Cissewski K, Wolf M, Moses A C
Charles A. Dana Research Laboratories, Department of Medicine, Beth Israel Hospital, Boston, MA.
Receptor. 1992 Fall;2(3):145-53.
We have characterized the binding of 125I-IGF-I and 125I-IGF-II to plasma membranes purified from human thyroid tissue. IGF binding was time- and temperature-dependent. At 4 degrees C, maximal specific binding of 125I-IGF-I was 17.3 +/- 2.5% and of 125I-IGF-II was 8.8 +/- 2.0% (mean +/- SD/60 micrograms membrane protein). 125I-IGF-I binding was inhibited completely by unlabeled IGF-I, IGF-II, insulin, and the type-I IGF receptor monoclonal antibody, alpha IR-3. 125I-IGF-II was inhibited completely by unlabeled IGF-II and nearly completely by IGF-I. 125I-IGF-II binding also was inhibited significantly by insulin, suggesting that much or all of the IGF-II was bound to the type-I IGF receptor. Scatchard analysis revealed a single class of binding sites with a Kd of 6.0 +/- 4.2 x 10(-10) M for IGF-I binding and 5.7 +/- 1.3 x 10(-10) M for IGF-II binding. IGF-I binding was inhibited by a variety of salts in a dose-dependent manner, calcium and magnesium salts being more effective than sodium or potassium salts. Affinity crosslinking of 125I-IGF-I and -II showed clear evidence only for type-I IGF receptors. Thus, a crude plasma membrane fraction of human thyroid tissue expresses predominantly type-I IGF receptors.
我们已对从人甲状腺组织纯化的质膜上(^{125}I)-胰岛素样生长因子-I（IGF-I）和(^{125}I)-胰岛素样生长因子-II（IGF-II）的结合特性进行了表征。IGF结合具有时间和温度依赖性。在4℃时，(^{125}I)-IGF-I的最大特异性结合率为17.3±2.5%，(^{125}I)-IGF-II的最大特异性结合率为8.8±2.0%（平均值±标准差/60微克膜蛋白）。未标记的IGF-I、IGF-II、胰岛素和I型IGF受体单克隆抗体αIR-3可完全抑制(^{125}I)-IGF-I的结合。未标记的IGF-II可完全抑制(^{125}I)-IGF-II的结合，IGF-I可几乎完全抑制其结合。胰岛素也可显著抑制(^{125}I)-IGF-II的结合，这表明大部分或全部IGF-II与I型IGF受体结合。Scatchard分析显示存在一类结合位点，IGF-I结合的解离常数（Kd）为6.0±4.2×10⁻¹⁰ M，IGF-II结合的Kd为5.7±1.3×10⁻¹⁰ M。多种盐类以剂量依赖性方式抑制IGF-I的结合，钙盐和镁盐比钠盐或钾盐更有效。(^{125}I)-IGF-I和-II的亲和交联仅显示出I型IGF受体的明确证据。因此，人甲状腺组织的粗质膜部分主要表达I型IGF受体。
