Lectins are proteins responsible for recognizing the signals of sugar molecules in the body. Sialic acid-binding immunoglobulin-like lectins (Siglecs) regulate the innate and adaptive immune responses in the tumor microenvironment by recognizing the glycan structure containing sialic acid and mediating downstream signals through immune receptor tyrosine inhibitory motifs. In recent years, a variety of tumor treatment strategies targeting the sialic acid-Siglecs axis have been introduced, including sialoglycoprotein-mediated drug delivery and antibody mediated inhibition of Siglecs from recognizing tumor surface ligands. In the future, by combining with glycoprotein nanotherapy, antibody therapy and gene therapy, Siglecs can be used to accurately locate tumor targets and release the anti-tumor immunity, so as to achieve the purpose of effective cure of tumors.
Sialic Acid Binding Immunoglobulin-like Lectins/metabolism* ; N-Acetylneuraminic Acid ; Immunoglobulins/metabolism* ; Receptors, Immunologic ; Ligands

Bacillus subtilis is recognized as a generally-regarded-as-safe strain, and has been widely used in the biosynthesis of high value-added products, including N-acetylneuraminic acid (NeuAc) which is widely used as a nutraceutical and a pharmaceutical intermediate. Biosensors responding to target products are widely used in dynamic regulation and high-throughput screening in metabolic engineering to improve the efficiency of biosynthesis. However, B. subtilis lacks biosensors that can efficiently respond to NeuAc. This study first tested and optimized the transport capacity of NeuAc transporters, and obtained a series of strains with different transport capacities for testing NeuAc-responsive biosensors. Subsequently, the binding site sequence of Bbr_NanR responding to NeuAc was inserted into different sites of the constitutive promoter of B. subtilis, and active hybrid promoters were obtained. Next, by introducing and optimizing the expression of Bbr_NanR in B. subtilis with NeuAc transport capacity, we obtained an NeuAc-responsive biosensor with wide dynamic range and higher activation fold. Among them, P535-N2 can sensitively respond to changes in intracellular NeuAc concentration, with the largest dynamic range (180-20 245) AU/OD. P566-N2 shows a 122-fold of activation, which is 2 times of the reported NeuAc-responsive biosensor in B. subtilis. The NeuAc-responsive biosensor developed in this study can be used to screen enzyme mutants and B. subtilis strains with high NeuAc production efficiency, providing an efficient and sensitive analysis and regulation tool for biosynthesis of NeuAc in B. subtilis.
N-Acetylneuraminic Acid/metabolism* ; Bacillus subtilis/metabolism* ; Promoter Regions, Genetic/genetics* ; Binding Sites ; Biosensing Techniques

OBJECTIVETo explore the changes of methylenedioxyamphetamine (MDA), total antioxidants content (TAC) and sialic acid (SA) from the unilateral epididymis of experimental varicocele in adolescent rats, and to illuminate the effects of varicocele on unilateral epididymis epithelium.

METHODSExperimental left varicocele model of 16 adult male Sprague-Dawley rats were established by partial ligation of left renal vein. The epididymis were collected for detecting the content of MDA, TAC and SA by using spectrophotometry.

RESULTSThere was statistically significant differences in the contents of three substances between experimental varicocele and sham-operated groups.

CONCLUSIONThe content of MDA, TAC and SA will change and the sialic acid-secreting-function of unilateral epididymis will be injured because of varicocele.

Animals ; Antioxidants ; metabolism ; Epididymis ; metabolism ; Male ; N-Acetylneuraminic Acid ; metabolism ; N-Methyl-3,4-methylenedioxyamphetamine ; metabolism ; Rats ; Rats, Sprague-Dawley ; Varicocele ; metabolism

OBJECTIVETo investigate the change and implication of epididymis sialic acid after 24 hours following 2- or 4-hour torsing/detorsing of testes in rats.

METHODSTwenty-four adult male Sprague-Dawley rats were subjected to unilateral 720 degrees testicular torsion for 2 and 4 hours and then repaired. The ischemic epididymides were collected for detecting the content of sialic acid by spectrophotometry.

RESULTSThere was no statistically significant difference between the content of epididymis sialic acid after 24 hours following 2-hour torsing/detorsing of testes and that of the sham group, while significant difference was found between the content of epididymis sialic acid after 24 hours following 4-hours torsing/detorsing of testes and that of sham group.

CONCLUSIONSSialic acidsecreting-function of epididymis can remain normal after one day following 2-hour torsing/detorsing of testes, and be injured after one day following 4-hour torsing/detorsing of testes. The epididymis remains resistant to ischemic damage during testicular ischemia.

