Miyamoto T, Ichikawa K, Hashizume K, Nishii Y, Takeda T, Kobayashi M, Suzuki S, Yamada T
Department of Gerontology, Endocrinology, and Metabolism, Shinshu University School of Medicine, Matsumoto-City, Japan.
Endocrinology. 1991 Aug;129(2):907-14. doi: 10.1210/endo-129-2-907.
Bernal et al. identified two proteins in rat hepatic nuclear extract, t- and n-proteins, that were enriched by thyroidectomy or T3 treatment, respectively. We purified these proteins, raised monospecific antibodies, and characterized them by Western blotting. Anti-n and anti-t-protein antibodies did not recognize t- and n-proteins, respectively. The n-protein was present in nuclear and cytosolic fractions, was present at low levels in the microsomal fraction, and was absent in the mitochondrial fraction of rat liver. The t-protein was more abundant in mitochondrial and microsomal fractions than in the nuclear fraction. The t-protein had the same molecular mass and shared immunological properties with peroxisomal enoyl-coenzyme-A (CoA) hydratase-3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme. The total cellular amount of n-protein increased 12 h after the administration of 1 microgram T3/100 g BW to thyroidectomized rats. Induction was obvious at 0.1 microgram T3/100 g BW after 24 h. Maximal induction was observed at 0.3 microgram T3/100 g BW. The n-protein was induced when thyroidectomized rat liver was perfused with 10(-7) M T3 for 6 h, excluding the possibility that the effect of T3 was mediated by an extrahepatic factor. The n-protein was detected in liver and brain, but not in kidney, heart, testis, or spleen. However, the amount of n-protein in brain was not thyroid hormone dependent. Hepatic n-protein does not correspond to any other T3-responsive protein in terms of its molecular mass and intracellular localization and may be a novel T3-responsive protein.
贝尔纳尔等人在大鼠肝核提取物中鉴定出两种蛋白质，即t蛋白和n蛋白，它们分别通过甲状腺切除术或T3处理得到富集。我们纯化了这些蛋白质，制备了单特异性抗体，并通过蛋白质印迹法对其进行了表征。抗n蛋白和抗t蛋白抗体分别不能识别t蛋白和n蛋白。n蛋白存在于核和胞质部分，在微粒体部分含量较低，在大鼠肝脏的线粒体部分不存在。t蛋白在线粒体和微粒体部分比在核部分更丰富。t蛋白具有与过氧化物酶体烯酰辅酶A（CoA）水合酶-3-羟酰基辅酶A脱氢酶双功能酶相同的分子量并具有共同的免疫特性。给甲状腺切除的大鼠注射1微克T3/100克体重后12小时，n蛋白的细胞总量增加。24小时后，在0.1微克T3/100克体重时诱导明显。在0.3微克T3/100克体重时观察到最大诱导。当用10^(-7) M T3灌注甲状腺切除的大鼠肝脏6小时时，n蛋白被诱导，排除了T3的作用由肝外因子介导的可能性。在肝脏和大脑中检测到n蛋白，但在肾脏、心脏、睾丸或脾脏中未检测到。然而，大脑中n蛋白的量不依赖于甲状腺激素。就其分子量和细胞内定位而言，肝脏n蛋白与任何其他T3反应蛋白都不对应，可能是一种新型的T3反应蛋白。
