The LIM Domain Protein FHL2 Interacts with the NR5A Family of Nuclear Receptors and CREB to Activate the Inhibin-α Subunit Gene in Ovarian Granulosa Cells
The LIM Domain Protein FHL2 Interacts with the NR5A Family of Nuclear Receptors and CREB to Activate the Inhibin-α Subunit Gene in Ovarian Granulosa Cells
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DOI：
10.1210/me.2011-1347
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发表时间：
2012-08-01
影响因子：
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通讯作者：
Mayo, Kelly E.
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文献类型：
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作者：
Matulis, Christina K.;Mayo, Kelly E.
核受体转录活性通过与共激活剂的相互作用而增强。高度相关的核受体 5A (NR5A) 亚家族成员肝受体同源物 1 和类固醇生成因子 1 结合并激活几个相同的基因，其中许多对生殖功能很重要。为了更好地了解这些核受体的转录激活，我们试图鉴定可能充当共激活剂的相互作用蛋白。在人卵巢 cDNA 文库的酵母双杂交筛选中，LIM 结构域蛋白四个半 LIM 结构域 2 (FHL2) 被鉴定为与 NR5A 受体相互作用。 FHL2 和密切相关的 FHL1 均在啮齿动物卵巢和颗粒细胞中表达。在原代小鼠颗粒细胞中，小干扰 RNA 介导的 FHL1 和 FHL2 敲低降低了编码抑制素-α 和 P450scc 的 NR5A 靶基因的表达。体外测定证实了 FHL 和 NR5A 蛋白之间的相互作用，并揭示 FHL2 的单个 LIM 结构域足以实现这种相互作用，而 NR5A 蛋白的配体结合结构域和 DNA 结合结构域中的决定因素很重要。 FHL2 增强肝受体同源物 1 和类固醇生成因子 1 激活颗粒细胞中抑制素-α 亚基基因启动子的能力，从而起到转录共激活剂的作用。 FHL2 还与 cAMP 反应元件结合蛋白相互作用，并通过 NR5A 受体和毛喉素的组合显着增强抑制素基因表达的激活，表明 FHL2 可能促进这两种信号的整合。总的来说，这些结果表明 FHL2 是卵巢颗粒细胞中 NR5A 核受体的新型共激活剂，并表明它参与调节对哺乳动物繁殖重要的靶基因。 （分子内分泌学26：1278-1290，2012）
Nuclear receptor transcriptional activity is enhanced by interaction with coactivators. The highly related nuclear receptor 5A (NR5A) subfamily members liver receptor homolog 1 and steroidogenic factor 1 bind to and activate several of the same genes, many of which are important for reproductive function. To better understand transcriptional activation by these nuclear receptors, we sought to identify interacting proteins that might function as coactivators. The LIM domain protein four and a half LIM domain 2 (FHL2) was identified as interacting with the NR5A receptors in a yeast two-hybrid screen of a human ovary cDNA library. FHL2, and the closely related FHL1, are both expressed in the rodent ovary and in granulosa cells. Small interfering RNA-mediated knockdown of FHL1 and FHL2 in primary mouse granulosa cells reduced expression of the NR5A target genes encoding inhibin-alpha and P450scc. In vitro assays confirmed the interaction between the FHL and NR5A proteins and revealed that a single LIM domain of FHL2 is sufficient for this interaction, whereas determinants in both the ligand binding domain and DNA binding domain of NR5A proteins are important. FHL2 enhances the ability of both liver receptor homolog 1 and steroidogenic factor 1 to activate the inhibin-alpha subunit gene promoter in granulosa cells and thus functions as a transcriptional coactivator. FHL2 also interacts with cAMP response element-binding protein and substantially augments activation of inhibin gene expression by the combination of NR5A receptors and forskolin, suggesting that FHL2 may facilitate integration of these two signals. Collectively these results identify FHL2 as a novel coactivator of NR5A nuclear receptors in ovarian granulosa cells and suggest its involvement in regulating target genes important for mammalian reproduction. (Molecular Endocrinology 26: 1278-1290, 2012)