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New research · Urology
Journal of Zhejiang University. Science. B · 4d
StudyJournal of Zhejiang University. Science. B · 2026

Selenocystine-based fluorescence assay combined with structural prediction for functional analysis of cystine transporter variants in cystinuria.

Xiaobai He, Xinyi Qian, Xiaoguang Zheng … Linjie Chen
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UrologyStudy

New assay measures cystine transporter affinity for selenocystine.

Selenocystine-based fluorescence assay combined with structural prediction for functional analysis of cystine transporter variants in cystinuria.

Xiaobai He … Linjie Chen
Journal of Zhejiang University. Science. B · 2026
Purpose

Thus, we aimed to develop a nonradioactive, cell-based method for the functional assessment of cystine transporters and mutation-specific pathologies.

Methods

Using human embryonic kidney 293 (HEK293) cells transiently co-expressing wild-type or mutant SLC3A1 and SLC7A9 , we developed an integrated approach that combined a selenocystine-based fluorescence uptake assay with AlphaFold3-based structural predictions to rapidly and accurately assess cystine transporter function and the molecular impact of genetic mutations.

(156.3±24.2) μmol/L
Results
(156.3±24.2) μmol/L
This Michaelis constant indicates the transporter's affinity for selenocystine.
More results

Using operational thresholds (mild >60%, moderate 20%‒60%, severe <20% residual activity), the assay differentiated the functional impacts of eight clinically characterized variants, including SLC7A9 A70V, A182T, G105R, R333W, V170M, A354T, and P482L, and SLC3A1 M467T, with categorical assignments consistent with previously published radioisotope-based functional data.

More results

AlphaFold3 modeling, combined with molecular docking, provides mechanistic interpretations of the dysfunction observed in the P482L and A354T mutants.

“
Conclusion · 1 of 2

The integrated approach employed in this work, which combines a sensitive selenocystine fluorescence assay with artificial intelligence (artificial intelligence)-powered structural analysis, enables the rapid, precise diagnosis of cystinuria variants.

Conclusion · 2 of 2

This platform is compatible with standard microplate-reader infrastructure and offers potential utility in variant-interpretation pipelines and future genotype-guided therapeutic decision-making, pending prospective clinical validation.

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