Modulation of insulinlike growth factor I binding to human fibroblast monolayer cultures by insulinlike growth factor carrier proteins released to the incubation media.
Modulation of insulinlike growth factor I binding to human fibroblast monolayer cultures by insulinlike growth factor carrier proteins released to the incubation media.
复制标题
通过释放到培养介质中的胰岛素样生长因子载体蛋白调节胰岛素样生长因子 I 与人成纤维细胞单层培养物的结合。
DOI：
10.1172/jci112343
复制
发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Rechler,MM
中科院分区：
文献类型：
--
作者：
DeVroede,MA;Tseng,LY;Katsoyannis,PG;Nissley,SP;Rechler,MM
I 型和 II 型胰岛素样生长因子 (IGF) 受体和 IGF 载体蛋白对 IGF-I 示踪剂与培养的人成纤维细胞结合的相对贡献是在竞争性结合实验中确定的，该实验使用未标记的胰岛素和含有胰岛素 A 链和 IGF-I B 结构域的合成胰岛素-IGF-I 杂合分子。胰岛素仅与 I 型 IGF 受体结合，而 B-IGF-I 杂合体则与 I 型受体和 IGF 载体蛋白结合，但不与 II 型受体结合。在悬浮的人成纤维细胞中，IGF-I 示踪剂主要与 I 型 IGF 受体结合（IGF-I 的抑制作用远大于胰岛素，大于 B-IGF-I 杂合分子）。相比之下，在成纤维细胞单层中，IGF-I 结合受到胰岛素或杂合分子的最小程度抑制，表明主要与 II 型 IGF 受体结合。 I型受体似乎被掩盖在成纤维细胞单层上，并且需要细胞的悬浮液或去污剂溶解才能被证明。在单层结合实验过程中，我们注意到低浓度的未标记 IGF-I (5-10 ng/ml) 或 B-IGF-I 杂合体 (100 ng/ml) 反而使 IGF-I 示踪剂结合增加至两倍。我们假设在结合孵育期间（5 小时，15 摄氏度），IGF-I 示踪剂在细胞表面上的结合位点和释放到孵育介质中的 IGF 载体蛋白之间分配。未标记的配体优先占据介质中的结合位点，增加了可与细胞结合的示踪剂。为了支持这一假设，在与成纤维细胞单层结合孵育结束时在培养基中证实了载体蛋白，并且培养基中不饱和结合位点的浓度与示踪剂与细胞的结合呈反比相关。因此，在结合孵育过程中释放到培养基中的载体蛋白调节IGF-I示踪剂与细胞受体的结合，表明载体蛋白可能在调节细胞对IGF的反应性中发挥重要作用。
The relative contributions of type I and type II insulinlike growth factor (IGF) receptors and IGF carrier proteins to the binding of IGF-I tracer to cultured human fibroblasts were determined in competitive binding experiments that used unlabeled insulin and synthetic insulin-IGF-I hybrid molecules containing the A chain of insulin and the B domain of IGF-I. Whereas insulin binds only to type I IGF receptors, the B-IGF-I hybrids bind to type I receptors and IGF carrier proteins but not to type II receptors. In suspended human fibroblasts, IGF-I tracer binds predominantly to type I IGF receptors (inhibition by IGF-I much greater than insulin greater than B-IGF-I hybrid molecules). By contrast, in fibroblast monolayers, IGF-I binding was minimally inhibited by insulin or hybrid molecules, suggesting predominant binding to the type II IGF receptor. The type I receptor appears to be masked on fibroblast monolayers, and to require suspension or detergent solubilization of the cells to be demonstrated. In the course of the monolayers binding experiments, we noted that low concentrations of unlabeled IGF-I (5-10 ng/ml) or B-IGF-I hybrids (100 ng/ml) paradoxically increased IGF-I tracer binding up to twofold. We postulated that during the binding incubation (5 h, 15 degrees C), IGF-I tracer partitioned between binding sites on the cell surface and IGF carrier proteins released to the incubation media. Preferential occupancy of binding sites in the media by unlabeled ligand increased the tracer available to bind to the cells. In support of this hypothesis, carrier proteins were demonstrated in the media at the end of the binding incubation with fibroblast monolayers, and the concentration of unsaturated binding sites in the media correlated inversely with tracer binding to the cells. Thus carrier proteins released to the media during the binding incubation modulate the binding of IGF-I tracer to cell receptors, suggesting that the carrier proteins may play an important role in regulating cellular responsiveness to the IGFs.