Production of Recombinant β-Hexosaminidase A, a Potential Enzyme for Replacement Therapy for Tay-Sachs and Sandhoff Diseases, in the Methylotrophic Yeast Ogataea minuta

Human β-hexosaminidase A (HexA) is a heterodimeric glycoprotein composed of α- and β-subunits that degrades GM2 gangliosides in lysosomes. GM2 gangliosidosis is a lysosomal storage disease in which an inherited deficiency of HexA causes the accumulation of GM2 gangliosides. In order to prepare a large amount of HexA for a treatment based on enzyme replacement therapy (ERT), recombinant HexA was produced in the methylotrophic yeast Ogataea minuta instead of in mammalian cells, which are commonly used to produce recombinant enzymes for ERT. The problem of antigenicity due to differences in N-glycan structures between mammalian and yeast glycoproteins was potentially resolved by using α-1,6-mannosyltransferase-deficient (och1Δ) yeast as the host. Genes encoding the α- and β-subunits of HexA were integrated into the yeast cell, and the heterodimer was expressed together with its isozymes HexS (αα) and HexB (ββ). A total of 57 mg of β-hexosaminidase isozymes, of which 13 mg was HexA (αβ), was produced per liter of medium. HexA was purified with immobilized metal affinity column for the His tag attached to the β-subunit. The purified HexA was treated with α-mannosidase to expose mannose-6-phosphate (M6P) residues on the N-glycans. The specific activities of HexA and M6P-exposed HexA (M6PHexA) for the artificial substrate 4MU-GlcNAc were 1.2 ± 0.1 and 1.7 ± 0.3 mmol/h/mg, respectively. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern suggested a C-terminal truncation in the β-subunit of the recombinant protein. M6PHexA was incorporated dose dependently into GM2 gangliosidosis patient-derived fibroblasts via M6P receptors on the cell surface, and degradation of accumulated GM2 ganglioside was observed.     

Effect of environmental conditions on the α-glucosidase inhibitory activity of mulberry leaves

Mulberry leaves have been used as the sole food for silkworms in sericulture, and also as a traditional medicine for diabetes prevention. Mulberry leaf components, for example 1-deoxynojirimycin (1-DNJ), inhibit the activity of α-glucosidase and prevent increased blood glucose levels, and they are highly toxic to caterpillars other than silkworms. The α-glucosidase inhibitory activity of mulberry leaves changes with the season, but it is unknown which environmental conditions influence the α-glucosidase inhibitory activity. We investigated in this study the relationship between the α-glucosidase inhibitory activity and environmental conditions of temperature and photoperiod. The results demonstrate that low temperatures induced decreasing α-glucosidase inhibitory activity, while the induction of newly grown shoots by the scission of branches induced increasing α-glucosidase inhibitory activity. These results suggest that the α-glucosidase inhibitory activity was related to the defense mechanism of mulberry plants against insect herbivores.     

Characterization of Mesorhizobium loti L-rhamnose isomerase and its application to L-talose production

The L-rhamnose isomerase gene (rhi) of Mesorhizobium loti was cloned and expressed in Escherichia coli, and then characterized. The enzyme exhibited activity with respect to various aldoses, including D-allose and L-talose. Application of it in L-talose production from galactitol was achieved by a two-step reaction, indicating that it can be utilized in the large-scale production of L-talose.     

JAK2 is an important signal transducer in IL-33-induced NF-κB activation

IL-33, a member of the IL-1 family of cytokines, has been shown to activate NF-κB and MAP kinase family through the IL-1 receptor-related protein, ST2L. In this study, we found that IL-33 rapidly activated a tyrosine kinase, JAK2. Interestingly, we demonstrated the functional involvement of JAK2 in IL-33-induced IκBα degradation and NF-κB activation, since a JAK2 inhibitor, AG490, effectively inhibited this signaling pathway. Furthermore, IL-33 failed to induce IκBα degradation and NF-κB activation in JAK2-deficient MEFs expressing ST2L, compared with wild-type MEFs expressing ST2L. In addition, the introduction of wild-type JAK2 but not kinase dead JAK2 mutant (K882R) restored the IL-33-induced efficient activation of NF-κB in JAK2-deficient MEFs expressing ST2L, resulting in the induction of IL-6, CCL2/MCP-1 and CXCL1/KC expression. On the other hand, the activation of ERK, JNK and p38 was unaffected by JAK2 inhibition and JAK2 deficiency. Thus, these data demonstrate that JAK2 plays an important role in regulating IL-33-induced NF-κB activation.     

