Thyroid hormone transport by the human monocarboxylate transporter 8 and its rate-limiting role in intracellular metabolism
Thyroid hormone transport by the human monocarboxylate transporter 8 and its rate-limiting role in intracellular metabolism
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DOI：
10.1210/me.2005-0256
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发表时间：
2006-11-01
影响因子：
--
通讯作者：
Kester, Monique H. A.
中科院分区：
文献类型：
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作者：
Friesema, Edith C. H.;Kuiper, George G. J. M.;Kester, Monique H. A.
甲状腺激素的细胞进入是由质膜转运蛋白介导的。我们已经确定大鼠单羧酸转运蛋白8(MCT8)是一种活性和特异性的甲状腺激素转运蛋白。MCT8基因位于X染色体上。在患有严重精神运动发育迟缓和血清T-3水平升高的男性中发现MCT8基因的半合子突变，证明了该基因的生理学相关性。我们通过分析瞬时单独或与编码碘甲状腺原氨酸脱碘酶D1、D2或D3的hMCT8基因一起瞬时转染人(H)MCT8基因的细胞系对碘甲腺原氨酸的摄取和代谢来表征人(H)MCT8。RT-PCR在许多人细胞系和COS1细胞中检测到MCT8mRNA，但在包括JEG3细胞在内的其他细胞系中检测不到MCT8mRNA。用多克隆抗体HMCT8免疫印迹法检测未转染细胞系中未检测到MCT8蛋白，但在预期大小(61 KDa)的转染细胞中检测到MCT8蛋白。转染hMCT8基因的COS1和JEG3细胞对T-3和T-4的摄取增加了2~3倍，而对RT(3)或3，3‘-二碘甲状腺原氨酸(3，3’-T-2)的摄取几乎或没有增加。共转染D2或D3后，MCT8表达显著增加T-4代谢，D3代谢T-3，D1或D2共转导RT(3)，D3共转导3，3‘-T-2。将完整的转基因细胞与N-溴乙酰-[I-125]T-3孵育后，观察hMCT8蛋白的亲和标记。HMCT8也促进了溴乙酰-T-3共转染d1的亲和标记。我们的发现表明，hMCT8介导了碘甲状腺原氨酸的质膜转运，从而增加了它们在细胞内的利用率。
Cellular entry of thyroid hormone is mediated by plasma membrane transporters. We have identified rat monocarboxylate transporter 8 (MCT8) as an active and specific thyroid hormone transporter. The MCT8 gene is located on the X-chromosome. The physiological relevance of MCT8 has been demonstrated by the identification of hemizygous mutations in this gene in males with severe psychomotor retardation and elevated serum T-3 levels. We have characterized human (h) MCT8 by analysis of iodothyronine uptake and metabolism in cell lines transiently transfected with hMCT8 cDNA alone or together with cDNA coding for iodothyronine deiodinase D1, D2, or D3. MCT8 mRNA was detected by RT-PCR in a number of human cell lines as well as in COS1 cells but was low to undetectable in other cell lines, including JEG3 cells. MCT8 protein was not detected in nontransfected cell lines tested by immunoblotting using a polyclonal C-terminal hMCT8 antibody but was detectable in transfected cells at the expected size (61 kDa). Transfection of COS1 and JEG3 cells with hMCT8 cDNA resulted in 2- to 3-fold increases in uptake of T-3 and T-4 but little or no increase in rT(3) or 3,3 '-diiodothyronine (3,3 '-T-2) uptake. MCT8 expression produced large increases in T-4 metabolism by cotransfected D2 or D3, T-3 metabolism by D3, rT(3) metabolism by D1 or D2, and 3,3 '-T-2 metabolism by D3. Affinity labeling of hMCT8 protein was observed after incubation of intact transfected cells with N-bromoacetyl-[I-125]T-3. hMCT8 also facilitated affinity labeling of cotransfected D1 by bromoacetyl-T-3. Our findings indicate that hMCT8 mediates plasma membrane transport of iodothyronines, thus increasing their intracellular availability.