Selective intranuclear redistribution of PPAR isoforms by RXRα
Selective intranuclear redistribution of PPAR isoforms by RXRα
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DOI：
10.1210/me.16.4.707
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发表时间：
2002-04-01
影响因子：
--
通讯作者：
Gonzalez, FJ
中科院分区：
文献类型：
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作者：
Akiyama, TE;Baumann, CT;Gonzalez, FJ
用荧光显微镜检测了人PPARpha(GFP-PPARhalpha)和小鼠PPARpha、β和Gamma1(分别为GFP-PPARMalpha、GFP-PPARmbeta和GFP-PPARmGamma)的转录活性绿色荧光蛋白(GFP)嵌合体在小鼠肝癌细胞系HEPA-1中的细胞内定位。在存在和不存在每个受体的特定配基的情况下，发现每个亚型的主要核型和弥漫性分布。GFP-PPARMalpha-G(包含PPARMalpha的Glu282Gly替换)和磷酸化突变体GFP-PPARmGamma-A(包含PPARmGamma的Ser82Ala替换)表现出转录活性的变化，但与它们各自的野生型受体相比，显示出相似的细胞内定位模式。核受体辅阻遏子的共表达受到抑制，而类固醇受体辅活化子-1增强了每种GFP-PPAR亚型的转录活性，但不能明显改变它们在细胞内的分布，无论有没有PPAR配体。有趣的是，PPAR的专有异二聚体伙伴RXRpha的共表达导致了GFP-PPARmGamma异构体在核内的重新分布，其特征是PPARGamma的绿色荧光标记在细胞核内呈网状分布，而不是在核仁中，并且在核仁结构和核膜上的荧光标记浓度增加。相反，黄色荧光蛋白-RXRpha和天然PPARmGamma的共表达导致了类似的黄色荧光标记的分布。这种定位模式不会被PPARGamma或RXRpha特异性配体明显改变。这些结果表明RXRpha参与了PPARGamma的核重组，并表明PPARGamma与RXRpha在核内的特定位置共定位，而不依赖于添加的配体。
The intracellular localization of transcriptionally active green fluorescent protein (GFP) chimeras linked to PPARs for human PPARalpha (GFP-PPARhalpha) and mouse PPARalpha, beta, and gamma1 (GFP-PPARmalpha, GFPPPARmbeta, and GFP-PPARmgamma, respectively) was examined in the mouse hepatoma cell line, Hepa-1, using fluorescence microscopy. A predominantly nuclear and diffuse distribution of each isoform was found in both the presence and absence of specific ligands for each receptor. GFP-PPARmalpha-G (containing a Glu282Gly substitution of PPARmalpha) and a phosphorylation mutant, GFP-PPARmgamma-A (containing a Ser82Ala substitution of PPARmgamma), exhibited altered transcriptional activities, but displayed similar intracellular localization patterns compared with their respective wild-type receptors. Coexpression of nuclear receptor corepressor suppressed, whereas steroid receptor coactivator-1 enhanced the transcriptional activity of each of the GFP-PPAR isoforms, but did not discernibly alter their intracellular distributions, both in the presence and absence of PPAR ligands. Interestingly, coexpression of the obligate heterodimeric partner of PPARs, RXRalpha, resulted in an intranuclear redistribution of the GFP-PPARmgamma isoform characterized by a reticulated pattern of the green fluorescent label for PPARgamma within the nucleus, but not in nucleoli, and a heightened concentration of the fluorescent label surrounding nucleolar structures and at the nuclear membrane. Conversely, coexpression of yellow fluorescent protein-RXRalpha and native PPARmgamma resulted in a similar distribution of the yellow fluorescent tag. This localization pattern was not discernibly altered by PPARgamma or RXRalpha-specific ligands. These results implicate RXRalpha in the nuclear reorganization of PPARgamma and suggest that PPARgamma colocalizes with RXRalpha at specific locations within the nucleus independent of added ligand.