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Pendrin

Role pendrinu při syntéze hormonu štítné žlázy

Pendrin je membránová buněčná pumpa s 11 transmembránovými řetězci, zejména přenášející jód přes membránu. Je to obvykle chlorido–jodidový, ale také chlorido–hydroxylový a chlorido–bikarbonátový přenašeč aniontů. U člověka se vyskytuje ve štítné žláze, vnitřním uchu, ledvinách, placentě a prsní žláze. Mutace genu pro pendrin způsobuje hluchotu nebo Pendredův syndrom, kombinované onemocnění ucha a štítné žlázy.

Literatura

Pendrin a jeho úloha v patogenezi kongenitální hypotyreózy a dalších onemocnění
Oxford dictionary of biochemistry and molecular biology; revised edition. Příprava vydání R. Cammack et al. New York: Oxford university press, 2006. ISBN 0-19-852917-1.

Média použitá na této stránce

Thyroid hormone synthesis.svg
Autor: Mikael Häggström, Licence: CC0
Synthesis of thyroid hormones.

Reference:

Chapter 48, "SYNTHESIS OF THYROID HORMONES" in: Walter F., PhD. Boron (2003) Medical Physiology: A Cellular And Molecular Approach, Elsevier/Saunders, pp. 1,300 ISBN: 1-4160-2328-3.

Thyroglobulin is synthesized in the rough endoplasmic reticulum and follows the secretory pathway to enter the colloid in the lumen of the thyroid follicle by exocytosis.
Meanwhile, a sodium-iodide (Na/I) symporter pumps iodide (I^-) actively into the cell, which previously has crossed the endothelium by largely unknown mechanisms.
This iodide enters the follicular lumen from the cytoplasm by the transporter pendrin, in a purportedly passive manner.^[1]
In the colloid, iodide (I^-) is oxidized to iodine (I⁰) by an enzyme called thyroid peroxidase.
Iodine (I⁰) is very reactive and iodinates the thyroglobulin at tyrosyl residues in its protein chain (in total containing approximately 120 tyrosyl residues).
In conjugation, adjacent tyrosyl residues are paired together.
The entire complex re-enters the follicular cell by endocytosis.
Proteolysis by various proteases liberates thyroxine and triiodothyronine molecules
Efflux of thyroxine and triiodothyronine from follicular cells, which appears to be largely through monocarboxylate transporter (MCT) 8 and 10,^[2]^[3] and entry into the blood.

↑ How Iodide Reaches its Site of Utilisation in the Thyroid Gland – Involvement of Solute Carrier 26A4 (Pendrin) and Solute Carrier 5A8 (Apical Iodide Transporter) - a report by Bernard A Rousset. Touch Brieflings 2007
↑ (2008). "Effective Cellular Uptake and Efflux of Thyroid Hormone by Human Monocarboxylate Transporter 10". Molecular Endocrinology 22 (6): 1357–1369. DOI:10.1210/me.2007-0112. ISSN 0888-8809.
↑ (2011). "Molecules important for thyroid hormone synthesis and action - known facts and future perspectives". Thyroid Research 4 (Suppl 1): S9. DOI:10.1186/1756-6614-4-S1-S9. ISSN 1756-6614.