Optimized application of the secreted Nano-luciferase reporter system using an affinity purification strategy.

Secreted Nano-luciferase (secNluc) is a newly engineered secreted luciferase that possesses advantages of high structural stability, long half-life, and glow-type kinetics together with high light emission intensity, and thus would become one of the most valuable tools for bioluminescence assays. However, like other secreted luciferases, secNluc has to mix with the components in the conditioned medium surrounding test cells, or in the biological samples such as blood or urine after being secreted. These components may interfere with secNluc-catalyzed bioluminescence reactions and thus limit the application of the secNluc reporter system. In this study, we first examined the effects of three factors, pH, serum and residual reagents, on secNluc-catalyzed bioluminescence reactions, finding that these factors could interfere with bioluminescence reactions and result in background signal. To resolve these problems, we applied a simple affinity purification strategy in which secNluc was fused with a FLAG-tag, and anti-FLAG magnetic beads were used to catch and transfer the fusion protein to PBST, an optimal buffer for secNluc-catalyzed bioluminescence reactions that was identified in this study. The results indicated that this strategy could not only negate the interferences from serum or residual reagents and enhance the stability of light emission but also greatly increase signal intensity through enzyme enrichment. This strategy may contribute to biomedical studies that utilize secNluc and other secreted luciferases, especially those requiring superior sensitivity, low background noise and high reproducibility.

[Enhancing hRANKL production in Escherichia coli by optimizing culture conditions and lysing program].

RANKL/RANK/OPG axis is important in bone metabolism regulation, and becomes a popular research area in bone diseases. RANKL is a critical part of RANKL/RANK/OPG axis, and widely required in bone metabolism research. However, the yield of recombinant soluble human RANKL (hRANKL) in Escherichia coli is much lower than mouse RANKL (mRANKL). In this study, by adjusting and stabilizing the pH value of LB medium at 7.5, lowering the inducing temperature to 16 ℃ and optimizing the lysis program, the yield of soluble hRANKL increased by approximately 5 to 12-fold over the non-adjusted group. Our experiment effectively enhanced soluble hRANKL expression in E. coli and might constitute a meaningful attempt to obtain soluble expression of recombinant protein in E. coli.

[Construction and verification of NF-κB luciferase reporter gene system].

To quantify the transcriptional activity of NF-κB and to screen drugs related to the regulation of NF-κB activation, we constructed a recombinant plasmid through deleting the original CMV promoter of retrovirus vector pQCXIP and inserting the NF-κB enhancer and NanoLuc luciferase sequence into the vector. Then, using the recombinant plasmid we constructed a cell line in which the expression of NanoLuc luciferase (NLuc) was regulated by NF-κB. The inserted sequences were verified by restriction endonuclease digestion and sequencing. Tumor necrosis factor-α (TNF-α), an NF-κB activator, acted on the constructed NLuc cell line and leaded to the specific luciferase reaction. The luciferase reaction showed a fine time and dose dependence to the TNF-α stimulation, indicating the successful construction of the NF-κB regulated NLuc-expressing cell line. Besides, the NF-κB inhibitor, triptolide, reduced the expression of NLuc in a dose-dependent way. The constructed reporter system in this study could be applied in the quantification of the NF-κB transcriptional activity and in the NF-κB regulation-related drug screening.

[Changes to CD4(+)CD25(high+)CD127(low) regulatory T cells in peripheral blood from children with bronchiolitis, and its clinical significance].

OBJECTIVE: To study changes to CD4(+)CD25(high+)CD127(low) regulatory T cells (Treg) in peripheral blood from children with bronchiolitis, and to explore its clinical significance. METHODS: Thirty-one children with bronchiolitis and aged under two years were randomly enrolled as the bronchiolitis group, and 25 under two-year-olds with bronchopneumonia were randomly enrolled as the bronchopneumonia group. A further twenty-five children with non-infectious diseases such as hernia and renal calculus served as the control group. The level of CD4(+)CD25(high+)CD127(low) Treg in peripheral blood was measured by multi-color detection and multi-parameter flow cytometry. RESULTS: The proportion of CD4(+)CD25(high+)CD127(low) Treg in peripheral blood in the bronchiolitis group (8.0%±2.1%) was significantly lower than in the bronchopneumonia (9.6%±2.6%; P<0.05) and control groups (11.3%±2.9%; P<0.05). CONCLUSIONS: CD4(+)CD25(high+)CD127(low) Treg level in peripheral blood may be an index of immunological function in infants. A decreased level of CD4(+)CD25(high+)CD127(low) Treg in peripheral blood suggests that Treg cells may be involved in the pathogenesis and development of bronchiolitis.