Functions as a negative regulator of the PI3 kinase/PI3K activity associated with endosomal membranes. By modifying the phosphatidylinositol 3-phosphate/PtdInsP3 content of endosomal membranes may regulate endosome fusion, recycling, sorting and early to late endosome transport. May also play a role in aggrephagy, the macroautophagic degradation of ubiquitinated protein aggregates. May also be involved in maintenance of normal mitochondrial structure and organization. Widely expressed. Highly expressed at 5 and 15 hpf. Expression is higher in brain and eye. The expression drops after 72 hpf. Belongs to the WD repeat WDR81 family.