Inconsistent conclusions on the cellular uptake of recombinant human β-glucocerebrosidase (rhGCase) for Gaucher disease stem from a fundamental limitation of existing methods: their inability to generate complete and reliable dose–response curves. This critical flaw, stemming from susceptibility to various experimental variables, prevents accurate potency comparison across different rhGCase products. To address this, we developed a robust bioassay using CHO-K1 cells stably expressing the human macrophage mannose receptor (hMMR). Our method quantifies uptake by measuring the enzymatic activity of internalized rhGCase and consistently produces a classic sigmoidal dose–response curve. Comprehensive validation and mechanistic studies, including inhibition experiments with mannose, fucose, and mannose-6-phosphate, confirmed that uptake is specifically mediated by hMMR, with successful enzyme transport to endosomes/lysosomes. Applying this assay to three commercial products yielded results contrary to prior literature: imiglucerase demonstrated superior uptake activity to velaglucerase alfa. The proposed method represents a significant improvement over existing assays, providing a more accurate and reproducible means to evaluate cellular uptake bioactivity, which is crucial for the quality control of rhGCase therapeutics.
Wang et al. (Sat,) studied this question.
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