Pendrin

Pendrin, also known as sodium-independent chloride/iodide transporter, is a is_associated_with::protein that in humans is encoded by the SLC26A4 is_associated_with::gene (solute carrier family 26, member 4). Pendrin is the protein which is mutated in is_associated_with::Pendred syndrome, which is an autosomal recessive disorder characterized by sensorineural hearing loss, goiter and a partial organification problem detectable by a positive perchlorate test.

By phylogenetic analysis, pendrin has been found to be a close relative of is_associated_with::prestin present on the hair cells or organ of corti in the inner ear. Prestin is primarily an electromechanical transducer but pendrin is an ion transporter.

Function
Pendrin is an ion exchanger found in many types of cells in the body. For example it is found in the is_associated_with::cortical collecting duct lining cells in the kidney.

Pendrin is found at the apical (luminal) membrane of follicular cells in the thyroid gland. It transports iodide from the cytoplasm to the follicle lumen. Its activity is necessary for production of is_associated_with::thyroid hormone.

Pendrin is also found in the cells of the inner ear, where its function is not well understood.

Clinical significance
Mutations in this gene are associated with is_associated_with::Pendred syndrome, the most common form of syndromic is_associated_with::deafness, an autosomal-recessive disease. Pendred syndrome is also characterized by is_associated_with::hypothyroidism. SLC26A4 is highly homologous to the is_associated_with::SLC26A3 gene; they have similar genomic structures and this gene is located 3' of the SLC26A3 gene. The encoded protein has homology to sulfate transporters.

Another little-understood role of pendrin is in airway hyperreactivity and is_associated_with::inflammation, as during asthma attacks and allergic reactions. Expression of pendrin in the lung increases in response to allergens and high concentrations of IL-13, and overexpression of pendrin results in airway inflammation, hyperreactivity, and increased mucus production. These symptoms could result from pendrin's effects on ion concentration in the airway surface liquid, possibly causing the liquid to be less hydrated.