Related Experiment Video
Updated: May 1, 2026
Monitoring Cell-to-cell Transmission of Prion-like Protein Aggregates in Drosophila Melanogaster
Published on: March 12, 2018
Fluorescence quantitation of thyrocyte iodide accumulation with the yellow fluorescent protein variant
Kerry J Rhoden1, Stefano Cianchetta, Serena Duchi
1Laboratory of Medical Genetics, Department of Internal Medicine, Cardiology, and Hepatology, University of Bologna, 40138 Bologna, Italy. kerry.rhoden@unibo.it
Insights
This study introduces a novel biosensor, YFP-H148Q/I152L, for quantifying iodide uptake in thyroid cells. The biosensor effectively measures iodide accumulation, crucial for thyroid hormone synthesis.
Area of Science:
- Cell Biology
- Biochemistry
- Endocrinology
Background:
- The thyroid gland requires iodide for synthesizing essential thyroid hormones.
- Accurate quantification of iodide uptake is vital for understanding thyroid function and related disorders.
Purpose of the Study:
- To develop and validate a live cell imaging method for quantifying iodide accumulation in cultured thyroid cells.
- To assess the sensitivity and selectivity of the halide-sensitive yellow fluorescent protein (YFP) variant YFP-H148Q/I152L as an iodide biosensor.
Main Methods:
- Utilized the YFP-H148Q/I152L variant for live cell imaging of iodide in FRTL-5 thyrocytes.
- Performed in vivo calibrations to determine YFP-H148Q/I152L sensitivity to iodide and other halides.
- Investigated iodide influx and efflux kinetics using saturation kinetics analysis.
Main Results:
- YFP-H148Q/I152L demonstrated 20-fold selectivity for iodide over chloride, with pH-dependent halide suppression.
- FRTL-5 cells concentrated iodide up to 60 times the extracellular levels.
- Quantified iodide transport kinetics, including K(m) and V(max) values for both influx and efflux.
Conclusions:
- YFP-H148Q/I152L is a sensitive and selective biosensor for accurately measuring iodide accumulation in thyroid cells.
- This imaging technique provides valuable insights into iodide transport mechanisms in thyroid physiology.
Abstract:
The thyroid gland accumulates iodide for the synthesis of thyroid hormones. The aim of the current study was to quantify iodide accumulation in cultured thyroid cells by live cell imaging using the halide-sensitive yellow fluorescent protein (YFP) variant YFP-H148Q/I152L. In vivo calibrations were performed in FRTL-5 thyrocytes to determine the sensitivity of YFP-H148Q/I152L to iodide. In the presence of ion-selective ionophores, YFP-H148Q/I152L fluorescence was suppressed by halides in a pH-dependent manner with 20-fold selectivity for iodide versus chloride and competition between the two halides. At a physiological pH of 7 and a chloride concentration of 15mM, the affinity constant of YFP-H148Q/I152L for iodide was 3.5mM. In intact FRTL-5 cells, iodide induced a reversible decrease in YFP-H148Q/I152L fluorescence. FRTL-5 cells concentrated iodide to 60 times the extracellular concentration. Iodide influx exhibited saturation kinetics with respect to extracellular iodide with a K(m) of 35 microM and a V(max) of 55 microM/s. Iodide efflux exhibited saturation kinetics with respect to intracellular iodide concentration with a K(m) of 2.2mM and a V(max) of 43 microM/s. The results of this study demonstrate the utility of YFP-H148Q/I152L as a sensitive and selective biosensor for the quantification of iodide accumulation in thyroid cells.