Animals ; Epididymis ; chemistry ; Male ; N-Acetylneuraminic Acid ; analysis ; Rats ; Rats, Sprague-Dawley ; Spermatic Cord Torsion ; metabolism ; Time Factors

Immunoglobulin (IgG) glycosylation affects the effector functions of IgG in a myriad of biological processes and has been closely associated with numerous autoimmune diseases, including systemic lupus erythematosus (SLE), thus underlining the pathogenic role of glycosylation aberration in autoimmunity. This study aims to explore the relationship between IgG sialylation patterns and lupus pregnancy. Relative to that in serum samples from the control cohort, IgG sialylation level was aberrantly downregulated in serum samples from the SLE cohort at four stages (from preconception to the third trimester of pregnancy) and was significantly associated with lupus activity and fetal loss during lupus pregnancy. The type I interferon signature of pregnant patients with SLE was negatively correlated with the level of IgG sialylation. The lack of sialylation dampened the ability of IgG to suppress the functions of plasmacytoid dendritic cells (pDCs). RNA-seq analysis further revealed that the expression of genes associated with the spleen tyrosine kinase (SYK) signaling pathway significantly differed between IgG- and deSia-IgG-treated pDCs. This finding was confirmed by the attenuation of the ability to phosphorylate SYK and BLNK in deSia-IgG. Finally, the coculture of pDCs isolated from pregnant patients with SLE with IgG/deSia-IgG demonstrated the sialylation-dependent anti-inflammatory function of IgG. Our findings suggested that IgG influences lupus activity through regulating pDCs function via the modulation of the SYK pathway in a sialic acid-dependent manner.
Humans ; Pregnancy ; Female ; Lupus Erythematosus, Systemic/pathology* ; Signal Transduction ; N-Acetylneuraminic Acid/metabolism* ; Immunoglobulin G ; Dendritic Cells/pathology*

OBJECTIVETo study the relationships of experimental varicocele to the apoptosis of epididymis epithelium and changes of the contents of alpha-1,4-glucosidase and sialic acid from the unilateral epididymis in adolescent rats, and to investigate the effects of varicocele on the unilateral epididymis epithelium.

METHODSExperimental left varicocele models of 16 adult male Sprague-Dawley rats were obtained by partial ligation of the left renal vein. The epididymides were collected for detecting the apoptosis of epididymis epithelium and the contents of alpha-1,4-glucosidase and sialic acid by using spectrophotometry.

RESULTSSeven days after the establishment of the left varicocele model, the index of the apoptosis of the left epididymis epithelium was significantly higher (P < 0.001) and the contents of alpha-1,4-glucosidase and sialic acid significantly lower (P < 0.05, P < 0.005) in the experimental group than in the control.

CONCLUSIONThe results suggest that unilateral varicocele may increase the apoptosis of epididymis epithelium and the contents of alpha-1,4-glucosidase and sialic acid and subsequently affect the synthesizing and secretory function of the epididymis.

Animals ; Apoptosis ; Epididymis ; pathology ; Epithelium ; pathology ; Male ; N-Acetylneuraminic Acid ; metabolism ; Rats ; Rats, Sprague-Dawley ; Varicocele ; metabolism ; pathology ; alpha-Glucosidases ; metabolism

In comparison with its counterpart from N. meningitides, all conserved motifs were found in the N-termini of E. coli CMP-NeuAc synthetase. E. coli CMP-NeuAc synthetase seems to have redundant C-termini with a less effect on its activity. To explain this speculation, a series of recombinant DNAs with deletion from 3'-end of CMP-NeuAc synthetase were produced by PCR, ligated into expression vector pET-15b and expressed in BL21(DE3)pLysS. After induction with IPTG, we found that the recombinant enzyme with deletion of 189 amino acids from C0termini retained its activity. This result demonstrates that the 229 amino acids of N-termini was the minimal functional domain of E. coli CMP-NeuAc synthetase. The deletions altered the optimum pH and thermostability of active truncated enzymes, indicating that the truncated C-terminal amino acids of E. coli CMP-NeuAc synthetase could affect the conformation of the enzymatic catalytic domain and therefore affect its catalytic activity and thermostability, although it is not involved in enzymatic activity directly.
Amino Acid Sequence ; Cytidine Monophosphate N-Acetylneuraminic Acid ; metabolism ; Enzyme Stability ; Escherichia coli ; enzymology ; Hydrogen-Ion Concentration ; Molecular Sequence Data ; Mutation ; N-Acylneuraminate Cytidylyltransferase ; chemistry ; physiology ; Structure-Activity Relationship

OBJECTIVETo investigate the effects of icariin on the streptozocin (STZ)-induced epididymis impair in rats.

