Cullin Ring E3 Ligases (CRLs) belong to the largest family of multisubunit ubiquitin E3 ligases. A cullin serves as the scaffold protein that recruits E3 ligases and substrate receptors in a CRL complex, whose activity requires cullin neddylation, a posttranslational modification that can be pharmacologically targeted by neddylation inhibitors. Elevated neddylation activity has been observed in the liver and adipose tissue of obese mice, implicating a pathogenic link between altered CRL activity and the development of metabolic disorders. Emerging evidence has also shown that neddylation inhibitors possess antiobesity and hypoglycemic property. However, the roles of cullin proteins in regulating adipocyte biology are still incompletely defined. Here, we report that pan neddylation inhibitor TAS4464 treatment reversed obesity and adipose inflammation, resulting in improved hepatic steatosis and insulin sensitivity in obese mice. Among all mammalian cullin proteins that were targeted by TAS4464, we identified that cullin 3 (Cul3) was required for adipogenesis and adipocyte hypertrophy. A complete absence of Cul3 in adipocytes caused severely inhibited adipose expansion associated with ectopic fat accumulation in the liver and brown adipose tissue and insulin resistance, while adipocyte-specific Cul3 haploinsufficiency attenuated obesity and improved overall metabolic homeostasis, which recapitulated the metabolic benefits of TAS4464. Mechanistically, we found that Cul3 inhibition caused adipose nuclear factor erythroid 2-related factor 2 (NRF2) stabilization, which contributed to impaired adipogenesis by inhibiting lipogenesis. Together, these findings demonstrate that Cul3 is required during adipogenesis and acts as a downstream mediator of the antiobesity effect of pan neddylation inhibitors.
Keywords: adipogenesis; diabetes; insulin resistance; obesity.