Molecular mechanism for activation of the reactive-oxygen-species-producing phagocyte NADPH oxidase that is involved in host defense.

NADPH氧化酶产生活性氧，在宿主防御中起着至关重要的作用。作为这些酶的原型，吞噬细胞NADPH氧化酶的催化中心存在于膜蛋白gp91^<phox>中，它与p22^<phox>络合形成细胞色素b_<558>。gp91^<phox>的激活是由于刺激诱导的特异性衔接蛋白p47^<phox>, p67^<phox>和p40^<phox>的膜移位，其靶向导致与细胞色素的相互作用。在这两年中，我们研究了NADPH氧化酶的激活机制，得到了以下发现。(1)已知p47^<phox>的膜移位需要与p22^<phox>相互作用。我们已经证明，这种相互作用是由p47^<phox> SH3结构域的一种新的识别模式介导的。此外，我们还确定了p47^<phox> SH3结构域与p22^<phox>肽的复合物的NMR结构。(2) p47^<phox>-p67^<phox>…更多的相互作用是p67^<phox>的膜移位所必需的。我们已经证明，p47^<phox>中Ser-379的磷酸化导致p47^<phox>-p67^<phox>相互作用的衰减，从而调节吞噬细胞NADPH氧化酶的激活。(3)我们发现p47^<phox>的151 ~ 153氨基酸是通过与gp91^<phox>相互作用参与氧化酶激活的残基。(4) gp91^<phox>同源物Nox1被认为在结肠上皮细胞的宿主防御中起重要作用。我们发现，小GTPase Rac通过促进Noxa1 （p67^<phox>的同源物）的膜定位，并通过诱导Noxa1的构象变化，直接参与Nox:Rac功能的激活。我们还发现，在内耳中表达的gp91^<phox>同源物Nox3与p22^<phox>形成异源二聚体，并且Nox3的活性被p47^<phox>、Noxo1或p67^<phox>增强，前两者通过与p22^<phox>相互作用而起作用。少

Enzymes called NADPH oxidases produce reactive oxygen species, which play a crucial role in host defense. The catalytic center of the phagocyte NADPH oxidase, the prototype of these enzymes, exists in the membrane protein gp91^<phox>, which is complexed with p22^<phox> to form cytochrome b_<558>. Activation of gp91^<phox> results from stimulus-induced membrane translocation of the specific adaptor proteins p47^<phox>, p67^<phox>, and p40^<phox>, which targeting leads to interaction with the cytochrome. During these two years, we have investigated the mechanism for activation of NADPH oxidases and obtained the following findings.(1)It is known that the membrane translocation of p47^<phox> requires its interaction with p22^<phox>. We have shown that the interaction is mediated by a novel mode of recognition by the p47^<phox> SH3 domains. In addition, we have determined the NMR structure of the complex of the p47^<phox> SH3 domains with a peptide of p22^<phox>.(2)The p47^<phox>-p67^<phox> … More interaction is known to be essential for the membrane translocation of p67^<phox>. We have demonstrated that phosphorylation of Ser-379 in p47^<phox> results in attenuation of the p47^<phox>-p67^<phox> interaction, thereby regulating activation of the phagocyte NADPH oxidase.(3)We have identified the amino acids 151-153 of p47^<phox> as residues that participate in oxidase activation by interacting with gp91^<phox>.(4)The gp91^<phox> homologue Nox1 is considered to play an important role in host defense by colon epithelial cells. We have revealed that the small GTPase Rac is directly involved in activation of Nox:Rac functions by facilitating membrane localization of Noxa1,a homologue of p67^<phox>, and by inducing a conformational change of Noxa1. We have also shown that Nox3,the gp91^<phox> homologue expressed in the inner ear, forms a heterodimer with p22^<phox>, and Nox3 activity is enhanced by p47^<phox>, Noxo1,or p67^<phox>, the former two of which act by interacting with p22^<phox>. Less