Sodium-iodide symporter

• OMIM: 601 843
• UniProt: Q92911
• MGI: 2149330

Of the sodium iodide symporter (NIS), and sodium iodide cotransporter, is a protein in the cell membrane, which catalyses the introduction of iodide ions from the blood into the cell. It is a transport protein. NIS is in all living things before except the plants. In human NIS is mainly produced in thyroid follicular, but also in smaller amounts in the mammary glands and the ovaries. Mutations in the SLC5A5 gene may lead to NIS deficiency and this to hypothyroidism ( Dyshormogene goiter).

The membrane transport equation reads:

Monovalent anions with a similar volume of ions such as iodide ( about 4 × 10-23 cm3) compete with this on the sodium - iodide symporter. As a solute can with NIS therefore except iodide also the anions bromide, chlorate, bromate, periodate, perchlorate, thiocyanate, selenocyanate, nitrate and tetrafluoroborate act. The iodide concentration in the cell can be 30 to 40 times higher than in plasma.

The human protein consists of 13 transmembrane domains with 643 amino acids and a molecular mass of 68 666 Da.

Regulation

Production of NIS is increased by inhibition of the PI3K signaling pathway, but also by radiation. The membrane transport by NIS can be stimulated with thyrotropin; Inhibition of transport is carried out by high Iodidkonzentation in the cell, but also for example, the perchlorate ion, which is a 30 times higher affinity than to NIS iodide.

Nuclear medicine application

Take by the ability to technetium or radioactive iodine, SLC5A5 is used in nuclear medicine as a reporter to document localization, functionality and treatability of (possibly degenerate malignant ) thyroid cells in vivo; with suitable radionuclides (eg, 131I, as beta emitters) also makes it possible therapy. Other radioisotopes, which are also transported by NIS, such as 211At could improve cancer therapy.