NIS (product of the SLC5A5 gene) transports iodide (I-), and other anions including ClO4-, SCN-, and Br-. NIS is expressed in the thyroid, colon, ovary, and in human breast cancers. It mediates the active transport and the concentration of iodide from the blood into thyroid follicular cells, a fundamental step in thyroid hormone biosynthesis, and is the basis of radioiodine therapy for thyroid cancer []. Mutation in the SLC5A5 gene can result in a form of thyroid hormone dysgenesis [, ]. Human NIS exists mainly as a dimer stabilized by a disulfide bridge []. This subgroup belongs to the solute carrier 5 (SLC5) transporter family.
