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Cloning and characterization of the thyroid iodide transporter
1Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Nature
|February 1, 1996
Summary
Researchers cloned the complementary DNA (cDNA) for the sodium-iodide symporter, a key protein in thyroid hormone production. This discovery provides a crucial link in understanding and treating thyroid disorders.
Area of Science:
- Biochemistry
- Molecular Biology
- Endocrinology
Background:
- Iodide is essential for thyroid hormone synthesis (T3 and T4).
- Thyroid iodide uptake is mediated by the Na+/I- symporter, vital for thyroid function.
- The Na+/I- symporter's molecular identity remained elusive despite its importance.
Purpose of the Study:
- To isolate and characterize the complementary DNA (cDNA) encoding the Na+/I- symporter.
- To provide the first molecular identification of the iodide transporter in the thyroid.
Main Methods:
- Functional screening of a rat thyroid cell line (FRTL-5) cDNA library in Xenopus laevis oocytes.
- In vitro RNA transcription from the isolated cDNA clone.
- Assay of Na+/I- symport activity in oocytes post-microinjection.
Main Results:
- Successful isolation of a cDNA clone encoding the Na+/I- symporter.
- Oocyte microinjection of in vitro transcribed RNA resulted in a >700-fold increase in Na+/I- symport activity.
- Demonstrated perchlorate-sensitive iodide transport, confirming symporter function.
Conclusions:
- The first molecular identification and cDNA cloning of the Na+/I- symporter.
- This finding provides a critical missing link in the thyroid hormone biosynthetic pathway.
- Enables further research into thyroid disorders and potential therapeutic strategies.