Functional analysis of new PPARγ coactivator and elucidation of emergence mechanism of diabetes.

甲状腺激素受体相互作用蛋白3（TRIP 3）是一种功能未知的蛋白质，与甲状腺激素受体（TR）和类维生素A激素X受体（RXR）相互作用，但不与糖皮质激素受体（GR）相互作用。最近我们克隆了TRIP 3的全长cDNA，并鉴定了TRIP 3还与肝细胞核因子-4 α（hepatocyte nuclear factor-4α，HNF-4α）相互作用，激活HNF-4α的反式激活活性。过氧化物酶体增殖物激活受体γ（Peroxisome proliferator-activated receptor γ，PPARγ）是另一种转录因子，属于核受体因子家族。PPARγ是脂肪细胞分化的主要调节因子，在调节参与脂质和葡萄糖代谢的基因中起重要作用。在本研究中，我们检测了TRIP 3对PPARγ反式激活活性的影响。TRIP 3 mRNA在人内脏和皮下脂肪组织中表达。GST pull-down实验和哺乳动物双杂交实验表明TRIP 3与PPARγ直接结合。缺失研究表明TRIP 3与PPARγ的AF-2结构域相互作用。TRIP 3在C末端含有一个短的保守的LXXLL基序。然而，缺失实验表明ThIP 3的N端在与PPARγ的相互作用中是重要的。报告基因分析表明，TRIP 3在其合成配体存在（2.0-5.0倍，p<0.05）或不存在（2.4-5.0倍，p<0.05）的情况下以剂量依赖性方式显著增加PPARγ的转录激活活性。TRIP 3可能作为PPAR γ的共激活因子。

Thyroid hormone receptor interacting protein 3(TRIP3) is a protein with unknown function that interacts with thyroid hormone receptor(TR) and retinoid hormone X receptor(RXR), but not with glucocorticoid receptor(GR). We have recently doned the full length TRIP3 cDNA and identified that TRIP3 also directly interacts with hepatocyte nuclear factor-4α (HNF-4α) and activated the transactivation activity of HNF-4α Peroxisome proliferators-activated receptor γ (PPARγ) is another transcription factor, belonging to the nuclear receptor factor family. PPARγ is a master regulator for adipocyte differentiation and is important in regulation of genes involved in lipid and glucose metabolism. In the present study, we examined the effect of TRIP3 on PPARγ transactivation activity. TRIP3 mRNA was expressed in human visceral and subcutaneous fat tissues. GST pull-down assay and mammalian two-hybrid assay showed that TRIP3 directly bound to PPARγ. Deletion studies indicated that TRIP3 interacted with the AF-2 domain of PPARγ. TRIP3 contains a short conserved LXXLL motif, in the C terminus. However, deletion experiments suggested that N terminus of ThIP3 was important for the interaction with PPARγ. A reporter gene assay showed that TRIP3 significantly increased the transcriptional activation activity of PPARγ in dose dependent manner in the presence(2.0-5.0 fold, p<0.05) or absence(2.4-5.0 fold, p<0.05) of its synthetic ligand. TRIP3 may act as a coactivator of PPAR γ.