CD18-dependent activation of the neutrophil NADPH oxidase during phagocytosis of Escherichia coli or Staphylococcus aureus is regulated by class HI but not class I or II PDKs

摘要

Phagocytosis and activation of the NADPH oxidase are important mechanisms by which neutrophils and macro-phages engulf and kill microbial pathogens. We investigated the role of PI3K signaling pathways in the regulation of the oxidase during phagocytosis of Staphylococcus aureus and Escherichia coli by mouse and human neutrophils, a mouse macrophage-like cell line and a human myeloid-like cell line. Phagocytosis of these bacteria was promoted by serum, independent of serum-derived an-tibodies, and effectively abolished in mouse neutrophils lacking the (i2-integrin common chain, CD18. A combination of PI3K isoform-selective inhibitors, mouse knock-outs, and RNA-interference indicated CD18-dependent activation of the oxidase was independent of class I and II PI3Ks, but substantially dependent on the single class III isoform (Vps34). Class III PI3K was responsible for the synthesis of Ptdlns(3)P on phagosomes containing either bacteria. The use of mouse neutrophils carrying an appropriate knock-inmutation indicated that Ptdlns(3)P binding to the PX domain of their p40Phox oxidase subunit is important for oxidase activation in response to both S aureus and E coli. This interaction does not, however, account for all the PI3K sensitivity of these responses, particularly the oxidase response to E coli, suggesting that additional mechanisms for Ptdlns(3)P-regulation of the oxidase must exist.