 proteins genetically associated with HF at nominal significance; 2 were separately associated with HFpEF, and another 2 with HFrEF. Seven of these 9 proteins (NPDC1 [neural proliferation differentiation and control protein 1], APOF [apolipoprotein F], LMAN2 [lectin, mannose-binding 2], ADIPOQ [adiponectin], CD14 [cluster of differentiation 14], ARHGAP1 [Rho GTPase-activating protein 1], C9 [complement 9]) showed new, possibly causal associations, although we did not detect evidence for colocalization. CONCLUSIONS: In this large-scale proteomic study involving 3 longitudinal cohorts of older adults, we identified and replicated 55 novel protein markers of HF or its subtypes, and 7 new, possibly causal proteins. These proteins may enhance risk prediction, improve understanding of pathobiology, and help prioritize targets for therapeutic development of these foremost disorders in elders.

Humans↗

Glycaemic burden disrupts innate immunity in TB by modulating CD206 expression and macrophage antimicrobial responses.

Tuberculosis (TB) and diabetes mellitus (DM) represent a growing dual global health burden, with chronic hyperglycaemia recognized as a major modifier of host immunity against Mycobacterium tuberculosis (Mtb). Macrophages, central to pathogen recognition, phagocytosis, antigen presentation, and intracellular killing, may be particularly vulnerable to diabetic metabolic dysregulation. This study evaluated phenotypic and functional macrophage alterations in individuals with pulmonary TB, type 2 DM, TB-DM comorbidity, and healthy controls. Surface receptor expression was analysed by multicolour flow cytometry, while phagocytosis and intracellular bacterial clearance were assessed using FITC-labelled Mtb assays and colony-forming unit enumeration. Hyperglycaemia was associated with reduced CD11b, MARCO, and TLR2 expression alongside upregulation of the mannose receptor CD206, which correlated positively with HbA1c levels, indicating a shift toward a permissive M2-like phenotype. Phagocytic uptake of Mtb was significantly impaired and inversely correlated with HbA1c. Antigen-presenting capacity was selectively compromised, with reduced CD80 and CD86 expression in DM and TB-DM groups, while HLA-DR remained unchanged. Intracellular Mtb killing was markedly diminished in diabetic macrophages. These findings demonstrate that chronic hyperglycaemia profoundly disrupts macrophage innate immunity, contributing to increased TB susceptibility and poor infection control in diabetic populations.

Humans↗

Receptor-mediated endocytosis of galactose and mannose exposing ligands: an electron microscopic study on adult and neonatal cultured rat hepatocytes.

We compared the receptor-mediated endocytosis for galactose and mannose exposing ligands in primary cultures of hepatocytes from newborn and adult rats. The endocytic pathway was revealed ultrastructurally using colloidal gold particles coupled to lactosylated bovine serum albumin and invertase. The binding activity on the cell surfaces is observed by keeping the cells at 4 degrees C. For both ligands used, the binding capacity for hepatocytes from adult rats was greater than for neonatal cultured cells. Increasing the temperature to 37 degrees C, we observed that the protein-gold complexes entered the intracellular endocytic organelles. Within 5-15 min, the marker was confined in vesicles close to the cell surface and in the endosome, while after 60 min, the marker is found in lysosome-like compartments. We found that the process of endocytosis is similar for galactose and mannose exposing ligands. The organelles involved in the process of endocytosis in newborn cultured hepatocytes are not different in shape from those of cultured cells of adult rats, but the process of internalization is slower.

Aging↗

The mannose receptor and other macrophage lectins.

The macrophage expresses a variety of cell surface lectins with activities that support specific functional roles and correspond to various differentiation states characteristic of this cell type. Recently, research has been carried out to investigate the mannose receptor, the advanced glycosylation end products receptor, the mannose-6-phosphate-receptor, the beta-glucan receptor, sialoadhesin and several galactose-specific binding proteins.

Animals↗

Heightened frequency of innate immunity risk alleles in south Indian diabetics with urinary tract infections.

Urinary Tract Infections are an emerging public health concern among individuals with diabetes mellitus, particularly in South Asia where high disease burden, genetic diversity and increasing drug resistance contribute to the progressive increase in burden. While metabolic and clinical risk factors are well studied, the role of host innate immune genetic variations in shaping UTI susceptibility among diabetics remains poorly understood. This case-control study evaluated functional polymorphisms in key innate immunity genes, TLR4 (rs4986790, rs4986791), MBL2 (rs1800450) and LTA (rs909253), in 70 T2D patients with UTI and 70 T2D patients without UTI. Genotyping was performed using 5'-hydrolysis probe assay. Across all the four SNPs, the risk allele consistently showed a higher frequency among T2D patients with UTI, indicating a directional trend suggestive of cumulative susceptibility. Also, a strong and significant protective association was observed for the LTA rs909253 'G' allele, which was less frequent in cases than controls. This low-inflammatory 'AA' genotype was also markedly enriched among rUTI cases compared to controls. Clinically, 34.3% of cases experienced rUTIs. This observed directional increase of risk alleles across all four innate immunity SNPs, along with the protective role of LTA rs909253 'G' allele, highlights cumulative host genetic modulation of UTI risk in T2D and supports translational use of genetic profiling in infection risk prediction.

