Checkpoint kinase 2 controls insulin secretion and glucose homeostasis.

After the discovery of insulin, a century ago, extensive work has been done to unravel the molecular network regulating insulin secretion. Here we performed a chemical screen and identified AZD7762, a compound that potentiates glucose-stimulated insulin secretion (GSIS) of a human ß cell line, healthy and type 2 diabetic (T2D) human islets and primary cynomolgus macaque islets. In vivo studies in diabetic mouse models and cynomolgus macaques demonstrated that AZD7762 enhances GSIS and improves glucose tolerance. Furthermore, genetic manipulation confirmed that ablation of CHEK2 in human ß cells results in increased insulin secretion. Consistently, high-fat-diet-fed Chk2-/- mice show elevated insulin secretion and improved glucose clearance. Finally, untargeted metabolic profiling demonstrated the key role of the CHEK2-PP2A-PLK1-G6PD-PPP pathway in insulin secretion. This study successfully identifies a previously unknown insulin secretion regulating pathway that is conserved across rodents, cynomolgus macaques and human ß cells in both healthy and T2D conditions.

A novel approach to achieving more efficient production of the mature form of human IL-37 in plants.

Interleukin-37 is a newly discovered cytokine that plays a pivotal role in suppressing innate inflammation and acquired immunity. We have recently expressed both the mature(mat-) and pro-forms of human IL-37b in plants and demonstrated that while both forms of the plant-made hIL-37b are functional, pmat-hIL37b exhibited significantly greater activity than ppro-IL-37b. Compared to ppro-hIL-37b, on the other hand, the expression level of pmat-hIL-37b was substantially lower (100.5 µg versus 1.05 µg/g fresh leaf mass or 1% versus 0.01% TSP). Since the difference between ppro-hIL-37b and pmat-hIL-37b is that ppro-hIL-37b contains a signal sequence not cleavable by plant cells, we reasoned that this signal sequence would play a key role in stabilizing the ppro-hIL-37b protein. Here, we describe a novel approach to enhancing pmat-hIL-37b production in plants based on incorporation of a gene sequence encoding tobacco etch virus (TEV) protease between the signal peptide and the mature hIL-37b, including a TEV cleavage site at the C-termini of TEV protease. The rationale is that when expressed as a sp-TEV-matIL-37b fusion protein, the stabilizing properties of the signal peptide of pro-hIL-37b will be awarded to its fusion partners, resulting in increased yield of target proteins. The fusion protein is then expected to cleave itself in vivo to yield a mature pmat-hIL-37b. Indeed, when a sp-TEV-matIL-37b fusion gene was expressed in stable-transformed plants, a prominent band corresponding to dimeric pmat-hIL-37b was detected, with expression yields reaching 42.5 µg/g fresh leaf mass in the best expression lines. Bioassays demonstrated that plant-made mature pmat-hIL-37b is functional.

Formation of hydroperoxo (-OOH) species on the surface of self-doped Bi2.15WO6: reactivity towards As(iii) oxidation.

Bi2+xWO6 is a cost-effective and environmentally friendly photocatalyst that shows high reactivity in the oxidation of various contaminants under visible light. However, under alkaline conditions, the reactive oxidative species in the Bi2+xWO6 system are still not clear yet. In this study, it is observed that the oxidation rates of As(iii) increase with increasing pH values in the Bi2.15WO6 system. Photoluminescence and the Mott-Schottky analyses confirm that OH- promotes the separation and transfer of photogenerated electron-hole pairs over Bi2.15WO6, thus facilitating the oxidation of As(iii). Electron spin resonance spectra analysis and quenching experiments rule out contributions of •OH, O2˙-, 1O2 and superoxo species to As(iii) oxidation and indicate that surface -OOH and/or H2O2 are indeed the predominant species under alkaline conditions. The improved production of H2O2 by H-donors such as glucose and phenol, as well as the UV-vis diffuse reflectance and Raman analyses, further confirms the formation of surface -OOH on Bi2.15WO6 under alkaline conditions. In the dark, the significant higher oxidation rate of As(iii) by H2O2-Bi2.15WO6 than that by H2O2 alone reveals that surface -OOH, instead of H2O2, plays an important role in As(iii) oxidation. This study enriches our understanding of the diversity of reactive oxygen species (ROS) in the Bi2.15WO6 system and gives new insight into the mechanism involved in the oxidation of As(iii) under alkaline conditions.

Formation and Oxidation Reactivity of MnO2+(HCO3-)n in the MnII(HCO3-)-H2O2 System.

The MnII(HCO3-)-H2O2 (MnII-BAP) system shows high reactivity toward oxidation of electron-rich organic substrates; however, the predominant oxidizing species and its formation pathways involved in the MnII-BAP system are still under debate. In this study, we used the MnII-BAP system to oxidize As(III) in that As(III), Mn2+, and HCO3- are common components in As(III)-contaminated groundwater. Kinetic results show that MnII(HCO3-)n [including MnII(HCO3)+ and MnII(HCO3)2] is a key factor in the MnII-BAP system to oxidize As(III). Quenching experiments rule out contributions of OH• and 1O2 to As(III) oxidation and reveal that O2•- and the oxidizing species generated from O2•- play predominant roles in the oxidation of As(III). We further reveal that the MnO2+(HCO3-)n intermediate generated in the reaction between MnII(HCO3-)n and O2•-, instead of O2•-, is the predominant oxidizing species. Although CO3•- also contributes to As(III) oxidation, the high reaction rate constant between CO3•- and O2•- indicates that CO3•- is not the predominant oxidizing species in the As(III)-MnII-BAP system. In addition, the presence of Mn(III) further indicates the important Mn(II)-Mn(III) cycling in the MnII-BAP system. We therefore suggest two important roles of MnII(HCO3-)n in the MnII-BAP system: (i) MnII(HCO3-)n reacts with H2O2 to form the MnIII(HCO3)3 intermediate, followed by a subsequent reaction between MnIII(HCO3)3 and H2O2 to produce O2•-; (ii) MnII(HCO3-)n can also stabilize O2•- with the formation of MnO2+(HCO3-)n. MnO2+(HCO3-)n is an electrophilic reagent and plays the predominant role in the oxidation of As(III) to As(V).