ASB3 limits adipocyte thermogenesis and energy expenditure through p62 ubiquitination

Adipose thermogenesis increases energy expenditure and protects against obesity. However, the endogenous mechanisms that restrain this process are not fully understood.

Adipose tissue- and adipocyte-specific Asb3-deficient mice were exposed to cold or treated with the β3-adrenergic receptor agonist CL-316,243. Primary thermogenic adipocytes were used to assess adipogenic differentiation and β3-adrenergic/cAMP-PKA responses. Proteomic/phosphoproteomic profiling, co-immunoprecipitation, ubiquitination assays and domain mapping were performed to define the mechanism. Adipose p62 knockdown and high-fat-diet feeding were used to evaluate in vivo relevance.

The abundance of ASB3 protein increased in inguinal white adipose tissue (iWAT) following cold exposure or β3-adrenergic stimulation. Conversely, adipose-tissue- or adipocyte-specific deletion of Asb3 enhanced iWAT browning induced by cold exposure and b3-adrenergic receptor agonist CL-316,243, as well as brown adipose tissue activation and thermogenic gene expression. In primary beige adipocytes, ASB3 deficiency potentiated the thermogenic response to activation of the β3-adrenergic/cAMP-PKA pathway. Mechanistically, ASB3 interacted with p62 through its ankyrin-repeat region, promoting p62 ubiquitination involving both K48- and K63-linked ubiquitin chains. Loss of ASB3 was associated with increased p62 abundance and nuclear accumulation. Conversely, local p62 knockdown in iWAT attenuated ASB3 deficiency-induced beiging, thermogenic signaling and whole-body energy expenditure. Furthermore, adipose-tissue-specific ASB3 deficiency protected mice against weight gain, fat accumulation, hepatic steatosis, glucose intolerance and insulin resistance by a high-fat diet.

These findings indicate the critical role of the ASB3-p62 ubiquitin axis in restricting adipose tissue thermogenic plasticity and suggest that ASB3 may be a promising therapeutic target for obesity and related metabolic disorders.