Ubiquitin-proteasome system regulates adipogenic differentiation by stabi-lizing HSP90-dependent PPARγ / 中国病理生理杂志

ABSTRACT

AIM: To investigate the role of ubiquitin-proteasome system ( UPS) in adipocyte differentiation. METHODS:Differentiation of 3T3-L1 preadipocytes into adipocytes was induced by treatment with insulin, 3-isobutyl-1-methylxanthine and dexamethasone.Western blot and immunoprecipitation were performed to detect the protein abundances and association, respectively.Oil red O staining was used to determine the intracellular lipid of 3T3-L1 adipocytes.The levels of mRNA were measured by reverse transcription polymerase chain reaction ( RT-PCR) .RESULTS:UPS inhibitor bortezomib (BZM) suppressed the differentiation of 3T3-L1 pre-adipocytes, evidenced by reduced intracellular content of triglyceride, and decreased mRNA expression of adipogenic marker proteins such as adiponectin and adipocyte protein 2.In contrast, administration of sildenafil (SDN), an activator of protein kinase G which was also found to activate UPS, promo-ted adipocyte differentiation.In addition, BZM treatment decreased the expression of heat shock protein 90 (HSP90) and peroxisome proliferator-activated receptor gamma ( PPARγ) in the soluble fraction and reduced association of HSP90 and PPARγ.Furthermore, HSP90-specific N-terminal inhibitor geldanamic mitigated SDN-induced increase in PPARγlevel and 3T3-L1 cell differentiation.CONCLUSION:UPS modulates HSP90-dependent PPARγstability, thus leading to pro-motion of adipocyte differentiation.