Research on the Mechanism of thyroid hormone action

1.抗c-erb A/核T_3受体蛋白抗体的制备及核T_3受体的分析根据c-erb AcDNA序列，我们合成了一个由15个氨基酸组成的多肽，其序列与c-erb A_1、c-erb A_2和c-erb A_3高度同源，并制备了抗c-erb A的抗体。我们研究了NT_3R与抗c-erb A抗体的相互作用，得到以下结果。(1)该抗体与大鼠肝、肾、脑和人肾制备的NT_3R免疫沉淀相似。(2)该抗体以竞争性方式特异性抑制T_3与NT_3R的结合。它降低了T3结合结合常数的值呈剂量依赖性，而最大结合能力不受影响。(3)该抗体对T_3与大鼠肝胞浆结合蛋白或人血清TBG的结合无影响，提示这些蛋白T_3结合区的蛋白构象可能与NT_3R不同。(4)免疫吸附实验表明，反向T_3结合蛋白与NT_3R不同。（5）抗体免疫沉淀c-erb A_1和c-erb A_2的体外转录/翻译产物。甲状腺细胞核T_3受体的研究：我们发现猪甲状腺细胞和培养的大鼠甲状腺细胞系FRTL-5细胞核内存在T_3受体蛋白，TSH可显著降低FRTL-5细胞核内NT_3R水平。这一结果可能提示下丘脑-垂体-甲状腺轴存在另一个通过调节激素受体水平的控制系统。

1. Production of an antibody against c-erb A/nuclear T_3 receptor proteins and analysis of nuclear T_3 receptorsIt has been reported that c-erb A encodes nuclear T_3 receptors (NT_3R). Based on the sequence of c-erb A cDNA, we synthesized a polypeptide consisting of 15 amino acids, the sequence of which has high homology between c-erb A _1, and , and raised an anti c-erb A antibody. We have studied the interaction between NT_3R and the anti c-erb A antibody and obtained the following results.(1) The antibody immunoprecipitated NT_3R prepared from rat liver, kidney, brain and human kidney similarly.(2) The antibody specifically inhibited T_3-binding to NT_3R in a competitive manner. It decreased the value for T3-binding association constant dose dependently, while maximal binding capacity was not influenced.(3) No effect of the antibody was detected on T_3-binding to rat liver cytosolic binding proteins or human serum TBG, suggesting that the protein conformation of the T_3-binding region of these proteins might be different from that of NT_3R.(4) The immunoabsorption study revealed that reverse T_3 binding protein was not the same as NT_3R.(5)The antibody immunoprecipitated the in vitro transcription/translation products of c-erb A _1 and .2. Nuclear T_3 receptors in thyroid cells.We have found that nuclear T_3 receptor proteins exist in porcine thyroid cells and cultured rat thyroid cell line, FRTL-5 cells, and that TSH significantly decreases NT_3R level in FRTL-5 cells. The results may suggest the existence of another control system of the hypothalamic-pituitary-thyroid axis via modulation of the hormone receptor levels.