The function of WDR81 (WD repeat domain 81, ENSG00000167716) is as follows. Functions as a negative regulator of the PI3 kinase/PI3K activity associated with endosomal membranes via BECN1, a core subunit of the PI3K complex. By modifying the phosphatidylinositol 3- phosphate/PtdInsP3 content of endosomal membranes may regulate endosome fusion, recycling, sorting and early to late endosome transport (PubMed:26783301). It is for instance, required for the delivery of cargos like BST2/tetherin from early to late endosome and thereby participates indirectly to their degradation by the lysosome (PubMed:27126989). May also play a role in aggrephagy, the macroautophagic degradation of ubiquitinated protein aggregates. In this process, may regulate the interaction of SQSTM1 with ubiquitinated proteins and also recruit MAP1LC3C (PubMed:28404643). May also be involved in maintenance of normal mitochondrial structure and organization (By similarity). {ECO:0000250|UniProtKB:Q5ND34, ECO:0000269|PubMed:26783301, ECO:0000269|PubMed:27126989, ECO:0000269|PubMed:28404643}.