PI(3,5)P2 is dephosphorylated to PI3P by FIG4 at the early endosome membrane

At the early endosome membrane, the PAS complex, consisting of FYVE finger-containing phosphoinositide kinase (PIKFYVE), yeast VAC14 homologue (VAC14), and polyphosphoinositide phosphatase aka SAC3 (FIG4), binds to the membrane via PIKFYVE's FYVE finger. The FIG4 phosphatase component dephosphorylates phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) to phosphatidylinositol 3-phosphate (PI3P) (Sbrissa et al. 2007, Sbrissa et al. 2008).

在早期内体膜上，由含有FYVE结构域的磷脂酰肌醇激酶（PIKFYVE）、酵母VAC14同源物（VAC14）以及多磷酸磷脂酰肌醇磷酸酶即SAC3（FIG4）组成的PAS复合物，通过PIKFYVE的FYVE结构域与膜结合。其中，FIG4磷酸酶组分将磷脂酰肌醇3,5-二磷酸（PI(3,5)P2）去磷酸化，转化为磷脂酰肌醇3磷酸（PI3P）（Sbrissa等，2007，Sbrissa等，2008）。