The adaptor protein ARAP contributes to Akt-dependent NF-κB p50 activation and inflammatory cytokine production in dendritic cells.

Adaptor proteins play critical roles in determining the specificity of innate immune signaling pathways. Here, we report that a previously uncharacterized adaptor protein, ARAP (activation-dependent, raft-recruited ADAP-like phospho-protein), is critical for lipopolysaccharide (LPS)-induced cytokine production in dendritic cells (DCs). Bone marrow-derived DCs (BMDCs) isolated from ARAP knockout (ARAP-KO) mice exhibited a significant reduction in proinflammatory cytokine production following LPS stimulation. Mechanistically, ARAP-KO-derived BMDCs displayed normal activation of mitogen-activated protein kinases and inhibitor of κBα (IκBα) degradation, along with preserved nuclear translocation of nuclear factor-κB (NF-κB) p65. However, the nuclear translocation of the NF-κB p50 subunit was markedly impaired. Concomitantly, LPS-induced Akt phosphorylation was attenuated in ARAP-KO-derived BMDCs. Pharmacological inhibition of Akt in wild-type BMDCs phenocopied the defect in p50 nuclear translocation. These findings reveal a non-canonical mechanism in which ARAP is required for p50 nuclear translocation in an Akt-dependent pathway, independent of classical IκB kinase-IκB signaling, adding mechanistic insight into innate immune signaling.