Nuclear localization of liver X receptor alpha and beta is differentially regulated.
Nuclear localization of liver X receptor alpha and beta is differentially regulated.
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DOI：
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发表时间：
2007
影响因子：
4
通讯作者：
K. Prüfer;J. Boudreaux
中科院分区：
文献类型：
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作者：
K. Prüfer;J. Boudreaux
核受体的活性受其核定位的调节。肝X受体(LXR)α和β是调节胆固醇代谢、胆固醇转运和脂肪生成基因转录的核受体。虽然LXRα和β在结构上非常相似，并表现出相似的配体结合特性，但它们的生理作用却截然不同。由于LXR属于一类在细胞核和细胞质之间移动的受体，因此我们进行了实验，以确定LXRα和LXRβ在核定位模式上是否存在差异。为了确定每个受体的位置，研究了稳定表达黄色荧光蛋白(YFP)与LXRα或LXRβ嵌合体的细胞系。使用荧光显微镜结合洋地黄素通透性分析来评估在有或没有配体的情况下嵌合蛋白在细胞核中的保留。令人惊讶的是，在LXRα和LXRβ之间发现了差异。未连接的LXRα保留在细胞核内，而未连接的LXRβ部分输出。然后将突变引入假定的核定位序列(NLS)，以确定哪些序列对核定位和功能重要。其中一个这样的序列的突变消除了LXRα的核定位，而LXRβ的类似变化的影响要小得多。相似的假设NLS的突变也不同地影响LXRα和LXRβ的转录激活。这些数据首次表明，LXRα和LXRβ的核保留和定位以及功能受到不同的调节。
Activity of nuclear receptors is regulated by their nuclear localization. Liver X receptors (LXR) alpha and beta are nuclear receptors that regulate transcription of genes for cholesterol metabolism, cholesterol transport, and lipogenesis. While LXR alpha and beta are very similar in structure and exhibit similar ligand binding properties, their physiological roles are quite different. Since the LXRs fall into a class of receptors that move between the nucleus and cytoplasm, experiments were conducted to determine whether LXR alpha and LXR beta show differences in their nuclear localization pattern. To determine the location of each receptor, cell lines stably expressing yellow fluorescent protein (YFP) chimeras with either LXR alpha or LXR beta were examined. Retention in the nucleus of the chimeric proteins in the presence or absence of ligands was assessed using fluorescence microscopy coupled with digitonin permeabilization assays. Surprisingly, differences were found between LXR alpha and LXR beta. Whereas unliganded LXR alpha was retained in the nucleus, unliganded LXR beta was partially exported. Mutations were then introduced into putative nuclear localization sequences (NLS) to determine which sequences are important for nuclear localization and function. Mutation in one such sequence abolished nuclear localization of LXR alpha, whereas the analogous change in LXR beta had a much less dramatic effect. Mutations in analogous putative NLS also differentially affected transcriptional activation by LXR alpha and LXR beta. These data demonstrate for the first time that nuclear retention and localization as well as function of LXR alpha and LXR beta are differentially regulated.