UBD (ubiquitin-like modifier D) is a ubiquitin-like protein that functions as a post-translational modifier targeting proteins for proteasomal degradation in an NUB1-dependent manner 123. UBA6 activates UBD conjugation to target proteins via adenylation of its C-terminal glycine 45. UBD regulates innate immunity by promoting TNF-mediated proteasomal degradation of ubiquitinated IκB-α, enabling NF-κB activation 6. The protein participates in dendritic cell maturation and contributes to immune responses 7. UBD mediates mitotic non-disjunction and chromosome 6 by abbreviating mitotic phase and impairing MAD2L1 kinetochore localization 8. In renal disease contexts including polycystic kidney disease and HIV-associated nephropathy, UBD mediates caspase-dependent apoptosis in renal epithelial and tubular cells 9. Recently, UBD was identified as a genetic modifier of APOL1-associated kidney disease, where reduced UBD expression correlates with increased APOL1-mediated toxicity, suggesting UBD mitigates APOL1 pathogenicity through proteasomal targeting 10. Additionally, UBD was identified as a novel gene associated with depressive symptoms through exome-wide association analysis, linking it to immune and neuropsychiatric traits 11. UBD also mediates claudin-5 degradation in endothelial cells through the IKZF1-UBD axis, affecting blood-brain barrier integrity 12.