CRBN also known as cereblon is a protein related to the Lon protease protein family. CRBN is a substrate receptor of the CUL4–DDB1 E3 ubiquitin ligase complex that controls protein homeostasis by directing specific targets for ubiquitination and proteasomal turnover. Through regulation of ubiquitin-dependent degradation, CRBN influences transcriptional programs, cell-cycle progression, and cellular stress responses, linking it to pathways that shape differentiation and immune signaling. CRBN has been studied in the context of developmental biology and neuronal function, and perturbation of its expression or activity is associated with altered proteostasis and disease-relevant phenotypes.