2455-P: Cereblon Regulates Lysosomal Degradation of the Leptin Receptor and Acute Leptin Responsiveness in Hypothalamic Neurons

Introduction and Objective: Leptin signaling in the hypothalamus regulates food intake and body weight, and impairment of the leptin receptor (LEPR) contributes to obesity. Cereblon (CRBN), a substrate receptor of the E3 ubiquitin ligase complex, negatively regulates LEPR signaling. This study examined whether CRBN controls LEPR stability and leptin responsiveness in vitro and in vivo, and whether its effects differ between acute and chronic metabolic regulation. Methods: Cell-based assays used HEK293 cells transiently co-transfected with CRBN and LEPR, or HEK293 cells stably expressing LEPR for leptin treatment. Cells were treated with leptin and/or thalidomide. Protein interaction, ubiquitination, and degradation were assessed by co-immunoprecipitation and western blot. Lysosomal and proteasomal inhibitors evaluated LEPR turnover pathways. In vivo, mice lacking CRBN in LEPR-expressing neurons (CRBN LEPR KO) received 3 consecutive daily leptin injections under normal chow, and body weight responses were measured after fasting-refeeding following 4 and 8 weeks of high-fat diet. Hypothalamic leptin signaling was assessed by phosphorylated STAT3 in CRBN whole-body knockout mice. Results: CRBN reduced LEPR protein via lysosome-dependent degradation, and thalidomide prevented LEPR ubiquitination and degradation. CRBN LEPR KO mice showed greater weight reduction after acute leptin administration and attenuated weight gain after fasting-refeeding, while long-term weight and food intake were unchanged. CRBN whole-body knockout mice exhibited altered long-term metabolic phenotypes. Conclusion: These results show that CRBN promotes lysosomal LEPR degradation and suppresses acute leptin response in the hypothalamus. CRBN deficiency in LEPR-expressing neurons enhances short-term leptin sensitivity and acute weight responses but does not alter long-term energy balance, highlighting a context-dependent role of CRBN in leptin signaling. Disclosure D. Kim: None.