Differential effects of FcRn antagonists on the subcellular trafficking of FcRn and albumin
Guanglong Ma, Andrew R. Crowley, Liesbeth Heyndrickx, Ilse Rogiers, Eef Parthoens, Jolien Van Santbergen, Raimund J. Ober, Vladimir Bobkov, Hans de Haard, Peter Ulrichts, Erik Hofman, Els Louagie, Bianca Balbino, E. Sally Ward
Guanglong Ma, Andrew R. Crowley, Liesbeth Heyndrickx, Ilse Rogiers, Eef Parthoens, Jolien Van Santbergen, Raimund J. Ober, Vladimir Bobkov, Hans de Haard, Peter Ulrichts, Erik Hofman, Els Louagie, Bianca Balbino, E. Sally Ward
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Research Article Immunology

Differential effects of FcRn antagonists on the subcellular trafficking of FcRn and albumin

Abstract

The homeostasis of IgG is maintained by the neonatal Fc receptor, FcRn. Consequently, antagonism of FcRn to reduce endogenous IgG levels is an emerging strategy for treating antibody-mediated autoimmune disorders using either FcRn-specific antibodies or an engineered Fc fragment. For certain FcRn-specific antibodies, this approach has resulted in reductions in the levels of serum albumin, the other major ligand transported by FcRn. Cellular and molecular analyses of a panel of FcRn antagonists have been carried out to elucidate the mechanisms leading to their differential effects on albumin homeostasis. These analyses have identified 2 processes underlying decreases in albumin levels during FcRn blockade: increased degradation of FcRn and competition between antagonist and albumin for FcRn binding. These findings have potential implications for the design of drugs to modulate FcRn function.

Authors

Guanglong Ma, Andrew R. Crowley, Liesbeth Heyndrickx, Ilse Rogiers, Eef Parthoens, Jolien Van Santbergen, Raimund J. Ober, Vladimir Bobkov, Hans de Haard, Peter Ulrichts, Erik Hofman, Els Louagie, Bianca Balbino, E. Sally Ward

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Figure 2

Effects of FcRn antagonists on recycling of HSA by HEK293-hFcRn-GFP cells.

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Effects of FcRn antagonists on recycling of HSA by HEK293-hFcRn-GFP cell...
HEK293-hFcRn-GFP cells were incubated with 50 nM FcRn antagonist or medium for 24 hours. The cells were then incubated in serum-free medium for 2 hours, pulsed with 250 μg/mL AF647-labeled HSA (HSA-AF647) in serum-free medium for 1 hour, washed, and chased in serum-free medium for 0 (C-) or 30 minutes (C+) at 37°C in a 5% CO2 incubator. The cell-associated HSA-AF647 levels following the indicated treatments were determined using flow cytometry. (A) Schematic illustration of HSA recycling assay. (B) Data normalized against pulse-only levels (represented as 100%). These data are combined from 2 independent experiments, with triplicate samples in each experiment. One-way ANOVA was used for statistical analysis. Statistically significant differences are shown as *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001. Error bars indicate the standard deviation of the mean.