Division of Basic Medical Sciences, Mercer University School of Medicine, 1550 College St, Macon, GA 31207, USA. Thomas
J Steroid Biochem Mol Biol. 2011 May;125(1-2):57-65. doi: 10.1016/j.jsbmb.2010.08.003. Epub 2010 Aug 22.
Human 3β-hydroxysteroid dehydrogenase/isomerase type 1 (3β-HSD1) is a critical enzyme in the conversion of DHEA to estradiol in breast tumors and may be a target enzyme for inhibition in the treatment of breast cancer in postmenopausal women. Human 3β-HSD2 participates in the production of cortisol and aldosterone in the human adrenal gland in this population. In our recombinant human breast tumor MCF-7 Tet-off cells that express either 3β-HSD1 or 3β-HSD2, trilostane and epostane inhibit the DHEA-induced proliferation of MCF-7 3β-HSD1 cells with 12-16-fold lower IC(50) values compared to the MCF-7 3β-HSD2 cells. Trilostane and epostane also competitively inhibit purified human 3β-HSD1 with 12-16-fold lower K(i) values compared to the noncompetitive K(i) values measured for human 3β-HSD2. Using our structural model of 3β-HSD1, trilostane was docked in the active site of 3β-HSD1, and Arg195 in 3β-HSD1 or Pro195 in 3β-HSD2 was identified as a potentially critical residue. The R195P-1 mutant of 3β-HSD1 and the P195R-2 mutant of 3β-HSD2 were created, expressed and purified. Kinetic analyses of enzyme inhibition suggest that the high-affinity, competitive inhibition of 3β-HSD1 by trilostane may be related to the presence of Arg195 in 3β-HSD1 versus Pro195 in 3β-HSD2. In addition, His156 in 3β-HSD1 may play a role in the higher affinity of 3β-HSD1 for substrates and inhibitors compared to 3β-HSD2 containing Try156. Structural modeling of the 3β-HSD1 dimer identified a possible interaction between His156 on one subunit and Gln105 on the other. Kinetic analyses of the H156Y-1, Q105M-1 and Q105M-2 support subunit interactions that contribute to the higher affinity of 3β-HSD1 for the inhibitor, epostane, compared to 3β-HSD2. Article from the Special issue on Targeted Inhibitors.
人 3β-羟甾脱氢酶/异构酶 1 型(3β-HSD1)是在乳腺癌肿瘤中将 DHEA 转化为雌二醇的关键酶,并且可能是绝经后妇女治疗乳腺癌的抑制靶酶。人 3β-HSD2 参与人群中肾上腺皮质醇和醛固酮的产生。在我们表达 3β-HSD1 或 3β-HSD2 的重组人乳腺癌 MCF-7 Tet-off 细胞中,与 MCF-7 3β-HSD2 细胞相比,三氯司坦和依普利酮以 12-16 倍的低 IC50 值抑制 DHEA 诱导的 MCF-7 3β-HSD1 细胞增殖。三氯司坦和依普利酮也竞争性地抑制纯化的人 3β-HSD1,其 K(i) 值比测量的非竞争性 K(i) 值低 12-16 倍人 3β-HSD2。使用我们的 3β-HSD1 结构模型,将三氯司坦对接在 3β-HSD1 的活性部位,鉴定出 3β-HSD1 中的 Arg195 或 3β-HSD2 中的 Pro195 为潜在关键残基。创建、表达和纯化了 3β-HSD1 的 R195P-1 突变体和 3β-HSD2 的 P195R-2 突变体。酶抑制的动力学分析表明,三氯司坦对 3β-HSD1 的高亲和力、竞争性抑制可能与 3β-HSD1 中的 Arg195 与 3β-HSD2 中的 Pro195 有关。此外,3β-HSD1 中的 His156 可能在 3β-HSD1 对底物和抑制剂的更高亲和力中起作用,而不是含有 Try156 的 3β-HSD2。3β-HSD1 二聚体的结构建模确定了一个可能的相互作用,其中一个亚基上的 His156 与另一个亚基上的 Gln105 相互作用。H156Y-1、Q105M-1 和 Q105M-2 的动力学分析支持亚基相互作用,这有助于 3β-HSD1 对抑制剂依普利酮的亲和力高于 3β-HSD2。来自靶向抑制剂特刊的文章。