METHODSThe epididymis impair was induced by injection of streptozocin at dosage of 60 mg/kg ip in SD rats. Animals were randomly divided into six groups (n = 14): normal control, model group, three icariin treated group with different dosages (P.O, 20 mg/kg, 40 mg/kg, 80 mg/kg especially) and rosiglitazone group (P.O, 3 mg/kg), 12 weeks later, animals were sacrificed. The level of serum glucose, the activity of lactate dehydrogenase (LDH), acid phosphatase (ACP), gamma-glutamyltranspeptidase (gamma-GT), alpha-glucosidase activity as well as sialic acid (SA), fructose level in the epididymis were determined. The pathological examination was performed under microscope after the epididymis was fixed by 4% poly-formalin and stained by HE.

RESULTSCompared with the normal control, the activity of LDH, ACP, gamma-GT and alpha-glucosidase in the epididymis revealed a decline, with lower level of SA and fructose. Histological examination showed that mature spermatocytes in the epididymis markedly decreased. These alterations were ameliorated in the groups with the treatment of icariin at 40 mg/kg and 80 mg/kg, but not at 20 mg/kg.

CONCLUSIONIcariin ameliorated the signs of epididymis in diabetic rats induced by streptozocin, this effect might carry out by promoting the elevation of special enzyme and energy metabolism in the epididymis.

Acid Phosphatase ; metabolism ; Animals ; Blood Glucose ; Diabetes Mellitus, Experimental ; physiopathology ; Epididymis ; drug effects ; enzymology ; physiopathology ; Flavonoids ; pharmacology ; Fructose ; metabolism ; L-Lactate Dehydrogenase ; metabolism ; Male ; N-Acetylneuraminic Acid ; metabolism ; Rats ; Rats, Sprague-Dawley ; alpha-Glucosidases ; metabolism ; gamma-Glutamyltransferase ; metabolism

OBJECTIVETo investigate the effect of cell surface sialic acid and its linkage on the cell-cell and cell-matrix adhesion of mammary carcinoma cells MD-MB-435.

METHODSMD-MB-435 cells were sense-transfected with ST6Gal I cDNA or antisense-transfected with part of the ST6Gal I sequence inserted in pcDNA 3.1 vector, with mock transfection with pcDNA3.1 vector as the control. The cell surface alpha2, 6-linked sialylation was determined by fluorescence-activated cell sorting (FACS) using lectin SNA (Sambucus nigra agglutinin specific to alpha2, 6-linked sialic acid on N-linked glycoprotein). A significantly increased alpha2, 6-sialylation subclone in sense-transfectants and a decreased alpha2, 6-sialylation subclone in antisense-transfectants were selected for further examination of cell-cell and cell-matrix (collagen IV) adhesion. The transfectants were also treated with sialidase to compare the capacity of cell adhesion affected by cell surface sialylation.

RESULTSSense-transfection subclone showed a reduced cell-cell aggregation but enhanced cell-matrix adhesion. In contrast, the antisense-transfection subclone exhibited increased cell-cell aggregation and decreased cell-matrix adhesion. After treatment with sialidase, the cell-matrix adhesion of all the transfectants and the parental MDA-MB-435 cells were significantly reduced to the level of 31%-57% of untreated cells.

CONCLUSIONCell surface sialic acid and alpha2, 6-linked sialylation play an important role in cell-cell and cell-matrix adhesion of mammary carcinoma cell MDA-MB-435.

Antigens, CD ; genetics ; metabolism ; Breast Neoplasms ; genetics ; metabolism ; pathology ; Cell Adhesion ; Cell Line, Tumor ; Cell Membrane ; metabolism ; Cell-Matrix Junctions ; metabolism ; Collagen Type IV ; metabolism ; Extracellular Matrix ; metabolism ; Humans ; N-Acetylneuraminic Acid ; metabolism ; Sialyltransferases ; genetics ; metabolism ; Transfection

To investigate the N-glycosylation characteristics of recombinant human erythropoietin (rhEPO) produced by an industrial Chinese hamster ovary (CHO) cell line that is currently used in a large scale manufacturing process, we cultured this cell strain in static mode. The produced rhEPO in the culture supernatant was analyzed using isoelectric focusing (IEF) and Ricinus communis agglutinin-I (RCA-I) lectin precipitation. The lactate dehydrogenase (LDH) and sialidase activity in the serum-free supernatant were assayed as well. The analyses revealed that this cell strain could produce rhEPO with high sialic acid content, but during prolonged culture, cell viability decreased with time whilst the activity of sialidase present in the supernatant increased. The loss in rhEPO quality was due to a decrease in terminal sialic acid on the N-glycans, caused by sialidase degradation. The methods and findings in this paper serve as basis for further investigation of industrial production process.
Animals ; CHO Cells ; metabolism ; Cell Culture Techniques ; methods ; Cricetinae ; Cricetulus ; Erythropoietin ; biosynthesis ; genetics ; metabolism ; Genetic Engineering ; Humans ; N-Acetylneuraminic Acid ; metabolism ; Neuraminidase ; metabolism ; Proteolysis ; Recombinant Proteins ; biosynthesis ; genetics ; metabolism