Block N E, Komori K, Dutton S L, Robinson K A, Buse M G
Department of Medicine, Medical University of South Carolina, Charleston 29425.
Diabetes. 1991 Dec;40(12):1691-700. doi: 10.2337/diab.40.12.1691.
Insulin receptor tyrosine kinase activity solubilized from hind limb muscle of control and streptozocin-induced diabetic (STZ-D) rats (2-3 wk) was studied with the substrates histone H2B and poly glutamic acid-tyrosine (glu-tyr) (4:1). Basal and insulin-stimulated kinase activities were inhibited when high concentrations of either substrate were added before initiation of phosphorylation with ATP. Under these conditions, insulin-stimulated activities of diabetic- and control-derived receptor kinase toward H2B were similar at 0.008 mg/ml H2B. However, higher concentrations of H2B (0.04-1 mg/ml) progressively reduced the ratios of diabetic-derived to control-derived receptor kinase activities to approximately 0.5. When inhibition of receptor kinase activities was prevented by allowing maximal autophosphorylation of insulin receptors before addition of H2B, kinase activity of diabetic- and control-derived receptors was similar at all H2B concentrations. Diabetic-derived insulin-receptor tyrosine kinase activity toward poly glu-tyr (4:1) was not significantly different from that of control rats. Under conditions of substrate inhibition (0.4 mg/ml H2B), insulin receptor H2B kinase activity from muscles of rats with severe diabetes (85 mg/kg STZ, 7 days) was significantly decreased, whereas the same activity from rats with moderate diabetes (50 mg/kg STZ, 7 days) was not significantly different from control rats. Insulin receptor alpha,beta dimers were not detectable in muscle preparations from control or diabetic rats. The data suggest that the impairment of muscle-derived insulin-receptor tyrosine kinase activity associated with insulinopenic diabetes reflects, in part, enhanced inhibition by some substrates. If solubilized insulin receptors and the exogenous substrates studied model in vivo events, impaired signaling of the muscle insulin receptor in insulinopenic diabetes may depend on the type and concentration of intracellular tyrosine kinase substrates and the severity of the metabolic derangements.
以组蛋白H2B和聚谷氨酸 - 酪氨酸（glu - tyr）（4:1）为底物，研究了从对照大鼠和链脲佐菌素诱导的糖尿病（STZ - D）大鼠（2 - 3周）后肢肌肉中溶解的胰岛素受体酪氨酸激酶活性。在用ATP启动磷酸化之前添加高浓度的任何一种底物时，基础和胰岛素刺激的激酶活性均受到抑制。在这些条件下，在0.008 mg/ml H2B时，糖尿病大鼠和对照大鼠来源的受体激酶对H2B的胰岛素刺激活性相似。然而，更高浓度的H2B（0.04 - 1 mg/ml）逐渐将糖尿病大鼠来源与对照大鼠来源的受体激酶活性之比降低至约0.5。当通过在添加H2B之前使胰岛素受体进行最大程度的自身磷酸化来防止受体激酶活性受到抑制时，在所有H2B浓度下，糖尿病大鼠和对照大鼠来源的受体激酶活性相似。糖尿病大鼠来源的胰岛素受体对聚谷氨酸 - 酪氨酸（4:1）的酪氨酸激酶活性与对照大鼠无显著差异。在底物抑制条件下（0.4 mg/ml H2B），重度糖尿病大鼠（85 mg/kg链脲佐菌素，7天）肌肉中的胰岛素受体H2B激酶活性显著降低，而中度糖尿病大鼠（50 mg/kg链脲佐菌素，7天）的相同活性与对照大鼠无显著差异。在对照或糖尿病大鼠的肌肉制剂中未检测到胰岛素受体α、β二聚体。数据表明，与胰岛素缺乏性糖尿病相关的肌肉来源的胰岛素受体酪氨酸激酶活性受损部分反映了某些底物抑制作用的增强。如果溶解的胰岛素受体和所研究的外源性底物模拟体内事件，胰岛素缺乏性糖尿病中肌肉胰岛素受体的信号传导受损可能取决于细胞内酪氨酸激酶底物的类型和浓度以及代谢紊乱的严重程度。
