Plays a role in protein ubiquitination, sorting and degradation through its association with VCP (By similarity). Involved in ubiquitin-mediated membrane proteins trafficking to late endosomes in an ESCRT-dependent manner, and hence plays a role in synaptic vesicle recycling (PubMed:28413018). May play a role in macroautophagy, regulating for instance the clearance of damaged lysosomes (By similarity). Plays a role in cerebellar Purkinje cell development (PubMed:28413018). Positively regulates cytosolic and calcium-independent phospholipase A2 activities in a tumor necrosis factor alpha (TNF-alpha)- or lipopolysaccharide (LPS)-dependent manner, and hence prostaglandin E2 biosynthesis (PubMed:28007986). Interacts with ubiquitin. Interacts with UBXN6, VCP and YOD1; may form a complex involved in macroautophagy. Recruited to damaged lysosomes decorated with K48-linked ubiquitin chains. Expressed in the brain, with highest levels in hippocampal neurons, cerebellar granular cell layer and Purkinje cells (PubMed:28413018). At stage 11.5 dpc ubiquitously expressed (PubMed:28413018). In smooth muscle and endothelial cells by leukotriene D4, by tumor necrosis factor in endothelial cells and by uric acid crystals in macrophages. The PUL domain is composed of 6 armadillo-like repeats and mediates the interaction with VCP C-terminus. The PFU domain mediates interaction with ubiquitin. Mice die perinatally and exhibit spleen, lung and brain developmental anomalies (PubMed:28413018, PubMed:28007986). Display less matured and differentiated embryonic cortical neurons (PubMed:28007986). Display reduced ubiquitin-dependent membrane protein trafficking from early to late endosomes (PubMed:28413018). Show reduced prostaglandin E2 biosynthesis in embryonic brain, lung and heart, but not in liver at 18 dpc (PubMed:28007986). Belongs to the WD repeat PLAP family. Several frameshifts and contaminating sequence.