Humans↗

A proteomics-based survey reveals thrombospondin-4 as a ligand regulated by the mannose receptor in the injured lung.

Receptor-mediated cellular uptake of specific ligands constitutes an important step in the dynamic regulation of individual protein levels in extracellular fluids. With a focus on the inflammatory lung, we here performed a proteomics-based search for novel ligands regulated by the mannose receptor (MR), a macrophage-expressed endocytic receptor. WT and MR-deficient mice were exposed to lipopolysaccharide, after which the protein content in their lung epithelial lining fluid was compared by tandem mass tag-based mass spectrometry. More than 1200 proteins were identified in the epithelial lining fluid using this unbiased approach, but only six showed a statistically different abundance. Among these, an unexpected potential new ligand, thrombospondin-4 (TSP-4), displayed a striking 17-fold increased abundance in the MR-deficient mice. Experiments using exogenous addition of TSP-4 to MR-transfected CHO cells or MR-positive alveolar macrophages confirmed that TSP-4 is a ligand for MR-dependent endocytosis. Similar studies revealed that the molecular interaction with TSP-4 depends on both the lectin activity and the fibronectin type-II domain of MR and that a closely related member of the TSP family, TSP-5, is also efficiently internalized by the receptor. This was unlike the other members of this protein family, including TSPs -1 and -2, which are ligands for a close MR homologue known as urokinase plasminogen activator receptor-associated protein. Our study shows that MR takes part in the regulation of TSP-4, an important inflammatory component in the injured lung, and that two closely related endocytic receptors, expressed on different cell types, undertake the selective endocytosis of distinct members of the TSP family.

Animals↗

Inducible flocculation in Komagataella phaffii enables enhanced biomass separation for biopharmaceutical production.

Biomass separation represents a critical bottleneck in Komagataella phaffii-based biopharmaceutical processes, as typically high cell densities of 40 - 50 % create significant operational, technical and economic challenges for harvest operations. Yeast cell aggregation (flocculation) provides a solution to accelerate cell sedimentation by increasing particle size, thus allowing to improve biomass-supernatant separation efficiency during both natural gravity settling and (continuous) centrifugation operations. This study demonstrates successful engineering of K. phaffii strains with an inducible flocculation phenotype using CRISPR/Cas9-based genome editing to integrate the Saccharomyces cerevisiae FLO1 (ScFLO1) gene under control of various regulatory elements, including methanol-inducible and derepressible promoters. Flocculation strength could be enhanced by implementing transcriptional positive feedback circuits based on the methanol-inducible AOX1 promoter. To address methanol-free production requirements, we developed alternative systems to retrofit PAOX1-based ScFLO1 expression and exploited the derepressible PDF promoter, offering broader compatibility with biopharmaceutical manufacturing facilities. Flocculating cells cultivated in a bioreactor demonstrated significantly improved sedimentation behavior, with considerably lower supernatant turbidity after short low-speed centrifugation or gravity sedimentation compared to non-flocculating controls. Crucially, cell flocculation had no negative impact on product amount and quality when expressing a multivalent NANOBODY® VHH molecule with pharmaceutical relevance. Thus, this work establishes the first genetically engineered flocculation system in K. phaffii compatible with recombinant protein production, providing the basis for an innovative approach to streamline harvest operations in biopharmaceutical processes.

Flocculation↗

Organization of the gene encoding the human macrophage mannose receptor (MRC1).

The gene for the human macrophage mannose receptor (MRC1) has been characterized by isolation of clones covering the entire coding region. Sequence analysis reveals that the gene is divided into 30 exons. The first three exons encode the signal sequence, the NH2-terminal cysteine-rich domain, and the fibronectin type II repeat, while the final exon encodes the transmembrane anchor and the cytoplasmic tail. The intervening 26 exons encode the eight carbohydrate-recognition domains and intervening spacer elements. However, no simple correlation between intron boundaries and functional carbohydrate-recognition domains is apparent. The pattern of intron positions as well as comparison of the sequences of the carbohydrate-recognition domains suggests that the duplication of these domains was an evolutionarily ancient event.

Amino Acid Sequence↗

Distinct and overlapping functions of allelic forms of human mannose binding protein.

Human mannose binding protein (MBP) is a C-type serum lectin involved in first-line host defense against a variety of bacterial, fungal and viral pathogens. Recently an association was found between low levels of serum MBP and an increased frequency of recurrent infections in infants. A particular genotype, in which glycine is substituted by aspartic acid at codon 54 of MBP in the fifth collagen repeat, shows apparent concordance with the clinical phenotype. We report, however, that this genotype occurs in 5% of the population and encodes a functional protein. Our results indicate that the Gly54Asp allele does not account for a deficiency state, but instead suggest that MBP may have two predominant allelic forms that have overlapping function and differ only in their ability to activate the classical pathway of complement.

