[Effect of knockdown of O-Glcnac transferase on hepatocyte fat synthesis]

Objective: To investigate the effect of knockdown of O-GlcNAc transferase (OGT) on hepatocyte fat synthesis. Methods: Liver cell line L02 were used to established the model of hepatic steatosis. The levels of OGT and O-GlcNAc protein were detected by Western blot. The OGT knockdown cell line of L02 cells was established, and its lipid formation ability was detected after induction of oleic acid (OA). Real-time quantitative PCR (qRT-PCR) and Western blot were used to detect mRNA and protein expression of enzymes related to fat synthesis. An independent sample t test was used. Results: Western blot showed that the expression of OGT and O-GlcNAc was increased in L02 cells after adipogenesis (P < 0.05). After shOGT lentivirus infects L02 cells, OGT mRNA levels were down-regulated (P < 0.01). Oil red O staining showed that the lipid in L02 shOGT cells decreased, qRT-PCR showed that the mRNA expressions of fat synthase (ACC1), (FASN) and (SCD1) were decreased, the difference was statistically significant (P < 0.05), protein Expression is consistent with mRNA expression. Conclusion: Knockdown of OGT can inhibit hepatocyte fat synthesis by reducing O-GlcNAc levels.

Preparation of single chain variable fragment of MG7 mAb by phage display technology

AIM: To develop the single chain variable fragment of MG₇ murine anti-human gastric cancer monoclonal antibody using the phage display technology for obtaining a tumor-targeting mediator.

METHODS: mRNA was isolated from MG₇ producing murine hybridoma cell line and converted into cDNA. The variable fragments of heavy and light chain were amplified separately and assembled into ScFv with a specially constructed DNA linker by PCR. The ScFvs DNA was ligated into the phagmid vector pCANTAB5E and the ligated sample was transformed into competent E. Coli TG1. The transformed cells were infected with M13K07 helper phage to form MG₇ recombinant phage antibody library. The volume and recombinant rate of the library were evaluated by means of bacterial colony count and restriction analysis. After two rounds of panning with gastric cancer cell line KATOIII of highly expressing MG₇-binding antigen, the phage clones displaying ScFv of the antibody were selected by ELISA from the enriched phage clones. The antigen binding affinity of the positive clone was detected by competition ELISA. HB2151 E.coli was transfected with the positive phage clone demonstrated by competition ELISA for production of a soluble form of the MG₇ ScFv. ELISA assay was used to detect the antigen-binding affinity of the soluble MG₇ ScFv. Finally, the relative molecular mass of soluble MG₇ ScFv was measured by SDS-PAGE.

RESULTS: The V-H, V-L and ScFv DNAs were about 340 bp, 320 bp and 750 bp, respectively. The volume of the library was up to 2 × 10⁶ and 8 of 11 random clones were recombinants. Two phage clones could strongly compete with the original MG₇ antibody for binding to the antigen expressed on KATOIII cells. Within 2 strong positive phage clones, the soluble MG₇ ScFv from one clone was found to have the binding activity with KATOIII cells. SDS-PAGE showed that the relative molecular weight of soluble MG₇ ScFv was 32.

CONCLUSION: The MG₇ ScFv was successfully produced by phage antibody technology, which may be useful for broadening the scope of application of the antibody.