Efficient expression of functional human coagulation factor IX in stably-transfected Drosophila melanogaster S2 cells; comparison with the mammalian CHO system

Glycosylation in Drosophila S2 cells

In recent years, there has been a remarkable surge in the approval of therapeutic protein drugs, particularly recombinant glycoproteins. Drosophila melanogaster S2 cells have become an appealing platform for the production of recombinant proteins due to their simplicity and low cost in cell culture. However, a significant limitation associated with using the S2 cell expression system is its propensity to introduce simple paucimannosidic glycosylation structures, which differs from that in the mammalian expression system. It is well established that the glycosylation patterns of glycoproteins have a profound impact on the physicochemical properties, bioactivity, and immunogenicity. Therefore, understanding the mechanisms behind these glycosylation modifications and implementing measures to address it has become a subject of considerable interest. This review aims to comprehensively summarize recent advancements in glycosylation modification in S2 cells, with a particular focus on comparing the glycosylation patterns among S2, other insect cells, and mammalian cells, as well as developing strategies for altering the glycosylation patterns of recombinant glycoproteins.

Enhanced functional recombinant factor IX production by human embryonic kidney cells engineered to overexpress VKORC1

Replacement therapy with recombinant drugs is the main therapeutic strategy for hemophilia B patients. To reduce the production costs of recombinant coagulation factors, improvement of their expression and activity by enhancement of γ-carboxylation might be of interest. The expression and functional activity of vitamin K-dependent (VKD) coagulation proteins rely, in part, on the VKD process of γ-carboxylation that is mediated by the enzymes γ-carboxylase and vitamin K epoxide reductase (VKOR). Since the recombinant production of VKD proteins is hampered by the inefficiency of this enzymatic process, we specifically have examined the stable expression of functional blood coagulation factor IX (FIX) in HEK293 cells following transient overexpression of VKORC1 as an important part of VKOR component. Recombinant hFIX-producing human embryonic kidney (HEK) cells were transfected to overexpress VKORC1. Following reverse transcription polymerase chain reaction (RT-PCR) analysis, expression efficiency of the active hFIX was analyzed by performing enzyme-linked immunosorbent assay and coagulation test. In addition, to quantify γ-carboxylated recombinant FIX, the barium citrate method was used. Overexpression of VKORC1 in FIX-producing HEK cells, resulting in a 3.2-fold higher expression of functional FIX, which displayed a 1.4-fold enhanced specific activity. Moreover, a 3.9-fold enhanced recovery of fully γ-carboxylated FIX following barium citrate adsorption was achieved. Collectively, these findings indicate that the overexpression of VKORC1 results in the production of higher levels of functional hFIX in HEK293 cells. The increase of the VKORC1 as a supplier of γ-carboxylase seems to play a significant role in increasing the amount and efficiency of recombinant FIX production, thereby reducing the production costs.

Improved activity and expression of recombinant human factor IX by propeptide engineering

PURPOSE

The main therapeutic strategy for Hemophilia B patients involves the administration of recombinant coagulation factors IX (rFIX). Although there are various approaches to increasing the activity of rFIX, targeted protein engineering of specific residues could result in increased rFIX activity through enhanced γ-carboxylation. Specific amino acids in the propeptide sequence of vitamin K-dependent proteins are known to play a role in the interaction with the enzyme γ-carboxylase. The net hydrophobicity and charge of the γ-carboxylic recognition site (γ-CRS) region in the propeptide are important determinants of γ-carboxylase binding. So the contribution of individual γ-CRS residues to the expression of fully γ-carboxylated and active FIX was studied.

METHODS

Propeptide residues at positions -14, -13, or - 12 were substituted for equivalent prothrombin amino acids by SEOing PCR. The recombinant FIX variants were transfected and stably expressed in Drosophila S2 cells, and the expression of both total FIX protein and active FIX was assessed.

RESULTS

While overall the substitutions resulted in an increase of both total FIX protein expression as well as an increase in the portion of active FIX, the highest increase in FIX protein expression, FIX activity, and specific FIX activity was observed following the simultaneous substitution of residues at positions -12, -13, and - 14. The enhanced rFIX activity was further confirmed by enrichment for functional, fully γ-carboxylated rFIX species via barium citrate adsorption.

