Molecular description of non-autoimmune hyperthyroidism at a neonate caused by a new thyrotropin receptor germline mutation
Molecular description of non-autoimmune hyperthyroidism at a neonate caused by a new thyrotropin receptor germline mutation
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DOI：
10.1186/1756-6614-4-s1-s8
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发表时间：
2011-01-01
期刊：
影响因子：
2.2
通讯作者：
Kleinau, Gunnar
中科院分区：
文献类型：
--
作者：
Biebermann, Heike;Winkler, Franziska;Kleinau, Gunnar
背景：促甲状腺激素受体（TSHR）基因组成性激活的种系突变可导致非自身免疫性甲状腺功能亢进，并可作为显性性状传播或零星发生。这些突变大多位于g蛋白偶联受体的蛇形部分。方法：对1例2月龄患者促甲状腺激素受体基因外显子9和10进行测序，发现瞬时转染COS-7细胞后出现功能特征突变。通过ELISA方法研究了细胞表面定位，通过α筛选技术测量了g /腺苷酸环化酶激活的cAMP，并使用报告基因法测定了Gq/11磷脂酶C-b的激活。结果：我们在TSHR基因的第一个细胞外环检测到一个杂合突变，导致异亮氨酸残基在486 （I486N）氨基酸位置交换为天冬酰胺。细胞表面定位降低到野生型TSHR的51%。突变受体的功能表征显示Gs/腺苷酸环化酶途径具有组成性激活，而Gq/11途径的基础活性与野生型相当。牛tsh诱导的cAMP积累略有减少，但IP3信号通路受损。结论：我们在一名非自身免疫性散发性甲状腺功能亢进新生儿中发现了一种新的TSHR种系突变（I486N）。该突变位于细胞外环1，并表现出基础cAMP积累的增加，但意外地损害了TSH诱导的Gq介导的信号传导能力。TSHR同源模型表明，异亮氨酸486是通过进一步激活敏感的细胞外部分相互作用诱导信号转导的潜在关键参与者。
Background: Constitutively activating germline mutations in the thyrotropin receptor (TSHR) gene result in nonautoimmune hyperthyroidism and can be transmitted as a dominant trait or occur sporadically. These mutations are mostly located in the serpentine part of this G-protein coupled receptor.Methods: Sequencing exon 9 and 10 of the thyrotropin receptor gene in a two months old patient identified a mutation which was functionally characterized after transient transfection into COS-7 cells. Cell surface localization was investigated by an ELISA approach and for signalling properties we measured cAMP by alpha screen technology for Gs/adenylyl cyclase activation and use a reporter gene assay for determination of Gq/11 phospholipase C-b activation.Results: We detected a heterozygous mutation in the first extracellular loop of the TSHR gene leading to an exchange of an isoleucine residue for asparagine at amino acid position 486 (I486N). Cell surface localization was reduced to 51% of wild-type TSHR. Functional characterization of the mutant receptor revealed constitutive activation of the Gs/adenylyl cyclase pathway, in contrast basal activity of the Gq/11 pathway was comparable to the wild-type. The bovine TSH-induced cAMP accumulation was slightly reduced, but IP3 signaling was impaired.Conclusion: We identified a new TSHR germline mutation (I486N) in a neonate with non-autoimmune sporadic hyperthyroidism. The mutation is located at the extracellular loop 1 and exhibits an increase in basal cAMP accumulation, but unexpectedly impairs the capability for TSH induced Gq mediated signaling. The TSHR homology model suggests isoleucine 486 as a potential key-player for induction of signal transduction by an interplay with further activation sensitive extracellular parts.