May play a role in cellular vesicle trafficking. Has been proposed to function as a sorting protein that targets SELPLG into endosomes, but has no effect on SELPLG internalization from the cell surface, or on SELPLG-mediated cell-cell adhesion. Interacts with SELPLG. Interaction with SELPLG is controversial. The PX domain binds phosphatidylinositol 3-phosphate which is necessary for localization to the endosomes. Belongs to the sorting nexin family.