CONCLUSION

Our findings indicate that by increasing both the net charge and the net hydrophobicity of the FIX γ-CRS region, the expression of fully γ-carboxylated and as such active FIX is enhanced. Graphical abstract .

Effect of propeptide amino acid substitution in γ-carboxylation, activity and expression of recombinant human coagulation factor IX

The production of recombinant vitamin K dependent (VKD) proteins for therapeutic purposes is an important challenge in the pharmaceutical industry. These proteins are primarily synthesized as precursor molecules and contain pre-propeptide sequences. The propeptide is connected to γ-carboxylase enzyme through the γ-carboxylase recognition site for the direct γ-carboxylation of VKD proteins that has a significant impact on their biological activity. Propeptides have different attitudes toward γ-carboxylase and certain amino acids in propeptide sequences are responsible for the differences in γ-carboxylase affinity. By aiming to replace amino acids in hFIX propeptide domain based on the prothrombin propeptide, pMT-hFIX-M14 expression cassette, containing cDNA of hFIX with substituted -14 residues (Asp to Ala) was made. After transfection of Drosophila S2 cells, expression of the active hFIX was analyzed by performing ELISA and coagulation test. A 1.4-fold increase in the mutant recombinant hFIX expression level was observed in comparison with that of a native recombinant hFIX. The enhanced hFIX activity and specific activity of the hFIXD-14A (2.2 and 1.6 times, respectively) were further confirmed by comparing coagulation activity levels of substituted and native hFIX. Enrichment for functional, fully γ-carboxylated hFIX species via barium citrate adsorption demonstrated 2-fold enhanced recovery in the S2-expressing hFIXD-14A relative to that expressed native hFIX. These results show that changing -14 residues leads to a decrease in the binding affinity to substrate, increase in γ-carboxylation and activity of recombinant hFIX. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:515-520, 2018.

Investigations into, and development of, a lyophilized and formulated recombinant human factor IX produced from CHO cells

OBJECTIVES

To develop a recombinant human factor IX (rFIX) formulation equivalent to commercially available products in terms of cake appearance, residual moisture, proportion of soluble aggregates and activity maintenance for 3 months at 4-8 °C.

RESULTS

NaCl and low bulking agent/cryoprotectant mass ratio had a negative impact on cake quality upon lyophilisation for a wide range of formulations tested. Particular devised formulations maintained rFIX activity after lyophilization with a similar performance when compared with the rFIX formulated using the excipients reported for a commercially available FIX formulation (Benefix). rFIX remained active after 3 months when stored at 4 °C, though this was not the case with samples stored at 40 °C. Interestingly, particular formulations had an increase in residual moisture after 3 months storage, but not above a 3% threshold. All four formulations tested were equivalent to the Benefix formulation in terms of particle size distribution and cake appearance.

CONCLUSIONS

Three specific formulations, consisting of surfactant polysorbate-80, sucrose or trehalose as cryoprotectant, mannitol or glycine as bulking agent, L-histidine as buffering agent, and NaCl added in the reconstitution liquid at 0.234% (w/v) were suitable for use with a CHO cell-derived recombinant FIX.

Optimized expression of the antimicrobial protein Gloverin from Galleria mellonella using stably transformed Drosophila melanogaster S2 cells

Antimicrobial proteins and peptides (AMPs) are valuable as leads in the pharmaceutical industry for the development of novel anti-infective drugs. Here we describe the efficient heterologous expression and basic characterization of a Gloverin-family AMP derived from the greater wax moth Galleria mellonella. Highly productive single-cell clones prepared by limiting dilution achieved a 100% increase in productivity compared to the original polyclonal Drosophila melanogaster S2 cell line. Comprehensive screening for suitable expression conditions using statistical experimental designs revealed that optimal induction was achieved using 600 µM CuSO4 at the mid-exponential growth phase. Under these conditions, 25 mg/L of the AMP was expressed at the 1-L bioreactor scale, with optimal induction and harvest times ensured by dielectric spectroscopy and the online measurement of optical density. Gloverin was purified from the supernatant by immobilized metal ion affinity chromatography followed by dialysis. In growth assays, the purified protein showed specific antimicrobial activity against two different strains of Escherichia coli.