The Na+/I- symporter (NIS): recent advances

Area of Science:

• Molecular Endocrinology
• Cellular Physiology
• Genetics

Background:

• The sodium/iodide symporter (NIS) facilitates iodide uptake into thyroid cells, a critical step for thyroid hormone synthesis.
• Advances in molecular biology have enabled detailed studies of NIS function and regulation.

Purpose of the Study:

• To elucidate the molecular mechanisms of NIS function, regulation, and genetic basis.
• To characterize NIS in both thyroidal and extrathyroidal tissues.

Main Methods:

• Isolation and characterization of rat and human NIS cDNA and gene.
• Electrophysiological analysis to determine NIS stoichiometry and specificity.
• Biochemical and immunological assays to test NIS structure and expression.
• Mutation analysis in patients with iodide transport defects.

Main Results:

• High-affinity antibodies against NIS were generated.
• NIS stoichiometry, specificity, and secondary structure were elucidated.
• Regulation of NIS expression by thyroid stimulating hormone and iodide was monitored.
• The rat NIS gene promoter was characterized.
• Human NIS cDNA was isolated, and its genomic organization determined.
• NIS mutations causing congenital iodide transport deficiency were described.
• NIS was identified in extrathyroidal tissues.

Conclusions:

• Molecular characterization of NIS has significantly advanced understanding of thyroid hormone biosynthesis and iodide transport.
• NIS plays a role beyond the thyroid, with implications for iodide homeostasis and disease.
• Identification of NIS mutations provides insights into congenital iodide transport defects.