Regulation of adipose lipid metabolism by new lipid droplet protein

我们最近发现了一个以前未鉴定的38kD蛋白，它包含一个载脂蛋白样结构域，并且在脂肪组织中特异表达。然而，由于缺乏信号序列，该蛋白不能分泌。相反，我们发现它定位于脂滴(LD)，使该蛋白成为新发现的脂肪特异性LD相关蛋白。我们发现，这种新的LD相关蛋白存在于LD接触部位，并促进脂质转移。此外，我们还检测到与Fsp27(也称为CideC)的直接相互作用。此外，这种载脂蛋白样蛋白的编码基因在禁食小鼠的脂肪组织中的表达非常低，但在喂食时会增加，特别是在喂食高脂肪食物时。我们还发现，它在遗传和饮食诱导的肥胖中都过度表达，表明它对肥胖有贡献。我们已经利用CRISPR-Cas9系统获得了在脂肪组织中过表达的转基因小鼠，以及全局KO小鼠。我们的转基因小鼠显示白色脂肪组织(WAT)质量显著增加，脂肪细胞增大，脂肪分解减少，但脂肪生成没有明显变化。相反，我们的全球KO小鼠显示出显著减少的脂肪组织质量，较小的脂肪细胞尺寸和较高的脂肪分解，从而保护小鼠免受饮食诱导的肥胖。我们的长期目标是了解该蛋白作为LD相关蛋白的功能的分子细节和生理意义，以促进WAT中LD的生长/脂质转移和标签储存。目的1是研究载脂蛋白L6对脂质转移的调节。目的2是研究该蛋白对脂解的调节作用。最后，目标3是通过在小鼠身上进行功能丧失和功能获得的研究来检验其在体内的作用。总体而言，拟议的研究将确定这种新发现的LD蛋白在WAT中LD生长/脂质转移和脂解中的作用。这项研究不仅有助于更好地了解脂肪变性的生理学，而且也为肥胖/糖尿病的未来治疗提供了靶点。

We recently identified a previously uncharacterized 38 kD protein, which contains an apolipoprotein-like domain and is specifically expressed in adipose tissue. Due to lack of signal sequence, however, the protein is not secreted. Rather, we found that it is localized to lipid droplets (LD), making this protein a newly discovered adipose-specific LD-associated protein. We found that this new LD-associated protein is found at the LD contact site and promotes lipid transfer. In addition, we detected direct interaction with Fsp27 (also called CideC). Furthermore, expression of the gene coding for this apolipoprotein-like protein is very low in adipose tissue of fasted mice, but is increased upon feeding, especially when fed a high fat diet. We also found it to be overexpressed in both genetic and diet induced obesity, suggesting its contribution to adiposity. We have generated transgenic mice for overexpression in adipose tissue, as well as global KO mice by using CRISPR-Cas9 system. Our transgenic mice showed a greatly increased white adipose tissue (WAT) mass with enlarged adipocytes in WAT, having decreased lipolysis without significant changes in lipogenesis. Conversely, our global KO mice showed a substantially diminished adipose tissue mass with smaller adipocyte size with higher lipolysis that protected mice from diet induced obesity. Our long-term goal is to understand the molecular details and physiological significance of the function of this protein as a LD-associated protein to promote LD growth/lipid transfer and TAG storage in WAT. Aim 1 is to examine regulation of lipid transfer by ApoL6. Aim 2 is to examine regulation of lipolysis by this protein. Finally, Aim 3 is to examine its role in vivo by performing loss- and gain-of function studies in mice. Overall, the proposed research will define the role of this newly discovered LD protein on LD growth/lipid transfer and lipolysis in WAT. This research may not only help to better understand adipose LD physiology but also provide future therapeutic targets for obesity/diabetes.