Identification and functional analysis of intrinsic and extrinsic key regulators of adipocyte differentiation.

（1）PPARγ对perilipin基因表达的调控机制：在小鼠perilipin基因和PEX 11 α基因之间存在一个PPAR结合基序。我们发现，在脂肪细胞中，PPARγ激活perilipin基因，而在肝脏中，PPARα分别激活PEX 11 α基因，两者都是通过结合到该位点。因此，我们提出了一种新的真核基因调控类型，其中两个基因通过共同的蛋白质结合位点进行组织特异性调控。（2）JNK在人骨髓间充质干细胞分化中的作用：JNK负性调控多能间充质干细胞向脂肪细胞的分化，而正性调控多能间充质干细胞向成骨细胞的分化。这可能是通过JNK对CREB和IRS-1活性的负作用。（3）新的脂滴结合蛋白的鉴定与鉴定：鉴定了一种与perilipin相互作用的脂滴蛋白CGI-58。携带相同氨基酸取代的CGI-58突变体蛋白质 关于我们 与Chanarin-Dorfman综合征患者的那些既不与周脂蛋白结合也不与脂滴结合一样。CGI-58被认为激活脂肪酶，因此促进脂滴表面上的脂质降解。接下来，我们鉴定了PAT家族的新成员MLDP，其中还包括围脂蛋白。MLDP被发现是一种脂滴结合蛋白，特别是在心脏中富集。MLDP在禁食期间诱导，其表达依赖于PPARα。我们认为，MLDP有助于脂质在心脏中的特征性快速周转。（4）与脂肪细胞分化有关的核受体研究：我们发现，SUMO结合在N端区域对PPARγ有负调控作用。我们还发现NGFI-B在3 T3-L1细胞脂肪形成的初始阶段被急性诱导，通过在初始阶段对细胞生长的作用而对分化产生刺激作用。此外，我们发现ERRα和ERR γ具有非常广泛的序列识别特异性。少

(1)Regulatory mechanism of perilipin gene expression by PPARγ : A PPAR-binding motif was found between the mouse perilipin and PEX11α genes. We showed that PPARγ activates the perilipin gene in the adipocytes, whereas in the liver, PPARα activates the PEX11α gene, respectively, both by binding to this site. Hence, we presented a novel type of eukaryotic gene regulation, where two genes are regulated tissue-specifically through a common protein-binding site.(2)Role of JNK in the differentiation of human mesenchymal stem cells : We found that JNK regulates the differentiation of multipotent human mesenchymal stem cells into adipocytes negatively, whereas that into osteoblasts positively. This was possibly through negative actions of JNK on CREB and IRS-1 activities.(3)Identification and characterization of novel lipid droplet-binding proteins : CGI-58, a lipid droplet protein interacting with perilipin, was identified. The CGI-58 mutant proteins carrying the amino acid substitutions same … More as those of Chanarin-Dorfman syndrome patients bound to neither perilipin nor lipid droplets. CGI-58 was suggested to activate lipases, and hence promotes lipid degradation on the lipid droplet surfaces. Next, we identified MLDP, a new member of PAT family, in which perilipin is also included. MLDP was found to be a lipid droplet-binding protein particularly enriched in the heart. MLDP was induced during fasting, the expression being dependent on PPARα. We suggest that MLDP contributes to the characteristically rapid turnover of lipids in the heart.(4)Investigation of nuclear receptors involved in adipocyte differentiation : We showed that PPARγ is negatively regulated by SUMO conjugation in the N-terminal region. We also found that NGFI-B, acutely induced in the initial stage of adipogenesis of 3T3-L1 cells, exerts a stimulatory effect on the differentiation, through the action on the cell growth in the initial stage. Furthermore, we found that ERRα and γ have extraordinarily broad specificities of sequence recognition. Less