Department of Molecular and Integrative Physiology, College of Medicine at Urbana-Champaign, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Mol Pharmacol. 2011 Mar;79(3):340-50. doi: 10.1124/mol.110.068478. Epub 2010 Nov 16.
Progesterone receptor membrane component 1 (PGRMC1) has been shown to interact with several cytochromes P450 (P450s) and to activate enzymatic activity of P450s involved in sterol biosynthesis. We analyzed the interactions of PGRMC1 with the drug-metabolizing P450s, CYP2C2, CYP2C8, and CYP3A4, in transfected cells. Based on coimmunoprecipitation assays, PGRMC1 bound efficiently to all three P450s, and binding to the catalytic cytoplasmic domain of CYP2C2 was much more efficient than to a chimera containing only the N-terminal transmembrane domain. Down-regulation of PGRMC1 expression levels in human embryonic kidney 293 and HepG2 cell lines stably expressing PGRMC1-specific small interfering RNA had no effect on the endoplasmic reticulum localization and expression levels of P450s, whereas enzymatic activities of CYP2C2, CYP2C8, and CYP3A4 were slightly higher in PGRMC1-deficient cells. Cotransfection of cells with P450s and PGRMC1 resulted in PGRMC1 concentration-dependent inhibition of the P450 activities, and this inhibition was partially reversed by increased expression of the P450 reductase (CPR). In contrast, CYP51 activity was decreased by down-regulation of PGRMC1 and expression of PGRMC1 in the PGRMC1-deficient cells increased CYP51 activity. In cells cotransfected with CPR and PGRMC1, strong binding of CPR to PGRMC1 was observed; however, in the presence of CYP2C2, interaction of PGRMC1 with CPR was significantly reduced, suggesting that CYP2C2 competes with CPR for binding to PGRMC1. These data show that in contrast to sterol synthesizing P450, PGRMC1 is not required for the activities of several drug-metabolizing P450s, and its overexpression inhibits those P450 activities. Furthermore, PGRMC1 binds to CPR, which may influence P450 activity.
孕激素受体膜成分 1（PGRMC1）已被证明与几种细胞色素 P450（P450s）相互作用，并激活固醇生物合成中涉及的 P450 酶的活性。我们分析了 PGRMC1 与代谢药物的 P450s，CYP2C2、CYP2C8 和 CYP3A4 在转染细胞中的相互作用。基于免疫共沉淀测定，PGRMC1 与所有三种 P450s 有效结合，与仅包含 N 端跨膜结构域的嵌合体相比，与 CYP2C2 的催化胞质结构域的结合效率更高。在稳定表达 PGRMC1 特异性小干扰 RNA 的人胚肾 293 和 HepG2 细胞系中下调 PGRMC1 表达水平对 P450s 的内质网定位和表达水平没有影响，而 CYP2C2、CYP2C8 和 CYP3A4 的酶活性在 PGRMC1 缺陷细胞中略高。细胞共转染 P450s 和 PGRMC1 导致 PGRMC1 浓度依赖性抑制 P450 活性，这种抑制可通过增加 P450 还原酶（CPR）的表达部分逆转。相反，PGRMC1 的下调降低了 CYP51 的活性，而 PGRMC1 在 PGRMC1 缺陷细胞中的表达增加了 CYP51 的活性。在共转染 CPR 和 PGRMC1 的细胞中，观察到 CPR 与 PGRMC1 的强结合；然而，在存在 CYP2C2 的情况下，PGRMC1 与 CPR 的相互作用明显减少，表明 CYP2C2 与 CPR 竞争结合 PGRMC1。这些数据表明，与固醇合成 P450 相反，PGRMC1 不是几种代谢药物的 P450 活性所必需的，其过表达抑制了这些 P450 活性。此外，PGRMC1 与 CPR 结合，这可能影响 P450 活性。
