The Phosphoinositide-Binding Protein p40phox Regulates NADPH Oxidase Activation Rather Than Assembly during FcγIIA Receptor-Induced Phagocytosis.
Notice bibliographique
Résumé
Abstract Many critical features of the organization and regulation of the phagocyte NADPH oxidase, a complex multi-subunit enzyme that generates superoxide for microbial killing, remain poorly defined. The active enzyme includes a membrane-bound flavocytochrome b along with p47phox, p67phox, p40phox, and Rac-GTP that are present in the cytosol of resting cells. p67phox is linked by high affinity interactions with both p47phox and p40phox, which appear to translocate as a trimeric complex upon cellular activation. The p47phox subunit acts as an adaptor to promote translocation by docking at a proline-rich target sequence on the flavocytochrome, and p67phox is a Rac-GTP effector containing a domain that activates electron transport. In contrast, the function of p40phox, which is not required for high level oxidase activity in cell free systems, is poorly understood. Recently, our group showed that p40phox plays key role in the activation of superoxide production during phagocytosis of IgG-opsonized targets in COSphoxFcγR cells. This model cell line contains stable transgenes for the flavocytochrome, p47phox, p67phox, and the FcγIIA receptor, without or with an additional transgene for p40phox. p40phox-dependent coupling of FcγR-mediated phagocytosis to superoxide production required an intact p40phox PX domain, which binds to phosphatidylinositol-3-phosphate (PI3P), a phosphoinositide generated by class III PI3 kinases in phagosome membranes (Suh et al J Exp Med 203, 1915Suh et al J Exp Med 203, 2006). Furthermore, a newly developed p40phox-null mouse exhibits reduced neutrophil NADPH oxidase activity in response to selected agonists, including IgG-opsonized targets (Ellson et al J Exp Med 203, 1927Ellson et al J Exp Med 203, 2006). In the current study, we investigated whether p40phox is required for translocation of p67phox during phagocytosis. We generated COSphoxFcγR cells expressing YFP-tagged p67phox from a stable transgene instead of untagged p67phox. Following incubation with IgG-opsonized sheep red blood cells (IgG-RBC), p67phox was detected on phagosome membranes at both early stages of phagosome cup formation and after closure, independent of whether or not p40phox was also co-expressed. However, NADPH oxidase activity was not detected in IgG-RBC phagosomes in COSphoxFcγR-p67phox-YFP cells unless p40phox was present. PMA-activated superoxide production was independent of p40phox, and Western blotting indicated there was no significant difference in expression of the other oxidase subunits in COSphoxFcγR-p67phox-YFP cells without or with the p40phox transgene. Further studies in PLB-985 granulocytes expressing stable transgenes for either YFP-tagged p67phox or p40phox showed that the PI3K inhibitor wortmannin inhibited phagosome NADPH oxidase activity and translocation of p40phox, but localization of p67phox to phagosomes was unaffected. These results indicate that although p40phox positively regulates NADPH oxidase activation during phagocytosis, recruitment of p67phox to the phagosome is independent of p40phox. Taken together, these data suggest that the PX domain of p40phox acts as a PI3P-dependent switch to activate the membrane-assembled NADPH oxidase complex.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».