The mammalian expression system plays a key central role in the production of therapeutic recombinant proteins. Conspicuously, any improvements in the expression system which lead to a higher ...expression level would have an impact especially in bio-pharmaceutical industries. In the current study, to take steps toward the improvement of expression of recombinant protein, first, we established a stable HEK293 cell line to overexpress a well-known cytoprotective and antioxidant gene, Nrf2. Next, we transiently expressed human recombinant coagulation factor VII, as an example of human recombinant protein, in the engineered-HEK293 cell line. Our results revealed that the established cells had a higher growth rate and were able to endure to UV-induced oxidative stress. Furthermore, within our expectation, our results revealed that the expression level of recombinant FVII in Nrf2-engineered HEK293 cells (315 ng/ml) was higher than the HEK293 (198 ng/ml) cells and it was functional in a coagulation test assay. Moreover, our new cell line could be a suitable cell to express other recombinant proteins especially for large-scale production of recombinant protein under other culture condition such as lower serum and suspension culture that imposed advantages especially in terms of cost benefits in bio-pharmaceutical industries.
Numerous matrix attachment regions (MARs) have been used to improve transgene expression in genetic engineering, but an efficient and stable expression vector is lacking. In the present study, a ...vector named pCCF containing chloramphenicol acetyltransferase (CAT) reporter gene cassettes was constructed. The cassettes were flanked by a β-interferon MAR at the 5′ upstream of the reporter gene cassettes, and a β-globin MAR at the 3′ site. After transfecting pCCF into Chinese hamster ovary cells, the expression level of the CAT gene with a MAR was effectively increased to about 4.5-fold higher than that transfected with pCAM (containing two β-globin MARs flanking the expression cassette), and to 46.4-fold higher than that transfected with the control plasmid pCAG (without MARs). Quantitative reverse transcription polymerase chain reaction and the 2−ΔΔCt method were used to analyze the CAT gene relative copy numbers. The expression levels were found to be not directly proportional to the gene copy numbers when MAR elements from different sources were used. However, the presence of MARs improved the transgene copy numbers.
► Matrix attachment regions have been used to improve transgene expression in genetic engineering. ► We constructed a vector named pCCF contained different MARs flanking the expression cassette. ► The MARs of pCCF efficiently and stably increased the transgene expression level. ► Expression levels were not directly proportional to the gene copy numbers using different MARs. ► The presence of MARs improved the transgene copy numbers.
RNA polymerase II carboxyl-terminal domain (RNAPII CTD) phosphatases are responsible for the dephosphorylation of the C-terminal domain of the small subunit of RNAPII in eukaryotes. Recently, we ...demonstrated the identification of several interacting partners with human small CTD phosphatase1 (hSCP1) and the substrate specificity to delineate an appearance of the dephosphorylation catalyzed by SCP1. In this study, using the established cells for inducibly expressing hSCP1 proteins, we monitored the modification of β-O-linked N-acetylglucosamine (O-GlcNAc). O-GlcNAcylation is one of the most common post-translational modifications (PTMs). To gain insight into the PTM of hSCP1, we used the Western blot, immunoprecipitation, succinylayed wheat germ agglutininprecipitation, liquid chromatography-mass spectrometry analyses, and site-directed mutagenesis and identified the Ser41 residue of hSCP1 as the O-GlcNAc modification site. These results suggest that hSCP1 may be an O-GlcNAcylated protein in vivo, and its N-terminus may function a possible role in the PTM, providing a scaffold for binding the protein(s).
Pigeon circovirus (PiCV) is the most recurrent virus diagnosed in pigeons and is among the major causative agents of young pigeon disease syndrome (YPDS). Due to the lack of an established laboratory ...protocol for PiCV cultivation, development of prophylaxis is hampered. Alternatively, virus-like particles (VLPs), which closely resemble native viruses but lack the viral genetic material, can be generated using a wide range of expression systems and are shown to have strong immunogenicity. Therefore, the use of VLPs provides a promising prospect for vaccine development. In this study, transfected human embryonic kidney (HEK-293) cells, a mammalian expression system, were used to express the PiCV capsid protein (Cap), which is a major component of PiCV and believed to contain antibody epitopes, to obtain self-assembled VLPs. The VLPs were observed to have a spherical morphology with diameters ranging from 12 to 26 nm. Subcutaneous immunization of pigeons with 100 µg PiCV rCap-VLPs supplemented with water-in-oil-in-water (W/O/W) adjuvant induced specific antibodies against PiCV. Observations of the cytokine expression and T-cell proliferation levels in spleen samples showed significantly higher T-cell proliferation and IFN- γ expression in pigeons immunized with VLPs compared to the controls (
< 0.05). Experimentally infected pigeons that were vaccinated with VLPs also showed no detectable viral titer. The results of the current study demonstrated the potential use of PiCV rCap-VLPs as an effective vaccine candidate against PiCV.
