Lung infections are major causes of acute lung injury (ALI), with limited effective treatment available. Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an essential adaptor regulating Toll-like receptors (TLRs). We recently identified Cullin-5 (Cul-5) as a prominent component in the regulation of TRAF6 polyubiquitination, but its physiological significance in ALI has not been explored. In this study, we investigated the potential role of Cul-5 in regulating ALI using mice receiving intratracheal instillation of LPS. We observed that Cul-5-deficient mice displayed reduced lung injury compared with wild-type mice as evidenced by histological analysis, alveolar neutrophil infiltration, and lung liquid accumulation. In addition, inflammatory cytokine expression in bronchoal-veolar lavage fluid and lung tissue was also markedly reduced in LPS-treated Cul-5-deficient mice. Interestingly, intratracheal adoptive transfer of Cul-5(+/-) but not Cul-5(+/+) macrophages attenuated neutrophil recruitment, alveolar inflammation, and loss of barrier function in LPS-challenged wild-type mice. Finally, we demonstrated that Cul-5 neddylation following LPS exposure induced Cul-5 and TRAF6 interaction and, thereby, TFAR6 polyubiquitination, leading to NF-kappa B activation and generation of proinflammatory cytokines. Our data show that neural precursor cell expressed developmentally down-regulated protein 8 (Nedd8) modification of Cul-5 is required for its interaction with TRAF6 and activation of the TLR4-TRAF6 signaling pathway in LPS-induced ALI, a feature that may be explored for therapeutic intervention.