p40phox as an alternative organizer to p47phox in Nox2 activation: A new mechanism involving an interaction with p22phox

p40phox activated phagocyte NADPH oxidase without p47phox in a cell-free system consisting of p67phox, Rac and cytochrome b558 relipidated with phosphatidylinositol 3-phosphate. The activation reached to 70% of that by p47phox. Addition of p47phox slightly increased the activation, but not additively. p40phox improved the efficiency of p67phox in the activation. The C-terminus-truncated p67phox, p40phox(D289A), p40phox(R58A), or p40phox(W207R) showed an impaired activation. A peptide corresponding to the p22phox Pro-rich region suppressed the activation, and far-western blotting revealed its interaction with p40phox SH3 domain. Thus, p40phox can substitute for p47phox in the activation, interacting with p22phox and p67phox through their specific regions.