Soprano D R, Herbert J, Soprano K J, Schon E A, Goodman D S
J Biol Chem. 1985 Sep 25;260(21):11793-8.
Studies were conducted to ascertain if transthyretin mRNA was present in extrahepatic tissues of the rat. A trnasthyretin cDNA clone was isolated from a lambda gt11 human liver cDNA library by antibody screening and its identity was confirmed by nucleotide sequence analysis. This transthyretin cDNA clone was used to survey poly(A+) RNA isolated from 12 different rat tissues for transthyretin mRNA by Northern blot analysis. The liver contained the highest level of transthyretin mRNA and this level was not altered by the vitamin A status of the rat. A significant amount of transthyretin mRNA was found in the brain (30% of the level of the liver) which was localized in specific regions of the brain. In addition, detectable levels of transthyretin mRNA (1% to 2% of that of the liver) were observed in the stomach, heart, skeletal muscle, and spleen. Translation of brain poly(A+) RNA in rabbit reticulocyte lysates and immunoprecipitation of the translation products with anti-transthyretin antiserum resulted in a protein band of the same size as liver pre-transthyretin. Liver pre-transthyretin was processed by the cotranslational addition of dog pancreas microsomal membranes to a protein that migrated coincidentally with monomeric serum transthyretin. These data suggest that transthyretin in the brain and the cerebrospinal fluid results from de novo synthesis and that transthyretin may play a significant physiological function, as yet unknown, within the nervous system.
开展了多项研究以确定转甲状腺素蛋白mRNA是否存在于大鼠的肝外组织中。通过抗体筛选从λgt11人肝脏cDNA文库中分离出一个转甲状腺素蛋白cDNA克隆，并通过核苷酸序列分析确认其身份。利用该转甲状腺素蛋白cDNA克隆，通过Northern印迹分析检测从12种不同大鼠组织中分离的聚腺苷酸加尾（poly(A+)）RNA中的转甲状腺素蛋白mRNA。肝脏中转甲状腺素蛋白mRNA水平最高，且该水平不受大鼠维生素A状态的影响。在脑中发现了大量转甲状腺素蛋白mRNA（为肝脏水平的30%），其定位于脑的特定区域。此外，在胃、心脏、骨骼肌和脾脏中观察到可检测水平的转甲状腺素蛋白mRNA（为肝脏水平的1%至2%）。用兔网织红细胞裂解物翻译脑poly(A+)RNA，并用抗转甲状腺素蛋白抗血清对翻译产物进行免疫沉淀，得到一条与肝脏前转甲状腺素蛋白大小相同的蛋白带。通过共翻译添加犬胰腺微粒体膜，肝脏前转甲状腺素蛋白被加工成一种与单体血清转甲状腺素蛋白迁移一致的蛋白质。这些数据表明，脑和脑脊液中的转甲状腺素蛋白是从头合成的结果，并且转甲状腺素蛋白可能在神经系统中发挥一种尚未知晓的重要生理功能。
