35B5 antibody potently neutralizes SARS-CoV-2 Omicron by disrupting the N-glycan switch via a conserved spike epitope

1. Download : Download high-res image (302KB)
2. Download : Download full-size image

     

Streptococcal immunoglobulin-binding protein Sib35 exerts stimulatory and mitogenic effects toward mouse B lymphocytes

Group A Streptococcus (GAS) produces several immunopotent proteins such as the immunoglobulin-binding protein 35 (Sib35) family, known to be an immunoglobulin G-degrading enzyme of GAS and a CD16-binding protein of GAS, Mac-1-like protein/IdeS. In this study, Sib35 activated mouse B cells and induced the proliferation of B lymphocytes, while it also bound directly to B cells, which enhanced the expression of MHC class II and B7-2. Furthermore, Sib35 induced the differentiation of B cells to immunoglobulin-producing plasma cells and B cell line proliferation. These results suggest that Sib35 functions as a streptococcal mitogen of mouse B cells.     

Hypoxia enhances stimulating effect of amyloid beta peptide (25–35) for interleukin 17 and T helper lymphocyte subtype 17 upregulation in cultured peripheral blood mononuclear cells

Th17 has been demonstrated to have a key role in several autoimmune diseases. The present study was carried out to investigate changes in IL-17 and Th17 in cultured PBMC in response to Abeta peptide (25–35) and hypoxic stimulation in vitro . PBMC were collected from adult healthy donors and cultured in normal and anaerobic conditions (hypoxia 1, 3, 6, 12, 24 hr). Each group of cells was stimulated with Abeta peptide (25–35; 3, 10 nmol/ml). ELISA was used to examine IL-17A concentrations in the supernatants, and flow cytometry for the numbers of IL-17A secreting CD4 positive Th17 lymphocytes. Statistically significant increases in IL-17A and Th17 concentrations were found in groups with 10 nmol/ml Abeta (25–35) and more than three hr anaerobic culture. IL-17A and Th17 concentrations in anaerobic groups increased gradually with time and peaked at six hr. Compared with other groups, the highest concentrations were found in those treated with 10 nmol/ml Abeta and cultured for six hr ( P < 0.001). This study provides the first report that IL-17A and Th17 lymphocytes are possibly involved in the immune pathogenesis caused by Abeta peptide (25–35). Hypoxia may enhance this response independently of time.     

Modulation of efficiency of translation termination in Saccharomyces cerevisiae

Nonsense suppression is a readthrough of premature termination codons. It typically occurs either due to the recognition of stop codons by tRNAs with mutant anticodons, or due to a decrease in the fidelity of translation termination. In the latter case, suppressors usually promote the readthrough of different types of nonsense codons and are thus called omnipotent nonsense suppressors. Omnipotent nonsense suppressors were identified in yeast Saccharomyces cerevisiae in 1960s, and most of subsequent studies were performed in this model organism. Initially, omnipotent suppressors were localized by genetic analysis to different protein- and RNA-encoding genes, mostly the components of translational machinery. Later, nonsense suppression was found to be caused not only by genomic mutations, but also by epigenetic elements, prions. Prions are self-perpetuating protein conformations usually manifested by infectious protein aggregates. Modulation of translational accuracy by prions reflects changes in the activity of their structural proteins involved in different aspects of protein synthesis. Overall, nonsense suppression can be seen as a “phenotypic mirror” of events affecting the accuracy of the translational machine. However, the range of proteins participating in the modulation of translation termination fidelity is not fully elucidated. Recently, the list has been expanded significantly by findings that revealed a number of weak genetic and epigenetic nonsense suppressors, the effect of which can be detected only in specific genetic backgrounds. This review summarizes the data on the nonsense suppressors decreasing the fidelity of translation termination in S. cerevisiae, and discusses the functional significance of the modulation of translational accuracy.     

