Comparison of expression optimization of new derivative of staphylokinase (SAK-2RGD-TTI) with the rSAK

Staphylokinase (SAK) is a promising thrombolytic agent for the treatment of patients suffering from blood-clotting disorders. To increase the potency of SAK and to minimize vessel reocclusion, a new construct bearing SAK motif fused to tsetse thrombin inhibitor (TTI) via a 20-amino acid linker with 2 RGD (2 × arginine-glycine-aspartic acid inhibiting platelet aggregation via attachment to integrin receptors of platelet) was codon optimized and expressed comparatively in Pichia pastoris GS115 as a Mut⁺ strain and KM71H as a Mut^s strain. Fusion protein was optimized in terms of best expression condition and fibrinolytic activity and compared with the rSAK. Expression level of the designed construct reached up to 175 mg/L of the culture medium after 72-hr stimulation with 2.5% methanol and remained steady for 3-4 days. The highest expression was obtained at the range of 2-3% methanol. The SAK-2RGD-TT (relative activity >82%) was more active at 25-37 °C than rSAK (relative activity of 93%). Further, it showed relative activity >80% at pH ranges of 7-9. Western blot analysis showed two bands of nearly 27 and 24 kDa at ratio of 5 to 3, respectively. The specific fibrinolytic activity of the SAK-2RGD-TTI was measured as 8,269 U/mg, and 19,616 U/mg for the nonpurified and purified proteins, respectively. Deglycosylation by using tunicamycin in culture medium resulted in higher fibrinolytic activity of SAK-2RGD-TTI (2.2 fold). Consequently, compared to the rSAK, at the same equimolar proportion, addition of RGD and TTI fragments could increase fibrinolytic activity. Also, P. pastoris can be considered as an efficient host for overexpression of the soluble SAK-2RGD-TTI with high activity without requiring a complicated purification procedure.

Production of Universal Group O Red Blood Cells by Alpha-N-Acetylgalactosaminidase Enzyme Expressed in Pichia pastoris

Enzymatic removal of blood groups antigens A and B is an efficient method for production of universal red blood cells. In this research, an α-N-acetylgalactosaminidase (NAGA) enzyme was expressed in Pichia pastoris for digestion of the A blood antigen. DNA sequence of the gene NAGA, originally expressed in Elizabethkingia meningosepticum (NAGA-EM), was ordered for optimization and synthesis. It was then expressed in P. pastoris (KM71H and GS115 strains). Expression of the recombinant NAGA was evaluated by dot blot, SDS-PAGE, and Western blotting. The activity of the enzyme was measured using a synthetic substrate in addition to the conversion of group A red blood cells to the O cells. Expression of NAGA-EM with an apparent molecular mass of 55 kDa was verified by dot blot, SDS-PAGE and Western blot analysis. The maximum enzyme activity in the supernatant of KM71H was higher than that in the GS115 (250 vs. 200 U/ml). Treated group A RBCs did not react with the anti-A antiserum or with the sera from individuals with blood groups B and O. The results of this study indicated that NAGA-EM is an efficient enzyme for production of universal O blood cells.

Induction of cytotoxicity and apoptosis in FLT3 mutant expressing cells using novel pyrimido cyanoacrylates and quinoline derivatives

BACKGROUND

Aberrant activation of FMS-like tyrosine kinase 3 (FLT3) is associated with acute myeloid leukemia (AML). Leukemic cells expressing constitutively active FLT3 mutants are resistance to the current cancer therapies (radiotherapy and chemotherapy); hence, there is an increased interest to identify new agents for the treatment of AML. The main aim of this study was evaluating cytotoxic effects of novel pyrimidocyanoacrylates and quinoline derivatives on FLT3 overexpressing cells.

MATERIALS AND METHODS

Five novel pyrimidocyanoacrylates & 2-chloro 3-carbaldehyde quinolone derivative compounds, E1QAC1, E1QAC2, E1QAC3, E1QAC4, and E1QAC5 were designed and synthesized at the Department of Chemistry, Faculty of Sciences, Ferdowsi University, Mashhad, Iran. FDC-P1 cells expressing human wild-type FLT3 (FD-FLT3-WT) and internal tandem duplication (ITD) mutants (FD-FLT3-ITD) used in this study. The cells maintained in DMEM medium supplemented with 10% fetal calf serum (FCS) and murine granulocyte-macrophage colony stimulating factor (mGM-CSF). Potency for induction of cytotoxicity (IC₅₀ value) and apoptosis was determined after treating the cells with concentration of the compounds by resazurin assay. Bax and Bcl2 activation status was also investigated by Western blot analysis.

RESULTS

All the compounds had concentration-dependent effects on inhibition of cell proliferation and induction of apoptosis in both cell lines. E1QAC4 was the most potent compound for inhibition of cell proliferation (with IC50 value of 19 μM) and apoptosis induction in the FLT3-WT cells. However, FD-FLT3-ITD cells were nearly five-times more resistant to all the compounds (except than E1QAC2) that the FLT3-WT expressing cells. Western blotting results also showed that FD-FLT3-ITD cells had lower levels of Bax and higher levels of Bcl2 than the FD-FLT3-WT cells.

CONCLUSION

The five novel heterocyclic compounds (E1QAC1-5) had cytotoxic effects and induced apoptosis in FD-FLT3 cells. Therefore, it is worthwhile to consider them as potential lead compound for development of new therapeutic agents for AML patients.