neddylation

Neddylation is a post-translational modification in which the ubiquitin-like protein NEDD8 is covalently attached to substrate proteins. The best characterized substrates are the Cullin family proteins, and neddylation of CUL1-5 activates Cullin-RING ubiquitin ligases (CRLs), a major class of E3 ubiquitin ligases that regulate degradation of many regulatory proteins.

Attachment of NEDD8 proceeds through a cascade of enzymatic steps. NEDD8 is activated by the NEDD8-activating enzyme (E1), a heterodimer formed by NAE1 (also known as APPBP1) and UBA3. The activated NEDD8 is transferred to an E2 conjugating enzyme, primarily UBE2M/UBC12 or UBE2F. An E3 ligase then facilitates transfer of NEDD8 to lysine residues on substrates, with CRLs being the principal and physiologically relevant targets.

Conjugation of NEDD8 to cullins promotes conformational changes that stimulate CRL ubiquitin ligase activity, enabling rapid ubiquitination and proteasomal degradation of substrates. Deneddylation by the COP9 signalosome (CSN) reverses this modification, restoring CRLs to a less active state and allowing dynamic regulation.

Non-cullin substrates can also be neddylated by other E3s, and specific deneddylases such as NEDP1 can remove NEDD8 from some substrates.

Neddylation influences cell cycle progression, DNA replication licensing, and responses to DNA damage, among other processes, by modulating the turnover of key regulatory proteins.

Dysregulation of neddylation has been linked to cancer and other diseases. Inhibitors of the NEDD8 activating enzyme, such as pevonedistat (MLN4924), are in clinical development and act by inactivating CRLs, causing accumulation of CRL substrates and promoting apoptosis in tumor cells.

Research continues to define the full spectrum of neddylation substrates and its roles in development and disease.