The Fc portion of immunoglobulin G (IgG) recruits complements and its cognate receptors, thereby promoting defensive mechanisms in the humoral immune system. These effector functions critically ...depend on N-glycosylation at the Fc region, which is therefore regarded as a crucial factor in the design and production of therapeutic antibodies. NMR spectroscopy plays a unique role in the characterization of conformational dynamics and intermolecular interactions of IgG-Fc in solutions. Here, we report NMR assignments of the glycosylated Fc fragment (Mr 53 kDa), cleaved from a chimeric antibody with human IgG1 constant regions, which was produced in Chinese hamster ovary cells with uniform (13)C- and (15)N-labeling.
Plexins are type I membrane proteins that function as receptors for semaphorins. All of the known plexins contain a large globular domain, termed the sema domain, in the N-terminal extracellular ...region, which interacts with semaphorins during signal transduction. Here, we describe procedures for protein production and purification that we utilized in the crystallographic study of the mouse Plexin A2 (mPlxnA2) extracellular fragment, including the sema domain. A mutant mammalian cell line, HEK293S GnTI
, was used as an expression host for the production of a crystallizable-quality mPlxnA2 fragment, which contains several N-glycosylation sites and disulfide bonds.
Plasmodium falciparum is the aetiological agent for malaria, a deadly infectious disease for which no vaccine has yet been licensed. The proteins displayed on the merozoite cell surface have long ...been considered attractive vaccine targets because of their direct exposure to host antibodies; however, progress in understanding the functional role of these targets has been hindered by technical challenges associated with expressing these proteins in a functionally active recombinant form. To address this, a method that enables the systematic expression of functional extracellular Plasmodium proteins was previously developed, and used to create a library of 42 merozoite proteins.
To compile a more comprehensive library of recombinant proteins representing the repertoire of P. falciparum merozoite extracellular proteins for systematic vaccine and functional studies, genome-wide expression profiling was used to identify additional candidates. Candidate proteins were recombinantly produced and their integrity and expression levels were tested by Western blotting and ELISA.
Twenty-five additional genes that were upregulated during late schizogony, and predicted to encode secreted and cell surface proteins, were identified and expressed as soluble recombinant proteins. A band consistent with the entire ectodomain was observed by immunoblotting for the majority of the proteins and their expression levels were quantified. By using sera from malaria-exposed immune adults, the immunoreactivity of 20 recombinant proteins was assessed, and most of the merozoite ligands were found to carry heat-labile epitopes. To facilitate systematic comparative studies across the entire library, multiple Plasmodium proteins were simultaneously purified using a custom-made platform.
A library of recombinant P. falciparum secreted and cell surface proteins was expanded by 20 additional proteins, which were shown to express at usable levels and contain conformational epitopes. This resource of extracellular P. falciparum merozoite proteins, which now contains 62 full-length ectodomains, will be a valuable tool in elucidating the function of these proteins during the blood stages of infection, and facilitate the comparative assessment of blood stage vaccine candidates.
When cytotoxic T lymphocytes (CTL) or natural killer (NK) cells recognize tumor cells or cells infected with intracellular pathogens, they release their cytotoxic granule content to eliminate the ...target cells and the intracellular pathogen. Death of the host cells and intracellular pathogens is triggered by the granule serine proteases, granzymes (Gzms), delivered into the host cell cytosol by the pore forming protein perforin (PFN) and into bacterial pathogens by the prokaryotic membrane disrupting protein granulysin (GNLY). To investigate the molecular mechanisms of target cell death mediated by the Gzms in experimental in-vitro settings, protein expression and purification systems that produce high amounts of active enzymes are necessary. Mammalian secreted protein expression systems imply the potential to produce correctly folded, fully functional protein that bears posttranslational modification, such as glycosylation. Therefore, we used a cost-efficient calcium precipitation method for transient transfection of HEK293T cells with human Gzms cloned into the expression plasmid pHLsec. Gzm purification from the culture supernatant was achieved by immobilized nickel affinity chromatography using the C-terminal polyhistidine tag provided by the vector. The insertion of an enterokinase site at the N-terminus of the protein allowed the generation of active protease that was finally purified by cation exchange chromatography. The system was tested by producing high levels of cytotoxic human Gzm A, B and M and should be capable to produce virtually every enzyme in the human body in high yields.
RNA polymerase II carboxyl-terminal domain (RNAPII CTD) phosphatases are responsible for the dephosphorylation of the C-terminal domain of the small subunit of RNAPII in eukaryotes. Recently, we ...demonstrated the identification of several interacting partners with human small CTD phosphatase1 (hSCP1) and the substrate specificity to delineate an appearance of the dephosphorylation catalyzed by SCP1. In this study, using the established cells for inducibly expressing hSCP1 proteins, we monitored the modification of β-O-linked N-acetylglucosamine (O-GlcNAc). O-GlcNAcylation is one of the most common post-translational modifications (PTMs). To gain insight into the PTM of hSCP1, we used the Western blot, immunoprecipitation, succinylayed wheat germ agglutininprecipitation, liquid chromatography-mass spectrometry analyses, and site-directed mutagenesis and identified the Ser41 residue of hSCP1 as the O-GlcNAc modification site. These results suggest that hSCP1 may be an O-GlcNAcylated protein in vivo, and its N-terminus may function a possible role in the PTM, providing a scaffold for binding the protein(s).
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