May be involved in several stages of intracellular trafficking. Acts as a GAP for Galphas (By similarity). May play a role in endosome homeostasis. The PX domain mediates interaction with membranes enriched in phosphatidylinositol 3-phosphate. Embryonic lethal. After 8.5 dpc, embryos are smaller, show failure of neural tube closure and abnormal cephalic vascularization. None survive after 14.5 dpc. Visceral yolk sac endoderm cells contain large autophagic vacuoles. Belongs to the sorting nexin family.