Phox homology domain (PX domain) (PX domain)

The Phox homology (PX) domain is a highly conserved structural module of approximately 100–130 amino acids that functions primarily as a phosphoinositide-binding scaffold (UniProt, 2024). It was originally identified in the p40phox and p47phox subunits of the NADPH oxidase complex, where it facilitates membrane recruitment essential for the production of reactive oxygen species during the immune response (Wishart et al., 2001). Beyond the immune system, PX domains are found in over 40 human proteins, including sorting nexins (SNXs) and phosphoinositide 3-kinases, playing critical roles in endosomal trafficking, protein sorting, and intracellular signaling (Seet & Pawson, 2004). Mutations or dysregulation of PX domain-containing proteins are associated with various diseases, such as Chronic Granulomatous Disease, Alzheimer's disease, and several types of cancer (Ellson et al., 2002). Because the PX domain specifically recognizes phosphatidylinositol 3-phosphate (PI(3)P), it has emerged as an attractive target for therapeutic intervention (PubMed, 2023). Small-molecule inhibitors designed to occupy the PI(3)P-binding pocket can disrupt the membrane localization of key signaling proteins, offering a potential strategy for treating inflammatory disorders and inhibiting tumor metastasis (Nature, 2022). Although no drugs targeting this domain are currently FDA-approved, research into selective PX domain antagonists continues to expand the druggable landscape of the phosphoinositide signaling pathway (PubMed, 2023).

Other names

PX domainPhox-homology domainPhosphoinositide-binding domain

Competitive inhibition of phosphatidylinositol 3-phosphate (PI(3)P) binding to the PX domain, preventing membrane recruitment of effector proteins (PubMed, 2023).