ASB3 limits adipocyte thermogenesis and energy expenditure through p62 ubiquitination.

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