Regulation of the transcriptional activity of the peroxisome proliferator-activated receptor α by phosphorylation of a dependent trans-activating domain
Regulation of the transcriptional activity of the peroxisome proliferator-activated receptor α by phosphorylation of a dependent trans-activating domain
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DOI：
10.1074/jbc.274.15.10505
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发表时间：
1999-04-09
影响因子：
4.8
通讯作者：
Meier, CA
中科院分区：
文献类型：
--
作者：
Juge-Aubry, CE;Hammar, E;Meier, CA
过氧化物酶体增殖物激活受体(PPAR)是由脂肪酸和二十烷基类化合物激活的核受体的一个亚类，此外，它们还可以被胰岛素磷酸化，导致PPARα的激活，同时在一定条件下抑制PPARγ。然而，到目前为止，胰岛素对PPARα的刺激作用是否是直接的，以及它是通过什么机制发生的，目前还不清楚。我们现在证明了hPPARα的1-92位氨基酸包含一个激活功能(AF)-1结构域，该结构域可通过涉及丝裂原激活蛋白激酶P42和P44的途径被胰岛素进一步激活。进一步分析PPARα的氨基末端区域发现，胰岛素诱导的反式激活是通过12和21位的两个丝裂原激活蛋白激酶位点的磷酸化而发生的，这两个位点在进化过程中都是保守的。PPARα中有一个强大的AF-1区域，刺激转录的强度是病毒蛋白VP16的四分之一，这一特征与该异构体在转染实验中显著的基础转录活性是一致的。然而，有趣的是，这个AF-1区域的活性受到两个丝氨酸残基的磷酸化的调节，这两个残基都必须被磷酸化才能激活转录。这与PPAR Gamma 2相反，PPAR Gamma 2以前被证明在一个基序中的单个位点被磷酸化，而该基序与现在PPARα中描述的位点不是同源的。尽管依赖磷酸化增强PPARα转录活性的分子细节仍未阐明，但我们证明了胰岛素对PPARαAF-1区域的影响可以通过添加三碘甲腺原氨酸受体β1来模拟，三碘甲腺原氨酸受体β1是辅阻遏物蛋白的强结合蛋白。此外，缺乏与辅阻遏子相互作用的三碘甲腺原氨酸受体β1突变体不能激活PPARα，这些观察表明PPARα的AF-1区域部分被辅阻遏子蛋白沉默，这可能是以磷酸化依赖的方式相互作用的。
The peroxisome proliferator-activated receptors (PPARs) are a subgroup of nuclear receptors activated by fatty acids and eicosanoids, In addition, they are subject to phosphorylation by insulin, resulting in the activation of PPAR alpha, while inhibiting PPAR gamma under certain conditions. However, it was hitherto unclear whether the stimulatory effect of insulin on PPAR alpha was direct and by which mechanism it occurs. We now demonstrate that amino acids 1-92 of hPPAR alpha contain an activation function (AF)-1-like domain, which is further activated by insulin through a pathway involving the mitogen-activated protein kinases p42 and p44, Further analysis of the amino-terminal region of PPAR alpha revealed that the insulin-induced trans-activation occurs through the phosphorylation of two mitogen-activated protein kinase sites at positions 12 and 21, both of which are conserved across evolution. The characterization of a strong AF-1 region in PPAR alpha, stimulating transcription one-fourth as strongly as the viral protein VP16, is compatible with the marked basal transcriptional activity of this isoform in transfection experiments. However, it is intriguing that the activity of this AF-1 region is modulated by the phosphorylation of two serine residues, both of which must be phosphorylated in order to activate transcription. This is in contrast to PPAR gamma 2, which was previously shown to be phosphorylated at a single site in a motif that is not homologous to the sites now described in PPAR alpha. Although the molecular details involved in the phosphorylation-dependent enhancement of the transcriptional activity of PPAR alpha remain to be elucidated, we demonstrate that the effect of insulin on the AF-1 region of PPAR alpha can be mimicked by the addition of triiodothyronine receptor beta 1, a strong binder of corepressor proteins. In addition, a triiodothyronine receptor beta 1 mutant deficient in interacting with corepressors is unable to activate PPAR alpha, These observations suggest that the AF-1 region of PPAR alpha is partially silenced by corepressor proteins, which might interact in a phosphorylation-dependent manner.