PCG-1β及其内含子小核酸在成脂分化的过程中调节细胞自噬的机理研究

Autophagy has been proved to be important in the maintenance of cellular homeostasis and energetic balance. Genetic knockout studies also shown that autophagy is essential in the process of adipocyte differentiation and obesity. PGC-1β and miR-378a are deeply involved in energetic metabolism, it is possible that PGC-1βand miR-378a are also related to adipogenesis. In this project, we will investigate the potential roles and the underlying molecular mechanism of PGC-1β and miR-378a in modulating autophagic process and adipogenesis. .Mir-378a is intronic miRNA embedded in the first intron of Ppargc1b gene which encodes PGC-1β, a transcriptional coactivator and metabolic regulator. As an intronic miRNA, miR-378a should co-express with its host gene. However, in our previous study, we found that miR-378a and Ppargc1b do not have a fully co-expressive relationship at expression level and miR-378a antagonize the function of its host gene at function level. So, we also will use intronic miR-378a and its host PGC-1βas model to analyze the biologic significance of the relationship between PGC-1β and Mir-378a in the regulation of autophagy and adipocyte differentiation. .In our previous study, we already found that PGC-1β represses autophagic activity through up-regulating MTORC1 pathway. Importantly, ChIP assay demonstrates that Mtor gene expression is transcriptionally regulated by Ppargc1b. Interestingly, we find that Ppargc1b is a direct target of is its intronic Mir-378a. Overexpression of Mir-378a enhances adipogenesis via activating autophagy. To further antagonize the function of its host gene, Mir-378a induces autophagy and adipogenesis by directly suppressing the expression of Rubicon, a negative regulator of autophagosome maturation. Silencing Rubicon leads to significant reduction of lipid accumulation..This study will provide some new information about autophagy regulation and will facilitate a deeper understanding about the relationship of intronic miRNAs and their host genes.

细胞自噬在调节能量代谢，维持细胞稳态中起重要作用, 基因敲除实验证明自噬在成脂分化的过程中也是必要的。miR-378a来自PGC-1β基因的第一内含子，两者都是调节能量代谢的重要分子。由于自噬与代谢和成脂分化关系密切，所以PGC-1β和miR-378a均有可能介入了细胞自噬和成脂分化的调节。我们首先采用细胞生物学和分子生物学的方法，研究PGC-1β和miR-378a对细胞自噬和成脂分化的调节及其机理，再结合生物信息学以及基因分子生物学的手段，以miR-378a和它的宿主基因PGC-1β为模型，研究在成脂分化过程中，内含子小核酸miR-378a在表达上与其宿主基因PGC-1β不完全同步，以及在功能上与PGC-1β相拮抗的机理和生物学意义。本项目的研究不仅有助于加深对细胞自噬和成脂分化机理的理解，还能进一步揭示内含子miRNA与其宿主间基因之间的复杂关系，有重要的学术意义。

本课题研究PGC-1β和miR-378a对细胞自噬及成脂分化的调节作用及其分子机理，并以PGC-1β和miR-378a为例，分析内含子miRNA与其宿主基因间的相互关系,包括miR-378a和它的宿主基因PGC-1β在功能上是协同关系还是拮抗关系，在基因的表达上是共同表达还是非共同表达的关系。研究工作已经完成。我们启动了同受PGC-1调节的另外一条非编码核酸EPB4IL4A-AS1调节代谢的课题，研究了长非编码核酸EPB4IL4A-AS1在不同疾病中调节代谢的现象及机理， 论文分别在EBioMedicine和Mol Ther Nucleic Acids杂志发表。我们发现EPB41L4A-AS1基因受p53 调控。生物信息学的数据分析显示，在多种癌症中EPB41L4A-AS1表达下调，其表达水平与患者的预后有关，EPB4IL4A-AS越低者预后越差。近一步的细胞和分子生物学的实验发现EPB41L4A-AS1下调改变肿瘤细胞的糖代谢模式，造成有氧糖代谢增加和对谷胺酰胺的依赖增加，进而加快了肿瘤的生长。上述现象的发生与EPB41L4A-AS1作为长非编码核酸调节了VHL和VDAC1两个关键基因的表达有关。我们还发现，怀孕早期的反复流产病人胎盘绒毛组织中的EPB41L4A-AS1表达过高，抑制了胎盘快速生长所依赖于Warburg效应，使绒毛细胞生长减缓，凋亡增加。这可能是怀孕早期发生病理性的反复流产发生的原因之一。 该发现不仅有助于加深对怀孕早期反复流产病理机理的理解，也可能为怀孕早期反复流产的治疗提供新的思路。