Ritvos O, Rutanen E M, Pekonen F, Jalkanen J, Suikkari A M, Ranta T
Department I of Obstetrics and Gynecology, University Central Hospital, Helsinki, Finland.
Endocrinology. 1988 Feb;122(2):395-401. doi: 10.1210/endo-122-2-395.
Specific receptors for insulin-like growth factor I (IGF-I) on cultured human choriocarcinoma cells (JEG-3 and BeWo) were characterized. The binding of 125I-labeled recombinant (Thr59)IGF-I to the cells was reversible and time, temperature, and pH dependent. Steady state of binding occurred after 16 h at 4 C, pH 7.4. Natural human IGF-I (hIGF-I), hIGF-II, recombinant (N-Met)IGF-I, rat multiplication-stimulating activity, and insulin were 200%, 37%, 37%, 1.6%, and 0.1% as potent as (Thr59)IGF-I in inhibiting the binding of [125I]iodo-(Thr59)IGF-I to JEG-3 cells, respectively. Epidermal growth factor was ineffective. The half-maximal displacement of [125I]iodo-(Thr59)IGF-I by unlabeled (Thr59)IGF-I occurred at 11 +/- 2 ng/ml (mean +/- SEM) in both JEG-3 and BeWo cells. Scatchard analysis of the competitive binding data revealed linear plots indicating a single species of binding sites with an association constant of 0.8 X 10(9) M-1 for the binding of [125I]iodo-(Thr59)IGF-I to both cell lines. The binding capacity was 30,000 and 20,000 sites/cell for JEG-3 and BeWo cells, respectively. Chemical cross-linking of [125I]iodo-(Thr59)IGF-I to JEG-3 cells revealed two receptor complexes of 130K and 260K. Their formation was completely inhibited by an excess of unlabeled (Thr59)IGF-I or hIGF-II. Increasing amounts of insulin affected both labeled bands equally, suggesting that the 130K and 260K bands represent the monomer and dimer forms, respectively, of the ligand-binding alpha-subunit of type I IGF receptor. (Thr59)IGF-I, in a dose-dependent manner, stimulated uptake of nonmetabolizable alpha-[3H]aminoisobutyric acid by JEG-3 cells, showing that the receptor is biologically active. Our results demonstrate that choriocarcinoma cells possess functional high affinity type I IGF receptors and suggest that IGF-I is involved in the growth-regulating processes of JEG-3 and BeWo cells. These cells may provide a useful model to study the role of IGFs in trophoblast physiology.
对培养的人绒毛膜癌细胞（JEG - 3和BeWo）上胰岛素样生长因子I（IGF - I）的特异性受体进行了表征。125I标记的重组（苏氨酸59）IGF - I与细胞的结合是可逆的，且依赖于时间、温度和pH值。在4℃、pH 7.4条件下，16小时后达到结合稳态。天然人IGF - I（hIGF - I）、hIGF - II、重组（N - 甲硫氨酸）IGF - I、大鼠促有丝分裂活性因子和胰岛素在抑制[125I]碘 - （苏氨酸59）IGF - I与JEG - 3细胞结合方面的效力分别为（苏氨酸59）IGF - I的200%、37%、37%、1.6%和0.1%。表皮生长因子无效。在JEG - 3和BeWo细胞中，未标记的（苏氨酸59）IGF - I使[125I]碘 - （苏氨酸59）IGF - I半数最大位移时的浓度为11±2 ng/ml（平均值±标准误）。对竞争结合数据进行Scatchard分析，得到线性图，表明存在单一类型的结合位点，[125I]碘 - （苏氨酸59）IGF - I与两种细胞系结合的缔合常数为0.8×10^9 M^-1。JEG - 3细胞和BeWo细胞的结合容量分别为30,000和20,000个位点/细胞。[125I]碘 - （苏氨酸59）IGF - I与JEG - 3细胞的化学交联显示出130K和260K的两种受体复合物。过量未标记的（苏氨酸59）IGF - I或hIGF - II可完全抑制它们的形成。胰岛素量的增加对两条标记带的影响相同，表明130K和260K带分别代表I型IGF受体配体结合α亚基的单体和二聚体形式。（苏氨酸59）IGF - I以剂量依赖方式刺激JEG - 3细胞摄取不可代谢的α - [3H]氨基异丁酸，表明该受体具有生物学活性。我们的结果表明，绒毛膜癌细胞具有功能性高亲和力I型IGF受体，提示IGF - I参与JEG - 3和BeWo细胞的生长调节过程。这些细胞可能为研究IGF在滋养层生理学中的作用提供一个有用的模型。
