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PPARgamma ubiquitination sites in HEK293T cells

ABSTRACT: Peroxisome proliferator–activated receptor γ (PPARγ) is the central regulator of adipogenesis, and its dysregulation is linked to obesity and metabolic diseases. Identification of the factors that regulate PPARγ expression and activity is therefore crucial for combating obesity. Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor with a known role in xenobiotic detoxification. Recent studies have suggested that AhR also plays essential roles in energy metabolism. However, the detailed mechanisms remain unclear. We previously reported that experiments with adipocyte-specific Cullin 4b (Cul4b)-knockout mice showed that CUL4B suppresses adipogenesis by targeting PPARγ. Here, using immunoprecipitation, ubiquitination, real-time PCR and Gst-pulldown assays, we report that AhR functions as the substrate receptor in CUL4B–RING E3 ubiquitin ligase (CRL4B) complex and is required for recruiting PPARγ. AhR overexpression reduced PPARγ stability and suppressed adipocyte differentiation, and AhR knockdown stimulated adipocyte differentiation in 3T3-L1 cells. Furthermore, we found that two lysine sites on residues 268 and 293 in PPARγ are targeted for CRL4B-mediated ubiquitination, indicating cross-talk between acetylation and ubiquitination. Our findings establish a critical role of AhR in regulating PPARγ stability and suggest that the AhR–PPARγ interaction may represent a potential therapeutic target for managing metabolic diseases arising from PPARγ dysfunction.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Hao Dou

LAB HEAD: Yaoqin Gong

PROVIDER: PXD015830 | Pride | 2019-11-01

REPOSITORIES: Pride

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Project description:Metabolic syndrome is an important public concern and demand for effective therapeutic strategies. Abdominal obesity, especially an increase in the visceral adipose tissue, is the main cause of this syndrome. Flavonoids are expected to improve risk factors for metabolic syndrome. Bilberry, original species of blueberry containing anthocyanidin flavonoids have been used for centuries in Europe to ameliorate the symptoms of diabetes, but their effects and the mechanisms on lipid accumulation of adipocyte cells are not well defined. In the present study, we investigated effects of the Bilberry extract on differentiation of adipocytes using 3T3-L1 adipocyte cell line. Exposure to Bilberry extract during the early period of adipogenesis (6 days) was significantly inhibited adipocyte differentiation of 3T3-L1. During this period, Bilberry extract greatly down-regulated the mRNA levels of the key adipogenesis-associated markers peroxisome proliferator-activated receptor-γ (PPARγ). Furthermore, Bilberry extract significantly decreased expression of the transcription factor Sterol Regulatory Element Binding Protein 1c (SREBP1c), which plays a central role in adipocyte differentiation including the induction of PPARγ. The expression of SREBP1c is remarkably enhanced in response to insulin, thus raises the possibility that Bilberry extract might inhibit the Insulin pathway. So, We investigated whether Billberry extract and anthocyanidines turned the insulin signaling pathway using microarray. As a result, Gene Set Enrichment Analysis (GSEA) shows that these additives turned insulin signaling pathway certainly. We quantified expression profiles of whole mRNAs by microarray in the adipocyte from 3T3-L1 with or without additives. 3T3-L1 preadipocytes (American Type Culture Collection, Manassas, VA) were grown to confluence in DMEM media (Sigma Aldrich, Tokyo, Japan) with 10% calf serum and penicillin (100 U/ml)/streptomycin (100 ug/ml). Adipogenesis was induced using an adipogenesis assay kit (Chemicon International, Temecula, CA). On day 0, cells were induced with initiation media (10 ug/ml insulin, 1 uM dexamethasone and 0.5 uM IBMX in DMEM media added with 1: 0.1% DMSO, 2: 100 ug/ml Bilberry extract, 3: 100 nM Delphinidin or 4: 100 nM Cyanidin (total 4 samples). On day 2, harvested the cells, extracted total RNA and did microarray experiments.

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PPARgamma ubiquitination sites in HEK293T cells

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