PtdIns3P binding to the PX domain of p40phox is a physiological signal in NADPH oxidase activation.

The production of reactive oxygen species by the NADPH oxidase complex of phagocytes plays a critical role in our defence against bacterial and fungal infections. The PX domains of two oxidase components, p47phox and p40phox, are known to bind phosphoinositide products of PI3Ks but the physiological roles of these interactions are unclear. We have created mice which carry an R58A mutation in the PX domain of their p40phox gene, which selectively prevents binding to PtdIns3P. p40phoxR58A/R58A embryos do not develop normally but p40phoxR58A/- mice are viable and neutrophils from these animals exhibit significantly reduced oxidase responses compared to those from their p40phox+/- siblings (e.g. 60% reduced in response to phagocytosis of Staphylococcus aureus). Wortmannin inhibition of the S. aureus oxidase response correlates with inhibition of phagosomal PtdIns3P accumulation and overlaps with the reduction in this response caused by the R58A mutation, suggesting PI3K regulation of this response is substantially dependent on PtdIns3P-binding to p40phox. p40phoxR58A/- mice are significantly compromised in their ability to kill S. aureus in vivo, defining the physiological importance of this interaction. [ABSTRACT FROM AUTHOR]