Elimination of N-glycosylation by site mutation further prolongs the half-life of IFN-α/Fc fusion proteins expressed in Pichia pastoris

Background

Interferon (IFN)-α has been commonly used as an antiviral drug worldwide; however, its short half-life in circulation due to its low molecular weight and sensitivity to proteases impacts its efficacy and patient compliance.

Results

In this study, we present an IgG1 Fc fusion strategy to improve the circulation half-life of IFN-α. Three different forms of IgG1 Fc fragments, including the wild type, aglycosylated homodimer and aglycosylated single chain, were each fused with IFN-α and designated as IFN-α/Fc-WT, IFN-α/Fc-MD, and IFN-α/Fc-SC, respectively. The recombinant proteins were expressed in Pichia pastoris and tested using antiviral and pharmacokinetic assays in comparison with the commercial pegylated-IFN-α (PEG-IFN-α). The in vitro study demonstrated that IFN-α/Fc-SC has the highest antiviral activity, while IFN-α/Fc-WT and IFN-α/Fc-MD exhibited antiviral activities comparable to that of PEG-IFN-α. The in vivo pharmacokinetic assay showed that both IFN-α/Fc-WT and IFN-α/Fc-MD have a longer half-life than PEG-IFN-α in SD rats, but IFN-α/Fc-SC has the shortest half-life among them. Importantly, the circulating half-life of 68.3 h for IFN-α/Fc-MD was significantly longer than those of 38.2 h for IFN-α/Fc-WT and 22.2 h for PEG-IFN-α.

Conclusions

The results demonstrate that the elimination of N-glycosylation by mutation of putative N-glycosylation site further prolongs the half-life of the IFN-α/Fc fusion protein and could present an alternative strategy for extending the half-life of low-molecular-weight proteins expressed by P. pastoris for in vivo studies as well as for future clinical applications.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-016-0601-9) contains supplementary material, which is available to authorized users.

Chelation therapy in Wilson's disease: from D-penicillamine to the design of selective bioinspired intracellular Cu(I) chelators

Wilson's disease is an orphan disease due to copper homeostasis dysfunction. Mutations of the ATP7B gene induces an impaired functioning of a Cu-ATPase, impaired Cu detoxification in the liver and copper overload in the body. Indeed, even though copper is an essential element, which is used as cofactor by many enzymes playing vital roles, it becomes toxic when in excess as it promotes cytotoxic reactions leading to oxidative stress. In this perspective, human copper homeostasis is first described in order to explain the mechanisms promoting copper overload in Wilson's disease. We will see that the liver is the main organ for copper distribution and detoxification in the body. Nowadays this disease is treated life-long by systemic chelation therapy, which is not satisfactory in many cases. Therefore the design of more selective and efficient drugs is of great interest. A strategy to design more specific chelators to treat localized copper accumulation in the liver will then be presented. In particular we will show how bioinorganic chemistry may help in the design of such novel chelators by taking inspiration from the biological copper cell transporters.

Hepatocyte-targeting single galactose-appended naphthalimide: a tool for intracellular thiol imaging in vivo

We present the design, synthesis, spectroscopic properties, and biological evaluation of a single galactose-appended naphthalimide (1). Probe 1 is a multifunctional molecule that incorporates a thiol-specific cleavable disulfide bond, a masked phthalamide fluorophore, and a single galactose moiety as a hepatocyte-targeting unit. It constitutes a new type of targetable ligand for hepatic thiol imaging in living cells and animals. Confocal microscopic imaging experiments reveal that 1, but not the galactose-free control system 2, is preferentially taken up by HepG2 cells through galactose-targeted, ASGP-R-mediated endocytosis. Probe 1 displays a fluorescence emission feature at 540 nm that is induced by exposure to free endogenous thiols, most notably GSH. The liver-specificity of 1 was confirmed in vivo via use of a rat model. The potential utility of this probe in indicating pathogenic states and as a possible screening tool for agents that can manipulate oxidative stress was demonstrated in experiments wherein palmitate was used to induce lipotoxicity in HepG2 cells.

Hepatocyte targeting and intracellular copper chelation by a thiol-containing glycocyclopeptide

Metal overload plays an important role in several diseases or intoxications, like in Wilson's disease, a major genetic disorder of copper metabolism in humans. To efficiently and selectively decrease copper concentration in the liver that is highly damaged, chelators should be targeted at the hepatocytes. In the present work, we synthesized a molecule able to both lower intracellular copper, namely Cu(I), and target hepatocytes, combining within the same structure a chelating unit and a carbohydrate recognition element. A cyclodecapeptide scaffold displaying a controlled conformation with two independent faces was chosen to introduce both units. One face displays a cluster of carbohydrates to ensure an efficient recognition of the asialoglycoprotein receptors, expressed on the surface of hepatocytes. The second face is devoted to metal ion complexation thanks to the thiolate functions of two cysteine side-chains. To obtain a chelator that is active only once inside the cells, the two thiol functions were oxidized in a disulfide bridge to afford the glycopeptide P(3). Two simple cyclodecapeptides modeling the reduced and complexing form of P(3) in cells proved a high affinity for Cu(I) and a high selectivity with respect to Zn(II). As expected, P(3) becomes an efficient Cu(I) chelator in the presence of glutathione that mimics the intracellular reducing environment. Finally, cellular uptake and ability to lower intracellular copper were demonstrated in hepatic cell lines, in particular in WIF-B9, making P(3) a good candidate to fight copper overload in the liver.