Phosphatidylinositol(3)-phosphate signaling mediated by specific binding to RING FYVE domains

Phosphoinositide 3-kinases (PI(3)K) are important regulators of receptor signaling cascades and intracellular membrane trafficking. To date, no protein domain has been identified that binds specifically to PtdIns(3)P and thereby recruits/activates downstream effecters of PtdIns(3)P signaling. Using an in vivo assay in yeast that detects Vps34 PI(3)K-dependent intracellular localization of a GFP reporter protein, and in vitro lipid-binding assays, we demonstrate that cysteine-rich RING domains of the FYVE finger subfamily bind specifically to PtdIns phosphorylated exclusively at the D-3 position of the inositol ring. GFP-FYVE domain fusion proteins localized predominantly to membranes of endocytic compartments acid required active Vps34 PI(3)K. Our data establish a molecular link between Vps34 PI(3)K and several FYVE domain-containing proteins (Vac1p, Vps27p) required for vacuolar/lysosomal protein trafficking.