Abstract A whole-cell-based reconstitution system was developed to study the signaling mechanisms underlying chemoattractant-induced activation of NADPH oxidase. This system takes advantage of the lack of formyl peptide receptor-mediated response in COS-phox cells expressing gp91phox, p22phox, p67phox, and p47phox, which respond to phorbol ester and arachidonic acid with O⨪2 production. By exogenous expression of signaling molecules enriched in neutrophils, we have identified several critical components for fMLP-induced NADPH oxidase activation. Expression of PKCδ, but not PKCα, -βII, and -ζ, is necessary for the COS-phox cells to respond to fMLP. A role of PKCδ in neutrophil NADPH oxidase was confirmed based on the ability of fMLP to induce PKCδ translocation and the sensitivity of fMLP-induced O⨪2 production to rottlerin, a PKCδ-selective inhibitor. Optimal reconstitution also requires phospholipase C-β2 and PI3K-γ. We found that formyl peptide receptor could use the endogenous Rac1 as well as exogenous Rac1 and Rac2 for NADPH oxidase activation. Exogenous expression of p40phox potentiated fMLP-induced O⨪2 production and raised the level of O⨪2 in unstimulated cells. Collectively, these results provide first direct evidence for reconstituting fMLP-induced O⨪2 production in a nonhemopoietic cell line, and demonstrate the requirement of multiple signaling components for optimal activation of NADPH oxidase by a chemoattractant.