iodide transport

Definition

Target type: biologicalprocess

The directed movement of iodide into, out of or within a cell, or between cells, by means of some agent such as a transporter or pore. [GOC:krc]

Iodide transport is a crucial biological process for the synthesis of thyroid hormones, which regulate metabolism, growth, and development. The process begins with the active transport of iodide ions from the bloodstream into thyroid follicular cells, facilitated by the sodium-iodide symporter (NIS). This protein is located on the basolateral membrane of the follicular cell, where it couples the movement of iodide ions against their concentration gradient to the inward movement of sodium ions down their electrochemical gradient.

Once inside the follicular cell, iodide ions are transported to the apical membrane, facing the lumen of the follicle, by pendrin, a chloride/iodide exchanger. This transport is driven by the electrochemical gradient of chloride ions.

In the follicular lumen, iodide ions are oxidized to iodine by the enzyme thyroid peroxidase (TPO). This oxidation reaction occurs in the presence of hydrogen peroxide, which is produced by the enzyme dual oxidase 2 (DUOX2). The iodine then reacts with tyrosine residues on thyroglobulin, a large glycoprotein produced and secreted by the follicular cells, forming monoiodotyrosine (MIT) and diiodotyrosine (DIT).

Finally, two molecules of DIT combine to form thyroxine (T4), the major thyroid hormone, or one molecule of MIT and one of DIT combine to form triiodothyronine (T3). These hormones are stored within the thyroglobulin molecule and are released into the bloodstream by proteolytic enzymes.

The regulation of iodide transport is tightly controlled by several factors, including TSH (thyroid-stimulating hormone), which stimulates the expression of NIS and other proteins involved in iodide uptake and hormone synthesis. Iodide deficiency can lead to hypothyroidism, while excess iodide can cause hyperthyroidism.'
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Proteins (2)

Compounds (45)