0024 Decreased circadian period associated with enhanced autophagy in cereblon knockout mice

Abstract

Abstract Introduction The circadian rhythm plays a critical role in many biological processes. Recently, autophagy was suggested as a regulating factor of circadian rhythm by reducing protein trafficking. Cereblon (CRBN) is a component of the E3 ubiquitin ligase complex for ubiquitination and degradation of the target proteins. Interestingly, cereblon ubiquitinates beclin 1, a potent autophagy inducer. Accordingly, the changes in cereblon are likely to affect the circadian rhythm. However, how cereblon can regulate circadian rhythm is not understood yet. Therefore, we hypothesized that cereblon might be an important regulator of the circadian rhythm and sought to investigate the relationship. Methods We obtained 3-month-old CRBN gene knockout (KO) and wild-type (WT) mice (n=4 and 8, respectively). The mice were housed in the wheel-based activity recording system under 12:12 light-dark (LD) condition for 1 week and constant darkness (DD) condition for the subsequent 2 weeks. Activity data were analyzed by ClockLab Analysis 6 (Actimetrics, USA). Autophagy-related proteins, including beclin1, microtubule-associated protein light chain-3 (LC3), and p63, were measured by the ELISA and western blot. Results We found that CRBN KO mice showed decreased circadian period during constant darkness (23.7 vs 23.4 hours, p< 0.05). The latency from the light-off time to initiating activities in the dark period was shorter in CRBN KO mice and WT mice. Protein analysis assay revealed that beclin1, LC3, and p62 increased in CRBN KO mice, indicating increased autophagy. Conclusion Our results demonstrated that CRBN knockout mice showed shorter circadian periods and reduced autophagy-related molecules. We interpret that the lack of cereblon resulted in reduced degradation of beclin1 that triggers autophagy. As per Beesley et al (2020), autophagy-induced decrease in cytoplasmic congestion facilitates the protein trafficking for the crucial components of the molecular circadian clock. The shorter circadian period in CRBN KO mice was primarily due to the enhanced autophagy, although its implication in general health is unclear. Taken together, we suggest that CRBN is associated with circadian rhythm via controlling autophagy. Further investigations to understand how circadian amplitude was increased and the activity latency during the dark period was shortened are needed. Support (if any)