Strack V, Bossenmaier B, Stoyanov B, Mushack J, Häring H U
Eberhard-Karls-Universität Tübingen, Innere Medizin IV, Germany.
Diabetologia. 1997 Oct;40(10):1135-40. doi: 10.1007/s001250050798.
A population-based study in the Netherlands has recently demonstrated that a mutation of the human insulin receptor (HIR-973 valine to methionine) is associated with hyperglycaemia and an increased prevalence of non-insulin-dependent diabetes mellitus (NIDDM). The aim of the present study was to assess whether this mutation leads to a functional alteration of the insulin receptor. We prepared the HIR-973 mutant by in vitro mutagenesis. This mutant was transiently overexpressed in HEK 293 cells either alone or together with insulin-receptor substrate-1 (IRS-1) or Shc. Insulin stimulated autophosphorylation, phosphorylation of the substrates IRS-1 and Shc as well as activation of phosphatidylinositol-3 (PI3)-kinase were studied. Autophosphorylation of HIR-973 and its susceptibility to hyperglycaemia induced inhibition was not different from HIR-wt. Human insulin receptor with a juxtamembrane deletion HIR-deltaJM which is known to impair HIR/IRS-1 interaction was used as control. While the HIR-deltaJM induces a reduced IRS-1 phosphorylation HIR-973 showed even a slightly increased ability to phosphorylate IRS-1 (n = 7, 115% of control, p < 0.01). Shc phosphorylation was only mediated by HIR-wt and HIR-973 but not by HIR-deltaJM. Again a tendency to higher phosphorylation of Shc was seen with HIR-973 (n = 7, 109% of control, NS). When PI3-kinase activity was measured in IRS-1 precipitates similar activity was found for HIR-wt and HIR-973 whereas PI3-kinase stimulation was reduced with HIR-deltaJM. In summary, the data suggest that HIR-973 does not impair the first steps of the insulin signalling cascade. It is therefore unlikely that this mutation may cause cellular insulin resistance. The close vicinity of this mutation to insulin receptor domains which are involved in IRS-1 and Shc binding may, however, alter the interaction of the insulin receptor with these substrates. This could explain the slightly increased insulin effect on tyrosine phosphorylation of these docking proteins. These characteristics of HIR-973 might have a compensatory function of impaired signal transduction further downstream of the signalling chain in this specific subgroup of NIDDM patients.
荷兰一项基于人群的研究最近表明，人类胰岛素受体的一种突变（HIR - 973缬氨酸突变为甲硫氨酸）与高血糖症以及非胰岛素依赖型糖尿病（NIDDM）患病率增加有关。本研究的目的是评估这种突变是否会导致胰岛素受体功能改变。我们通过体外诱变制备了HIR - 973突变体。该突变体在HEK 293细胞中单独或与胰岛素受体底物 - 1（IRS - 1）或Shc一起瞬时过表达。研究了胰岛素刺激的自身磷酸化、底物IRS - 1和Shc的磷酸化以及磷脂酰肌醇 - 3（PI3）激酶的激活情况。HIR - 973的自身磷酸化及其对高血糖诱导抑制的敏感性与野生型HIR无差异。已知会损害HIR/IRS - 1相互作用的具有近膜缺失的人类胰岛素受体HIR - deltaJM用作对照。虽然HIR - deltaJM导致IRS - 1磷酸化减少，但HIR - 973显示出磷酸化IRS - 1的能力甚至略有增加（n = 7，为对照的115%，p < 0.01）。Shc磷酸化仅由野生型HIR和HIR - 973介导，而非HIR - deltaJM。同样，HIR - 973的Shc磷酸化也有升高趋势（n = 7，为对照的109%，无显著性差异）。当在IRS - 1沉淀物中测量PI3激酶活性时，野生型HIR和HIR - 973的活性相似，而HIR - deltaJM的PI3激酶刺激作用降低。总之，数据表明HIR - 973不会损害胰岛素信号级联反应的第一步。因此，这种突变不太可能导致细胞胰岛素抵抗。然而，该突变与参与IRS - 1和Shc结合的胰岛素受体结构域非常接近，可能会改变胰岛素受体与这些底物的相互作用。这可以解释胰岛素对这些对接蛋白酪氨酸磷酸化的作用略有增加。在这个特定亚组的NIDDM患者中，HIR - 973的这些特征可能对信号传导链下游受损的信号转导具有补偿功能。
