Page 22 - N. Metabolism and metabolic diseases

[N. Metabolism and metabolic diseases-11]

Study on the molecular mechanisms of deubiquitinating

enzyme USP1 in the regulation of adipogenesis

Myung Sup Kim¹, Kyung-Hee Chun¹˙*

¹Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, Seoul 120-752, Korea

The Ubiquitin specific peptidase 1 (USP1) is an enzyme that is encoded by the Usp1 gene. USP1 is a family of a
deubiquitinating enzyme (DUB) with His and Cys domains. This protein is known to be located in the cytoplasm
and cleaves the ubiquitin from ubiquitin attached precursors. USP1 is most widely studied in the disease Fanconi

anemia (FA) DNA repair pathway1,2. But the metabolic role of USP1 is not fully understood. In this study, we

investigated whether USP1 regulates adipocyte differentiation and obesity. The level of USP1 increased during the
adipocyte differentiation process and was predominantly expressed in mouse fat tissues. We discovered
glucocorticoid receptor binding element is existing in the promoter region of USP1 and accordingly, dexamethasone,

a glucocorticoid receptor agonist treatment led to the higher luciferase activity. USP1 knock down induced by siRNA
extremely attenuated adipocyte differentiation of 3T3-L1 cells and also decreased the expression levels of adipogenic

and lipogenic markers proliferator-activated receptor (PPAR)-γ, ccaat enhancer binding protein (C/EBP) α, ccaat
enhancer binding protein (C/EBP) β, fatty acid binding protein (FABP) 4 and fatty acid synthase (FASN). USP1 is

majorly located in the nucleus of 3T3-L1 before the differentiation, and when the differentiation is induced by
dexamethasone, insulin, and 3-isobutyl-1-methylxanthine, it is spread throughout the cell ubiquitously. We

investigated that USP1 is important in the process of mitotic clonal expansion if adipocyte differentiation. ML3233,
a USP1-specific inhibitor treatment to 3T3-L1 cells also inhibited adipocyte differentiation and lipid accumulation.

Adipogenic markers and lipogenic markers of ML323 treated 3T3-L1 cells were also extremely down regulated.
Accordingly, we injected ML323 to C57BL/6 mice which was obese induced with high-fat diet (HFD). Mice injected

with USP1 inhibitor showed improved body weight, adipose tissue size and weight, and mRNA levels of adipogenic,
lipid oxidation, and inflammation markers. These results suggest that USP1 is an important factor in regulating the

adipocyte differentiation process and USP1 might be potential therapeutic target in obesity.