Alleles↗

Characterization of the interaction both in vitro and in vivo of tissue-type plasminogen activator (t-PA) with rat liver cells. Effects of monoclonal antibodies to t-PA.

The interaction of 125I-labelled tissue-type plasminogen activator (125I-t-PA) with freshly isolated rat parenchymal and endothelial liver cells was studied. Binding experiments at 4 degrees C with parenchymal cells and endothelial liver cells indicated the presence of 68,000 and 44,000 high-affinity t-PA-binding sites, with an apparent Kd of 3.5 and 4 nM respectively. Association of 125I-t-PA with parenchymal cells was Ca(2+)-dependent and was not influenced by asialofetuin, a known ligand for the galactose receptor. Association of 125I-t-PA with liver endothelial cells was Ca(2+)-dependent and mannose-specific, since ovalbumin (a mannose-terminated glycoprotein) inhibited the cell association of t-PA. Association of 125I-t-PA with liver endothelial cells was inhibited by anti-(human mannose receptor) antiserum. Anti-(galactose receptor) IgG had no effect on 125I-t-PA association with either cell type. Degradation of 125I-t-PA at 37 degrees C by both cell types was inhibited by chloroquine or NH4Cl, indicating that t-PA is degraded lysosomally. in vitro experiments with three monoclonal antibodies (MAbs) demonstrated that anti-t-PA MAb 1-3-1 specifically decreased association of 125I-t-PA with the endothelial cells, and anti-t-PA Mab 7-8-4 inhibited association with the parenchymal cells. Results of competition experiments in rats in vivo with these antibodies were in agreement with findings in vitro. Both antibodies decreased the liver uptake of 125I-t-PA, while a combination of the two antibodies was even more effective in reducing the liver association of 125I-t-PA and increasing its plasma half-life. We conclude from these data that clearance of t-PA by the liver is regulated by at least two pathways, one on parenchymal cells (not galactose/mannose-mediated) and another on liver endothelial cells (mediated by a mannose receptor). Results with the MAbs imply that two distinct sites on the t-PA molecule are involved in binding to parenchymal cells and liver endothelial cells.

Animals↗

Mannose receptor (MRC1) mediates uptake of dextran by bone marrow-derived macrophages.

Macrophages survey their environment using receptor-mediated endocytosis and pinocytosis. Receptor-mediated endocytosis allows internalization of specific ligands, whereas pinocytosis nonselectively internalizes extracellular fluids and solutes. CRISPR/Cas9 whole-genome screens were used to identify genes regulating constitutive and growth factor-stimulated dextran uptake in murine bone marrow-derived macrophages (BMDM). The mannose receptor c-type 1 (MRC1/CD206) was a top hit in the screen. Targeted gene disruptions of Mrc1 reduced dextran uptake but had little effect on fluid-phase uptake of Lucifer yellow. Other screen hits also differentially affected the uptake of dextran and Lucifer yellow, indicating internalization by separate mechanisms. Visualization of dextran and Lucifer yellow uptake by microscopy showed enrichment of dextran in small puncta, which was inhibitable by mannan, a ligand of MRC1. In contrast, Lucifer yellow predominantly was internalized in larger macropinosomes. In addition, IL4-treated BMDMs internalized more dextran than untreated BMDM correlating with increased MRC1 expression. Therefore, dextran is not an effective marker for pinocytosis in BMDMs since it is internalized by receptor-mediated process. Numerous genes that regulate dextran internalization in primary murine macrophages were identified in the whole-genome screens, which can inform understanding of the regulation of MRC1 expression and MRC1-mediated uptake in macrophages.

Animals↗

High frequencies in African and non-African populations of independent mutations in the mannose binding protein gene.

We have previously identified, in three British families having an index child with frequent infections, a point mutation (GGC-->GAC) in codon 54 of exon 1 of the gene for the human lectin mannose binding protein (MBP). This was associated with low serum levels of this complement activating protein and would be anticipated to impair opsonization of mannose rich microorganisms. We now report a second point mutation (GGA-->GAA) in Gambians from West Africa, involving codon 57 of exon 1. By substituting carboxylic acids for axial glycines in the translated proteins both mutations would be expected to disrupt the secondary structure of the collagenous triple helix of the 96 kDa MBP subunits. In the Gambians the codon 57 mutation was studied by PCR, sequence analysis and restriction analysis and found to be remarkably common (frequency of the mutant gene 0.29 in adults and 0.23 in newborns) whereas the codon 54 mutation was very rare (frequency 0.003). However, the codon 54 mutation was frequent in both a British Caucasian and a Hong Kong Chinese population (frequency of the mutant gene 0.17 and 0.11 respectively). It was predicted that both homozygous and heterozygous individuals would have profoundly reduced serum levels of the protein and this was confirmed by immunoassay as was the reduced capacity of such sera to activate complement through the MBP initiated classical pathway. Our data indicate that the two mutations have arisen independently since the divergence of African and non African populations and both have attained high frequencies.

Adult↗