Thyrotropic activity of recombinant human glycoprotein hormone analogs and pituitary mammalian gonadotropins in goldfish (Carassius auratus): Insights into the evolution of thyrotropin receptor specificity

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• 作者：T.C. Miller^a ; ^{millertc@mail.nih.gov} ; J.T. Jaques^b ; ^{j-jaques@tvmdl.tamu.edu} ; M.W. Szkudlinski^c ; ^{mszkudlinski@trophogen.com} ; D.S. MacKenzie^a ; ^{duncan@bio.tamu.edu}
• 关键词：TSH ; thyrotropin ; TSH-R ; thyrotropin receptor ; T4 ; thyroxine ; GTH ; gonadotropin ; GSU伪 ; glycoprotein hormone subunit 伪 ; LH ; luteinizing hormone ; FSH ; follicle stimulating hormone ; hCG ; human chorionic gonadotropin
• 刊名：General and Comparative Endocrinology
• 出版年：2012
• 期刊代码：169_00166480
• 类别：bio
• 出版时间：15 May, 2012
• 卷：177
• 期：1
• 页码：70-75
• 文件大小：524 K

摘要

Thyrotropin (TSH) is a pituitary glycoprotein hormone heterodimer that binds to its G-protein coupled receptor (TSH-R) at the thyroid to promote the synthesis and secretion of thyroid hormone. Very little is known about TSH-TSH-R interactions in teleost fish. Mammalian gonadotropins have been reported to have an intrinsic ability to activate teleost fish TSH-Rs, suggesting the TSH-R in teleost fish is more promiscuous than in other vertebrates. In this study we utilized the goldfish T₄-release response and recombinant human TSH analogs as in vivo tools to evaluate the structural constraints on hormone-receptor interactions. We found that four positively charged lysines substituted for neutral or negatively charged amino acids within positions 11-20 of the glycoprotein hormone subunit 伪 (GSU伪) significantly increased biological activity of hTSH in fish, as it does in mammals. We further found that bovine follicle stimulating hormone but not luteinizing hormone, whose GSU伪 subunits also contain four lysine or arginine amino acid residues in the N-terminal portion of GSU伪, was thyrotropic in goldfish, suggesting gonadotropin 尾 subunit contributes to the heterothyrotropic activity. Though recombinant human FSH did not produce a dose-dependent increase in T₄, thyrotropic activity could be acquired with the addition of positively charged amino acids at the N-terminal portion of its GSU伪, confirming the importance of the charge on those amino acids for activation of the goldfish TSH-R. These studies demonstrate that mammalian glycoprotein hormone analogs can be utilized to evaluate the conservation of receptor binding and activation mechanisms between fish and mammals.