Dysregulated hepatic lipid metabolism causes lipotoxicity and liver diseases, such as non-alcoholic fatty liver disease (NAFLD). Cyclic AMP responsive element binding protein 3-like 3 (CREB3L3, also known as CREBH) is a liver-enriched transcription factor. CREBH acts as a fasting-responsive metabolic sensor to maintain hepatic lipid homeostasis. Recent studies illustrated protein-protein interactions plays critical roles in full-length CREBH activation and in executing transcription functions of activated CREBH. In this project, I aim to reveal CREBH protein interaction partners (PIPs) in the membrane and nuclear protein fractions of mouse livers in order to investigate regulation and function of CREBH in response to feeding or fasting challenge. I have discovered more than 2000 PIPs in the liver subcellular fraction groups. For the first time, my study revealed the interaction of CREBH with the lipid droplet (LD) protein, PLIN2. Knockout of the Crebh gene has no effect on expression of PLIN2 in the liver during fasting. However, Plin2 knockdown significantly reduced CREBH protein level in both mouse primary hepatocytes and mouse hepatoma cell line. Further, treatment of oleic acids (OA) did not revert the down-regulation of CREBH by Plin2 knockdown. PLIN2 knockdown can decrease expression of CREBH-target genes that are involved in lipolysis, fatty acid oxidation and autophagy. The findings from my studies lead to a novel model for CREBH activation: CREBH is translocated to the LD for storage and then stabilized by binding to PLIN2, through which CREBH protein level and activity can be enhanced. In mouse liver nucleus, CREBH was found to interact with the nuclear receptors PPARα and PGC1α to synergistically regulate hepatic autophagy in response to nutrient starvation. Finally, a novel transcription partner, HNF1α, has been identified to interact with CREBH in the liver nuclear protein fraction, implicating a transcriptional regulation of liver metabolism by CREBH through partnering with HNF1α.
|Commitee:||Finley, Russell, Li, Li, Chen, Xuequn|
|School:||Wayne State University|
|Department:||Molecular Biology and Genetics|
|School Location:||United States -- Michigan|
|Source:||DAI-B 81/3(E), Dissertation Abstracts International|
|Subjects:||Molecular biology, Bioinformatics, Genetics|
|Keywords:||CREB3L3, Interaction partner, Lipid droplet, Lipophagy, Quantitative proteomics, Transcription factor|
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