Johnson T E, Holloway M K, Vogel R, Rutledge S J, Perkins J J, Rodan G A, Schmidt A
Department of Genetic and Cellular Toxicology, Merck and Company, West Point, PA 19486, USA.
J Steroid Biochem Mol Biol. 1997 Sep-Oct;63(1-3):1-8. doi: 10.1016/s0960-0760(97)00064-2.
The mammalian peroxisome proliferator-activated receptor (PPAR) family consists of three different subtypes, PPARalpha, hNUC1/PPARdelta and PPARgamma. Selective agonists have been identified for PPARalpha and PPARgamma but not for hNUC1, and consequently little is known about the genes that are controlled by this receptor. Using ligand-dependent transcription assays in COS-7 cells, we screened a variety of PPAR activating agents to identify a selective activator of hNUC1. We found that the potent peroxisome proliferator, Wy-14643, and the PPARgamma-selective thiazolidinedione, BRL 49653, were poor activators of hNUC1 (EC50s of > 100 microM). Short chain fatty acids (FAs) appeared more selective for PPARalpha than for hNUC1, whereas the very long chain FA, erucic acid (C22:1) was more selective for hNUC1. Using erucic acid as a probe, we conducted a topological similarity search of the Merck Chemical Collection and identified a fatty acid-like compound, L-631,033 4-(2-acetyl-6-hydroxyundecyl) cinnamic acid, that was a selective activator of hNUC1 (EC50 of 2 microM), but was much less selective for PPARalpha or PPARgamma (EC50s of > 100 microM). Structure-function analysis of PPAR activation by L-631,033 structural analogues showed that receptor selectivity depends on the position of the carboxyl group relative to the phenyl ring on the molecule. Transfection experiments in several cell types: an osteoblastic cell line (MB 1.8), a mouse liver cell line (ML-457), rat aortic smooth muscle cells (RSMCs) and COS-7 cells revealed differences in the activation profile of specific ligands. The most notable differences were observed in RSMCs, where transactivation by L-631,033 and Wy-14643, but not by BRL 49653, was markedly reduced, and in MB 1.8 cells, where oleic acid failed to activate PPARs. These findings identify certain structural features in PPAR-activating agents that modulate PPAR activation, and suggest that as with other nuclear receptors, activation is cell-type specific.
哺乳动物过氧化物酶体增殖物激活受体（PPAR）家族由三种不同的亚型组成，即PPARα、hNUC1/PPARδ和PPARγ。已鉴定出PPARα和PPARγ的选择性激动剂，但未鉴定出hNUC1的选择性激动剂，因此，对于受该受体调控的基因了解甚少。利用COS-7细胞中的配体依赖性转录分析，我们筛选了多种PPAR激活剂，以鉴定hNUC1的选择性激活剂。我们发现，强效过氧化物酶体增殖剂Wy-14643和PPARγ选择性噻唑烷二酮BRL 49653是hNUC1的低效激活剂（半数有效浓度>100μM）。短链脂肪酸（FAs）对PPARα的选择性似乎高于对hNUC1的选择性，而超长链脂肪酸芥酸（C22:1）对hNUC1的选择性更高。以芥酸为探针，我们对默克化学文库进行了拓扑相似性搜索，鉴定出一种脂肪酸样化合物L-631,033 4-(2-乙酰基-6-羟基十一烷基)肉桂酸，它是hNUC1的选择性激活剂（半数有效浓度为2μM），但对PPARα或PPARγ的选择性要低得多（半数有效浓度>100μM）。L-631,033结构类似物对PPAR激活的结构-功能分析表明，受体选择性取决于分子中羧基相对于苯环的位置。在几种细胞类型中进行的转染实验：一种成骨细胞系（MB 1.8）、一种小鼠肝细胞系（ML-457）、大鼠主动脉平滑肌细胞（RSMCs）和COS-7细胞，揭示了特定配体激活谱的差异。在RSMCs中观察到最显著的差异，L-631,033和Wy-14643可激活转录，但BRL 49653不能，且在MB 1.8细胞中，油酸未能激活PPARs。这些发现确定了PPAR激活剂中调节PPAR激活的某些结构特征，并表明与其他核受体一样，激活具有细胞类型特异性。
