Shimizu Y, Shimizu N
J Biol Chem. 1986 Jun 5;261(16):7342-6.
The rat hepatoma H35 cells in serum-free medium produce tyrosine aminotransferase (TAT) and initiate DNA synthesis and cell division upon exposure to 10(-9)-10(-10) M insulin. This insulin-dependent hormonal and mitogenic stimulation is through the insulin receptors and not through the receptors for insulin-like growth factor type I. We have isolated genetic variants of H35 cells which are resistant to a cytotoxic insulin-diphtheria toxin A fragment conjugate. These variants showed different degrees of insulin binding capacity and exhibited different sensitivities to insulin-stimulated TAT and DNA synthesis. Variant DTaI-b had a slight decrease in number of insulin receptors but completely lost sensitivity to both TAT and DNA stimulation. Variant 11-1 had a reduced number of insulin receptors but retained both TAT and DNA inducibilities. Variant 14-1, which had a high number of insulin receptors, was not responsive to DNA synthesis but was responsive to TAT induction. The beta-subunit of insulin receptors in these cell variants had different sensitivities to their insulin-dependent autophosphorylation. The rat hepatoma HTC cells used as a control showed very low insulin binding, no stimulation of TAT and DNA synthesis by insulin, and no detectable insulin-enhancement of beta-subunit phosphorylation. These characteristics provide genetic evidence for the divergence of the insulin receptor-mediated mitogenic and hormonal signals during the post-receptor pathways which is apparently regulated by the insulin-dependent phosphorylation.
无血清培养基中的大鼠肝癌H35细胞可产生酪氨酸转氨酶（TAT），并在暴露于10⁻⁹ - 10⁻¹⁰ M胰岛素后启动DNA合成和细胞分裂。这种胰岛素依赖性的激素和有丝分裂刺激是通过胰岛素受体，而不是通过I型胰岛素样生长因子受体。我们已经分离出对细胞毒性胰岛素-白喉毒素A片段偶联物具有抗性的H35细胞遗传变体。这些变体显示出不同程度的胰岛素结合能力，并对胰岛素刺激的TAT和DNA合成表现出不同的敏感性。变体DTaI-b的胰岛素受体数量略有减少，但对TAT和DNA刺激完全失去敏感性。变体11-1的胰岛素受体数量减少，但保留了TAT和DNA诱导能力。变体14-1的胰岛素受体数量较多，对DNA合成无反应，但对TAT诱导有反应。这些细胞变体中胰岛素受体的β亚基对其胰岛素依赖性自身磷酸化具有不同的敏感性。用作对照的大鼠肝癌HTC细胞显示出非常低的胰岛素结合，胰岛素对TAT和DNA合成无刺激作用，且未检测到胰岛素增强的β亚基磷酸化。这些特征为胰岛素受体介导的有丝分裂和激素信号在受体后途径中的分歧提供了遗传学证据，这显然是由胰岛素依赖性磷酸化调节的。
