ABSTRACT
The manipulation of redox potential in secretory pathway by thiol reducing agents can be a strategy to improve the production levels of disulfide-bonded proteins including recombinant antibodies. Here we have studied the influence of cysteamine on viability and the production level of IgG[4] in Sp2.0 cells. For this purpose, the recombinant Sp2.0 cells producing an anti CD33 IgG[4], were subjected to different concentrations of cysteamine. At concentrations of 2, 4 and 5 mM cysteamine, the secreted levels of IgG[4] did not change significantly. However, in concentration of 7 mM cysteamine, a significant decrease was observed in IgG[4] levels which may indicate the cytotoxicity of this compound in higher concentrations. Our results show that the cysteamine treatment reduces the cell viability in a dose-dependent manner. Also it was observed that 2 mM cysteamine had no late effect on IgG4 production level and only at day 3, this concentration of cysteamine decreased the cell viability significantly. To test whether the addition of cysteamine can affect the expression level of protein disulfide isomerase, RT-PCR analysis was carried out. The results revealed that cysteamine does not affect the PDI transcription and expression level of IgG[4] in this type of recombinant cells
Subject(s)
Cell Growth Processes/drug effects , Cell Survival/drug effects , Immunoglobulin GABSTRACT
The study of physiological changes in recombinant cell lines provides useful information to improve production performance. In this study, we investigate the effects of an anti-CD33 chimeric IgG4 expression on Sp2.0 cell growth. Variable region genes of light and heavy chains of monoclonal antibody produced by M195 were cloned in pFUSE-CLIg-hk and pFUSE-CHIg-hG4 expression vectors, respectively. Transfection of recombinant plasmids into Sp2.0 cell lines was performed using lipofectamine in two steps. Positive transformant cells were isolated and subjected to PCR, RT-PCR and Western blot analysis to confirm the integration of gene cassettes and the expression of recombinant IgG4. To assess the growth parameters, recombinant and parent Sp2.0 cell lines were seeded at a density of 1×10[5] cells/ml in duplicate into 12-well plates. For nine days, culture plates were sampled daily and viable cell count and viability determined. The results of PCR, RT-PCR and Western blot analyses confirmed the generation of stable producer cell lines. In recombinant cells, the maximum cell density decreased by 46%. However, it was observed that IgG4 expression had no effect on cell viability of these transfectants. Our results showed that the expression of recombinant IgG4 can change growth parameters in Sp2.0 cell lines that express the pFUSE-CHIg-hG4-pFUSE-CLIg-hk construct
ABSTRACT
Bone Morphogenetic Proteins [BMPs] belong to the transforming growth factor-beta [TGF-beta] superfamily, and play an important role in bone metabolism. Recombinant forms of BMP-2 and BMP-7 are the only BMPs used clinically. In this study the mature part of human bone morphogenetic protein-7 [BMP-7] was engineered through substitution of the BMP-7 Nterminal sequence by heparin-binding site of BMP-2. This targeted substitution was made to enhance the binding affinity of the novel protein to the extracellular matrix components such as heparin and heparan sulfate proteoglycans [HSPGs]. The engineered protein was expressed in Escherichia coli [E.coli]. The PelB signal sequence was used to translocate soluble proteins into the periplasmic space of E.coli. The protein was purified from periplasmic extract using Ni-NTA chromatography and the SDS-PAGE and western blot analysis confirmed the successful expression of the novel protein. The novel hBMP-7 mutant was produced as approximately 16 kDa monomer. It was found that the heparin binding of this protein was approximately 50% more than that of the wild-type at a protein concentration of 500 ng/ml. The findings showed that the periplasmic expression may be suitable to produce complex proteins like BMPs