αvβ3-Integrin-targeting lanthanide complex: synthesis and evaluation as a tumor-homing luminescent probe

The application of lanthanide complexes in the time-resolved fluorescence imaging of living cells has emerged in the last few decades, providing high-contrast images of cells through detection of the delayed emission. In the present study, we synthesized novel trivalent lanthanide complexes containing the cyclic peptide c(RGDfK) to visualize the α_vβ₃-integrin-expressing tumor cells. Conjugation of c(RGDfK) with the macrocyclic bipyridine ligand had little effect on the fluorescence properties of the complex, indicating that the coordinated lanthanide ion was well isolated from the peptide. Bright luminescence images of α_vβ₃-integrin-expressing U87-MG cells were successfully obtained by employing the probes.     

IL-27-producing CD14(+) cells infiltrate inflamed joints of rheumatoid arthritis and regulate inflammation and chemotactic migration

Interleukin (IL)-27, a heterodimeric cytokine, has been reported to be involved in the pathogenesis of autoimmune diseases through mediating differentiation of Th1 or Th17 cells and immune cell activity or survival. However, the origin and effects of IL-27 in joints of rheumatoid arthritis (RA) remain unclear. In this study, we investigated the distribution and anti-inflammatory roles of IL-27 in RA synovium. The IL-27 levels in plasma of RA patients, osteoarthritis (OA) patients, or healthy volunteers (n=15 per group) were equivalent and were at most 1 ng/ml, but the IL-27 level in synovial fluid of RA patients (n=15, mean 0.13 ng/ml; range 0.017-0.37 ng/ml) was significantly higher than that in synovial fluid of OA patients (n=15, mean 0.003 ng/ml; range 0-0.033 ng/ml) and potentially lower than in plasma. We analyzed the protein level of IL-27 produced by RA fibroblast-like synoviocytes (FLSs) or mononuclear cells (MNCs) from RA or OA synovial fluid or peripheral blood and showed that IL-27 in RA joints was derived from MNCs but not from FLSs. We also found by flow cytometry that IL-27-producing MNCs were CD14(+), and that these CD14(+)IL-27(+) cells were clearly detected in RA synovium but rarely in OA synovium by immunohistochemistry. Furthermore, we demonstrated that a relatively physiological concentration of IL-27 below 10 ng/ml suppressed the production of IL-6 and CCL20 from RA FLSs induced by proinflammatory cytokines through the IL-27/IL-27R axis. In the synovial fluid of RA, the IL-27 level interestingly had positive correlation with the IFN-γ level (r=0.56, p=0.03), but weak negative correlation with the IL-17A level (r=-0.30, p=0.27), implying that IL-27 in inflammatory joints of RA induces Th1 differentiation and suppresses the development or the migration of Th17 cells. These findings indicate that circulating IL-27-producing CD14(+) cells significantly infiltrate into inflamed regions such as RA synovium and have anti-inflammatory effects in several ways: both directly through the reduction of IL-6 production, and possibly through the induction of Th1 development and the suppression of Th17 development; and indirectly by regulation of recruitment of CCR6(+) cells, such as Th17 cells, through the suppression of CCL20 production. Our results suggest that such a serial negative feedback system could be applied to RA therapy.     

Separating the wheat from the chaff: a prioritisation pipeline for the analysis of metabolomics datasets

Liquid Chromatography Mass Spectrometry (LC-MS) is a powerful and widely applied method for the study of biological systems, biomarker discovery and pharmacological interventions. LC-MS measurements are, however, significantly complicated by several technical challenges, including: (1) ionisation suppression/enhancement, disturbing the correct quantification of analytes, and (2) the detection of large amounts of separate derivative ions, increasing the complexity of the spectra, but not their information content. Here we introduce an experimental and analytical strategy that leads to robust metabolome profiles in the face of these challenges. Our method is based on rigorous filtering of the measured signals based on a series of sample dilutions. Such data sets have the additional characteristic that they allow a more robust assessment of detection signal quality for each metabolite. Using our method, almost 80% of the recorded signals can be discarded as uninformative, while important information is retained. As a consequence, we obtain a broader understanding of the information content of our analyses and a better assessment of the metabolites detected in the analyzed data sets. We illustrate the applicability of this method using standard mixtures, as well as cell extracts from bacterial samples. It is evident that this method can be applied in many types of LC-MS analyses and more specifically in untargeted metabolomics.