Polychronakos C, Piscina R, Fantus I G
Protein and Polypeptide Hormone Laboratory, Royal Victoria Hospital, Montreal, Quebec, Canada.
Endocrinology. 1989 Jan;124(1):505-10. doi: 10.1210/endo-124-1-505.
Hyperplasia of the thyroid gland induced by propylthiouracil (PTU) is a well established model of rapid cell proliferation in vivo. Recent evidence indicates that tyrosine kinase activity is associated with growth factor receptors and oncogene protein products and may have an important regulatory action in the control of cell growth. Thus, we examined tyrosine kinase activity in rat thyroid membrane and cytosol preparations at rest and during PTU-induced hyperplasia. Although kinase activity was present in a crude microsomal membrane preparation, no change was observed during thyroid growth. In contrast, tyrosine kinase activity assayed with the artificial substrate poly(Glu,Na:Tyr) 4:1 was present in normal rat thyroid cytosol and increased 2- to 6-fold during the rapid phase of hyperplasia in the first 5-10 days of PTU treatment. It declined to control values by day 15, when the size and DNA content of the thyroid reached a plateau. Preincubation of the cytosolic preparations with several peptides known to bind to and activate growth factor receptor tyrosine kinases failed to enhance the activity, suggesting, along with the cytosolic localization, that the activity was distinct from these receptors. By gel filtration chromatography and polyacrylamide gel electrophoresis, tyrosine kinase activity was associated with a 55 kDa protein. Partial purification over a poly(Glu,Na:Tyr)4:1-Sepharose column, yielded a protein that appeared capable of autophosphorylation. It is suggested that this tyrosine kinase plays a role in mediating the growth-promoting effects of this model of thyroid cell hyperplasia.
丙硫氧嘧啶（PTU）诱导的甲状腺增生是一种在体内快速细胞增殖的成熟模型。最近的证据表明，酪氨酸激酶活性与生长因子受体和癌基因蛋白产物相关，并且可能在细胞生长控制中具有重要的调节作用。因此，我们检测了大鼠甲状腺在静止状态以及PTU诱导增生过程中膜和胞质溶胶制剂中的酪氨酸激酶活性。虽然在粗微粒体膜制剂中存在激酶活性，但在甲状腺生长过程中未观察到变化。相反，用人工底物聚（Glu，Na：Tyr）4:1测定的酪氨酸激酶活性存在于正常大鼠甲状腺胞质溶胶中，并且在PTU治疗的前5 - 10天增生快速期增加了2至6倍。在第15天时它下降至对照值，此时甲状腺的大小和DNA含量达到平台期。用几种已知可结合并激活生长因子受体酪氨酸激酶的肽对胞质溶胶制剂进行预温育未能增强活性，连同胞质定位一起表明，该活性与这些受体不同。通过凝胶过滤色谱法和聚丙烯酰胺凝胶电泳，酪氨酸激酶活性与一种55 kDa的蛋白质相关。在聚（Glu，Na：Tyr）4:1 - 琼脂糖柱上进行部分纯化，得到一种似乎能够自身磷酸化的蛋白质。提示这种酪氨酸激酶在介导这种甲状腺细胞增生模型的促生长作用中发挥作用。
