Srivastava D, Thompson E B
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77550.
Endocrinology. 1990 Oct;127(4):1770-8. doi: 10.1210/endo-127-4-1770.
Glucocorticoids are known to have a lytic effect in leukemic cells via interactions with the glucocorticoid receptor (GR). Cortisol and various synthetic glucocorticoids bind to the GR with one-site kinetics. Cortivazol (CVZ) is a unique, high potency synthetic glucocorticoid, which has a phenylpyrazol fused to the A-ring of the steroid nucleus and displays binding consistent with two or more sites in the cytosol from CEM C7 cells (a human acute lymphoblastic T-cell line). It has previously been shown that the lower affinity class of sites are similar in affinity and site molarity to those recognized by dexamethasone. The higher affinity sites bind CVZ with 20- to 50-fold greater affinity, consistent with CVZ's enhanced biological effects. In mutant leukemic cells resistant to the lytic effects of dexamethasone, CVZ both lyses the cells and recognizes a single class of sites similar to the high affinity site in CEM C7 cells. We have carried out experiments to define the nature of the higher affinity CVZ binding site. We now show that: 1) CVZ has more than one binding site in a second, independent, B-cell line, IM-9; 2) the antiglucocorticoid RU 38486 is able to block both CVZ's higher and lower affinity sites; 3) all of CVZ's binding sites are on a protein immunologically indistinguishable from the human GR; and 4) freshly isolated clones of CVZ-resistant cells have lost all binding sites for CVZ. These data indicate that CVZ is recognizing two glucocorticoid binding sites on the human GR or a protein very similar to it.
已知糖皮质激素通过与糖皮质激素受体（GR）相互作用，对白血病细胞具有溶解作用。皮质醇和各种合成糖皮质激素以单一位点动力学与GR结合。可替唑（CVZ）是一种独特的高效合成糖皮质激素，其在甾体核的A环上融合有一个苯基吡唑，并且在来自CEM C7细胞（一种人急性淋巴细胞性T细胞系）的胞质溶胶中显示出与两个或更多位点一致的结合。先前已经表明，较低亲和力的位点在亲和力和位点摩尔浓度方面与地塞米松识别的位点相似。较高亲和力的位点以高20至50倍的亲和力结合CVZ，这与CVZ增强的生物学效应一致。在对地塞米松的溶解作用具有抗性的突变白血病细胞中，CVZ既能溶解细胞，又能识别与CEM C7细胞中的高亲和力位点相似的单一类位点。我们已经进行了实验来确定较高亲和力的CVZ结合位点的性质。我们现在表明：1）CVZ在第二个独立的B细胞系IM-9中有不止一个结合位点；2）抗糖皮质激素RU 38486能够阻断CVZ的较高和较低亲和力位点；3）CVZ的所有结合位点都在一种与人类GR在免疫学上无法区分的蛋白质上；4）新分离的CVZ抗性细胞克隆已经失去了所有CVZ结合位点。这些数据表明CVZ正在识别人类GR或与其非常相似的蛋白质上的两个糖皮质激素结合位点。
