Fanger B O, Viceps-Madore D, Cidlowski J A
Arch Biochem Biophys. 1984 Nov 15;235(1):141-9. doi: 10.1016/0003-9861(84)90262-5.
It is reported that receptors for epidermal growth factor (EGF) in HeLa S3 cells exist in two forms, which differ in both affinity and capacity. Both the number of receptors and their distribution into low- and high-affinity forms are modulated by glucocorticoids. Scatchard analysis of saturation binding assays performed at 0 degrees C indicates that there is a low-affinity class of receptors (Kd approximately equal to 1.5 nM), which contains approximately 6 X 10(4) binding sites per cell, and a second, high-affinity class of receptors (Kd approximately equal to 0.16 nM) containing approximately 5 X 10(3) binding sites per cell. Exposure of HeLa S3 cells to 10(-7) M dexamethasone for 24 h increased EGF binding to whole cells by increasing the numbers of low- and high-affinity receptors by 20 and 114%, respectively. The increase in EGF binding depends upon the dose of dexamethasone, being raised from 10(-11) to 10(-6) M. EGF binding is half-maximal near 2-4 X 10(-9) M, a concentration equal to the Kd of dexamethasone for the glucocorticoid receptor in these cells. The increase in EGF binding is specific for glucocorticoids, occurring when the HeLa S3 cells are exposed to 10(-7) M cortisol or dexamethasone for 24 h, but not when the cells are similarly treated with testosterone, 5 alpha-dihydroxytestosterone, 17 beta-estradiol, or progesterone. The effect on EGF binding appears to be biphasic; the initial rapid increase occurs between 8 and 12 h, is blocked by both 10(-6) M cyclohexamide and 0.1 micrograms/ml actinomycin D, and is followed by a more gradual increase thereafter. These data indicate that glucocorticoids are able to regulate both the number of EGF receptors and their distribution into high- and low-affinity components.
据报道，HeLa S3细胞中的表皮生长因子（EGF）受体存在两种形式，其亲和力和容量均有所不同。受体的数量及其向低亲和力和高亲和力形式的分布均受到糖皮质激素的调节。在0℃下进行的饱和结合试验的Scatchard分析表明，存在一类低亲和力受体（Kd约等于1.5 nM），每个细胞含有约6×10⁴个结合位点，以及第二类高亲和力受体（Kd约等于0.16 nM），每个细胞含有约5×10³个结合位点。将HeLa S3细胞暴露于10⁻⁷ M地塞米松24小时，通过分别将低亲和力和高亲和力受体的数量增加20%和114%，增加了EGF与全细胞的结合。EGF结合的增加取决于地塞米松的剂量，从10⁻¹¹ M增加到10⁻⁶ M。EGF结合在2 - 4×10⁻⁹ M附近达到最大值的一半，该浓度等于地塞米松对这些细胞中糖皮质激素受体的Kd。EGF结合的增加对糖皮质激素具有特异性，当HeLa S3细胞暴露于10⁻⁷ M皮质醇或地塞米松24小时时会发生，但当细胞用睾酮、5α-二氢睾酮、17β-雌二醇或孕酮进行类似处理时则不会。对EGF结合的影响似乎是双相的；最初的快速增加发生在8至12小时之间，被10⁻⁶ M环己酰亚胺和0.1微克/毫升放线菌素D阻断，随后是更逐渐的增加。这些数据表明，糖皮质激素能够调节EGF受体的数量及其向高亲和力和低亲和力成分的分布。