A Cdk5–p35 Stable Complex Is Involved in the β-Amyloid-Induced Deregulation of Cdk5 Activity in Hippocampal Neurons

The cdk5 and its activator p35 constitute one of the main tau-phosphorylating systems in neuronal cells. Under normal conditions for neurons, its activity is required for modulating tau involvement in neuronal polarity and in development of the mammalian central nervous system. Recently, we reported that the treatment of rat hippocampal cells in culture with fibrillary β-amyloid (Aβ) results in deregulation of the protein kinase cdk5. The neurotoxic effects of Aβ fibrils were prevented by inhibition of cdk5 activity by butyrolactone I or by using antisense oligonucleotides that control the expression of this kinase. Here, we show that the Aβ-promoted increase of cdk5 activity is associated with changes in tau phosphorylation patterns and in the intraneuronal distribution of tau. In addition to hippocampal cells, deregulation of cdk5 was observed in other cell types. However, butyrolactone I prevented Aβ-induced cell death only in neuronal cells in which cdk5 activation was sensitive to Aβ fibrils. This lost of cdk5 regulation in hippocampal cells exposed to Aβ fibrils appears to be associated with an increase in the cdk5–p35 complex stability. Complex stabilization was sensitive to phosphorylation of cdk5. However, no changes in cdk5 and p35 mRNAs were observed, suggesting that the main effects on cdk5 occur at the posttranslational level. These studies indicate that cdk5 phosphorylation and the formation of an abnormally active cdk5–p35 complex are directly involved in the molecular paths leading to the neurodegenerative process of rat hippocampal neurons triggered by Aβ fibrils.     

A Sensitive and Reliable Assay for Dopamine (β-Hydroxylase in Tissue

A new assay procedure for dopamine β-hydroxylase (DBH) in tissue extracts is described. Solubilized DBH was adsorbed from crude extracts on Concanavalin A-Sepharose (Con A-Sepharose), resulting in enrichment of the enzyme as well as removal of endogenous catecholamines and inhibitory substances. The enzymatic assay was carried out with DBH still adsorbed to Con A-Sepharose. The adsorption of the DBH to Con A-Sepharose offers three advantages over previous assay procedures. (1) Because of removal of the endogenous inhibitory substances, a single Cu²⁺ concentration can be used for the determination of DBH activity, regardless of the tissue dilution or inhibitor content of the analysed sample. Using this procedure, the optimal Cu²⁺ concentration for DBH of bovine adrenal gland extracts was 3 μM and for rat brain 10 μM. (2) Because of removal of endogenous catecholamines, dopamine, the main physiological substrate of DBH in noradrenergic neurons, can be used for the assay. The enzymatic reaction product, noradrenaline, was determined by high performance liquid chromatography and electrochemical detection (hplc-ec). This procedure resulted in an approx. 10-fold increase in sensitivity of the assay compared with other procedures, e.g., the radioenzymatic assay. (3) Direct determination of the immediate product of the enzymatic reaction (noradrenaline) permits kinetic analysis. It was found that the Michaelis constants for the substrate (dopamine) and co-factor (ascorbic acid) (2 mM and 0.65 mM, respectively) determined in bovine adrenal tissue extracts by the described procedure were identical with the values for the purified DBH preparation.     

Assembly of an antibody and its derived antibody fragment inNicotiana andArabidopsis

The yield and assembly of an IgG1 antibody and its derived F_ab fragment were compared inNicotiana andArabidopsis. The results obtained showed a lot of interclonal variability. For 45% of the primary transgenic calluses, antigen-binding entities represented less than 0.1% of the total soluble protein (TSP). Only two of the 103 analysed transformants contained more than 1% of antigen-binding protein, with 1.26% being the highest yield. Analogous amounts of complete antibody and F_ab accumulated in primary callus tissue. Moreover, yields were in the same range for both species as far as primary callus tissue is concerned. However, the accumulation of the F_ab fragment in leaf tissue of regenerated plants differed significantly betweenNicotiana andArabidopsis. The F_ab fragment accumulated to only 0.044% of TSP inNicotiana leaves but up to 1.3% inArabidopsis leaves. Furthermore, both species showed differences in the assembly pattern of the complete antibody. WhereasArabidopsis contained primarily fully assembled antibodies of 150 kDa,Nicotiana showed an abundance of fragments in the 50 kDa range.     

Targeting cellular apoptotic pathway with peptides from marine organisms

Apoptosis is a critical defense mechanism against the formation and progression of cancer and exhibits distinct morphological and biochemical traits. Targeting apoptotic pathways becomes an intriguing strategy for the development of chemotherapeutic agents. Peptides from marine organisms have become important sources in the discovery of antitumor drugs, especially when modern technology makes it more and more feasible to collect organisms from seas. This primer summarizes several marine peptides, based on their effects on apoptotic signaling pathways, although most of these peptides have not yet been studied in depth for their mechanisms of action. Novel peptides that induce an apoptosis signal pathway are presented in association with their pharmacological properties.