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和PEX11α基因之间发现了PPAR结合基序。我们发现，PPARγ激活脂肪细胞中的Perilipin基因，而在肝脏中，PPARα分别通过与该位点结合来激活PEX11α基因。因此，我们提出了一种新型的真核基因调控，其中两个基因是通过一个共同的蛋白结合位点进行组织特异性调控的。(2)JNK在人间充质干细胞分化中的作用：我们发现JNK负向调控人多能间充质干细胞向脂肪细胞的分化，而正向调控人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活性的负性作用实现的。(3)新的脂滴结合蛋白的鉴定和性质：鉴定了与Perilipin相互作用的脂滴蛋白CGI-58。携带相同…氨基酸替换的cgi-58突变蛋白更多的是Chanarin-Dorfman综合征患者既不与Perilipin结合，也不与脂滴结合。CGI-58被认为可以激活脂肪酶，从而促进脂滴表面的脂类降解。接下来，我们鉴定了PAT家族的一个新成员MLDP，其中也包括Perilipin。MLDP被发现是一种脂滴结合蛋白，特别是在心脏中丰富。MLDP在禁食过程中被诱导，其表达依赖于PPARα。(4)脂肪细胞分化过程中核受体的研究：我们发现PPARγ在N-末端区域受相扑结合的负调控。我们还发现，在3T3-L1细胞成脂初期诱导的NGFI-B通过对3T3-L1细胞的生长起到促进分化的作用。此外，我们发现Errα和γ具有非常广泛的序列识别特异性。较少

(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