Posttranslational protein modifications (PTMs) are necessary for cells to 
function properly. The role of PTMs in regulating immune responses, specifically 
those mediated by dendritic cells (DCs), which are critical for both innate and 
adaptive immunity, is not well understood. Utilizing multiple but complementary 
approaches, we determined the role of an important but less understood type of 
PTM, namely, neddylation, in regulating DC functions. Inhibition of neddylation 
suppressed the release of proinflammatory cytokines by DCs in response to 
Toll-like receptor, nucleotide oligomerization domain-like receptor, and 
noninfectious CD40L stimulation. These effects were more profound than those 
mediated by the proteasome inhibitor bortezomib or a commonly used 
antiinflammatory agent, dexamethasone. Targeting neddylation also suppressed the 
ability of DCs to stimulate murine allogeneic T cells in vitro and in vivo and 
human allogeneic T-cell responses in vitro. Mechanistic studies demonstrated 
that inhibition of neddylation reduced both canonical and noncanonical nuclear 
factor-κB (NF-κB) activity. Neddylation inhibition prevented the degradation of 
inhibitor-κB and thus reduced the translocation and activation of NF-κB, but 
without perturbation of the mitogen-activated protein kinase/extracellular 
signal-regulated kinase pathway. Thus, blocking neddylation could be a novel 
strategy for mitigating immune-mediated disease processes.